bluuebunny/crossref_metadata_2025 huggingface dataset:
Inverse Opal Carbons As Li-O2 Cathodes with an Ionic Liquid-Based Electrolyte: Effect of Macropore Size on Capacity, Rate Capability and Reversibility
Authors: Olivares-Marín Mara , Palomino Pablo , Enciso Eduardo , Tonti Dino
Published: February 2020

Inverse opals are beautiful macroporous materials prepared by template synthesis and presenting a well-defined arrangement of pores of tunable monodisperse size. Thus, they are ideal model systems for studying the effect of macropore size in lithium-oxygen electrodes.

In this work, inverse opal carbons were prepared by using poly(styrene-co-methacrylic acid) (PS-MAA) spheres of different size as templates via a resorcinol-formaldehyde sol-gel process. These were used in cathodes for Li-O2 batteries using different cell configurations and an ionic liquid electrolyte (LiTFSI in PYR14TFSI). The high porosity and open channels with low tortuosity allowed remarkable capacities of over 3000 mAh/g at 0.1 mA/cm2.

We could relate the carbon textural properties to the capacity, rate capability and reversibility. We observed better rate capability for discharge with the largest macropores (500 nm diameter), evidencing a mass transport limitation. However, charge profiles denoted a remarkable asymmetry respect to discharge, with low coulomb efficiency. Instead, when macropores were smaller than 100 nm we obtained a remarkable symmetry in time-limited discharge-charge profiles. This proves that confinement of discharge products in small pores effectively prevents the electrode passivation.

Acknowledgement

The research leading to these results has received funding from the European Union’s Seventh Framework Programme under EC-GA No. 265971 ‘LABOHR’, and from the Spanish Government under contract MAT2012-39199-C02-01. M.O. acknowledges CSIC for a JAE-DOC research contract.
Stability Enhancement of Nasicon Solid Electrolytes As Protective Layer for Li-Air Systems
Authors: Ni Chung-Ta , Tsai Shu-Yi , Fung Kuan-Zong
Published: February 2020

The development of Li-air battery has received great attention recently. However, using metallic lithium directly as as an anode has been challenging due to the high reactivity of Li. Protective coatings with ionic conduction on metallic Li has be proposed to solve this problem.Inorganic Li ion conductors may be suitable for using as the protection layer.

NASCION-type LiTi2(PO4)3 and perovsikte-La0.50Li0.50TiO3 are known to be inorganic solid electrolytes with adequate conductivity in a range of 10-3 S/cm after required modification. However, Li tends to react with La0.56Li0.33TiO3
due to the incorporation of the released electrons with Ti+4 ions. Simultaneously, Li+ ions will migrate into the vacant sites in the cation sublattice. As a result, La0.50Li0.50TiO3 perovsikte becomes a mixed ionic/electronic conductor after reacting with Li. On the other hand, limited reaction was observed on the Li1+xAlxTi2-x(PO4)3
electrolyte when the metallic Li was used as the anode.

In order to improve the stability of Li1+xAlxTi2-x (PO4)3, a concept of composite electrolyte based on NASCION-type LiTi2(PO4)3 and perovsikte-La0.50Li0.50TiO3 is proposed. With proper mixing and distribution of these two electrolytes, a better stabiltiy from the composite electrolyte is expected.

Thus, the objective of this work is (1) to develop a composite electrolyte based on the mixture of Li1+xAlxTi2-x (PO4)3, and La0.50Li0.50TiO3, (2) to analyze the interface reaction between two components of composite cathode, (3) to investigate the electrical conduction/stability of composite as a function of volume fraction, grain size, and thickness, (4) to evaluate the feasibility of using composite electrolyte for Li-Air battery. The stability of composite electrolyte will be determined based on the measurement of the induced electronic conductivity and the open circuit voltage after a Li-air cell is assembled.
Adsorption of Polysulfides from Electrolyte Using Porous Carbons
Authors: Hippauf Felix , Nickel Winfried , Oschatz Martin , Borchardt Lars , Doerfler Susanne , Kaskel Stefan
Published: February 2020

Due to their high theoretical specific energy density and the low costs of sulfur, Lithium-sulfur (Li-S) batteries are of high interest as the storage of electric energy becomes more and more important. After several year of investigation, they still lack of a high cycling stability, which can be mainly ascribed to the formation of dendrites and particularly, to the so-called polysulfide (PS) shuttle mechanism. Therefore, the understanding of the latter and its possible inhibition is the aim of current research. Adding traces of LiNO3 to the electrolyte or using composite cathodes with additional polysulfide reservoirs seems to prolong the battery life.1,2 Other publications report on carbon host materials with specially designed porosity in order to avoid the polysulfide diffusion. Up to now, the detailed mechanism of the shuttle and the effect of PS reservoirs is not fully understood as previous studies concentrated more on electrochemical characterization of half-cells including other components, such as separator and anode.3

This study is focused on the liquid phase adsorption of stoichiometric and ex-situ synthesized polysulfides from a Li-S battery electrolyte on porous carbons to simulate a simplified Li-S cell environment. Several micro and meso and hierarchically structured porous carbons were investigated - both industrial reference materials and specially designed carbons. The latter are already electrochemically tested as carbon-sulfur cathode composite in Li-S cells. Li2Sx(x=4,6,8) were synthesized by stirring stoichiometric amounts of Lithium and sulfur in DOL/DME (1:1) at 70°C under Argon until the solution reached equilibrium condition. Subsequently, the porous carbons were added and the PS adsorption was monitored by UV/Vis spectroscopy. The influence of different carbon porosities on the adsorption properties of the polysulfides species was investigated.

(1) Ji, X.; Evers, S.; Black, R.; Nazar, L. F. Nat. Commun.
2011, 2, 325.

