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]

Intercalation electrodes provide the highest energy density battery systems. Hence, understanding diffusion of ions other than Li in such electrode materials is important to assess the feasibility of “Beyond Li” technologies. Both Na and Mg are being considered as alternatives to lithium. In this presentation we will compare the diffusion mechanisms for Li, Na and Mg in typical intercalation materials. Layered Na-oxides have recently been shown to be able to achieve rates > 30C, and in many layered oxides Na diffusion seems faster than Li diffusion. Mg being a divalent ion shows much slower diffusion in many intercalation hosts. Results for the migration barrier of Mg diffusion in different hosts will be shown.

The extraction, exchange, and separation of ions in solution have been studied extensively because of applications in seawater desalination, elemental purification, and wastewater treatment. Reversible electrochemical insertion of ions into materials would present a valuable alternative to existing methods of ion exchange because of the ease of cycling and reuse. Reversible insertion of monovalent ions has been thoroughly explored because of its application in intercalation battery electrodes, including electrodes for nickel-metal hydride and lithium-ion batteries. However, the stable and reversible insertion of divalent or trivalent ions into materials remains an unsolved problem.
Copper hexacyanoferrate (CuHCF), a Prussian Blue analogue, possesses a unique open framework structure that allows for the reversible insertion of a wide variety of multivalent cations, including many alkaline earth, rare earth, and transition metal cations. The material demonstrates unprecedented kinetics, reversibility, and cycle life for multivalent ion insertion. However, little is known about the processes by which multivalent ions can readily insert into CuHCF. Ongoing synchrotron X-ray and neutron diffraction experiments have begun to provide insight on the ion insertion mechanism in the material and on the complex interplay between vacancies, water molecules, and insertion ions in the structure.

Cubic garnet of nominal composition Li7La3Zr2O12 (LLZO) is of interest as a possible electrolyte in batteries composed of molten Li as an anode and sulfur or an insoluble metal halide as a cathode operating in the temperature range 300-350C. As a consequence the chemical stability of dense (>98% relative density) cubic LLZO stabilized by different dopants in molten lithium and sulfur in the temperature range 300-350C was characterized by x-ray diffraction, electron microscopy, x-ray photoemission spectroscopy and electron paramagnetic resonance. The results revealed LLZO had undergone chemical coloration and exhibited intergranular cracking after immersion in molten Li. These results will discussed and compared to other Li and Na-ion conductors tested in a similar temperature range.

Recently a new, large family of two-dimensional (2D) early transition metal carbides and carbonitrides, called MXenes, was discovered. MXenes are produced by selective etching of the A element from the MAX phases. the latter metallically conductive layered solids, connected by strong metallic, ionic, and covalent bonds such as Ti2AlC, Ti3AlC2, Ta4AlC3, etc. MXenes combine the metallic conductivity of transition metal carbide layers with the hydrophilic nature of their hydroxyl or oxygen terminated surfaces. In essence, they behave as “conductive clays”. MXenes are expected to be good candidates for a host of applications. They have already shown promising performance in electrochemical energy storage systems. However, we are only starting to explore the potential of MXenes as anode materials for Li-ion batteries and their use in electrochemical capacitors.
Herein, we report on the intercalation of Li+, Na+, Mg2+, K+, NH4+, and Al3+ ions between the 2D Ti3C2Tx and Ti2CTx layers. In most cases, the cations intercalated spontaneously. The intercalation of some ions, notably Al3+, can be promoted electrochemically. We also report on intercalation-induced high volumetric capacitance of flexible Ti3C2Tx paper electrodes. This study provides a basis for exploring a large family of 2D carbides and carbonitrides in electrochemical energy storage applications using single- and multivalent ions.

Electrochemical energy storage relies on the breaking and reforming of chemical bonds to store and recover energy. Energy is stored through the decomposition of a stable compound, MX, into more elemental components, M and X and is recovered by the reverse reaction, M+X→MX. Experience with Li-ion batteries has shown that reversibly forming and breaking bonds electrochemically is most facile for intercalation reactions, whereby ions are shuttled between electrodes and fill the interstitial sites of a rigid host structure that undergoes minimal dimensional and structural changes. First-principles computational methods have proven invaluable in elucidating and predicting a wide variety of thermodynamic and kinetic properties of electrode and electrolyte materials. In this talk I will describe how these tools can be used to explore and design new electrochemical energy storage concepts and devices.

Doped cubic phases of garnet-related Li7La3Zr2O12 (LLZ) have a strong application potential as solid electrolytes for all-solid-state batteries and as protective layers for anodes in Lithium-air batteries due to their favorable combination of high ionic conductivity with chemical and electrochemical stability versus both lithium and cathode materials. Lithium oxide volatility at temperatures suitable for conventional sintering however favors the formation of non-Li+-conducting La2Zr2O7 phase and impedes the formation of dense, phase pure membranes. Hence a lower synthesis temperature is required for the retention of Li. From Rietveld refinement of in situ neutron diffraction data in combination with thermogravimetric analysis we could determine (both the undoped and doped) LLZ variation in the mass fractions of the phases involved at different temperatures during the formation process from ball-milled precursor mixtures. Pentavalent doping on the Zr site and (to a lesser extent) trivalent doping on the Li+ sites enhance Li+ diffusion, whereas Ga3+ doping essentially stabilizes the cubic phase with minimal effect on the conductivity. Addition of 1 - 2 wt% Ga2O3 as a sintering agent to precursor mixtures for pentavalently doped LLZ has been found to densify the membrane (96% of theoretical density) at a sintering temperature of 1150°C and thus enhance the total Li+ ion conductivity by one order of magnitude. The low melting temperature of TeO2 (733°C) makes it attractive as a sintering agent. Indeed Te-doping is found to stabilize the fast ion conducting cubic phase at a moderate formation temperature of 750°C. However, the lower redox stability of Te4+ may limit application of LLZ with high Te dopant concentrations.
Low-temperature sol-gel synthesis of undoped and (Ta-, Nb- and Al-) doped LLZ samples has also been carried out. The fast ion conducting cubic phase was successfully formed at 750°C, 850°C and 950°C. La2Zr2O7 impurities in samples prepared at the lowest temperature could be suppressed by enriching the mother powder in Li2CO3 during the subsequent sintering at 900°C. Due to the porosity of the samples formed by sol-gel method the Li+ ion conductivity of the LLZ samples made was one order of magnitude lower than those made via conventional solid state reaction. Performance studies of the different LLZ samples as solid electrolytes in all-solid state batteries and as anode-protecting membrane in Li-air as well as Li redox flow battery configurations will be discussed.

Large-scale applications of lithium ion batteries for transportation and storage of renewable energy require high energy densities, high power, reduced costs and, most importantly, safety. The use of liquid organic electrolytes that exhibit high vapor pressures and flammability poses a substantial safety issue in particular for large-scale systems. Solid electrolytes offer a potential solution due to their inherent chemical stability. In addition to being lithium ion conductors, solid electrolytes act as separators between the electrodes. Recently, several material systems such as LLZO (Li₇La₃Zr₂O₁₂) have been identified that exhibit ionic conductivities similar to those of liquid electrolytes at moderate temperatures paving the way to integrate these materials in battery cells.
In the present work, we report on the synthesis and characterization of Al-doped LLZO solid electrolyte with grain sizes in the range of 40 to 300 nm. The main goal is to establish the role of the grain size and the residual porosity in the electrolyte layer on the conductivity. The material was synthesized using nebulized spray pyrolysis (NSP). NSP is an aerosol-based synthesis method that allows for a high production rate on a laboratory scale and is scalable for mass production. Pellets consolidated from as-synthesized powders were sintered at 1000 °C to obtain the desired phase-pure cubic garnet material. The structure of the powders and the sintered ceramics was characterized by means of X-Ray diffraction (XRD). Furthermore, the microstructure was analyzed using secondary electron microscopy (SEM). The electrochemical performance of the sintered pellets was studied, in relation with the microstructural information, and compared to the performance of materials prepared by solid state reaction.

The lithium solid-state electrolyte (SSE) of Li5La3Nb2O12 (LLNO) was synthesized via a novel molten salt synthesis (MSS) method at a relatively low temperature of 900°C. The low sintering temperature prevented the loss of lithium which commonly occurs during synthesis of the SSE using conventional solid-state or wet chemical reactions. Recent publications have demonstrated that preserving the Li content is critical in improving the ionic conductivity of SSEs. In this study, X-ray photoelectron spectroscopy (XPS) showed that the synthesis of the LLNO was successful, without any Li loss, by using the MSS method. The LLNO in this experiment showed a high Li-ion conductivity comparable to the values reported for LLNO in the literature. X-ray diffraction (XRD) measurements confirmed the formation of the cubic garnet Ia-3d crystal structure. In addition, the morphology was examined by scanning electron microscope (SEM), which showed a uniform grain size and crack free microstructure. These results demonstrate that the MSS is a powerful synthesis method to fabricate LLNO at a relatively low temperature while still achieving a high quality material.

Na-ion batteries have attracted recent interest and start now to be counted as viable alternatives vs. Li ion technologies for specific applications. Indeed, recent works on phosphate-based Na-containing positive electrodes such as Na3V2(PO4)3 [1] and Na3V2(PO4)2F3 [2] have demonstrated excellent performances and can be considered as a new step on the way of sodium-ion technology development. However, like for the Li-ion technology, safety issues related to the use of flammable liquid electrolytes remain, especially due to the high reactivity of sodium with moisture and oxygen. All-solid state batteries, which use non-flammable solid electrolytes instead of organic liquid ones, have been proposed as strong candidates for alternative energy storage devices [3-5].
Following a recent successful approach developed for Li-ion all-solid state batteries [6, 7], we were able to assemble a monolithic all-solid state Na-ion battery using NASICON-type electrodes and electrolyte in a single step using the spark plasma sintering technique. Na3V2(PO4)3 was used as both positive (V4+/V3+ couple) and negative (V3+/V2+) electrodes while Na3Zr2Si2PO12 was used as the solid electrolyte. Both compositions present order-disorder phase transitions and present decent ionic conductivities of 1.5 x10 3 S cm-1 and 1.9 x10-4 S cm-1 at 200°C for Na3Zr2Si2PO12 and Na3V2(PO4)3, respectively. Thanks to a new experimental set-up, we report for the first time on the electrochemical characteristics of an all solid state Na-ion battery at temperatures as high as 200°C [8]. The battery operates at 1.8 V with 85% of the theoretical capacity attained at C/10 with good capacity retention, for an overall energy density of 1.87 x10-3 W h cm-2 and a capacity of 1.04 mA h cm-2.
[1]K. Saravanan, C.W. Mason, A. Rudola, K.H. Wong, P. Balaya, Advanced Energy Materials, 3 (2013) 444-450.
[2]A. Ponrouch, R. Dedryvere, D. Monti, A.E. Demet, J.-M. Ateba Mba, L. Croguennec, C. Masquelier, P. Johansson, M.R. Palacin, Energy & Environmental Science, 6 (2013) 2361-2369.
[3]T. Ohtomo, A. Hayashi, M. Tatsumisago, Y. Tsuchida, S. Hama, K. Kawamoto, Journal of Power Sources, 233 (2013) 231-235.
[4]M. Nagao, Y. Imade, H. Narisawa, T. Kobayashi, R. Watanabe, T. Yokoi, T. Tatsumi, R. Kanno, Journal of Power Sources, 222 (2013) 237-242.
[5]S. Boulineau, J.-M. Tarascon, J.-B. Leriche, V. Viallet, Solid State Ionics, 242 (2013) 45-48.
[6]A. Aboulaich, R. Bouchet, G. Delaizir, V. Seznec, L. Tortet, M. Morcrette, P. Rozier, J.M. Tarascon, V. Viallet, M. Dollé, Advanced Energy Materials, 1 (2011) 179-183.
[7]G. Delaizir, V. Viallet, A. Aboulaich, R. Bouchet, L. Tortet, V. Seznec, M. Morcrette, J.-M. Tarascon, P. Rozier, M. Dollé, Advanced Functional Materials, 22 (2012) 2140-2147.
[8]F. Lalère, J.B. Leriche, M. Courty, S. Boulineau, V. Viallet, C. Masquelier, V. Seznec, Journal of Power Sources, 247 (2014) 975-980.

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.
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(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.

One revolutionary example of rechargeable batteries is the birth of lithium ion batteries in the early 1990s. However, the safety from the combustible organic electrolytes is a serious and challenging problem in the case of large-scale applications such as energy storage in smart grids. As a result, it comes back to aqueous electrolyte again. However, it is neutral and green, and one example is aqueous rechargeable lithium batteries of super-fast charging performance and excellent cycling [1,2]. Recently, the energy density is markedly improved in comparison with that for lithium ion batteries due to the “cross-over” effect instead of the traditional overpotentials [3]. This effect will bring unpredicted promise for the new power sources since it can markedly increase the output voltage of aqueous batteries to above 3 V, much higher than the theoretical stable window of water, 1.23 V. The estimated practical energy density will be much higher than those for lithium ion batteries. This opens a new choice for smart grids and electric vehicles as a chemistry of post lithium ion batteries.
Acknowledgment
Financial support from MOST (2010DFA61770), STCSM (12JC1401200) and NSFC (21073046) is greatly appreciated.
References:
[1] W. Tang, L.L. Liu, Y.S. Zhu, H. Sun, Y.P. Wu, K. Zhu, Energy Environ. Sci., 5, 6909-6913 (2012).
[2] W. Tang, Y.S. Zhu, Y.Y. Hou, L.L. Liu, Y.P. Wu, K.P. Loh, H.P. Zhang and Kai Zhu, Energy Environ. Sci., 6, 2093-2104 (2013).
[3] X.J. Wang, Y.Y. Hou, Y.S. Zhu, Y.P. Wu, R. Holze, Sci. Rep., 3, 1401 (2013).
[4] X.J. Wang, Q.T. Qu Y.Y. Hou, F.X. Wang, Y.P. Wu, Chem. Commun., 49, 6179 - 6181 (2013).

Despite the commercial success of Li-ion batteries for portable electronics and electric vehicle applications, proven safety issues and the declining availability of lithium has spurred the pursuit of new technologies (e.g., batteries with Mg- or Al-based anodes) and a revisit of some conventional batteries, but with a new eye. Of the latter approach, zinc-based batteries (e.g., Zn-air and Ni-Zn) are a compelling option because they can deliver high specific energy in safe, low-cost forms, but they are confined to specialized primary (single-use) applications because the conventional Zn anode (packed-powder bed) undergoes dendritic growth during cycling that limits rechargeability. To both overcome the Zn dendrite problem and to increase the upper-limit discharge capacity of Zn-based batteries, we have architecturally redesigned the zinc anode to take on a sponge morphology that expresses a 3-dimensional aperiodic form factor. The Zn sponge redesign provides (i) an inner core of Zn that is retained throughout battery charge/discharge to facilitate long-range electronic conductivity; (ii) amplification of electrified interfaces to distribute current uniformly throughout the electrode structure, and thus eliminate dendrite-forming high current densities; and (iii) confined void volume elements within the interior of the porous anode that expedite saturation/dehydration of zincate to ZnO, thus preventing shape change. We have demonstrated that such Zn sponges achieve 90% Zn utilization (728 mA h g_Zn^-1 in a primary Zn-air cell and >40 dendrite-free cycles at 25 mA cm^-2 charge/discharge in a symmetric Zn||ZnO cell (alkaline electrolyte). Here we present our recent efforts to develop rechargeable Zn-based batteries using the Zn sponge anode architecture in conjunction with cathodes optimized for Zn-air, Ni-Zn, and Ag-Zn cell configurations.

Dendritic Li growth and limited Coulombic efficiency (CE) during Li deposition/stripping are two main barriers prevented practical applications Li metal as an anode for rechargeable batteries in the last 40 years. We recently proposed a novel self-healing electrostatic shield (SHES) mechanism which can fundamentally change the dynamics of Li deposition and obtain dendrite-free Li film electrodeposited on Cu substrates. However, CE of Li deposition obtained in the previous work was only ~ 76% due to the use of propylene carbonate (PC) as the electrolyte solvent. To enable dendrite-free Li deposition with high CE, various electrolyte salts, solvents, as well as additives have been investigated in this work. A small amount of vinylene carbonate (VC) has been added to the SHES electrolytes to form a stable solid electrolyte interphase (SEI) and improve the CE of Li deposition. To explore the origin of the SEI layer and its effect on Li deposition, X-ray photoelectron spectroscopy (XPS) were used to analyze the surface compositions change on Cu substrate after application of voltage bias but before Li deposition starts. 2 wt% VC leads to a distinctive improvement of coulombic efficiency from 74.7% to 92.6%. XPS spectra reveal that the CsPF6 additive can change the surface compositions of the Cu substrates prior to the start of Li deposition. Deposition of Li in the control electrolyte use the similar surface treatment but without CsPF6 additive cannot result in dendrite-free Li layers, indicating the Cs+ has the decisive effect on the suppression of Li dendrites. In addition to the surface morphology investigation by scanning electron microscopy (SEM), the clear cross-sectional structure of dendrite-free Li layers was reported for the first time in this work. It is very interesting that the as-deposited dendrite-free Li layers are actually composed of highly-compacted Li nanorods with semispherical tips, rather than semispherical Li particles as previous reports. With improved electrolyte solvent and additive, dendrite-free Li film with a CE of > 98% has been obtained. The full growth pattern of Li film revealed in this work will provide a clear insight into the deposition/stripping mechanism of Li metal anodes. Further development of this approach will enable dendrite-free Li deposition with a high CE required for the practical application of rechargeable Li metal batteries.

The ability to spontaneously repair damage, which is termed as self-healing, is an important survival feature in nature because it increases the lifetime of most living creatures. This feature is highly desirable for rechargeable batteries because the lifetime of high-capacity electrodes, such as silicon anodes, has been shortened by the mechanical fractures generated during the cycling process. Here, inspired by nature, we apply self-healing chemistry to silicon microparticle anodes to overcome their short cycle life. Coating Si anodes with a room temperature repeatable self-healing polymer, we show that the low-cost native Si microparticles (~3-8 micro), for which stable deep galvanostatic cycling was previously impossible, can now have an excellent cycle life. We attain a cycle life of 10 times longer than state-of-art anodes made from Si microparticles while retaining a high capacity (up to >3,000 mAh/g). Cracks and damage in the coating during cycling can be spontaneously healed due to the presence of the self-healing polymers rationally designed to have features, such as room-temperature reversible healing due to the hydrogen bonding chemistry, the amorphous structure, its low glass transition temperature and the high stretchability.
[1] C. Wang, H. Wu, Z. Chen, M. T. McDowell, Y. Cui, Z. Bao, Nat. Chem. 2013, 5, in press.

Multivalent battery systems like rechargeable magnesium (Mg) batteries are garnering more interest as candidate post-lithium (Li) battery systems, for eventual applications in electric vehicles (EVs) and plug-in hybrid vehicles (PHVs). This is primarily due to concerns over the range performance of current Li battery systems, and the space requirements for future EVs and PHVs.^1-4 Mg, being divalent and denser, is theoretically capable of delivering a higher volumetric energy-density (3833 mAh cm^-3) than Li (2061 mAh cm^-3), making it a viable battery system for addressing current range and space concerns.^1-3 To date, various low voltage organohaloaluminate electrolytes have been utilized in Mg battery systems, due to the incompatibility of high voltage conventional battery electrolytes (TFSI^-, ClO₄^-, PF₆^-) with Mg metal anodes.^5-8
As we recently reported, it is however possible to use conventional battery electrolytes for Mg battery systems, by changing the type of anode, from a Mg metal anode to a Mg-ion insertion-type anode (e.g. Bi and Sn). This change enables Mg-ion transport through the anode/electrolyte interface during the use of conventional battery electrolytes.^3,9 Here, we report the recent progress in the use of such insertion-type anodes for rechargeable Mg-ion batteries, using conventional battery electrolytes. Further, although the compatibility of such insertion-type anodes with conventional battery electrolytes is good, we address specific issues related to the various anode/electrolyte interfaces for Mg-ion batteries, which are now being studied in detail.¹⁰ Results from recent fundamental analyses, focused on studying and understanding these various anode/electrolyte interfaces, will be presented and discussed.
References:
1 J.-M. Tarascon and M. Armand, Nature, 2001, 414, 359.
2 P. Novak, R. Imhof and O. Haas, Electrochim. Acta, 1999, 45, 351.
3 T. S. Arthur, N. Singh and M. Matsui, Electrochem. Commun., 2012, 16, 103.
4 D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich and E. Levi, Nature, 2000, 407, 724.
5 D. Aurbach, J. Weissman, Y. Gofer and E. Levi, Chem. Rec., 2003, 3, 61.
6 Z. Lu, A. Schechter, M. Moshkovich and D. Aurbach, J. Electroanal. Chem., 1999, 466, 203.
7 T. D. Gregory, R. J. Hoffman and R. C. Winterton, J. Electrochem. Soc., 1990, 137, 775.
8 J. Muldoon, C. B. Bucur, A. G. Oliver, T. Sugimoto, M. Matsui, H. S. Kim, G. D. Allred, J. Zajicek and Y. Kotani, Energy Environ. Sci., 2012, 5, 5941.
9 N. Singh, T. S. Arthur, C. Ling, M. Matsui and F. Mizuno, Chem. Commun., 2013, 49, 149.
10 T. S. Arthur, P-A. Glans, M. Matsui, R. Zhang, B. Ma and J. Guo, Electrochem. Commun., 2012, 24, 43.

