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
crabtree@anl.gov
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
crabtree@uic.edu
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
bpetrovic@anl.gov

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: hli@iphy.ac.cn
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:
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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.