The development of advanced materials and technologies to efficiently convert and store energy directly into electricity is of urgent importance due to increasing energy demands of an ever growing world population and decreasing energy reserves. However tremendous scientific challenges remain before successful implementation of any number of competing energy technologies such as solar cells, fuel cells, and batteries. The materials, interfaces and device architectures currently being explored are very challenging to interrogate by ensemble-averaging, bulk experimental methods since they do not exhibit long-range order or homogeneity, contain unique nano-morphological features and possess non-uniform chemical compositions and defect chemistry. This presentation will summarize a few materials design strategies for optimizing the performance of redox-active materials for use in electrochemical energy storage applications and highlight the development of high resolution experimental and theoretical tools for studying charge transfer processes at electrode interfaces. Information obtained from these studies provides fundamental understanding of electron and ion transfer processes and degradation mechanisms for materials utilized for electrochemical energy storage.

Structures, Devices, and Architectures for Nanoscale Solutions in Electrical Energy Storage
G.W. Rubloff
Nano science and technology promise enhancement to batteries and capacitors through higher power at given energy, accompanied by new possibilities for better capacity retention and safety. Among the challenges to realize this promise are (1) the design of higher performance electrode and electrolyte materials and (2) the rational design of structures in which these materials are arranged. We have focused on the latter, seeking to understand how the structure of components and the architecture in which they are arranged determine the multifunctionality required for electrical energy storage: ion transport and storage, electron transport, and structural stability during charge/discharge cycling.
Precision multistep synthesis has enabled the creation of heterogeneous nanostructures, involving multiple materials to confer the needed multifunctionality and to understand how design influences electrochemical behavior at the nanoscale and storage performance of nanostructures. This is illustrated by several such structures which address fundamental phenomena important at the nanoscale and the mesoscale, including: (1) Si nanowire and nanotube structures with integrated electron transport components that achieve robust Li cycling despite large volume changes; (2) nanopore battery configurations to assess fundamental limits on ion transport in highly confined environments; (3) solid state electrolyte and battery configurations for scaling safe materials to the nanoscale; and (4) 3D nanostructure forests, both regular and pseudo-random, to analyze mesoscale architectures and new scientific challenges emerging at the mesoscale. These experimental advances have been accompanied by significant modeling and simulation insights, from DFT to continuum levels, and at the same time they pose formidable, important challenges for theory, particularly at the mesoscale.
This work has been supported by Nanostructures for Electrical Energy Storage (NEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Award Number DESC0001160.

The primary goal of the FIRST Center is to develop fundamental understanding and validated, predictive models of the unique nanoscale environment at fluid-solid interfaces that enable transformative advances in electrical energy storage and catalysis for energy. A signficant portion of our research has focussed on capacitive energy storage by ion attraction to charged interfaces, often termed electrical double layer capacitance. This type of electrical energy storage, which does not involve phase changes, redox reactions or ion intercalation into crystal lattices, frequently results in very long cycle lives and very hgh power densities, but lower energy densities than can be achieved by converting electrical to chemical energy in a battery. We have extensively explored the role of pore size versus ion size, nanoscale surface curvature and pore geometries in maximizing both power and energy density of capacitive and pseudocapacitive electrical energy storage, particularly involving room temperature ionic liquid electroltyes and nanotextured carbon electrode materials.

Energy storage represents an opportunity and a challenge for basic research to cross the technological boundaries in bringing energy independence to the U.S. Since its inception in 2009, the overriding mission of the Center for Electrical Energy Storage (CEES) has been to advance the fundamental understanding of electrochemical phenomena and the design of new materials architectures, using lithium-ion battery chemistries as a guide, for the discovery of a new generation of electrical energy storage systems.
This presentation will discuss the journey of CEES over the past 5 years. Highlights will include 1) approaches to design new anode and cathode materials and architectures, 2) the development of characterization techniques to monitor electrochemical processes at the electrode/electrolyte interface, 3) the use of autonomous chemistries to enable self-repair and shutdown reactions, and 4) theoretical approaches to complement experimental observations and discoveries.
Acknowledgments
This work was supported by the Center for Electrical Energy Storage, an Energy Frontier Research Center funded by the Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy.

This presentation will deal with the development of operando methods for the study and characterization of battery materials. The presentation will begin with a brief overview of the methods employed. Particular emphasis will be placed on the use of X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS), differential electrochemical mass spectrometry (DEMS) and transmission electron microscopy (TEM) under active potential control. The utility of these methods will be illustrated by selected examples including conversion reactions of Mn3O4 as anode material for lithium ion batteries (LIBs), spectroscopic studies of Li/S batteries and the use of DEMS to characterize electrolyte systems for LIBs. The use of operando TEM will be illustrated by studies of lithiation/de-lithiation dynamics of LiFePO4 via energy-filtered TEM. The presentation will conclude with an assessment of future directions.

The Northeastern Center for Chemical Energy Storage (NECCES) has leaded a synergistic effort in the past five years on basic research in the design of the next generation of lithium-ion batteries. The Center has enabled both the development of new chemistries and the fundamental understanding of the physical and chemical processes that occur in intercalation materials such as LiFePO4 and conversion materials such as FeF3/FeF2. The NECCES team has identified the key atomic-scale processes that govern electrode function in rechargeable batteries, over a wide range of time and length scales, via the development and use of novel characterization and theoretical tools, including in situ X-ray scattering, in situ TEM observation, in situ NMR spectroscopy and new computation/simulation tools. The information and knowledge gained are critical to identify and design new battery systems with improved electrochemical properties.

The Joint Center for Energy Storage Research combines discovery science, battery design, research prototyping and manufacturing collaboration in a single highly interactive organization to pursue transformational next generation energy storage beyond lithium ion batteries. JCESR will leave three legacies:
- a library of fundamental knowledge of the materials and phenomena of energy storage at the atomic and molecular level
-two prototypes, one for the grid and one for transportation, that, when scaled to manufacturing will be able to deliver five times the energy density at one-fifth the cost
-a new paradigm for battery R&D that accelerates the pace of discovery and innovation and significantly shortens the time from discovery to commercialization.
An introduction to JCESR&’s vision, mission and legacies will be followed by research highlights illustrating its advances in fundamental science and the promising pathways to transformational battery designs and prototypes.
This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences
Contact information
George Crabtree
Director, Joint Center for Energy Storage Research (JCESR)
Argonne National Laboratory
9700 S. Cass Ave
Argonne, IL 60439
630 252 5509
[email protected]
Departments of Physics, Electrical and Mechanical Engineering
University of Illinois at Chicago
845 W. Taylor St. M/C 273
Chicago, IL 60607
Tel 630 252 5509
[email protected]
Executive Assistant
Bernadette (Nada) Petrovic
Joint Center for Energy Storage Research (JCESR)
Argonne National Laboratory
9700 S. Cass Ave
Argonne, IL 60439
(630) 252-1420
[email protected]

Wildcat Discovery Technologies uses a proprietary high throughput synthesis and screening platform for battery materials. Wildcat&’s system produces materials in bulk form, enabling evaluation of its properties in a standard cell configuration. This allows simultaneous optimization of all aspects of the cell, including the active materials, binders, separator, electrolyte and additives.
Over the past 3 years, we have screened over 250,000 cells, developing new cathodes, anodes, and electrolytes for a variety of battery types (primary, secondary, aqueous, non-aqueous). In this talk, I will discuss what we&’ve learned from this work. Specifically, new analysis methods to extract more information from each cell, which performance metrics are most predictive of long term cycle life and other failure modes, and sensitivity of performance metrics to changes in cell components. I will also discuss new high throughput cell evaluation methods in use at Wildcat, including high precision coulometry and in-situ gas evolution measurement

Lithium hydroxysulfates with general formula LiMSO4OH (M = Co, Fe, Mn) have been advanced as a sustainable option to overcome the deleterious effects of the F-based cathode materials. These hydroxysulfates crystallize either in tavorite or in layered structure depending on the synthetic approach used to obtain these phases. The electrochemical behavior did not show any obvious correlation to structural characteristics such as bond iconicity or bond length. We determined the relative thermodynamic stabilities of LiMSO4OH (M = Co, Fe, Mn) using isothermal acid solution calorimetry to understand the observed differences in their synthesis, structure and electrochemical properties. Both redox potential and thermodynamic stability in layered LiMSO4OH (M = Co, Fe, Mn) decrease with decrease in sulfate binding symmetry as one moves from Co to Mn and LiMnSO4OH becomes electrochemically inactive. LiFeSO4OH shows anomalous stability among isostructural layered materials. Tavorite LiFeSO4OH was found to be energetically less stable than layered LiFeSO4OH, possibly due to its lower symmetry corner shared octahedral chain structure. This study demonstrates the correlation between energetic and redox potential trends in LiMSO4OH (M = Fe, Co, Mn) materials with their ionic radius, overall structure symmetry as well as sulfate binding symmetry.

Since 1997 and the inductive eect of Goodenough, there has been no signicant theoretical
breakthrough in the strategies for guiding experimentalists in their search for high-potential cathodes
in Li-ion batteries. However, experimental evidences exist that prove it is possible to increase the
voltage of cathodes beyond the inductive eect. In this letter we ll the gap between Goodenough
predictions and experimental facts in deriving a simple theoretical formulation of the battery voltage
which accounts not only for the short-range inductive eect of the ligands but also for the long-
range screening eect of the Li+ ions. We further propose to evaluate those contributions in terms of
Madelung eld calculations, using concepts of formal charge that are very familiar to chemists. This
approach is then validated on a wide series of Fe-based cathode materials including the newly and
contentious LiFeSO4F tavorite and triplite phases and having dierent crystal structures, dierent
stoichiometries and dierent ligands. Compared to the voltage predictions usally carried out through
time-consuming rst-principles (DFT) calculations, our approach yields equivalent results within
a few secondes. We believe this chemically intuitive approach will entail new experimental and
computational strategies to revisit the very challenging project of Material Design in the eld of
Li-ion and Na-ion batteries.

Layered titanates represent a class of materials whose physical, ion exchange, and electrochemical intercalation properties are of great technological interest. Several layered titanates have recently been shown to undergo reversible reductive intercalation of both lithium and sodium ions. Some of these electrode materials, which have theoretical capacities in excess of 200 mAh/g, insert alkali metal cations at unusually low potentials (below 0.5V). These characteristics have important implications for the design of high-energy dual intercalation batteries, particularly when the intercalant is sodium.
For this presentation, we report on the preparation, crystal structure, ion exchange and electrochemical properties of a lepidocrocite-type layered titanate and materials derived from it as examples of how new intercalation hosts can be synthesized through the use of chimie douce techniques.

H2V3O8 is a promising cathode material for Li-ion batteries, allowing intercalation of up to four lithium equivalents, ca. 400 Ah kg-1, between 4.2 V and 1.5 V vs. Li/Li+ with a mean potential close to 2.7 V, leading to a specific energy density above 1 kWh kg-1. However, poor stability under cycling still hinders its dissemination, especially when LiPF6 based electrolytes are used. Recently, Wu et al. [1] revealed that traces of water present in the battery electro active core can lead to HF formation, reacting with V2O5 cathodes through a self-catalyzed process, both at open circuit and under potential. The formation of vanadium oxyfluorides could be responsible for the severe capacity fade under charge/discharge cycles.
Aiming to hinder side reactions between H2V3O8 surface and the electrolyte, a process was developed to deposit aluminum oxyhydroxide on the surface of lithiated H2V3O8 at low temperature. The deposition was performed by a one pot multistep reaction starting with phase pure H2V3O8, following by a chemical lithiation, in which the concentration of vanadium (IV) in the structure increases with the lithiation extent, and subsequent surface coating with an aluminum oxyhydroxide. Electro active materials with nominal aluminum concentrations ranging from 0.5 wt.% to 3 wt.% were prepared and characterized by several techniques (TEM, SEM/EDX, He-ion microscopy, XRD, XPS, TGA-DSC and electrochemically).
Physicochemical analysis revealed that the crystal structure of LixH2-xV3O8 was unaffected by the presence of AlOx(OH)y and the later one most likely has an amorphous structure. A homogeneous surface coverage with 3 to 10 µm thickness was measured by TEM on the 3 wt.% Al sample, while for low Al contents no clear coverage could be detected by imaging. EDX and XPS results confirmed the presence of aluminum in all samples. Electrochemical characterization in half cells assembled with 1.5 wt.% Al coated sample showed higher stability for Li-ion intercalation after 200 cycles compared to bare LixH2-xV3O8. For instance, after 200 charge and discharge cycles between 4.05 and 2.2 V vs. Li/Li+ at a rate of 100 A kg-1, LixH2-xV3O8 coated with a nominal Al concentration of 1.5 wt.% shows a capacity retention of 89% compared to 67% of the uncoated LixH2-xV3O8, allowing for a specific energy higher that 0.5 Wh kg-1 for more than 200 cycles.
[1] - J. Wu, N. Membreno, W.-Y. Yu, J. D. Wiggins-Camacho, D. W. Flaherty, C. B. Mullins and K. J. Stevenson, J. Phys. Chem. C 2012, 116, 21208

In the search for new Li-ion battery electrodes that provide the best compromise between capacity, power, charge rates, and long-term stability, increasingly complex composite materials and reaction mechanisms have emerged. Amongst high capacity conversion electrodes based on highly abundant iron, mixed anion oxyfluoride systems combine favorable performance characteristics of the simple oxides (e.g., Fe2O3, Fe3O4, FeO) and fluorides (e.g., FeF3, FeF2). Electrochemical reaction of the oxyfluoride with lithium (FeOF + 3Li → Fe + Li2O + LiF) couples the higher output voltages and reaction potentials of the fluorides and the improved reaction kinetics, capacity and cyclability of the oxides to provide promising electrochemical performance. Identifying the fundamental basis for these performance advantages requires a comprehensive understanding of the electrochemical reaction mechanism and, accordingly, detailed knowledge of how the atomic structure transforms, how the electrode particles evolve, and how the chemical composition of different components change.
We have designed and optimized an in-situ cell that allows data suitable for quantitative Pair Distribution Function (PDF) and small angle scattering (SAXS) analyses to be collected during electrochemical cycling. An in-depth analysis of the operando X-ray PDF data provides comprehensive insights into the evolution in atomic structure and O/F chemistry. Analysis of the SAXS data reveals how the electrode nano-structure evolves.

CFx cathodes offer both high gravimetric energy density and low self-discharge characteristics, making them a preferred option for portable energy applications. However, CFx materials suffer from poor rate and power performance, sub-optimal low temperature performance and are associated with a high cost due to the fluorination of carbon. Leveraging a proprietary high-throughput battery materials discovery workflow, Wildcat Discovery Technologies has developed a new technology to improve cathode materials. The CM2 technology, based on the fabrication of a molecular coating on the surface of the cathode active material, improves CFx cathode rate capability (90% at 1C) and operating voltage (+100mV), while extending the useable power performance into later DoDs (90%), effectively extending the practical lifetime of the battery. Additionally, CM2 eliminates voltage delay at both room temperature and -10oC.
By tailoring the chemistry, CM2 has been demonstrated as a broadly applicable technology on multiple cathode chemistries to improve performance. Another specific example is CuF2 cathodes, which are an attractive primary battery cathode due to their higher volumetric energy density and substantially lower cost. CuF2 cathodes treated with CM2 have higher rate capability (>90% at 1C), significantly improved self-discharge behavior (<90% retention after 10 weeks), and higher voltage stability than state-of-the-art CuF2. A 2032 coin cell was fabricated with 300Ah/L (cell level), an energy density improvement of >30% over a commercial MnO2 cell.

To further improve the energy/power density of Li- or Na-based batteries, structure modification of oxide/fluoride/polyanion materials with moderate expansion of ion channels has been demonstrated to be a successful strategy.[1-4] However, one should pay attention to the fact that the synthesis of more expanded structures usually comes at the cost of a decrease in ion channel dimensionality, mostly leading to the formation of 1D or 2D channel structures that have a greater potential to become blocked or degraded. Also, in the case of interconnected open 3D channels, structure expansion upon storage is still a great challenge.Fluorides are expected to exhibit larger capacities than most of the oxides without tradeoffs in terms of working voltage as long as their poor conductivity can be compensated. In the past decades, such studies mainly focused on commercially available ReO3-type FeF3 electroactivated by high-energy ball milling of FeF3/C composites to generate C-FeF3 nanodomains as insertion or conversion cathodes for Li batteries. Recently, our group prepared an open-structure fluoride for Li battery applications.[2,5] As reported for the hexagonal tungstenminus;bronze (HTB)-type compound FeF3 0.33H2O characterized by open 1D channels, the Li insertion mechanism was intrinsically modified, and the miscibility gap present in ReO3-type FeF3 was completely removed in the HTB phase, favoring complete solid-solution behavior in the 3 V region. An improved intrinsic conductivity enabled the fluoride to act as a highly electroactive Li battery cathode without in situ addition of conductive species. However, the presence of single ion channels, which are prone to partial blockage by H2O molecule fillers, still limits the extension of fluoride materials into Na batteries. Most recently, we report a novel open-framework fluoride pyrochlore phase, FeF3 0.5H2O, that is structurally similar to the known AlF3 0.5H2O and characterized by a much larger cell volume (sim;1130 Å3). [6] Notably, it exhibits a higher pore density due to interconnected 3D ion channels without a serious tradeoff concerning channel size compared with HTB-type fluoride, suggesting a more favorable cation insertion capacity. The storage performance should also benefit from the more tightly confined H2O molecules in the zigzag channels of the pyrochlore phase as opposed to the straight channels of the HTB phase.
[1] Li C L, Gu L, Tsukimoto S, van Aken P A, Maier J. Adv. Mater., 2010, 22, 3650.
[2] Li C L, Gu L, Tong J W, Tsukimoto S, Maier J. Adv. Funct. Mater., 2011, 21, 1391.
[3] Li C L, Gu L, Tong J W, Maier J. ACS Nano, 2011, 5, 2930.
[4] Li C L, Mu X K, van Aken P A, Maier J. Adv. Energy Mater., 2013, 3, 113.
[5] Li C L, Yin C L, Mu X K, Maier J. Chem. Mater., 2013, 25, 962.
[6] Li C L, Yin C L, Gu L, Dinnebier R E, Mu X K, van Aken P A, Maier J. J. Am. Chem. Soc., 2013, 135, 11425.

Porous aromatic frameworks (PAFs) are a class of carbon-based ultraporous materials with large internal surface areas (in excess of 5000 m²/g). The exceptionally large porosity of PAFs can potentially provide numerous open binding sites for charge carrying ions and allow for their faster transport. While PAFs are being thoroughly investigated for gas adsorption and separation applications, their performance as host electrode materials for rechargeable batteries is largely unknown. In this work, we examine the viability of PAFs as electrode materials for Li-ion batteries using ab initio density functional theory methods. We show that Li intercalated PAFs can demonstrate a large electrochemical capacity for Li (as large as 750 mAh/g) and a low voltage (0.2-0.5 V). These electrochemical properties, coupled with small structural distortions during intercalation, indicate that this class of porous materials can be a promising candidate as negative electrode (anode) materials for Li-ion batteries. We also show that the ultraporous nature of PAFs can also allow for the intercalation of larger ions (for example, Na ions), further extending their potential for next-generation non-Li rechargeable batteries.

By stacking multiple positive and negative electrode pairs described as bipolar electrodes within a single cell, design of more powerful and useful stacked Li-ion batteries is possible. While Al and Cu are typically used as current collectors for positive and negative electrodes, respectively, the bipolar electrodes for the proposed battery use a single Al foil coated with both positive and negative electrode materials. However, owing to the Li-Al alloy reaction (lower potential of 0.4 V vs. Li/Li⁺), reversible Li intercalation materials which operate from 0.5 to 1.0 V are essential for the negative electrode. In the presentation, we show the intercalation-metal-organic framework (iMOF), 2,6-naphthalene dicarboxylate dilithium (Naph(COOLi)₂) as the target negative electrode material. This material has a crystalline organic-inorganic layered structure composed of π-stacked naphthalene packing and tetrahedral LiO₄ units. The 2,6-Naph(COOLi)₂ electrode shows a reversible two-electron-transfer reaction (230 mAh g^-1 per active material) at a flat potential plateau of 0.8 V with narrow polarization of 70 mV. This material exhibits an intercalation reaction of Li into the tetrahedral LiO₄ layer by redox systems of the π-stacked naphthalene packing layer. Its volumetric change was ca. 10 % while the framework remains constant during charging and discharging. Intercalated Li⁺ is stabilized as a tetrahedral LiO₃C structure composed of three O atoms of different dicarboxylate units and naphthalene C atom covalently-bonded carboxylate groups indicating Li⁺ transport channel. The organic-inorganic interlayer distance remains constant while π-stacking interaction for naphthalene packing slightly increases, which contributes to electron-transfer channel. Such molecular self-assembly having two-dimensional electron and ion conduction paths provides the observed electrochemical reversibility. As a preliminary step for the high-voltage stacked Li-ion batteries, a 4-V Li-ion cell was fabricated with 2,6-Naph(COOLi)₂ negative and high potential-operating LiNi_0.5Mn_1.5O₄ spinel positive electrodes in the available potential range of the Al current collector.

Stable organic radicals moieties have been polymerized and successfully fabricated into cathodes for organic radical batteries (ORB&’s). The morphologies of these polymers have a crucial impact on the performance of the battery. The density of radical moieties is directly related to the battery&’s energy density. In addition, how the polymer chains pack in films can affect both electron transport between radicals and ion transport through the film. In order to guide the development of new organic radical electrode materials and to aid in the design of improved electrode structures, a detailed understanding of the polymer morphologies is needed.
Accordingly the polymeric organic nitroxide radical material poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate) (PTMA), was studied using quantum (QM) chemical calculations and classical molecular dynamics simulations (MD) comprising hundreds of thousands of atoms. Radical-containing units and pairs of units were extracted from the films generated in the classical MD simulations and QM calculations were performed to determine factors influencing the electrical conductivity including the reorganization energy and the many-electron electron-transfer matrix element. Furthermore, gas phase QM calculations of ionic bound pairs and morphological features including the radial distribution function where used to evaluate the ion migration within the film. Results were compared to relevant experimental measurements.

Li-S and Li-O₂ batteries represent promising new technologies that could meet the needs for high energy density storage, but they require thoughtfully designed nanomaterials for the cathode, different electrolyte strategies than those used for Li-ion batteries, and a better understanding of the factors that limit the cell performance via operando and ex-situ studies of cell chemistry. These topics will be the subject of the presentation. The similarities and differences in the two systems will be compared and contrasted based on our knowledge of the electrochemistry and materials science, and critical developments will be discussed that could enable their commercial viability. This presentation will address the many aspects of our fundamental investigations involving XAS and NMR probes of sulfur redox chemistry and sulfur speciation in the Li-S cell; electrolyte-cathode interactions involving new electrolyte systems; and the mechanisms underlying product deposition and dissolution at the cathode interface in both Li-S and Li-O₂ cells.

As a result of the high theoretical specific energy, the rechargeable aprotic Li-O2 battery is under intense investigation worldwide.[1-13] Early research in this field determined that it was essential to understand the fundamental chemistry and electrochemistry that underpins operation of the Li-O2 battery if there was to be any hope of making progress with the technology.[1-10]
The presentation will concentrate on the key challenge of the positive electrode; it will consider the processes that occur on O2 reduction (discharge) and oxidation (charge) and include consideration of the stability of electrolytes and electrodes towards the reactive species involved. The use of alternative cathode materials to carbon will be discussed,[13] as will redox mediating molecules to address the major problem of how to oxidise solid Li2O2 at a solid electrode with sufficient rate to sustain adequate current densities.
(1) Abraham, K. M.; Jiang, Z. J. Electrochem. Soc. 1996, 143, 1.
(2) Ogasawara, T.; Debart, A.; Holzapfel, M.; Novak, P.; Bruce, P. G. J. Am. Chem. Soc. 2006, 128, 1390.
(3) Girishkumar, G.; McCloskey, B.; Luntz, A. C.; Swanson, S.; Wilcke, W. J Phys Chem Lett 2010, 1, 2193
(4) Lu, Y. C.; Gasteiger, H. A.; Parent, M. C.; Chiloyan, V.; Shao-Horn, Y. Electrochem. Solid State Lett. 2010, 13, A69.
(5) Zhang, Z.; Lu, J.; Assary, R. S.; Du, P.; Wang, H.-H.; Sun, Y.-K.; Qin, Y.; Lau, K. C.; Greeley, J.; Redfern, P. C.; Iddir, H.; Curtiss, L. A.; Amine, K. J. Phys. Chem. C 2011, 115, 25535.
(6) Bryantsev, V. S.; Giordani, V.; Walker, W.; Blanco, M.; Zecevic, S.; Sasaki, K.; Uddin, J.; Addison, D.; Chase, G. V. J. Phys. Chem. A 2011, 115, 12399.
(7) Mo, Y. F.; Ong, S. P.; Ceder, G. Phys. Rev. B 2011, 84, 205446.
(8) Xu, W.; Viswanathan, V. V.; Wang, D.; Towne, S. A.; Xiao, J.; Nie, Z.; Hu, D.; Zhang, J.-G. J. Power Sources 2011, 196, 3894.
(9) Mizuno, F.; Nakanishi, S.; Kotani, Y.; Yokoishi, S.; Iba, H. Electrochem. 2010, 78, 403.
(10) Adams, B. D.; Radtke, C.; Black, R.; Trudeau, M. L.; Zaghib, K.; Nazar, L. F. Energy Environ. Sci. 2013, 6, 1772.
(11) Kim, B. G.; Lee, J.-N.; Lee, D. J.; Park, J.-K.; Choi, J. W. Chemsuschem 2013, 6, 443.
(12) Li, F.; Tang, D.-M.; Chen, Y.; Golberg, D.; Kitaura, H.; Zhang, T.; Yamada, A.; Zhou, H. Nano Letters 2013.
(13) Ottakam Thotiyl, M. M.; Freunberger, S. A.; Peng, Z.; Chen, Y.; Liu, Z.; Bruce, P. G. Nat Mater 2013, 12, 1050.

The mechanisms and efficiency of charge transport in lithium peroxide (Li2O2) are key factors in understanding the performance of non-aqueous Li-air batteries. Towards revealing these mechanisms, here we use first-principles calculations to predict the concentrations, mobilities, and conductivities of various charge carriers and intrinsic defects in Li2O2. We compare transport rates within the baseline case of (pristine) bulk Li2O2, at selected low-energy surfaces, and within amorphous phases. While transport within the bulk is predicted to be low, higher concentrations of charge carriers at both surfaces and within amorphous regions are shown to enhance conductivity in the vicinity of these features. Our calculations reveal that changes in the charge state of O2 dimers controls the defect chemistry and conductivity of Li2O2. More generally, we describe how the presence of a species that can change charge state - e.g., O2 dimers in alkaline metal-based peroxides - may impact rechargeability in metal-air batteries.

Although the operation principle of Li-S batteries has been known for decades, they have not been commercialized on a large scale up to date. The major problems connected with a fast capacity fading (stability) and low cycling efficiency are mainly due to a complicated reaction mechanism which involves different soluble lithium polysulfides. In an attempt to confine polysulfides in the vicinity of their formation, different designed porous host matrixes have been used [1]. It has been proposed that a high surface area, porous carbon materials enable confinement of sulfur and polysulfides and have an impact on the Li-S battery cycling properties (capacity and efficiency). However, some literature reports have showed that the use of carbons with a designed morphology is insufficient for long cycling stability. Additional stability can be gained by using doped or modified carbon materials or using a designed separator [2] that can stop polysulfide diffusion to the lithium. In this study, we show our recent results on the role of separator. By different approaches we modified the surface of separator with selected functional groups (materials) that can trap or repulse lithium polysulfides. The use of modified separator has resulted in a significantly improved coloumbic efficiency and in a longer cycle life. The impact of modified separator on the mechanisms proceeding in Li-S batteries was studied using the recently developed in-situ analytical techniques (4-electrode Swagelok cell [3] and UV-Vis spectroscopy in operando mode [4]).
[1] S. Eversand, L.F. Nazar, Acc. Chem. Res. 46 (2013), 1135-1143
[2] A. Manthiram, Y. Fu, Y.-S. Su, Acc. Chem. Res. 46 (2013), 1125-1134
[3] R. Dominko, R. Demir-Cakan, M. Morcrette, J.-M. Tarascon, Electrochem. Comm., 13 (2011) 117-120.
[4] M.U.M. Patel, R. Demir-Cakan, M. Morcrette J.-M. Tarascon, M. Gaberscek, R. Dominko, ChemSusChem, 6 (2013), 1177-1181.
This work has been supported by the EUROLIS project, grant agreement number 314515, funded by the EC Seventh Framework Programme theme FP7-2012-GC-MATERIALS.

The lithium-oxygen battery, of much interest due to its very high energy density, presents many challenges, one of which is a high charge overpotential that results in large inefficiencies. Here we report a cathode architecture based on nanoscale components that results in a dramatic reduction in charge overpotential (to ~0.2 V). The cathode utilizes atomic layer deposition of palladium nanoparticles on a carbon surface with an alumina coating for passivation of carbon defect sites. The low charge potential is enabled by the combination of palladium nanoparticles attached to the carbon cathode surface, a nanocrystalline form of lithium peroxide with grain boundaries, and the alumina coating preventing electrolyte decomposition on carbon. High resolution transmission electron microscopy provides evidence for the nanocrystalline form of lithium peroxide. The new cathode material architecture provides the basis for future development of lithium-oxygen cathode materials that can be used to improve the efficiency and extend cycle life.

Yali Liu, Hao Zheng, Dongdong Xiao, Yingchun Lyu, Jiayue Peng, Rui Wang, Yongsheng Hu,
Lin Gu, Hong Li*, Liquan Chen
Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P.R. China
E-mail: [email protected]
Rechargeable nonaqueous lithium air battery has attracted wide attention due to its very high theoretical energy density. It is still very challenge for operating the batteries in air, partially due to influences of moisture and carbon dioxide. It has been demonstrated that there would be Li2CO3 in the discharge products when the reactive gas contains CO2. It has been thought that Li2CO3 is very difficult to be decomposed during charging. Therefore, most reported lithium air batteries are investigated under high pure oxygen with CO2 less than 5 ppm. In 2011, Takechi et al reported a Li/CO2:O2 (from 0 to 100% volume CO2) battery, which didn&’t show a reversible charge capacity with a cut-off voltage of 4.5 V even in the first cycle. McCloskey et al reported a Li/O2 battery with CO2 as a contamination gas (10% volume). The battery employed LiTFSI-DME as electrolyte and a sloped charging voltage profile up to 4.8 V was reported in the first cycle. A reversible Li/CO2:O2 (1:1, volume ratio) battery with DME based and DMSO based electrolyte was reported by Kang et al recently. They pointed that Li2CO3 was the main discharge product in this battery and can form reversibly. We have also reported that Li2CO3 can be decomposed after mixing with NiO as catalyst. Accordingly, there is no doubt that formed Li2CO3 can be decomposed under suitable conditions. Therefore, it is plausible that a rechargeable Li/CO2 battery could be also developed. According to thermodynamic calculation, the specific energy density of Li/CO2 batteries is almost three fourths of Li/O2 battery. It also can be calculated that the theoretical voltage is about 2.8 V based on the equation: 4Li + 3CO2 → 2Li2CO3 + C. The Li/CO2 battery could be attractive especially when CO2 is enriched in atmosphere. Previously, Archer et al reported a primary Li/CO2 battery which cannot be recharged and only discharge in the high temperature.
In this report, we will show that a Li/CO2:O2 (2:1, volume ratio) battery and a Li/CO2 battery can operate reversibly at room temperature when lithium triflate (LiCF3SO3)-TEGDME is used as the electrolyte, various carbon as air electrodes. The polarization of the reactions, products formed under different conditions with different volume ratio of O2: CO2, and the relationship between the electrochemical performances and the structure, morphology and the composition of the products are analyzed based on electrochemical measurements combining with in situ and ex situ STEM, SEM, AFM, FTIR, Raman, XRD, SIMS techniques and DFT calculations.