One of the challenges for successful development of sodium ion batteries is identification of a suitable anode material with high capacity and good cyclability. The most promising materials for this application in the short term are likely to be intercalation compounds due to safety concerns with hard carbons and the large volume changes associated with metal alloying reactions, two alternatives currently being investigated. Our current research is focused on sodium titanate intercalation compounds for this purpose. A variety of structures can be synthesized depending on conditions, Na/Ti ratios, and the presence or absence of additional elements in the precursor mix, but most have either tunnel, stepped layered or corrugated layered structures. Because of site limitation issues with the tunnel compounds, the layered variants are of greater interest for use in batteries. Our recent work has focused on a stepped layered compound derived from dehydration of NaTi3O6(OH).2H2O (also known as sodium nonatitanate), and those with lepidocrocite-type (corrugated layered) structures. Both types of materials exhibit reversible sodium and lithium ion intercalation processes at very low potentials vs. the alkali metal (~0.5V), and have gradually sloping voltage profiles indicative of solid solution processes. The theoretical capacities of these materials are high, ranging from 200-300 mAh/g depending on exact composition, making them of interest for further development for use in either sodium ion or lithium ion batteries.

Very recently, redox flow lithium-ion battery (RFLB) has emerged as a new electrochemical energy storage solution with great advantages over the conventional redox flow batteries and lithium-ion batteries.[1] In RFLB the active electrode materials are reversibly delithiated/lithiated via redox targeting reactions without being attached to the current collector. The transport of electrons between the active material and current collector is mediated by the diffusion of redox shuttle molecules in the electrolyte. While LiFePO4 have been successfully demonstrated in RFLB, so far there isn&’t report on the reversible chemical lithiation/delithiation of anodic materials. As a promising anodic material, anatase TiO2 has drawn considerable attention and the electrochemical lithiation/delithiation of TiO2 have been extensively investigated.[2] In contrast, while chemical lithiation of TiO2 by n-butyllithium has been reported by several groups,[3] the reaction is irreversible and no chemical delithiation was reported.
Here we report for the first time the reversible chemical lithiation/delithiation of TiO2 and its application in RFLB. It was observed that anatase TiO2 can reversibly be lithiated in the presence of bis(pentamethylcyclopentadienyl)cobalt (CoCp*2) in battery electrolyte and then be delithiated by cobaltocene (CoCp2). The reactions can be described as follows:
xLi+ + TiO2 + xCoCp*2 ---> LixTiO2 + xCoCp*2+ (1)
LixTiO2 + xCoCp2+ ---> xLi+ +TiO2 + xCoCp2 (2)
The reversible Li+ insertion and extraction in the presence of the two redox mediators were confirmed by Raman, UV-vis, and XPS spectroscopic measurements. A redox flow lithium-ion battery was assembled based on CoCp*2, CoCp2 and TiO2, and was tested galvanostatically. In a preliminary test, >66% TiO2 which was immersed in electrolyte away from the current collector, was reversibly charged/discharged through redox targeting reactions.
[1] Huang, Q.; Li, H.; Gratzel, M.; Wang, Q. Physical chemistry chemical physics : PCCP 2013, 15, 1793.
[2] Deng, D.; Kim, M. G.; Lee, J. Y.; Cho, J. Energy & Environmental Science 2009, 2, 818.
[3] Wagemaker, M.; Borghols, W. J.; Mulder, F. M. Journal of the American Chemical Society 2007, 129, 4323.

The increasing utilization of renewable energy sources is driving the need for low-cost medium-to-large scale energy storage systems. A promising approach is the Semi Solid Flow Cell (SSFC), which operates on the principle of moving suspensions of active materials past inert electrodes to store or utilize electricity. Energy and power density can be scaled independently, which gives these systems distinct advantages over existing technologies. While SSFCs have great potential for future applications, they are subject to complex physical and electrochemical processes. To date, the SSFC approach has only been applied to the lithium ion chemistry and its suitability for other chemistries remains largely unknown. Here we present a thorough analysis of the thermodynamics and kinetics of such battery systems, with the goal to identify crucial design and performance requirements. Using the example of the lead acid chemistry, suspension stability and particle-to-electrode resistance were identified as the performance-limiting parameters. The results of the study were used to develop tools for evaluating the suitability of different battery chemistries for the SSFC approach and to provide a road map for the design of a functional SSFC.

The morphological evolution of the metal-electrolyte interface during repetitive charging and discharging is critical to the performance and reliability of batteries. Recharging of zinc, lead or lithium-air batteries deposits metal on the anode. Control of morphology during deposition is important so that one can avoid growth instabilities such as dendrite formation, which can reduce capacity and cause short-circuiting or even battery ignition. Several strategies have been proposed to suppress growth instabilities. It is possible to flow the electrolyte or to modify the electrolyte chemistry with additives. However, a simpler approach is to use pulse charging, where short pauses in the charging current allow ion concentration gradients to level out. In order to assess the mechanisms at work and the effectiveness of this approach, it is helpful to examine the morphological evolution of the growth interface during charging, in real time and with nanoscale resolution. Here we describe the results of in situ transmission electron microscopy (TEM) experiments in which we record growth morphology at video rate during electrochemical deposition in a test system, copper in acidified copper sulphate solution. Experiments were carried out using the Nanoaquarium liquid cell in a Hitachi H-9000 TEM operated at 300kV. Three integrated Pt electrodes were connected to a potentiostat to control the current and record the potential during galvanostatic deposition, while simultaneously imaging the resulting growth at video rate (30 images per second). We will first describe the interface morphology and growth kinetics during continuous plating and pulse plating using pulses of different durations. Measuring the RMS roughness of the growth front allows us to quantify the onset of instability and identify the transition from uniform growth to dendritic growth as a function of current density and pulse time. We will show that pulse plating can create a smooth deposit, even for current densities that produce dendrites if applied continuously. We will also show interface evolution during pulse-reverse plating, a technique in which part of the deposit is stripped during pauses in growth. We find that the growth front can be significantly roughened by pulse-reverse plating, depending on the conditions chosen. We will discuss these results in the context of battery cycling.
The work was supported in part by National Science Foundation grants 1129722, 1066573, 1310639 and 1031208.

Graphene-based materials have been widely used in Li-ion batteries. However, their potential for use in Na-ion batteries is not well understood. We present a firtst ab initio study of sodium adsorption and diffusion on graphene that considered Na clustering, graphene defects, and dispersion forces.
At the GGA DFT level, Na atoms prefer to adsorb at the Hex sites and diffuse via the bridge site. The adsorption energy of -0.75 eV vs the vacuum state is weaker than the cohesive energy of Na metal. The adsorption becomes competitive with Na metal cohesive energy when dispersion corrections are included (DFT-D), with Eads = -1.14 eV. DFT-D slightly changes relative energetics and geometry of different adsorption sites. This is explained by analysing a model potential term used in DFT-D. Both DFT and DFT-D predict that clustering of Na atoms adsorbed an neighboring sites is energetically favored. This is evidenced by smaller charge donation to graphene, about 0.5 e compared to about 0.9 e for single atom adsorption as well as by the formation of a Na-Na bond identified by analysis of the electron density.
These results suggest that despite a low diffusion barrier of the order of 0.1 eV, ideal graphene is not a promising material for Na ion battery anodes. They also highlight the necessity to include dispersion forces when modeling alkali atom interaction with graphene derivatives.
Finally, we study the effect of point defects and B/N doping on the Na-graphene interaction and show that Na storage capability can thereby be enhanced.

In this talk, I will present a recent progress on the polyanionic phosphates that function as cathode materials in sodium ion batteries (SIBs). I will first cover vanadium-containing frameworks that show very stable voltage curves in different potential regimes with advantageous behaviors such as single flat voltage plateaus and the presence of intermediate phases that are beneficial for cell kinetics. In the second half of my talk, I will introduce some anomalous manganese activation in the SIB pyrophosphate family that overcomes the chronic Jahn-Teller distortion, in contrast to the Li counterparts. By employing DFT calculations, it turned out that such anomalous activation is originated from its unique crystal structure where corner-sharing is the main structural change during the phase transformation in the charge-discharge processes. Throughout the talk, unique SIB properties as compared to the LIB analogues even for the same chemical formulae will be discussed.

A number of key science questions must be answered to establish the limits of achieving reversible and efficient oxygen electrochemistry in aprotic organic electrolytes. Such information is essential for the development of rechargeable alkali metal - oxygen batteries. In this paper, we seek to determine if the formation of lithium peroxide at carbon electrode is driven by nucleation at the electron transfer sites or by saturation of the superoxide and subsequent disproportionation in the aprotic electrolyte resulting in the precipitation at the electrode surface. If a through solution pathway is operative, we need to understand where peroxide is likely to nucleate, the form and properties with which it grows as a function of discharge rate, and whether the growth sites are likely to support sustained electron transfer during the oxygen evolution or charging reaction. This information is essential in determining suitable cathode architectures. Electrochemical scanning probe microscopic (EC-SPM) measurements for 1 M Lithium bis(trifluoromethane)sulfonimide in tetraethylene glycol dimethyl ether show a significant delay between the onset of the galvanostatically driven oxygen reduction reaction and the first appearance of a solid product at the surface of graphite, arguing a significant solution pathway. Initial nucleation is directed toward the step edges, the more electrochemically active defect sites when compared to the basal plane, making it difficult to determine whether saturation first occurs near step edges. Additional measurements using lithium peroxide pre-saturated electrolyte show that this delay is greatly reduced and nucleation is no longer preferred along the step edges. We demonstrate an experimental method on an EC-SPM for decoupling the site of electron transfer and the site where product forms to better understanding of whether product formation is a solution-mediated process. We apply this methodology to explore the discharge rate dependence on spatial distribution, composition and structure (ex situ Raman and transmission electron microscopy), and properties (electrical conductivity) of the reduced product formed. Comparisons are made between several different aprotic solvent and supporting electrolyte salts and with alternate cathode materials including gold and manganese dioxide to aid in determining the impact of both electrolyte and cathode substrate on product properties.
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. Sandia is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE&’s NNSA under contract DE-AC04-94AL85000.

Rechargeable batteries based on aluminum are attractive alternatives to those based on conventional chemistries because of the low cost and high charge-storage capacity of aluminum. Aluminum is the most abundant metal in the earth&’s crust, and its cost is significantly lower than that of most other metals used as active materials in batteries. The volumetric capacity of aluminum metal is 8.0 Ah/cm^3, which is four times higher than that of lithium. Aluminum is also competitive in terms of gravimetric capacity (3.0 Ah/g vs. lithium&’s 3.9 Ah/g or sodium&’s 1.2 Ah/g). Aluminum batteries based on aqueous or high-temperature molten salt electrolytes have been the subject of extensive research but have faced prohibitive technical barriers. An alternative type of rechargeable aluminum battery is based on imidiazolium chloroaluminate salts, which are liquid at room temperature. Electrochemical plating and stripping of aluminum metal in such solutions have been studied in detail, forming the basis for the negative electrode (anode) in a rechargeable aluminum battery. Active materials for the positive electrode (cathode) have been far less explored.
Presented here is the use of conductive polymers as anion-insertion electrodes in rechargeable aluminum batteries operating at room temperature. Such polymers can be electrochemically oxidized and reduced in chloroaluminate ionic liquids at room temperature. Such cycling has been demonstrated previously with polypyrrole, polythiophene, and polyaniline in chloroaluminate ionic liquids, but metrics that are important for battery characterization (such as specific capacity and cycling stability) were not reported.
For the present study, polypyrrole and polythiophene, in the form of electropolymerized films and suspension-cast composite electrodes, were cycled at room temperature using 1-ethyl-3-methylimidazolium chloroaluminate as the electrolyte and aluminum metal as the anode. The insertion and removal of chloroaluminate anions into and out of the conductive polymers were confirmed using elemental analysis, electrochemical characterization, and quartz crystal microbalance. Polythiophene electrodes exhibited electrochemical activity at potentials greater than 1.3 V vs. aluminum metal. Specific gravimetric capacity of the conductive polymers was measured and shown to be highly dependent on the voltage range for cycling. Excellent cycling stability for hundreds of cycles and coulombic efficiencies greater than 99% were observed. The results were used to estimate the specific energy density of the polythiophene-aluminum cell chemistry at 50 Wh/kg, which is competitive for grid-scale energy storage.
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.

Recently Sodium-Oxygen Batteries have attracted strong interested, as they show much higher round-trip efficiencies than lithium-oxygen cells. In fact, the formation of a stable NaO2 phase (sodium superoxide) by one-electron transfer requires only very small cathodic overvoltages (smaller than 100 mV). However, it is now also known that much higher overvoltages occur when sodium peroxide is formed, i.e. when the cell chemistry follows the similar route as in a lithium-oxygen cell.
Here we will present new results on the thermodynamics and the kinetics of non-aqueous sodium-oxygen batteries (sodium superoxide battery). These include the study of different cathode materials, conducting salts and an extended study of the pressure dynamics during discharge and charge. By modifying the cycling parameters we can obtain now more than 100 dicharge/charge cycles.
[1] P. Hartmann et al., Nat. Mater. 12 (2013) 228

The ubiquitous need for mobile energy storage forces us to consider the availability and cost of battery materials as an important factor in their ability to fulfill energy storage demands. Many materials used in the production of batteries today employ elements of low abundance such as Li and Co. These materials also have limited availability as their production is limited geographically. Calcium, on the other hand, is a superb choice to use as the basis for alternative battery strategies as it is highly abundant and geographically disperse. Additionally, the power loss when moving to the Ca²⁺/Ca redox couple is minimal compared to that of other alternative cations. The high charge density of Ca²⁺ limits its applicability as a battery material to conversion systems. Therefore, we have explored the calcium-sulfur (Ca-S) conversion battery system as an alternative technology to that of lithium-based systems. We find that the Ca-S system exhibits capacities of 600 mA.h/g (S basis) as a primary cell. The capacity is a result of the oxidation of calcium and the reduction of sulfur in a single discharge process to produce CaS_x. Contrary to the Li-S system, the Ca oxidation at the anode limits the capacity of the cell and the Ca solid electrolyte interface (SEI) causes high impedance and low sulfur utilization.

Phase diagram is of critical importance for predicting and explaining the electrochemical properties of cathode materials. We have determined the phase diagram of olivine NaxFePO4 (0 < x < 1) which is very different from that of LixFePO4.
At room temperature, the phase diagram consists of two regions. For x < 2/3, phase separation to FePO4/Na2/3FePO4 was found to be favorable, while for x > 2/3 solid-solution phase NaxFePO4 is the ground state. Mössbauer spectra revealed two types of local environment for the Fe2+ ions in the single-phase region of NaxFePO4 (2/3 < x < 1). Ab initio calculations suggest that the Fe2+ site with very low quadrupole splitting (1.7 mm/s) corresponds to highly distorted sites. Temperature-dependent XRD found that the phase diagram at room temperature was firmly maintained until 500 °C. Above 500 °C, NaFePO4 converts to the ground-state maricite structure, while NaxFePO4 decomposes to a variety of products. The stronger relaxation of the sodium structure will stabilize NaxFePO4 because it will disperse the elastic strain resulting from the coexistence of Fe2+ and Fe3+ ions in the same lattice, which have quite different average Feminus;O bond lengths (computed values of sim;2.0 and 2.2 Å, respectively). The larger unit cell size for NaxFePO4 (sim;17% larger than that of FePO4 at x = 1) compared with LixFePO4 allows larger room for such structural relaxation.
In searching new materials, as often missed by the ground state screening, experimental identification of metastable functional phase by entropy gain (including disorder and/or defects) at finite temperature is important and efective. Very promising new cathode materials led by this concept will be introduced as time permits.
Ref. J. Lu, S. C. Chung, et al., and A. Yamada, Chem. Mater., 10.1021/cm402617b (2013)

With the pressing needs for economically feasible and environmentally benign energy storage technologies, Na-ion batteries have re-captured the attention of the scientific community due to its natural abundance and broad distribution. In this talk, we will report our recent work on novel electrode materials for Na-ion batteries. Na2Ti3O7 is able to provide 177 mAh/g capacity at an ultra low voltage, 0.3 V, making it a very promising anode for high energy density Na-ion full cells. A combination of experimental and computational studies has been conducted to investigate the anode material&’s working principles and to improve its electrochemical properties. A phase transformation has been identified upon cycling, and charge compensation mechanisms have been studied. Excellent cycling properties at different current rates have been obtained after carbon coating. In addition to the anode research, we have led a systematic investigation of layered Na transition metal (TM) oxides, Nax[LiyNizMn1-y-z]O2 (0

Magnesium rechargeable battery is one of candidates for next generation battery system. The advantage of magnesium battery is the high theoretical capacity, low cost and stability of magnesium metal anode. One of challenges for the practical application is development of cathode materials. Compared to lithium ions, insertion reaction of magnesium ions into the host compounds has more difficulty due to stronger ionic interaction and harder redistribution of the charge of the inserted multivalent cations in host materials. Therefore, the compounds which can serve as magnesium hosts are limited. In this study we apply the polyanion compounds to magnesium battery cathodes. We investigate electrochemical magnesium insertion/extraction of polyanion compounds. And then the mechanism of magnesium insertion/extraction is analyzed by using X-ray absorption spectroscopy and X-ray diffraction.
Electrodes were prepared from polyanion compounds to which carbon black (acetylene black) was added and ball-milled. Polytetrafluoroethylene binder was thereafter added. Three electrodes were used. Mg rod and double junction-type Ag+/Ag were used as the counter and reference electrode respectively. 0.5 M Mg[N(CF3SO2)2]2 / acetonitrile was used as electrolyte. Measurements were performed at 55oC. XAS spectra were measured in a transmission mode at the beam line BL01B1 at SPring-8 (Japan). XRD measurements were carried out at the beam line BL02B2 at SPring-8 (Japan).
Electrochemical cycling tests show that Mg2+ can be reversibly inserted/extracted at 55oC. The absorption edge from XAS is shifted towards lower/higher energy with discharging/charging, respectively. This result indicates that the formal valence of iron is decreased/increased with Mg insertion/extraction process. We further demonstrate the feasibility of reversible Mg deposition and dissolution using a magnesium Mg[N(CF3SO2)2]2 / triglyme electrolyte that exhibits a high-voltage window. Combination of a triglyme-based electrolyte system not only presents a practical high-energy-density Mg-ion rechargeable battery, but also is free of toxic and explosive chemicals.

