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The intercalation rate of Li + -ions in flake natural graphite (two-dimensional) with particle size from 2 to 40 μm and sphere-like graphite (three-dimensional), 12 to 40 μm in particle size, was investigated. The amount of Li + ions that intercalate at different rates was determined from measurement of the reversible capacity during de-intercalation in 1 M LiClO 4 /1:1 (volume ratio) ethylene carbonate—dimethyl carbonate. The key issues in this study are the role of the particle size and fraction of edge sites on the rate of intercalation and de-intercalation of Li + ions. At low specific current (15.5 mA/g carbon), the composition of lithiated graphite approaches the theoretical value, x =1 in Li x C 6 , except for the natural graphite with the largest particle size. However, x decreases with an increase in specific current for all particle sizes. This trend suggests that slow solid-state diffusion of Li + ions limits the intercalation capacity in graphite. The 3D natural graphite with a particle size of 12 μm may provide the optimum combination of reversible capacity and irreversible capacity loss in the electrolyte and discharge rates used in this study.

An electrochemical cell using an electrode of expanded metal (EXMET ® ) is demonstrated. The sheet of EXMET ® contains voids with open volume and geometric arrangement that are capable of locally absorbing any lateral expansion. Consequently, all cumulative changes in the plane of the EXMET ® , when an Li–Al alloy is initially formed, are avoided. Three configurations of electrochemical generators utilizing cathodes of V 2 O 5 , FePO 4 and LiCoO 2 are described. Studies of alloy and dense anode sheets with local stress relaxation were demonstrated by in situ optical microscopy (OM) and scanning electron microscopy (SEM) using expanded metal. These studies indicate that a dense anode offers advantages for application in SPE-cells, including safety, long life and reliability.

Li4Ti5O12 was obtained by solid-state reaction of a ternary precursor mixture, TiO2, Li2CO3 and carbon. The influences of the reaction time, temperature and mixing method on the electrochemical performance of Li4Ti5O12 were investigated. Electrochemical measurements and XRD diffraction characterization were used to determine the reversible capacity and TiO2 residue in the final powder, respectively. Between 1.2 and 2.0 V versus Li, a reversible capacity as high as 165 mAh/g at 7.3 mA/g was obtained.

LiFePO{sub 4}/gel/natural graphite (NG) cells have been prepared and cycled under a fixed protocol for cycle and calendar life determination. Cell compression of 10 psi was found to represent an optimal balance between cell impedance and the first cycle losses on the individual electrodes with the gel electrolyte. Cells with a Li anode showed capacities of 160 and 78 mAh/g-LiFePO{sub 4} for C/25 and 2C discharge rates, respectively. Rapid capacity and power fade were observed in the LiFePO{sub 4}/gel/NG cells during cycling and calendar life studies. Diagnostic evaluations point to the consumption of cycleable Li though a side reaction as the reason for performance fade with minimal degradation of the individual electrodes.

Graphitized carbons have played a key role in the successful commercialization of Li-ion batteries. The physicochemical properties of carbon cover a wide range; therefore identifying the optimum active electrode material can be time consuming. The significant physical properties of negative electrodes for Li-ion batteries are summarized, and the relationship of these properties to their electrochemical performance in nonaqueous electrolytes, are discussed in this paper.

In these presentation, we will present the data and movies of several an operando techniques to study lithium ion and solid state batteries such in situ SEM, In situ TEM, in situ Raman spectroscopy , in situ X-ray diffraction and in situ UV visible. These studies help to understand several mechanism such volume expansion of anodes such lithium metal (20 %), Graphite (10 %), LTO (0 %) and another example the measurements of the thickness of anode, cathode and electrolyte during charge discharge. The mechanism of lithium dendrite was also study and details will be shown during this presentation. Bleand Lithium/solid polymer electrolyte (SPE)/sulfur cells were studied in operando by two techniques: Scanning Electron Microscope (SEM) and ultraviolet-visible absorption spectroscopy (UV-vis). During the operation of the cell, extensive polysulfide dissolution in the solid polymer electrolyte (cross-linked polyethylene oxide) leads to the formation of a catholyte. A clear micrograph of the thick passivation layer on the sulfur-rich anode and the decreased SPE thickness by cycling confirmed the failure mechanism; the capacity decays by reducing the amount of active material, and by contributing to a charge inhibiting mechanism called polysulfide shuttle. The formation of elemental sulfur is clearly visible in real time during the charge process beyond 2.3 V. The non-destructive in operando UV-vis study also shows the presence of characteristic absorption peaks evolving with cycling, demonstrating the accumulation of various polysulfide species, and the predominant formation of S4 2- and of S6 2- during discharge and charge, respectively. This finding implies that the charge and discharge reactions are not completely reversible and proceed along different pathways.