Lithium based batteries play a critical role among the best candidates for next generation high energy storage systems. Sulfur is one of the most promising cathode materials, with its theoretical specific capacity of 1675 mAh/g (the highest value for all known solid cathode materials), for the next generation of rechargeable batteries. However, poor rechargeability and fast capacity degradation, owing to the insulating nature of sulfur and the dissolution of various polysulfide intermediates into the electrolyte during the discharge process, are major hurdles inherent in Li/S batteries that hinder their mass commercialization. The development of new battery architectures is essential to overcome these limitations for Li/S batteries to succeed. In this study, nanostructured three-dimensional graphene based materials are investigated as the electrode substrates for Li/S batteries: Vertically aligned carbon nanotubes (VACNT) and reduced graphite oxides (RGOx) are utilized as supporting materials for sulfur in nanocomposite electrodes.
The VACNTs are directly synthesized on a stainless steel substrate by employing an alumina catalyst support layer followed by a chemical vapor deposition process. The VACNT/Sulfur composites are then prepared by melt-infiltration of sulfur into the VACNTs. RGOx/Sulfur composites are prepared through a simple one-step process by intercalating sulfur into the GOx platelets and reducing the GOx by a photothermal reduction process. Both materials can provide a highly interconnected conductive network to both confine and make intimate contact with the insulating sulfur thereby enabling a reversible electrochemical reaction at high current rates. Additionally, they provide good structural stability of the cathode. Moreover, the sulfur loaded VACNT electrodes were further coated with conjugated polymers. This external layer of conducting polymers hinders the out-diffusion of the soluble polysulfides formed during discharge process into the electrolyte by encapsulating and adsorbing polysulfide intermediates in its unique highly torturous pore structure.
The resulting composite films are mechanically robust, show high electrical conductivity and can be used directly as electrodes without the need for binders as in the case for conventional battery electrodes. These composite materials are tested as novel cathodes for Li/S batteries and the results demonstrate the enriched utilization of sulfur and improved cyclability of the battery cells.

Lithium-sulfur (Li-S) batteries are rechargeable secondary batteries with a theoretical gravimetric capacity of 1.67 Ah/g and an energy density of 2.6 kWh/kg based on the lithium-sulfur redox couple. The high gravimetric capacity, natural abundance, and low cost of sulfur make it an attractive material for integration into high-performance lithium batteries. Unfortunately, sulfur alone is not a suitable electrode material, requiring the development of innovative solutions. Cathode materials for rechargeable secondary batteries such as Li-S batteries typically contain carbon as the amorphous conductive material carbon black predominantly synthesized by the incomplete combustion of petroleum byproducts. Sulfur cathodes require the addition of this conductive carbon material to improve their electrical conductivity. In an effort to create an environmentally sustainable synthesis pathway for energy materials necessary in Li-S batteries, the natural biopolymer lignin was used. Lignin is a found as a major constituent of wood and the extraction of lignin from wood pulp by the paper industry results in sulfonated lignin (lignosulfonate). The current work shows that lignosulfonate can be thermally converted and annealed to yield a high-performance cathode material for use in Li-S batteries, with initial results showing reversible capacities in excess of 600 mAh/g, corresponding to an energy density of ~1300 Wh/kg and with Coulombic efficiencies greater than 99%. This work will enable paper mills to convert a low-value byproduct stream of lignosulfonates into a high-value cathode material produced through sustainable methods.

Lithium-sulfur batteries are attractive because of the relative abundance of sulfur and a higher theoretical energy density than lithium-ion batteries[1]. However they suffer from poor cycling performance, primarily due to the dissolving of the polysulfide species in the electrolyte. As a step towards rational design strategies for optimizing battery performance, we study the chemistry of dissolved polysulfide species in a polymeric solvent using first principles DFT simulations and simulate the X-ray absorption spectra using the excited electron and core hole approach.

Lithium-ion batteries are commonly used for microelectronics, transportation, and other applications. There is great interest to improve their energy density for electric vehicle applications. Sulfur, the tenth most abundant element in earth, may provide a high theoretical capacity of 1675mAh/g and energy density of 2,500Wh/kg or 2,800Wh/l, holds great potential towards high-energy devices. However, the use of sulfur as the cathode has been limited by (a) poor electronic conductivity, (b) dissolution of sulfur intermediates, and (c) large volumetric expansion (~80%) upon lithiation. Such limitations result in low Coulombic efficiency and rapid capacity fading. Furthermore, as formed soluble sulfur intermediates in the cathode may diffuse to the anode reacting with the lithium anode, resulting in increased resistance and reduced efficiency. Herein, we report a rational design of carbon/sulfur/polymer composite particles. Porous carbon particles with high pore volume (>4.0 cm3/g) and surface area were prepared using a spry dry method, which were then coated with polymer. The high pore volume enables high loading of sulfur (>80 wt %), while the carbon scaffold offers high conductivity. Such a composite structure renders the electrodes with excellent Coulombic efficiency and capacity, as well as cycling stability.

The operation of Li batteries involves complex chemical and electrochemical reactions, which are crucial to the battery performance. Therefore, it is important to understand the reactions taking place at different stages of the battery operation, as well as the factors that affect the reactions. In particular, the electrolyte decomposition on anode surface, which forms the so-called solid electrolyte interphases (SEIs), and the lithiation/delithiation reaction of high capacity Li-rich cathode material have attracted much attention. Soft x-ray absorption spectroscopy (sXAS) is a powerful tool to probe the chemical species and electronic states with elemental sensitivity. This presentation will discuss examples on using sXAS to study battery materials for both fundamental understanding and practical developments. We will showcase how sXAS fingerprints the battery operation by detecting the evolving electron states. Recent results on SEIs and Li-rich cathode materials will be discussed. Our results offer important information for improving Li batteries.

The integration of inorganic nanocrystals as building units into mesoscale architectures yields materials whose structure is controllable on atomic, nano, and meso length scales, providing a foundation for understanding how system-level functional properties emerge. We create thin film mesoporous architectures [1] in which the pore and crystallite dimensions are tuned to elucidate the impact of these structural parameters on capacity fade during electrochemical cycling. In anatase TiO₂ architectures, both nanocrystallite dimensions and their arrangement into an open structure are found to influence their ability to accommodate the strain of the lithium-insertion driven phase transformation without significant degradation over 1000 cycles. Far greater strain accompanies the phase transformations occurring upon lithiation of tin (Sn), which forms a series of alloys up to a high theoretical capacity of 960 mAh/g in Li₁₇Sn₄. These transformations were found by ex situ TEM to fragment even nanoscale (8 nm diameter) Sn particles, leading to extensive capacity fade with cycling [2]. To address this problem, we encapsulated Sn nanocrystals in a conductive GeS₂ shell, in an effort to accommodate mechanical stresses and assure good electrical conductivity for more stable cycling behavior. GeS₂ plays an important role because it is not only able to insert lithium, but it is also able to form an alloy with Sn. We evaluated the cycling performance of pristine and functionalized Sn nanocrystals in Li-ion half-cell configuration. The Sn nanocrystals encapsulated GeS₂ showed a high discharge capacity with excellent cycling performance compared to those of Sn nanocrystal-based electrodes.
[1] R. Buonsanti, et al. Nano Lett. 12 (2012), 3872.
[2] L. Xu, et al. Nano Lett. 13 (2013), 1800.

TiO2 has been widely used for anode material of lithium ion battery because of its low cost and excellent structural stability during charging-discharging process. However, practical applications of TiO2 materials have been limited due to its low Li ion diffusivity and poor electrical conductivity. Several approaches such as design of 1D nanostructures, surface modification of electrode materials, and the use of hybrid electrode systems have been considered to be promising to overcome these intrinsic drawbacks of TiO2 materials, but some problems are not completely resolved. Further, it is recently reported that the contact property between electrode and current collector critically affects the electrochemical performance of lithium ion battery. Here, we suggest two different approaches to improve contact property between electrode materials and the current collector as well as between electrode materials; sol-gel nanoglues and 3D crosslinked nanoweb architecture. We could achieve excellent rate capability and stable cycle performance up to 100 cycles by applying these methodologies.

Titanium dioxide (TiO2) has received a great attention as an anode for lithium ion batteries (LIB) due to its structural stability during lithium insertion/extraction and high working voltage. However the poor rate capability, resulting from inherently low electric conductivity and high resistance between the current collector and the electrode, limits its practical use. Although one dimensional (1D) TiO2 nanostructures directly grown on the current collector could significantly improve the rate capability, this system has a limitation in the increase of areal capacity due to high electronic resistivity of TiO2. We report on TiO2 nanotubes branched on carbon nanofibers structure as an anode material for LIB. The TiO2 nanotubes branched on carbon nanofibers electrode shows high areal capacity and excellent rate capability. The improvements in areal capacity and rate capability are attributed to the high loading of branched TiO2 nanotubes on the carbon nanofibers and the efficient electron transport to branched TiO2 nanotubes from the current collector through carbon nanofibers.

Well shaped single crystalline Mn3O4 nano-octahedra with exposed highly active {011} facets with different particle sizes have been synthesized and used as anode material for lithium ion batteries. The nano-octahedra samples demonstrated a much better electrochemical performance in comparison with the irregular Mn3O4 nanoparticles. In particular, the smallest sized Mn3O4 nano-octahedra show the best cycling performance with an initial charge capacity of 907 mA h g-1 and a 50th discharge capacity of 500 mA h g-1 at a current density of 50 mA g-1 with an excellent coulombic efficiency (nearly 100%) and a good rate capability with a charge/discharge capacity of 350 mA h g-1 when cycling at 500 mA g-1. HRTEM and HAADF-STEM have been used to characterize our single crystalline Mn3O4 nano-octahedra. The mechanism for these excellent electrochemical properties has been studied in detail from different aspects such as structure, size effect, crystal shape, surface composition, ions diffusion and active facets. This work reveals that the excellent electrochemical performance is related to the exposed highly active {011} facets which can facilitate the conversion reaction of Mn3O4 and Li due to the alternating Mn and O atom layers, resulting in easy formation and decomposition of the amorphous Li2O and the multi-electron reaction. Moreover, the smallest sized Mn3O4 nano-octahedra contain the largest number of {011} facets, thus more active sites, providing maximum contact with the electrolyte, facilitating the rapid Li-ion diffusion at the electrode/electrolyte interface and fast lithium-ion transportation within the particles, leading finally to the best electrochemical properties among the differently sized Mn3O4 nano-octahedra. The high Li-ion storage capacity and excellent cycling performance suggest that the Mn3O4 nano-octahedra with exposed highly active {011} facets could be an excellent anode material for high-performance lithium-ion batteries.

Cu2O has been investigated as a cadidate of the promising anode materials for Lithium ion batteries (LIB) due to its several advantages such as reversible mechanism with Li+, relatively low-cost, non-toxicity, and higher theoretical capacity than graphite. However, the Li+ charge and discharge (C-D) processes accompany huge volume expansion and shrinkage, by which mechanical stresses are induced and lead to poor C-D cycle life due to the failure of the contacts between anode material and current collector. In this study, we present new nanostructures of Cu2O as an anode of LIB. The Cu2O nanostructure were synthesized by electrochemical deposition without any templates and surfactants. The Cu2O nanostructures showed much more excellent electrochemical properties than Cu2O films. During discharge/charge cycles of 500, the electrochemical capacity increased from 370 to more than 1000 mAh/g. The enhancement mechanism will be discussed in the view of phase transformation from Cu2O to CuO, structural transformation of Cu2O fragmentation, and generation of electroactive polymeric gel-like layer.

Lithium-ion batteries (LIBs) have been considered as one of the most promising electric energy storage systems due to the various merits of high voltage, high capacity, low cost and environmental friendliness. However, there are still several challenging issues in LIBs to be overcome in order to fulfil the requirements as high-performance power sources in future market, including higher capacity, lower cost, longer cycle life and better rate performance. Nanostructure engineering has been demonstrated as a powerful and effective strategy in the rational design of new electrode materials with optimized performance through both morphological and compositional solutions. For example, various nanostructures with controlled morphologies including hollow spheres/cubes, nanowires/rods as well as nanoplates could achieve significantly enhanced lithium storage properties due to the size and shape effects. However, the intrinsic properties including low electrical conductivity and poor mechanical stability of most oxide electrode materials, leading to unsatisfactory cycling stability and rate performance, still seriously limit their applications. Recently, an emerging concept of hybrid nanostructures has attracted tremendous attention since better performance could be expected in such architectures.Coaxial nanocables, as one of the most interesting hybrid nanostructures, hold the great potential for simultaneously resolving the problems of poor electrical conductivity and weak mechanical stability with rational design and careful choice of core and shell components. However, there are not too many such reports showing the attractive properties of nanocable structures for lithium storage, probably due to the lack of appropriate synthesis methods.
In this work, we have successfully synthesized CNF@MnO and CNF@CoMn2O4 coaxial nanocables with considerably enhanced lithium storage performance through a facile two-step strategy. The method involves the polyol process for the synthesis of metal-glycolate layer on the surface of the CNFs and the subsequent thermal ennealing treatment undr N2 protection. These two nanocable electrodes exhibit remarkable lithium storage properties in terms of high specific capacity, long cycle life and superior rate performance. For example, at a current density of 1000 mA/g, the CNF@CoMn2O4 nanocable electrode can deliver a high capacity of about 655 mAh/g and can last for at least 300 cycles, which is remarkable. The enhanced electrochemical performance could be attributed to several advantages of the smart coaxial nanocable configuration, which can effectively alleviate the volume change, prohibit the nanoparticle aggregation and facilitate the electron transport. Such high-performance nanosctructures with large-scale production might hold great potential for the fabrication of high energy and power density lithium-ion batteries.

Ge nanowires (NWs) are a promising anode material for next generation lithium-ion batteries due to their high maximum theoretical capacity (1385 mAh/g) when compared with conventional graphitic based materials (372 mAh/g).[1] NWs also provide good electrical conductivity along their length, have a high interfacial area in contact with the electrolyte, have an optimal short diffusion distance for Li-ion transport and can be grown directly from current collectors, eliminating the need for binders and conductive additives. Here we demonstrate stable cycling over 1100 cycles of Ge NWs grown directly from a current collector. We show by ex-situ high-resolution transmission electron microscopy (HRTEM) and high-resolution scanning electron microscopy (HRSEM) studies that the NW array transforms into a robust porous network structure within the first 100 cycles. Once this network is formed it is highly stable, maintaining a capacity of 900 mAh/g over the following 1000 cycles. The electrode material described here has several advantages as it is formed in a low energy, wet-chemical process with Ge NWs nucleating and growing from an evaporated Sn layer on stainless steel.[2, 3] Sn also has a high maximum theoretical capacity (994 mAh/g), and we show both physically (TEM) and electrochemically (differential capacity) that the Sn seeds at the ends of the NWs reversibly alloy with lithium and contribute to the electrodes overall specific capacity. The NW electrode architecture also performed exceptionally well in rate capability tests, achieving a discharge capacity of 435 mAh/g after 80 cycles at a discharge rate of 100C.
1. Mullane, E.; Kennedy, T.; Geaney, H.; Dickinson, C.; Ryan, K. M., Chemistry of Materials 25 (9), 1816-1822.
2. Geaney, H.; Dickinson, C.; Barrett, C. A.; Ryan, K. M., Chemistry of Materials 2011, 23 (21), 4838-4843.
3. Geaney, H.; Gunning, R. D.; Laffir, F. R.; Ryan, K. M., Chemical Communications 2011, 47 (13), 3843-3845.

Ge nanowires (NWs) have recently been highlighted as active materials within Li battery anodes.^1,2 Ge NWs (along with Si NWs³) are well placed as anode materials for Li ion storage due to their high theoretical capacity of 1384 mAhrg^-1. To maximize the capacity of NW based Li-ion anodes, they should be grown in high density directly on the metal current collector to allow for efficient current transport. Ancillary materials such as inactive catalyst seeds, binders and conductive additives should also be minimized as they diminish capacity by adding mass to the final device. Herein we present the development of a rapid pyrolysis route allowing the formation of high density Ge NW mats grown directly on stainless steel current collector substrates. Three distinct approaches which exploit the formation of discrete catalyst seeds were examined with the final process optimized for centimetre scale NW coverage on device integrable substrates. Electrochemical testing of the NW covered substrates yielded capacity measurements greater than 1000 mAhrg^-1 after 1000 cycles at high charge and discharge rates. The method represents a rapid scalable approach for the formation of highly promising Li-ion anode materials.
1. Candace K. Chan, Xiaou Feng Zhang, Yi Cui, Nano Letters2007, 8, 307-309
2. Fang-Wei Yuan, Hong-Jie Yang, Hsing-Yu Tuan, ACS Nano2012, 6 (11), 9932-9942
3. Candace K. Chan, Peng Hailin, Gao Liu, Kevin McIlwrath, Xiao Feng Zhang, Robert A. Huggins, Yi Cui, Nature Nanotechnology2008, 3 (1), 31-35

Recently, silicon-based lithium-ion battery anodes have shown encouraging results, as they can offer high capacities and long cyclic lifetimes. The applications of this technology are largely impeded by the complicated and expensive approaches in producing Si with desired nanostructures. We report a cost-efficient method to produce nanoporous Si particles from metallurgical Si through ball-milling and inexpensive stain-etching. The porosity of porous Si is derived from particle&’s three-dimensional reconstructions by scanning transmission electron microscopy (STEM) tomography, which shows the particles&’ highly porous structure when etched under proper conditions. Nanoporous Si anodes with reversible capacity of 2900 mAh/g was attained at a charging rate of 400 mA/g, and stable capacity above 1100 mAh/g was retained for extended 600 cycles tested at 2000 mA/g. The synthetic route is low-cost and scalable for mass production, promising Si as a potential anode material for the next-generation lithium-ion batteries with enhanced capacity and energy density.

The recovery of useful materials from earth-abundant substances is of strategic importance for industrial processes. Silicon, especially with nanostructure, has shown promise as the next generation anode for Li-ion batteries. Despite the fact that Si is the second most abundant element in the Earth's crust, processes to form Si nanomaterials is usually complex, costly and energy-intensive. Here we show that pure Si nanoparticles (SiNPs) can be derived directly from rice husks (RHs), an abundant agricultural byproduct produced at a rate of 1.2 × 10⁸ tons/year, with a conversion yield as high as 5% by mass. And owing to their small size (10~40 nm) and porous nature, these recovered SiNPs exhibits high performance as Li-ion battery anodes, with high reversible capacity (2790 mAh/g, seven times greater than graphite anodes) and long cycle life (86% capacity retention over 300 cycles). Using RHs as the raw material source, overall energy-efficient, green, and large scale synthesis of low-cost nano-Si anodes is possible.

All-solid inorganic Li ion batteries fabricated by physical vapor deposition as thin film stacks on a substrate are scalable and compatible with current industrial techniques for semiconductor device fabrication. Such thin film Li ion batteries (TFLIBs) readily allow for miniaturization, are safe, and have long lifetime, making them excellent candidates to power an emerging class of autonomous micro-electronic devices. The capacity of TFLIBs is determined by the thicknesses of the cathode and anode films. Making thicker electrodes reduces the power of the battery due to slow solid state ionic diffusion and increases susceptibility to fracture during battery cycling. To overcome these problems, 3D batteries of various architectures are proposed in literature where the thin film components are deposited on 3D frameworks. The increased area results in higher capacity while thin film components allow for fast operation and no cracking. The implementation of such 3D batteries has been lacking until recently due to material limitations. We report on the fabrication of working inorganic 3D Li ion batteries with thin film components deposited by RF sputtering and e-beam evaporation on silicon 3D frameworks in the form of pillar or cone arrays. These 3D frameworks with micrometer size features were dry etched in flat Si wafers through the resist patterns defined by nano-imprint or photo- lithography. In the 3D batteries, LiCoO2, LiPON, and (Si or Al) were used as cathode, electrolyte, and high capacity alloying anode, respectively. The distinctive feature of our 3D batteries is that the micro-structured cathode and anode inter-penetrate each other and are separated by a thin solid electrolyte layer. The batteries were characterized by galvanostatic cycling, cyclic voltammetry, SEM, and cross-sectional TEM. The successful operation of the 3D batteries is demonstrated although the performance of the batteries is presently lower than that of 2D analogues (TFLIB). The issues affecting the performance are discussed such as the inter-diffusion of the materials during the fabrication shown by cross-TEM analysis. This work contributes to the effort towards increasing of the capacity per footprint area of scalable inorganic all-solid batteries.

Metal-ion polymer batteries are associated with some safety concerns, one of which is the expansion/contraction of the cell while charging and discharging that results in delamination of electrodes, and may also cause damage to the casing and result in exposure of the lithium to the ambient; which in turn results in vital reaction of lithium with the moisture in the ambient and may cause fire and explosion. One concept to resolve this issue is to investigate flexible and stretchable materials as electrodes and electrolyte for this class of secondary cell batteries. However, one main concern is the poor electric and ionic conductivity of flexible and stretchable materials. We present the study of structure-property-processing correlation in flexible-stretchable metal-ion polymer batteries, with insight into the fundamental science of the soft materials in electrochemical energy storage. We have integrated soft functional materials into the structure of gel polymer electrolyte and electrodes to allow fabrication of flexible-stretchable metal-ion polymer batteries, to prevent issues arose from expansion/contraction of the electrochemical cell.

For lithium ion battery, a range of materials has a high theoretical capacity and it is very often that this type of material is prone to cause the fast capacity fading of the battery. To address this problem, a range of microstructural designing concepts has emerged, most notably such as composites based on nanowires, nanotubes, and nanoparticles as well as in combination with surface structural and chemical modifications. For a lot of cases, the nanoscale designing concept is inspired and verified by direct in-situ imaging or spectroscopic analyzing of structural and chemical evolution of the materials under dynamic operating condition. In this presentation, we will review, in retrospective and perspective, the overall progress of in-situ TEM study of battery materials, especially focusing on the challenges that related to anode, cathode, and solid electrolyte interface (SEI) layer for lithium ions battery and beyond, typically such as sodium and magnesium ions. In particular, we will describe the development of the liquid electrochemical cell that enables operando TEM studies of electrode materials under battery operating conditions.

An understanding of the electrochemical processes at electrode-electrolyte interfaces such as lithium intercalation or reaction with the electrode, Solid Electrolyte Interface (SEI) formation, lithium dendritic growth and so on is critically important for the design of batteries with improved performance. Using the newly designed electrochemical liquid TEM cell, we have directly observed such processes at the electrode-electrolyte interfaces in a commercial LiPF6/EC/DEC electrolyte for lithium ion batteries. During the charge-discharge cycles, electrochemical lithiation induced structural transformation of electrode, local strain and structural distortion from the inhomogeneous lithiation have been observed. Dendritic growth of lithium metal and the subsequent stripping of lithium have also been imaged. The effect of an addition of additives in the electrolyte on metal deposition has been investigated by in situ studies. Additionally, we were able to track the formation of SEI layer on the electrode and quantify its stability and growth kinetics under cyclic voltammetry. These results shed lights on strategies of improving electrode design for better performance and reducing short-circuit failure of lithium ion batteries.

Controlling the transport of lithium (Li) ions and their reaction with electrodes is central in the design of Li-ion batteries for achieving high capacity, high rate and long lifetime. The flexibility in composition and structure enabled by tailoring electrodes at the nanoscale could drastically change the ionic transport and help meet new levels of Li-ion battery performance. Si-Ge composite anodes are regarded to possess a balanced and enhanced performance in Li-ion batteries due to the combination of the high capacity of Si and excellent rate capability of Ge. In this presentation, Li ion transport in Si-Ge heterostructures (Ge/Si core/shell and Si/Ge core/shell nanowires) was systematically studied inside the TEM in real-time. In sharp contrast to the core-shell lithiation behavior in Si/Ge core/shell nanowires as well as pure Ge and pure Si nanowires, pure axial lithiation was observed in Ge/Si core/shell nanowires, which demonstrated that radial heterostructuring (Si shell on Ge core) can suppress the commonly observed surface insertion of Li ions that has been reported in all nanoscale systems to date, and exclusively induce axial lithiation along the <111> direction in a layer-by-layer fashion. The deposition of a conformal, epitaxial, and ultrathin Si shell (1~5 nm) on Ge nanowires creates an effective chemical potential barrier for Li ion diffusion through the surface, allowing only axial lithiation and volume expansion. Our work is the first direct observation of the dramatic interfacial effect on ionic transport at the nanoscale. Specifically, we demonstrate that interface and bandgap engineering of electrochemical reactions can be utilized to control the nanoscale ionic transport/insertion paths, which provides a powerful additional degree of freedom to define the electrochemical reactions in Li-ion batteries.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Having high energy densities and light weight, lithium ion rechargeable batteries are widely used for small electronic devices. Along with commercially used graphite carbon, tin oxide has been researched as a promising anode material for high energy lithium ion batteries. In addition, SnO2 material has an advantage of cycle performance because lithium oxide buffer layers which are formed in the first charging process prevent from fast agglomeration and degradation. Furthermore, various potential anode candidate materials undergo electrochemical reactions, i.e. conversion reaction, similar to SnO2, which makes it worthy of researching SnO2 as lithium ion battery anode material. In lithium ion batteries, it is believed that SnO2 undergoes irreversible conversion reaction forming lithium oxide and reduced tin metal in the first charging process and repeats dis/charging by reversible LixSn de/alloying reaction after then. However, some researchers raised the possibility of partial reversibility of the conversion reaction based on the unexpected experimental peak of I-V curves and the capacity that exceeding theoretical prediction. Therefore, we analyzed the partial reversibility of the SnO2 conversion reaction by transmission electron microscopy(TEM) to reveal the uncertainty of SnO2 reaction in lithium ion batteries.
For tracing single SnO2 particle on each reaction step and observing changes of the single SnO2 particle, a TEM grid which SnO2 particles are dispersed on was enclosed in a coin cell and dis/charged. The dis/charged coin cell including the TEM grid was disassembled right after each major reaction step and the SnO2 particles on the TEM grid were analyzed by TEM study. This approach allows to examine realistic reaction mechanism in the aspect that it reflected real battery cell system. We observed different types of SEI layers at each step, instead of reversed SnO2. It poses the possibility that the unexpected phenomena may originate from reversibility of SEI layers. The detail identification of the unexpected experimental peak on I-V curves and the possibility of partial reversibility of SnO2 anode conversion reaction will be discussed.

In the search for earth-abundant, high capacity lithium-ion anode materials, the significant advantages of germanium are often overlooked due to the focus given to silicon anodes. Both Ge and Si have significantly higher theoretical lithium capacity (1600 mAh/g and 4200 mAh/g, respectively) compared to the carbon-based anodes (372 mAh/g) presently used in Li-ion batteries. However, Ge is more electronically conductive and has a higher room temperature Li-ion diffusivity. Due to their high capacities, Ge and Si anodes both suffer from large volume changes (up to 400%) during electrochemical cycling. Repeated expansion and contraction of these materials lead to fracturing and eventual pulverization resulting in the loss of electrical contact with the current collector and ultimately battery failure.
We will present 2D in operando X-ray microscopy results, which directly track the crack formation and density changes in micron-sized particles during battery operation. By studying particles within a number of ~40 micron regions, we have discovered that volume expansion during lithiation is particle size dependent, but the subsequent volume contraction is not. Moreover, we have found that only the largest particles actively participate in the second (de)lithiation cycle. Finally, from 2D images collected as a battery is rotated, we have reconstructed 3D images of particles at different points along the electrochemical cycle. With this in situ tomographic information we have quantified the volume change in particles and measure the changes in porosity or density as particles (de)lithiate.

Typically, experimental approaches for chemical phase imaging of battery materials have been carried out using ex-situ methods [1-3], which can be performed with multiple samples of interest harvested from cells at the different stages of reaction. While these approaches are well established, so far, experimental measurements about chemical phase evolutions in Li ion electrodes remain challenging, especially if synchronization with the morphological evolution is sought during the operation of battery. The operando observation of battery materials offers deeper insight into the veiled electrochemical reaction mechanisms that are controlled by kinetics under load; opening the circuit to recover a sample can lead to relaxation of the materials to a different, thermodynamically stable state.
In this study, we carried out operando full-field transmission X-ray microscopy (FFTXM) at 30 nm spatial resolution on a single Li-ion battery cathode particle during electrochemical lithium deintercalation, using well-defined spinel-type Li_1+xMn₂O₄ microcrystals. Chemical phase maps from quantitative analysis of pixel-by-pixel X-ray absorption near edge structure (XANES) spectra and morphological information of optical-density (OD) images at the post-absorption-edge region were obtained at the different states of charge. Our work revealed the dynamics of two-phase and solid-solution reactions followed by significant crack generation and propagation along the highest mismatch plane, which suggest a strong correlation between them. We believe our work is a valuable new asset for understanding phase transition mechanisms.
1. Boesenberg, U., et al., Chemistry of Materials, 2013. 25(9): p. 1664-1672.
2. Chueh, W.C., et al., Nano Letters, 2013. 13(3): p. 866-872.
3. Meirer, F., et al., Journal of Synchrotron Radiation, 2011. 18(5): p. 773-781.

Coherent x-ray diffractive imaging (CXDI), a lensless form of microscopy capable of discerning electron density and strain with 20 nm resolution, is used to map the strain evolution of a single LiNi1/2Mn3/2O4 high voltage spinel cathode particle in a functional battery as it is cycled in-situ. The evolution of compressive/tensile strain reveals a number of interesting effects. For instance, a strain front nucleates and propagates inward/outward during discharge/charge. Strain negatively correlates with Lithium amount in the first cycle, eventually becoming uncorrelated upon longterm cycling. The particle develops alternating stripes of compressive/tensile strain, perpendicular to the 111 direction, that suggests self organizing behavior. A number of other effects are explored. We demonstrate that CXDI is a powerful diagnostic tool to reveal correlation between strain and electrochemistry at the single particle level and offers valuable information for electrode/battery modeling and future battery design.