Renewable energy sources such as solar and wind power are fundamentally different from conventional energy generation from fossil fuels because of their inherent intermittency. A new kind of energy storage technology is needed for short-term grid storage applications, as existing technology struggle to meet the needs of these applications at a reasonable price.
We recently demonstrated promising results with a new family of battery electrode materials based on the common, inexpensive Prussian Blue pigment. The open framework (OF) structure of Prussian Blue analogues (PBAs) is fundamentally different from other insertion electrode materials because of its large channels and interstices. This structure is composed of a face-centered cubic framework of transition metal cations where each cation is octahedrally coordinated to hexacyanometallate groups. Large interstitial “A Sites” within the structure can accommodate zeolitic water and hydrated alkali ions. This results in a general chemical formula of AxPR(CN)6 nH2O, where A is an alkali cation such as K+ or Na+, P is a transition metal cation and R(CN)6 is a hexacyanometallate anion. Both the P-site transition metal cation and the R(CN)63- hexacyanometallate anion can be electrochemically active in this structure. The Prussian Blue framework structure has wide channels between the A sites, allowing rapid insertion and removal of Na+, K+, and other ions from aqueous solutions. In addition, there is little lattice strain during cycling because the A sites are larger than the hydrated ions that are inserted and removed from them. The result is an extremely stable electrode: over 40,000 deep discharge cycles were demonstrated in the case of the copper hexacyanoferrate cathode [1]. These OF structure cathodes are ideally paired with an anode that has comparable cycle life and kinetics to avoid a substantial constraint in the performance of the full battery [2].
Here, we report a newly developed manganese hexacyanomanganate OF anode that has the same crystal structure. By combining this new anode with the previously reported copper hexacyanoferrate cathode we demonstrate a new type of safe, fast, inexpensive, long-cycle life aqueous electrolyte battery which involves the transport and insertion of sodium ions. This high rate, high efficiency cell has shown a 96.7% round trip energy efficiency when cycled at a 5C rate, and an 84.2% energy efficiency at a 50C rate. There was no measurable capacity loss after 1000 deep-discharge cycles. Bulk quantities of the electrode materials can be produced by a room temperature chemical synthesis from earth-abundant precursors, and the cell operates in a safe and inexpensive aqueous sodium-ion electrolyte.
References
(1) Wessells, C. D.; Huggins, R. A.; Cui, Y. Nat. Commun. 2011, 2, 550.
(2) Pasta, M.; Wessells, C. D.; Huggins, R. A.; Cui, Y. Nat. Commun. 2012, 3, 1149.

Lithium ion batteries are quickly becoming the mainstream power sources for environmentally friendly vehicles such as hybrid vehicles (HV), plug-in hybrid vehicles (PHV) and electric vehicles (EV) due to their high energy density. However, since a battery system with even higher energy density is required for the long-range PHV or EV applications, post lithium ion batteries (PLIB) such as Li-sulfur batteries or Li-air batteries have been getting more attention in recent years. Rechargeable magnesium batteries are also a candidate for the PLIB due to the natural abundance of magnesium and the absence of dendrite formation when magnesium metal is used as the anode. In addition, a magnesium-metal electrode is expected to have high energy density, due to its divalent nature. However, the discovery and development of high voltage and capacity cathode materials that can surpass the performance of Chevrel phase materials such as Mo6S8 remains a challenge. The difficulty lies in the strong polarization character of the small and divalent Mg2+ and consequently the intercalation and diffusion of Mg2+ ions is somewhat difficult and complicated.
In this presentation, we will report our recent progress on Mg battery cathode research. Those novel cathode materials have been successfully applied in Mg battery showing high capacity and flat voltage plateau. Amazingly, through the novel electrochemical mechanism design, some of the cathode materials show remarkable rate capability due to avoiding the slugging intercalation of divalent Mg2+ in solid. The reaction mechanism of those cathode materials was investigated by multiple techniques, such as XRD, TEM-EELS, XAS, etc.

Significant progress has been made in Na-intercalation compounds for rechargeable Na batteries. P2 type layered oxides NaMO2 have been shown to have high capacity, good cyclability, and improved rate capability. In this study, we present results of first-principles calculations and ab initio molecular dynamics simulations on the diffusion mechanism in P2-NaMO2. Our computational results demonstrate that P2 sodium metal layered oxides are fast Na ionic conductors over a wide range of Na concentrations. We identify the Na diffusion mechanisms in P2 at non-dilute Na concentrations and compare them to diffusion in an O3-type layered compound. Our results suggest that P2 outperforms O3 in Na diffusion kinetics and that P2 is a promising cathode material with high rate capabilities. Methods to improve the rate performance in P2-type materials will be discussed.

The research and development of rechargeable Li-air or Li-O2 batteries has attracted significant attention and effort in recent years due to the batteries&’ ultra-high theoretical specific energy (~5200 Wh/kg when the weights of Li and oxygen are included) and the high expected practical specific energy of around 800 Wh/kg that is about 4 times of those of the state-of-the-art Li ion batteries (ca. 200 Wh/kg). However, significant challenges need to be addressed to achieve reasonably practical applications, such as the selection of stable electrolyte, decrease of charge-discharge voltage hysteresis, design of cathode materials with high capacity and stability, protection of the Li anode, supply of moisture-free air, and so on. It is well known now the major discharge product is Li2O2 when the Li-O2 cell is discharged in electrolytes containing ether or glyme and DMSO as the solvent. Such discharge process is mostly a two-electron electrochemical reduction reaction. The one-electron reduction intermediate, i.e. superoxide radical anion is hypothetically existent but has never been directly detected in non-aqueous electrolyte based Li-O2 batteries because the extremely short lifetime of superoxide radical anion especially at the presence of Li+. Similarly the hypothesis is suggested to the charging process as well. To have a clear understanding on the reaction routes during discharge and charge processes of the Li-O2 batteries will help researchers in this field design new electrolyte and electrode materials to promote the desired reactions and avoid detrimental reactions. Recently, we have systematically investigated the discharging process of the nonaqueous Li-O2 batteries using electron paramagnetic resonance (EPR) technique and have successfully detected the formation of superoxide radical anion during the oxygen reduction reaction. The charging process has also been studied. Details of the investigations will be reported and discussed in the presentation.
Acknowledgement
This work was supported by the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the Basic Energy Sciences, Office of Science of the U.S. DOE. The EPR measurements were performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE&’s Office of Biological and Environmental Research and located at PNNL.

The performance and robustness of energy storage devices can benefit from the usage of functional polymers. I will discuss incorporating conducting polymer hydrogels for high capacity Si nanoparticle anodes with more than 5000 charging and discharging cycles. We also adapted self-healing polymer to enable stable operation of more than 100 cycles for Si microparticles. Finally high surface area conducting polymers and carbon are used for ultra-high speed charging and discharging for supercapacitors.

In this work we have developed a new fabrication method for colloidal nanoparticle (NP) assemblies for battery electrodes that require no additional support or conductive materials such as polymeric binders or carbon black. By eliminating these additives we are able to improve the battery capacity/weight ratio. The film is formed by using electrophoretic deposition (EPD) of colloidally synthesized, monodisperse cobalt NPs. We have deomstrated this technique for transition metal oxides and metal chalcogenides. For the metal oxides we oxidize cobalt and form hollow Co₃O₄ NPs through the Kirkendall effect. EPD forms a network of NPs that are mechanically very robust and electrically-connected, enabling them to act as the Li-ion battery anode. The morphology change through cycles indicates stable 5 - 10 nm NPs form after the first lithiation remained throughout the cycling process. This NP-film battery made without binders and conductive additives shows high gravimetric (>830 mAh/g) and volumetric capacities (>2100 mAh/cm³) even after 50 cycles. Because similar films made from drop-casting do not perform well under the same conditions, EPD is seen as the critical step to create good contacts between the particles and electrodes resulting in this significant improvement in battery electrode assembly. Colloidal metal chalcogenide NPs also can be assembled as an electrode by utilizing EPD. Unlike cobalt NP case, the organic surfactant ligands of the NPs are effectively removed by ammonium sulfide ((NH₄)₂S) treatment. This NP film without additives works as a battery electrode showing an excellent cyclability with high capacities close to their theoretical capacities. This is a promising system for colloidal nanoparticles to build a simple and robust electrode and a template for investigating the mechanism of lithiation and delithiation of NPs.
D.H. Ha, M.A. Islam, and R.D. Robinson, “Binder-free and Carbon-free Nanoparticle Batteries: A Method for Nanoparticle Electrodes without Polymeric Binders or Carbon Black,” Nano Letters 12, 5122 (2012)
H. Zhang, B. Hu, L. Sun, R. Hovden, F.W. Wise, D.A. Muller, and R.D. Robinson, “Surfactant Ligand Removal and Rational Fabrication of Inorganically Connected Quantum Dots,” Nano Letters 11, 5356 (2011).

Capacitive energy storage is distinguished from other types of electrochemical energy, such as batteries, by shorter charging times and higher power. This technology has attracted considerable interest because the energy densities can be increased with better choice of material. One interesting pseudocapacitive material is orthorhombic α-MoO3, which is a layered compound with a high theoretical lithium capacity of 300 mAh/g (1080C/g). However, this material exhibits poor capacity retention due to the occurrence of phase changes upon lithium insertion. We are investigating non-stoichiometric α-MoO3 (NS-α-MoO3) since the oxygen vacancies suppress the phase changes and improve the electronic conductivity. Here we report our recent studies on non-stoichiometric α-MoO3 which exhibits increased levels of pseudocapacitance and enhanced energy storage properties compared to stoichiometric α-MoO3.
Microwave hydrothermal synthesis was used to prepare oxygen deficient NS-α-MoO3. The orthorhombic phase and nanobelt morphology of this material was confirmed by XRD and TEM, respectively. Raman analysis indicates that the van der Waals gap for NS-α-MoO3 expands due to the structural distortion caused by oxygen vacancies in NS-α-MoO3. While cyclic voltammetry of α-MoO3 shows irreversible peaks in the first cycle, no irreversible peaks were observed for NS-α-MoO3.In addition, a near-theoretical capacity of 1000 C/g was obtained at 1 mV/s for NS-α-MoO3. At a scan rate of 50 mV/s, which corresponds to a charge-discharge time of one minute, NS-α-MoO3 is able to store 60% of the theoretical capacity with good cycle life. The results presented here demonstrate the improvement in electrochemical properties of NS-α-MoO3 over α-MoO3 by the addition of oxygen vacancies to improve both structural stability and conductivity.

Advances in battery technology have become increasingly important to sustain an electrified society. Silicon anodes, with ten times the theoretical capacity of state-of-the-art carbonaceous anodes, are promising for application not only in traditional Li-ion batteries, but also in next-generation Li-O2 and Li-S batteries to replace dendrite-forming Li metal anodes. The main challenges associated with silicon anodes are: structural degradation and unstable solid-electrolyte interphase (SEI) caused by the colossal volume change (~300%) during cycling; increased side-reactions with the electrolyte and low volumetric energy density when the material size is reduced to the nanoscale. Here, we report a pomegranate-inspired hierarchical structure with electrically interconnected primary Si nanoparticles and individually engineered nanoscale empty space encapsulated by carbon layer to form micrometer secondary particles, that simultaneously overcomes all these problems. Internally accommodated volume expansion and spatially confined SEI formation results in superior cycle life (1000 cycles with 97% capacity retention), while the secondary structure lowers the electrode/electrolyte contact area for improvement of Coulombic efficiency and increases tap density. Furthermore, we demonstrate unprecedented stable cycling (100 cycles with 94% capacity retention) with high areal capacity (3.7 mAh cm-2), similar to the areal capacity of commercial Li-ion batteries. The successful design principles developed in this study can be widely applied to other high-capacity Li battery electrodes.

High power energy storage devices, such as Li-ion batteries, are critical for the development of zero-emission electrical vehicles, large scale smart grid, and energy efficient ships and locomotives. The energy storage characteristics of Li-ion batteries are mostly determined by the specific capacities of their electrodes, while their power characteristics are influenced by the maximum rate of the ion transport. Selected chemistries offer very high capacities, but suffer from various limitations, such as volume changes, low ionic or low electronic conductivities, chemical and electrochemical instabilities, to mention a few. The talk will focus on the development of nanocomposite electrodes capable to improve both the cycle life as well as energy and power storage characteristics of the state of the art Li-ion batteries. Selected materials showed the unprecedented ultra-fast charging and discharging characteristics and stable performance for 100-2000 cycles. In order to overcome the limitations of traditional composites precise control over the materials&’ structure, porosity and surface coatings were required.

Layered sodium oxides with the formula NaxMO2 (M is a transition metal) have been intensively studied these last thirty years either for their unique physical properties (high thermoelectric power, superconductivity hellip;) or with a view for their use in large sodium-ion batteries. In this context we have studied different NaxMO2 systems which differ one from another by the nature of the transition metal (M = V, Ni, Mo), by the type of site that sodium occupies, either octahedral or prismatic, and by the number of different MO2 layers needed to describe the structure. The electrochemical study of these systems in sodium batteries, associated with in situ X-ray diffraction experiments, allowed for the first time to get a precise overview of their room temperature phase diagram. We then focused on the synthesis on the phases with the Na1/2MO2 composition. Their structure was determined from high resolution powder X-ray diffraction data and we found that a sodium/vacancy existed in those phases of each system. More precisely, three polymorphs Na1/2VO2 were studied. We have found that the three phases present not a sodium ordering between the VO2 layers, but also a peculiar arrangement of the vanadium ions within the VO2 slabs which form either pseudotrimers in the P2 phase (ABBA oxygen stacking, Na+ in prisms) and in the P&’3 phase (AABBCCA oxygen stacking with a monoclinic distortion, Na+ in prisms) or V-V pairs the O&’3 phase (ABCA oxygen stacking with a monoclinic distortion, Na+ in octahedra). As a consequence the three polymorphs present very different magnetic and transport properties. As an example, we found that the P2 and the P&’3 phases presented a first order transition near room temperature for which their electronic conductivity gained two orders of magnitude. Simultaneously a structural transition occured and the results obtained from high resolution powder diffraction and pair distribution function analysis indicated that the disappearance of the vanadium pseudotrimers was associated with this transition. This work on the NaxVO2 system showed that the arrangement of Na+ ions between the VO2 layers greatly affects the electron localization. This is a crucial point to keep in mind when considering sodium layered oxides with the general formula NaxMO2 for use as positive electrode materials in batteries, as transport properties can vary greatly during electrochemical cycling.

The expanding roles of electrochemical energy storage systems range from vehicle electrification, to grid reliability, and the utilization of renewable energy sources. Although Li-Ion batteries have emerged as perhaps the most attractive system, there is now renewed interest in Na-Ion technology since there are abundant reserves of sodium, its cost is low, and its intercalation chemistry is similar to that of lithium. Previous studies on the interrelationship between crystal structure and intercalation processes for Na-Ion batteries have led to the discovery of several positive electrode transition metal oxide materials. On the other hand, the intercalation properties for the corresponding negative electrodes have not been well established and it is now clear that novel negative electrode materials capable of reversibly intercalating the larger Na-ions are necessary for the advancement of this battery technology. Recent studies have shown that capacities of up to 200 mAh.g-1 can be achieved with sodium trititanate (Na2Ti3O7), however the question of long-term stability still remains unanswered. The 2D morphology of Na2Ti3O7 lends itself to exfoliation methods and the formation of nanosheets. The ability to form nanosheets enables us to investigate sodium intercalation properties at the nanoscale and to gain insight about structure and chemical stability while improving capacity retention. In our study, nanosheets were exfoliated from layered Na2Ti3O7 particles by proton exchange with hydrochloric acid and chemical reaction with methylamine and propylamine (PA). The final product consisted of (Ti3O7)-2 nanosheets separated by much larger PA ions. An improvement in capacity retention and sodium insertion was expected by forming a stable NaxTi3O7 structure upon electrochemical cycling. Electrochemical properties were investigated using cyclic voltammetry and our initial results indicate good reversibility for the titanate nanosheets with capacities in the range of 100 to 150 mAh/g depending upon the rate of charge storage.

Activated carbon materials play a major role as electrode materials for electrochemical capacitors because of their well developed specific surface area, low price and acceptable electrochemical stability. Activated carbons enriched with heteroatoms such as nitrogen or oxygen demonstrates pseudocapacitive properties, however, their cycle life is rather unsatisfying. It seems that long cycling degrades the functionalities responsible for redox response. In this work we present the great advantage of quinone/hydroquinone redox couple as a source of additional capacitance, present not only on the electrode surface but also in the electrolyte. Redox-active electrolytes, e.g. iodide/iodine-based couple is quite novel idea and tends to be more popular because of its usefulness. By generation functional groups on the carbon electrode surface (grafting process cannot be excluded) directly from electrolyte gives the possibility to enhance the capacitance value and specific energy significantly. Hydroxybenzene solutions with different substitution of hydroxyl groups were effectively used in order to do it. Accordingly, an important step to meet the increasing demand for energy consumption without using lithium - ion technology was made.
This study is focused on the electrochemical and physicochemical investigations of capacitive properties demonstrated by carbon materials characterized by different properties such as specific surface area, pore size distribution, N or O content. Especially, electrochemical performance after assumed electrochemical grafting was studied. In order to observe it, several electrochemical techniques, such as galvanostatic charging/discharging (0.2 - 50 A/g), cyclic voltammetry (1-100 mV/s) and electrochemical impedance spectroscopy (100 kHz - 1 mHz) were applied. Significant capacitance enhancement (ca. 120% at moderate current regimes) was observed, especially in acidic medium. Three-electrode cell investigations demonstrated that electrochemical activity of differently substituted hydroxybenzenes is observed at different potentials. The self-discharge profile is acceptable (91% of capacitance retention). Cyclability recorded over 10,000 cycles was maintained at 87% of initial value. In order to explain the origin of observed capacitance enhancement, carbon materials used were characterized with other techniques. Thermogravimmetric analysis demonstrated higher mass loss after capacitor operation; coupled mass spectrometer indicated stronger signal for carbonyl and carboxyl groups. Raman spectroscopy done for electrodes in post mortem mode revealed weak band in region typical for C-O bonds. Potentiometric titration shown a significant difference in pKa distribution for fresh and exploited electrodes. Other techniques preliminarily confirm this tendency. Hence, apart from typical redox activity of dissolved hydroxybenzenes, electrochemical ‘decoration&’ of carbon electrode by quinone-type functionalities cannot be neglected.

Li-ion battery is becoming an essential component of mobile electronic devices and electric vehicles as smaller, lighter, and longer energy storage is required. Silicon is considered as one of the promising anode materials for Li-ion batteries because of its exceptional specific capacity of 4200 mAh g-1, which is about ten times that of commercial graphite anodes. However, conventional Si anodes typically suffer from rapid capacity decay due to mechanical fracture caused by large volume changes (300%) during repeated electrochemical lithium insertion and extraction. In this talk, the fracture behavior of crystalline Si nanostructures during electrochemical lithiation will be discussed in relation to volume expansion, stresses, and fracture. First, anisotropic volume expansion and anomalous fracture behavior of crystalline Si nanopillars of various axial orientations will be shown. Second, we will show that there is find facets of reaction front between crystalline Si core and Li-Si alloy shell. Then, new stress models and numerical analysis will explain how anisotropic expansion contributes to fracture of Si nanostructures during lithiation. Then, the critical size below which Si nanostructures do not fracture will be discussed and compared to amorphous Si nanopillars and germanium nanopillars. Finally, how the mechanical interaction of silicon nanopillar structures during lithiation can affect volume expansion and fracture behavior will be discussed when they are placed in confined media as electrode materials are close-packed in battery cell configuration.

This talk will provide an overview of the recent progresses in non-lithium ion battery systems at the Pacific Northwest National Laboratory. We will discuss the challenges in full Na-ion battery cells and Mg-ion battery systems, in particular the role of the interfacial reactions, and the pathways to achieve long cycle stability. We will also discuss our recent efforts to characterize and understand the transformation of the chemical species in the full Li-S batteries, and how these chemical transformations are related to the properties and performance of the batteries. Finally, we will give examples of our next generation, extra high energy density, aqueous redox flow batteries.

Thermal battery has been proposed for cabin heating and cooling on electric vehicle, which is realized by exothermic and endothermic reaction of advanced metal hydride materials. Ball-milled magnesium hydride with TiH2 as catalyst stands out as one promising material for the thermal battery due to its high energy density, fast hydrogenation/dehydrogenation kinetics and good cycle ability. Important as hydrogenation is, especially low temperature hydrogenation, there are few studies concerning the hydrogenation mechanism of this specific material, MgH2 with TiH2 as catalyst. The present work investigates the hydrogenation of this material in a wide temperature range from room temperature to 200 oC using a Sieverts type apparatus. The kinetics tests have been conducted under a deliberately designed isothermal condition to minimize the thermal effect which is usually very significant and often neglected in the literature. The absorption kinetics could be interpreted by Johnson-Mehl-Arrami model.