(2) Aurbach, D.; Pollak, E.; Elazari, R.; Salitra, G.; Kelley, C. S.; Affinito, J. J. Electrochem. Soc.
2009, 156, A694.

(3) Evers, S.; Yim, T.; Nazar, L. F. J. Phys.
Chem. C
2012, 116, 19653–19658.
Charge Transfer and Transport Properties of Lithium Polysfulfide Solutions
Authors: Woodford William , Fan Frank , Baram Nir , Helal Ahmed , Carter W. Craig , Chiang Yet-Ming , McKinley Gareth
Published: February 2020

Metal-sulfur couples are of interest due to the high energy density and potentially low cost of these chemistries. However, the existence of soluble polysulfide intermediates—which exist in all known polar electrolyte systems—has challenged the cycle life and efficiency of these systems. Recently, interest in catholyte cells based on dissolved polysulfide solutions has renewed, in part due to the possible use of these catholytes as flow electrodes with low cost.1-3To realize the potential advantages of dissolved polysulfide catholytes, highly concentrated solutions are needed to obtain high charge storage capacities, which simultaneously retaining adequate rate capability. To achieve this, the rate limiting mechanisms in polysulfide solutions must be understood as a function of concentration and solution composition.

Here, we present experimental measurements of the exchange current density and ionic conductivity and of lithium polysulfide solutions of varying concentration in non-aqueous solvents. Exchange current densities are measured by three different methods: steady-state voltammetry at a C-fiber microelectrode, electrochemical impedance spectroscopy at a glassy carbon macroelectrode, and galvanostatic polarization measurements at a glassy carbon macroelectrode. Solvents of interest include tetraethylene glycol dimethyl ether (TEGDME), 1,2-dimethoxyethane (DME), 1,3-dioxolane (DOL), and mixtures thereof. Ionic conductivies are measured with and without supporting LiTFSI salt, as shown for several selected solvent systems in Figure 1(A). The measured ionic conductivities are correlated with measured solution viscosities, as shown for the TEDGME system in Figure 1(B). Lithium polysulfide solutions with sulfur concentrations of 1-8 M in these solvents have measured exchange current densities on the order of 0.01 – 1 mA cm-2 and ionic conductivities are on the order of 1 – 10 mS cm-1.

This work represents the first report of systematic measurements of these fundamental charge transfer and transport properties for polysulfide solutions. These results enable rational interpretation of the limiting processes in conventional solid sulfur cells as well as the catholyte systems and provide a quantitative basis for selection of electrolyte solvents.

References

1. Demir-Cakan, R. et al. Li–S batteries: simple approaches for superior performance. Energy & Environmental Science
6,176 (2012).

2. Yang, Y., Zheng, G. & Cui, Y. A membrane-free lithium/polysulfide semi-liquid battery for large-scale energy storage. Energy & Environmental Science
6,1552 (2013).

3. Manthiram, A., Fu, Y. & Su, Y.-S. Challenges and Prospects of Lithium–Sulfur Batteries. Acc. Chem. Res.
46,1125–1134 (2013).

Acknowledgements

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.
Nanoscale Operando and 3D In Situ Imaging of Micron-Sized Ge Anode Particles in Li Batteries
Authors: Weker Johanna Nelson , Liu Nian , Andrews Joy C , Toney Michael , Cui Yi
Published: February 2020

Ge anodes have very high theoretical lithium capacity (1600 mAhg-1) and are promising anodes for Li batteries. Ge is more electronically conductive than Si and has a higher room temperature Li-ion diffusivity. However, because of their high capacity, Ge anodes suffer from large volume changes (up to 400%; similar to Si, at 4200 mAhg-1) during electrochemical cycling. Repeated expansion and contraction of these materials lead to fracturing and eventual pulverization resulting in the loss of electrical contact with the current collector and ultimately battery failure.

In order to better understand these failures we have conducted the first 3D nanoscale in situ study of a Li battery system. We imaged Ge anodes with hard X-rays (11.2 keV, above the Ge K-edge) with transmission X-ray microscopy at 30 nm resolution. 2D images in operando were collected at several regions within the particles, and 3D tomography data was also collected at different time points within the fully operating battery (in situ) to further examine the crack formation and density changes that occur with cycling. We found that volume expansion during lithiation is particle size dependent, but the subsequent volume contraction is not. Moreover, we found that only the largest particles actively participate in the second (de)lithiation cycle. From the in situ tomographic information we quantified the volume change in particles and measured the changes in porosity or density as particles (de)lithiate. Our results demonstrate the significant value of high resolution 3D imaging of batteries under operating conditions.
Extended Tests of Pyrazolides As Lithium Salts for Lithium-Ion Cells
Authors: Grünebaum Mariano , Hiller Martin Manuel , Wiemhöfer Hans-Dieter
Published: February 2020

Lithium ion batteries nowadays dominate the market of high power energy storage devices [1]. One of the crucial points for next generation lithium batteries and dual-ion cells for stationary energy storage is the development of lithium salts with enhanced electrochemical stability and without corrosive impact at Al current collectors. Additionally, novel electrolytes for lithium batteries should have a high conductivity and should guarantee long term stability of anode and cathode interfaces as well as lead to stable SEI films. Here, we introduce first examples of a new generation of lithium salts based on pyrazolide anions [2] (cf. Fig. 1). The cyclic anion contains different perfluorinated side chains RF at the 3- and 5-position. Further tests were done with additional modifications at the anionic structure.

Fig. 1: Structures and half-cell cycling with different discharge rates of the anionic pyrazolides and their modified types, RF representing perfluorinated alkyl chains of different lengths.