Layered Li1.2Ni0.2Mn0.6O2 (LMNO) nanoparticles and spinel LiMn1.5Ni0.5O4 are shown to be a very promising next generation high capacity cathode materials for Li-ion batteries. However, the structure, cation ordering and distribution in the cathode, before and after cycling is still under debate [1,2]. In addition, the phase transformation of layered cathodes to spinel on high voltage cycling is postulated to result in capacity fading and poor rate performance, limiting its application in heavy-duty electric vehicles [3]. These important structural, compositional and chemical changes as a function of cycling can be clarified using a combination of atom probe tomography (APT), scanning transmission x-ray microscopy (STXM) and transmission electron microscopy (TEM) analysis. Recent scanning TEM x-ray energy dispersive spectroscopy (STEM-EDS) tomography results have indicated the segregation of Ni at surfaces and grain boundaries in layered cathode material which is proposed to act as a barrier to the Li transport [4]. A lack of Ni or Mn segregation in LiMn1.5Ni0.5O4 is also observed by STEM-EDS. Laser-assisted, atom probe tomography (APT) studies of the LMNO layered cathode materials helped to quantify the Ni and Mn segregation observed qualitatively by STEM-EDS in addition to providing evidence for preferential Li segregation to Mn-rich regions over the Ni-rich regions. Uniform distribution of Mn, Ni and Li was observed in LMNO spinel particles using APT analysis in agreement with the STEM-EDS measurements. The LMNO layered and spinel cathodes before and after cycling were also analyzed using STXM on Advanced Light Source beamlines 5.3.2.1 and 11.0.2 to study the Mn, Ni L edges and O K edge x-ray absorption spectra. A direct correlation of STXM, TEM and APT analysis of the same nanoparticle was also conducted using a multimodal chemical imaging suit. Such detailed characterization of Li ion battery cathodes when combined with electrochemical battery performance results, could be used to understand the structural, chemical and compositional changes as a function of electrochemical cycling.
[1] Jarvis, K.A., et al.. Chem. Mater., 2011. 23, 3614-3621.
[2] Armstrong, A.R., et al., Journal of the American Chemical Society, 2006. 128, 8694-8698.
[3] Hong, J., et al., J. Mater. Chem., 2010. 20, 10179-10186.
[4] M. Gu et. al. NanoLetters Sept. 17, 2012

LiFePO4 is one of the most widely studied positive electrodes for lithium-ion batteries. However, the lithium intercalation mechanism at both the single particle and the electrode level is not well understood. The absence of a spatially and chemically resolved in operando study of Li-ion batteries has made it difficult to understand the dynamic intercalation process. As a result, the lithium intercalation process remains controversial.
We employed in operando, chemically resolved x-ray microscopy to image LiFePO4 electrodes in standard liquid electrolytes and realistic geometries during charging and discharging. By probing the iron K-shell absorption edge, we obtained a state-of-charge map in real-time at ~30 nm resolution with a ~30 micron field of view. We achieved simultaneously time and spatial resolution as well as reasonable statistics by imaging a large number of particles. We observed that charging and discharging in a LiFePO4 electrode is highly inhomogeneous, and that certain regions of the electrode intercalate preferentially. We will also present a new model of lithium intercalation in a many-particle system based on our in operando results.

Understanding degradation and failure mechanisms of battery electrodes and their real three dimensional (3D) microstructure is essential for developing high performance batteries for electric vehicles and energy storage applications. Although the irreversible microstructural transformations in battery electrode materials is one of the key processes associated with battery degradation and failure, the mechanisms that lead to it are poorly understood. Moreover, existing data is not sufficient to draw clear guidelines for better electrode design. Recent advances in nano tomography have allowed the characterization of electrode microstructure in 3D with resolution of 10 nm; however, there is a clear gap in the application of these techniques for the study of battery electrodes and battery performance. This study will utilize advanced tomography techniques for investigating battery electrodes. Focused Ion Beam (FIB) and X-ray tomography are used for quantifying the 3D microstructure of prospect electrodes such as lithium iron phosphate (LFP) cathodes and graphite mesocarbon microbrad (MCMB) anodes. Specifically, their porosity, tortuosity factor, surface area, connectivity and phase distribution are derived. The complexity in the MCMB anode microstructure suggests inhomogeneous local lithium ion distribution would occur within the anode during operation.

Tortuosity of lithium ion battery (LIB) porous electrodes has traditionally been a difficult value to experimentally quantify, yet it is key to performance and safety of LIBs. Tortuosity (tau;) and porosity (ε) are related through the generalized Bruggeman relation: tau;=ε^-α. Here we show that the Differential Effective Medium (DEM) Approximation [1] provides a facile analytical approach to accurately predict the exponent, α, so that the tortuosity of an electrode can be determined a priori for a given active material and electrode porosity [2]. As input, the DEM Approximation requires only particle size distribution obtained from laser diffraction and a sampling of particle major and minor axes from scanning electron microscope images of the active material powder. To demonstrate the accuracy of the DEM Approximation, we compare the directional tortuosities predicted by DEM to those determined experimentally using reconstructions of synchrotron x-ray tomography of lithium ion battery [3]. The validity of such a simple method will enable the rational optimization of material shape and size distribution to achieve a desired electrode performance at a specific price point. To this end, we present an open source script for performing these calculations that can be used by material researchers to determine the tortuosity of an electrode that will result from their material.
1. S. Torquato, Random Heterogeneous Materials, Springer , New York (2002).
2. M. Ebner, D.-W. Chung , R. E. García , and V. Wood, Tortuosity Anisotropy in Lithium-Ion Battery Electrodes Advanced Energy Materials (2013).
3. M. Ebner, F. Geldmacher, F. Marone, M. Stampanoni, X-Ray Tomography of Porous, Transition Metal Oxide Based Lithium Ion Battery Electrodes, Advanced Energy Materials (2013).

Tortuosity is an important parameter for characterizing transport properties of multi-phase structures, and is of interest in a broad range of fields such as energy storage and conversion materials. A distance propagation method is presented for calculating tortuosity with relatively low computation time from three-dimensional nano-tomographic data. The method, which can be applied to any porous medium, is tested against a diffusion-based tortuosity simulation on two 3D microstructures: a LiCoO2 cathode electrode of lithium ion battery measured by x-ray nano-tomography and a lanthanum strontium manganite-yttria-stabilized zirconia, solid oxide fuel cells cathode measured using focused ion beam-scanning electron microscopy serial sectioning. The present method is shown to provide good-agreement with the effective diffusion-based tortuosity values. Moreover, a novel concept of tortuosity distribution is developed to provide a more comprehensive picture of inhomogeneous microstructures where tortuosity depends on the actual three-dimensional paths. Instead of using one single tortuosity value, the tortuosity distribution both as spatial distribution map and also statistic histogram can provide a more complete description.

It is well-known that high-power and high-energy lithium ion cells require different design rules for their electrode microstructures. Even though their distinctive features are obvious, conventional analysis methods fail to quantify the key properties of different three-dimensional electrode microstructures.
As tomography methods have proven to be powerful tools [1], we systematically apply them herein for 3D electrode reconstructions of two state-of-the-art cylindrical consumer cells, one of them being a high-energy cell, the other one being a high-power cell. Based on X-ray micro-CT reconstructions of the graphite anodes, and FIB/SEM reconstructions of the LiFePO4 and LiCoO2 cathodes, comprehensive sets of structural parameters are obtained. For the first time, an in-depth analysis of (a) volume fractions, (b) surface areas, (c) particle size distributions and (d) tortuosity, gives insight into the different design goals of the electrodes. Furthermore, the different design rules required by the strongly differing material properties of LiFePO4 and LiCoO2 become visible. In addition, electrochemical impedance spectroscopy [2], as well as charge and discharge measurements were performed at the same types of electrodes. The measurements of the electrodes are discussed and shed light on the relation between electrode microstructure and cell performance.
References:
[1] M. Ender, J. Joos, T. Carraro, E. Ivers-Tiffée, J. Electrochem. Soc. 159 (2012) A972-A980.
[2] J. Illig, M. Ender, T. Chrobak, J.P. Schmidt, D. Klotz, E. Ivers-Tiffée, J. Electrochem. Soc. 159 (2012) A952-A960.

All solid-state batteries are promising candidate for future energy storage systems with high energy density and power density. The most important issue to be solved is materials for the solid electrolyte. Lithium superionic conductors promise the potential to replace organic liquid electrolytes and thereby improve the safety of next-generation high-energy batteries. The Li10GeP2S12 (LGPS) has an extremely high ionic conductivity of over 10-2 S cm-1 at room temperature and its value is comparable to that of liquid systems. The LGPS has a three-dimensional framework structure, which consists of the (Ge0.5P0.5)S4 tetrahedra, PS4 tetrahedra, LiS4 tetrahedra, and LiS6 octahedra. This framework structure provides a one-dimensional lithium conduction pathway along the c axis. A certain range of solid solution was confirmed and the conductivity varies with the lithium content in the conduction pathway. The structure analysis based on the neutron diffraction study provided the information of conduction mechanism of its extremely high ionic conductivity. The materials variety based on the LGPS structure is important for the future practical applications. The cationic and anionic substitutions affect the ionic conduction and stability of the electrolyte. The LGPS was examined as a solid electrolyte for the all-solid-state battery and the battery demonstrated that the high ionic conductive electrolyte has advantages for the rate characteristics.

Solid-state electrolytes exhibit good safety and stability, and are promising to replace current organic liquid electrolytes in rechargeable battery applications. In this talk, we will present our efforts at developing scalable first principles techniques to design novel solid-state electrolytes. Using the recently discovered Li10GeP2S12 lithium super ionic conductor as an example, we will discuss how various properties of interest in a solid-state electrolyte can be predicted using first principles calculations.[1] We will show how the application of these first principles techniques has suggested a chemical modification, Li10SnP2S12, that retains the excellent Li+ conductivity of Li10GeP2S12 at a significantly reduced cost.[2] This modification has recently been synthesized, and the measured Li+ conductivity is in excellent agreement with first principles predictions.[3] We will conclude with a demonstration of how relatively expensive first principles calculations can be intelligently scaled and combined with topological analysis to be a useful screening tool for novel solid-state electrolytes.
References:
[1] Mo, Y.; Ong, S. P.; Ceder, G. Chem. Mater., 2012, 24, 15-17, doi:10.1021/cm203303y.
[2] Ong, S. P., Mo, Y., Richards, W. D., Miara, L., Lee, H. S., & Ceder, G., Energy & Environmental Science, 2013, 6(1), 148. doi:10.1039/c2ee23355j
[3] Bron, P.; Johansson, S.; Zick, K.; Schmedt Auf der Günne, J.; Dehnen, S. S.; Roling, B. J. Am. Chem. Soc., 2013, doi:10.1021/ja407393y.

All-solid-state batteries have the potential to dramatically improve the capacity and safety of high-density energy storage. Inorganic electrolytes with sufficiently high conductivity and mechanical and thermal stability are needed to develop these batteries. Understanding the effect of correlation, lattice properties and disorder on Li conductivity will provide design rules to accelerate high-throughput screening of potential electrolytes. Using a recently synthesized highly conductive electrolyte candidate, Li₃InBr₆, we explore the role of phonon modes, 3D channels and lattice strain on Li diffusivity using first-principles molecular dynamics simulations. The insights gained from our in-depth characterization of the Li transport mechanism in this promising material will aid the search for better inorganic solid-state batteries.
This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.

Standard Li-ion batteries utilize a liquid electrolyte which, although exhibiting high ionic mobilities, suffer from substantial drawbacks including the off-gassing of polymer solvents, safety concerns prohibiting the use of metallic Li as the anode and a narrow electrochemical stability window which leads to the formation of what is commonly referred to as the solid electrolyte interphase layer. Although using solid electrolytes will reduce or eliminate these issues, the ionic conductivity is not typically high enough to warrant their use in Li-ion batteries. To explore this issue, we investigate phase stability and ionic transport mechanisms in a recently discovered superionic conductor, Li3OCl, from first principles. We identify a low-barrier three-atom hop mechanism involving Li interstitial dumbbells. This hop mechanism is facile within the (001) crystallographic planes of the perovskite crystal structure and is evidence for the occurrence of concerted motion, similar to ionic transport in other solid electrolytes. Although the band gap of Li3OCl exceeds 5 eV (point to good electronic stability), the metastable antiperovskite becomes susceptible to decomposition into Li2O2, LiCl and LiClO4 above an applied voltage of 2.5 V, suggesting that these compounds are most suited for low-voltage Li batteries.

Recently Li-ion-conducting solid electrolytes have received intensive research interest, as they provide solutions for issues associated with the organic liquid electrolytes in conventional Li-ion batteries. However, despite the relatively high bulk conductivity achieved in many solid electrolytes, the grain-boundary conductivity is frequently low and limits the application. Detailed atomic structure and elemental distribution on the grain boundaries in these materials must be revealed in order to fundamentally understand the origin of large grain-boundary resistance. Such studies, however, are currently very rare. Here we present a detailed atomic scale study on the conduction behaviors of an extensively studied solid electrolyte (Li3xLa2/3-x)TiO3 (LLTO). Using aberration-corrected scanning transmission electron microscopy (STEM) and the associated electron energy loss spectroscopy (EELS) analysis, we found that the large grain-boundary resistance of LLTO arose from the intrinsic local structural reconstruction, which is energetically not favorable for Li accommodation. Therefore, large flux of charge carriers was unlikely to occur both along and across the grain boundary, leading to the poor grain-boundary conductivity. The relationship among the processing condition, microstructure, and ionic conductivity was established. And the ionic transport behavior in LLTO is further compared to that in garnet-type Li7La3Zr2O12. These results paved the way for further improvement of the Li-ion-conducting solid electrolytes.

A great challenge of all-solid state lithium-ion rechargeable batteries (LIBs) for practical use is reduction of the large charge transfer resistance at the interface between the electrode and electrolyte. One the basis of these backgrounds, we herein propose a new fabrication route to smart interface constructing of a stacking assemblies of hexagonal-plate like shaped LiCoO2 single crystals layer and densely packed garnet-type Li5La3Nb2O12 crystal layer. The conversion of Nb metal film to Li5La3Nb2O12 crystal layer was performed at 500 oC for 10h under ambient atmosphere by using LiOH molten salt (flux) with La2O3 and LiOH as solutes. The supported Nb film was deposited onto the LiCoO2 single crystals layer, and was used as a Nb source. The molarity of LiOH as a flux and the total solute was typically controlled to be 5 mol%. The metallic Nb film was completely converted to the single phase Li5La3Nb2O12 crystal layer consisted of densely-packed, idiomorphic crystals. SEM observation revealed the individual Li5La3Nb2O12 crystals were single crystal and typically shaped as a polyhedral structure. The crystal phase, size, and crystallinity were strongly depended on the growth conditions. Cross-sectional SEM observation and XPS analysis strongly suggested that their interfaces were connected without impurities formation. Further detail crystallographic natures and electrochemical characteristics will present in the MRS spring meeting 2014.

Lithium ion batteries are now, arguably, reaching the maximum energy density that can be achieved in the 18650 format using chemistry based on graphite anodes and Co-based cathodes. In order to achieve a step change in the energy density of future lithium batteries, the anode needs to change to either intermetallics, such as Sn, Si or to pure Lithium metal. Alternatively, cathodes with high operating potentials, those greater than 4.6 V vs Li|Li⁺, could be used. However, using standard aprotic-based electrolytes at these potentials creates issues with electrolyte oxidation, transition metal dissolution and current collector corrosion during cycling.
Ionic Liquids have been discussed as a potential replacement for standard aprotic-based electrolytes due to their superior physical properties such as thermal and (electro)chemical stability. We have been examining a number of ionic liquid electrolytes, salts and additives to determine the effect of combinations on the cyclability of high voltage cathodes. Using techniques such as SECM, we have been able to understand the effect of ionic liquid electrolytes with these materials and examine methodologies to improve performance [1].
Beyond these incremental improvements, the use of the metallic electrode, such as Lithium, can deliver a 10-fold increase in the specific energy over graphite-based materials. When used in devices such as Lithium - Sulfur and Lithium - Air, these devices can deliver theoretical capacities of 2567 Wh.kg^-1 and 3505 Wh.kg^-1 respectively; over 6 times greater than current technologies [2].
To enable these high energy devices the electrolytes used to electrodeposit the metal, in this case lithium, needs to allow two-dimensional plating to ensure even deposition without the formation of dendrites. As a consequence CSIRO, together with a number of our collaborators, have been at the forefront of developing new ionic liquid electrolytes which allow lithium to be plated and stripped with high columbic efficiency and without dendritic growth [3, 4, 5].
In this presentation, we will outline our research into the replacement of traditional aprotic electrolytes with ionic liquid electrolytes for lithium metal batteries, from ab initio and molecular dynamics simulations through synthesis and fundamental electrochemical characterization. We will also describe results from devices and post-mortem analysis focusing on the morphology of the lithium metal anode.
[1] G. A. Snook, T. D. Huynh, A. F. Hollenkamp, A. S. Best, J. Electroanal. Chem., 687 2012 30 - 34.
[2] P. G. Bruce, L. J. Hardwick, K. M. Abraham, MRS Bulletin, 36 2011 506 - 512
[3] P. C. Howlett, D. R. MacFarlane, A. F. Hollenkamp, Electrochem. Solid State Lett., 7 (5) 2004 A97 - A101
[4] A. S. Best, A. I. Bhatt, A. F. Hollenkamp, J. Electrochem. Soc., 157 (8) 2010 A903 - A911.
[5] G. H. Lane, A. S. Best, D. R. MacFarlane, A. F. Hollenkamp, M. Forsyth, J. Electrochem. Soc., 157 (7) 2010 A876 - A884.

Fast Li-conducting ceramic electrolytes are foremost components for the development of next generation secondary batteries with increased stability, life and safety. Most efforts have been focused on trying to develop materials with higher conductivity and on the understanding of the bulk ionic conduction mechanisms. However, no special attention has been paid to processing and moisture sensitivity issues (1). In particular, Li3xLa2/3-xTiO3 (LLTO) has been reported to have the highest bulk Li-conductivity in a ceramic material with 10-3 S/cm at 25 C with x = 0.11. However, the high grain boundary resistivity of this system decreases the total conductivity to an order of 10-5 S/cm (2 ). Another kind of materials receiving great attention are Li-stuffed garnet materials with the general formula LixB3C2O12 (x > 3) achieving ionic conductivities higher than 10-4 S/cm at room temperature for the cubic-stabilized phases of different compositions like Ga-doped Li7La3Zr2O12. However sinterability is a major issue for the processing of these materials (3).
This study provides for the first time, a better understanding of the importance of moisture control during the processing of Li-conducting ceramics as it is a limiting factor for their use as solid state electrolytes. For this purpose, LLTO and Ga-doped Li7La3Zr2O12 electrolytes were sintered in air, synthetic air and pure oxygen. Impedance spectroscopy combined with 1H an 7Li solid state NMR were used to monitor the Li exchange by protons from moisture and its effect in the Li conductivity while scanning electron microscopy was used to evaluate the effect on the microstructure of the samples.
We observed a considerable moisture-dependence on the percentage of densification of the samples and the Li-conductivity with the degree of Li-H exchange. Both sets of materials show a substantial increase of the densification with densities around 95% when sintering in pure O2. Moreover, Li populations with different motilities have been identify and directly correlated to the presence of H in the structures due to Li-H exchange. For instance, the conductivity at the grain boundary (comparing equivalent grain size samples) of LLTO have been increased by more than half a decade to 8.34 10-5 S.cm-1 when preventing protonation of the ceramics using dried synthetic air or pure oxygen. The independency of activation energies on sintering conditions, may indicate that the increase of conductivity is only related to an increase of charge carriers thanks to the hindering of the Li-H exchange and not to a change in the conduction mechanism in these systems.
1-Bohnke, O. et al. Solid State Ionics 188, 2011, 144
2- Inaguma, Y., et al. Solid State Comm 86, 1993, 689
3- Shinawi, H.E et al. Journal of Power Sources 225, 2013, 13

Recent work has shown that many of the so-called “stuffed Li garnets”, namely those garnets having more than 3 Li⁺ cations in the formula unit, are excellent fast-ion conductors with values of approximately 10^-4 S/cm at RT [1,2]. Their good chemical and thermal stability, as well as their wide energy potential window, are also important properties making them excellent candidates as possible electrolytes in all-solid-state Li-ion batteries. At room temperature, end-member Li₇La₃Zr₂O₁₂ (LLZO) is tetragonal, I4₁/acd, with a lower conductivity compared to the cubic, Ia-3d, modification, which is only stable above 150 °C. It has been shown that the higher conducting cubic phase can be stabilized at room temperature through the doping of small amounts of Al³⁺ [4] or other cations (e.g. Ga³⁺, Fe³⁺, etc.). Thus, the role of dopant cations and their effect on the conductivity and phase stability of LLZO needs to be carefully studied. We addressed two important issues:
1.) The energy site preference of Al³⁺ in LLZO.
2.) A simulation of ²⁷Al MAS NMR spectra of Al³⁺-doped LLZO to compare to published experimental results that are difficult to interpret.
To do this, we are using DFT methods implemented in the Wien2k code [3]. We calculated the energetics and the NMR parameters for Al³⁺ located in various structural sites in LLZO. Our results show that Al³⁺ prefers the tetrahedrally coordinated 24d site and a distorted 4-fold coordinated 96h site in the space group, Ia-3d. Al³⁺ has been reported to occur in regular octahedral coordination at a 48g site, but we find no evidence for this. Because the site energies for Al³⁺ atoms are slightly displaced from the exact crystallographic sites (i.e., 24d and 96h) are similar, this leads to a distribution of slightly different local oxygen coordination environments. Thus, broad ²⁷Al NMR resonances result, reflecting the distribution of slightly different isotropic chemical shift and quadrupole splitting values.
[1] Cussen, E. J. Mater. Chem.2010 (20) 5167-5173.
[2] Murugan, R.; Thangadurai, V.; Weppner, W. Angew. Chem.2007 (119) 7925-7928.
[3] Blaha, P.; Schwarz, K.; Madsen, G. K. H.; Kvasnicka, D.; Luitz, J. WIEN2K, Techn. Universitat, Wien, Austria (2001) ISBN: 3-9501031-1-1-2. p. 21-8.
[4] Geiger, C. A.; Alekseev, E.; Lazic, B.; Fisch, M.; Armbruster, T.; Langner, R.; Fechtelkord, M.; Kim, N.; Pettke, T.; Weppner, W. Inorg. Chem.2011 (50) 1089-1097.

Lithium batteries using polymer electrolytes (PEs) have been found as potential energy sources for various applications due to their improved safety reliability. Though purely solid polymer electrolytes are most beneficial, the room temperature ionic conductivity (10^-4 S cm-1), transference number and electrochemical performance of these electrolytes are poor [1, 2]. In this scenario, to utilize the beneficial characteristics of both (liquid electrolyte and SPE) systems, hybrid electrolyte concept called polymer gel electrolytes (PGEs) which provides lighter and safer batteries with longer shelf life, leak proof construction and easy fabrication into desired shape and size was explored. Amongst the several factors which influence the performance of PGEs, reduction of ionic coupling and increasing the free lithium ion content without affecting the mechanical properties is the most critical one. In the present work, we are tackling both the issues by using a lithium based glass ceramic prepared by sol gel method which has a conductivvity of 10^-2 S/cm to improve both the mechanical and electrochemical properties.X ray diffraction studies show single phase, phase pure material. A series of P(VdF-co-HFP)/LAGP composite fiber based electrospun membranes are prepared. The morphology of the membrane is studied using field emission scanning electron microscope (FE-SEM). The membranes are made up of fibers of ~1 µm diameter. The interlaying of fibers offers high porosity (~88%). The membranes exhibit a high electrolyte uptake of ~700%. The thermal and mechanical properties of the membranes are studied and it is seen that the properties improved with the addition of LAGP. The temperature dependent ionic conductivity and electrochemical performance is studied. The polymer composite electrolytes (PCEs) show a high ionic conductivity in the range of 6*10-3 S/cm at room temperature. Higher ionic conductivities can be achieved even at lower electrolyte loading because of the presence of the additional source lithium ions and high conductivity of LAGP. The PGEs show anodic stability up to 5.5 V versus Li/Li+, and a good compatibility with lithium metal resulting in low interfacial resistance and formation of a stable SEI layer within 4 days. The cell performance of the PCE is evaluated in Li/(LiFePO4) cell at various C-rates at 25 °C. The cell shows an initial discharge capacity of 165 mAh/g and good cycle performance for 100 cycles. The addition of LAGP improves the charge discharge performance and cycling stability of the polymer composite electrolytes at higher C rates.
References
[1] M.R. Palacín, Chem. Soc. Rev. 38 (2009) 2565-75.
[2] P. Raghavan, J.W. Choi, J.H. Ahn, G. Cheruvally, G.S. Chauhan, H.J. Ahn, C. Nah, J. Power Sources 184 (2008) 437-443.

Surface phase segregation behavior has a critical impact on the kinetics of Li insertion/extraction processes taking place at the surface of an olivine electrode particle that undergoes a phase separation during battery charge/discharge. The presence of a surface, which is one of structural defects, usually modifies the kinetics of phase transformation by perturbing the elastic and chemical contributions on the transformation. We employ a comprehensive phase-field model integrating elastic anisotropy, interfacial energy anisotropy, diffusion mobility anisotropy, structural inhomogeneity due to the presence of the surface, and Cahn-Hilliard diffusion kinetics to describe the phase segregation behavior near the surface as well as inside the particle using a nanoscale Li_xFePO₄ particle as a model system. We present the parametric phase-field simulation study to discuss the effects of the surface on the kinetics of lithiation/delithiation and diffusional phase transformations near the surface and to understand the transition from bulk to surface phase behaviors.

In situ characterization methods, such as vibrational spectroscopy and differential electrochemical mass spectrometry (DEMS), are powerful means of investigating the processes occurring in electrochemical cells during operation. Combined Raman and IR spectroscopy offers advantages connected to the complementarity of the two methods. Whereas the former is particularly sensitive to local structural changes of the electrodes, the latter provides an excellent way of probing the interface with the organic electrolyte in lithium-ion batteries. Employing microscopic methods and a specially adapted cell allows the measurement of in situ data with spatial resolution. The application of this combined spectroscopic method to the characterization of the positive electrode material Li1+δMO2+δ (M = Ni, Co, Mn) and negative carbon electrodes will be discussed in this contribution. Depending on the nature of the electrolyte and active material, interface reactions are also often associated with the formation of volatile side-reaction products, especially during the critical initial cycles. Progress in the development and application of DEMS to qualitatively and quantitatively detect evolving gaseous species in situ during cycling will be presented. Independently of the applied technique, further im-provements in performance and safety of batteries will be based on a fundamental understanding of the properties of battery materials and their interactions with the environment.

In conventional lithium cathodes (e.g., LiCoO2, LiFePO4), lithium is inserted and removed from planes or tunnels within the host structure during discharge and charge. While these topotactic reactions ensure good reversibility, the number of available lithium sites within the host structure limits the overall capacity. One route to achieving a greater specific capacity is to utilize all possible oxidation states of a compound through a conversion reaction in which more than one electron transfer occurs per transition metal (TM) ion (as opposed to 0.5minus;1.0 electrons for most intercalation compounds). Although these reactions have been known for some time, the demonstration of reversible electrochemical conversion in TM oxides has renewed hope that these high-capacity electrodes may be used in rechargeable batteries. In addition to the oxides, reversible conversion reactions have been demonstrated in hydrides, sulfides, nitrides, and fluorides. The reaction potentials of these systems scale with the electronegativity of the anion and span a wide range. However, only fluorides have sufficiently high reaction potentials to be suitable as cathodes. Nevertheless, problems with poor kinetics, cycle life, and reversibility (especially with CuF2) are only some of the challenges that hinder the potential commercialization of these electrodes.
In this study we investigated the reversible lithium conversion in FeF2, FeF3 and CuF2 composites via electrochemical and x-ray absorption measurements. We demonstrate for the first time the reversibility of the CuF2 reaction (2Li + CuF2 larr;→ 2LiF + Cu) when prepared as a composite powder. Electrochemical measurements (cyclic voltammetry and dQ/dV) clearly show the Cu0/Cu2+ redox peaks on both the discharge and charge reactions. Similarly, x-ray absorption measurements from a series of CuF2 composite electrodes prepared at different states of lithiation exhibit reversible shifts in the Cu K-edge associated with the Cu0/Cu2+ redox reaction. Although these composites exhibited poor cycling characteristics, the high reversible capacities (>550 mAh/g) at high discharge potentials (>3V) are an encouraging first step in the development of a new high energy cathode.
Partial support for this work was received through the Northeastern Center for Chemical Energy Storage, a U.S. Department of Energy Frontier Research Center.

The delithiation-lithiation process of C-coated olivine LiFePO4 (C/LFP) cathodes with the temperature range between 25 and 55 °C has been investigated using cyclic voltammtery, charge-discharge cycling, and ac impedance spectroscopy. Using polyethylene glycol as carbon precursor, the C/LFP powders are synthesized by an efficient calcination/pyrolysis method at 650 °C. The experimental results reveal that the high-temperature operation of C/LFP cathodes shows an improved capacity at 0.1minus;5 C but negative effect on high-rate cyclic stability. The ac impedance spectroscopy incorporated with equivalent circuit indicates the decrease in equivalent series resistance and the increase in diffusion coefficient (DLi) with operating temperature. The DLi value achieved is as high as 1.49 × 10-12 cm2 s-1 at 55 °C according to the Randles plot, and the apparent activation energy for the ionic diffusion in the C/LFP cathode is approximately 110 kJ mol-1, determined from the Arrhenius plot. On the basis of the results, the improved performance is attributed to high ionic conductivity, high ionic migration rate in solid electrolyte interphase film, high electronic conductivity, and high diffusion rate.

Asymmetric supercapacitors have been attracted great attention because they can work in wide voltage window so that have relative high power density and also high energy density. Recently, cheap transition metal oxides such as manganese oxide, iron oxide and vanadium oxide have been extensively investigated as positive electrode and various carbon materials are used as negative electrode. In this work, a novel hierarchical porous carbon (HPC) and nano-porous manganese dioxide (MnO2) are synthesized and used as negative and positive electrode materials, respectively. Their structures and electrochemical properties are characterized by SEM, XPS, XRD, nitrogen adsorption-desorption determination, cyclic voltammetry (CV), galvanostatic charge-discharge tests and so on. The results from CV tests show that the potential window of the asymmetric HPC/MnO2 supercapacitor can reach 2V, and the CV curves maintain in rectangular shape at 50mV/s of scan rate. The HPC/MnO2 supercapacitor shows an energy density of 18.2Wh/kg at a power density of 500 W/kg and 12.8Wh/kg at a power density of 2003 W/kg.