There is a constant drive to improve the specific energy and energy density of the state-of-the-art lithium-ion battery. High energy can be achieved by either choosing a cathode material that operates at a higher potential or has a higher specific capacity. Compared with the conventional 4-V cathodes such as LiCoO2 (LCO), LiNi x Co y Al z O2 (NCA), LiMn2O4 (LMO) and 3.5-V LiFePO4 (LFP), LiCoPO4 (LCP) operates at 4.8 V (vs. Li/Li+) with a theoretic capacity of 167 mAh g-1, resulting in a specific energy of ~800 Wh kg-1, which is about 25% higher than those of the conventional LFP and LMO lithium-ion batteries. Although Co is more expensive than the other transition metals, the energy cost of LCP is expected to be cheaper than all commercialized lithium-ion batteries on the market [1] due to the improved energy density (FIG.1). However, LCP suffers from severe capacity fade due to the low intrinsic electronic/ionic conductivity, structure deterioration and electrolyte decomposition [2]. In order to improve the cyclability and reduce the cost of LCP, Co ions were partially substituted by cheaper elements such as Fe, Cr and Si etc [3]. Meanwhile, a carbon-coating was used to improve the electronic conductivity of LCP. Electrochemical tests showed that both carbon-coating and substitution greatly improved the cycling performance of LCP, which suggests that the substituted LCP is a very promising cathode candidate for high energy lithium-ion battery. References [1] S. Brutti, S. Panero, ACS Symposium Series, 1140, Chapter 4, 69 (2013). [2] K. Tadanaga, F. Mizuno, A. Hayashi, T. Minami, M. Tatsumisago, Electrochemistry 71, 1192 (2003). [3] J. L. Allen, J. L. Allen, T. Thompson, S. A. Delp, J. Wolfenstine, T. Richard Jow, J. Power Sources, 327, 229 (2016). FIG. 1. Energy density and energy cost of LCP compared with other cathode materials currently used in lithium-ion batteries. Figure 1

The need for environmentally friendly, safe, stable, and low cost materials for application in lithium-ion batteries has led to strong interest in developing olivine-type LiMPO4 (M = Fe, Mn, Co, Ni) cathode materials. Among them, LiFePO4 (LFP) has been extensively studied and commercialized. However, LFP has some special shortcomings in practical applications, such as low potential plateau (3.4 V vs. Li/Li+) and small packing density (due to the inclusion of large-volume carbon), which lead to relatively low specific energy density (580 Wh kg-1). Whereas LiCoPO4 (LCP) in the olivine family has been considered as an attractive cathode candidate due to the large theoretical capacity (167 mAh g-1), high operating voltage (4.8 V vs. Li/Li+) and high specific energy density (800 Wh kg-1). However, LCP suffers from severe capacity fade due to the low intrinsic electronic/ionic conductivity, structure deterioration and electrolyte decomposition [1]. In this work, Hydro Quebec and US Army Research Laboratory dedicated to develop the high voltage olivine cathode. Specifically, partially Co-substitution strategy with a carbon coating was successfully used to improve the cycling stability of LCP cathode [2]. FIG. 1 shows the cyclability of substituted-LCP olivine cathode at room temperature under C/3 rate, from which no obvious capacity loss was observed in 100 cycles. Moreover, phosphate based cathodes may provide higher abuse tolerance than oxides at a given voltage due the strong covalent band of P-O. Therefore, the substituted high voltage LCP olivine cathode has the apparent potential to be a next decade success story in lithium-ion technologies and to find large application in the next generation lithium-ion batteries. References [1] K. Tadanaga, F. Mizuno, A. Hayashi, T. Minami, M. Tatsumisago, Electrochemistry 71, 1192 (2003). [2] J. L. Allen, J. L. Allen, T. Thompson, S. A. Delp, J. Wolfenstine, T. Richard Jow, J. Power Sources, 327, 229 (2016). Figure 1