Both, an efficient synthetic route as well as a thorough characterization of electrochemical stability and conductivity as well as cell tests were carried out. The salts showed an excellent electrochemical stability in non-aqueous solvents up to +5 V vs. Li/Li+. Moreover, cycling of LiFePO4 half-cells revealed structure-conductivity relationships for the novel salts. Both salt-types allowed at least 200 full cycles. Thus, the novel class lithium salts exhibits promising candidates for novel liquid and polymeric electrolyte systems and future safe lithium ion batteries.

The authors acknowledge funding by the German federal ministry of education and research (BMBF) within the project “Insider”, No. 03EK3031A.

[1] M. Winter, R. J. Brodd, Chemical Reviews, 104, 4245, 2004.

[2] M. Grünebaum, H.-D. Wiemhöfer, M.M. Hiller, WO2013135824 A2, 2012.
In-Situ gelled Polymer Electrolytes for Advanced Lithium Ion Batteries
Authors: Di Lecce Daniele , Vitucci Francesco , Palumbo Oriele , Paolone Annalisa , Panero Stefania , Hassoun Jusef , Navarra Maria Assunta
Published: February 2020

The activities aimed at reducing the safety hazard in lithium batteries have successfully considered the replacement of the conventional, volatile and flammable carbonate-based, liquid electrolytes with more stable polymer electrolytes, obtained in the form of free standing membranes. With respect to other solid polymer electrolytes, such as those based on poly(ethylene oxide), gelled polymer electrolytes (GPEs) have the great advantage of offering high conductivity, i.e. of the order of 10−3 S cm−1, over a wide temperature range, combined with a large electrochemical stability, i.e. extending up to 5V versus Li+/Li [1-3].

Poly(vinylidene fluoride) (PVdF)-based, gel-type membranes have been widely investigated as Li-conducting systems and prepared by conventional solvent-casting procedures [4] or electro-spinning techniques [5].

In this work we report on originally developed, PVdF-based GPEs obtained by in-situ formation of the gel matrix during cell assembly, followed by a lithium salt infiltration step [6]. Particular emphasis was devoted to the study and the optimization of the GPE composition. The substitution of the commonly used LiPF6salt with the fluorine free, bis(oxalato)borate (LiBOB) was investigated.

A detailed thermal and dynamical mechanical characterization was adopted to elucidate the properties of the proposed systems over a wide temperature range. Vibrational spectroscopy revealed interesting molecular interactions among components, mainly. polymer and salt, strongly affecting the stability of the membranes. The electrochemical investigation confirmed high ionic conductivity, a controlled interfacial resistivity versus lithium metal and a good electrochemical stability window.

The feasibility of the in-situ gelled, PVdF-based polymer electrolyte containing the LiBOB salt was demonstrated by successful galvanostatic cyclations of the quoted membrane in different lithium-ion cell configurations, obtained by coupling a Sn-C alloying anode with an high voltage spinel or a LiFePO4cathode.

Acknowledgments

The results of this work have been obtained by the financial support of the European Community within the Seventh Framework Programme APPLES (Advanced, High Performance, Polymer Lithium Batteries for Electrochemical Storage) Project (contract number 265644).

References

[1] F. Croce, G.B. Appetecchi, L. Persi, B. Scrosati, Nature 394 (1998) 456.

[2] G.B. Appetecchi, P. Romagnoli, B. Scrosati, Electrochem. Commun. 3

(2001) 281.

[3] J. Hassoun, S. Panero, P. Reale, B. Scrosati, Adv. Mater. 2 (2009) 4807.

[4] J. Hassoun, P. Reale, Bruno Scrosati, J. Mater. Chem. 17 (2007) 3668.

[5] F. Croce, M.L. Focarete, J. Hassoun, I. Meschinia, B. Scrosati, Energy Environ. Sci.

4 (2011) 921.

[6] L. Lombardo, M. A. Navarra, S. Panero, L. Aguilera Medina, A. Matic, J. Hassoun, J. Power Sources, 245 (2014) 232.
Composition Regulation Prediction of Cathode Materials By First-Principles Calculation
Authors: Li Yang , Lian Fang , Chen Ning , Hao Zhen-jia , Chou Kuo-Chih
Published: February 2020

The performance of lithium-ion batteries (LIBs) critically depends on the intrinsic properties of the electrode materials. The design and application of novel materials, especially cathode materials, will always be primary to attain performances improvements in LIBs. Mainly commercial cathode materials contain layered (e.g. LiCoO2), spinel (e.g. LiMn2O4) and olivine (e.g. LiFePO4) structures. As known, Part of layered compounds gradually transforms into spinel during cycling, or spinel-like structure forms in the as-prepared layered materials, which results in capacity fading, structure instability and safety problems. The doping technique is accepted as an effective approach to improve the structural stability and electrochemical performance.

First-principles calculation method, which is based on Density Functional Theory (DFT), is used to solve the Schrödinger equation after some rational approximations. The obtained wave function of the system contains a lot of natural information of materials. The computational methods could be the most powerful complementarity for experimental ones, which is helpful for understanding macro-properties and materials design. The First principles calculation method has been applied in the field of LIBs including calculating average lithium intercalation voltage, analyzing intercalation and extraction mechanism, optimizing the structure, etc.