We have made a quantitative evaluation of the possibility to store electrical energy using ferroelectric supercapacitor built on core-shell nanoceramics. In this framework we have studied many type of ferroelectric ceramics constituted of core-shell nanoparticles by using a combination of ab-initio derived calculations, and of Landau theory. The influence of several parameters such as the maximum applied electric field during storage or the breakdown field, the permittivity of the shell, the anisotropy of particles (nanorods, nanowires) etc have been considered for different types of dielectric materials. Many new interesting features have been observed, such as new phases including vortices of polarization. Among results we have constructed a new Landau potential using both polarization and toroidal moment as order-parameters, which allows us to propose a new phase diagram of barium titanate. In fine we show that the ability of ferro-supercapacitor to store energy is in the state of the art fair but one or two order of magnitude lower than those of electrolytic-supercapacitor. However if some limitations like the breakdown field in the ceramics could be overcome, or if peculiar configurations of nanostructuration are used, middle-density ferro-supercapacitors could be built and eventually replace current hybrid supercapacitors.

Modern polypropylene film power capacitors have power densities more than two orders of magnitude greater than supercapacitors, but their use is limited to temperatures of less than 85°C. This temperature limit can be overcome by use of thin, alkali-free glass as dielectric. “Glass capacitors” are promising devices for high temperature applications in oil, gas, aerospace, hybrid electric vehicles, DC link, and pulsed power systems. This includes emerging power electronic systems using silicon carbide switches and diodes.
This work analyzes and compares various glasses with a thickness of less than 50 µm by dielectric spectroscopy, voltage breakdown, elemental analysis, and a post-mortem analysis following breakdown. It is demonstrated that glass is attractive as dielectric for a wide frequency range at 140°C.
While high temperature prototypes already exist, we demonstrate through our material and thermal analysis that further developments are required to integrate this promising device into commercial systems. It is seen that even trace amounts of alkali materials can have an impact on losses. Thermal losses must be further reduced through fundamental research into polarization mechanisms of various glass components. Furthermore, the engineering challenges of high production of thin, brittle glass must be mastered for low cost production, as discussed in this work.
Keywords: novel energy storage, glass capacitor

The new technology discussed here will enable wireless monitoring and communication with a wide variety of mobile and stationary energy storage systems, including primary and secondary batteries, such as lithium-ion batteries, capacitors, fuel cells, engines, hybrids, converters, photovoltaic cells, thermoelectric generators, gas and steam turbines, sterling engines, electrical generators and motors, fuel tanks and sub-stations. Given the safety challenges facing lithium-ion batteries in EV applications, such sensors may be particularly important to the emerging EV market. These wireless suites of sensors and readers eliminate the need for massive wiring harnesses necessary to carry sensor signals, and allows for the painless incorporation of large arrays of sensors for the control of hybrid energy systems, as well as enhanced performance, safety, and reliability. This increases operating efficiency, prolongs life of system, and increases reliability. The proposed work leverages advancements made from an earlier ARPA-e funded project that developed prototype sensors for wireless battery management systems for lithium-ion battery packs. The accomplishments that will be reported include: (1) flexible wireless tags and sensors, using Bluetooth 4.0 standard; (2) small receivers compatible with USB ports on portable computers; (3) software drivers and logging software; (4) flexible wireless controllers, also using Bluetooth 4.0 standard, essential for balancing large-scale battery packs; (4) demonstrations performed to date, with examples of the data acquired.

In this paper, a topotactic transformation from single crystalline (SC) Co3O4 or Fe2O3 cubes to CoO or Fe3O4 cubes within graphene aerogel has been demonstrated. Macroscopic, 3D, interconnected and porous graphene aerogel as isolated system promotes efficient thermokinetics reduction from Co3O4 to CoO as well as from Fe2O3 to Fe3O4 without any reducing agent. The SC-CoO/graphene and SC-Fe3O4/graphene aerogel displays superior cyclic performance and rate capability for Lithium-ion batteries compared to SC-Co3O4/graphene and SC-Fe2O3/graphene .

We report an-solid-state-supercapacitor with closely matching performance with a liquid counterpart. Conceived strategy here is controlled electro-deposition of polyethylenedioxythiophene (PEDOT) on to individual carbon fibers of porous carbon substrate and followed by intercalating the matrix with polyvinyl alcohol-sulphuric acid (PVA-H2SO4) gel electrolyte. SEM imaging shows highly intercalated gel electrolyte inside the porous substrate in which fibers are coated with PEDOT having 3-D flower morphology. Due to the 1-Dimensional growth of PEDOT over fibers even with a high mass loading of 3.78 mg/cm2 enough pores are available of gel electrolyte. Thus strategy adopted here can be used to replace liquid electrolyte from convention supercapacitors for the development of lighter, thinner, safer and cheaper electric devices. The established electrode-electrolyte interface nearly mimics the interface of the counterpart based on the liquid electrolyte. Consequently, the solid device attained a high specific capacitance (181 F g-1) for PEDOT at a discharge current density of 0.5 A g-1. This value is highest among the reported capacitance of PEDOT. Even with a high volumetric capacitance of 28 F cm-3, the solid device retained a mass-specific capacitance of 111 F g-1 for PEDOT. At 10 A /g current density, PEDOT in solid device shows 75% of its initial capacitance which is exactly matching with that experiment done in 0.5M H2SO4. Detailed Impedance analysis is used to measure the ESR, time constant and phase angle of solid device to get deep insight of the advantage of the strategy adopted here. The device also showed excellent charge-discharge stability for 12000 cycles at 5 A g-1. Performance of the device was consistent even under wide range of humidity (30 to 80 %) and temperature (-10 to 80oC) conditions. A device is fabricated by increasing the electrode area by four times was used to light an LED, which validated the scalability of the process

Flexible graphene-based supercapacitors were made using carbon nanotube (CNT) thin films as current collectors and plastic substrates as substrates. The electrode was fabricated by stacking a graphene film onto the CNT film. To form a device, two graphene-on-CNT films are used to sandwich a gelled electrolyte made of polyvinyl alcohol containing phosphoric acid. The graphene product was produced by a simple electrochemical exfoliation method. We found that without graphene, the capacitance of CNT film electrode was around 400 mu;F/cm2, while with graphene film the capacitance was largely improved to 2-3 mF/cm2. If using Au film as current collector to support the graphene film, the capacitance was in the range of 600-900 mu;F/cm2. We conclude that the graphene film is superior to CNT film in capacitive performance. When using CNT film to support the graphene electrode, the CNT felt film is not only a flexible current collector, but also has the function of improving the capacitance.

The ability to bridge the high energy density of chemical batteries with the large power capability of electrostatic capacitors has been a long sought after goal. In this regard, electrochemical capacitors (ECs) exploiting enhanced Pseudocapacitance (PC) due to surface redox reactions offers significant promise for energy storage applications. It has been seen, for example, that the charge density inherent to PC mechanisms could exceed that obtainable from the double layer capacitance in ECs by an order of magnitude. However, a drawback of PC was considered to be the lower power densities that could be harnessed.
In this work, we demonstrate high rate PC through the use of defect engineered/defective vertically aligned carbon nanotubes (VACNTs) . Such nanocarbons have the advantages of (1) high specific surface area suitable for large electrosorption as well as (2) availability of multiple, relatively homogeneous, reaction sites allowing for fast electrode kinetics .Optimized spacing between the VACNTs could allow for facile species transport.
The VACNTs were characterized through cyclic voltammetry (CV), PC of~500 F/g was obtained (at a scan rate of 0.2 V/s in aqueous electrolytes). The measured difference in anodic and cathodic peak potentials was found to be ~ 25 mV and modeled to indicate adsorption as well as diffusion limited behavior. Additionally, we have also observed an anomalous increase in the specific capacitance to values as high as 1000 F/g at very low scan rates (~1 mV/s) accompanied by an increase in the faradaic peak potential difference, indicating diffusion of electroactive ions to the defects on the nanostructure surface, with the implication of a much larger effective area of charge transfer. Through a study of the variation of the peak redox potentials with scan rate, we were able to achieve an insight into the lateral interactions between the PC contributing electrochemical species . Our studies pave the way for the development of ECs that match the energy densities of batteries.

To achieve the improved sustainability through the development of renewable and clean energy source, it is required to understand the operational mechanism of the complex materials and systems of renewable energy systems to improve their own properties. However, such materials or systems often consist complicated Multiscale/Multiphysics natures characterized by energy inter-conversion processes, sequential electron transportation, subtle balance of thermodynamic driving forces, ill-defined structural characteristics, etc.; thus, it is often difficult to unveil the underlying mechanism and improve the desired material properties. For the systematic improvement with tailored material properties, we use first-principles based multi-scale computational methods to understand, predict, and design the material structures and processes.
In this talk, I discuss our recent work demonstrating how the computer simulations can aid controlling mechanistic pathways of complicated chemical reactions of lithium air battery system. Particularly, we investigated the reaction mechanisms in the Li-O2/CO2 cell under various electrolyte conditions using quantum mechanical density functional theory (DFT) simulations coupled with Poisson-Boltzmann implicit solvation method to mimic the electrolyte environment. Our most important finding is that the subtle balance among various reaction pathways influencing the potential energy surfaces can be modified by the electrolyte solvation effect, and thereby the final discharge product can be controlled by the choice of electrolyte, which is further confirmed by experiments. We believe that the current mechanistic understanding of the chemistry of CO2 in a Li-air cell and the interplay of CO2 with electrolyte solvation will provide an important guideline for developing Li-air batteries. Furthermore, the possibility for a rechargeable Li-O2/CO2 battery based on Li2CO3 may have merits in enhancing cyclability by minimizing side reactions.
[1] H.-K. Lim et al., J. Am. Chem. Soc., 2013, 135 (26), pp 9733-9742

Non-aqueous Li-air batteries have attracted considerable attention in recent years, in view of its capability to deliver a much higher gravimetric energy density than all other energy storage systems.[1-3] Nevertheless, the problems such as poor cyclability and low electrical energy efficiency hinder their practical application. To overcome these obstacles, substantial efforts have been made to search for stable electrolytes against lithium superoxide and peroxide, optimized configuration of oxygen diffusion cathodes, screening appropriate ORR/OER catalysts as well as Li anode protection and so on. In our work, the cyclability of Li-O2 batteries was greatly enhanced by controlling the cathode reaction. Using intentionally selected cathodes (vertical aligned carbon nanotubes grown on stainless steel meshes), nucleation, growth and decomposition processes of Li2O2 during cycling are visualized.[4,5] Li2O2 and carbonates simultaneously formed on the cathode surfaces are identified according to distinctive morphologies. On basis of the deeper understanding of the reaction mechanism, the battery performance has been greatly improved by control of charge and discharge protocols.[6] In addition, we also explored the origin of large overpotentials during cycling, which is difficult to eliminate, although enormous efforts have been put into this research. [7]
In contrast, a recently reported rechargeable sodium oxygen (Na-O2) battery exhibited a low overpotential (< 200 mV), yielding an electrical energy efficiency above 90%.[8] The performance of Na-O2 batteries significantly depends on the reaction products (NaO2, Na2O2, Na2O2 2H2O and Na2CO3) by using different electrolytes (PC- and TEGDME-based ones), operation conditions and cathode configurations.[9,10] In addition to these fundamental perplexities, the so-far reported Na-O2 batteries showed poor cycling and rate performance. In order to clarify the battery chemistry and improve the electrochemical performance, we investigated the Na-O2 batteries under appropriate operating conditions.
[1] G. Girishkumar, B. McCloskey, A. C. Luntz, S. Swanson, W. Wilcke, J. Phys. Chem. Lett. 2010, 1, 2193-2203.
[2] P. G. Bruce, S. A. Freunberger, L. J. Hardwick, J.-M. Tarascon, Nat. Mater. 2012, 11, 19-29.
[3] C.-X. Zu, H. Li, Energ. Environ. Sci. 2011, 4, 2614.
[4] W.G. Fan, Z.H. Cui and X.X. Guo, J. Phys. Chem. C, 2013, 117, 2623.
[5] Z.H. Cui, W.G. Fan and X.X. Guo, J. Power Sources, 2013, 235, 251.
[6] X.X. Guo and N. Zhao, Adv. Energy Mater. 2013, DOI: 10.1002/aenm.201300432.
[7] N. Zhao, C. L. Li and X.X. Guo, Energy Technology 2013, submitted.
[8] P. Hartmann, C. L. Bender, M. Vra#269;ar, A. K. Dürr, A. Garsuch, J. Janek and P. Adelhelm, Nat. Mater. 2013, 12, 228-232.
[9] Q. Sun, Y. Yang and Z.-W. Fu, Electrochem. Commun. 2012, 16, 22-25.
[10] J. Kim, H.-D. Lim, H. Gwon and K. Kang, Phys. Chem. Chem. Phys. 2013, 15, 3623.

In the light of the recent discovery of rechargeable room-temperature sodium superoxide (NaO₂) batteries [1], a deeper understanding of the electronic properties of NaO₂ has become of broader interest. We investigate the electronic structure of NaO₂ using the framework of density functional theory and employ a hybrid functional approach for the exchange and correlation interaction. The disordered pyrite structure of the NaO₂ room-temperature phase is modeled by taking into account various superoxide orientations in our computations. The band structure calculations indicate that NaO₂ is an insulator with an energy gap of 2.4 eV and that different superoxide alignments lead to a broadening of the conduction band. We compare our results to recent experimental investigations regarding the conductivity of NaO₂.
[1] P. Hartmann, C. L. Bender, M. Vra#269;ar, A. K. Dürr, A. Garsuch, J. Janek, and P. Adelhelm, Nature Mat. 3486 (2012)

Li-O2 battery systems have attracted immense recent research interest due to their potential for replacing Li-ion batteries in next-generation vehicular applications. This focus has been stimulated by the exceptionally high capacities (in excess of >1000 mAhg-1) exhibited by a number of Li-O2 battery architectures to date. Despite much promise, these batteries often show poor cycle life due to the instability of carbon based cathodes and organic electrolytes. It thus becomes crucial for the formation and decomposition of Li2O2 to be the only electrochemical processes.
While carbon is a promising cathode material in terms of cost and low density, its instability with respect to the formation of Li2CO3 and poor catalytic activity towards the OER have led to the development of many bi-functional catalyst systems for Li-O2 battery cathodes. Metal oxides in particular seem to be well placed as efficient bifunctional catalysts which exhibit high ORR and OER activity while retaining the lost costs crucial to wide scale implementation. MnO2 has attracted significant interest as a catalyst material for Li-O2 battery cathodes and has been shown to exhibit improved round trip efficiencies in comparison to pure carbon cathodes. However, few investigations have focussed on the influence of MnO2 on the morphology of the discharge products for Li-O2 cathodes.
In this study, we have investigated the morphology of the discharge products formed on MnO2 nanorod based cathodes within various electrolytes. By conducting tests in parallel using Super P carbon cathodes (under identical current densities), it was possible to directly gauge the role of MnO2 in determining discharge product morphology. Galvanostatic cycling experiments also showed that MnO2 nanorods led to significantly higher charge capacities than those exhibited by pure carbon cathodes. This study gives important insight into the mechanism of MnO2 catalysts for Li-O2 battery cathodes and also illustrates the importance of electrolyte choice for Li-O2 battery operation.

Lithium oxygen battery is an intriguing system as it provides a unique platform to investigate many interesting fundamental phenomenon spanning from catalytic reactions, defect chemistry, oxygen reduction and evolution, and even radical reactions [1, 2, 3]. However, the key challenge, e.g. the stable electrolyte has still not been identified leading to the intensive parasitic reactions initiating on the carbon substrates during both discharge and charge processes [4]. The end result is the continuous increase of cell impedance accompanied by the depletion of the electrolyte and accumulation of insulating Li2O2 and byproducts. In most of the reported work where carbon has been used as the air electrode, high surface area carbon with high mesopore volume is usually preferred [5, 6] in order to deliver high capacity. The high surface area carbon, unfortunately accelerates the electrolyte decomposition as well which makes it difficult to understand the nucleation and growth of Li2O2 on carbon surface. This work takes advantage of conductive graphite with low surface to simplify the Li-O2 system. The deposition and morphology evolution of Li2O2 on graphite-based air electrode during repeated cycling will be explored and discussed in detail.
Reference:
[1] A. Débart, J. Bao, G. Armstrong, and P.G. Bruce. Journal of Power Sources 174 (2), 1177 (2007).
[2] Y. Lu, Z. Xu, H.A. Gasteiger, S. Chen, K. Hamad-Schifferli, and Y. Shao-Horn. Journal of the American Chemical Society 132 (35), 12170 (2010).
[3] R.S. Assary, J. Lu, P. Du, X. Luo, X. Zhang, Y. Ren, L.A. Curtiss, and K. Amine, ChemSusChem 6 (1), 51 (2013).
[4] E. Nasybulin, W. Xu, M.H. Engelhard, Z. Nie, S.D. Burton, L. Cosimbescu, M.E. Gross, and J. Zhang. The Journal of Physical Chemistry C 117 (6), 2635 (2013).
[5] J. Xiao, D. Wang, W. Xu, D. Wang, R.E. Williford, J. Liu, and J. Zhang. Journal of The Electrochemical Society 157(4), A487 (2010).
[6] J. Xiao, D. Mei, X. Li, W. Xu, D. Wang, G.L. Graff, W.D. Bennett, Z. Nie, L.V. Saraf, I.A. Aksay, J. Liu, and J. Zhang. Nano letters 11(11), 5071 (2011).

The Juvenile Salmon Acoustic Telemetry System (JSATS) project supported by the U.S. Army Corps of Engineers, Portland District, has yielded the smallest micro-acoustic transmitter commercially available to date. To study smaller fish and permit implantation by injection using a needle, the JSATS micro-acoustic transmitter was reduced in weight and volume. This study focuses on the development of a micro-battery design based on lithium/carbon monofluoride (Li/CFx with x = 1) chemistry. A steady high-rate pulse current with required lifetime was achieved while the weight and volume of the battery was significantly reduced. The newly designed micro-batteries have intrinsically lower impedance than the batteries currently used in JSATS transmitters, leading to significantly improved electrochemical performances within a wide operating temperature range from -5°C to 25°C. The fundamental science related with fluorination chemistry will also be discussed to tune the power/energy ratio for various requirements for practical applications.

Successful use of hard templated carbons as a crucial component in new electrochemistry systems like Li-Sulfur renewed interest in this long known material class.
Almost all of these materials have meso- and small macro pores in the range up to about 100 nanometers with significant additional micro porosity.
Here, we report on the improvement of cell kinetics in Lithium-ion cells by the use of hard templated porous carbons with dominant macroporosity between 100-1000nms.
Experimental
NMC cathode slurry formulations have been mixed and homogenized with carbon black, PVDF binder and further addition of different amounts of a hard templated carbon sold as Porocarb LD2N by Heraeus.
The cathode slurry has been coated on Al foil with standard equipment and subsequently calendared to achieve the high electrode density required by high-energy cells.
The porous particles within the electrode volume retained their initial porosity and pore size distribution whereas the remaining volume consisting of active materials and conductive additives was densified to a lower level of porosity. Thus, a smooth electrode could be produced with local areas of high porosity and macro pores.
The cathodes have been assembled to half cells and cycled at different C rates to observe the effects of the new electrode structure on Lithium-ion transport kinetics.
Results
Electrode cycling shows improved effective Lithium-ion conductivity of the electrodes with different areas of porosity. We show a substantial capacity improvement during cycling at medium to high C rates in comparison to a standard cathode without additive.
In a second step we increased the coating thickness of the electrodes to check the thickness dependency of the effect.
We can show that with small addition of the macroporous carbon particles the electrode thickness can be at least doubled without losing discharge rate performance of the cell.
Creating local areas of high porosity within the electrode with porous carbons therefore finally leads to improved volumetric and gravimetric energy densities.
Furthermore, manufacturing costs from coating to cell assembly can be significantly lowered due to increased electrode thickness.