International audience; The advanced lithium-ion batteries are critically important for a wide range of applications, from portable electronicsto electric vehicles. The research on their electrodes aims to increase the energy density and the powerdensity, improve the calendar and the cycling life, without sacrificing the safety issues. A constant progressthrough the years has been obtained owing to the surface treatment of the particles, in particular the coatingof the nanoparticles with a layer that protects the core region from side reactions with the electrolyte, preventsthe loss of oxygen, and the dissolution of the metal ions in the electrolyte, or simply improve the conductivity ofthe powder. The purpose of the presentwork is to present the different surfacemodifications that have been triedfor three families of positive electrodes: layered, spinel and olivine frameworks that are currently considered aspromising materials. The role of the different coats used to improve either the surface conductivity, or the thermalstability, or the structural integrity is discussed

LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently “plagued” by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially solved by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. To develop colloidally synthesized LiFePO4 nanocrystals (NCs) optimized for high rate applications, we propose here a surface treatment of the NCs. The particles as delivered from the synthesis have a surface passivated with long chain organic surfactants, and therefore can be dispersed only in aprotic solvents such as chloroform or toluene. Glucose that is commonly used as carbon source for carbon-coating procedure is not soluble in these solvents, but it can be dissolved in water. In order to make the NCs hydrophilic, we treated them with lithium hexafluorophosphate (LiPF6), which removes the surfactant ligand shell while preserving the structural and morphological properties of the NCs. Only a roughening of the edges of NCs was observed due to a partial etching of their surface. Electrodes prepared from these platelet NCs (after carbon coating) delivered a capacity of ∼155 mAh/g, ∼135 mAh/g, and ∼125 mAh/g, at 1 C, 5 C, and 10 C, respectively, with significant capacity retention and remarkable rate capability. For example, at 61 C (10.3 A/g), a capacity of ∼70 mAh/g was obtained, and at 122 C (20.7 A/g), the capacity was ∼30 mAh/g. The rate capability and the ease of scalability in the preparation of these surface-treated nanoplatelets make them highly suitable as electrodes in Li-ion batteries., Nano Letters, 14 (12), ISSN:1530-6984, ISSN:1530-6992

We examine the reactivity of the non-aqueous electrolyte at the surface of 5-volts positive electrode materials for Li-ion batteries. LiPF6-based electrolytes include various solutes as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and 1,2-dimethoxyethane (DME), which react with the surface of LiNi0.5Mn1.5O4 in the voltage range 3.0–4.9 V vs. Li0/Li+. Effects with mixed salts and electrolyte additive are also examined.

Lithium-insertion compounds with the spinel structure become active element of a new generation of Li-ion batteries, namely the 4.7-V positive electrodes that improve the technologies of energy storage and electric transportation. The compound considered here is the bulk and surface modified LiMn1.5Ni0.5O4 (LMN) spinel. We report the structural and electrochemical features of Cr-doped LMN phase and the LiFePO4-coated LMN structure. Emphasis is placed on the control of physical properties that is needed to guarantee the reliability and the optimum electrochemical performance of these materials.

We report that the rotation speed of the stirring in the hydrothermal reactor process is an important parameter that affects the structural properties and the electrochemical performance of LiFePO4. The best results are obtained for a rotation speed of 280 revolutions per minute. It is argued that this improved performance is related to the optimized morphology of the particles, and a smaller agglomeration of the particles. Since this material meets a worldwide success as a positive electrode for commercial Li-ion batteries.

Li-ion batteries with high power and high energy are used for new applications such as electric vehicles, for which safety concern is essential. We review the state of the art in the research to optimize the safety of all the elements of the batteries already available on the market. We also report on the recent batteries that are not yet commercialized, but have been tested as demonstrators, which pass all the security tests without the help of any battery monitoring system with almost unlimited cycling life, which is expected to reduce significantly the cost of the electric vehicles.

In situ X-ray diffraction has been carried out to study the structural changes of the bare and Cr-doped LiMn1.5Ni0.5O4 crystallized samples in the disordered phase (Fd m space group) are investigated during the galvanostatic charge/discharge process at C/24 rate. The de-intercalation of lithium proceeds through a series of first-order phase transitions with two regions of two-phase coexistence. The phase diagram is analyzed and discussed, together with the differences among different results reported in the literature.

International audience; A series of metal-doped LiMn1.5Ni0.5O4 (metal ¼ Co, Al, Cu and Mg) positive electrode materials for lithium ion batteries were synthesized and their structural changes during the galvanostatic charge/ discharge process at C/24 rate were investigated by using in situ X-ray diffraction (XRD) measurements. The phase diagram shows that similar series of first-order phase transitions with two regions of twophase coexistence are observed during intercalation/de-intercalation of lithium among all the doped cathode materials. However, minor differences of the phase evolution and the electrochemical properties point to the different roles of the dopant ions. The phase diagram is analyzed and discussed, together with the differences among different results reported in the literature to distinguish between general intrinsic properties of spinel and sample-dependent properties due to the degree of cation ordering, outof- equilibrium effects, electro-negativity and radii of the dopant ions. Among the metal-substituted samples, we argue that the Co-doping is the most promising approach with improved electrochemical property.