In this work, we modeled the real and virtual layered (LiMO2) and spinel (LiM2O4) phases (M=Sc~Cu, Y~Ag, Mg~Sr and Al~In), then we have comparatively studied the phase stability between the layered phase LiMO2 and spinel phase LiM2O4 (M=Sc~Cu, Y~Ag, Mg~Sr and Al~In), as well as the impact regulation of doping. The phase stability of a specific compound depends on both binding and reaction energy. And the dominant phase between layered LiMO2 and spinel LiM2O4 is close related to the valence state of element M. The location of the compounds with multi-cationic M in the phase dominant figure can be determined by ingredient percentage weighted average method. The regulation of phase stability and impact of multi cationic doping have been proved by the experimental results from references. The phase dominant figure based on the First principles calculation is a power tool to predict the property of LiMO2 layered materials with multi-cationic M.
Measurement and Analysis of Adhesion Property of Lithium-Ion Battery Electrodes with SAICAS®
Authors: Son Bongki , Ryou Mhyung-Hyun , Choi Jaecheol , Lee Taejoo , Kim Jong Hun , Lee Yunju , Jeong Jiseon , Yeon Daeyong , Song Seonghyun , Appiah Williams Agyei , Lee Yong Min
Published: February 2020

The adhesion strength of lithium-ion battery (LIB) electrodes consisting of active material, nano-sized electric conductor and polymeric binder is measured by a new analysis tool, called the Surface and Interfacial Cutting Analysis System (SAICAS®). Compared to the conventional peel test with the same electrode, SAICAS® gives higher adhesion strength owing to its elaborate cutting-based measurement system. In addition, the effects on adhesion property of the polymeric binder type and content, electrode density and measuring point are also investigated to determine whether SAICAS® provides reliable results. The findings confirm SAICAS® as an effective and promising tool to measure and analyze the adhesion properties of LIB electrodes.

References

[1] B. Son et al., ACS Applied Materials & Interfaces, 6 (2014) 526-531
Rechargeable Lithium Polymer Batteries Assembled with Electrospun Poly(ethylene oxide) Membranes
Authors: Choi Ji-Ae , Jung Yun-Chae , Park Se-Mi , Kim Dong-Won
Published: February 2020

Solid polymer electrolytes have been paid much attention in rechargeable lithium batteries, due to absence of electrolyte leakage, enhanced safety and design flexibility [1,2]. Solid polymer electrolytes studied to date are mainly based on poly(ethylene oxide)(PEO) containing lithium salts. However, these materials have a major drawback that the ionic conductivity for practical application can only be reached at high temperature, due to the high degree of crystallinity inherent in these complexes at ambient temperature. Because of the inherent drawback, various attempts such as grafting, block copolymerization, interpenetration polymer network have been tried to incorporate PEO into a macromolecular sequence, which inhibits crystallization, while maintaining a low value of the glass transition temperature. In our study, with the aim of developing highly conductive polymer electrolytes with high mechanical strength, we prepared the cross-linked polymer electrolytes using low-molecular weight PEO, which are supported by electrospun nanoporous membrane based on high-molecular weight PEO. In this system, mechanically robust porous membrane with chemical cross-linking can protect against electric short to assure safety reliability and make a flexible thin film. By using these solid polymer electrolytes, the lithium polymer cells are assembled and their cycling performances are evaluated at room temperature.

References

[1] F.M.Gray, Polymer Electrolytes, The Royal Society of Chemistry, Cambridge, 1997.

[2] W.A.Van Schalkwijk, B.Scrosati, Eds., Advances in Lithium-Ion Batteries, Kluwer Academic/Plenum Publishers, New York, 2003.
Ionic Diffusion in the Solid Solution Na3-XKxPO4 (0 ≤ x ≤ 3): Experimental Results and First Principle Calculations
Authors: Guin Marie , Tietz Frank , Bhat Kaustubh , Lustfeld Hans
Published: February 2020

Na3PO4 is a well-known ionic conductor [1,2] and serves in this work as a starting point to investigate the solid solution Na3-xKxPO4with 0 ≤ x ≤ 3. The aim is to elucidate the impact of potassium ions on the physical properties: crystalline phases, band gaps, activation energies and ionic conductivities.

Various compositions in this solid solution are synthesised by annealing the starting materials at 1200°C according to the Na3PO4-K3PO4phase diagram [3]. Then the crystalline phases, band gaps, activation energies and ionic conductivities are determined experimentally and measured.

Using density functional theory [4] the ground state energies and band gaps are calculated for the various phases. Energy barriers are calculated for various paths of the cations Na+ and K+by using the nudged elastic band (NEB) method [5].

The theoretical and experimental results, especially the simulated energy barriers and the equivalent activation energies, are compared and discussed.

We think that our approach can be applied to more complex solid electrolytes with polyanionic structures like NASICON [6,7].

References:

[1] A. Hooper, P. McGeehin, K. T. Harrison, B. C. Tofield, J. Solid State Chem. 24 (1978) 265-275

[2] J. T. S. Irvine, A. R. West, Solid State Ionics 28-30 (1988) 214-219

[3] I. B. Markina, N. K. Voskresenskaya, Russ. J. Inorg. Chem. 14 (1969) 1188-1192

[4] P. E. Blöchl, Phys. Rev. B 50 (1994) 17953-17979

[5] G. Henkelman, B. P. Uberuaga, H. Jónsson, J. Chem. Phys. 113 (2000) 9901-9904

[6] H.Y.P. Hong, Mat. Res. Bull. 11 (1976) 173-182

[7] H.Y.P. Hong, J.B. Goodenough, J.A. Kafalas, Mat. Res. Bull. 11 (1976) 203-220
LixFeF6 (x = 2, 3, 4) Battery Materials: Structural, Electronic and Lithium Diffusion Properties Presentation Format: Poster
Authors: Schroeder Melanie , Eames Christopher , Tompsett David , Lieser Georg , Islam M. Saiful
Published: February 2020

Lithium iron fluoride materials have attracted recent interest as cathode materials for lithium ion batteries. The electrochemical properties of the high energy density LixFeF6 (x = 2, 3, 4) materials have been evaluated using a combination of potentials-based and DFT computational methods. Voltages of 6.1V and 3.0V are found for lithium intercalation from Li2FeF6 to α-Li3FeF6 and α-Li3FeF6 to Li4FeF6 respectively. The calculated density of states indicate that Li2FeF6 possesses metallic states that become strongly insulating after lithium intercalation to form α-Li3FeF6. The large energy gain associated with this metal-insulator transiton is likely to contribute to the associated large voltage of 6.1 V. Molecular dynamics simulations of lithium diffusion in α-Li3FeF6 at typical battery operating temperatures indicate high lithium-ion mobility with low activation barriers. These results suggest the potential for good rate performance for lithium iron fluoride cathode materials[1].