The functionality of battery electrodes depends on their electronic structure and their microstructure. These may experience significant changes in the course of synthesis of materials, processing of components and operation of the device. It is in general very difficult to monitor these changes with accuracy and confidence. However, detailed knowledge on the interrelation of the properties and processing steps may be crucial for development of better battery materials. I present here a suite of in-situ and operando studies on LiMn2O4-based battery cells with soft x-ray and hard x-ray spectroscopy and scattering methods and showcase the pathogenesis of the spinel materials during operation, along with detailed information of the molecular structure, electronic structure and microstructure depending on the state of charge of the battery. A highlight is the recent first operando x-ray Raman study on such battery cell which allows insight into the bulk electronic structure changes during the Li intercalation process.
References
1. A. Braun, H. Wang, T. Funk, S. Seifert, E.J. Cairns, Depth profile analysis of a cycled lithium ion LiMn2O4 battery electrode via the valence state of Mn with soft x-ray emission spectroscopy, Journal of Power Sources 2010, 195(22), 7644-7648.
2. A Braun, H. Wang, S.S. Lee, EJ Cairns, JP Shim. Lithium K(1s) NEXAFS spectra of lithium ion battery cathode, anode and electrolyte materials. Journal of Power Sources 170 (2007) 173-178.
3. A. Braun, S. Shrout, A. C. Fowlks, B. A. Osaisai, S. Seifert, E. Granlund, E. J. Cairns. Electrochemical in-situ reaction cell for X-ray scattering, diffraction and spectroscopy. Journal of Synchrotron Radiation (2003), 10, 320-325.
4. A Braun, H. Wang, U. Bergmann, M.C. Tucker, Weiwei Gu, S.P. Cramer, and E.J. Cairns. Origin of chemical shift of manganese in lithium battery electrode materials - A comparison of hard and soft X-ray techniques. Journal of Power Sources 112 (1) 231-235 (2003).

Lithium ion batteries (LIBs) are one of the most attractive battery systems based on high energy density, negligible memory effect and a less self-discharge behaviors. As demands increase for LIBs, they have expanded market area from portable electronic devices to large energy storage systems including hybrid electric vehicles (HEVs) and electric vehicles (EVs). However, safety issues are still main obstacles for expanding a new application area of the LIBs because explosion of LIBs are frequently reported up to now. Therefore, many kinds of approach have been attempted to enhance the safety of the LIBs and one of efficient ways is investigation for non-flammable electrolytes to replace combustible organic electrolytes. In this regard, the ionic liquids (ILs) can be one alternative based on their unique properties.
ILs are salts existing in liquid state at room temperature. Because they consists of ions (cation and anion), they have unique physicochemical properties such as wide liquid range, non-volatility, non-flammability, superior thermal stability, high ionic conductivity, and wide electrochemical windows. In addition, these properties can be tunable by combination of various cations, anions and their substituents. Therefore, the ILs have been highlighted as an alternative main solvent or additive to enhance electrochemical performance of the LIBs. However, relatively high viscosity and low Li-ion migration behavior are considered as main obstacles for successful utilization of ILs for LIBs.
In this presentation, we will report novel pyrrolinium-based ILs as functional additives and/or solvent for the LIBs. In organic- and electro- chemical aspect, introducing ether substituents in the ILs would exert a favorable influence to increase ionic conductivity, resulting in increased capacity with cell tests. We would also expect that these solvent mixtures of ILs and carbonate would be much less flammable than the conventional carbonate electrolytes. As expected, the prepared electrolyte mixtures containing more than 60% of ILs were not ignited at all by the flammability test while the mixtures with less than 40% of ILs were found to be flammable. To confirm the electrochemical stability for LIBs, the prepared mixtures were tested for cycle performance with LFP/Li half coin cells. Both the discharge capacity and the retention ratio of these mixtures were better than the conventional carbonate electrolytes.

Battery performance and life testing is an ongoing program at Argonne National Laboratory. Batteries from U. S. Advanced Battery Consortium and U. S. Department of Energy projects are objectively evaluated according to well defined protocols. [1] Testing provides useful information about battery performance changes with time and, combined with statistical analysis and accelerated aging test conditions, allows forecasting performance over the expected lifetime of the devices. [2] This approach, however powerful, does not provide insights into physicochemical causes of device degradation at materials level. To address this issue, we have established a post-test analysis laboratory to elucidate physicochemical changes in Lithium-ion batteries responsible for performance degradation.
Electrochemical performance is often limited by surface and interfacial reactions at the electrodes. However, routine handling of samples can alter the very surfaces that are the object of study. Our approach combines standardized testing of batteries with sample harvesting under inert atmosphere conditions. Cells of different formats are disassembled inside an Argon glove box with controlled water and oxygen concentrations below 2 ppm. Cell components are characterized in situ, guaranteeing that observed changes in physicochemical state are due to electrochemical operation, rather than sample manipulation.
We employ a complementary set of spectroscopic, microscopic, electrochemical and metallographic characterization to obtain a complete picture of cell degradation mechanisms. The resulting information about observed degradation mechanisms is provided to materials developers, both academic and industrial, to suggest new strategies and speed up the Research & Development cycle of Li-ion and related technologies.
This talk will describe Argonne&’s post-test analysis laboratory, with an emphasis on capabilities and opportunities for collaboration. Cell disassembly, sample harvesting procedures and recent results will be discussed.
This work was performed under the auspices of the U.S. Department of Energy, Office of Vehicle Technologies, Hybrid and Electric Systems, under Contract No. DE-AC02-06CH11357.
References:
[1] USABC test manuals can be downloaded from: http://www.uscar.org/guest/article_view.php?articles_id=86
[2] “Statistical methodology for predicting the life of lithium-ion cells via accelerated degradation testing”. E. Thomas, I. Bloom, J. Christophersen, and V. Battaglia. J. Power Sources. 184 (2008) 312-317.

Porous carbon with high surface area, large pore volumes, chemical inertness and high mechanical stability have been extensively studied and used in various applications. The synthesis of mesoporous carbon (2 < pore size < 50 nm), which its extensive applicability such as water purification, adsorbents, molecular sieves, and electrode materials for energy storage devices has been motivated the progress of various fabrication method. To controled and tailored pore structure, template synthesis method has been widely investigated. In this work, polybenzoxazine, a novel phenolic resin, was used as a precursor to produce mesoporous carbon through soft-templating method using Pluronic P123 as a template, and pyrolyzed under nitrogen gas at high temperature. The effect of template loading content was investigated. The BET measurement was used to characterize surface area of nanoporous carbon. The morphology was determined by using SEM and XRD. Electrochemical analyzer was utilized to investigate the electrochemical behavior of the mesoporous carbon electrode.
References:
1. Jang, J., and Bae, J., (2005). Fabrication of mesoporous polymer using soft template method. The Royal Society of Chemistry, 1200-1202.
2. Jin, J., Nishiyama, N., Egashira, Y., and Ueyama, K., (2009). Pore structure and pore size controls of ordered mesoporous carbons prepared from resorcinol/ formaldehyde/ triblock polymers. Microporous and Mesoporous Materials, 118, 218-223.
3. Katanyoota, P., Chaisuwan, T., Wongchaisuwat, A., and Wongkasemjit, S.(2010). Novel polybenzoxazine-based carbon aerogel electrode for supercapacitors.
Materials Science and Engineering B, 167, 36-42.
4. Tanaka, S., Nishiyama, N., Egashira, Y., and Ueyama, K., (2005). Synthesis of ordered mesoporous carbons with channel structure from an organic-organic nanocomposite. The Royal Society of Chemistry, 2125-2127.

Recent advances in miniaturized energy storage devices have been driven by the demand for high-performance compact on-chip energy in a range of form factors. Flexible micro-capacitors have gained considerable attention due to the fast kinetics of ion motion, and thus high power densities. Here, we demonstrate a new method for fabricating all solid-state micro-capacitors. Binder-free micro-patterned electrodes are formed starting from a conventional soft lithography method. A poly(dimethylsiloxane) (PDMS) pattern with interdigitated finger-like channels is first designed and then a multi-walled carbon nanotube (MWNTs) solution is evenly spread onto the patterned PDMS. By repeatedly sticking and peeling back scotch tape, over-coated MWNTs on the channel are completely removed, providing electrically isolated MWNT channels. A poly(vinyl alcohol) (PVA) solution is cast onto the MWNT-patterned side of PDMS. A dried PVA film is demountable from the PDMS and can be peeled off. The patterned MWNTs are completely transferred onto the dried PVA film. Solid-state micro-capacitors are obtained by applying a PVA/H3PO4 gel as an electrolyte on the pattern. The resulting devices are highly flexible and provide reliable power output, suggesting they may be a promising candidate for on-chip energy storage applications with high power demands.

Among the family of carbon-based systems, graphene is one of the youngest members alongside diamond, graphite, fullerenes and carbon nanotubes. There is a significant interest in carbon-based nanomaterials as supercapacitor electrodes owing to their lighter weight, higher electrical conductivity and specific surface area. Moreover, supercapacitors store energy by forming a double layer of electrolyte ions on the surface of conductive electrodes. There is large number of interesting possibilities in creating new designs for such energy storage devices if the carbon-based electrodes can be tailored and engineered to fit new functionalities (i.e. higher stored energy) by forming composites with polymer, for instance. In this work, we present the synthesis of in-situ oxidative polymerization transforming pyrrole to polypyrrole in the presence of functionalized graphene sheets producing high-quality novel 2D hybrids / composites as advanced electrochemical platforms/electrodes for energy storage and conversion. The obtained functional materials are investigated by means of electrochemical and in-situ Raman spectroscopic methods in terms of cyclic voltammetry (CV) with scan rate, electrochemical impedance spectroscopy (ac EIS) determining specific capacitance and resistance, charge-discharge cycling with varying concentration ratio of graphene/pyrrole and charge transfer dynamics by monitoring Raman spectroscopy bands as a function of applied electrochemical bias. The synergistic surface and interfacial interaction due to structural conjugation between the p-type polypyrrole on the surface of negatively charged carboxylated functionalized graphene sheets is anticipated to result in higher charge storage capacity than those of graphene-only or polymer-only films. It is the higher electrical conductivity of p-doped polypyrrole and higher surface area of carboxylated functionalized graphenes promote higher charge accumulation in these (super)capacitors. These results are complemented with AFM and TEM combined with electron diffraction structural techniques to establish property-structure relationship. We also report the optimization of the relative concentrations of carboxylated functionalized graphene in the polypyrrole matrix to maximize the compositions&’ specific capacitance. The work is supported by the author's start-up (SG) and NSF-KY EPSCoR (EPS-0814194 and 3048108525-l4-046) grants.

Effective energy conversion and storage are required for better use of energy due to the inevitable depletion of fossil fuels. Energy storage technology is the key factor in harvesting kinetic energy. In the past decades, there has been an ever-increasing demand for environmental friendly, high performance energy storage systems. Titanium oxide has been extensively investigated as electrode candidate for electrochemical energy storage, such as lithium ion battery. However, the poor conductivity of titanium oxide has limited its application. Carbon black, graphene, and carbon nanotubes (CNTs) are common supplements to electrode materials in order to increase their conductivity.
Three-dimensional (3D) carbon scaffold was made to be an additive to titanium oxide to improve its conductivity. It was made by CNTs (one-dimensional) and graphene oxide (two-dimensional). Titanium oxide was prepared by two-phase hydrothermal method, when the scaffold was introduced to titanium oxide, the specific capacity was 170 mAh/g at 0.3C and it is very close to the theoretical capacity of titanium oxide (175 mAh/g) and performed good cyclic data.

Carbon coated Li4Ti5O12 (LTO) particles have been synthesized by high-temperature calcination and carbonization process. The coating layer has been characterized by high resolution TEM (HRTEM), local X-ray absorption near edge structure (XANES) and chemical scanning transmission X-ray microscopy (STXM) imaging. The LTO samples exhibited a spinel cubic spherical nanocrystal with average sizes around 50-70 nm. TEM and STXM imaging confirmed the graphitic carbon layer with uniform coating thickness on the surface of the LTO nanocrystal.
Electrochemical studies of galvanostatic discharge/charge testing and cycling performance indicated that those LTO particles show much improved rate capability and specific capacity when used as anode materials than un-coated LTO. The uniform carbon coating improved the kinetics of Li4Ti5O12 towards fast lithium insertion/extraction, thus enhancing the electrochemical properties of the Li4Ti5O12 nanocomposites as the anode in Li-ion cell.

There has been growing demand for high-power energy storage systems for use in diverse applications such as hybrid electric vehicles, personal electronics, and industrial power backups. Recent attention has focused on electrochemical capacitors (ECs, also called supercapacitors) to address these demands. ECs are promising new energy storage systems because of their high power density, long cycle life, short charging time, good safety, and simple mechanism. ECs can be classified as electrical double-layer capacitors (EDLC) and Faradaic redox reaction pseudo-capacitors on the basis of their electrode materials and the charge storage mechanism. In general, the energy density for an EC based on the pseudo-Faradaic process is higher than that of an EDLC owing to redox electron movements through the electrode materials. As pseudo-Faradaic electrochemical capacitor materials, transition metal oxides such as vanadium oxide, ruthenium oxide, copper oxide, cobalt oxide, manganese oxide, and nickel oxide, have been qualified. Among them, nickel oxide (NiO) is one of the most important because of its low cost and high theoretical capacitance (2584 F g-1 within 0.5 V), which is similar to that of amorphous RuO2. However, a large specific volume change occurs in the electrode matrix of the metal oxide during the cycling process, thus, leads to pulverization of the electrodes and rapid capacity decay. High resistivity is also another drawback of ECs for practical applications. Therefore, several studies have combined metal oxide and carbon-based materials to improve the cyclability and reduce the resistivity of ECs compared with pristine metal oxides.
In this study, we fabricated amorphous carbon-coated nickel oxide nanofibers (NiC NFs) via electrospinning, vapor deposition polymerization (VDP), and carbonization. In VDP steps, thickness of the coating layer was controlled by adjusting the concentration of the initiator solution (FeCl3) due to the amount control of Fe cations on NiO NFs surface. The specific capacitance of the NiC NFs was ca. 288 F g-1, which is higher than that of pristine NiO NFs (ca. 221 F g-1); the NiC NFs also displayed better cyclability. As a result, the coated amorphous carbon layers limited degradation of the NiO structure during charge/discharge process and enhanced the specific capacitance because of its own EDLC ability. Furthermore, this facile coating method can also be applied to other metal oxides to improve its cyclic abilities and electrochemical properties.

Lithium ion batteries nowadays serve as the most important power source for mobile electronics. Advanced electrode materials with improved performance have become an important research focus recently. Among these materials, silicon (Si) is identified as one of the most appealing candidates for next generation anode material owing to its high specific capacity, 4200 mAh/g. However, Si based anodes suffer from dramatic volume change (300%) due to insertion/extraction of the lithium ions. Huge stress induced by the volume change makes the Si material vulnerable to cracks and pulverization, resulting in failure of the batteries eventually. Besides, the low electrical conductivity associated with the semiconductor nature of Si hinders efficient charge transfer during electrochemical cycling. Thus, successful modification of the Si material or architecting Si into novel structures is essential to realize the high capacity of Si and prolong its retention. Nano-compositing and nano-structuring are now considered as effective strategies to overcome the problems of Si based anodes. On one hand, incorporation of metal material into Si to form composite is an important approach to improve the capacity retention. The electrochemical inactive characteristic of the metal composition is able to buffer the volume change of Si and reduce structural damage. It also helps the charge transfer by increasing the electrical conductivity. On the other hand, an emerging trend in lithium ion battery research is the nano-structures of carbon nanotube (CNT) cores coated with Si shells. Such core-shell heterogeneous nanowires take advantages of the excellent properties of CNTs for improved battery performance. For example, the mechanical strength and stiffness of CNTs enable them to constrain the Si shells, preventing them from excessive expansion while the high electrical conductivity of CNTs facilitates charge transfer during electrochemical cycling. In view of these attempts, we develop a novel anode architecture which combines the merits of nano-compositing and nano-structuring to further improve the performance. In our approach, CNTs are subsequently coated with nickel (Ni) and Si layers, followed by thermal annealing to drive the Ni atoms into the Si layer and form Ni silicide (NiSix). The obtained core-shell CNT-NiSix nanowires perform excellent capacity retention, demonstrating very promising potential applications.

The environmental concerns over the consumption of fossil fuels and the insatiable demand for energy in the 21st century have warranted the development of advanced electrical energy storage devices such as supercapacitors. NiO is considered as a highly promising candidate for supercapacitor electrodes due to its high theoretical capacitance, natural abundance and low cost. In order to improve the energy storage characteristics of NiO supercapacitor electrodes, we studied the effect and limitation of reduced graphene oxide (RGO) coating. We discovered that RGO coating on NiO electrodes significantly improve the specific capacitance of uncoated NiO electrodes. The specific capacitance increased from 374 F/g to 600 F/g. This increase could be due to improved electrode conductivity provided by the RGO layers. Interestingly, the specific capacitance of NiO electrode can also be increased to 962 F/g with the addition of glucose during the solvothermal preparation of the NiO. This increase in capacitance can be explained by the decreased size of NiO flakes as well as the improved conductivity by the reduced thickness of the NiO layer on the carbon paper, which is favorable for electron transport. RGO coating on these glucose modified NiO electrodes only showed moderate improvement of the specific capacitance to 1077 F/g. However, the RGO coated electrodes in both systems showed excellent cycling stability (~99%), owing to the mechanical stability provided by RGO coating. Thus, our findings reveal that the effects of RGO coating in electrode systems are two-fold. One is to increase the electrical conductivity of the electrodes, especially when the electrodes is not highly conductive. If the electrode already has high conductivity, however, this effect is reduced. The second effect is to improve the mechanical stability of the electrode, thus increase the cycling stability of the electrodes. These understandings will be important in the designing of high performance energy storage devices, especially from materials with limited electrical conductivity.

Carbon nanotubes (CNTs) have been shown to increase the cathode conductivity more than carbon black or surface coatings alone. Many of the previous efforts did not attend to the unique challenge that dispersing nanotubes presents. With poor dispersion a larger quantity of CNTs may be required and thus it has been unfortunate that the primary method for dispersing CNTs in battery systems have been methods more appropriate for amorphous carbons, such as ball milling. Furthermore the percolation threshold with good dispersions has not been well established for CNTs in battery composites.
The selection of CNTs is also critical where the cost and capabilities have to be balanced. Single walled CNTs have the highest conductivity and the highest cost and at the other extreme massively multi-walled CNTs are relatively inexpensive but have poorest conductivity. In this study we selected few-walled nanotubes due to their reduced costs and still considerable conductivity.
We investigated methods to incorporate CNTs both before and after battery particle formation; including mixing methods, solvent selection, and surfactants. For battery particle synthesis combinations of water, n-methyl-2-pyrrolidone, ethylene glycol, and tetraethylene glycol were evaluated both with and without surfactants. Additionally we have investigated the stability of the dispersions at both low and high growth temperatures and with subsequent annealing steps. The optimal processes should ensure that the CNTs do not coalescence before the final deposition of cathode material onto the electrode.

All-solid-state lithium ion batteries (LIBs) containing non-flammable solid electrolytes offer improved safety and better chemical compatibility compared with conventional LIBs using combustible liquid organic electrolytes. For practical application of all-solid-state batteries, it is important not only to develop solid electrolyte with high lithium ion conductivity but also to improve their electrochemical performance because the electrochemical performance and interfacial resistance of an all-solid-state battery is strongly affected by the interfacial contact between the electrodes and electrolyte.
In this study, a composite cathode was designed comprising the solid powders of active material and oxide electrolyte coated with glass electrolyte which can form an interface with high adhesion and contact between the active material and polycrystalline powders. LiNi0.6Co0.2Mn0.2O2 (NCM) and Li7La3Zr2O12 (LLZO) garnet-type oxide electrolytes were selected as cathode active material and main solid electrolyte, respectively. We have considered lithium borosilicate (LBS) glass as a promising aid to produce good interfacial contact in the composite cathode as well as to reduce the interfacial resistance due to its relatively high lithium ion conductivity and isotropic ionic conduction.
LLZO was prepared by solid state method and LLZO with highly conductive cubic phase was obtained (~ 1×10-4 S/cm at 25oC). LBS glass can be synthesized through sol-gel process and the conductivity of LBS glass of 25Li2O-15B2O3-60SiO2 was 6×10-6 S/cm at 25oC. To coat NCM and LLZO with LBS, the powders of NCM and LLZO was mixed with the precursor sol of LBS glass, and the densified LBS glass was obtained after aging and heat treatment (~450oC).
The SEM-EDS results showed that LBS glass was uniformly coated on NCM and LLZO particles in the composite cathode. The XRD pattern of the composite cathode showed the LBS sol-gel coating did not affect the structure of the solid materials. The all-solid-state cell using the composite cathode coated LBS glass showed a higher discharge capacity and capacity retention compared with the cell with a composite cathode without LBS glass. Electrochemical Impedance spectroscopy was used to investigate the interface resistance of the batteries. The results indicated that the LBS coating reduced the cathode interfacial resistance, which can be the main reason for the observed battery performance enhancement.

As the looming depletion of natural resources and the emerging
demand for high power density devices as our technology advances,
supercapacitors, functioning as renewable energy generation and
storage devices are getting more and more attention.
Hollow carbon spheres has long been recognized to have various advantages, such
as high specific surface area, large controllable inner pore volume
and low specific density. These excellent properties make hollow
carbon spheres as a good candidate to be applied on
supercapacitors.
In this work, we present high specific performance
hollow carbon based supercapacitor produced by one-step simple
hydrothermal reaction. The Pluronic F127 is used as soft templates
and alpha-cyclodextrin (α-CD) as carbon precursor. By adjusting
the added weight of F127, i.e. 30, 60, and 120 mg and mixed them
with 60mg α-CD respectively, after hydrothermal for 6 hours at
200°C, different inner pore volume and carbon particle sizes can be
obtained. Relatively high specific capacitance can be observed for
all the samples by using 6M KOH as aqueous electrolyte, 191 F/g
under 1 A/g discharging current can be obtained.
Various characterizations have been conducted to undermine the factors
that affect the performance and the growing mechanism as well.
The last but not the least, another environmentally friendly carbon
precursor- D-Fructose is used to contrast how hollow cavity can help
the specific capacitance performance.
In conclusion, simple one-step hydrothermal reactions by tuning the weight of soft
templates, different inner pore volume and porosity distribution can
be achieved and result in high specific performance.

Lithium-ion batteries have applications ranging from portable electronics to electric vehicles. Graphite is currently used as a commercial anode in Li-ion batteries. However, due to its low gravimetric capacity (372 mAh/g) and volumetric capacity (~800 mAh/cm^3), a significant amount of materials and huge space is required to fabricate the battery. The materials that alloy and de-alloy with lithium have large gravimetric capacity which is 2-10 times greater than that of graphite. This may lead to an increase in the energy density of the battery, and, therefore, these materials are considered as possible candidates to replace graphite. The practical use of these materials is impeded by a huge volume change (200-370 %) during repeated cycling of the battery. The enormous volume expansion and contraction of the materials results in pulverization and cracking of the electrodes that leads to the loss of contact or detachment of materials from the current collector. This issue can be solved by using composite structures in which the active particles are embedded or dispersed in a carbon matrix. Mechanical ball milling is one of the suitable techniques to prepare such a composite, as it is inexpensive and large quantities of materials can be produced. Among the materials that alloy with lithium, antimony is chosen to prepare composites using a magneto-ball mill. Suitable amounts of antimony and graphite are loaded into a stainless steel vial along with four hardened steel balls and milled for 100 hours. Four different ball milling modes are used including two milling modes with an external magnet and other two without the magnet. The structure and morphology of the composite were investigated using x-ray diffraction, Raman spectroscopy and transmission electron microscopy. The structure of the composites varies depending on the ball milling mode used in the course of sample preparation. The optimal electrochemical performance is shown by the composite prepared using a milling mode with an external magnet. The electrochemical properties are dependent on the electrode thickness. In a thin electrode, electrochemical investigation reveals that the composite prepared with a magnet retains 550 mAh/g at a current rate of 230 mA/g even after 250 cycles. Furthermore, the composite is capable of retaining a capacity of ~400 mAh/g at a high current rate of 1.15 A/g, exceeding the theoretical capacity of graphite. Transmission electron microscope analysis demonstrates that the electrochemical stability originates from the structural characteristics of the nanocomposite, which contains Sb nanoparticles (about 5-15 nm in size) dispersed homogeneously in a carbon matrix.

To improve the efficiency of Li-Ion batteries, transition-metal fluorides have attracted much interest due to the possibility of a three-electron redox reaction giving capacities as high as 712 mAh g-1 for FeF3, much higher than generally used materials for the positive electrode (e.g. LiCoO2, LiFePO4)[1].
FeF3 may be synthesized by ball milling from solid precursors [2], in ionic liquid[3] or by the fluorolytic sol-gel approach[4,5]. The production of well-defined, narrow-sized fluoride nanoparticles in shorter time is important to obtain high-performance materials.
Here, we report a benzyl alcohol-assisted fluorolytic sol-gel route for the fabrication of electrochemically active iron fluoride nanoparticles and iron fluoride/RGO based nanostructures [6]. Iron fluoride sol formation involves the reaction of dehydrated Fe(NO3)3 9H2O in benzyl alcohol with a concentrated methanolic HF solution, following the fluorolytic sol-gel approach developed by Kemnitz et al.[4] 30 nm sized FeF3 0.33H2O nanocrystals are readily obtained upon microwave treatment at 150 °C for 10 minutes of the sol prepared in benzyl alcohol.
The electrochemical behavior, especially when the FeF3 0.33H2O nanoparticles are supported onto RGO, shows the presence of a relatively stable conversion reaction which allows high capacities to be delivered for the first few cycles (180 to 270 mAh g-1). After prolonged cycling only a stable Li+ insertion mechanism is observed. After the 50th cycle a value close to the full theoretical capacity can be delivered (150 mAh g-1, for the insertion mechanism only at around 3V vs Li+/Li), proving the suitability of the proposed approach.
References:
1. F. Badway, N. Pereira, F. Cosandey and G. G. Amatucci, J. Electrochem. Soc., 2003, 150, A1209-A1218.T. Li et al., J. Power Sources, 2012 , 217, 54
2. T. Li et al., J. Power Sources, 2012 , 217, 54
3. C. Li, L. Gu, S. Tsukimoto, P. A. v. Aken and J. Maier, Adv. Mater., 2010, 22, 3650-3654
4. E. Kemnitz, U. Gross, S. Rüdiger and C. S. Shekar, Angew. Chem. Int. Ed., 2003, 42, 4251-4254
5. Y. Guo, P. Gaczynski, K.-D. Becker and E. Kemnitz, ChemCatChem, 2013, 5, 2223-2232.
6. L. Di Carlo, D. E. Conte, E. Kemnitz, Chem. Comm. 2013, submitted

Recently, garnet-type Li7La3Zr2O12 solid electrolyte has attracted much attention because of its high ionic conductivity and its potential application in all-solid-state Li batteries [1-4]. However, the Li7La3Zr2O12 obtained via conventional solid-state method usually showed a limited density owing to poor contact between grains. High porosity in Li7La3Zr2O12 may cause a high grain-boundary resistance for Li-ion conduction and hence a poor ionic conductivity . In this work, highly densified Li7La3Zr2O12 solid electrolytes were successfully obtained by liquid-phase sintering and atmosphere sintering. During liquid-phase sintering by using Li2O as additive, the liquid phases formed between the grains could expel the residual pores and improve the ceramic density [5]. Sintered in a flowing oxygen atmosphere, the pores filled with oxygen could disappear easily by oxygen migration via lattice diffusion or vacancy transport, leading to a enhanced densification of ceramics [6]. All obtained Li7La3Zr2O12 solid electrolytes show a relatively high density of > 96% and a high ionic conductivity (~7×10-4 S/cm).
References
[1] Murugan R, Thangadurai V, Weppner W. Angew. Chem. Int. Ed., 2007, 46, 7778.
[2] Li Y, Wang CA, Xie H, Cheng J, Goodenough JB. Electrochem. Commun., 2011, 13, 1289.
[3] Rangasamy E, Wolfenstine J, Sakamoto J. Solid State Ionics, 2012, 206, 28.
[4] Huang M, Liu T, Deng YF, Geng HX, Shen Y, Lin YH, Nan CW. Solid State Ionics, 2012, 204-205, 41.
[5] Li YQ, Cao Y, Guo XX. Solid State Ionics, 2013, 253, 76.
[6] Li YQ, Wang Z, Li CL, Cao Y, Guo XX. J. Power Sources, 2014, 248, 642.

We report an innovative paradigm for design and synthesis of 3-D graphene/graphite structures with engineered high porosity by using Cu/Ni alloy foams as templates. The Cu/Ni alloy foams were obtained by electrodeposition of Cu on Ni foam scaffolds (feature size of 50 µm) followed by annealing at 1000°C and selective electrochemical etching of Cu. The as-obtained Cu/Ni alloy foams were highly porous with a feature size of 5 µm, ten times smaller than that of the original Ni scaffolds. By using such Cu/Ni foams as templates, 3-D graphene and graphite can be readily synthesized with replicated feature sizes of 5 µm in ethylene and at a temperature of only 600°C. The as-synthesized graphene/graphite foams exhibit excellent electrical conductivity as well as much higher specific surface areas than that of the state-of-the-art graphene/graphite foams. We further coated such materials with Ni(OH)2 and demonstrated high performance in the supercapacitor application.

Lithiation of silicon anodes in Li-ion batteries is a complex chemo-mechanical phenomenon, characterized by coupled diffusion, microstructural rearrangements, and large deformation, which operate over a wide range of spatial and temporal scales. Lithiation and delithiation can lead to failure after very few cycles, motivating the design of silicon anodes with a proper understanding of the underlying chemo-mechanics. Here, we propose a coupled chemo-mechanical continuum model, calibrated using available experimental data and computational data obtained using molecular dynamics simulations. In contrast to existing models, the mechanical component of the model takes into account deformation rate-dependence (or creep), which we believe is important, since typical operating temperatures are close to 0.8*Tm for lithium. The model is formulated using a consistent thermodynamic framework with two state variables. The first one is the concentration of lithium, and the second state variable is an order parameter which describes the specific free volume or a degree of amorphization. The chemical component of the model is based on a standard methodology for stress-assisted diffusion. The mathematical structure of the model lends itself to straightforward implementation within commercial finite element codes.