The intercalation rate of Li + -ions in flake natural graphite with particle size that ranged from 2 to 40 μm was investigated. The amount of Li + -ions that intercalate at different rates was determined from measurement of the reversible capacity during deintercalation in 1 M LiClO 4 /1:1 (volume ratio) ethylene carbonate–dimethyl carbonate. The key issues in this study are the role of particle size and fraction of edge sites on the rate of intercalation and deintercalation of Li + -ions. At low specific current (15.5 mA/g carbon), the composition of lithiated graphite approaches the theoretical value, x =1 in Li x C 6 , except for the natural graphite with the largest particle size. However, x decreases with an increase in specific current for all particle sizes. This trend suggests that slow solid-state diffusion of Li + -ions limits the intercalation capacity in graphite. The flake natural graphite with a particle size of 12 μm may provide the optimum combination of reversible capacity and irreversible capacity loss in the electrolyte and discharge rates used in this study.

The irreversible capacity loss (ICL) that is observed with carbons in Li-ion batteries is associated with electrolyte decomposition. In this paper, we present the results of an analysis to illustrate the role that the edge and basal plane sites play on the ICL and first-cycle coulomb efficiency of flake-like natural graphite. A model of an ideal graphite particle, which is depicted as an ideal prismatic structure, is used to develop an understanding of the correlation of the fraction of edge sites and particle size for flake-like and cube structures. In the case of flake-like graphite, thin flakes have higher surface area and higher ICL than thicker flakes, even though the fraction of edge sites is lower. On the other hand, the cube structure has a high fraction of edge sites but a low ICL and low surface area. The analysis presented here suggests that the particle morphology and the surface area associated with the edge and basal plane sites play a significant role in the electrochemical performance of graphite in Li-ion batteries.

Electrolyte decomposition and the formation of a solid electrolyte interphase (SEI) layer occur during the initial charge/discharge cycles of carbon in electrolytes used in Li-ion batteries. This paper describes our approach to characterize the formation of SEI layers on various carbonaceous materials by in situ ellipsometry. Five types of carbon samples (carbon films on glass, pyrolyzed photoresist on silicon, highly oriented pyrolytic graphite and natural graphite) with specular surfaces were characterized by Raman spectroscopy and in situ ellipsometry/electrochemical studies in ethylene carbonate–dimethyl carbonate containing a lithium salt. Raman spectroscopy showed that the carbons films deposited on glass contain broad overlapping peaks from 900 to 1700 cm −1 , which is indicative of the highly disordered nature of the carbon films. Changes in the ellipsometric parameters, Δ and ψ , were correlated with the formation of the SEI layer during the initial charge (intercalation) process.

The oxidation kinetics of natural graphite particles (2–40 μm average particle size) with a flake-like morphology were investigated at 933, 982 and 1033 K. The reaction rate in air increased with increase in temperature and with a decrease in particle size of natural graphite. The activation energy, derived from the classical Arrhenius relationship, was 188±2.2 kJ/mol, in good agreement with published results. The activation energies of the natural graphite did not show any systematic trend with particle size. The rate constant, normalized for the area of active sites, is independent of the particle size and Brunauer–Emmet–Teller (BET) surface area, which strongly suggests that the edge sites play a significant role in the oxidation kinetics. This observation is consistent with conclusions reported in the literature that the oxidation kinetics of carbonaceous materials decreases with a decrease in active surface area.

The oxidation of natural graphite particles with a prismatic (flake-like) structure was investigated by thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). The objective of this study is to examine the relationship between the relative fraction of edge sites and the oxidation behaviour of graphite. The approximate prismatic structure of the natural graphite provided a model geometry from which the relative fraction of edge and basal plane sites was determined. The three thermal parameters, ignition temperature (Ti), temperature maximum (Tm) in the DTA curves, and the temperature at which 15% carbon weight loss is attained (T15), were determined for a series of natural graphite samples (average particle size, 2–40 μm) using simultaneous TGA/DTA. The results reported in this study support the observation that the fraction of edge sites has a strong influence on the thermal parameters (Ti, Tm and T15) for the oxidation of graphite.