Si, one of the most promising anode materials with high theoretical capacity (3,750 mAh g-1) for Li ion batteries, suffers from volumetric change-induced pulverization and surface solid electrolyte interphase (SEI) formation, both of which lead to capacity fading during the charge/discharge cycles. In this regard, cladding of Si with various materials such as carbon and silicon oxide has been adopted to prevent these problems. However, detailed conduction path of Li ions and electrons inside the cladding layer have not been studied. Herein, we designed novel core-sheath composites in which Si nanoparticles and conductive indium tin oxide (ITO) nanoparticles are filled inside carbon hollow fibers. Encapsulating Si nanoparticles by carbon hollow fiber allows for accommodating significant volumetric change and for preventing the continual growth of SEI at surface. Simultaneously, inner ITO nanoparticles assist not only the electronic conduction but also the ionic conduction of Li ions through Li2O which could be generated via conversion reaction of ITO. These well-engineered Si-ITO core/carbon sheath composites enable us to achieve excellent capacity retention and better rate capability than Si core/carbon and Si-carbon core/carbon composites. Electrochemical impedance spectroscopy (EIS) also exhibits the enhanced electrochemical reaction rate due to the presence of ITO that behaves as an electronic-ionic mixed conductor.

Power generation and storage for microelectromechanical systems (MEMS), miniaturized biomedical devices, sensors and integrated on-chip components, can significantly benefit from the fabrication and integration of planar thin film supercapacitors. Here we report the room temperature growth of nanostructured carbon (ns-C) thin films and nanocomposites with high surface area by supersonic cluster beam deposition (SCBD). SCBD consists in a random stacking of low kinetic energy nanoparticles producing films with very low-density and high porosity. The use of supersonic expansions for cluster deposition allows to obtain very high deposition rates and highly collimated beam (divergence <20 mrad) which are suitable for the deposition of patterned nanostructured films by using stencil masks on substrates kept at room temperature. The synthesis of porous carbon via SCBD presents several advantages, such as the compatibility with temperature sensitive substrates and with standard planar microtechnology processes, that may be pivotal toward the development of miniaturized, planar and flexible supercapacitors. The avoidance of binders to hold the ns-C to the current collector is another advantage of technological relevance.
The electric double layer capacitance of ns-C films (thickness variable in the range of 140divide;500 nm) soaked in different ionic liquids is investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The inclusion of metal clusters in the porous ns-C matrix is also demonstrated as a route towards the synthesis of nanostructured carbon-based materials with optimized electric transport properties. Embedded metal clusters significantly affect the ns-C properties and promote modification of the carbon structure upon thermal treatments. The viability of metal:carbon nanocomposites as active material in electrochemical double layer (EDL) energy storage applications is presented by the study of the EDL formed at the interface of the nanocomposites and aqueous electrolyte. Finally, the fabrication of a planar supercapacitor based on cluster-assembled nanostructured carbon (ns-C) thin films and ionic liquid as electrolyte is demonstrated [1].
[1] LG Bettini, M Galluzzi, A Podestagrave;, P Milani, P Piseri. Planar thin film supercapacitor based on cluster-assembled nanostructured carbon and ionic liquid electrolyte. (2013) Carbon doi: 10.1016/j.carbon.2013.03.011

Supercapacitors (SC) are believed to play a vital role in the future development of Hybrid Electric Vehicles (HEV) as well as Electric Vehicles (EV). Owing to their high power density supercapacitors can act as a power source during peak performances, e.g. acceleration, thus leading to reduced fuel consumption in HEV. Furthermore is the combination with fuel cells (FC) very appealing where SC can deliver the required power density and FC the energy density.
In the easiest case a SC consist of two identical porous carbon electrodes. It is known that a high surface area in combination with a well-defined porosity (network of micro- and mesopores) is beneficial for a high capacitance. Amongst various methods to develop high surface areas (e.g. hard/soft templates, activation etc.) salt templating is a very attractive process where a high carbon yield can be achieved and only water is needed to etch the template.
The SC performance can be enhanced by introducing heteroatoms (e.g. nitrogen) into the carbon framework. Nitrogen leads to higher electrical conductivity, thus better performance under high current densities and can give rise to a so called pseudocapacitance (fast faradic reactions).
We here present a solution based synthesis for porous carbons. We were able to introduce various hetero atoms into the carbon framework achieving both a high carbon yield as well as high and tunable porosities. The supercapacitor performance of the carbon materials in aqueous and non-aqueous electrolytes will be presented.

Conventional electric double layer capacitors (EDLC) with activated carbon electrodes are able to deliver more power but less energy than Li-ion batteries. In order to combine the advantages of Li-ion batteries and supercapactiros, an asymmetric supercapacitor was fabricated where positive electrode (such as: carbon based composite) stores charges non-faradaically, and negative electrode (such as: Li4Ti5O12) stores charges through fast reversible intercalation of lithium ions. To further enhance the power and energy density, 3D structures were constructed based on photolithography. Electrostatic spray deposition (ESD) was used to integrate active materials onto 3D electrode arrays. The resulting electrodes were characterized by X-ray diffraction and scanning electron microscopy. Electrochemical performances were characterized by cyclic voltammetry (CV), galvanostatic charge-discharge and rate capability tests. Detailed results will be presented in the conference.

Li4Ti5O12 (LTO) is one of the most promising anode materials for lithium-ion batteries. In this study, porous LTO thin films were prepared by electrostatic spray deposition (ESD). Their electrochemical performance was characterized by cyclic voltammetry (CV) and galvanostatic charge-discharge. Our results reveal that the LTO electrodes exhibit high rate capability and long cycle life. In the potential range of 0.05-3 V, the LTO electrode delivers reversible specific capacity of 357,307, 270, 207, 153 and 98 mAh g-1 at different current rates of 0.5 C, 1 C, 2 C, 5 C, 10 C and 20 C, respectively. After high C rate test, the electrode was tested at 2 C for 100 cycles. No capacity decay was observed even after testing at harsh condition. Detailed results will be presented in the meeting.

A multi-dimensional thermal and electrochemical coupled model is developed for
Li-ion batteries. The model is capable of predicting the cell internal temperature distribution as well as the average cell temperature evolution.
Numerical simulations are performed for a different-size Li-ion cell for electric vehicle applications. The coupled model predictions indicate the importance of thermal-lectrochemical coupling for accurate prediction of the thermal and electrochemical behaviors of Li-ion batteries. Numerical results show that large temperature gradients develop along the cell height, causing severe non-uniformity in both electrode reaction rate and electrolyte concentration distributions. Evolutions of cell potential and temperature are found to be greatly affected by the thermal environment and the cell aspect ratio.

Recent advances in dendritic nanotechnology have given rise to a myriad of applications in the areas of environment, biomedicine and energy. Our research offers the possibilities of using these nano-polymers in high energy density applications such as in lithium-air (Li-O₂) and lithium-sulfur (Li-S) batteries. Li-O₂ batteries have attracted significant attention around the world due to their extremely high theoretical energy densities. However, their practical applications have been limited by a number of technical challenges such as poor cyclability and low Coulombic efficiency. Recently, we have developed a novel dendritic polymer-based heterogenous electrocatalyst that has the potential to improve the cycling capability of Li-O₂ batteries. Poly(amidoamine) (PAMAM) dendrimers - highly branched architectures with exceptional physicochemical and mechanical properties, have been used as hosts to encapsulate monodispersed metallic ruthenium (Ru) nanoparticles and used as catalysts in the air electrode for Li-O₂ batteries. The dendrimers stabilized the Ru nanoparticles as well as ensured the availability of the entire nanoparticle surface for catalysis. The application of these dendrimer-encapsulated nanoparticles (DENs) significantly reduced the charging over-voltage. They also improved cyclability of Li-O₂ cells by nearly three times as compared to the electrodes using Ketjen Black (KB) carbon without any catalysts. The electrochemical performance of DENs was further analyzed using a glassy carbon electrode. The metallic nanoparticles were characterized using transmission electron microscopy and X-ray photoelectron spectroscopy. The discharged electrodes were characterized by X-ray diffraction to qualitatively analyze the discharge products. Furthermore, the porous DENs themselves showed some capacity towards hosting lithium peroxide discharge products, thus attributing functionality to these nanoparticles. The effects of DENs on the cell performance can be attributed to the good dispersability of the nano-sized Ru nanoparticles within the dendrimer template while still keeping the surface of catalysts unpassivated.
In the case of Li-S batteries, the charge/discharge reaction involves the creation of highly soluble polysulfide intermediates in electrolytes. We will discuss the application of dendrimer based solid-state electrolytes at room temperature in Li-S batteries to arrest the self-discharge of sulfur cathode and thus improve electrochemical cycling of the cells. The three-dimensional, flexible structure of the dendrimer enables a continuous medium for fast Li+ transport. Furthermore, the high glass transition temperature of dendrimers makes them amorphous at room temperature and thus, improves ionic conductivity without the need of plasticizers. Thus, the promising application of dendritic nanotechnology may provide attractive solutions to the challenges in high-energy storage systems.

Energy storage characteristics of Li-ion batteries are limited by the relatively low gravimentric and volumetric capacities of intercalation-type electrodes[1-3]. In this work, we report on the synthesis and characterization of iron fluoride (FeFx)/ nanoporous carbon composites for high capacity conversion-type Li-ion battery cathodes with good cycle stability. In contrast to many prior studies, which involved independent synthesis of FeF2 or FeF3 followed by their mechanical mixing with carbon powders[4, 5], we demonstrated synthesis of FeFx nanoparticles within a nanoconfined space of carbon pores using liquid precursors. After infiltration, thermal treatment allowed for the transformation of the precursor to FeFx nanoparticles. The size and distribution of FeFx were regulated by the porous structure of the nanoporous carbon host. The high precision of the microstructure control allowed us to achieve a high capacity of up to ~530 mAh/g in combination with excellent reversibility and rate performance. The impacts of annealing temperature and pore size distribution of the carbon host on the electrochemical properties of the composite cathode have been studied systematically. In this talk we will discuss the structure-property relationships related to such composite cathodes. This work is a step closer to the practical applications of conversion-type cathode materials, such as FeFx, in Li rechargeable batteries.
References
1. Goodenough, J.B. & Kim, Y. Challenges for Rechargeable Li Batteriesdagger;. Chemistry of Materials 22, 587-603 (2010).
2. Ellis, B.L., Lee, K.T. & Nazar, L.F. Positive Electrode Materials for Li-Ion and Li-Batteriesdagger;. Chemistry of Materials 22, 691-714 (2010).
3. Li, H., Wang, Z., Chen, L. & Huang, X. Research on Advanced Materials for Li-ion Batteries. Advanced Materials 21, 4593-4607 (2009).
4. Amatucci, G.G. & Pereira, N. Fluoride based electrode materials for advanced energy storage devices. Journal of Fluorine Chemistry 128, 243-262 (2007).
5. Pereira, N., Badway, F., Wartelsky, M., Gunn, S. & Amatucci, G.G. Iron Oxyfluorides as High Capacity Cathode Materials for Lithium Batteries. Journal of the Electrochemical Society 156, A407 (2009).

Novel organic/inorganic hybrid glasses have been actively studied for a variety of applications. However, normal hybrid silica provided by a bulk mixing process often shows limitations; the resulting materials' properties prepared by the simple mixing technique maintain their original properties of the individual components and thus significantly influenced by the properties of each component. To overcome the limitations, an alkylene-bridged hybrid glass mixed at the molecular level was designed and then synthesized to create new properties that individuals don&’t have. After a co-polymerization of the alkylene-bridged sol-gel monomer and a sol-gel processable chromium precursor under acidic condition, a highly compressed, thin glassy film was prepared. In laser experiments, the optical transparent hybrid glassy film with high compressibility has shown a strong ‘acoustic response&’ as much as a liquid. The diffraction efficiency and absorption light efficiency (45 %) of the Cr dope glass was higher than that (25 %) of methanol; which means, the compressibility of the doped glass is as effective as liquid. Therefore, it can be served as a ‘HEAT GENERATOR (ENERGY- STORAGE MATERIAL)&’; as a result, the heat gets transferred into expansion or compression wave effectively. This is a new phenomenon that can develop novel energy-storage materials with a good optical clarity. It can be also integrated small patterns on substrates for the fabrication of optoelectronic devices.

In this investigation, thin films of polyvinylidene fluoride (PVDF) containing nanoparticles of the ceramic titanium dioxide (TiO₂) are synthesized using physical deposition techniques. This composite material shows promise for possible use as the dielectric in capacitors for energy storage. This composite approach allows for the integration of complimentary features such as high dielectric permittivity from the integrated nanoparticles and high breakdown strength from the polymer matrix, resulting in a greatly enhanced energy density. Co-deposited films with a TiO₂ concentration of up to 10% have been synthesized. Elemental mapping from EDS and intermittent contact AFM show that the disspersion of the nanoparticles is homogeneous in the films. Additional information from XPS and SEM concerning the structure of the films is presented for different deposition conditions. Furthermore, parameters such as the dielectric constant and the breakdown voltage are given.

Self-powered microsystems as an alternative to standard systems powered by electrochemical batteries are taking a growing interest. The energy harvested but not immediately used by the system has to be stored in a battery. Although these systems aim to replace electrochemical batteries via self-powering, paradoxically the storage step is performed yet by an electrochemical battery.
In this work, we propose a different method to store the energy harvested from the ambient which is performed in the mechanical domain and, consequently, allows leaving aside the use of supercapacitors or electrochemical batteries. Our mechanical storage concept is based on a spring which is loaded by the force associated to the energy source to be harvested. This load is maintained with a ratchet potential. Such a mechanical battery could maintain the stored energy for a longer time than the electrochemical batteries based on charge storage, which suffer a certain discharge during time. Additionally, depending on the material used the system could achieve high values of stored energy density [1].
Our first approach is based on pressing an array of fine wires grown vertically on a substrate surface. This approach fits very well with the self-powered systems based on ambient energy harvesting which normally are based on, or one of their main parts are, mechanical resonators. For the fine wires based battery, we have chosen ZnO fine wires due to the fact that they could be grown using a simple and inexpensive process named the hydrothermal process. We have done several experiments changing temperature, solvent concentrations and initial pH of the solution in order to determine the best growth conditions of the fine wires for our purposes. From the geometrical dimensions of the fine wires obtained in the optimal growth conditions we have calculated the maximum storing energy capability using linear elastic theory. For that purpose, we have considered that the maximum load we can apply to the system is given by the one corresponding to the linear buckling of the fine wires. Taking the best statistical approximation we have obtained a critical strain value of epsilon = 10.6 % and a maximum average stored energy density of U = 91.2 MJ/m3. These results were confirmed by using COMSOL FEM software simulations.
The second approach is based on polymers which change their dimensions by thermal or optical actuation. The battery, in this case, is not based on fine wires but in microfabricated silicon springs (using bulk micromachining) directly in contact with the polymer. By increasing system temperature or applying UV light, the polymer is contracted loading the silicon spring. We have fabricated a demonstrator of this load system and we have achieved an energy density stored of 700 J/m3.
[1] F.A. Hill, T.F. Havel, et al. “Modeling mechanical energy storage in springs based on carbon nanotubes” Nanotechnology 20 (2009) 255704, 12pp.

polyethylene(PE) separator is coated by coating solution containing polysulfone(PSF), tetrahydrofuran(THF)as solvent, and 1,4-butandiol as nonsolvent via nonsolvent-induced phase separation(NIPs) process. The effects of the nonsolvent content on the morphology of the coating layer were observed. The final pore size increased as nonsolvent ratio decreased when PSF, THF ratio is fixed. It increases thermal stability of PE separator by coating with PSF. Also, Al2O3 nano particle is used for more enhancing the thermal stability of the separator. By using Polyvinylpyrrolidone(PVP), it makes Al2O3 nano particle more dispersed in the PSF solution. And γ-MPS(γ-Methacryloxypropyltrimethoxysilane) is used as coupling agent to improve interface property of nano particle. By adding organic-inorganic composite to the PSF solution, it enhances more thermal stability than the PSF coating, while air permeability of the separator is deceased. Changes in the thermal stability and air permeability depended on the morphology of the coating layer and organic-inorganic composite.

Predicting Capacity of Hard Carbon Anodes in Sodium-Ion Batteries Using Porosity Measurements
Sodium-ion batteries (SIBs) hold the potential of achieving key breakthroughs in the field electricity storage. Their similarities with lithium-ion batteries (LIBs) coupled with their low cost render them very attractive for grid-level energy storage. However, the larger ionic radius of Na⁺ prohibits the transfer of technologies from LIBs to SIBs. This is particularly true in the case of the anode, as Na⁺ cannot readily intercalate graphite based materials. Consequently, there have been many attempts at developing suitable anode candidates. Such efforts have included carbon-based materials, phosphorous, metal oxides and various types of alloys.
Herein, we explore sucrose based hard carbon as an anode material. Hard carbon has already shown promise: several research groups such as Dahn et al. Alcántra et al. and Palacin et al. have demonstrated reversible capacities of around 300mAh g^-1. Furthermore, these are easily synthesized from any organic sources, cheap and non-toxic.
Through our experiments, we are able to derive a model which shows that reversible capacity is inversely related to pore volume/surface area. This allows us to accurately predict the performance of hard carbon based anodes based porosity measurements as obtained through N₂ sorption. Furthermore, we are able to demonstrate one of the highest reversible capacities for hard carbon anodes obtained to date of 335 mAh g^-1 along with 500+ cycles of long term cycling at a current rate of 300 mA g^-1. Our findings give much new insight of sodium ion storage mechanism in hard carbon and in the use of hard carbon as an anode material in SIBs.

Nickel hydroxide at copper core-shell nanobelts (Ni(OH)2@CuNBs) with high surface area, good conductivity and multiple oxidation states are designed as electrochemical pseudo-capacitor materials for potential energy storage devices. The growth of CuNBs on carbon/Aluminum (Al) electrode is achieved by a simple electrochemical reduction of CuCl2 by Al in aqueous HNO3 solution and cetyltrimethylammonium chloride (CTAC) at 290 K.1 The CuNBs with several tens of um in length and a thickness of ~ 20 nm grows densely to form an interlacing net which will serve as an excellent nanoscale current collectors. The uniform Ni(OH)2 nanosheets shell is coated onto CuNBs by the second step galvanic displacement of Al again in NiSO4 mediate. The electrochemical measurements were carried out by a three-electrode system in 1 M KOH electrolyte. The optimum Ni(OH)2@CuNBs electrode delivers a high specific capacitance (Csp) of 2663 F g-1 at 10 A g-1 and a good rate performance of 2376 F g-1 even at 100 A g-1. The support of CuNBs is important for the enhanced rate performance of our electrode, which provides a large surface area and fast electron transport. The long-term cycling performance at 30 A g-1 shows a Csp of 1627 F g-1 (68% remains) after 1000 cycles. This work suggest that Ni(OH)2@CuNBs is promising for the next generation high-performance supercapacitor.
Keywords: Copper, Nickel hydroxide, Nanobelts, Galvanic displacment, Supercapacitor
Reference:
(1) Huang, T.-K.; Cheng, T.-H.; Yen, M.-Y.; Hsiao, W.-H.; Wang, L.-S.; Chen, F.-R.; Kai, J.-J.; Lee, C.-Y.; Chiu, H.-T. Langmuir 2007, 23, 5722- 5726

In this study, we reported a low-cost and easy scale up method to prepare a conductive and flexible TiOxNy sheet with mesoporous structure as an electrochemical electrode for energy storage. TiOxNy sheets were fabricated by nitridation of titanate sheets under an ammonia atmosphere at 600~800 oC. The TiOxNy sheets were composed of randomly stacked high density fibers with several micrometers in length, resulting in a dense network which leads to the flexibility of sheets. The O/N ratio, porosity and conductivity of TiOxNy sheets can be controlled by the temperature and duration of nitridation process. TiOxNy sheets exhibits good specific capacitance performance (127.5 F g-1, 2 M H2SO4) with a high O/N ratio of 4.55 and a large specific surface area (58.9 m2/g). These suggested that TiOxNy may be employed as a potential electrode material for further electrochemical applications.