[1] M. Schroeder, C. Eames, D. A. Tompsett, G. Lieser, M. S. Islam, Phys. Chem. Chem. Phys., 2013, 15, 20473.
Atomistic Investigation of Lithiation Behaviors in Silicon Nanowires: Reactive Molecular Dynamics Simulation
Authors: Jung Hyun , Joo Jaeyong , Lee Kwang-Ryeol , Han Sang Soo
Published: February 2020

Recently silicon has attracted intense interest as a promising anode material of lithium-ion batteries due to its extremely high capacity of 4200 mA/g (for Li4.2Si) that is much higher than 372 mAh/g (for LiC6) of graphite. However, it seriously suffers from large volume change (even up to 300%) of the electrode upon lithiation, leading to its pulverization or mechanical failure during lithiation/delithiation processes and the rapid capacity fading. To overcome this problem, Si nanowires have been considered. Use of such Si nanowires provides their facile relaxation during lithiation/delithiation without mechanical breaking. To design better Si electrodes, a study to unveil atomic-scale mechanisms involving the volume expansion and the phase transformation upon lithiation is critical. In order to investigate the lithiation mechanism in Si nanowires, we have developed a reactive force field (ReaxFF) for Si-Li systems based on density functional theory calculations. The ReaxFF method provides a highly transferable simulation method for atomistic scale simulation on chemical reactions at the nanosecond and nanometer scale. Molecular dynamics (MD) simulations with the ReaxFF reproduces well experimental anisotropic volume expansion of Si nanowires during lithiation and diffusion behaviors of lithium atoms, indicating that it would be definitely helpful to investigate lithiation mechanism of Si electrodes and then design new Si electrodes.
Improvement of Electrochemical Performance of Bulk-Type All-Solid-State Lithium Secondary Batteries By Using Sulfide Solid Electrolyte Thin Films
Authors: Ito Yusuke , Sakuda Atsushi , Hayashi Akitoshi , Tatsumisago Masahiro
Published: February 2020

All-solid-state batteries using inorganic solid electrolytes are widely studied as next generation batteries. Two types (bulk or thin-film) of batteries have been investigated. Especially, bulk-type batteries, which use composite electrodes of active material and electrolyte powders, are anticipated for power sources with high energy density. Solid electrolyte thin films are useful for bulk-type batteries with an ideal electrode-electrolyte interface. Furthermore, the solid electrolyte contents in composite electrodes can be reduced significantly. We previously fabricated amorphous Li2S-P2S5 and Li2S-GeS2 thin films with high lithium-ion concentrations by pulsed laser deposition (PLD) [1, 2], and this technique was used for coating solid electrolyte thin films on active material particles. Consequently, the energy density of all-solid-state batteries normalized by the total weight of the composite electrode increased [2, 3]. In order to further improve the battery performance, solid electrolyte thin films with higher lithium-ion conductivity are indispensable. We prepared the 33Li4GeS4·67Li3PS4 (mol%) thin film with an ionic conductivity of 1.1×10-4 S cm-1, and the conductivity was increased to 1.8×10-3 S cm-1 by a heat treatment at 200 oC. The all-solid-state cell using LiCoO2 particles coated with the 33Li4GeS4·67Li3PS4 (SE) thin film was charged and discharged with a larger capacity of 67 mAh g-1 than that using non SE-coated LiCoO2 particles. Moreover, the capacity of all-solid-state cell increased to 80 mAh g-1after enhancing the ionic conductivity of SE-coating layer after the heat treatment. The coating of highly-ion conductive solid electrolyte thin films on active material particles is considered to be effective in forming an ideal interface between electrode and electrolyte, resulting in the increase of energy density in bulk-type all-solid-state batteries.

Acknowledgement: This study is financially supported by Toyota Motor Corporation.

References

[1] A. Sakuda et al., J. Am. Ceram. Soc., 93(2010) 765-768.

[2] Y. Ito et al., Solid State Ionics, 236(2013) 1-4.

[3] A. Sakuda et al., J. Power Sources, 196 (2011) 6735-6741.
Direct Observation of Li-Ions under Equilibrium and Non-Equilibrium Conditions By In Situ Neutron Depth Profiling
Authors: Zhang Xiaoyu , Labohm Freek , Wagemaker Marnix
Published: February 2020