International audience; Energy storage by batteries has become an issue of strategic importance. A scientific breakthrough in this context is the lithiumion battery. Indeed, lithium-ion batteries can store up to three times more electricity and generate twice the power of nickel–metalhydride batteries now in use, making possible great improvements in energy storage for electric vehicles and portable electronics. Major investments are beingmadefor thecommercial development of Li-ion batteries and there are government funds available offering $billions in grants for research, development, and manufacturing. In this context, we wish to call attention to a deceptive paper that recently appeared in Nature [1], which has receivedmuch publicity since it announced an impossibly high recharging rate capability for a Li-ion battery of 9 s! Close examination of the work [1] shows that the authors have no direct evidence in support of such a high recharging rate, but imply their dramatic conclusion only from the high discharge rate. Experienced batterymaterials scientistswould understand that the charge and discharge processes of batteries are basically asymmetric, resulting in rates of discharge that are generallymuch higher than rates suitable for recharge! The ability of a battery to be rechargedina fewseconds, as the authors claim,would indeed be of great benefit, but this goal remains unmet despite the claims of Kang and Ceder [1] as we will explain herein. The olivine material LiFePO4, used in thework reported by Kang and Ceder [1] is a very promising material that was first proposed in 1996 [2]. Hydro Quebec (HQ) recognized the potential of this material for Li-ion batteries after discussions with Professor John Goodenough in the same year. HQ has much experience with this material and has invested in R&D to promote this material for battery applications in order to make it practical for lithium rechargeable batteries by coating it with carbon [3].

Lithium intercalation of natural graphite and well-graphitized vapor-grown carbon fibers has been investigated by solid-state {sup 7}Li-NMR and by cyclic voltammetry. Chemical shift of {sup 7}Li in Li-graphite intercalation compounds (Li-GICs) of natural graphite occurs in two regions, >40 and

A lithium ion rechargeable battery based on carbon anode that is a viable replacement for lithium metal anode has been developed. In this investigation, the Vapor-Grown Carbon Fiber was used as the anode material of a cylindrical battery. The charge/discharge experiments were carried under various temperatures and current densities. Excellent cyclability was obtained at 21°C at a charge/discharge of 0.8 C with three cathode materials (LiCoO 2 , LiMn 2 O 4 , and LiNiO 2 ). High discharge capacity was obtained at low temperature (0°C). Good cyclability was also obtained at high temperature (40°C). At the charge/discharge rate of 4.0 C, energy density did not decay significantly. Good cyclability was obtained for rates ranging from 0.8 C to 4.0 C. Self-discharge was investigated at 3 temperatures (21, 40 and 60°C). The measured self-discharge was 8, 15 and 31% per month at 21, 40 and 60°C, respectively.

Battery is one of the most used technologies in everyday life (cellular, electric vehicle or hybrid cars). Improvement in the specific capacity (energy by weight or volume) and charging rate has a potential to even significantly improve their used. Hence, the research in battery materials is very important, well founded and will have a direct economical and social impact. Most of the actual battery technology is based on the displacement of Lithium ion (Li) from two active materials (i.e., graphite for the anode and LiFePO4 for the cathode). It is thus essential to determine the distribution and the amount of Li with a good spatial resolution (<< 1 μm) In terms of microstructural characterization Li is very difficult to analysed using conventional detector because it is a very light element and emits low energy x-rays (52 eV). Optical Emission spectrometry and XPS can easily detect Li but without any no good lateral resolution. In counterpart, Li has a relatively high sputtered yield and low backscattered coefficient. Mass spectra have been used in dedicated secondary ion mass microscope (SIMS), either static or Time of Flight (TOF) but with, again, with a limited lateral resolution.

An examination of the electrochemical performance of solid-state lithium-ion batteries was carried out using a solvent-free solid-polymer electrolyte at 60°C. We studied two different types of anode (negative electrode) material: graphite intercalation compound (GIC) or lithium-titanium oxide (Li 4 Ti 5 O 12 ), and LiCoO 2 was used as the cathode (positive electrode). Natural graphite and carbon fiber gave high reversible capacities of about 372 and 300 mAh/g, respectively. A Li 4 Ti 5 O 12 vs. lithium cell discharged at the C/15 rate delivered 155 mAh/g corresponding to a 97% first-cycle Coulombic efficiency. The irreversible capacity was high when carbon material was used as the negative electrode. However, this sacrificial capacity was very small when we replaced carbon with the spinel material. The crystallographic structure of Li 4 Ti 5 O 12 was analyzed by X-ray diffraction, and its stability was demonstrated by in situ scanning electron microscopy using Li 4 Ti 5 O 12 , which is a zero-strain insertion material that offers advantages for the solid-polymer electrolyte cell including safety, long life, and reliability.