MX phase materials are multifunctional class materials, where M is an early transition metal and X is C or N and find application in various fields. Recently MX bulk phase materials were tried as anode material in Li ion batteries with encouraging results. In this study, we deposited Ti8C5 and TiC phases by reactive magnetron sputtering on copper substrates at room temperature by varying methane partial pressure during the process. Cubic Phase TiC films show a discharge capacity of 169 µAh cm-2µm-1 in a non-aqueous electrolyte containing a Li salt. There is a graded decrease in discharge capacity when cycled between 0.01 and 3.0 V. From XPS depth profile analysis, it is inferred that Li intercalated cubic phase TiC films consist of lithium compounds, hydroxyl groups, titanium sub oxides and cubic phase TiC. XPS and GIXRD depth profile revealed that lithium reactivity and diffusivity is limited to grain boundary volume in cubic phase TiC. Trigonal phase Ti8C5 shows double the discharge capacity of cubic TiC possibly due to enhanced diffusion of Lithium in grain boundary volume and layered lattice structure. The discharge capacity of cubic TiC at 50th cyle is 127 µAh cm-2µm-1.

The layered oxide compounds (1-x)LiMO2#9679;xLi2MnO3 (M= Ni, Mn, Co) are of great interest as positive electrode materials for high energy density lithium-ion batteries. In this work, we successfully prepared Li1.2Ni0.2Mn0.6O2 by co-precipitation method. The surface modification with “AlF3” was done by solution based reaction. After surface modification, the first cycle coulombic efficiency of Li1.2Ni0.2Mn0.6O2 improved from 82.7% to 87.5%. In addition, both the rate capacity and cycling capacity are also improved. In order to understand the improved electrochemical performances, the structure differences between pristine and surface modified Li1.2Ni0.2Mn0.6O2 after different electrochemical cycles were carried out with X-ray diffraction (XRD), neutron diffraction (ND), X-ray photoelectron spectroscopy (XPS) and aberration corrected scanning transmission electron microscopy (a-STEM) & electron energy loss spectroscopy (EELS). Electrochemical property measurements including potentiostatic intermittent titration technique (PITT), electrochemical impedance spectroscopy (EIS) are adopted. By using these powerful surface/bulk characterization techniques, the mechanism of improved electrochemical performance is revealed.

Due to a worldwide imperative of making use of renewable energy to solve finite fossil-fuel supplies and global warming problems, better energy storage systems must be developed to ensure a safe, reliable and high-efficient energy supply. To this end, Li-ion batteries have been targeted as the distinguished candidates for energy storage. Currently, we are focusing on one of the most interesting polyanionic cathode materials, epsilon-VOPO4. This material adopts a stable 3D tunneling structure with theoretical specific capacity of ~158 mAh/g (for LiVOPO4), as high as LiFePO4. More importantly, this material possesses a higher free energy of reaction, a higher conductivity, and a greater possibility of oxidation state variation than LiFePO4. It is known that for Li-ion batteries, high energy density can be achieved not only by increasing the operation voltage, but also by increasing the number of Li ion transferable per redox center. For VOPO4 materials, the most attractiveness is that we might intercalate up to two Li ions into the structure, which will yield a theoretical capacity of 316 mAh/g (for Li2VOPO4). Our previous studies have proved that epsilon-VOPO4 can allow more than one Li ion per redox center participating in the electrochemistry, and it is possible to cycle reversibly over hundreds of cycles. However, testing results do not yet assure the full utilization of the electrochemical potentialities of VOPO4 (the so-far-obtained reversible capacity is ~180 mAh/g, much lower than the theoretical capacity of 316 mAh/g for Li2VOPO4).
Can both two lithium ions participate in the electrochemistry and reach the full capacity of Li2VOPO4? Can Li2VOPO4 cathode be cycled reversibly and stably? What is the ultimate limit to this intercalation reaction? To answer these questions, we investigated in-situ and ex-situ synchrotron X-ray diffraction, neutron diffraction, X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and electrochemical behavior of epsilon-VOPO4. Based on these experiment results we provided more insight in the reaction mechanism, structure evolution process, as well as the fundamental intercalation limitation of this material upon cycling. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Basic Energy Sciences under Award Number DE-SC0001294.

Silicon is regarded as one of the most promising anode materials for next generation lithium-ion batteries. For use in practical applications, a Si electrode must have high capacity, long cycle life and high efficiency. A yolk-shell structure is a very promising structure to meet all these needs. The well-defined void space allows the Si particles to expand freely without breaking the outer shell, therefore stabilizing the solid-electrolyte interphase (SEI) on the shell surface. Beyond commonly used C shell, other conducting materials, such as Titanium nitride (TiN) and ploy(3,4-ehylenedioxythiophene) (PEDOT), were prepared to conformally wrap the Si nanoparticles with rationally designed void space. These conducting shells enhance the electrical conductivity of Si nanoparticles and provides a high stable SEI layer during the cycling, resulting in excellent electrochemical performances. Moreover, compared with commonly used amorphous C shell, TiN coating largely increases the first cycle Coulombic efficiency, which makes the structures promising for full cell application, because less cathode materials will be needed to compensate the initial Li loss at the anode.

We have developed a novel synthetic route to produce Mg2Si fine particles for an anode material of Li-ion battery with cyclability. Downsizing the diameter of the particles is believed to a key to maintaining the stable charge and discharge reactions on cycles. By conventional synthetic methods, however, Mg2Si fine particles with high quality have not been produced. In particular, the solution chemistry route, which is widely applied to the synthesis of oxides or noble metals, is not applicable in principle because it is impossible to reduce Mg2+ ions in a solution. Ball milling or mechanical alloying tends to give insufficient atomization effect or undesirous impurity inclusion. Very recently, two research groups reported that Mg2Si fine particles were obtained by microwave heating of ball-milled mixture of Mg and Si lumps or by the hydrogen-driven reaction of ball-milled mixture of MgH2 and Si powders. Even though, the inhibition of the surface oxidation or undesirous impurity formations, which directly affects to the performance of the battery, seems to be still challenging. Here, we show the novel synthetic route, using NaSi, MgCl2 and Na as starting materials, to prepare Mg2Si fine particles without undesired by-products. The mixtures of NaSi, MgCl2 and Na with various nominal compositions (~ 150 mg) were padded into BN crucibles. Then, each BN crucible was placed in a stainless steel cell (~ 10 cm3) in an Ar atmosphere and heated at 650 °C for 10 h. We found the condition of high yield Mg2Si formation without oxidation. The diameter of the prepared Mg2Si particles was less than 1 mu;m. It was suggested that the formation of Mg2Si fine particles was based on a metathesis reaction where the reaction of MgCl2 and Na formed Mg and NaCl, and then Mg reacted with NaSi to form Mg2Si. Because the melting temperatures of Mg, NaCl and NaSi are higher than 650 °C, any liquid phases, which induce a grain growth of Mg2Si, would not appear. The charge/discharge properties of the synthesized Mg2Si fine powders were evaluated using the electrode comprised of a mixture of the Mg2Si fine powders and carbon black (66.7/33.3 wt%). We used a Li foil as a counter/reference electrode and LiPF6 (1 M) dissolved in a mixture of ethylene carbonate/diethyl carbonate (50/50 vol%) as an electrolyte. A constant current of 100 mA/g was applied at a voltage window of 0.02 - 1.5 V (v.s. Li/Li+). As a reference, the charge/discharge properties of Mg2Si coarse particles (diameter < 53 mu;m) were evaluated in the same way. The initial discharge capacity of the synthesized Mg2Si fine powders was 740 mAh/g, which is more than twice as high as that of the conventional carbon and that of the commercial Mg2Si particles. For the Mg2Si fine powders, the capacity after 10 cycles retained 68 % of the initial capacity. The retention value is comparable to the highest value of 60 % reported for the Mg2Si powder prepared by the hydrogen-driven reaction of MgH2 and Si powders.

Olivine-phase lithium ion phosphate (LiFePO4) has been extensively studied as a promissing cathode of lithium ion battery used in high density power sources owing to its numerous appealing features, such as high theoretical capacity (170 mAh gminus;1), flat voltage profile, structure stability, low cost, abundant material supply and environmental benignity [1-3]. However, the main obstacle for the application of LFP is its poor high-rate performances due to the low electronic conductivity (~10minus;9 S cm-1) and low ionic diffusivity (10minus;13 to 10minus;16 cm2 sminus;1)[4-5]. In order to improve its electronic conductivity, LiFePO4 (LFP) modified by La0.6Sr0.4Co0.2Fe0.8O3minus;δ (LSCF) which has good electrical conductivity was studied in present research. The synthesis was as followings: firstly, LFP particles were synthesized by a hydrothermal method. Then these particles were modified with La0.6Sr0.4Co0.2Fe0.8O3minus;δ (LSCF) by a suspension mixing process. Finally the LSCF modified LFP particles were calcined in a reducing atmosphere (5%H2/Ar). The effects of LSCF modification were studied by X-ray diffraction(XRD), transmission electron microscopy (TEM), galvanostatic charge/discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The TEM results showed that LSCF particles were tightly enwrapped with the bare surface of LFP. X-ray diffraction results proved that the modified composite still retained the structure of the LiFePO4 substrate. Electrochemical test results indicated that LSCF modifying significantly improve the capacities at high charge/discharge rates. This improvement may be attributed to the lower charge transfer resistance and higher electronic conductivity.
Acknowledgements
The authors thank the project supported by Shanghai Science and Technology Commission(11nm0501600), and the Analysis and Research Center of Shanghai University for their technical supports.
Reference
1. A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, J. Electrochem. Soc. 144 (1997) 1188.
2. K. Amine, J. Liu, I. Belharouak, Electrochem. Commun. 7 (2005) 669.
3. Y.D. Li, S.X. Zhao, C.W. Nan, B.H. Li, J. Alloys Compd. 509 (2011) 957.
4. J. Lim, J. Gim, S. W. Kang, S. Baek, H. Jeong, and J. Kim, J. Electrochem. Soc., 159, A479 (2012).
5. A. V. Murugan, T. Muraliganth, and A. Manthiram, J. Phys. Chem. C, 112, (2008) 14665.
6. G. X. Wang, H. Liu, J. Liu, S. Z. Qiao, G. Q. MaxLu, P. Munroe, and H. Ahn, Adv. Mater., 22, (2010) 44.

The aspect of pseudocapacitance (C_p) in nanostructured electrochemical capacitors (ECs) has not received much attention in terms of substantially enhancing capacitance and energy density over a small voltage range. While most nanostructures are proposed for charge/energy storage due to their large surface area-to-volume ratio, which contributes to a large electrostatic/double layer capacitance (C_dl), focusing on C_p could lead to the long sought-after bridge between batteries and electrical capacitors. The large surface area of nanostructured electrodes is also involved in C_p and allows for the observation of enhanced peak currents (i_p) in voltammetric measurements. We present a new model to explain and understand such peak currents and the implications for high energy density storage coupled with rate capability. The model is based on ion motion by electric drift, wherein the leakage of electric field through the Helmholtz layer is considered to be the dominant force on the electrolyte ions. This new physical interpretation results in a much simpler derivation of the well-known Randles-Sevcik equation, which relates the electrical currents to the voltage scan rates and the electrolyte concentrations, assuming ion diffusion as the transport mechanism. We find that our model is consistent with experiment and follows established i_p dependencies of ion concentration and scan rate. A translation to an equivalent circuit model for C_p, involving the pseudocapacitance and the double layer capacitances, and relevance to a practical EC device will also be discussed. [1] H. Yamada and P. R. Bandaru, Appl. Phys. Lett. 102, 173113 (2013).

Lithium iron phosphate (LFP) based electrode has excellent cycleability, high safety, and good thermal stability, however it has low capacity and rate capabilities due to the low electrical conductivity and lithium ion diffusivity. Here, we wrapped functionalized carbon nanotubes (CNTs) on the surface of LFP particles in the presence of cationic surfactant-cetyl trimethylammonium bromide (CATB), to improve the electrical conductivity of LFP particles. The observation of scanning electron microscopy and thermogravimetric analysis confirmed that the CNTs were fully adsorbed on the surface of LFP particles by the electrostatic interaction between negatively charged, functionalized CNTs and positively charged LFP particles functionalized with cationic CTAB. The wrapping of CNTs on LFP particles enhances the electrical contact between particles, which leads to the formation of the electrical conducting pathways through the CNTs network within the electrode. CNTs wrapped LFP electrode exhibits higher cycle performance and rate capabilities than other LFP electrodes. Therefore, it is suggested that this approach can be beneficial for the application of lithium ion batteries with high energy density such as electrical vehicles and energy storage systems.

Supercapacitors, in particular lithium-ion (Li-ion) capacitor, have been considered as a perfect candidate for the energy source of electronic devices requiring high and short current and good tolerance for numerous charge and discharge cycles. Li-ion supercapacitors have the similarity to Li-ion battery in that they utilize Li-ions for electrochemical charge and discharge. However, their electrode materials are different from those of Li-ion battery, i.e., all-carbons are used as electrode materials in Li-ion supercapacitors. In this research, multi-layered carbon nanofibers were manufactured using a simple process (electrospinning and subsequent thermal treatment) and their capacitances were characterized to investigate a feasibility of developing flexible nanofiber Li-ion supercapacitors.
In this study, tri-layered carbon nanofibers consisting of concentrically electrode/separator/electrode layers were manufactured by electrospinning and carbonization process. Poly(acrylonitrile) was used as the precursor of carbon layers (core and outmost shell), while styrene-co-acrylonitrile and aluminum acetate dispersion was used for the middle layers (i.e., the second layer from the core). All precursors were dissolved in dimethylformaldehyde and provided into coaxial nozzles for triple-walled electrospinning. The electrospun nanofibers were carbonized into tri-layered carbon nanofibers, in which aluminum oxide layers were formed between carbon core and carbon shell. The morphological and structural characterizations and x-ray diffraction were carried out to investigate the triple structure of the carbon nanofibers and crystal structure of the constituent layers. Electrochemical characterizations were carried out by the cyclic voltammetry and galvanostatic charge-discharge. Detailed results will be presented at the Conference.

Microstructure evolution of Li2Fe0.5Mn0.5SiO4 during the delithiating/lithiating processes is investigated by the first-principles calculations in an attempt to understand the capacity fading phenomenon often observed in the lithium cathode materials containing Manganese. A cycle of delithiating/lithiating LixFe0.5Mn0.5SiO4 for x between 2.0 and 0.5 is completely reversible with a microstructure consisting of stable 4-coordination configurations, which are corner shared tetrahedrons, centered by Fe, Mn, and Si ions. The accompanied redox couples are Fe2+/Fe3+, Mn2+/Mn3+, Mn3+/Mn4+ for x from 2.0 to 1.5, then to 1.0, and finally to 0.5, respectively. When LixFe0.5Mn0.5SiO4 is over-delithiated to the sate x being not greater than 0.5, the delithiating/lithiating process is not reversible. The microstructure of the compound in this stage collapsed into 5-coordination configurations, which are one edge shared polyhedrons of Fe and Mn ions, with 4-coordination configurations of Si ions, leading to a substantial volume shrinkage and shape twist of crystal structure. The existence of energy barrier is attributed to the main reason of this irreversibility. The energy associated with the 5-coordination microstructures stays in the deeper valley of the formation energy surface. A portion of energy injected into the compound to extract out more than 1.5 Li ions is consumed to form additional bonds between O and Fe/Mn ions, and is not recoverable. Further extracting Li0.5Fe0.5Mn0.5SiO4 t0 x=0 is accompanied by the redox couple of O2-/Oγ- (γ is between 1 and 2).

Li1+w[NixCoyMnz]1-wO2 (x:y:z = 6:2:2), the nickel rich material cathode of lithium ion cells with high capacity over 170mAhg-1 were fabricated using BTR-graphite as negative electrodes to investigate the mechanism of 1 C at 8.6, 7.0 and 5.5V for overcharging characteristics at room temperature. Using a combination of X-ray diffraction (XRD) and first principles calculations, we explore the structural origin of the overcharge induced thermal instability of cathode materials, Li1+w[NixCoyMnz]1-wO2, and LiCoO2 which exhibit significant difference in thermal stabilities. At first, batteries which have 7~8 stacks were assembled and we could found general charge-discharge properties that increasing current density helped to increase the specific energy of the cell. However, as current density was increased, it was found that this had an unsatisfactory impact on life and safety. And including the nickel content of NCM622 materials also helped improve performance, but this came at the expense of safety and life. A very significant irreversible reaction was detected between 5.2~5.5V range during overcharging test. Detailed SEM (scanning electron microscope), EDS (energy dispersive spectroscope) and Raman analysis reveal a complex surface structure of the particles in each overcharged voltage step that was not previously detected by XRD. Heat capacity was accumulated very seriously at middle position of stacks in a pouch cell. Cathode active materials of NCM622 were founded on anode surface by melting of the separator. But these phenomena were not appeared at a surface of both side end of electrodes because the heat was released at the end surface of the pouch by air. Structural comparison indicates that both LiCoO2 and Li1+w[NixCoyMnz]1-wO2 particles consist of trigonal structures, R-3mH, while the overcharged electrodes consist of a similar coreshell-surface structure but a little bit different surface structure. The thermal instability of Li1+w[NixCoyMnz]1-wO2 can be attributed to the release of oxygen because of the rapid growth of the rock-salt-type structure on the surface during heating through the overcharging. In contrast, the surface structure of the overcharged Li1+w[NixCoyMnz]1-wO2 particles delays the oxygen-release reaction to a much higher temperature resulting in better stability. These results gave deep insight into the relationship between the local structural changes and the thermal stability of cathode materials, which is vital to the development of new cathode materials for the next generation of lithium-ion batteries.

Amorphous SiO_x nanoparticles were fabricated through the electrochemical liquid-liquid-solid process using room temperature ionic liquid dissolved SiCl₄ and liquid Ga electrode. Amorphous SiO_x nanoparticles of about 200 nm were successfully obtained and their physicochemical properties were characterized by SEM, TEM, XRD, and XPS. The electrochemical performances of amorphous SiO_x nanoparticles as an anode material for lithium ion battery will be also presented.

In recent years, transparent devices have attracted substantial attention. However, transparent batteries, a key component in fully integrated transparent devices, have not yet been reported. The key factor in obtaining a transparent LIB resides mainly in the preparation of the cathode material. LiMPO4 (M=Fe, Mn, Ni) has advantages of excellent structural and thermal stabilities, non-toxicity, low cost and excellent electrochemical properties. In this study, we describe for transparent olivine compound LiNiPO4 wide band gap cathode materials deposition on a transparent conducting oxide (TCO) substrate. The olivine compound LiNiPO4 thin film cathode materials were deposited by radio frequency (RF) magnetron sputtering. The crystalline phases of the thin films were confirmed by X-ray diffraction (XRD). The morphology of the thin films were observed by scanning electron microscope (SEM). Films were characterized by UV-VIS spectroscopy and atomic force microscope (AFM). Electrochemical properties were measured by electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV).

Reduced graphene oxides (rGOs) with various degree of graphitization were prepared from graphene oxides (GO) using various reduction routes. The resulting rGOs were investigated as lithium storage materials for lithium ion batteries. Various analytical techniques including XRD, XPS, TGA, TEM were employed to study the relationship between the degree of graphitization of rGOs and their lithium storage characteristics. Electrochemical tests combined with physicochemical characterization on the rGOs revealed that reversible capacity and rate capability of rGOs is highly dependent on the degree of graphitization of rGOs. In this presentation, key factors governing lithium storage characteristics of rGOs will be discussed in more detail.

Si nanocrystals embedded SiO_x nanoscomposites were investigated as high capacity anode materials for lithium-ion batteries. High resolution transmission electron microscopy with x-ray diffraction analysis revealed that Si nanocrystals with the size of about 5 nm were well dispersed in amorphous SiO_x matrix after heat treatment at 1200 °C under inert atmosphere. The electrochemical performances of these materials showed a reversible capacity of 950 mAh/g with stable capacity retention during 100 cycles. In this presentation, the electrochemical properties of Si/SiO_x nanocomposites such as cycle performance and rate capability will be discussed in more detail.

Supercapacitors are being widely used in conjugation with Li-ion batteries (LIB) and also as alternatives to LIBs in laptops, portable media players, power backup, hybrid electrical vehicles etc. Carbon based materials are being investigated for application in electrical double layer capacitors (EDLC) and these materials still suffer from relatively low specific capacitance values than the desirable range. Metal oxides/hydroxides are being separately investigated for application in pseudocapacitors, which suffer from a drawback of having a low operating potential window. However, metal oxides offer advantages of high energy density and relatively easy-cost effective synthesis. Among the various metal hydroxides investigated for application in pseudocapacitors Ni(OH)2 is perhaps the most promising candidate with high theoretical specific capacitance value (2082 F/g).
In this report, we have synthesized porous mesoscopic channeled nanoparticles of Ni(OH)2 and performed electrochemical measurement thereupon. We have obtained a high specific capacitance of 2144 F/g at the current density of 1 A/g from these electrochemical measurements. Since, Ni(OH)2 suffers from poor conductivity we added graphene forming Ni(OH)2-G composite with enhanced conductivity. The Ni(OH)2-G composite showed even higher electrochemical performance with a specific capacitance of 2830 F/g at the current density of 1 A/g. The Ni(OH)2-G composite also showed a better capacitance retention of 47% (1335 F/g) at a current density as high as 40 A/g when compared to Ni(OH)2 , which showed only 29% (618 F/g) retention.

For the development of future energy storage devices, the concept of the Li ion hybrid (LIH) capacitor has attracted increasing attention of researchers worldwide. It bridges the gap between the Li-ion battery and supercapacitor to power the electric and hybrid electric vehicles. LIH capacitor consists of Li-insertion type material(s) which act as the anode and high surface area carbon material as the electrical double layer cathode. Aqueous electrolyte based hybrid capacitor has a voltage window limitation due to the occurrence of water splitting at 1.23V and compatibility limitation of Li insertion materials. Therefore using organic electrolyte is more convenient in such systems. Several combinations of cathode (trigol reduced graphene, activated carbon, coconut shell derived carbon etc) and anode (TiO2-B, b-FeOOH, TiP2O7, LiCrTiO4, LiTi2(PO4)3 etc) materials have been studied to achieve the highest possible energy density. However, there is still need to enhance the energy density value for these devices in order to drive HEVs. In this work, we have synthesized a very high surface area microporous carbon (surface area 2730 m2/g) by pyrolyzing a zinc based metal organic framework (MOF-5) at 10000C for 8 hours and used it as cathode material with the combination of Li4Ti5O12 as the anode in a LIH capacitor configuration. During the carbonization process, ZnO formation takes place at lower temperature along with the carbonaceous material. At temperatures above 7500C, the reduction of ZnO to Zn takes place. At temperatures above 9080C (evaporation temperature of Zinc) Zn evaporates to form the synthesized high surface area porous carbon. In the half cell configuration (vs. Li) MOF derived carbon shows an EDLC type charge storage behavior with a specific capacitance value of 149 F/g. This specific capacitance value is comparable with some of the highest values reported recently in the literature and higher than the commercial activated carbon. In the full cell (Carbon/ Li4Ti5O12), the cell delivered a maximum energy density of 65W-h kg-1 which is already high enough to drive the HEV (7.3-8.3 Wh kg-1), but further enhancement of energy density is required to drive the PHEV (57 to 97 Whkg-1) and EV (min 150 Wh kg-1). The energy density is higher than the commercial activated carbon, and only MOF derived carbon based supercapacitor (symmetric configuration). Along with the high value, the cell demonstrates longer cycle life with more than 90% of capacitance retention after 10000 cycles.

The growing energy demand brought about by extensive requirement and use of different electronic devices have motivated researchers to pursue high performance advanced electrode materials for charge storage applications. Owing to its unique combined characteristics of high power density, superior pulse charge/discharge, long cycle life and environmental friendliness for use in portable systems and hybrid vehicles, the supercapacitor is easily the most attractive option among all the charge storage systems for these applications. Due to the low capacitance value of carbon based electric double layer capacitor (EDLC) materials, several pseudocapacitive materials have been studied with considerable interest. Different eco-friendly metal oxides, sulfides and nitrides with several types of nanostructures have been reported for the last few years in a concerted effort to improve the capacitive performance. Here we report a novel synthetic protocol that involves direct growth of ternary nickel cobalt sulfide (NiCo2S4) nanowires (NCS NWs) on a carbon fiber paper for high performance supercapacitor applications. NCS NWs were synthesized by wet chemical sulfurization of nickel cobalt oxide (NiCo2O4) nanowires (NCO NWs) using Na2S as a sulfurization agent. The synthesized NCS NWs have a hierarchical morphology, and a direct electrical contact with the porous, conducting and stable carbon fiber paper substrate. The material exhibits a maximum areal capacitance of 2.65 F/cm2 at a current density of 1mA/cm2 (which is around six times higher than that of NCO NWs) along with a high rate capability (40% capacitance retention at current of 40mA/cm2). We demonstrate and discuss the rich redox chemistry of the NCS NWs in comparison to its NCO counterpart.

Electrochemical energy storage devices are one of the promising device platforms for efficient utilization of energy. Li-ion batteries (LIB) and supercapacitors are the well-known existing technologies among them. A combination of EDLC and Li ion battery, called Li ion hybrid capacitor (Li-HEC), is expected to overcome the energy and power density limitations of supercapacitors and Li ion batteries. This new generation capacitors involve the charge storage mechanism of both double layer formations at cathode and Li intercalation at anode. Recently three dimensionally interconnected carbons with wide pore distribution have shown good promise for double layer formation. Here we report synthesis of 3D interconnected high surface area porous carbon (HSPC) with hierarchical pore distribution by single step pyrolysis of selected polymer without adding any external activation agent. HSPC was synthesised by pyrolysis of Poly(acrylamide-co-acrylic acid) potassium salt at 1000°C in the inert atmosphere. The interconnected porous morphology of HSPC was confirmed by FESEM. This HSPC showed a BET specific surface area of 1491m2/g. Major part of the surface area is seen to be contributed by pores having size in the range of 1-2nm. HSPC showed remarkable performance as cathode for Li ion hybrid capacitor. The hybrid capacitor measurements were performed with HSPC as the cathode material, Li4Ti5O12 as anode material and LiPF6 in EC:DMC mixture as the electrolyte. Cyclic voltammogram and charge discharge measurements were performed to evaluate the performance of HSPC. The HSPC based Li-HEC delivered the energy density of ~55 Whkg-1 which is much higher as compared to that obtained using other activated carbons. HSPC based Li-HEC showed good rate performance at higher current densities and cyclic stability of 85% retention after 2000 cycles.

Polyanion materials such as phosphates (LiMPO4, M = Fe, Mn), borates (LiMBO3, M = Fe, Mn, Co), and silicates (Li2MSiO4, M = Fe, Mn, Co) have received great attentions due to their inherent stability and high operation voltage windows. Amogest them silicates, especially Li2MnSiO4, are regarded as an attractive cathode material due to the possibility of achieving large theoretical capacity of ~330 mAh g-1 and two electron reactions. However, structural degradation resulting from Jahn-Teller distortion upon lithiation and delithiation and low electronic conductivity prohibits its practical use. Herein we prepare electrospun Li2MnSiO4 nanoparticles embedded carbon nanofibers (C-Li2MnSiO4 NFs) by using electrospinning method. During annealing process, carbonization and crystallization develop simultaneously, resulting in highly crystalline Li2MnSiO4 particles in carbon matrix. To confirm the 1D effect of nanofibers on electrochemical performance, the electrochemical properties of Li2MnSiO4 particles (Li2MnSiO4 NPs) and carbon coated Li2MnSiO4 nanoparticles (C-Li2MnSiO4 NPs) were also evaluated. C- Li2MnSiO4 NFs electrode shows much enhanced electrochemical performances including a high discharge capacity of ~ 200 mAh g-1 (0.05C) and the capacity retention of ~ 77 % over 20 cycles. These improved electrochemical performances are attributed to uniform carbon coating and one-dimensional (1D) properties related to lithium ion kinetics.

Nano-structured silicon is promising for high capacity electrodes of Li ion batteries. The charge-discharge capacity of silicon is an order of magnitude higher than that of conventional graphite anode. However fully lithiated silicon has been reported to cause fracture and pulverization of the electrode, thereby leading to capacity degradation and failure of the battery cells. Here we compare three kinds of Si nanoparticle composite anode for Li ion batteries.
Our lithium ion batteries cells have a lithium cathode and an anode. We employed three kinds of the anode materials consisted of Si and C. One was mixture of Si nanoparticles and C nanoparticles (1:1), another was Si nanoparticles, and the other was Si/SiC coreshell nanoparticles. Si/SiC coreshell nanoparticles were produced by the double multi-hollow discharges plasma CVD method. SiH4 gas with a flow rate of 2sccm, diluted with H2 with a flow rate of 448sccm. Si nanoparticles were nucleated, grown in H2 + SiH4 plasma, and transported downstream by gas flow. CHx radicals for carbonization was produced by the CH4 multi-hollow discharge. Si/SiC core-shell nanoparticles were produced at 5 Torr. The electrolyte was 1M LiPF6 in ethylene carbonate (EC)/ dimethylene carbonate (DMC) (1:2). For the measurements of anode property, a Li metal sheet of 1mm thickness was used as a cathode. Li intercalation capacity was measured by applying a constant current of 0.1 mA/mg.
The best charge-discharge characteristic of Li ion battery in this study was obtained using Si/SiC coreshell nanoparticle anode. The charge capacity is 3000mAh/g, which is 1.5 and 9 times higher than that of anode of mixture of Si nanoparticles and C nanoparticles and conventional graphite anode. Li ion battery with Si/SiC coreshell nanoparticle anode produced by plasma CVD also shows better capacity maintenance ratio of 91%. Thus SiC/Si coreshell nanoparticle anode is promising for next generation Li ion batteries.
Acknowledgements
This work was partly supported by MEXT, JSPS, Fukuoka IST, and P&P of Kyushu University.

Here we propose a new route to smart interface for all-solid-state lithium ion batteries (LIBs). Direct formation of electrode active materials/ Li ion conductive glass heterojunction was performed through a molten salt using crystal growth method. We used Li-B-Si-O system glass as a molten salt for LiCoO2, LiMn2O4, and Li4Ti5O12 crystals growth. High-quality idiomorphic crystals can be grown in the Li-B-Si-O system glass matrix. HR-TEM observation coupled with EDX-based elemental analysis revealed that the interfaces between the crystals and the glass matrixes were well-connected without impurely phase formation. We expect the direct formation of the hetero-junction reduce its interfacial resistance for lithium ion transportation during all-solid-state LIBs operation as well as prevent their direct contact with the electrolyte solution, suppress the phase transitions, improve the structural stability, and decrease the disorder of cations in the crystal sites for conventionally used LIBs operation. Furthermore, we performed the LiCoO2/Li-B-Si-O, Li4Ti5O12/Li-B-Si-O composites could be easily integrated with Li7La3Zr2O12 ceramics sheet without no byproducts at the interface by hot pressing. The all-solid-state LIBs using a double layer consisting of the LiCoO2/Li-B-Si-O composite with the Li7La3Zr2O12 sheet with 350 µm thick exhibited charge-discharge performances. This result is believed to be due to the efficient lithium-ion transport at the interface with the strong contribution of Li-B-Si-O system glass as a binder.