We demonstrate a simple method for preparing porous, hollow microspheres composite consisting of nanoscale Fe3O4 along with an amorphous carbon. This facile process involves the bacteria-templated synthesis of FeO(OH) nanostructures that are anchored on a bacterial surface used as templates at room temperature, and subsequent template removal process by thermal treatment at 400 oC in Ar. The spherical Microccocus lylae bacteria are used as soft-templates. The as-synthesized FeO(OH) nanostructures exhibit a uniform deposition showing flower-like structures of a hierarchical formation with high mesoporous properties, such 2D-nanoflakes that are actually comprised of extremely tiny FeO(OH) nanoparticles, on the bacterial templates. After heat-treatment at Ar atmosphere, hollow microspheres are observed to be Fe3O4@amrophous carbon that can be derived from the bacteria, and retain original spherical shapes. Besides, they show higher porosity with a large BET surface area (~ 60 m2 g-1). Additionally, bacterial removal process is also explored in air at the same temperature. The Li-electroactivities of all samples as anode materials are determined by CV profiles. Furthermore, we also evaluate the series of electrochemical performances such as cycle stability and rate capability. In particular, the Fe3O4@amorphous carbon composite anode indicate improved electrochemical performance with a specific capacity of about 500 mAh g-1 after 150 cycles, compared to other anodes, and this result can be further discussed based on the enhanced electrical conductivity as well as structural properties.

Nanomaterials are commercially used in electrochemical storage devices such as lithium-ion batteries. The latter are inevitable parts of high tech devices like portable devices, sensors and biocompatible items. In a typical cell, the active electrode materials are coated on thick current collectors and carbon additives increase their electronic conductivity.
Today, the metal current collector on the anode side is a 10 µm thick copper sheet, representing a heavy component in a lithium-ion cell. Its mass is comparable to the anode active material and accounts for around 10% of the total weight of the cell.[1] Although intense efforts have provided lighter electrode materials with high capacities, there is still sufficient space to reach higher energy densities if it would be possible to reduce the weight of the current collector.
Porous metals have received recently increased attention as catalysts, filters, lightweight and electrode materials.[2] However, there remain still two challenging tasks in the synthesis of porous metals: 1) an exact control of the morphology and 2) pore sizes in the submicron range. Up to now, it was not possible to gain a precise control over the pore size and their distribution within the metal coating like in mesoporous silicates, which display interior channels of exactly defined dimensions on the nanometer scale.
In this work, I will demonstrate a precise control over the morphology and porosity of nickel thin films on the nanoscale. Porous nickel nanostructures in the form of hollow spheres and tubes were synthesized by electrochemical co-deposition and subsequent etching. These hierarchically ordered nanostructures may find potential application as building blocks for electrochemical devices, such as current collectors in energy storage systems.[3]
[1] L. F. Cui, L. B. Hu, J. W. Choi, Y. Cui, ACS Nano 2010, 4, 3671-3678.
[2] A. R. Studart, A. Nelson, B. Iwanovsky, M. Kotyrba, A. A. Kundig, F. H. Dalla Torre, U. T. Gonzenbach, L. J. Gauckler, J. F. Loffler, J. Mater. Chem. 2012, 22, 820-823.
[3] A. Slabon, F. Krumeich, F. Wächter, R. Nesper, submitted.

Li2S cathodes are extremely attractive due to their high theoretical capacity (1166 mAh/g), low cost, and compatibility with non-lithium metal anodes. However, the lithation/delithiation reaction pathway between Li2S and S includes the formation of soluble polysulfides, which leads to poor cycle life. One strategy to improve cycle life is to coat Li2S particles with a protective layer, preventing polysulfide dissolution. We present a solution based route to a new family of coatings for Li2S, which improve both capacity retention and rate performance.
Leveraging a proprietary high-throughput synthesis workflow, Wildcat has demonstrated the reactive deposition of an inorganic coating on Li2S particles. The coating method, based on the reaction of precursors with Li2S, is shown to be a general method and used to deposit coatings with different compositions on the surface of Li2S. Galvanostatic cycling of coated cathodes show >90% capacity retention between cycles 1 and 3 and 20% improvement in 1C rate performance.

This work reports a numerical and analytical evaluation in time and space of Li polysulfides shuttling process, concentration of ion in electrolyte, concentration of soluble high-order polysulfide on the electrodes surface, and concentration of diffused Li into the cathode. As a result our model is able to predict prevalent specifications like capacity fade, current density and optimum concentration of species to improve battery operation. To simplify complexity of the modeling we consider: i) the rate of transportation of species is same for those are producing at the same time either on anode or cathode side; ii) only complete discharge condition which results in having low-order polysulfide as the only final products at the end of discharge process. From reported experimental data we can understand that shuttling mechanism in the electrolyte is a primary factor in battery performance. We then define equations to calculate concentration of soluble high-order polysulfide on the surface of electrodes at any time during charge and discharge. Knowing the concentration of polysulfide on the surface of cathode, inside the cathode and also in the electrolyte as function of time opens a way to numerically compute the concentration of Li-ion available to contribute to both battery capacity and to the formation of high-order polysulfide which provide an unwanted coated layer on the anode surface.
Solving a set of electrochemical diffusion equations in the electrolyte and applying boundary condition on electrodes surfaces result in having concentration of Li-ions as function of time and space over electrolyte bulk. We are introducing two separate mechanisms for discharge and recharge process in which they properly satisfy initial conditions, boundary condition and continuity of cycling process. Time-dependent 1D expression for concentration of ions yields an expression for ionic flux, current density and subsequently coulometric capacity, coulombic efficiency, energy capacity, battery cycling life and internal resistivity. Our numerical analysis results are compared with previously reported experimental works.
Additionally, effect of porosity on the cathode surface to confine soluble high-order polysulfide inside the electrode is considered and a one-dimensional modeling is presented to show advantages of porosity to lessen capacity fading after tens of cycling.
We will present for the first time a space and time dependence theoretical Li-S battery model. We will report on several configurations and numerically evaluate specification of battery such as the specific energy, loss of capacity per cycle, lifetime (number of cycles), maximum discharge current, and compare them with some available reported experimental data. Moreover, 1D model for porous electrode is presented and capability of that mechanism to predict battery operation will be discussed.

To find electrode materials suitable for Na-ion batteries, several types of materials have been extensively studied, and recently pyrite-FeS₂ have attracted much interest as a cathode material [1]. However charge and discharge reactions in Na/FeS₂, that are governed by a structural conversion mechanism, are not fully understood yet especially concerning intermediate states involved in the reactions. By using first-principles calculations for probable phases in Na/FeS₂ conversion reactions, we theoretically estimate electromotive forces (EMF) that characterize battery performances. To study local-structure changes during the reactions, we calculate x-ray absorption spectra (XAS) of Na/FeS₂ before and after discharges. Obtained EMF and XAS are compared with experimental results [1], and discharge reaction mechanisms in Na/FeS₂ battery systems are discussed.
We assume stable crystal phases as model structures of Fe-S, Na-S and Na-Fe-S systems. Calculations are based on the density functional theory within the generalized gradient approximation adopting the all-electron full-potential linearized augmented plane wave method, and XAS spectra are computed on the basis of Fermi&’s golden rule with the one-electron ground states [2]. All the computations are done using the HiLAPW code.
We first calculate EMFs assuming stable Na-S crystals as a final product of discharge reactions of Na/pyrite-FeS₂. Calculated results show that the most likely final product is Na₂S+Fe generating EFM of about 1.2V vs. Na, consistent with the experimental results. We further investigate multi-step reactions considering Fe-S, Na-S and Na_xFeS₂ (x = 1 and 2) models as intermediate products. All assumed multi-step reactions are energetically higher, indicating that the assumed intermediates can be minor products relative to the two-phase form as FeS₂-Na₂S. Among the assumed multi-step reactions, we find energetically acceptable two-step reactions which produce FeS and Na_xFeS₂ intermediate phases, and the two-step reactions can give EFMs close to the two-phase average 1.2V. Thus FeS as well as Na_xFeS₂ may be plausible intermediate products. Comparison of the calculated XAS spectra at the S K-edge with the experimental ones [1] also shows that the intermediates of FeS+Na₂S likely exist during the reactions.
[1] A. Kitajou, J. Yamaguchi, S. Hara and S. Okada, J. Power Sources 247, 391 (2014).
[2] T. Oguchi and H. Momida, J. Phys. Soc. Jpn. 82, 065004 (2013).

Lithium-ion batteries have been widely accepted due to their broad applicability as power sources for portable electronic devices and electric vehicles. However, the use of lithium-ion batteries in large scale application is currently under debate due to the high cost of lithium and its possible supply risk. Thus, minor-metal free or low-cost materials that can be derived from more abundant resources have become increasingly desirable along with the world's growing ecological concerns. Sodium-ion batteries have been explored as a promising alternative to lithium-ion batteries. However, its ionic volume is almost double and its atomic mass is triple than that of lithium. Hence, it has been difficult to find an insertion host that can readily accept repeated insertion and extraction of the large sodium-ion into the matrix. The reported cathode active materials with relatively large capacity for sodium were limited to two-dimensional layered chalcogenides, three-dimensional layered chalcogenides with a corner-sharing matrix, or layered rocksalt oxides. Recently, it has been reported that disodium rhodizonate, Na₂C₆O₆, exhibit good electrochemical properties and cycle performance as a rare organic cathode for sodium-ion batteries [1]. The minor-metal free Na₂C₆O₆ can be considered as a promising cathode candidate for high cost performance sodium-ion batteries. However, its crystal structures during discharge/charge cycle, which correspond to Na_2+xC₆O₆ (0 < x < 2) in composition, still remain unclear.
In this work, we theoretically propose feasible crystal structures of Na_2+xC₆O₆ during discharge/charge processes. Density functional theory calculations have been performed using the full-potential linearized augmented plane wave method [2, 3]. As a result of total energy calculations for Na_2+xC₆O₆ with several space groups, we have found a structural phase transition: The most stable structure for Na₄C₆O₆ has a different C₆O₆ packing arrangement from that in Na₂C₆O₆. The space group for Na₄C₆O₆ also varies in accordance with the C₆O₆ rearrangement. The detailed structural stability of Na_2+xC₆O₆ is discussed by electronic structure analyses. Moreover, electrode potentials vs. Na/Na⁺ of Na_2+xC₆O₆ have been evaluated. The calculated electrode potentials are consistent well with experimental results in which crystal structures are unrevealed. Our predictions from first-principles calculations could be the key to understanding the mechanism of the discharge/charge process for Na₂C₆O₆ cathode and be of benefit to the application of the minor-metal free sodium-ion batteries.
[1] K. Chihara, N. Chujo, A. Kitajou, and S. Okada, Electrochim. Acta, in press.
[2] E. Wimmer, H. Krakauer, M. Weinert, and A. J. Freeman, Phys. Rev. B 24, 864 (1981).
[3] J. M. Soler and A. R. Williams, Phys. Rev. B 440, 1560 (1989).

The development of a practical solar thermal fuel from a subset of photoswitching molecules that can be used as a triggerable heat source (e.g. azobenzenes and norbornadienes) has been hindered by combinations of poor stability, energy densities and high costs. Recent theoretical studies by our group have predicted a new class of materials capable of overcoming these technological challenges. Templating photoswitching molecules onto various substrates that are both rigid and can achieve dense packing of the chromophores (<5 nm) allows for the engineering of specific interactions that are otherwise difficult to achieve.
This presentation will highlight recent experimental results demonstrating the promise of this approach. We have demonstrated a bulk energy density of 56 Wh/kg with ~14% external quantum efficiency in a highly cyclable azobenzene-carbon nanotube material. This presentation will highlight these recent experimental results as well as additional synthetic work by our group towards the building of a library of photoswitching materials that follow these general principles. The completion of this compilation of such a broad range of substrates and photoswitching molecules will allow for the tailoring of this technology to a given application (e.g. thin film or solution). Specifically, the attachment of azobenzenes to templates such as carbon nanotubes, graphene-like carbons, polycyclic aromatic hydrocarbons and porphyrins will be demonstrated. Focus will be given to the structural characterization of these heterogeneous materials.

High volumetric capacity on-chip solid-state supercapacitors were fabricated through a specially designed composite electrode with graphene and chemically surface modified MWCNTs. The surface functionalized MWCNTs with SO3H hydrophilic groups effectively increased ion accessibility into the composite electrodes. In addition, the hydrophilically functionalized MWCNTs were freely dispersed in water and can be uniformly mixed with the graphene oxide solution, opening the possibility for preparing high-dense electrodes. The composite electrodes exhibited a high specific capacitance (58 F cm-3, 99.3 mF cm-2, 62 F g-1) and electrochemically stable, even for the thick electrodes.

This work demonstrates the effect of atomic layer deposited (ALD) Al2O3 on the reactivation of dissolved polysulfides in Li-S batteries. A 0.5 nm thick layer of Al2O3 is conformally coated onto highly porous carbon cloth by ALD, and then assembled in a Li-S battery between the sulfur cathode and the anode side (separator and Li anode) to function as a reactivation component. Compared to half cells with no ALD treatment, the ultrathin Al2O3 coating increases the specific discharge capacity by 25% from 907 to 1136 mAh/g at the 1st cycle, and by 114% from 358 to 766 mAh/g at the 40th cycle. Thus the ALD-Al2O3 improves the initial specific capacity and stabilizes the cycle life remarkably. Scanning electron microscopy and energy-dispersive X-ray spectroscopy results indicate that the ALD-Al2O3 coated carbon cloth sorbs (adsorbs/absorbs) more dissolved sulfur species from the electrolyte. Potential mechanisms for the improved sorption properties are proposed. The combination of an ultrathin ALD-oxide coating with highly porous carbons presents a new strategy to improve the performance of Li-S batteries.

Salinity gradient is an enormous source of clean and renewable energy. We present a process for emf generation from an ionic concentration gradient. The ionic gradient is created using a Polymer electrolyte membrane fuel cell type cell with a microporous ion exchange membrane. A salinity gradient of 30: 1 was established using NaCl solution, in the electrode chambers. An emf of 0.087 V can be realized at ambient temperatures and pressures. The cell emf can further be enhanced by using a bi-polar cell, wherein specific ion exchange membrane (cation and anion) can be incorporated. The cell performance can be optimized for Membrane Electrode System (MES) morphology, active cell area (ACA), and catalytic ionization (CI). A 2V, multicell assembly will be presented and the load characteristics will be simulated, optimized and studied. The thermodynamic and electrical efficiency is discussed for various gradients and flow rates. The relation with number of valance electrons/ ion and the emf generated will be discussed for various gradients. The higher the concentration gradient the larger will be the emf generated. There exists a monotonic relation between the number of valence electron / ion /unit time and the emf generated. The graph between ln (gradient) versus Voltage is a straight line passing through the origin.

Non-aqueous lithium-oxygen (Li-O₂) batteries have received considerable attention because of their remarkably higher theoretical specific energy density than other Li-ion batteries.^[1] However, one of the great challenges for practical applications is low stability of liquid-type non-aqueous electrolyte by superoxide radical attack. To improve chemical and physical stability of electrolyte, solid-state Li ion conductive materials using polymer or ceramic have been extensively studied.^[2] In particular, solid polymer electrolyte (SPE)^[3] has been the promising medium for Li batteries, for example poly(ethylene oxide) (PEO) with Li salt complex (PEO-based SPE) which has exhibited wide electrochemical window, appreciable stability and reasonable solvation ability for alkali metal salts. Since Abraham et al^[4] have shown the first demonstration of gel polymer electrolyte for the Li-O₂ batteries, some studies have reported feasibility of SPE for the Li-O₂ batteries.^[5] However, detailed stability tests and cycling performance using the SPE have not as yet been studied. In this work, we present Li-O₂ cell performance using a PEO-based SPE incorporated with carbon nanotubes (CNT) electrode.
The homogeneous, flexible and semi-transparent PEO-based SPE was prepared by a solvent-free procedure using ball-milling and hot-press techniques. The SPE was then merged with the free-standing CNT film by using the same hot-press technique, which resulted in a two-phase membrane having the SPE and the CNT/SPE. In the CNT/SPE phase, the conductive network of CNT film was coated by the thin PEO-based SPE, which maintained the CNT film pores (a pore size of ~100 nm) required for the smooth O₂ gas transport and accommodation of discharge products. Galvanostatic tests performed on the Li-O₂ cells at 55^oC exhibited reasonable discharge capacity and discharge/recharge potential for initial two cycles but showed unstable potential profile during the third cycle. Detailed analytical results revealed decomposition and depletion of SPE caused by acute parasitic reactions.
References
1. P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J.M Tarascon, Nat. Mater., 2012, 11, 19-29
2. F. Li, H. Kitaura, H. Zhou, Energy Environ. Sci., 2013, 6, 2302-2311
3. F. Gray, M. Armand, Handbook of battery materials, 2011, 2, 627-656
4. K.M. Abraham, Z. Jiang, J. Electrochem. Soc. 1996, 143, 1-5
5. J. Hassoun, F. Croce, M. Armand, B. Scrosati, Angew. Chem. Int. Ed. 2011, 50, 2999-3002

Emerging sodium ion chemistries promise tremendous opportunities for next generation battery technologies, but realizing the promise of these emerging system relies on the development of chemically and structurally robust solid state electrolytes. These ceramic materials must be capable of physically separating molten sodium from incompatible catholytes, while providing high sodium ion conductivity for effective battery performance. Here, we investigate the materials chemistry of the ceramic electrolyte NaSICON (Sodium Super Ion Conductor) with the composition Na1+xZr2P3-xSixO12 (0le;xle;2). While NaSICON has shown promising low temperature sodium ion conductivity, it has been historically plagued by the formation of deleterious secondary phases (e.g., ZrO2, silicates, and phosphates) that can affect ion conductivity and ceramic stability. This work investigates the complex evolution of phases during synthesis and describes potential influences of secondary phases on NaSICON conductivity and stability. Finally, this research explores how variations in processing conditions and the introduction of additives, such as excess sodium, can improve NaSICON phase purity. Insights from these studies may illuminate new syntheses of optimized NaSICON electrolytes for developing sodium battery systems.

Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the US Department of Energy&’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

The nonaqueous lithium-oxygen (Li-O₂) battery has received great deal of attention to increase travel range of electric vehicles owing to its high theoretical energy density. However, unlike the expected operation reactions via oxygen reduction and evolution (O₂(g) + 2Li⁺ + 2e^- harr; Li₂O₂(s)), the Li-O₂ batteries have suffered from parasitic reactions, which result in poor cycling performance and large energy loss. The unintended chemical reactions arise from superoxide radical (O₂^-) formed as an intermediate of oxygen gas reduction and lithium peroxide (Li₂O₂) formed as a discharge product, which react with carbon cathode and organic electrolyte in the Li-O₂ cells to form lithium carbonate (Li₂CO₃) and carboxylates. These side products, in particular insulating Li₂CO₃, are irreversibly formed and deposited on the cathode upon cycling, thus causing failure of primary lithium and oxygen electrochemical reaction. To suppress the side reactions, new cathode materials such as porous gold,¹ TiC,² and ITO³ have been employed. However, these efforts do not completely prevent the formation of Li₂CO₃ due to the inevitable decomposition reaction of electrolyte. Consequently, the endeavor to eliminate the Li₂CO₃ is needed to improve the cycling performance of Li-O₂ cells as long as the Li₂CO₃ are somehow formed.
Here, we present the activity of nickel oxide (NiO) catalyst for the decomposition of Li₂CO₃ in the Li-O₂ cell. The porous NiO particles with a diameter of hundreds of nanometers are homogeneously dispersed on multi-walled carbon nanotubes (NiO/MWCNT). Galvanostatic measurements of Li-O₂ cells with the NiO/MWCNT cathode and ether-based electrolyte exhibit considerably enhanced cycling performance compared with the case of MWCNT cathode only. Further analytical results using FT-IR demonstrate substantial elimination of Li₂CO₃ and lithium carboxylates on the NiO/MWCNT after cycling, which is in a good agreement with the observed low overpotential of Li₂CO₃ oxidation. We expect that the employment of NiO with suitable cathode materials can improve the cycling performance of Li-O₂ cell and eventually aid in achieving practical applications of rechargeable Li-O₂ battery.
1. Peng, Z.; Freunberger, S. A.; Chen, Y.; Bruce, P. G. Science2012, 337, 563.
2. Ottakam Thotiyl, M. M.; Freunberger, S. A.; Peng, Z.; Chen, Y.; Liu, Z.; Bruce, P. G. Nature Mater.2013, 12, 1050.
3. Li, F.; Tang, D.-M.; Chen, Y.; Golberg, D.; Kitaura, H.; Zhang, T.; Yamada, A.; Zhou, H. Nano Lett.2013, 13, 4702.