International audience; The effect of carbon coating on the properties of LiFePO4 particles is studied from magnetic measurements. Magnetization experiments are an excellent tool to detect very low concentrations of iron-based impurities (< 1 ppm) which are poisoning the phospho-olivine used as positive electrode mate- rial in rechargeable Li-ion batteries. The results indicate that I addition of 5% carbon withdraws traces of the Fe(III) phase such as Fe2P and/or Fe2O3. This carbothermal effect appears to be beneficial for long-term application of LiFePO4 materials in Li-ion batteries. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Actual interpretation of the enhancement of Cu/Zn cementation kinetics by a “cement critical specific mass” is reconsidered. Working with a rotating disk electrode and varying the initial concentration of copper and zinc ions over a large range, we show that copper deposit is not responsible for the kinetic transition. First, cement peeling off does not change the delay for the appearance of the second stage and the amplitude of the kinetic transition is a function of the initial concentration of zinc ions. Furthermore, the first stage duration decreases, and even this stage may disappear, on a substrate precorroded in the same solution replacing copper ions by Ce(IV) ions. On the other hand, the stage duration increases if a constant polarization is imposed to the substrate. Operating conditions at the Zn2+/Zn interface appear to be the essential parameter. Discussion includes morphological examinations.

A study of the electrochemical performance of carbon materials from different types was carried out on true solid polymer-based poly(ethylene oxide) (PEO) with LiTFSI for application as the negative electrode in lithium ion solid-state batteries (LISSBs) at 60 °C. The reversible and irreversible capacity depend strongly on the crystallinity, the form of carbon and the impurities. A comparison of particle versus fiber was done when we investigated the charge/discharge characteristics with different current densities. The galvanostatic curves show high reversibility of the lithium—carbon in solid polymer electrolyte. The kinetics of electrochemical intercalation of lithium into carbon was studied by impedance spectroscopy especially for evaluating the diffusion coefficient in different origins of carbon. The degree of ionization of lithium was investigated by using solid-state 7 Li nuclear magnetic resonance spectroscopy when the electrode is fully intercalated or doped down to 0 V. The chemical shift of 7 Li NMR in lithium intercalation or doping in the carbons was classified in two ranges, 42 ppm and 9 ppm. 7 Li NMR suggests the carbon with a 42 ppm range is the best choice for LISSBs.

Additional electrons injected into lithium peroxide become self-trapped to form polarons. While the final stage of this self-trapping phenomenon has been examined extensively, the electron-phonon interactions that drive this process remain largely unaddressed in the first-principles literature. In order to understand the dynamical process of polaron formation in lithium peroxide, we examine the initial embryonic stage of this process through first-principles calculations of the electron-phonon interaction between the lithium peroxide lattice and an extra electron injected into the crystal. It is shown that the electron-phonon interaction is perceivably strong with such phonons whose vibration patterns map directly onto the lattice distortions that occur when a polaron is actually formed. These patterns indicate the elongation of the bond length of the O${}_{2}^{2\ensuremath{-}}$ ions and contraction of the surrounding Li${}^{+}$ ions.

The bulk electronic properties of LiFePO4 are explored by the self-consistent analysis of both the magnetic properties and electric conductivity. This combination gives evidence that the ionic and electronic conductivity are closely correlated, since the electronic conductivity is due to the migration of lithium vacancies. The results are compared with the results of the calculations of the formation energy of the native defects in this material.

International audience; LiFePO4 has emerged as the winning cathode material for a new generation of Li-ion batteries that are increasingly used for hybrid and electric vehicles, due to its remarkable electrochemical properties. The present review gives the state of the art in the understanding of the properties of this material and the other members of the same family. We discuss the effects of the decrease of the size of the particles down to circa 20 nm; some of them have been misunderstood or are still open questions. All of them are important to determine the trends in the research and development on this family of materials in the future. The cells' properties are also reviewed with both the graphite and more recently the Li4Ti5O12 anodes, the last one providing outstanding performance in terms of cycling life and power that make them promising not only for electric vehicles, but also to solve for intermittence locally in smart grids

We report recent progress in surface control of cathode element particles. Re-crystallization of the surface layer can be obtained not only in olivines, but also in lamellar compounds, which results in an increase of the electrochemical properties. In addition, we take benefit of the stability of LiFePO4 and the fact that it does not need protection against overcharge, by synthesizing multi-component particles formed by a core particle with higher working potential like LiMnPO4 (4 V cell) and even LiMn1.5Ni0.5O4 (5 V cell) surrounded by LiFePO4 coated with carbon to the particles with LiFePO4. The remarkable improvement of the electrochemical properties obtained in this process gives evidence that the synthesis of such multi-component composites are promising to improve the energy density and high-rate performance of Li-ion batteries in the near future.