Electric double layer capacitors, or supercapacitors, have demonstrated significant promise in emerging standalone energy modules, hybrid systems, and grid-level storage. Although porous carbon electrode materials, such as activated and carbide-derived carbons (CDCs), exhibit high surface area and yield high gravimetric capacitance, they feature poorly conductive pore walls composed of amorphous or disordered graphitic carbon and are therefore unable to provide good rate handling. Furthermore, the effects of different functional groups terminating carbon surface on pore wetting and electrolyte stability are not completely understood. We conducted various thermal annealing and chemical modifications of CDC derived from 0.02 - 2.0 µm TiC and SiC particles and synthesized in the 600-1000°C range. While we retain a consistent pore structure matching the diameters of electrosorbed ions, we modify the accessible surface area, pore volume, and mesoporosity as a factor of initial material properties and subsequent treatment conditions. Vacuum annealing in the 700-1600°C range at 10^-6 torr strips the surface of functional groups and increases the size of ordered sp²-bonded domains on the pore surfaces. Using air oxidation, NH₃ annealing, and oxidation in H₂SO₄/HNO₃, we introduce -OH, =O, -COOH, and quaternary nitrogen/NH₂ surface groups. Depending on the surface functionalization and degree of graphitization, we change the charge storage density and mobility of electrolytes including tetraethylammonium tetrafluoroborate (in acetonitrile) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Key electrochemical performance metrics, such as rate handling and ionic resistance, are shown to vary depending on the surface chemistry and resulting pore wall hydrophobicity. We show that the introduction of surface groups as dopant-like defects affects the electron density of states in graphitic carbon and subsequently changes ion screening and packing in confined pores, and rate handling and power densities are affected as a result. By comparing these materials with similarly modified exohedral onion-like carbons, we show the effects of ion confinement in pores. We show the trade-offs between carbon structure, surface chemistry and ion mobility and electrolyte stability, suggesting pathways to science-based design of high-performance carbon electrode materials.

Graphene oxide (GO) has been of particular interest because it provides unique properties due to its high surface area, chemical functionality and ease of mass production. GO is produced by chemical exfoliation of graphite and is decorated with oxygen-containing groups such as phenol hydroxyl, epoxide groups and ionizable carboxylic acid groups. Due to the presence of those functional groups, GO can be utilized as a novel platform for hybrid nanocomposites in chemical synthetic approaches. In this work, GO-SnO2 nanocomposites have been prepared through the spontaneous formation of molecular hybrids. When SnO2 precursor solution and GO suspension were simply mixed, Sn2+ was spontaneously formed into SnO2 nanoparticles upon the deoxygenation of GO. Through further chemical reduction by adding hydrazine, reduced GO-SnO2 hybrid was finally created. Our investigation for the electrocapacitive properties of hybrid electrode showed the enhanced performance (389 F/g), compared with rGO-only electrode (241 F/g). Our approach offers a scalable, robust synthetic route to prepare graphene-based nanocomposites for supercapacitor electrode via spontaneous hybridization.

Electrochemical impedance spectroscopy (EIS) is ideal for investigating the performance limiting factors or ageing behavior of lithium-ion batteries. However, the evaluation of impedance spectra is not always straightforward because of a rather complex response originating from electrode microstructures with distributed parameters or interactions between electrode microstructure and processes with a similar time constant. Thereby, the development of an appropriate impedance model and the evaluation of its suitability remain ambiguous. However, this step is of crucial importance to obtain physically meaningful conclusions from impedance analysis.
This study shows for a graphite anode, that the distribution function of relaxation times (DRT) [1,2] is supportive for proposing a well-suited and physical based impedance model. A comparison of different models, their effect on the fitting result and a final evaluation of their physical suitability are introduced. Beside serial impedance models, also transmission line models (TLM) [3] are applied, which describe interactions between electrode microstructure and charge transport or charge transfer processes more properly. Microstructure parameters, such as porosity and tortuosity, give valuable information for the model parameterization [4]. This study shows that the best suited model should meet two criteria: (1) superior fit quality and, even more important, (2) the ability to represent parameter dependencies correctly. By application of the best suited model, which turned out to be a transmission line model, the contributions of (i) contact resistance, (ii) transport through the solid electrolyte interphase (SEI), (iii) charge transfer resistance and (iv) solid state diffusion were assessed quantitatively and physical parameters as activation energies and ionic conductivity in the pores were determined.
[1] H. Schichlein, A.C. Müller, M. Voigts, A. Krügel, E. Ivers-Tiffée, J. Appl. Electrochem. 32 (2002) 875-882.
[2] J. Illig, M. Ender, T. Chrobak, J.P. Schmidt, D. Klotz, E. Ivers-Tiffée, J. Electrochem. Soc. 159 (2012) A952-A960.
[3] J. Bisquert, J. Phys. Chem. 106 ( 2002), 325-333
[4] M. Ender, J. Joos, T. Carraro, E. Ivers-Tiffée, J. Electrochem. Soc. 159 (2012) A972-A980.

Silicon is considered as one of the most promising anode materials for future lithium ion batteries, due to its high theoretical capacity. It is known that the lithiation of crystal silicon typically involves huge volume expansion, plastic flow of material, phase transformation from crystal to amorphous, and mass diffusion of lithium ions. In-situ TEM experiments and some first principle simulations revealed the anisotropic migration of the sharp interface during this process. However, it remains unclear in a global scale how this anisotropic interface mobility influences the fracture/degradation behavior. Based upon an orientation-dependent solid-solid reaction assumption, we have developed a three dimensional continuum model to describe anisotropic interface motion, and implemented through commercial finite element package to simulate the concurrent anisotropic interface motion and large plastic flowing. Our exemplary results on circular nanowires and spherical nano particles successfully captured the features observed in experiments on the same subjects and provided insight into anisotropic facture/degradation behavior. Based on these simulations, a new principle for geometry design of silicon electrode was proposed and benefits were demonstrated on both 2D and 3D nanostructures.

Next-generation energy storage materials must simultaneously satisfy a number of criteria: excellent charge and ion transport, high capacity, and reversible charge transfer. Electron- and ion-conducting polymers are often explored as additives in cathodes such as V₂O₅, LiCoO₂, LiFePO₄, etc. to form hybrid electrodes. Unfortunately, it remains extremely difficult to obtain a hybrid electrode that successfully balances electron and ion transport with charge transfer because of large-scale phase separation and poor structure control among the electrode&’s various components. Here, we show that hybrid electrodes comprised of multi-functional block copolymer and inorganic V₂O₅ exhibit good electon and ion transport, high energy storage capacity, and flexibility. Poly(3-hexylthiophene) - block - poly(ethylene oxide) (P3HT - b -PEO) block copolymers provide good electron and ion conductivity and act as a nanostructured binder for V₂O₅ crystals, which exhibit high electrochemical capacity. P3HT - b -PEO are synthesized in a two step method using externally initiated Grignard Metathesis Polymerizaiton followed by “click” coupling. The composite materials are fabricated in water to create block copolymer/ V₂O₅ xerogel hybrid electrodes. Fabricated electrodes of pure materials and composites were tested for capacity and cycling in both 2 and 3-electrode cell configurations, and composite materials exhibited capacities of 120 mAh/g and an energy density of 440mWh/g, similar to the values for pure V₂O₅.

Here we are reporting the synthesis and properties of Cu nanoparticle loaded carbonized wood electrodes for application in electrochemical supercapacitors. The Cu nanoparticle/carbonized wood electrodes were fabricated by reducing the Cu(NO3)2 in the wood at 800°C under the N2 atmosphere. The X-ray diffraction (XRD) measurements confirmed the formation of cubic Cu in the wood electrode. The average size of Cu nanoparticles was determined from the broadening of the XRD peaks using Scherer formula. The morphology of the samples was examined by scanning electron microscopy (SEM) which showed the Cu nanoparticles were anchored uniformly on the surface and deep within the pores of the electrode. The cyclic voltammetry measurements showed the electrode has a typical pseudocapacitor behavior with two redox reaction peaks at -0.16V and -0.4V. The reversible oxidation of Cu into Cu2O and CuO was verified by performing X-ray photoelectron spectroscopy (XPS) at different stages of charge discharge cycle. The charge-discharge curves indicated the formation of an electrochemical double layer at low potential and a redox charge transformation at higher potential. An ultra-high specific capacitance of 400 F/g was observed by discharging the electrode at 0.2A/g in a 2M KOH electrolyte solution. Additionally, the Cu nanoparticle/wood electrode exhibited excellent cyclability, with 99% of the specific capacitance being retained even after 2000 cycles. These remarkable results demonstrate the potential for Cu/wood as cheap and high performance electrodes for supercapacitor applications.

Li-ion battery (LIB) has been widely used in the past 2 decades, due to its higher energy density and cycling ability compared with other rechargeable battery system.
Graphite, as traditional anode material for LIB, has a theoretical capacity of 372 mAh/g, which cannot afford the demands from fast development of electronic devices. Therefore, more and more attention has been paid to Si and Ge material for their much higher capacity, 4200 mAh/g and 1620 mAh/g, respectively. However those two materials share a common drawback, expansion, which will result in electronic disconnection and capacity fading. Recently, we have demonstrated that Nano scale Multi-layer structure can effectively reduce the capacity fading. In situ X-ray reflectivity has been applied to study the reversible ability of Ge/Ti. From the back and forth shift of Bragg peak, we conformed that Ge in multi-layer structure can keep original structure and electronic connecting during charging and discharging. Coin cell battery test also gave a support to this result.
Spinel LiMn2O4, a 3D cathode material, was discovered 30 years ago by Thackeray etc. Compared with widely used LiCoO2 cathode, LiMn2O4 is cheaper and environmental friendly. This promising cathode material undergoes the problem of Mn-ion dissolving and structure distortion, which shall cause severe capacity fading and safety problems. Currently, we have synthesized high quality of epitaxial LiMn2O4 thin film with and without TiN buffer by sputtering and PLD methods. Those films can be used for future research, such as in situ study of surface change during cycling, Mn-ion dissolution and precipitation, phase transition etc.

TiO₂ has recently emerged as a potential material for use as anodes for lithium ion batteries owing to its low cost, abundance and high chemical stability. There has been considerable interest in nanostructured thin films for this application since they offer higher surface area and thus better performance compared to bulk films. However, morphology of the nanostructure has not yet been co-related to the performance of the battery. Also, current fabrication methods consist of multiple steps involving the use of carbon as conducting material and binders for adhering the active material to the current collector substrate. These, in addition to increasing the cost of fabrication, also pose a safety concern for high rate applications.
In this study, we present the fabrication of TiO₂ nanostructures using a single step gas phase method directly on the current collector. Aerosol Chemical Vapor Deposition (ACVD) process has been successfully used for single step synthesis of nanostructures of TiO₂ with different morphologies by controlling the aerosol dynamics in the process. One dimensional (columnar) single crystal TiO₂ nanostructures were synthesized on stainless steel substrates (current collector) by the ACVD process. The electrochemical performance of these nanostructures was tested in a half-cell assembly against Li/Li⁺.
Cyclic voltammetry curve of the single crystal columnar TiO₂ nanostructures shows an oxidation peak at 2.1V and a reduction peak at 1.7V. The first discharge and charge characteristics of the columnar nanostructures with a column height of 2.5 mu;m were found to be 198 mA h g^-1 and 155 mA h g^-1 at a current density of 100 mA g^-1. Optimization of the column height for the charge discharge capacity and the coulombic efficiency was carried out. This was also compared to different morphologies (dense and granular) synthesized by the ACVD process. Mass transfer characteristics of the different morphologies were studied using electrochemical impedance spectroscopy (EIS) and Galvanic Intermittent Titration Technique (GITT). The co-relation of nanostructure with the mass transfer characteristics and the performance will be presented.

Silicon (Si) is one of the most promising anode materials for lithium ion batteries mainly due to its high theoretical capacity, which is more than ten times higher than that of graphite. In Si electrodes, active materials are normally mixed with nonconductive polymer binders and conductive additives to maintain the electrical and mechanical integrity. However, the incompatibility between polymer binders with conductive additives often leads to low cycling stabilities due to the mechanical failure caused by large volumetric changes of Si during the cycling process. Here we have designed and synthesized a class of new conductive polymers binders by synergistically incorporating different desired functions into a single structure.. The designed conductive polymer binders exhibit high conductivity, high binding strength to Si particles and good mechanical properties. As a result, electrodes made from Si particles and these conductive polymer binders show high capacity and good cycling stability. This work demonstrated an effective design strategy towards stable Si electrodes, which may be extended to fabricate other high capacity electrodes having similar structure changes during cycling.

We demonstrate a new method of manufacturing highly controllable TiO₂ electrodes for lithium ion battery applications based on ALD coating of porous metal foams. In contrast to conventional electrode preparation techniques based on casting a mixture of titania nanoparticles, a conducting additive and a polymer binder, our technique allows us to independently control the electrode pore size, active material thickness and phase of the active material.
Nanoporous gold (np Au) foams were prepared by free corrosion and then coated with titania as the active electrode material. The structure of the np Au determines the morphology and pore size of the active material and also acts as the current collector. The pore size can be tuned to the desired value in a range of 75 nm to about 2 µm by heat-treatment of the as-prepared nanoporous gold before coating the active material. The heat treatment does not change the overall structure of the template with narrow distribution of pore size and ligament width, allowing us to prepare electrodes with different, well defined pore sizes.
Atomic Layer Deposition (ALD) is used to achieve a homogeneous coating of the active material (TiO₂) on the np Au. The coating thickness can be controlled by the number of ALD cycles in a wide range from single layer up to almost complete filling of the pores. The as-deposited titania is amorphous and can be converted to anatase phase by heat treatment without changing the pore size of the sample.
We systematically studied the influence of pore size, coating thickness and phase on the electrochemical performance of our titania coated np Au electrodes. Our electrodes achieve high rate performance and show excellent cycling stability with high coulombic efficiency and no capacity loss, even after 500 cycles at 10C rate.
Work at LLNL was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

Lix[Ni0.33Mn0.67]O2 cathode materials with different secondary particle size were prepared via a carbonate co-precipitation method. Spherical morphologies with mono-dispersed powders (7.1 mu;m, 10.2 mu;m, 12.1 mu;m, 14.4 mu;m and 16.7 mu;m in average secondary particle size) were observed by scanning electron microscopy and particle size analysis. These lithium- and manganese-rich cathode materials can deliver a high initial discharge capacity of about 250 mAh/g-1 (2.0-4.7 V, C/10) regardless of their secondary particle sizes. However, smaller secondary particle size of Lix[Ni0.33Mn0.67]O2 (x=1.38) shows a better rate capability in high C-rate due to the reduced Li+ diffusion path inside cathode particle. For these cathode materials, their tap densities are not changed based on their average secondary particle sizes because of their sphericity. If the particles are not spherical, its tap density decreases from 1.7 g/cc to 0.8 g/cc even though their average secondary particle sizes are similar. To get higher tap density, mixing of 16.7 mu;m-size particles (80wt%) and 7.1 mu;m-size particles (20wt%) was carried out which led to the tap density of 1.9 g/cc. The results here indicate that secondary particle shape has a greater effect on tap density than secondary particle size for the mono-dispersed material at the range between 7 and 17 mu;m. And the spherical poly-dispersed material shows the increased tap density by more than 10%.
As an another lithium- and manganese-rich cathode material, spherical Lix[Ni0.15Co0.17M n0.68]O2 (x=1.47) was prepared with the average secondary particle size of 6.7 mu;m to maximize electrochemical performance and tap density using a carbonate co-precipitation method. This material shows a very high initial discharge capacity of 292 mAh/g-1 (2.0-4.7 V, C/20) and a tap density of 1.82 g/cc. The effect of lithium ratio of Lix[Ni0.15Co0.17M n0.68]O2 was investigated to maximize cycle life and their morphologies of primary and secondary particles were observed by scanning electron microscopy.

Nowadays a huge amount of attention is being devoted to alternative sources of energy, able to supply our also growing necessities. Maybe it is possible to consider the solar energy as the cleanest and with less impact on nature. For the daily use of this energy, however, many aspects must have their efficiency and yield improved.
In our research for this kind of development, we end up finding in nature maybe the more efficient system known up to date. Photosynthetic complexes can reach efficiencies larger than 98%, very often bordering the unity. More than that, they work on room temperature and are subjected to the weather conditions.
The photosynthetic complexes are basically composed of three parts: a light harvesting system, a channel that guides the collected energy until the reaction center and the reaction center, which, in turns, is responsible for the energy storing in the form of chemical energy.
By the last years it has been seen from spectroscopic data that the reason why these mesoscopic complexes are so efficient relies on quantum correlations, highlighting the quantum entanglement, that carry out the dynamics of the excitons from the harvesting sector, to the reaction center through the channel. However, how the quantum entanglement can survive on such intricate systems and that such big chaotic dynamics is still obscure. Also in the last few years it has been seen that instead of destroying the quantum correlations, the environment can protect and even generate then.
Noting that the systems can be modelled as harmonic oscillators immersed in a thermal field, we show that when the coupling is linear we are not succeeded in generating the quantum entanglement between the different sites. More than that, we point out and work on a completely general coupling. The field representing the external reservoir must be notoriously classical, once the environment of the photosynthetic complex is, in the last instance, classical. Actually we are dealing with a cell of a photosynthetic bacteria or a leave. We also note that our model can be extended to any bosonic modes in place of the harmonic oscillators, what is important for other transport of energy devices. The field is temporally stochastic and, following the nowadays technologies needs, all the evolutions occur in on a complete general non-Markovian regime, where the memory effects are included.
Finally, once this model reproduces the real case with a very high fidelity and generality, by means of mastering the high efficient evolution of the transport of energy we will be able to extend it to several transport of energy devices, highlighting the solar cells. It will be possible to propose solid-state systems as spin chains and nanostructured compounds that guide, as a channel, the excitation arising from the solar light to a chemical storage set up, that reply nature's giant efficiency.

Transition metal oxides (TMO), with their very large pseudocapacitance effect, hold promise for next generation high-energy-density electrochemical capacitors (EC). However, the typically very high resistance of TMO restricts the reported pseudocapacitors working at very low frequency with the typical cyclic voltammetry (CV) measurement limited to ~ 1 V/s. Here, we report a novel vanadium oxides core/shell nanostructure based electrode design to overcome the resistance challenge of TMO for rapid EC design. Quasi-metallic V2O3 nanoscale cores are dispersed on chemically-derived reduced graphene oxide (RGO) flakes for electric connection of the whole structure, while a naturally formed VO2 and V2O5 (called as VOx) thin shell around the V2O3 core act as active pseudocapacitive material. The composite is further thermally processed in hydrogen ambient. With such a composite as electrode material, we demonstrate EC with CV scan up to 100V/s, suggesting the EC can work at rapid frequency, attributed to the largely reduced resistance resulting from the synergistic effects of nanocomposites and hydrogenation process. The specific capacitance of the supercapacitor based on the hydrogen treated composite can achieve 518 F/g, which is much higher than 230 F/g of the untreated one.

Li batteries are currently emerging into automotive applications. Unlike conventional application areas, batteries for automotive applications experience very fast discharge rates (during acceleration) that leads to rapid decrese of capacity. Development of reliable and long-lasting batteries for energy-intensive applications requires comprehensive understanding of the degradation mechanisms of battery electrodes. Recently, Kelvin Probe Force Microscopy (KPFM) was used to study localized electronic states of battery electrode materials [1, 2]. Electronic structure of battery materials is obviously related to both charge and ageing states, hence KPFM could bring significant information about degradation mechanisms. However, only few studies have been published so far.
In present work, we studied LiMn₂O ₄ cathodes of commercial batteries at different states of charge and degradation by means of KPFM. In order to quantify the surface potential data, we measured KPFM response on LiMn₂O₄ particles and the Al current collector simultaneously and used the Al work function as a reference. We determined the shift of a surface potential of the LiMn₂O₄ at different states of charge and degradation and related it to the Li concentration. We also observed a variation of the surface potential within the same LiMn₂O₄ particles that suggests not uniform delithiation/degradation.
This research was supported by the European project laquo;Nanomotionraquo; (FP7-People-2011-ITN-290158).
1. Shrikant C. Nagpure, Bharat Bhushan, S.S. Babu, laquo;Surface potential measurement of aged Li-ion batteries using Kelvin probe microscopyraquo;, J. Power Sources 196, 1508-1512, 2011
2. Jing Zhu, Kaiyang Zeng, and Li Lu, laquo;In-situ nanoscale mapping of surface potential in all-solid-state thin film Li-ion battery using Kelvin probe force microscopyraquo;, J/ Appl. Phys. 111, 063723, 2012.

Carbon Aerogels (CAs) are potential candidates for supercapacitor electrode materials due to their unique properties such as high specific surface area (SSA) up to ~1000 m²/g, controllable interconnected 3D-porosity, good electrical conductivity and longer cycle stability. CAs are commonly prepared through a sol-gel polycondensation of resorcinol (R) with formaldehyde (F) and water by using Na₂CO₃ catalyst. The synthesis involves four steps: sol-gel formation, solvent exchange, supercritical drying, and pyrolysis. However, supercritical drying approach is more expensive than ambient drying and requires complex machinery. Therefore, recent efforts have been focused on synthesis of CAs via ambient pressure or subcritical drying conditions.
In contrast to conventional supercritical approaches, our work is focused on comparison of morphological and electrochemical properties of CAs synthesized in presence of (NH₄)₂CO₃ catalyst and dried at ambient pressure and in supercritical conditions. Organic gels (OGs) were formed by polymerization of resorcinol and formaldehyde with varying amounts of distilled water (0.883g in Gel1, 2.8937g in Gel2 and 4.904g in Gel3 respectively) using NH₄CO₃ catalyst. The first group of organic gels formed after polymerization was dried in ambient conditions for two days followed by pyrolysis at 900^oC in inert (N₂) gas. The second set of OG samples was prepared by supercritical drying in liquid CO₂ (at1500 PSI and 40oC) after exchanging water with acetone, followed by pyrolysis at 900^oC in N₂ atmosphere for 2 hours.
Preliminary nitrogen adsorption-desorption measurements indicated that all three CA samples dried at ambient conditions have high microporosity and Langmuir type of monolayer adsorption isotherms. However, SSA of the materials decreases with amount of water content. BET analysis, SEM and TEM data will be presented for understanding the differences implied by supercritical vs. ambient drying. The electrochemical properties of the cells assembled in symmetric CR2023 coin cell supercapacitor geometry will be discussed in terms of cyclic voltammetry, galvanostatic charging-discharging, electrochemical impedance and durability tests. The structure dependent electrochemical properties such as specific capacitance, energy density, power density and cycle stability in aqueous and organic electrolytes will also be discussed.

Electrical energy storage is central to energy strategies to harness the full potential of alternative energy sources, which often requires tailoring the electrode-electrolyte interactions to optimize the performance of storage devices. Fundamental gaps still exist in our understanding of the atomic- and molecular-level processes at the interfaces of in these storage devices, which determine their operation and affect their performance. Herein we describe the interactions between ionic liquid (IL) electrolytes, such as N-methyl N-octyl piperidinium bromide, N-methyl N-octyl pyrrolidinium bromide, N-methyl N-octyl piperidinium trifluoromethane sulfonate, or N methyl N octyl pyrrolidinium trifluoromethane sulfonate, and reduced graphite oxide (rGO) (commonly employed as an electrode material in electrochemical double-layer capacitors) in GO-IL composites.
To develop a detailed understanding of the interface between rGO and the ILs, we use in situ IR spectroscopy to study the structural and chemical changes in these various rGO-IL composites. To further evaluate the possibility of such rGO composites as electrode materials, we also study the thermal stability, the extent of exfoliation (including interlayer chemical interactions) and the chemical stability of the composites using powder XRD and TGA. Contact angle measurements are also performed to monitor the surface wettability of the synthesized GO-IL composites. The carbon recovered after immersion in pyrrolidinium Bromide has a d-spacing of 14.3 Å (a 6.3 Å increase from the original d-spacing of -8.0 Å) while in piperidinium bromide the increase is only 3.3 Å. The electrostatic interaction is therefore stronger between the N-methyl N-octyl pyrrolidinium cation of the IL and the electronegative oxygen groups of GO than for N-methyl N-octyl piperidinium cations, due to the stronger electrostatic screening of the former. We find that both cation-anion interactions and the ILs&’ molecular volumes constitute the key factors that determined the crystallographic orientation and the extent of IL intercalation. However, bromide anions do not significantly contribute to thermal exfoliation. Indeed, there is no chemical functionalization in bromide-intercalated GO-IL composites, in contrast to TFMS that foster covalent functionalization of GO. Anion interaction is therefore another factor to tailor the chemical functionality. Annealing in GO-pyrrolidinium Br at 150°C results in thermal exfoliation while crystallographic orientation of GO-piperidinium Br does not change significantly. Strong interlayer interactions are therefore present in rGO-pyrrolidinium Br as bromide anions reduce the chemical stability of the composite more than TFMS anions.
*The initial research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC001951, and the more recent work by NSF-CHE-1300180.

Ternary Metal Fluorides as New Cathodes of Rechargeable Lithium Batteries with Ultrahigh Energy Density
Sung-Wook Kim, Liping Wang, Dong Su, Jason Graetz, and Feng Wang
Brookhaven National Laboratory, Upton, NY 11973, USA; [email protected]
Some of transition metal fluorides (MFx) have been shown promising for use as high-capacity cathodes in rechargeable Li-ion batteries for large-scale applications, such as electric vehicles and grid-scale storage, but energy-efficiency and kinetics related issues remain a major hurdle to their commercial use. Cu based fluorides, such as CuF2 or the composites are particularly attractive due to the 3.55 V redox potential and extraordinarily high specific energy (1874 Wh/kg), but due to the irreversibility of Cu redox they were used only in primary batteries. Novel ternary metal fluorides M1yM21-yFx (M1, M2 = transition metal, 0 le; y le; 1), of varying metal species and stoichiometry, were synthesized by cost-effective mechanochemical process. Due to incorporation of a second cation in the same lattice, this composite system exhibits exceptional electrochemical properties, shown as significantly reduced 1st discharge polarization, cycling hysteresis and faster reaction kinetics than the binary metal counterparts. And strikingly high reversibility of Cu redox (Cu2+/Cu0) was found in the CuyFe1-yF2 system by electrochemical measurements along with confirmation via x-ray absorption spectroscopy. The results from this study demonstrated, for the 1st time, the feasibility of using Cu-based reversible conversion cathodes that will provide 3 times higher energy density than conventional intercalation cathodes.
The Li storage/release mechanisms and limits to cycling stability of CuyFe1-yF2 were investigated by combining electrochemical measurement with comprehensive structural and chemical analysis using in-situ X-ray absorption spectroscopy, X-ray diffraction, and transmission electron microscopy-electron energy loss spectroscopy (TEM-EELS). The lithium reaction process is much more complicated in CuyFe1-yF2 than the binary metal counterparts (i.e. FeF2, CuF2)[1, 2]. Some of the recent results on synthesis, structural and electrochemical characterization of ternary metal fluorides M1yM21-yFx will be presented. Detailed lithium reaction mechanisms, and Cu-loss related issues along with possible remedy solutions in the CuyFe1-yF2 system, will be discussed. [1] Wang et al., Conversion Reaction Mechanisms in Lithium Ion Batteries: Study of the Binary Metal Fluoride Electrodes, J. Am. Chem. Soc., 133 18828 (2011); [2] Wang et al., “Tracking of Li Transport and electrochemical reaction in nanoparticles”, Nat. Comm., 3 (2012) 1201.
Acknowledgement This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award Number DE-SC0001294.

As an important candidate for electric vehicle (EV) and hybrid electric vehicle (HEV) power source, lithium-ion batteries based on graphite anode and ethylene carbonate (EC) containing electrolyte have gained wide application. Ethylene carbonate (EC) forms a stable solid electrolyte interphase (SEI) at ~0.8 V before lithium intercalation. Being Li+ permeable and electronic non-conductive, SEI prevents further electrolyte decomposition and allows reversible lithiation and delithiation of graphite anode. The major disadvantage of EC is its high melting point at around 34 oC, since EC is a solid material at room temperature it needs other co-solvents such as dimethyl carbonate (DMC) and diethyl carbonate (DEC). The relatively high melting point of EC also limits the use lithium-ion batteries at low temperatures. Propylene carbonate (PC) has a wide liquid temperature range (-48.8 ~ 242.0 oC) and very good low temperature performance compared to EC. However, with only a negligible structural difference from EC, PC undergoes a detrimental solvent decomposition on the surface of graphite with high crystallinity. This causes disintegration of the graphite electrode, usually accompanied with delamination of the active material from current collector and finally cell failure.
A homologous series of propylene carbonate (PC) analogue solvents with increasing length of linear alkyl substitutes were synthesized and used as co-solvents with PC for graphite-based lithium-ion half cells. A graphite anode reaches a capacity of around 310 mAh/g in PC and its analogue co-solvents, with 99.95 percent Coulombic efficiency, similar to the values obtained with ethylene carbonate-based electrolytes. Solvent interaction with the graphite anode and subsequent decomposition determines the graphite anode performance. Gaseous products from cyclic carbonates with short alkyl chains cause exfoliation of the graphite anode; solvents with longer alkyl chains are able to prevent graphite exfoliation when used as co-solvents with PC. The PC co-solvents compete for solvation of the Li ion with the PC solvent, delaying PC co-intercalation. Reduction products of PC on a graphite surface via a single-electron path form a stable Solid Electrolyte Interphase (SEI), which allows the reversible cycling of graphite.

Silicon wafer scrap comprises a large fraction of waste generated in the semiconductor and wafer fabrication industry and may function as a feasible starting material for fabrication of silicon nanostructures for high-performance Li-ion battery anodes. Silicon waste generation via ingot trimming, cutting, polishing, and sub-standard wafer disposal is responsible for thousands of tons of Si waste yearly. Herein, we have utilized both scrap polished wafers and powderized wafers as a means for producing SiOx@Si core-shell silicon nanowires as highly stable anodes for Li-ion batteries. These SiNWs produce an initial discharge capacity of 3413 mAhg-1 and 2nd cycle capacity of 1550 mAhg-1 after SEI layer formation. After 200 cycles, the SiNWs still produce a capacity of 1273 mAhg-1 with coulombic efficiencies near 100% throughout cycling. We compare two main synthesis routes for producing SiNWs: a templated AAO thin film approach and a template-free approach utilizing powderized wafers. While both approaches utilize metal-assisted chemical etching (MACE), comparisons are drawn from both in terms of scalability, yield, morphology control, and electrochemical performance.

Polymers with two functional groups were designed for using as conductive binders in lithium battery anodes. The functional groups were chosen to enhance both the electrons and the ions conductivity. The structures of the polymers were also manipulated to obtain optimal results. High-capacity and stable anodes were achieved while applying the conductive polymer binders in silicon based electrodes.