Neutron Depth Profiling allows to measure Li-ion concentration profiles perpendicular to the electrode plane. Incoming thermal neutrons are captured by 6Li (natural abundance 7.6%) producing charged 3H and 4He particles, the energy loss of which can be related to the depth of origin of the reaction, and hence of the lithium ions in the electrode. Using in-situ Neutron Depth Profiling (NDP) Li-concentration profiles were measured under various electrochemical conditions in LiFePO4 electrodes. It is directly observed that at relatively high charge rate conditions (1C) lithium is depleted near the electrolyte side resulting in a lithium gradient over the electrode. During a subsequent rest period this relaxes towards a homogeneous depletion throughout the complete electrode removing the lithium gradient. At lower charge rates (0.1C, 0.2C and 0.5C) no gradient was observed indicating that the charging proceeds nearly in equilibrium. These direct observation illustrate that the charge transport in these electrodes is rate limiting and not the nucleation and diffusion in the LiFePO4. By improving the ionic transport trough the electrodes by templating the concentration gradients were not observed at high charge rate conditions (1C), explaining the better performance of these templated electrodes. In addition aging tests were performed to locate the deactivated lithium in the electrodes. In summary the possibilities of NDP in Li-ion batteries are demonstrated under realistic electrochemical conditions.
Visualization of Li Profile in an All-Solid-State Li-Ion Battery By In Situ Electron Holography and Spatially-Resolved Eels
Authors: Yamamoto Kazuo , Yoshida Ryuji , Shimoyamada Atsushi , Sato Takeshi , Matsumoto Hiroaki , Iriyama Yasutoshi , Hirayama Tsukasa
Published: February 2020

All-solid-state Li-ion batteries (LIBs) have been expected to be next generation energy-storage-devices. However, a large interfacial resistance of Li-ion transfer at the electrode/solid-electrolyte interfaces prevents from the practical use. We have so far developed technique to operate the LIB in a TEM and observed the electric potential change around the interfaces by
in situ electron holography (EH) [1]. However, it is still unclear how the Li-ions are distributed and what kind of relation the Li and the potential profiles have in nanometer scale. In this report, we used spatially-resolved electron energy loss spectroscopy (SR-EELS) to directly detect the Li distribution around the interface, and compared with the potential profile observed by EH.

Figure 1(a) shows a schematic of our battery model sample. The Li2O-Al2O3-TiO2-P2O5-based glass-ceramics sheet (LATP) was used as the solid electrolyte, and the LiCoO2 positive electrode was deposited on one side. The negative electrode was prepared in situ by Li insertion reaction to the negative side LATP [2].

After 50 CV cycles, the negative side region was lifted out by a focused ion beam method and the TEM sample was prepared. The TEM image (Fig. 1(b)) shows a slightly different contrast around the interface. Fig. 1(c) shows the Li spectrum image detected by SR-EELS, the horizontal and vertical axes correspond to the electron energy loss and the sample position of the Fig. 1(b) in the vertical direction, respectively. The Li profile (Fig. 1(d)) was similar to the potential profile (Fig. 1(e)). Therefore, the EH detects the nanometer scale potential change due to the Li insertion reaction. The electronic structure changes of the other important elements (Ti and O) due to the Li insertion will be discussed in this presentation.

This work was supported by the RISING project of the New Energy and Industrial Technology Development Organization (NEDO) in Japan.

[1] K. Yamamoto et al., Angew. Chem. Int. Ed.
49 (2010) 4414 - 4417.

[2] Y. Iriyama et al., Electrochem. Commun. 8 (2006) 1287-1291.
90° Domain Structure of (La,Li)TiO3 and Its Influence on Li Conduction Properties
Authors: Moriwake Hiroki , Gao Xiang , Kimura Teiichi , Fisher Craig Andrew James , Kuwabara Akihide , Ikuhara Yumi H. , Oki Hideki , Tojigamori Takeshi , Kohama Keiichi , Ikuhara Yuichi
Published: February 2020

The influence of 90° domain boundaries in (La,Li)TiO3 (LLTO) on the Li conduction mechanism has been examined by a combination of state-of-the-art experiments and first-principles calculations. The atomistic structure of 90° domain boundaries in LLTO has been determined using HAADF-STEM observations. Using HAADF-STEM observations, we can obtain Z-contrast image. As shown in Fig.1, bright spots correspond to heavier La column. Important finding is that at 90° domain boundary, each cells connected by La layer. Based on this structural information, first-principles calculations were carried out. In this study, we use projector augmented wave (PAW) method based on the density functional theory (DFT). Li conduction path and its activation energy were determined using nudged elastic band (NEB) method. Phonon dispersion relations were determined by frozen phonon method. Firstly we performed bulk crystal calculations using tetragonal (SG: P4/mmm) (La0.5,Li0.5)TiO3 assuming alternative stacking La layer and Li layer along c-direction. The calculated phonon dispersion for bulk crystal shows soft-mode in the entire wave vector space. This indicate lattice instability mainly TiO6-octahedoron rotation. Because of this TiO6-octahedoron rotation instability, calculated Li conduction activation energy for LLTO bulk shows exceptionally small value (E
a = 0.2 eV). However, this theoretical E
a was quite small to compare with experimentally reported value (E
a = 0.4 eV). To reveal the origin of this E
a discrepancy between theory and experiments, secondary, we examined Li-conduction energies at 90° domain boundary. We assumed two type of Li conduction: a) Li conduction through La layer, b)Li conduction through La vacancy at La layer. a) Li conduction through La layer shows very high E
a of 3 eV. This indicate La layer acting blocking layer for Li conduction. However, if we assume the La vacancy at La layer, conduction energy significantly decreased to 0.6 eV. This conduction energy well corresponds to experimental value. Our calculations reveal that Li conduction in LLTO should be strongly influenced by 90° domain boundaries in this system.
Evolution of Chemical and Morphological Changes of High Capacity Electrode Materials Across Multiple Lengths Scales
Authors: Liu Yijin , Yang Feifei , Nanda Jagjit , Andrews Joy C. , Martha Surendra K , Callender Andrew F , Pannala Sreekanth
Published: February 2020

Understanding and quantifying the changes in chemical composition as well as morphology of battery materials under electrochemical cycling is fundamental to their long cycle life and safety1-2. This is particularly true for high energy density lithium-manganese rich cathodes which transitions from a high voltage layered–layered phase to a defect type spinel phase under constant electrochemical cycling. In this study we combine the full-field transmission X-ray microscopy (TXM) and the X-ray absorption near edge structure (XANES) to spatially resolve and map the accompanying chemical phase change and morphology of a high voltage lithium-ion cathode composition, Li1.2Mn0.525Ni0.175Co0.1O2, (LMR-NMC)3
at a resolution down to 30 nm over a fields-of-view of several tens of microns. 2D TXM-XANES imaging was conducted on a series of samples recovered at different stages of the battery cycling, showing that the material experiences phase segregation of various transition metal species from the particle bulk to surface4. Energy-resolved 3D morphology and quantification analysis with elemental information suggested that the distribution of three transition metal is heterogeneous and the surface of material particle constantly evolves with electrochemical cycling with varied average concentration of Mn, Co and Ni compared to particle internal.