γ-MnO 2 has been synthesized by hydrothermal process, and studied as electrode material in aqueous asymmetric super-capacitor. We studied the blend formed by electrochemical polymerization of pyrrole deposited onto γ-MnO 2 particles. The composite materials (PPy/MnO 2 ) were characterized by different methods including cyclic voltammetry, chronoamperometry, X-ray diffractometry and BET measurements. The specific capacitance at constant current density 2 mA cm −2 was calculated from galvanostatic charge-discharge cycling tests. The asymmetric super-capacitor using (PPy/MnO 2 ) composite material has high specific capacitance of 141.6 F g −1 compared with 73.7 F g −1 for γ-MnO 2 before PPy coating. The improvement of the coating is not only due to the electronic conductivity of the polymer, but also due to an increase of the BET surface area that raises to 125 m 2 g −1 after coating, against 64 m 2 g −1 for pristine MnO 2 .

The stacking order of graphite layers in mesocarbon microbeads (MCMBs) heat-treated between 700 and 3,000 C was examined by analyses of X-ray diffraction measurements, and lithium insertion into the MCMBs has been observed using solid-state {sup 7}Li-nuclear magnetic resonance ({sup 7}Li-NMR) spectroscopy. In MCMBs heat-treated above 2,000 C, the fully lithiated MCMBs showed two bands at ca. 45 ppm (vs. KiCl) and ca. 27 ppm in their {sup 7}Li-NMR spectra. The profile of the band at 45 ppm was very close to that for the first-stage lithium graphite intercalation compound (Li-GIC), though the other band at 27 ppm could not be assigned to any phases of Li-GICs. From these results, it is suggested that the structures of the MCMBs heat-treated above 2,000 C for lithium insertion are classified as graphitic structure, which has the AB stacking order of graphite layers, and turbostatic structure with a random stacking sequence of graphite layers; the fully lithiated compositions of both structures were estimated as LiC{sub 6} and ca. Li{sub 0.2}C{sub 6}, respectively. Although MCMB heat-treated at 700 C gave a higher capacity than LiC{sub 6}, the line shift in the {sup 7}Li-NMR spectra indicated that lithium stored in the MCMB displayed an ionic more » character. Capacity change of the MCMBs during charge-discharge cycling up to 20 cycles and capacity loss at higher current densities (

Zero-strain and long-term stability of nanoscale lithium titanate (LTO) anode materials make possible the fabrication of exceptionally stable lithium ion batteries. But one issue must be considered that of nanostructure-induced relaxation in 2D LTO nanosheets which profoundly modifies their Li storage properties and structural stability. Excessively intercalated Li ions at both 8a and 16c sites trigger nucleation of the relaxed LTO structure in the near-surface region, which impedes Li-ion diffusion and causes the increasing polarization of LTO nanosheet electrodes. Nuclei of relaxed LTO then undergo isotropic growth along the 3D Li-ion pathways in LTO to completely convert near-surface regions into relaxed LTO. With increasing population of trapped Li ions, the enhanced conductivity due to Ti4+/Ti3+ reduction gradually eliminates the raised polarization. In the meantime, spontaneous electrolyte/LTO reduction to form the solid electrolyte interphase starts playing a major role in capacity loss once the transformation of near-surface region into relaxed LTO becomes saturated. Elucidation of these fundamental intercalation-induced surface structure transformations contribute greatly into the design of highly performing 2D nanoscaled LTO and other electrode materials.