Silicon has known to have the highest theoretical specific capacity (4200 mAh g^-1) among the anode materials for Li-ion battery, having attracted much attention as a promising anode material. However, the volume expansion of silicon (~300%) during the cycle causes pulverization and interface (SEI) formation continuously between electrode and solid electrolyte, which induce capacity fading. It has been suggested that a combination of developing void spaces within anode material and clamping the silicon with carboneous material can effectively deal with the volume expansion and continuous SEI formation.
Here we report N-doped carbon coated silicon nanoparticle prepared via magnesiothermic reduction for anode material of Li-ion battery. SiO₂ nanoparticle of which size was tens of nanometer could be coated N-doped carbon using polydopamine as the carbon source. Then, N-doped carbon coated SiO₂ nanoparticles were reduced into Si via magnesiothermic reduction. If magnesiothermic reduction was conducted stoichiometrically, the product was composed of Si and MgO, having calculated volumetric ratio of 34.9% and 65.1%, respectively. Therefore, it was expected that the volume occupied by MgO could turn into void space after reaching out by HCl and provide enough porosity to relieve the volume expansion.
N-doped carbon coated silicon nanoparticle was characterized by TEM, Nitrogen-sorption measurement, XRD. Also, electrochemical properties such as capacity, cycling stability were measured. Details on the synthesis and measurements of electrochemical property will be discussed.
(Address correspondence to [email protected], [email protected], and [email protected])

Many key performance characteristics of carbon-based lithium-ion battery anodes are determined by the strength of binding between lithium (Li) and sp² carbon (C). Using extensive density functional theory calculations, we investigate the detailed interaction of Li with a wide variety of sp² C substrates, including pristine, defective, and strained graphene; planar C clusters; nanotubes; C edges; and multilayer stacks. We find that in almost all cases, the Li-C binding energy scales is determined largely by the work required to fill unoccupied carbon states, suggesting that intrinsic quantum capacitance is important for predicting Li capacity. This allows the binding energy and capacity to be estimated based solely on the electronic structure of the substrate. It also provides a connection to carbon-based supercapacitors, and underscores the role of electronic structure in interfacial electrochemical systems. Implications for improving the effective capacity of carbon-based anodes will be discussed.

Alkaline batteries are the most common modern forms of primary battery. These cells utilize the oxidation of zinc (Zn) and the reduction of manganese dioxide (MnO2) to provide power. This reaction provides a relatively high energy density and a low cost per kilowatt-hour. However, their value as rechargeable energy storage is limited by phase transformations which occur in the cathode during discharge by more than one electron, which render the cathode material electrochemically inert. In a typical alkaline battery, useful cyclability with minimal capacity losses can only be achieved if no more than 10-20% of the cell capacity is used. We have developed a new family of electrode materials, new to the literature, which consist of aragonite- or calcite-type carbonates with extensive substitution of manganese atoms on carbon sites. These materials are produced by a simple one-step hydrothermal process, which transforms the surface of a carbon precursor material into an manganese-doped carbonate. Permanganate salts used in the synthesis process result in extensive substitution of manganese atoms into the crystal structure without significant changes in long-range order. These materials have superior capacity, rate capability and cyclability compared to gamma MnO2, with comparable cost. In this presentation, we will describe these materials as we have characterized them via electroanalytical, X-ray and electron microscopy techniques.

Lithium ion batteries are an important energy source with wide scale applications due to their high energy and power densities. As the application of Li-ion batteries has advanced to their use in electric vehicles, the demand for increased performance had led to a greater need to understand the aging mechanisms that reduce storage capacity and increase internal resistance. In order to obtain a comprehensive understanding of the battery aging process, it is imperative to study the physicochemical processes that occur during aging.
Essential to understanding degradation mechanisms is the complete characterization of changes in battery components. Characterization is complicated not only by the complexity of reactions during aging but also by the fact that these materials are air-sensitive and require an inert atmosphere to eliminate artifacts that would lead to misinterpretation of data. To address this issue, Argonne has established a state-of-the-art post-test facility that is capable of analyzing/characterizing battery components in an inert (argon) atmosphere.
Argonne&’s unique Post-test Facility has two large connected argon-filled gloveboxes with water and oxygen concentrations held below 1 ppm. One glove box is used for the dismantling of cells, both large and small, and the subsequent sample preparation for analysis. Samples are transferred to the second customized glove box (via an air-lock) for XPS, Raman and TGA-MS analysis. Samples for HPLC-MS, GCMS, FTIR and SEM are removed from the glove box in containment and analyzed in appropriately modified instrumentation. Additionally, we are capable of TEM sample preparation using ion-milling and ultramicrotomy and we have special air-tight sample holders that allow for analysis at Argonne&’s Center for Nanoscale Materials user facility using high resolution SEM and Raman with multiple laser sources. In essence, we are capable of systematically studying degradation mechanisms at a multi-scale level.
This poster presentation will describe Argonne&’s Post-Test Facility, with an emphasis on capabilities and opportunities for collaboration. Cell disassembly, sample harvesting procedures and recent results will be discussed.
This work was performed under the auspices of the U.S. Department of Energy, Office of Vehicle Technologies, Hybrid and Electric Systems, under Contract No. DE-AC02-06CH11357.

Rechargeable lithium-ion batteries (LIBs) have been attracting great interest because of their wide range of applications such as consumer devices, portable electronics, electric vehicles, hybrid electric vehicles, and large-scale grid energy storage. Unfortunately, the energy density and power capability of graphite that is the current commercial anode material remains insufficient for next-generation LIBs. N-doped nanoporous graphitic carbon is a promising anode because of its distinctive structure and physical properties. Here, we develop a novel N-doped hollow nanostructured hybrid carbon of carbon nanotubes (CNTs) and carbon nanofibers (CNFs). We report the use of a typical polymer as a sacrificed component to produce pores and C₂H₂ that serves as a carbon source for the growth of CNTs under the effect of Ni nanoparticles in N-doped CNFs formed by the calcination of electrospun composite nanofibers. Therefore, we design and exploit a novel in situ chemical vapor deposition to prepare the activated N-doped hollow CNT@CNF hybrid carbon with a superhigh specific BET surface area of 1840 m² g^-1 and a total pore volume of 1.21 m3 g^-1. The prepared novel material as an anode shows an exceptional reversible capacity of ~ 1150 mAh g^-1 at 0.1 A g-1 after 70 cycles, outstanding rate capability, and long cycling stability of over 3500 times while retaining more than 80 % capacity at 8 A g^-1.

All-solid-state lithium ion rechargeable batteries (LIBs) consisting of nonflammable solid electrolytes have been desired for higher safety. A great challenge of all-solid state LIBs for practical use is reduction of the interfacial resistance. Effective interface modification techniques have been proposed, however, the interfacial resistance is still large because the charge transfer resistance at the active material / solid electrolyte interface would be strongly affected by interfacial contact condition. Furthermore, high-volatile lithium makes difficult to retain original stoichiometry in a lithium ion conducting solid electrolyte at high temperature post sintering process. In this presentation, we proposed a new route for interface bonding of the active material / solid electrolyte interface through a direct growth of active material crystals in a Li-ion conductive glass matrix (glass-flux growth).
We used lithium-ion conducting Li3BO3 glass as a flux, and LiNO3 and Co metal layer as solutes for the LiCoO2 crystal growth. The molar ratio of the Co and the LiNO3 was controlled at 1 : 1. The flux and the solutes were deposited on a Pt substrate as a current collector. The multi-components mixed films formed on a Pt substrate as a current collector were heated at designated temperature ranging from 710 to 900oC, held for several times, then the mixture was rapidly quenched immediately.
A composite film consisting of highly crystalline LiCoO2 crystal layer and Li3BO3 system glass matrix was successfully fabricated directly onto the Pt substrate. Investigations with SEM and XRS showed that the Co layer was completely converted to highly crystalline LiCoO2 crystals having hexagonal plate-like shape. Note that, the each LiCoO2 crystals were vertically grown from the Pt substrate. XPS and EDS indicated that all interfaces of Pt substrate/LiCoO2 crystal/Li3BO3 glass were seamlessly connected without pinholes and impurity phase formation. Furthermore, we also characterized their all-solid-state LIBs performances. All results indicate that newly developed glass-flux growth provides the formation of the ionically-conductive seamless pathway of lithium ion in the LIB cells which constructed of Pt/LiCoO2 crystal/Li3BO3 glass matrix/Lithium anode. Further details of the structural and the LIB characteristics will be reported in the MRS 2014 spring meeting.

Staircase Potentiostatic Electrochemical Impedance Spectroscopy (SPEIS) can be used to generate Mott-Schottky plots (V vs. C-1 or V vs. C-2). Mott-Schottky plots are generally indicative of band bending and the flat-band potential - both of which are significant semiconductor parameters. In addition to SPEIS: we also shall utilize Potentiostatic Electrochemical Impedance Spectroscopy (PEIS) to investigate the effect of varying amplitude of applied signal. PEIS shall provide us with detailed information regarding the internal structure of an electrochemical cell. This information can be expressed in various plots, including the complex impedance plot (Z&’&’ vs. Z&’). For example: PEIS shall give us specific information regarding the electrolyte, the electrode-electrolyte interface, and about diffusion of ions in an electrochemical cell. We shall also investigate cyclic voltammetry at various significant scan rates, namely at scan rates that correspond to time constants for important electrode kinetic steps. These time constants shall be obtained via PEIS, eg. via analyzing the imaginary impedance vs. frequency plot. Lastly, PEIS is a very powerful technology to determine the rate of individual electrode kinetic steps, if their time constants are resolvable. We shall utilize PEIS to obtain an approximation for these rates1.
1. Hong, J.; Wang, C.; & Kasavajjula, U. (2006). Kinetic behavior of LiFeMgPO4 cathode material for li-ion batteries. Journal of Power Sources, 162(2), 1289.

Monolithic graphene based carbon foams with hierarchical 3D architectures and high mass-specific surface areas have many promising applications ranging from hydrogen and electrical energy storage to desalination, catalysis and actuation. Most of these applications involve the polarization of the graphene-electrolyte interface in an electrochemical environment. Here, we will discuss how to overcome the limitations and improve the interfacial capacitance of graphene based materials by electronic structure engineering and surface functionalization. The atomic scale charging mechanism of graphene-based electrodes was explored by a combination of synchrotron-based in-situ x-ray adsorption experiments and DFT simulations. The results of this study allow for the first time a correlation between macroscopic effects of graphene based electrodes such as reversible electrical conductivity changes and mechanical strain with polarization induced changes of the electronic structure. Our results will guide the development of next generation carbon-based storage materials, and open the door to new applications of monolithic nanocarbon foams including all-carbon bulk actuator and transistor technologies.
Work at LLNL was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

Lithium-rich layered-layered cathode materials (xLi2MnO3.(1-x)LiMO2, where M = Ni, Co, Mn) have gained significant attention in recent years due to their high energy density, which has a strong potential to lower the overall cost ($/kWh) in Electric Vehicle (EV) and Plug-in Hybrid Electric Vehicle (PHEV) applications. However, challenges in cycle life, calendar life, and the structural phase change during the lithium topotactic process are delaying the commercial realization of this class of materials. In order to improve the overall structural and electrochemical properties of this high-energy density material, research efforts have been focused on the development and optimization of these materials. Enhancements in the stability and performance have been achieved by engineering the composition of LiMO2 and the proportion of Li2MnO3. To further improve the performance and stability of these materials, a full understanding of the phase-change and the effects of the material composition is required.
A systematic study investigating the effect of composition on the structure of the cathode material, both for the pristine material and following extended cycling, has been carried out using synchrotron X-ray diffraction (XRD) measurements to determine how the structural evolution of the material is affected by the varying the starting composition. The structural changes occurring during the first charge/discharge cycle have also been followed by studying electrodes at different states-of-charge (SOC). The results of this study will be presented, providing insight into how the composition of the xLi2MnO3.(1-x)LiMO2 material can be engineered to improve the performance of these cathode materials.

The layered oxide compounds (1-x)LiMO2#9679;xLi2MnO3 (M= Ni, Mn, Co) are of great interest as positive electrode materials for high energy density lithium-ion batteries. In situ neutron diffraction patterns were collected on the time-of-flight diffractometer, VULCAN, at the Spallation Neutron Source (SNS) at Oak Ridge National Lab (ORNL) during electrochemical charge/discharge cycling of the lithium-excess layered compounds (1-x)LiMO2#9679;xLi2MnO3 with low excess Li content (x=0.18) and high excess Li content (x=0.5). In this work, multi-layer pouch cells with silicon as the anode material were used for in situ study. Dynamic changes in structural evolution of lattice parameters, cation migrations and oxygen occupancies are revealed to explain the lithium (de-)intercalation mechanisms in these two materials. Strong anisotropy shifting of the lattice parameters during the first cycle and the following cycles is observed. The in situ observation shows different lithium and transition metal (TM) migration mechanisms in these two materials.

Lithium-and manganese-rich nickel-manganese-cobalt (LMR-NMC) oxide cathodes (for example: Li_1.2Mn_0.55Ni_0.15Co_0.1O₂ in this study) are promising candidates in high energy density lithium-ion batteries for all-electric vehicle applications. Despite the ability of delivering the high capacity when operated at higher upper cut-off voltage (for example, 4.8V), these oxides faces several issues such as 1) voltage fade after subsequent cycles, 2) low efficiency in the first cycle, and 3) impedance rise during high-voltage hold. In this work, neutron powder diffraction (NPD), and magnetic susceptibility techniques were employed to study the structural transformation pathways in Li_1.2Mn_0.55Ni_0.15Co_0.1O₂ in order to obtain fundamental understanding on cause of these effects. The NPD and magnetic susceptibility studies were performed from the pristine and cycled Li_1.2Mn_0.55Ni_0.15Co_0.1O₂ compounds collected at different state of charges (SOC) 3.5V, 4.1V, 4.5V, and 4.7V during initial cycles and after subsequent cycles. The NPD data and the magnetic susceptibility from the pristine Li_1.2Mn_0.55Ni_0.15Co_0.1O₂ reveals that the compound is a composite between layered trigonal and layered monoclinic structure with a composition of 0.50 {Li_1-xNi_x} {Li_xCo_0.25Mn_0.375Ni_0.375-x}O₂ #9679; 0.50 Li₂MnO₃ where x= 0.0354. The magnetic susceptibility data at high temperature region (Tge; 100K) were analyzed by Curie-Weiss fitting to obtain the bulk oxidation states of transition metal ions during lithium intercalation (deintercalation) to (from) the Li_1.2Mn_0.55Ni_0.15Co_0.1O₂. Analysis showed that the oxidation state of Mn⁴⁺ (high spin/ low spin) changes to Mn³⁺ (low spin) after subsequent cycles providing a signature of a distorted spinel (Li₂Mn₂O₄) and/or spinel (LiMn₂O₄) compounds. The neutron diffraction patterns were refined by Rietveld method to obtain the structural information of these spinel phases. The detailed structural degradation mechanism (s) related to the voltage fade, first cycle irreversible capacity and impedance rise will be presented.
Acknowledgement:
This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office's (VTO) Applied Battery Research Program (Program Managers: Peter Faguy and David Howell). Research conducted at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. The LMR-NMC material was obtained from Argonne National Laboratory (ANL). The electrodes and cell fabrication, and cell testing was carried out at the DOE&’s Battery Manufacturing R&D Facility at Oak Ridge National Laboratory, which is supported by VTO within the core funding of the ABR subprogram. The authors thank Dr. Daniel Abraham and Dr. Jason Croy at ANL for useful discussions.

Layered Li₂Ru_(1-y)Sn_yO₃ have been investigated for their Li- electrochemical reactivity.¹ The electrochemical behaviour being similar to that of Li-rich layered oxides (Li_1+xNi_yCo_zMn_1-x-y-zO₂),² the material showed reversible reactivity of almost 2 lithium per Ru with stable capacity retention. The underlying mechanism for the high lithium reactivity has been analysed using EPR, XPS, Mossbauer and XRD analyses coupled with DFT calculations and found to be associated with cationic as well as anionic reversible redox processes. The voltage decay on cycling, which is preventing the present implementation of Li-Rich NMC compounds in practical Li-ion cells, is greatly reduced with Li₂Ru_(1-y)Sn_yO₃.³ A size argument was put to the forefront to explain this phenomena since the voltage decay is believed to be nested in a phase transition enlisting a migration of cations through tetrahedral sites. To better understand the root of voltage decay, the study has been extended to similar Li₂Ru_(1-y)M_yO₃ systems with M being 3d transition metal ion in +4 oxidation state. Overall, the study helps in understanding the effect of size and electronic configuration of metal substituent on long cycling voltage decay, hence providing a feasible solution.
References:
1. M. Sathiya, G. Rousse, K. Ramesha, C. P. Laisa, H. Vezin, M. T. Sougrati, M-L. Doublet, D. Foix, D. Gonbeau, W.Walker, A. S. Prakash, M. Ben Hassine, L. Dupont, J-M. Tarascon, Nat. Mater, 2013, 12, 827.
2. M. M. Thackeray, S-H. Kang, C. S. Johnson, J. T. Vaughey, R. Benedek, S. A. Hackney, J. Mater. Chem, 2007, 17, 3112.
3. M. Gu, I. Belharouak, J. Zheng, H. Wu, J. Xiao, A. Genc, K. Amine, S. Dhevuthasan, D. R. Baer, J-G. Zhang, N. D. Browning, J. Liu, C. Wang, ACS Nano, 2013, 7 (1), 760.

Lithium- and manganese-rich transition metal oxide cathodes are of great interest for the next generation of lithium ion batteries (LIBs) due to their high capacity, low cost, and thermal stability. The biggest challenge for these materials is to mitigate voltage fade during cycling, which not only reduces energy and power density, but also makes them extremely complex to be used in practical applications. The cause of voltage decay in lithium- and manganese-rich transition metal oxide cathodes is unclear and is still under extensive investigation. However, the common agreement is that voltage fade is more problematic when these materials are cycled to high potentials (above 4.4 V vs. Li/Li⁺), which is necessary to access their high capacity (> 220 mAh g^-1). Cycling the materials to high potential is believed to cause structural changes such as oxygen loss, migration of transition metals from transition metal layer into lithium layer, and transformation of layered structure to a spinel-like structure, all of which may have effect on the voltage fade phenomenon. Understanding the kinetics of the voltage fade process and how processing conditions are the first steps to control the phenomenon. In this study, we will show how oxygen partial pressure used during synthesis and cell operating temperature affect the voltage fade phenomenon.

As a composite of layered structures of Li2MnO3 and LiMO2 (M = Mn, Fe, Co, Ni), the over-lithiated-oxides (OLOs) have shown much higher storage capacity than the traditional layered oxides for Li ion battery cathode because of the Li2MnO3 phase. However, it has been observed that Li2MnO3 is not stable after the 1st charge-discharge cycle and it would partly transform into layered LiMnO2, indicating that the practically used phase is a mixture of both Li2MnO3 and LiMnO2. During the subsequent cycles, the OLO voltage decreases due to the phase transition of layered LiMnO2 into spinel. Experimentally, the effective dopants satisfying multiple cathode materials requirements of thermodynamic stability, optimized voltage and improved kinetics based on ionic and electronic conductivities are investigated to overcome the voltage degradation and to improve the power capacity. In this work, redox potential, lithium ion diffusion and charge carrier transportation of both phases are examined in details using the ab initio density-functional theory (DFT) simulations. The results showed the different Li vacancy migration behaviors in LiMnO2 and also the formation of hole polaron and electron polaron in LiMnO2 and Li2MnO3 phases, respectively. Based on the understanding of the pure phase properties, we have investigated the effects of 10 cationic (Mg, Ti, V, Nb, Fe, Ru, Co, Ni, Cu, Al) and 2 anionic (N, F) dopants on the redox potential, ionic and electric conductivity. These DFT findings could provide conceptual guidance in the experimental search for the effective dopants enabling the practical application of OLO cathodes.
This work was supported by Samsung GRO project.

The purpose of the study was to correlate surface and bulk structural characteristics of LiNixMnxCo1-2xO2 (NMC) materials with the electrochemical performance. Aided with the state-of-the-art atomic-scale annular dark-field scanning transmission electron microscopy (ADF/STEM) and electron energy loss spectroscopy (EELS) as well as ensemble-averaged synchrotron X-ray absorption spectroscopy, the present study provides insights into the surface reconstruction and chemical evolution in NMC materials and directly leverages the origin(s) of long-standing challenges in NMC materials, including high-voltage capacity fading, impedance buildup and first-cycle coulombic inefficiency. Our results represent an important pathway towards understanding layered cathode materials and the methodology herein provides guidance to advance knowledge for battery materials in general.

Spinel-structured lithium manganese oxide (LMO) cathodes are among the most promising candidates for large-scale energy storage due to their abundance, low cost, and high power capabilities. However, LMO suffers from a limited cycle life resulting from manganese dissolution in the electrolyte during electrochemical cycling [1]. Manganese dissolution not only causes loss of the active material from the cathode but also results in contamination of the anode with manganese ions. The latter has been observed in various anodes such as graphite and metallic lithium [2]. In this work, we exploit graphene coatings as a diffusion barrier [3,4] on LMO cathodes to alleviate the manganese loss problem. Specifically, a single-layer graphene sheet, grown via chemical vapor deposition, is transferred onto the surface of a spinel LMO thin film deposited on a steel substrate. The resulting graphene-coated LMO cathode successfully performs 750 charge/discharge cycles with less than 10% capacity loss, while the control uncoated LMO cathode failed after ~350 cycles with a capacity loss of ~35%. Using X-ray photoelectron spectroscopy depth profiling, it is further shown that the graphene coating effectively inhibits manganese depletion from the LMO film. Grazing incidence X-ray diffraction, Raman spectroscopy, and scanning electron microscopy are also used to characterize the structure before and after electrochemical cycling, thus verifying that the graphene-coated LMO retained its initial properties after cycling while the uncoated LMO suffered changes due to substantial manganese loss.
[1] J.-S. Kim et al., Nano Lett. 12, 6358-65 (2012).
[2] C. Zhan et al., Nat. Commun. 4, 2437 (2013).
[3] S. S. Roy, M. S. Arnold, Adv. Funct. Mater. 23, 3638-3644 (2013).
[4] J. S. Bunch et al., Nano Lett. 8, 2458-2462 (2008).

Layered lithium metal oxide LiMO₂ (M = Ni, Mn, Co; NMC) cathodes for Li-ion batteries (LIB) have come into the spotlight due to their high capacity, reliable cycle-life, and safety. However, practical use of NMC cathodes, particularly in plug-in hybrid electric vehicles (PHEV) and plug-in electric vehicles (PEV), have been delayed because of their limited power performance and drastic degradation in their capacity and cycle-life at high operation temperatures (45-60°C) and voltages (>4.3 V). One possible way to endow NMC based cathodes with quality power performance is to blend them with a compensating cathode material, such as LiMn₂O₄ spinel (LMO), which has better high rate performance. This blending method enables use of NMC:LMO hybrid cathodes for less expensive commercialized electric vehicles (e.g. GM-Volt) with improved power density. However, emerging concerns about LMO&’s lower energy density compared to NMC and capacity fade due to metallic dissolution at elevated temperatures has led to a need for researchers to develop new materials technology. Atomic layer deposition (ALD) has been employed to deposit ultrathin coatings which enhance long-term stability of cathode materials by preventing reactions at the electrode/electrolyte interface without hindering electron conduction and Li ion insertion [1-3]. Here we demonstrate that Al₂O₃-ALD coated LiNi_1/3Mn_1/3Co_1/3O₂ (NMC L333) and high-Ni NMC (LiNi_0.6Mn_0.2Co_0.2O₂, NMC L622) cathodes outperform other commercially available cathodes in both energy/power-density and high temperature stability.
References
[1] Y.S. Jung, A.S. Cavanagh, A.C. Dillon, M.D. Groner, S.M. George, S.H. Lee, Adv. Mater. 22 (2010) 2172-2176
[2] I.D. Scott, Y.S. Jung, A.S. Cavanagh, Y. Yan, A.C. Dillon, S.M. George, S.H. Lee, Nano Letters 11 (2011) 414-418
[3] L.A. Riley, S.V. Atta, A.S. Cavanagh, Y. Yan, S.M. George, P. Liu, A.C. Dillon, S.H. Lee, J. Power Sources 196 (2011) 3317-3324

Atomic layer deposition (ALD) has been employed to modify the surface of high voltage cathode LiNi0.5Mn1.5O4 by coating ultrathin Al2O3 layer on the electrodes. The ultrathin layer of Al2O3 can suppress the undesirable reactions during cycling, while maintaining the electron and ion conductivity of the electrode. After 200 cycles, the ALD Al2O3 coated LiNi0.5Mn1.5O4 showed 91% capacity retention when the bare LiNi0.5Mn1.5O4 can only maintain 75%. In addition, the ALD coated LiNi0.5Mn1.5O4 maintained 63% capacity retention after as long as 900 cycles. At an elevated temperature of 55 oC, the ALD Al2O3 coated LiNi0.5Mn1.5O4 still delivered 116 mAh/g at the 100th cycle, in comparison, the capacity for bare LiNi0.5Mn1.5O4 decreased to 98 mAh/g. The improvement is ascribed to the reduced overpotental and Li ion surface diffusion impedance. The promising results demonstrate the potential of developing high energy and long life lithium ion batteries with highly scalable LiNi0.5Mn1.5O4 preparation and broadly applicable ALD process.

High voltage cathode materials with discharge potentials near 5 V such as LiCoPO₄ have been the focus of much study over the past few years owing to their theoretical high stored energy density. Initial work on LiCoPO₄ showed a severe loss of discharge capacity upon multiple charge - discharge cycles. This was attributed to amorphization of the cathode as well as electrolyte decomposition. Doping LiCoPO₄ is a strategy that leads to improved cycle life, discharge capacity and power. Fe substitution in particular was shown to lead to much improved cycling as well as improved rate of discharge. Study of the transport through electrochemical impedance spectroscopy and DC polarization suggests that Fe doping increases the ionic and electronic conductivity of the material relative to LiCoPO₄. These improvements are in agreement with first principle modeling calculations. We have developed new generations of doped LiCoPO₄ which have further increased cycle life, discharge capacity, rate of discharge and coulombic efficiency. The synthesis and measurements of electrochemical properties and electronic and ionic transport of doped LiCoPO₄ will be discussed and compared to LiCoPO₄.

The reaction mechanisms and performances of olivine-type LiM_1-yM&’_yPO₄ (M=Fe, Mn, Co) positive electrode materials for Li-ion battery strongly depend on their composition and stoichiometry. The substitution of iron by other transition metals is known to increase the overall operating voltage without compromising the charge/discharge capacity and reversibility. The presence of a few antisite Fe³⁺ impurities in the pristine powder hinders Li⁺ diffusion into the [010] channels thus decreasing the electrochemical performances. As shown by [1, 2], higher amounts of defects, as found in nanometric particles (~40 nm), lead to a partial single phase electrochemical reaction. Furthermore, the annealing in air at moderate temperatures of stoichiometric LiM_1-yM&’_yPO₄ (0le;yle;1) powders creates significant amounts of Li/Fe antisite exchange and Fe vacancies from the oxidation of iron that leads to a brand-new electrochemical signature [3, 4].
In this work, a low temperature precipitation technique was used to synthesize different
LiM_1-yM&’_yPO₄ (0le;yle;1) compositions with structural defects (10% to 30% of Fe³⁺) [5]. The annealing of these powders in air at ~300°C preserves the olivine structure, yet significant structural modifications involve an anisotropic change in the lattice parameters up to ~500°C, temperature at which the phase decomposes. The oxidation of Fe in the structure yields the “extrusion” of Fe₂O ₃ nanoclusters at the surface of the particles and the creation of Fe vacancies. We show that a redistribution of the transition metal atoms over M(I) and M(II) crystallographic sites occurs, while Mn is found to remain stable at a +2 oxidation state.
In addition, the electrochemical signature of powders annealed at ~300°C significantly differs from the stoichiometric ones [5]. We observed several distinct phenomena, associated with highly anisotropic variations of the unit-cell constants, that occur at around 4.1 V, 3.4 V and 2.8 V vs Li⁺/Li⁰ [6]. They arise from the Fe³⁺/Fe²⁺ and Mn³⁺/Mn²⁺ redox couples, and the reaction upon Li⁺ electrochemical insertion/extraction is reported for the first time as a solid solution reaction for both redox couples. This phenomena are associated to the redistribution of part of Fe within the Li-type M1 site of the triphylite structure, which leads, additionally, to faster kinetics of Li⁺ insertion/extraction.
We will present these results assessed by powder neutron diffraction, in situ Mössbauer and X-ray diffraction measurements together with electrochemical tests.
1. P. Gibot et al. Nat Mater, 7 (9), 741-747 (2008)
2. F. Mestre-Aizpurua et al. J Power Sources, 195 (19), 6897-6901 (2010)
3. S. Hamelet et al. J Mater Chem, 19 (23), 3979 (2009)
4. S. Hamelet et al. Chem Mater, 23 (1), 32-38 (2011)
5. R. Amisse et al. J Electrochem Soc, 160 (9) A1446-A1450 (2013)
6. R. Amisse et al., Manuscript in preparation

Due to high voltage and theoretical capacity over 300 mAh/g, Li₂CoSiO₄ is a promising compound of polyoxyanion cathode materials for lithium ion batteries. However, Li₂CoSiO₄ presents obscuring complex polymorphism and unusual difficulty to realize a practical electrochemistry. Here, we report first-principles computations in coupling with simulated Xrd to characterize structures and electrochemical properties of Li_xCoSiO₄ (x=2, 1.5, 1) with symmetries Pmn2₁, Pbn2₁ and P2₁/n. The calculated Xrd spectra and voltage profiles agree well with available experimental results. We show that the CoO₄ tetrahedra, as the key units, present their fingerprint in the Xrd spectra and determine electrochemical behaviors of Li₂CoSiO₄ polymorphs. Spin ordering and Xrd spectra of bonding characteristic associated with the oxidation of CoO₄ tetrahedra are predicted for further experimental investigation. Delithiated phases are intrinsic Mott insulators. The swapping of insulating gap states during delithiation correlates with the contraction of the oxidized CoO₄ units, demonstrating the occurring of Peierls distortions. The resulting electron localization is responsible for capacity quality degrading. Our results provide guidance for further realization of high performance polymorphs suitable for applications.