There is a growing need for new energy storage systems that can serve as competitive alternatives to current Li-ion technologies, but which are much safer and less expensive. One approach is to develop multivalent ion batteries that could, in principle, double or triple the energy density in a given electrochemical cell. However, the extra charge carried by the multivalent ion also introduces stronger interactions with its surroundings, which one might expect to hinder charge transport processes. As a result, it is very challenging to find appropriate intercalation compounds that allow for relatively fast and reversible Mg ion transport.
An established working Mg battery system is comprised of Mg organohaloaluminate salts in tetrahydrofuran solution as the electrolyte, and Mg metal and Mo6S8 Chevrel phase as the anode and cathode, respectively [D. Aurbach et al. Nature 407, 724 (2000)]. The open space between the Mo6S8 octahedra provides fast diffusion channels for Mg ions. Currently, we lack a clear understanding of the mechanism for Mg desolvation and intercalation at the interface between the electrolyte and Chevrel phase surfaces. With this information, one could imagine designing improved cathode and electrolyte materials that overcome the current slow diffusion and charge rates while maintaining electrochemical stability.
Here, we present a theoretical investigation of the dynamics and kinetics of the Mg desolvation/intercalation process. The surface properties of Mo6S8 are first studied using density functional theory (DFT). Several low-index Mo6S8 surfaces are created and the resulting surface energies are compared. The chemical stability of the Mo6S8 surface is studied by considering its interaction with a variety of chemical active species, such as H, O and Mg. An electrolyte/Mo6S8 interface is created and the free energy barrier for Mg ion diffusion is calculated using an ab initio molecular dynamics approach.
This work is supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

Recent experiments on Li-O₂ batteries demonstrated substantially smaller voltage polarizations and hence higher energy efficiency compared to standard Li-O₂ cells forming Li₂O₂ can be achieved when activated Li₅FeO₄ is used as a hybrid electrocatalyst/electrode material. The mechanism by which the charge process activates the Li₅FeO₄, however, is not well understood. Here, we present first principles density functional theory (DFT) GGA+U calculations to establish the thermodynamic conditions for the extraction of Li/Li+O from Li₅FeO₄. A step-by-step, history-dependent, removal process has been followed and the stability of the Li and Li+O deficient samples is investigated on the basis of the energies of the extraction reactions. Various stages of Li/Li+O removal are identified, and structural changes, electronic structure evolution, as well as predicted XANES spectra are reported. We also identify an end product that is closely related to one of the experimentally-observed LiFeO₂ structures.

The demand for cheaper, longer lasting, higher energy density batteries is growing rapidly as the desire for EVs, PHEVs and other mobile technology dependant on portable power sources continues to increase. Although current battery technology has enabled some steps to be made towards fulfilling that demand, it has, at the same time, been the limiting factor in allowing such technology to become widespread. Many alternatives to standard battery technology are currently being explored in labs around the world. One route being pursued is multivalent systems (e.g. Mg2+ and Al3+) which hold promise of higher energy density and potentially lower cost.
While theoretically promising, multivalent systems pose some unique challenges to researchers; one of these challenges is selection of an appropriate electrolyte. Selection of potential electrolytes can be guided by a better understanding of the ion transport and fundamental thermodynamics of ion - solvent systems. In this work we show the first results of studies on aluminum ions in 2-methoxyethyl ether, a low dielectric constant non-aqueous solvent.

As one of next generation energy storage systems, lithium-sulfur battery is a promising candidate due to its exceptionally high theoretical specific capacity (1675 mAh g-1), high theoretical energy density (2500 Wh kg-1), low cost and environmental friendliness. However, sulfur undergoes structural and morphological changes during the charge and discharge process involving the formation of lithium polysulfides. These polysulfides are very soluble in conventional organic electrolytes and shuttle between anode and cathode, resulting in poor cycle life and low system efficiency. Therefore, a variety of carbon materials have been used to form sulfur/carbon composites with favorable structures and properties to improve the discharge capacity, cyclability, and Coulombic efficiency.
In this work, we used a low-cost and facile chemical reaction deposition strategy to immobilize sulfur on quasi-two-dimensional nitrogen-doped graphene nanosheets (NGNSs) to prepare S-NGNSs nanocomposite cathodes for Li/S cells in ionic liquid-based electrolytes. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM) were respectively carried out for investigating and characterizing the obtained S-NGNSs nanocomposite. Cyclic voltammetry (CV) and galvanostatic charge-discharge experiments were used to evaluate the electrochemical performance of S-NGNSs nanocomposite as working electrode in half cells. More detailed results will be discussed in the meeting.

Sodium ion batteries (SIBs) have been receiving significant amount of attention for grid-scale energy storage systems due to the fact their raw electrode materials are cost effective and abundant when compared to lithium ion batteries. Moreover, SIBs operating in aqueous electrolytes are particularly attractive owing to further enhanced safety and lower materials cost. Although aqueous SIBs are appealing in many perspectives, finding both anode and cathode materials within the limited water potential window (~1.23V: H2/2H+ harr; O2/O2-) has been very challenging. Herein, we report a sodium ion hybrid battery using an unconventional organic/inorganic hybrid approach; an organic compound and a Prussian blue derivative serving as anode and cathode electrode materials, respectively. Both electrode materials exhibit appropriate operating voltages and robust reversibility in both half-cell and full-cell measurements, delivering a full-cell voltage of 1.1 V and 88% capacity retention after 100 cycles even at 3~6 min charging/discharging times in an aqueous electrolyte at pH=7. Furthermore, both electrode materials can be synthesized very easily at low temperatures (<100 oC).

The electrochemical redox reactions of stable organic polymer materials with unpaired electrons is a relatively new and exciting area of battery research. Specifically, stable nitroxyl radical-containing polymers have displayed excellent characteristics as the cathode-active material and have presented themselves as low-cost and environmentally friendly alternative to the current Li-ion battery technologies. However, with the advancement of organic-radical battery technology there is a lack of fundamental understanding of the dynamics of charge transfer processes, electronic and ionic, within organic radical-containing polymers. In order to elucidate the mechanisms further, we have conducted an extensive photoluminescence investigation of the polymers in various oxidation states
Since nitroxyl radicals are known fluorescence quenchers, we probed the charge transport in this system by the incorporation of fluorescent perylene markers into the radical-containing polymer matrix. We have investigated the interplay between collisional and static quenching processes using steady-state and time-resolved photoluminescence quenching studies of perylene by TEMPO (2,2,6,6-tetramethylpiperidinyloxyl), radical-containing species. Quenching studies for these model systems, including both free TEMPO monomers and non cross-linked, solution-phase PTMA-nitroxy polymers, (poly(4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl) have allowed us to calculate optimal synthetic parameters for construction of polymer cathode systems. We have determined how such polymer properties as average chain length, spacing between pendant groups, proclivity for polymer folding, and solvent swelling affect both the mechanism of quenching as well as the efficiency of charge transfer. As a function of polymer length, we observe a change in quenching mechanism, while the density of radical moieties has significant affects on quenching/charge transfer efficiency. The quenching sphere of action and thus the optimal distance between radical moieties and fluorophores for the most efficient charge transfer has also been determined and will be discussed at length.

The development of rechargeable Mg batteries, driven by the desire to surpass the limiting specific energy density of Li ion batteries, is currently limited by the lack of high voltage cathodes and stable, functional electrolytes. Few electrolytes are capable of delivering the magnesium cation to the anode surface in a form that readily undergoes de-solvation and without formation of a cation blocking surface film. To date, successful electrolyte strategies take advantage of the creation of a halide - magnesium ion complex where the cation is delivered through a Grignard reagent or an all-inorganic Lewis base-acid mixture involving aluminum trichloride. Generally not considered as significant is the existence of films on the magnesium surface that regulate the rates of charge transfer and metal accommodation. In this paper, we demonstrate the presence and impact of such surface films. We demonstrate that this organic:inorganic composite film, as determined by several ex situ characterization methods, contributes to the rate at which magnesium is deposited and stripped along with the nucleation overpotential for deposition, despite the film exhibiting appreciable electronic conductivity. Deposition and electrodissolution processes are visualized in situ using electrochemical scanning probe microscopy with results showing that the surface film can drive localized cation transport. The origin of stability of a magnesium deposit within a battery electrolyte will be discussed in light of the conductivity of this protective surface film. The properties of such native films highlight the required attributes of synthetic films that might be necessary in electrolytes that lack labile halide species.
This work is 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. Sandia is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE&’s NNSA under contract DE-AC04-94AL85000.

An alternative electrochemical energy storage device, sodium-air battery (SAB) has been readily introduced owing to its high energy density, low cost and environmentally benignity. Cost-effective gel polymer electrolytes (GPEs) are formed by absorbing some amount of organic liquid electrolyte in a polymer frame, thus forming a plasticized or gelled polymer electrolyte. These electrolytes offer light weight and high safety, a longer cycling life without leakage, and ease of fabrication into desired shape and size. The GPE consists of plastic frame poly(methyl methacrylate) (PMMA) and polycarbonate possess a good ability for absorbing organic solvents, ethylene carbonate (EC) and propylene carbonate (PC), which are immobilized within the frame. Sodium salt, sodium tetrafluoroborate (NaBF4), when added into the GPE decreases the crystallinity of the polymer, thus lowering the energy barrier for ion transfer and providing more charge carriers to facilitate the ionic conductivity of the GPE.
The electrolyte film was prepared by solution casting technique. The plastic PMMA and polycarbonate were mixed as 1:1 (weight ratio) and dissolved in tetrahydrofuran solvent at 50 °C. After the polymer completely dissolved, PC, EC and NaBF4 were added into the solution. The composition of the sample was 40% for polymer host, 60% for liquid electrolytes by weight. NaBF4 was added by weight percentage from 5 wt.% to 30 wt.%. The mixture was stirred for 8 hours till the homogenous solution obtained. Then poured solution into the Petri dish, and heated dried for 12 hrs to form the GPE. The thicknesses of the samples varied from 0.05cm to 0.065cm. The morphology examination of GPEs was carried out by scanning electron microscopy (SEM). The conductivity of the GPE is measured by electrochemical impedance spectroscopy (EIS). Cyclic Voltammetry (CV) test was applied to obtain the chemical window and stability of samples. Transference numbers were observed by DC polarization method to identify the ionic conductive property of the samples.
From EIS test, the highest ionic conductivity 5.67×10-4 S cm-1 has been observed for the GPE with 25 wt.% NaBF4 which increases 2 orders of magnitude of the GPE without sodium salt that has the ionic conductivity 1.1×10-6 S/cm. The temperature dependence of ionic conductivity agrees with an Arrhenius equation from 20 oC to 90 oC. The activation energies for GPEs with different concentrations of NaBF4: 5 wt.%, 15 wt.% and 25 wt% are found to be 0.13 eV, 0.17 eV and 0.28 eV respectively which indicate the lower energy barrier for better ion immigration. The CV confirms that the GPEs are electrochemically stable in a range of -5 V to 5V. In addition, the transference number measurements, whose values varied from 0.83 to 0.93, apparently demonstrate that GPEs are high ionic conductive electrolytes. This study is found to be in term of a good sodium ion conductive electrolyte that is promising to be applied to SAB.

Bi-functional nanofiber catalysts are fabricated by electrospinning. Catalyst nanofibers composed of Co oxide and Mn oxide nanoparticles, which are active for oxygen evolution (OER) and oxygen reduction reactions (ORR), respectively, can be manufactured in the close proximity after calcination at 300°C. Nanofibers consisting of two phases are confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive X-ray spectroscopy (EDS) is used to measure the relative composition of Co, Mn and O. Round-trip efficiency with bi-functional catalysts can be larger than 70%, which is larger than that of only Co or Mn oxide nanofibers. Cyclic voltammetry (CV) demonstrates both less positive and less negative onset potentials for OER and ORR, respectively, compared to that of pure carbon black electrode. Specific capacity larger than 1500 mAh/g can be shown when the bi-functional nanofiber catalysts are applied in the Li-air battery cathode.

Two-dimensional (2D) materials can have an excellent capability to handle high rates in ion batteries due to the absence of diffusion barrier. Herein, adsorption of Li, as well as Na, K, and Ca on Ti₃C₂, one representative MXene, is predicted by first-principles density functional calculations. In our study, we observe that these alkali ions exhibit different adsorption energy upon the coverage. The adsorption energies of Na, K and Ca decrease as coverage increases, while Li shows little sensitivity to variance in coverage. This observed relationship between adsorption energies and coverages of alkali ions on Ti₃C₂ can be explained by their effective ionic radii. A larger effective ionic radius increases interaction between alkali atoms, thus lower capacity and coverage are obtained. Our calculated capacity values for Li, Na, K and Ca on Ti₃C₂ are 639.5, 319.8, 191.8 and 159.9 mAh g^minus;1, respectively. Compared to materials currently used in Li ion battery anodes, MXene shows great promise in increasing overall battery performance.

Sulfur has a high specific capacity of 1673 mAh/g as lithium battery cathodes, but the problem of rapid capacity fading presents a significant challenge for practical applications. Two major approaches that have been developed to improve the sulfur cathode performance include fabricating nanostructured conductive matrix to encapsulate sulfur and engineering chemical modification to trap polysulfide dissolution. Here we report a 3-D electrode structure that encompasses both characteristics of sulfur encapsulation and polysulfide trapping. The structure is based on an inverse opal TiO2 structure that is highly conductive and robust towards electrochemical cycling. In addition, chemical tuning of the TiO2 composition through hydrogen reduction was shown to enhance the specific capacity of the sulfur cathode. With the TiO2 encapsulated sulfur structure, we demonstrated that the sulfur cathode could achieve a very high specific capacity of around 890 mAh/g after 200 cycles of charge/discharge. The Coulombic efficiency is also maintained at around 99.5% over cycling. The results showed that encapsulation of sulfur in the inverse opal TiO2 structure could be an effective strategy in improving lithium sulfur batteries performance.

The seemingly ubiquitous Li-ion batteries exhibit superb performance as compared to other types of rechargeable batteries. However, among light metals, Li is a very rare element, which requires active search for suitable alternatives. Among these, Na- and Ca-ion batteries have drawn significant attention in recent years. However, many of the anode materials being pursued have limitations including volume expansion, lack of passivating films and slow kinetics. Here, we investigate graphene with divacancy and Stone-Wales defects as a possible high-capacity anode material for Li-, Na- and Ca-ion batteries. Our results show that while adsorption of adatoms is not possible on pristine graphene, enhanced adsorption is observed on defective graphene due to increased charge transfer between the adatoms and defects. We find that the capacity of batteries increases with the density of defects. For maximum possible divacancy defect densities, the capacities of 1600 mAh/g, 1450 mAh/ and 2900 mAh/g for Li-ion, Na-ion and Ca-ion batteries respectively can be achieved. While for Stone-Wales defects, we find maximum capacities of 1000 mAh/g, 1071 mAh/g and 2142 mAh/g respectively. Our results provide guidelines to create better high-capacity anode material for Li-, Na- and Ca-ion batteries.

We will show how the control of the porous structure impacts the capacitance of nanostructured carbons. Electrochemical results will be presented as well as the as modeling results from molecular dynamics. The Quartz Microbalance technique (EQCM) has also been used to characterize ion adsorption in dynamics with carbons in two different electrolytes: neat EMI,TFSI and solvated EMI,TFSI in acetonitrile. Results show that cations and anions behave differently, and that the presence of solvent affects the ion transfer and adsorption in confined pores.
We recently proposed an approach that consists of designing the carbon electrode structure in conjunction with an electrolyte formulation. We will show that a right combination of nanostructured carbons and an eutectic mixture of ionic liquids can dramatically extend the temperature range of electrical energy storage, thus defying the conventional wisdom that ionic liquids can only be used as electrolytes above room temperature. The combination of various electrolytes / carbons will be presented and the wide temperature range and high cell voltage that these cells can reach will be emphasized. Finally, an application of these materials in micro-supercapacitors will be shown.

The purpose of this work is to develop bulk ceramic electrolyte technology to enable new Li battery technologies. The ceramic electrolyte is based on the garnet structure, with the nominal formula Li7La3Zr2O12, exhibiting the unique combination of: i) electrochemical stability between 0-6 V vs Li/Li+, ii) 1mS/cm conductivity at 298K, and iii) stability in air. While this electrolyte shows promise, there have been few studies that investigate DC Li transport and interfacial phenomena when coupled with metallic Li anodes. The data will include complex impedance analysis to characterize interfacial resistance, cyclic voltammetry, DC polarization and temperature dependent transport measurements. Pre and post cycling X-Ray diffraction and electron microscopy data will also be presented.
This work builds upon recent work to optimize the garnet formulation(s) for maximum conductivity including various doping approaches. Efforts to prepare low porosity robust membranes will also be discussed in the context of correlating microstructural parameters with electrochemical and mechanical stability. This presentation will discuss fundamental and applied aspects to provide a preliminary assessment for the feasibility of garnet electrolyte membranes for use in advanced Li battery technology.

A fast growing interest in the lithium-sulfur cell has been observed during recent years. This cell type, comprising a sulfur/carbon composite as cathode, a liquid electrolyte and Li metal as anode is an attractive candidate for next generation secondary batteries with high gravimetric capacity based on abundant components. It may surpass the energy density of secondary lithium ion batteries but still suffers from serious drawbacks: Cycling life and efficiency as well as the capacity retention of the cells are insufficient, predominantly because of the detrimental and parasitic shuttling of the soluble polysulfides. Current efforts to counteract this shuttle effect include adding LiNO3 to the liquid electrolyte to build up a rigid anode SEI or developing nano-structured cathode architectures in order to delay the diffusion of polysulfides through the electrolyte. The results are promising, but to achieve cycle lifetimes meeting the market requirements, the introduction of a solid electrolyte appears to be inevitable.
The implementation of a hybrid cell concept, i.e. inhibiting the shuttle process by adding a lithium-ion selective membrane to separate the anolyte from the catholyte is in the focus of our work. Different bulk lithium ion conducting phosphate glass-ceramics were prepared as thin pellets and laterally sealed in a special cell setup comprising a stack of anode, separator, solid electrolyte, separator and cathode. Further, lithium-ion conducting thin films were deposited on porous alumina membranes of around 60 mu;m in thickness via pulsed laser deposition to replace the bulk solid electrolytes. These substrates favor the application of the thin films as they stabilize it as a backbone and offer a porous structure that ensures the ionic contact of the thin films with the liquid electrolyte. The ability to cycle hybrid Li/S-cells without a shuttle effect and without the use of a nitrate additive points out the functionality of the Li-ion selective barrier. The impermeability was further proven by a setup using UV-Vis spectrometry. Our cycling experiments state as well, that the different phosphate glasses show significantly different overvoltages. As these do not correlate with the conductivities of the materials and concern both the bulk materials and the thin films, the results clearly indicate that the interface between the solid electrolyte and the liquid electrolyte is the major factor governing the increase in cell resistance. This conclusion was further supported by impedance spectroscopy experiments comprising a special four point setup to identify the interfacial resistance between solid electrolyte and liquid electrolyte.
In conclusion, our study demonstrates that the shuttle process in Li/S cells can be effectively prevented by introducing solid electrolytes in a hybrid cell concept. However further reduction in interfacial resistance is necessary to achieve better rate capability.

Electrochemical double-layer capacitors (EDLCs) provide higher power density and longer cycle life than state-of-the-art-batteries, but their low energy density currently limits their widespread use. Ionic liquids have been proposed as next-generation electrolytes for EDLCs as their high electrochemical stability can increase the energy density of EDLCs by increasing the maximum operating voltage of the devices. We have shown that functionalized graphene sheets (FGSs), a type of defective carbon produced via the thermal exfoliation of graphite oxide, are an ideal material for EDLCs as their intrinsic capacitance can surpass that of pristine graphene by four-fold. Here, we investigate the intrinsic capacitance of the FGS/ionic liquid interface. We compare the intrinsic capacitance of FGSs, HOPG, and glassy carbon in two high voltage (> 4 V) room temperature ionic liquids and contrast these results with those obtained using a traditional organic electrolyte. We also show that the intrinsic capacitance of the FGS/ionic liquid interface can be increased by diluting the ionic liquids with an organic solvent. Though dilution of ionic liquid has been shown to increase the capacitance of full devices, the improvement has been attributed solely to the increase in bulk electrolyte conductivity. We provide evidence demonstrating that the addition of solvent has an intrinsic effect on the capacitance of the interface. These experimental findings provide insight into electrolyte optimization for high energy density EDLCs.