These results will be compared with results obtained from confocal ex-situ Raman mapping for pristine and cycled LMR-NMC composite cathodes. Raman results provide important information regarding the chemical homogeneity of the electrodes with respect to active material, binder and carbon additive distribution and their changes under high voltage electrochemical cycling.

Florian Meirer, Jordi Cabana, Yijin Liu, Apurva Mehta, Joy C. Andrews and Piero Pianetta, J. Synchrotron Rad,. 18, 773 (2011).

Wen-Chin Chen, Yen-Fang Song, Chun-Chieh Wang, Yijin Liu, Darius T. Morris,Piero A. Pianetta, Joy C. Andrews, Hung-Chun Wud and Nae-Lih Wu, J. Mater. Chem. A
1, 10847. (2013).

Surendra K. Martha, Jagjit Nanda, Gabriel Veith Nancy J. Dudney, J Power Sources 199, 220 (2012)

Fei fei Yang et al. Under preparation (2014)
Li9Mg3[PO4]4F3
and Li2Mg[PO4]F: Crystal Structures and Ionic Conductivities
Authors: Ben Yahia Hamdi , Shikano Masahiro , Takeuchi Tomonari , Kobayashi Hironori
Published: February 2020

In oxide electrolytes, crystalline phosphate with NASICON (NaSuper Ionic Conductor)-type structures such as Li1+xAlxTi2
−x(PO4)3 (LATP) and Li1+xAlxGe2
−x(PO4)3 (LAGP) are known as excellent Li ion conductors. Perovskite Li0.5
−3xLa0.5+xTiO3 (LLT) exhibits the high level of bulk conductivity of 10−3 S cm−1, but LATP and LLT electrolytes have Ti element in crystalline structure, and thus transition metal such as Ti is easily reduced by lithium metal negative electrode; it is thus difficult for these electrolytes to use in lithium metal batteries.

Recently, we started the systematic study of crystal structure and the electrochemical properties of fluorophosphate phases which do not contain transition metal elements. Indeed, in the ternary phase diagram LiMgPO4-LiF-Li3PO4, two new lithium rich phases have been discovered (Li2Mg[PO4]F and Li9Mg3[PO4]4F3). Li2Mg[PO4]F crystallizes with the well-known Li2Ni[PO4]F-type structure, whereas the Li9Mg3[PO4]4F3 crystallizes with a new-type of structure. Li9Mg3[PO4]4F3 exhibits an ionic conductivity of 10-4 S cm-1 at 300 °C, which is much higher than that of Li3VO4 (σ
300
°C =1.6x10-6 S cm-1), γ-Li3PO4 (σ
300
°C =2.2 ´ 10-8 S cm-1) or Li2SO4 (σ
300
°C =2 ´ 10-7 S cm-1). This new phase would be also of great interest as positive electrode for Li-ion batteries if Mg2+ could be replaced by Fe2+ or Mn2+cations [1].

[1] Crystal structures of the new fluorophosphates Li9Mg3[PO4]4F3 and Li2Mg[PO4]F and ionic conductivities of selected compositions, H. Ben Yahia, M. Shikano, T. Takeuchi, H. Kobayashi, M. Itoh,
J. Mater. Chem. A (2014)DOI:10.1039/C3TA15264B.
Towards Safer Sodium-Ion Batteries Via Ionic Liquids As Electrolyte Additives
Authors: Monti Damien , Ponrouch Alexandre , Johansson Patrik , Palacin M Rosa
Published: February 2020

Our society is in urgent need of more efficient, affordable and environmentally friendly energy storage technologies. While lithium-ion batteries (LIB) is undeniably the main track of development and outstanding at present, complementary technologies are needed for managing applications such as renewable energy integration. One particularly appealing alternative is to explore the feasibility of a technology analogous to LIB – sodium ion batteries (SIB) – using the basic LIB know-how and with sodium being more abundant and less expensive.

As in any battery technology, the electrolyte choice is as important as that of the electrodes to ensure successful operation. Considering both safety and “environmental impact” ionic liquids (ILs) have emerged as an interesting option for LIB. ILs exhibit both non-volatility and non-flammability, but unfortunately their high viscosities and comparatively low conductivities are expected to considerably limit the rate performance. Mixed electrolytes, i.e. with ILs as additives to an organic electrolyte, are a compromise suggested to improve the safety – while still providing an appreciable conductivity. Here, the possibility of expanding this strategy also to the SIB technology has been explored.