We have demonstrated a simple solvothermal strategy (reaction at 220 oC) to synthesize very stable monodispersed cubic rock salt structure CoO with cube/rectangular morphology and spinel Co3O4 nanocrystals with sphere and hexagonal platelet morphology depending on the presence or absence of surfactant or change in reaction time. [1] The sizes of the as prepared CoO nanocrystals were found to be in 15-35 nm and Co3O4 nanospheres were found to be in 30-35 nm range. The dimensions of hexagonal platelets are 3-4 mu;m in diameter and ~100 nm in thickness. The structure, morphology, composition, optical absorption and surface area/pore volume distribution of the cobalt oxide samples were characterized using X-ray powder diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy, UV-Vis spectrometry and BET adsorption isotherm. Electrochemical performance of the synthesized materials (all CoO and Co3O4 samples) was evaluated using Cyclic Voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Galvanostatic charge-discharge (GCD) measurements of Co3O4 samples were carried out in two electrode cell assembly (Co3O4/KOH/Co3O4). In the present work we have obtained ~476 F/g specific capacitance for the Co3O4 hexagonal platelet with very high energy and power density of 42.3 Wh kg-1 and 1.56 kW kg-1 respectively at a high current density of 0.5 Ag-1 without utilizing any large area support. [2] This suggest that the present Co3O4 is a improved metal oxide and exhibit better performance compared to other metal oxides like MnO2, TiO2, SnO2 etc. and can be utilized for supercapacitor device fabrication. The overall electrochemical values and performance of our hexagonal Co3O4 platelet particles as pseudocapacitive material are excellent over most of the other reported Co3O4 micro/nano-structures and these observed better electrochemical properties are attributed to the layered platelet structural arrangement of the hexagonal platelet and the presence of exceptionally high numbers of regularly ordered pores.
.
References:
K. Deori and S. Deka, CrystEngComm, 2013, 15, 8465-8474.
K. Deori, S. K. Ujjain, R. K. Sharma and S. Deka, ACS Appl. Mater. Interfaces, in press, DOI: dx.doi.org/10.1021/am4027482

Tungsten oxide, originally poor in capacitive performance, was made an excellent electrode material for supercapacitors, by dispersing it to carbon aerogels (CA), a conductive and mesoporous hosting template, that drastically improved the utilization of WO3 for capacitance generation. The WO3 was introduced to the CA, in a form of well-dispersed single crystalline nanoparticles of 15-40 nm in size, with a simple immersion-calcination process. Utilization of WO3 for capacitance generation was greatly enhanced by distributing WO3 in this conductive, mesoporous template, the CA. A one order of magnitude improvement in specific capacitance was achieved with the present composition, from 54 F/g for WO3 nanoparticles to 700 F/g for WO3/CA composites (scaned at 25 mV/s in 0.5 M H2SO4 over a potential window of -0.3 to 0.5 V). The WO3/CA composites exhibited an excellent high rate capability with a 60 % retention in specific capacitance at 500 mV/s, almost perfect cycle efficiency of 99 %, and outstanding cycling stability of only 5% decay in specific capacitance after 4000 cycles. The high conductivity and mesoporous structure of a high specific surface area and large pore volume and pore size of the CA, and the formation of a thin nanostructure of WO3, single crystalline WO3 nanoparticles of 15-40 nm in size, within the CA, both contributed to the success of the WO3/CA composite in achieving its high specific capacitances, excellent high rate capability, cycle efficiency, and long term stability. The present product proves to be a promising candidate as an electrode material for next generation supercapacitors.

Pseudocapacitors aim to maintain the high power density of supercapacitors while increasing the energy density towards those of energy dense storage systems such as lithium ion batteries. Recently discovered [1] intercalation pseudocapacitors (e.g. Nb2O5) are particularly interesting because their performance is seemingly not limited by surface reactions or structures, but instead determined by the bulk crystalline structure of the material. We study [2] ordered polymorphs of Nb2O5 and detail the mechanism for the intrinsic high rates and energy density observed for this class of materials. We find that the intercalating atom (lithium) forms a solid solution adsorbing at specific sites in a network of quasi-2D NbOx faces with x={1.3, 1.67, or 2}, donating electrons locally to its neighboring atoms, reducing niobium. Open channels in the structure have low diffusion barriers for ions to migrate between these sites (Eb ~ 0.28 - 0.44 eV) comparable to high-performance solid electrolytes. Using a combination of complementary theoretical methods we rationalize this effect in LixNb2O5 for a wide range of compositions (x) and at finite temperatures. Multiple adsorption sites per unit-cell with similar adsorption energies and local charge transfer result in high capacity and energy density, while the interconnected open channels lead to low cost diffusion pathways between these sites, resulting in high power density. The nano-porous structure exhibiting local chemistry in a crystalline framework is the origin of high-rate pseudocapacitance in this new class of intercalation pseudocapacitor materials. This new insight provides guidance for improving the performance of this family of materials. Studies on doped Nb2O5 as well as other members with similar open structures such as V2O5 and Ta2O5 will also be presented. [1] Nature Materials, 2013, 12, 518-522. [2] J. Materials Chemistry A, (in press, DOI: 10.1039/C3TA13316H). This research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy

Graphene supercapacitors have been increasingly used in applications since graphene flake electrodes have high surface area, high electrical conductivity, and electrochemical stability. Especially reduced graphene oxide (rGO) flakes can be produced on a large scale from graphene oxides (GOs). Although there are numerous reports of high performance supercapacitors with porous graphene structures, there are no reports to control the interlayer gap distance between graphene sheets, which can explain the supercapacitor mechanism in terms of the accessibility of electrolyte ions. Herein, we introduce a facile, novel, and mass producible method of molecularly gap controlled reduced graphene oxides via the diazotization of phenyl derivatives (BD1), biphenyl (BD2), and para-terphenyl (BD3) bis-diazonium salts (BDs). The BDs treated graphene interlayer distances of rGO-BD1, rGO-BD2, and rGO-BD3 were 0.49, 0.72, and 0.96 nm, respectively, although the gap of rGO is 0.36 nm like graphite. Surprisingly, the 0.7 nm rGO-BD2 showed the highest capacitance value (250 F g-1 at 100 mA g-1) with a 0.6 nm sized 6 M KOH aqueous electrolyte. Our results clearly demonstrated that a slightly lager interlayer gap distance of the graphene nanosheets than the corresponding electrolyte ions resulted in the best capacitance performance. The rGO and rGO-BDs are clearly characterized by TEM, SEM, Raman spectroscopy, XPS and their supercapacitor properties are measured by electrochemical method.

The performance of electrochemical capacitors (ECs) is determined by the properties of their main components electrodes and the electrolyte. The energy density of EC is directly related to specific capacitance of the electrodes and the working potential of the device. In recent years, Ionic liquids (ILs) have attracted a lot of attention as electrolytes for ECs as they are stable at higher potentials compared to conventional aqueous and organic electrolytes, leading to higher energy density of the device. However, neat ionic liquids have much higher viscosities compared to electrolytes based on organic solvents such as acetonitrile (AN) or propylene carbonate (PC) and they are also more expensive. In this study, we introduce mixtures of ionic liquids and PC as effective substitutes for conventional organic electrolytes. We show that by using these mixtures as the electrolyte instead of a typical organic electrolyte (tetraethylammonium tetrafluoroborate (TEA BF4) in PC), we can extend the working potential and even cycle life of ECs without sacrificing the rate performance. The ionic liquids all contain the tetrafluoroborate anion just like the organic electrolyte used for comparison. The three different cations are 1-Butyl-1-methylhomopiperidinium, 1-Ethyl-1-methylpyrrolidinium, and 1,1-Dimethylpyrrolidinium. In all cases, multilayered graphene sheets are used as the electrode material. Electrochemical performance is assessed through galvanostatic cycling, cyclic voltammetry, and impedance spectroscopy. Results indicate better capacitive performance of all three IL electrolytes compared to the conventional organic electrolyte as well as an impressive capacitive stability over 10000 cycles. These electrolytes find applications in ECs with high energy density and long lifetime requirements.

Nanostructured electrochemical capacitors (ECs) are advantageous for charge and energy storage due to their large surface area-to-volume ratio, which contributes to a large electrostatic/double layer capacitance (C_dl). However, the intrinsically small density of states in nanostructures results in a quantum capacitance (C_Q) in series with C_dl which could diminish the measured device capacitance (C_tot). The lack of available states in the electrodes for the charges to occupy, is then posited as a major obstacle to achieving greater capacitances and concomitant energy densities. While such issues are just beginning to be investigated for graphene systems in the EC community, we show that higher capacitances may be harnessed in carbon nanotube arrays due to more efficient electric field screening. We have then investigated, through extensive modeling and comparison with experiment, the relative magnitudes of C_dl and C_Q in electrodes constituted of carbon nanotube arrays [1]. We will also present an equivalent circuit of C_dl and C_Q in series based on the voltage drop across C_Q. Consequently, we attribute the increase in C_tot resulting from ionizing radiation and plasma processing to an increased C_Q. Our study has deep implications for the maximum capacitance that can be obtained and measured in practical ECs. [1] H. Yamada and P. R. Bandaru, Appl. Phys. Lett. 102, 173113 (2013).

Graphene has received considerable attention in both scientific and technological areas due to its extraordinary material properties originating from the atomically single- or small number-layered structure. Nevertheless, in most scalable solution-based syntheses, graphene suffers from severe restacking between individual sheets and thus loses its material identity and advantages. In the present study, we have noticed the intercalated water molecules in the dried graphene oxide (GO) as a critical mediator to such restacking and thus eliminated the hydrogen bonding involving the intercalated water by treating GO with melamine resin (MR) monomers. Upon addition of MR monomers, porous restacking-inhibited GO sheets precipitated, leading to the carbonaceous composite with an exceptionally large surface area of 1040 m2/g after a thermal treatment. Utilizing such high surface area, the final graphene composite exhibited excellent electrochemical performance as a supercapacitor electrode material: specific capacitance of 210 F/g, almost no capacitance loss for 20000 cycles, and ~7 sec rate capability. The current study delivers a message that various condensation reactions engaging GO sheets can be a general synthetic approach for restacking-inhibited graphene in scalable solution processes.

Supercapacitors are promising energy storage devices due to their higher power density and long cycle life time (> millions) compared with conventional batteries, and greater energy density than dielectric capacitors. In order to meet the demands of a wide range of electrical and electronic technologies, such as hybrid electric vehicles, backup power sources and portable electronic equipment, supercapacitors with higher energy density and power density are required. In the past decade a great deal of effort has been devoted to improve the energy and power densities of supercapacitors that are far beyond state-of-art supercapacitors comprised of activated carbon powders. For supercapacitors, the energy density (E) is related to the cell capacitance (C) and operation voltage (V), i.e.,
E=1/2 CV^2
And the maximum power density P is determined by
P=V^2/(4*ESR)
where ESR is the equivalent series resistance of the supercapacitor cell. Equations (1) and (2) indicate that the most effective way to increase the power and energy densities is to raise V due to the square dependence of these properties on V. In general, the operation voltage of supercapacitors is limited by the electrochemical window of the electrolyte which is determined by both the electrolyte and the electrode materials. One promising approach to increase the operation voltage and hence the energy and power densities is to assemble asymmetric supercapacitors that make full use of the electrochemical windows of the two electrodes to increase the maximum cell operation voltage in the devices. Moreover, developing new electrode materials with large C and small ESR are also critical in improving both E and P of supercapacitors. Here, an asymmetric supercapacitor, exploiting nm-scale conformal coating of conducting polymer (CP) on aligned carbon nanotubes as the anode, and an ultra-high density activated microwave exfoliated graphite oxide (a-graphene) as the cathode, has been developed. The asymmetric configuration of the supercapacitor allows both electrodes to be separately tailored, increasing device capacitance and the electrochemical window, and thereby operating voltage. The conformal CP coating on the nanowires enhances charge storage of the anode while the aligned nanowire morphology provides direct non-tortuous fast ion transport pathways. The a-graphene cathode is fabricated from a self-assembly process shows high specific gravimetric and volumetric capacitance, providing an ideal cathode. As a result of complementary tailoring of the asymmetric electrodes, the device exhibits a wide 4V electrochemical window, and the highest power and energy densities reported thus far for carbon-based supercapacitors, 149 kW L-1 and 113 Wh L-1 in volumetric performance and 233 kW kg-1 and 177 Wh kg-1 in gravimetric performance, respectively.

The crystalline network of orthorhombic niobium oxide (T-Nb2O5) offers two-dimensional transport pathways for fast intercalation of lithium ions, leading to its high and rate independent intercalation capacitance. Unlike many other lithium intercalation metal oxides, T-Nb2O5 can be charged in short periods of time, making it suitable as a supercapacitor electrode material. This is due to the very low solid-state diffusion limitation and little structural change of T-Nb2O5 upon intercalation of Li ions. So far, the excellent performance of T-Nbnot;not;2O5 has been demonstrated for thin film and microelectrodes. However, for practical applications in supercapacitors, thick electrodes with large mass loadings are necessary. This will however increase the ohmic losses in the electrodes and also introduces limitations for the diffusion of Li ions into the whole thickness of the electrodes. In this study, we have addressed these issues by synthesis of three-dimensional (3D) structures of graphene and /Nb2O5 structures. These composite structures are fabricated by hydrothermal synthesis route, in which reduction of graphene oxide, deposition of Nb2O5 and formation of the 3D structures all happen at in one synthesis step. In the resulting freestanding electrodes, the 3D graphene structure acts as a highly conductive and porous current collector for Nb2O5 nanoparticles. The amorphous structures of deposited Nb2O5 particles were converted to orthorhombic structures by a post-synthesis heat treatment. The electrodes were directly tested as supercapacitor electrodes and show high capacitive performance and high rate handling capability. The high rate performance of the electrodes is believed to be the result of the intrinsic properties of T-Nb2O5 and also the unique structures of the 3D electrodes.

Synthesis of silicon carbide/nanoneedle MnO2 composites for use as high-performance materials in supercapacitors is reported by the following synthetic procedure: first, silicon carbide (SiC) was treated with hydrogen peroxide to create oxygen-containing functional groups in order to provide anchor sites between the SiC and MnO2 nanoneedles (N- MnO2). Formation of MnO2 nanoneedles was subsequently achieved on the SiC surface. The morphology and microstructure of the as-prepared composites are characterized by X-ray diffractometry, field-emission scanning electron microscopy, thermogravimetric anaylsis, X-ray photoelectron spectroscopy and BET surface area and pore volume analysis. Characterizations indicate that the MnO2 nanoneedles in the composite were homogeneously dispersed on the SiC surface. The capacitive properties of the as-prepared SiC/N- MnO2 electrodes are measured using cyclic voltammetry and galvanostatic charge/discharge test and electrochemical impedance spectroscopy in a three-electrode experimental setup using a 1 M Na2SO4 aqueous solotion as the electrolyte. The SiC/N- MnO2(3) electrode which exhibits a MnO2/SiC feeding ratio of 3:1 displays a specific capacitance as high as 265.7 F g-1 at 10 mV s-1. It is anticipate that the formation of nanoneedle structures of MnO2 on the SiC surface is a promising fabrication method for supercapacitor electrodes materials.

In lithium ion batteries, Li+ intercalation and electrode passivation processes are governed by applied potentials, which are in turn associated with the free energy changes of Li+ transfer (Delta G(t)) between the solid and liquid phases. Using ab initio molecular dynamics (AIMD) and thermodynamic integration techniques, we compute Delta G(t) for the virtual transfer of a Li+ from a LiC(6) anode slab, with lithiated edge planes exposed, to liquid ethylene carbonate confined in a nanogap. The predicted voltage dependence and electrode reactivity as functions of surface electron density and Li+ content on edge planes are contrasted with the case of LiC(6) basal planes. Li+ adsorption at edge sites, electron transfer/distribution, and salt/organic solvent decomposition associated with the initial stages of solid-electrolyte interphase formation are examined in light of the predicted electrode potential, calibrated using experimental input.
Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Deparment of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. KL was supported by Nanostructures for Electrical Energy Storage (NEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0001160.

Non-aqueous solvents in modern battery technologies (such as diethyl, dimethyl and ethylene carbonates in lithium ion batteries) undergo electroreduction at negative electrodes such as carbon and silicon, producing insoluble products that form a solid electrolyte interphase (SEI). If a stable SEI is not formed, battery performance is negatively impacted, for example by continued consumption of lithium with cycling. Many additives (such as fluoroethylene carbonate, vinylene carbonate, lithium borooxalate) have been shown to improve electrode cyclability, but the mechanisms and reactions leading to a stable SEI in alloying materials like silicon are still poorly understood. In particular, this lack of understanding inhibits the implementation of alloying materials like silicon as an electrode material and limits Li-ion battery life in general. We prepare SEI with common non-aqueous solvents (e.g., LiPF6 in EC/DEC 1:1 by wt%) on a variety of surfaces such as metals (Cu), native silicon oxide, and carbon to understand the role of surface chemistry, as well as electrode conductivity and bulk solid state electrochemistry on the surface reactions that lead to SEI. Desiccated and anoxic techniques were used to prevent air and moisture contamination of prepared SEI films, allowing for more accurate characterization of SEI chemical composition and stratification by XPS and ToF-SIMS. Additionally, the evolution of the SEI formation under different electrochemical methods (chronopotentiometry, chronoamperometry and cyclic voltammetry) was investigated. By controlling for electrode material chemistry, conductivity and electrochemistry we are able to examine particular SEI formation mechanisms that affect lithiation of negative electrodes.

Si is an attractive anode material for lithium ion batteries (LIBs) having huge theoretical capacity. To realize practical application, enhancing its cycle performance as well as simple and quick production are essential. We report the 3 mu;m-thick porous Si-Cu hybrid films rapidly deposited in 1 min on Cu current collectors and their electrochemical performance. Such quick deposition was achieved by heating the Si and Cu powder mixtures to ~ 2000 °C, well above their melting points, while the porous structure was spontaneously formed in the deposited films by keeping the Cu collector at much lower temperature of 100-500 °C. A diffuse interface was built between the hybrid film and Cu collector, which will defocus the stress working between them during charge-discharge cycles, both automatically during vapor deposition (owing to the higher vapor pressure for Cu than Si) and artificially through post annealing. The resulting hybrid films were highly reactive, showing high charge capacity closed to the theoretical value of 4000 mAh/g-Si with Li metal as the counter electrode and 1M LiClO4 in EC/PC (1:1 v/v) as electrolyte, but showed quick capacity fade possibly due to the continuous formation of the solid electrolyte interphase. Cycle performance of the hybrid films having different porosity, composition, and interface structure is now under investigation with and without vinylene carbonate additives to the electrolyte. This quick and simple deposition method of fairly-thick Si-based films with tailored microstructure will offer a practical route toward high-capacity anodes for LIBs.

A novel Silicon-Carbon Nanotubes (Si-CNTs) hybrid materials have been fabricated at different Si concentrations on Cu substrates by single step hot filament chemical vapor deposition (HFCVD). A mixture of Polymer and Si nanoparticles was used as the seeding source and Ni nanoparticles as catalysts. Micro Raman spectroscopy shows the characteristic peak for Si nanoparticles around 506 cm-1 similarly D and G peaks establish the presence of CNT. These results were confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) electron energy loss spectroscopy (EELS), X-ray Diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The hybrid materials consist of multiwall nanotubes of diameters in the range of 20-100 nm. Field Emission results shows a very low turn-on field which confirm the presence of a good electrical interface between the substrate and the CNTs, due to direct growth on Cu substrate, and between the Si coating and the CNTs. Si content in the Si/CNT was estimated using Thermo gravimetric analysis (TGA) and Inductive coupled plasma-optical emission spectrometry (ICP-OES) and it is found to be in the range of 14-22 wt.%. Electrochemical room temperature testing using coin cell batteries show that the Si-CNTs electrodes can deliver an initial high discharge capacity of around 700 mAh/g and a reversible capacity of around 500 mAh/g over 550 cycles, which is higher than the theoretical capacity of graphite electrodes. The cyclic voltammetry studies show a pair of redox peaks corresponding to lithium insertion and extraction, respectively. They also indicate good reversibility over extensive cycling, representing a promising anode material for rechargeable lithium ion batteries with high energy density. The Si-CNT films on the Cu substrate after electrochemical cycling showed that very few cracks were formed after Li alloying/dealloying. This is attributed to the high volumetric expansion of the silicon. However, the cracked film still had strong adhesion with the Cu substrate and delamination was not present.

Nowadays, rechargeable lithium battery is one of the most promising energy storage technologies to enable a various range of clean electric transportations which are essential to reduce the fossil oil dependency. To meet requirements of these applications, it is necessary to find higher capacity electrode materials. For a few years, great attention has been paid to silicon as negative electrode material for Lithium ion batteries, due to its very high gravimetric and volumetric capacities (3572 mAh g-1 and 8322 mAh cm-3) in comparison to those of graphite (372 mAh g-1 and 818 mAh cm-3). [1]
In this paper, reduced graphene oxide (rGO) was used as a conductive additive for nano silicon based lithium battery anodes with high active mass loading typically required for industrial applications. In contrast to the conventional Si electrodes using acetylene black (AcB) as an additive, the rGO system showed pronounced improvement of the electrochemical performance, irrespective of the cycling conditions. With capacity limitation, it results in improved coulombic efficiency (99.9%) and longer cycle life. Upon cycling without capacity limitation, much higher discharge capacity is maintained (2000 mAh/g after 100 cycles for 2.5 mg of Si/cm2). Used in conjunction with the bridging carboxymethyl cellulose binder, the crumpled and resilient rGO allows a highly reversible functioning of the electrode in which the Si particles repeatedly inflate and deflate upon alloying and dealloying with lithium. [2]
[1] M.N. Obrovac, L.J. Krause, J. Electrochem. Soc. 154 (2007) A103.
[2] B. P. N. Nguyen, N. A. Kumar, J. Gaubicher, F. Duclairoir, T. Brousse, O. Crosnier, Dubois, G. Bidan, D. Guyomard, B. Lestriez, Adv. Energy Mater. 2013, DOI: 10.1002/aenm.201300330

We present a comparative computational study of Li, Na, and Mg insertion into α and β tin. While β-Sn is most stable at normal conditions, reports suggested that α-Sn should be stabilized by Li ion insertion (e.g. [1]), which is also intuitive as the β phase is much denser. Energetics of doping and diffusion properties of the two phases being very different, the question of phase competition in Sn is critical for the performance of Sn anodes for Li - as well as post-Li - batteries, such as Na and Mg ion batteries.
Using a DFT / LCAO setup tuned to reproduce well absolute and relative cohesive energies of α and β tin, we compute insertion energetics for interstitial Li, Na, and Mg well-dispersed defects at a range of concentrations. While dopants prefer tetragonal sites in the cubic diamond lattice, several unique insertion sites exist in β-Sn. The most energetically favored sites in β-Sn are different for different dopant types.
Phase competition is dopant-type dependent. Specifically, at low concentrations ( M_xSn where M=Li, Na, and x<1/8), interstitial insertion sites of Li and Na in α-Sn are more favored to those in β-Sn (by of the order of 0.1 eV), but β-Sn becomes more favored for higher x values. However, Mg insertion sites in β-Sn are preferred to those in α-Sn for all concentrations studied here (by about half an eV).
Insertion energetics of Li and Na in both α-Sn and β-Sn is competitive with the metal's cohesive energies, and therefore both phases might play a role in storage depending on the cycling rate. On the contrary, the insertion energy of Mg, while lower vs. the vacuum reference state, is much higher than Mg cohesive energy for the α phase. The energy in the β phase is higher than the cohesive energy by 0.1-0.2 eV which is near the expected DFT accuracy. β-Sn could therefore work as the anode for Mg batteries.
We will also discuss the often ignored effect of vibrations on relative phase stability of the Sn anode.
[1] Hirai et al., Acta Mater. 56 (2008) 1539.

Tin as an anode in lithium ion batteries offers large theoretical charge capacity (994 mAhg-1), but also exhibits irreversible capacity loss through mechanical degradation, which results from the stresses generated by the large volume changes (~ 260%). In order to understand and possibly control mechanical degradation, a systematic investigation is carried out by selectively growing individual Li-Sn phases at specific potentials and measuring the corresponding stress and phase evolution.
Experiments are carried out on thin films of electrodeposited tin on elastic substrates. The stress evolution is measured by monitoring the substrate curvature during the lithiation and delithiation cycling. A kinetic model based on a simple kinetic picture is used to analyze the phase progression from the experimental data. Focused ion beam (FIB) milling and X-ray diffraction (XRD) are used to identify the lithiated phases that formed. The thicknesses of the lithiated phase were measured in the FIB cross-sectional images, which are used to interpret the curvature data in terms of stress evolution and the yielding stress for each phase. The mechanical property, biaxial modulus, of the lithiated phases are obtained from the delithiation experiments.

Thin-film Li-ion battery (TFLIB) anodes that alloy with Li, including Si, Ge, Sn, and Al have specific capacities that significantly exceed that of carbon-based intercalation anodes. However, the large volume expansion/contraction that accompanies charging/discharging processes lead to prominent mechanical stresses that ultimately induce loss in capacity and failure of the anodes. Here, we combine real-time scanning electron microscopy under ultra-high vacuum conditions with electrochemical cycling to quantify the dynamic degradation of the Al anode upon charging/discharging of a TFLIB with a N-doped LiPO₄ (LiPON) electrolyte and a LiCoO₂ cathode. Our approach allows us to precisely control the lithiation rate, record the voltage, and to correlate these parameters with specific changes in the electrode morphology; providing a quantitative and real-time analysis of the anode degradation. Surprisingly, we find that significant changes in the Al film morphology occur at very low lithiation level, at asymp; 1.0 % Li in Al. A capacity of 20 mu;Ah/cm² is reached on the first charge cycle, which is equivalent to 94% of theoretical cathode capacity and 20% of anode capacity. With increasing number of cycles the smooth surface of the Al anode film is significantly roughened and covered with Fd3m AlLi mounds. The battery degrades accordingly, losing asymp;90 % of its capacity after 100 cycles. The origin of the discharge capacity fade is directly related to the Li being trapped in the mounds, which is due to the blockage of Li and Al diffusion pathways necessary for the decomposition of LiAl at room temperature. This process is a direct consequence of the extremely low diffusivity of Li within Al, which will be discussed in details. The spatially resolved and in situ measurements of Li+ diffusion during lithiation/de-lithiation in an operating TFLIB model system represents an important step towards understanding and engineering the surface of metal anodes to improve capacity in rechargeable batteries.

Lithium titanate electrodes are of great importance for developing lithium-ion batteries (LIB) with advanced properties. Li4Ti5O12 (LTO) basically has a spinel structure and partially occupies the 16d sites of Ti atoms by Li atoms. By the Li insertion into LTO, the LTO phase is changed into the Li7Ti5O12 (Li-LTO) phase with an extremely small volume change. The inserted Li atoms usually occupy the 16c sites and initial Li atoms at the 8a sites move to the vacant 16c sites. Though this process the basal Ti-O framework structure is not change. The Li-LTO phase reversibly recovers to the LTO one by the Li extraction process. Thus it is important to clarify the interphase-boundary structures of Li4+xTi5O12 (x=0-3), approaching the intermediate charge or discharge state. In the Li insertion/extraction process, there are two candidate models. The first model is that with clear phase separation between LTO and Li-LTO with apparent phase boundaries [1], PS-model, and the second model is that with no clear phase separation, but has some kind of solid-solution states [2], SS-model. Recently we have reported atomic and electronic structures of bulk LTO and Li-LTO by first-principles calculations [3] and by transmission electron microscopy [4-6] and LTO surfaces by scanning probe microscopy [5-7], and the calculation results well correspond to the experimental ones. In this work, we perform the first-principles calculations for the interphase-boundary structures of Li4+xTi5O12 (x=0-3) and make detail analyses with related experimental aspects. Present first-principles calculations are carried out using the projector augmented-wave (PAW) program code QMAS [8]. The supercell structures of Li4+xTi5O12 interphase boundaries are constructed by the Li insertion to bulk LTO and Li extraction from bulk Li-LTO models, from Li32+xTi40O96 to Li56-xTi40O96. The obtained supercell structures are fully optimized for atomic positions and cell size. The structures of Ti-O frameworks are not drastically change by Li insertion/extraction process, which is consistent with the reversible behavior of LTO under charge-discharge process in LIB. In the energy analyses, the PS-model is energetically more favorable than the SS-model, thus in early Li insertion/extraction process the clear two-phase separation should exist. This work was supported by Grant-in-Aid (22360279), the Japan Society for the Promotion of Science Research (JSPS). [1] N. Takami et al., J. Electrochem. Soc. 158, A725 (2011). [2] M. Wagemaker et al., J. Phys. Chem. B 113, 224 (2009). [3] S. Tanaka et al., J. Phys. D: Appl. Phys. 45, 494004 (2012). [4] M. Kitta et al., J. Power Sources 237, 26 (2013). [5] M. Kitta et al., Appl. Surf. Sci. 258, 3147 (2012). [6] M. Kitta et al., Langmuir 28, 12384 (2012). [7] M. Kitta et al., Surf. Sci. (2013) in print. [8] http://qmas.jp.

Hematite with a theoretical capacity of 1007 mA h g-1 has been attracting much attention as promising candidate to replace carbon in lithium ion batteries. It is always practically interesting and intellectually challenging to develop facile methods to prepare Fe2O3 with unique hollow nanostructures. We report the fast template-free preparation of hollow α-Fe2O3 with unique cocoon-like structure by a one-pot hydrothermal method without templates or surfactants in just 3 hours. In contrast, typical methods to prepare inorganic hollow structures require few days of reaction and templates and/or surfactants are used. The materials were thoroughly characterized by FESEM, TEM and XRD. Ex-situ analysis of a series of samples prepared at different reaction time clearly reveals the evolution and formation mechanism involved. Superior electrochemical performance in terms of cyclability, specific capacity and high rate was achieved, which could be attributed to its unique structure. Structural stability was revealed by analysis the samples after 120 charge-discharge cycles. Experimental evidences also demonstrate that hollow nanococoons exceed solid nanococoons in reversible lithium ion storage.

With increasing demanding of energy, it becomes more and more important to find alternative energy sources beyond fossil fuel. Batteries, especially lithium ion batteries (LIB), provide unique advantages with their high energy densities (up to 150 Whkg-1). To meet the requirement for applications in electric vehicle (EV) and hybrid electric vehicle (HEV), it is desirable to develop high energy density and low cost materials. With current Li-ion technology, lithium in the cell is limited from cathode material, e.g., LiCoO2 etc., and electrolyte. Solid-Electrolyte Interphase (SEI) formation during initial cycles consumes lithium and results partial capacity loss irreversibly. The incorporation of stabilized lithium metal powder (SLMP), developed by FMC corporation, into anode has been suggested to overcome the irreversible capacity loss, and increase the capacity by 5~10%. Moreover, some non-lithiated materials with high specific capacities can be used as cathode materials if coupled with pre-lithiated anodes. With this strategy, the full cell energy density can be significantly improved.
In this study, we demonstrate the application of SLMP in our anode materials. Performance of prelithiated cells was compared with that of regular cells. The first cycle capacity loss of SLMP prelithiated cell was largely reduced and the corresponding first cycle Coulombic efficiency was significantly improved. The full cell with SLMP prelithiation but without any standard cell formation process showed better cycle performance than that of none SLMP containing cell with standard formation process. Prelithiation of anode with SLMP promote stable SEI formation on the surface of anode materials. Development of such SEI (using SLMP method) is equivalent to or even better than the slow formation protocols used in regular lithium ion cells. Application of SLMP in lithium-ion battery thus provides an effective method to enhance and maintain capacity, and promises a low cost SEI formation process.