For the development of the next generation of energy storage devices, novel materials are crucially needed to increase storage capacity (e.g., longer range for electric vehicles) while prolonging lifetime. Silicon, germanium and sulfur are promising anodes and cathodes in batteries, because they have high specific charge capacities compared to current electrodes. However, these materials have issues limiting performance. We have used in-situ transmission X-ray microscopy (TXM), X-ray absorption spectroscopy (XAS), and X-ray diffraction (XRD) to investigate structural and morphological changes in Ge anodes and sulfur cathodes during operation. Our results illustrate the powerful approach to characterization enabled by the use of combined, complementary in-situ techniques.
We show in situ 2D and 3D TXM results on Ge anodes, which directly track crack formation and volume changes in micron-sized Ge particles during operation. This allows observation of particle size dependencies and heterogeneities within individual particles during charge/discharge. XRD and XAS on similar Ge anodes track both crystalline (XRD) and amorphous (XAS) phase transitions in Ge during charging and discharging. From these data, a sequence of phase transformations during Ge lithiation is developed. For Li-S batteries comprised of micron-sized sulfur/carbon particles, XRD shows the no formation crystalline Li2S (reported in ex situ XRD studies) and TXM tracks morphological changes, showing that the particles did not dissolve significantly during the discharge, suggesting that the soluble polysulfides are (at least partly) trapped in the carbon matrix.

The conventional aprotic lithium-air batteries suffer from several challenges such poor cycle life, low efficiency, and safety concerns due to the clogging of the air electrode by the insoluble reaction products, decomposition of the organic electrolytes by the electroctalysts, contamination of the nonaqueous electrolyte by the impurities in ambient air, large polarization losses during charge and discharge reactions, and lithium dendrite formation. These problems could be largely overcome with hybrid lithium-air batteries in which the lithium metal anode in a nonaqueous electrolyte is separated by a lithium-ion conducting solid electrolyte membrane from the aqueous air cathode; the solid electrolyte can block the dendrite growth. The major issues with the hybrid lithium-air cells are lack of (i) a robust solid electrolyte with high lithium-ion conductivity and stability in contact with the nonaqueous and aqueous electrolytes on either side and (ii) efficient bifunctional electrocatalysts that offer high catalytic activity for the oxygen reduction reaction (ORR) and oxygen the evolution reaction (OER).
We present here a low-temperature form of lithium cobalt oxide (designated as LT-lithium cobalt oxide) that adopts a lithiated spinel structure in which the lithium ions occupy the 16c octahedral sites of the spinel framework, as an inexpensive, efficient electrocatalyst for OER. The OER activity of LT-lithium cobalt oxide is much higher than that of the high-temperature form of lithium cobalt oxide (designated as HT- lithium cobalt oxide) that is used as a cathode in lithium-ion batteries and even slightly higher than that of the well-studied metallic IrO2. Although LT-lithium cobalt oxide exhibits poor ORR activity, the delithiated LT-lithium cobalt oxide samples exhibit a combination of high ORR and OER activities, making the spinel-type LT-lithium cobalt oxides an excellent bifunctional electrocatalyst for hybrid lithium-air batteries as well as for other metal-air batteries. The high OER and ORR activities of LT-lithium cobalt oxides are attributed to cubane-like subunits in LT-lithium cobalt oxide and a pinning of the cobalt-3d energy with the top of the oxygen-2p band. In addition, nanocomposite air electrodes, consisting of a carbon nanoweb containing pyridone nitrogen and epoxide groups and an inexpensive oxide, that exhibit a combination of high ORR and OER activities will be presented.

Magnesium (Mg) is an attractive candidate for the anode material of a novel high-performance rechargeable battery because of its high energy density, moderate electrochemical activity, chemical stability, as well as the natural abundance. One of the most important issues to realize the Mg rechargeable battery is the development of electrolytes. Aurbach et al. have developed an electrolyte solution, a magnesium organohaloaluminate in tetrahydrofran (THF) with a formula of 0.25 mol/L Mg(AlCl2EtBu)2/THF that shows nearly 100% columbic efficiency, 2.5V electrochemical window, and room-temperature conductivity in the range of several millisiemens, which are much better than those of conventional Grignard reagents.
After the breakthrough by Aurbach, various approaches have been tried for further improvements. Kim et al. enhanced the electrochemical performance of hexamethyldisilazide magnesium chloride (HMDSMgCl) in THF through the addition of Lewis acid AlCl3 together with the crystallization of electrochemical active species [Mg2(mu;-Cl)3*6THF] +. In addition to the wide electrochemical window 3.2V, its non-nucleophilic character successfully realized the demonstration of magnesium sulfur battery. Recently, Abe et al. have found that magnesium deposition and dissolution can take place in some simple electrolyte solutions, such as magnesium bromide together with magnesium ethoxide in 2-methyltetrahydrofuran( (Mg(OEt)2 + MgBr2)/2-MeTHF), and MgBr2 in n-butyl methyl ether (MgBr2/n-BME). It is interesting that these two electrolytes do not include any Lewis acids in the solutions. Moreover, the same group has successfully found that Glymes and magnesium chloride (MgCl2) with aluminum chloride (AlCl3) enabled the magnesium deposition and dissolution on platinum electrode with high coulombic efficiency. It should be noted that these three electrolytes do not include any organic magnesium compounds that would make the solutions highly reactive.
Despite the improvements in the electrochemical properties, at least two more breakthroughs are required for the commercialization regarding electrolytes; one is the reduction of high reactivity, and the other one is suppression of solvent evaporation. Here we report the development of a novel Mg electrolyte using sulfone as solvents. Although it does not include any reactive materials such as organic magnesium compounds as well as Lewis acids, the electrolyte shows reversible Mg deposition and dissolution at room temperature. The electrochemical window is about 3.7V vs Mg without any corrosion on stainless steel electrodes. As the boiling point of the sulfone is high, we don&’t need to care about the solvent evaporation at the operating condition. In addition to the details of our Mg electrolyte, the performance of Mg rechargeable battery whose energy density would be much higher than the present Li-ion battery will be revealed at the conference.

Non-aqueous solution- and suspension-based electrochemical energy storage systems have the potential to revolutionize grid storage by increasing energy density ten-fold over existing aqueous flow batteries and reducing the total system costs five-fold. One of the challenges we face by switching to non-aqueous electrolytes is that the polymer membranes (or separators) currently used for aqueous systems (e.g., Nafion or Celgard) are no longer suitable due to their reliance on water for low impedance ion transport and their intrinsic porosity, which results in unacceptable species crossover of both solvent and storage material. Here, we will describe a new class of mesoarchitectured composite membranes where ions are ushered across polymer-inorganic interfaces. Molecular level control over polymer/inorganic interfaces throughout the conductive mesophase is critical to the realization of efficient transduction pathways for ions.

Atomic-layer-deposition (ALD) coatings have been increasingly used to improve battery performance. However, the electrochemical and mechanistic roles remain largely unclear, especially for ALD coatings on electrodes that undergo significant volume changes (up to 100%) during charging/discharging. Here we investigate an anode consisting of tin nanoparticles (SnNPs) with an ALD-Al2O3 coating. In situ transmission electron microscopy (TEM), for the first time, unveiled the dynamic mechanical protection of the ALD-Al2O3 coating by coherently deforming with the SnNPs under the huge volume changes during charging/discharging. Battery tests in coin-cells further showed the ALD-Al2O3 coating remarkably boosts the cycling performance of the Sn anodes, comparing with those made of bare SnNPs. Chemomechanical simulations clearly revealed that a bare SnNP debonds and falls off the underlying substrate upon charging, and by contrast, the ALD-Al2O3 coating, like ion-conductive nano-glue, robustly anchors the SnNP anode to the substrate during charging/discharging, a key to improving battery cycle performance.

Catalysts are an essential component in chemical energy storage devices such as electrolyzers and photoelectrochemical cells. There is increasing interest in abundant, inexpensive, and scalable catalysts for renewable energy storage. In this talk, we report our recent work in the development and understanding of several new classes of inorganic catalysts that are efficient for hydrogen evolution and oxygen evolution reactions. The catalysts include amorphous molybdenum sulfides, molybdenum carbide and boride, nickel phosphide, and their derivatives. The catalysts are characterized by electron microscopy, X-ray photoelectron spectroscopy, electrochemical quartz microbalance, and impedance spectroscopy. The activity in electrochemical and photoelectrochemical water splitting is explored.

The implementation of a neutral pH aqueous electrolyte energy storage device will be described. The core devices uses a configuration wherein the anode consists of a composite system of activated carbon and NaTi2(PO4)3, and the cathode is an MnO2 - based alkali intercalation compound (either Na4Mn9O18 or cubic spinel lambda;-MnO).1 Synthetic routes, materials properties, and performance attributes will be disclosed. The implementation of these materials in thick format electrode structures will be described and subsequent device level performance attributes will be shown.
Data will be presented showing that large-scale industrially packaged individual batteries with over 200 Wh in capacity (at 8 V at full state of charge) have be produced, qualified, and inserted into large format systems. Further data will show that packs of these batteries in the multi-kWh range have been effectively produced and implemented. Manifestations include units for support of both smaller off-grid applications with bus voltages in the in the 20 to 100 V range, as well as grid-compatible systems with bus voltages in excess of 800 V. These data show that no cell-level battery management system was used to maintain battery string integrity. The recombinant nature of the battery chemistry provides for a self-regulating overcharge condition that allows for even very high voltage battery strings to have long-term stability.

Electrochemical double-layer capacitors (EDLCs) have high power densities and long cycle lifetimes, but, because of their low-to-moderate energy densities, they are not typically used as stand-alone energy sources. To improve the energy density of EDLCs, we are developing a redox-enhanced EDLC that turns the electrolyte in a conventional EDLC into an integral, active component for charge storage - charge is stored in faradaic reactions with soluble redox-active molecules in the electrolyte in addition to in the double-layer capacitance of a porous carbon electrode. We report the identification and study of redox species to enable enhanced energy densities and the understanding of selfnot;-discharge processes within the redox capacitor. We evaluated the redox properties of various candidate redox couples. Bromine and iodine redox couples, when added to the inert aqueous electrolyte, increased the “apparent” capacitance of the positive electrode and showed low self-discharge rates over the course of 1 h (~74 %). When methyl viologen was added to the inert electrolyte, the apparent capacitance of the negative electrode was increased and a slow discharge rate was also observed.
Based on the studies of single redox electrolytes, a redox supercapacitor with a mixed electrolyte composed of 0.1 M KBr and 0.1 M MVCl2 was fabricated and studied. When charged to a potential > ~1.2 V (roughly the separation between the formal potentials of the couples) faradaic charging process were observed in addition to the capacitive processes that significantly increased the energy storage capability. This redox supercapacitor operated at 1.4 V achieved the specific capacity of 110 mAh/g-electrodes and the energy density of 100 mWh/g-electrodes in a simple Swagelock cell. A control EDLC was fabricated using 99.99 % 0.2 M K2SO4 which yielded 35 mAh/g-electrodes and 21 mWh/g-electrodes. The self-discharge rate of control and redox EDLCs was characterized by measuring the remaining capacity and energy density as a function of time at open circuit. The capacity and energy retention rate of 76 % and 50 % was found for the redox EDLC, which was surprisingly slightly higher than found for the control EDCL. This relatively low rate of self-discharge is possibly due to the electrostatic attraction between the charged redox ions and the polarized carbon electrodes. Optimization of the redox electrolyte should further increase the energy density and decrease the self-discharge rate of the redox EDLC, perhaps making them viable for applications where EDLCs are currently non-competitive.

Natural gas, mostly methane, is an attractive replacement of petroleum fuels for automotive vehicles because of its economic and environmental advantages. The technological obstacle to using methane as a vehicular fuel is its comparatively low volumetric energy density, necessitating densification strategies to yield reasonable driving ranges from a reasonably sized tank. The incumbent strategies, liquified natural gas (LNG) and compressed natural gas (CNG), both require cost-prohibitive refill station infrastructure and bulky onboard fuel tanks. Using nanoporous materials as adsorbents could yield a volumetric energy density of methane competitive with CNG, but using a lower storage pressure, alleviating infrastructure barriers. The exciting tunability of nanoporous materials yields billions of possible candidates. In this work, we use computer simulations and mathematical models to identify the features that yield optimal materials for methane storage to guide the materials synthesis community.

Recently, capacitive suspension-type electrodes (‘flowing electrodes&’) have emerged as a mode for achieving high capacity and scalable systems for a range of infrastructure-level challenges (electrochemical flow capacitor/desalination). The core idea behind suspension electrodes is that active material (carbon) can adsorb ions into an electric double layer and transport and store electrons via percolation networks. Although the suspension-type electrodes exhibit high power density, they are limited in terms of their energy density. In order to compete with existing applications for grid level energy storage or desalination the energy density of the suspension electrode needs to be improved.
Here we report the electrochemical performance and material characteristics of a pseudocapacitive manganese dioxide suspension electrode in a sodium sulfate (Na2SO4) electrolyte. The suspensions were electrochemically characterized using cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy in a static cell configuration. The manganese dioxide powders were synthesized using a hydrothermal treatment and characterized with x-ray diffraction. We studied the fundamental electrochemical and rheological trade-offs of different concentration (5wt%, 10wt%, and 15wt%) of conductive additives (carbon black and onion like carbons) in the suspension electrodes and report the subsequent effects on rate performance, and self-discharge. Finally it was found that an expanded voltage window of (~2 V) can be achieved in a suspension electrode based in a neutral electrolyte when the manganese dioxide suspension electrode is combined in an asymmetric configuration with an activated carbon suspension electrode.

Metal hydride based thermal battery is developed for an air conditioning system which can cool or heat the passenger compartment of an electric vehicle independently of the main power, so that cabin comfort does not deplete the vehicle&’s power supply and its range of operation. It uses endothermic and exothermic reactions of metal hydrides for providing cooling or heating. Magnesium hydride is used in this system due to its high energy density. To improve the thermodynamics, kinetic properties and long-term thermal cycle stability of magnesium hydride, multiple additives are doped by using high energy ball-milling technique. Pressure-composition-temperature analysis is used to characterize the properties of the magnesium based hydrides. Moreover, the performance of metal hydride based thermal battery prototype is reported.

Lithium sulfur batteries have brought significant advancement to the current state-of-art battery technologies because of their high theoretical specific energy, but their wide-scale implementation has been impeded by a series of challenges, especially the dissolution of intermediate polysulfides species into the electrolyte. Conductive polymers in combination with nanostructured sulfur have attracted great interest as promising matrices for the confinement of lithium polysulfides. However, the roles of different conductive polymers on the electrochemical performances of sulfur electrode remain elusive and poorly understood due to the vastly different structural configurations of conductive polymer-sulfur composites employed in previous studies. Here we systematically investigate the influence of different conductive polymers on sulfur cathode based on conductive polymer-coated hollow sulfur nanospheres with high uniformity. Three of the most well-known conductive polymers, polyaniline (PANI), polypyrrole (PPY), and poly(3,4-ethylenedioxythiophene) (PEDOT), were coated, respectively, onto monodisperse hollow sulfur nanopsheres through a facile, versatile, and scalable polymerization process. The sulfur cathodes made from these well-defined sulfur nanoparticles act as ideal platforms to study and compare how coating thickness, chemical bonding as well as the conductivity of the polymers affected the sulfur cathode performances from both experimental observations and theoretical simulations. We found that the capability of these three polymers in improving long-term cycling stability and high-rate performance of sulfur cathode decreased in the order of PEDOT > PPY > PANI. High specific capacities and excellent cycle life were demonstrated for sulfur cathodes made from these conductive polymer-coated hollow sulfur nanospheres.

Recently, more and more attention has been paid to sodium ion batteries due to the wide availability and low cost of sodium. Among the anode materials for sodium ion batteries, Sn has both high storage capacity and low voltage operation. The theoretical capacity of Sn is about 847 mAh/g when assuming the full conversion into Na15Sn4. However, the pure Sn powders suffer big volume change in charge and discharge, so it is a big challenge to improve the cycling stability of Sn. In our previous works, we point out that the polymer binder plays an important role in the cell&’s performance. The conductive binder Poly(9,9-dioctylfluorene-co-fluorenone-comethylbenzoic ester) (PFM) used in this study is a polyfluorene-type polymer with two key function groups—carbonyl and methylbenzoic ester—for tailoring the polymer to be conductive in the Sn cycling potential range and for improving the mechanical binding force, respectively. With this binder, the pure Sn nanoparticles exhibit high cycling stability besides high specific capacity.

Lithium-sulfur cell has been considered to be a highly promising candidate to replace the existing lithium-ion batteries because of its higher theoretical capacity (1672 mAh g^minus;1)[1].
Although significant progress has been made during recent years[2], some existing issues are still not resolved. The major one is the dissolution and shuttle effect of lithium polysulfides in the electrolyte solution and their reactions with the lithium negative electrodes. The second one is the insulating nature of sulfur and Li2S, leading to low electrochemical utilization and limited rate capabilitybecause of their poor contact with current collectors. Hence, upon cycling Li-S cells, the sulfur becomes progressively electrochemically inactive. Another failure mechanism of sulfur cathodes relates to large volume change which leads to the deterioration of microstructure or architecture of the electrodes and the pulverization of sulfur electrodes.
In this work, sulfur particles were in-situ grown in the inter-sheets of solvated oriented-graphene films. We have shown that the reduced graphene oxide (RGO) could self-assemble to form an oriented hydrogel film through a simple directional-flow-induced bottom-up assembly process[3]. As a result of micro-corrugation and repulsive inter-sheet solvation/electrostatic forces, RGO sheets in the hydrogel film remained largely separated[4]. The average pores in these graphene films in the form of separated inter-sheets were below 10 nm, providing room for immobilized sulfur and reservoir to constrain liquid polysulfides inside the films. Separated graphene with large surface area can increase the number of active sites for electrode reactions by enlarging the contact area and bonding between the carbon and the sulfur. Free of polymeric binders or conductive additives can lead to increased ratio of active mass. Finally, solvated graphene films also afforded a mechanically strong and flexible supports for sulfur, which could buffer the stress as a result of volume changes of electrode.
Encapsulated sulfur in such graphene films with 60 wt% S (against the whole mass of electrode) could obtain a stable discharge capacity above 1000 mA h g^minus;1 at 0.05 C and 800 mA h g^minus;1 at 0.2 C. SEM measurements showed that the porous structures remained nearly unchanged even after 100 cycles&’ discharging/charging.
References:
[1] M.-K. Song, E. J. Cairns, Y. Zhang, Nanoscale 2013, 5, 2186-2224.
[2] L. Ji, M. Rao, H. Zheng, L. Zhang, Y. Li, W. Duan, J. Guo, E. J. Cairns, and Y. Zhang, J. Am. Chem. Soc. 2011, 133, 18522-18525.
[3] X. W. Yang, J. W. Zhu, L. Qiu, D. Li, Adv. Mater. 2011, 23, 2833-2838.
[4] X. W. Yang, C. Cheng, Y. Wang, L. Qiu, D. Li, Science 2013, 341, 534-537.

DNA-based hybrid films incorporating sol-gel-derived ceramics have shown strong promise as insulating dielectrics for high voltage capacitor applications. Our studies of DNA-CTMA complex/sol-gel hybrid thin film devices have demonstrated reproducibility and stability in temperature-and frequency-dependent dielectric properties as well as reliability in DC voltage breakdown measurements, attaining values consistently in the 300 - 350 V/µm range. We have also investigated layered hybrid films to enhance the performance of the DNA-based dielectric. Functionally layered devices have been designed, fabricated and characterized to determine any added benefit in dielectric measurements. Dielectric breakdown and energy storage will be reported as a function of operating temperature, providing direction for best use case. The electrical/dielectric characteristics of DNA-CTMA with sol-gel-derived ceramics and in layered devices will be examined to determine their effect on vital dielectric parameters for high energy density capacitor applications.