We here present a systematic study of several electrolytes consisting of a sodium salt (NaTFSI) dissolved in mixtures of ILs and organic solvents, using electrochemical techniques (cyclic voltammetry, chronopotentiometry) coupled to various safety tests (e.g. self-extinguishing time (SET) and flash point (FP)). Imidazolium (BMImTFSI/EMImTFSI) and pyrrolidinium (PYR13TFSI) ILs were used as additives to optimized ethylene carbonate: propylene carbonate (EC:PC) electrolytes, while Hard Carbon (HC) and Na3V2(PO4)3 (NVP) were used as anode and cathode, respectively. Electrochemical tests were performed on half cells to evaluate the cycling abilities and the electrochemical stability of each electrolyte/electrode combination. HC tested with the BMImTFSI-EC:PC electrolytes exhibit specific capacities of ca 250 mAhg-1 and 140 mAhg-1 at C/5 and 1C rates with capacity retentions of 95% and 98%, respectively. For PYR13TFSI-EC:PC ~150 mAhg-1 at C/10 rate a Coulombic efficiency of ca 98% was achieved. The NVP electrode, exhibits capacities of ~80 mAhg-1 with the BMImTFSI-EC:PC electrolytes at C/10 rate, and of 80, 75 and 46 mAhg-1 at C/10, C/5 and C, respectively with the PYR13TFSI-EC:PC electrolyte. A successful full SIB cell was assembled based on the best choices of the above materials as a proof of concept. As a major argument for the use of ILs is an increased safety, it was encouraging that the safety tests, carried out in air for many different compositions, unambiguously proved the addition of ILs to decrease the SET, as well as the flame intensity, and simultaneously raise the FP.
In silico Based Rank-Order Determination and Experiments on Non-Aqueous Electrolytes for Li-Ion Batteries and Beyond
Authors: Sankaranarayanan Subramanian K. R. S. , Narayanan Badri , Kamath Ganesh , Xiong Hui (Claire)
Published: February 2020

Electrolytes are an important component of electrochemical energy storage systems and their optimization is critical for emerging beyond lithium ion technologies. Here, an integrated computational-experimental approach is used to rank-order and aid the selection of suitable electrolytes for a Na-ion battery. We present an in silico strategy based on both thermodynamic and kinetic descriptors derived from molecular dynamics simulations to rationally arrive at optimal electrolytes for Na-ion batteries. We benchmarked various electrolytes (pure and binary mixtures of cyclic and acyclic carbonates with NaClO4 salt) to identify appropriate formulations with the overarching goal of simultaneously enhancing cell performance while meeting safety norms. Fundamental insights from computationally derived thermodynamic and kinetic data considerations coupled with atomistic-level description of the solvation dynamics is used to rank order the various electrolytes. Thermodynamic considerations based on free energy evaluation indicate EC:PC as a top electrolyte formulation under equilibrium conditions. However, kinetic descriptors which are important factors dictating the rate capability and power performance suggest EC:DMC and EC:EMC to be amongst the best formulations. Experimental verification of these optimized formulations was carried out by examining the electrochemical performance of various electrolytes in Na/TiO2 nanotubes half cells with NaClO4 salt. Our rate capability studies confirm that EC:DMC and EC:EMC to be the best formulations. These optimized formulations have reversible specific capacities ~180-240 mAh/g whereas the lower ranked electrolytes (EC:DEC) have capacities ~100 mAh/g. The various electrolytes are also evaluated from a safety perspective. Such results suggest encouraging prospects for this approach in the a priori prediction of optimal sodium ion systems with possible screening implications for novel battery formulations.
Mediating Gel Formation from Structurally Controlled Poly(ionic liquids): Towards Ionic Gel Electrolytes for Energy Storage
Authors: Srour Hassan , Ratel Olivier , Leocmach Mathieu , Denis-Quanquin Sandrine , Appukuttan Vinukrishnan , Taberlet Nicolas , Majesté Jean-Charles , Carrot Christian , Manneville Sebastien , Andraud Chantal , Bucher Christophe , Monnereau Cyrille
Published: February 2020

Most sustainable energy sources (solar, hydropowered, geopowered, windpowered) rely on the production of electrical energy. In the last decade, Lithium ion based batteries have emerged as interesting candidates as high-density energy storage devices, enabling the developments of electrical vehicles of constantly growing autonomies. The synthesis of polymer electrolytes and the study of their electrochemical properties is currently a very active topic. Poly(ionic liquids) (PILs), in particular, constitute an increasingly sought-after category of materials, as they are expected to replace flammable, leakage-prone organic solvent electrolytes in future energy storage devices.[1,2]

In this communication, we will present a novel synthetic methodology, which provides an easy access to a broad range of PILs from a common monomeric precursor (figure 1). Owing to this straightforward conceptual approach, it is possible to precisely control the structure of the polymeric materials. We will show how the introduction of an anionic functional group on the ATRP initiator is enough to mediate gel formation at low concentrations through electrostatic interactions (Figure 2).[3,4]
We will then demonstrate that the incorporation of different additives along the polymer backbone helps optimizing ionogel properties in different electrolytic solvents to form gel electrolyte. Finally, we will illustrate the potential of the resulting gels as quasi-solid materials for energy storage applications through the study of different parameters: its rheological behaviour, electrochemical stability, diffusion and ionic conductivity properties.

[1] Yoshizawa, M.; Ogihara, W.; Ohno, H. Polym.
Adv. Technol.
2002,
13, 589-594.

[2] Wang, P.; Zakeeruddin, S. M.; Moser, J. E.; Nazeeruddin, M. K.; Sekiguchi, T.; Gratzel, M. Nat Mater
2003,
2, 402-407.

[3] Appukuttan, V. K.; Dupont, A.; Denis-Quanquin, S.; Andraud, C.; Monnereau, C. Polym. Chem.
2012,
3, 2723-2726.

[4] Srour, H.; Ratel, O.; Leocmach, M.; Adams, E. A.; Denis-Quanquin, S.; Appukuttan, V.; Taberlet, N.; Manneville, S.; Majesté, J.-C.; Carrot, C.; Andraud, C.; Monnereau, C. Macromol.
Rapid Commun.
2014, DOI: 10.1002/marc.201400478.

Figure 1