Lithium metal orthosilicate cathode materials (Li2(Fe,Mn)SiO4 denoted as LMS) have been the subject of significant research interest for the past 10 years because of the high theoretical capacity nearly two times higher than that of the analogous polyanion cathode LiFePO4 (165 mAh/g), if the two lithium ions could be fully extracted and re-inserted in multiple charge/discharge cycles. Despite significant progress, a series of critical issues-questions relating to this strategically important family of cathode materials remain open hampering their full development. One such critical issue is the mechanism of Li ion storage namely, solid-solution behavior (single-phase) vs. two-phase reaction. In analogy with the well understood two-phase separation Li storage mechanism of LiFePO4 cathode the dominant view among those investigating the orthosilicate system is that we have also a two-phase mechanism between monoclinic (P21/n) Li2FeIISiO4 and orthorhombic (Pmn21) one-Li delithiated LiFeIIISiO4. However, in many of these studies the generated discharge curves are not flat but are slanted. Such behavior has been attributed to polarization effects without further characterization leaving an important gap in our understanding. With the view of clarifying this issue we have conducted first principle calculations (1) and in situ (unpublished) and ex situ (submitted) synchrotron XRD and XANES (Fe K-edge and L-edge; Si K-edge and Oxygen K-edge) characterizations of nanostructured LFS cathode in terms of structure evolution and charge compensation at different states of charge (Li(2-x)FeSiO4, x=0, 0.25, 0.50, 0.75, 1.0). This is done by charging/discharging LFS at low current (C/50) to allow for structure relaxation hence unequivocal (quasi-equilibrium condition) probing of the Li storage mechanism: solid solution vs. two-phase reaction. Furthermore, cycling is not limited to the first cycle but is extended to several cycles. For the study we employ a mixed phase (monoclinic/orthorhombic) nanograined Li2FeSiO4 material synthesized via organic-assisted hydrothermal precipitation and annealing at 400 °C (2,3). The data clearly point out towards solid solution mechanism- a finding that should bring new perspective in our pursuit of unlocking the full capacity advantage of the orthosilicate Li-ion host structure. Acknowledgments This work is supported through a Hydro-Québec/Natural Sciences & Engineering Research Council of Canada (NSERC) Collaborative R&D research grant. DTJ acknowledges NSERC support for the work done at the University of Guelph. Synchrotron radiation measurements were performed at the Canadian Light Source, which is supported by CFI, NSERC, University of Saskatchewan, Province of Saskatchewan, Western Economic Diversification Canada, NRC Canada, and CIHR. References 1. Lu, X.; Chiu, H.-C.; Bevan, H. K.; Jiang, D.-T.; Zaghib, K.; Demopoulos, P. G., Density functional theory insights into the structural stability and Li diffusion properties of monoclinic and orthorhombic Li2FeSiO4 cathodes, Journal of Power Sources, 2016, 318, 136-145. 2. Lu, X.; Wei, H. J.; Chiu, H. C.; Gauvin, R.; Hovington, P.; Guerfi, A.; Zaghib, K.; Demopoulos, G. P. Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals, Scientific Reports, 2015, 5, 8599. 3. Arthur, Z.; Chiu, H.-C.; Lu, X.; Chen, N.; Emond, V.; Zaghib, K.; Jiang, D.-T.; Demopoulos, G. P. Spontaneous reaction between uncharged lithium iron silicate cathode and LiPF6-based electrolyte, ChemComm, 52 (2015) 190-193.

This paper will present the results for the determination of concentration of Li in silicates cathode materials using x-ray microanalysis with windowless SDD EDS technology and with Electron Energy Loss Spectroscopy (EELS) with state of the art field emission scanning electron microscopes at high spatial resolution. Advantages and disadvantages of both techniques will be covered. The aim of this work is to characterize Li concentration variation at the nm scale in batteries materials. The issue of electron beam damage will be covered and the advantage to work at electron beam energies below 30 keV will be demonstrated.

Based on neutron powder diffraction (NPD), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), Electron Energy Loss Spectroscopy (EELS), X-Ray Photoelectron Spectroscopy (XPS) we show that Fe-antisites defects are surface defects (see Figure 1) and slowly eliminated by Fe-Li cation exchange during standard hydrothermal synthesis1. Recently2 we demonstrated that the calcium ions help eliminate the Fe antisite defects by controlling the nucleation and evolution of the LiFePO4 particles during their hydrothermal synthesis. The final Ca:LFP particles present Fe-antsite defects confined in a thin surface layer compared to standard LFP. Fig. 1. Figure 1: Schematic representation of Fe-antisite defects elimination during standard hydrothermal synthesis of LFP Reference 1. Paolella, A. et al. Cation exchange mediated elimination of the Fe-antisites in the hydrothermal synthesis of LiFePO 4. Nano Energy 16, 256–267 (2015). 2. Paolella, A. et al. Accelerated Removal of Fe-Antisite Defects while Nanosizing Hydrothermal LiFePO 4 with Ca 2+. Nano Lett. 2–7 (2016). doi:10.1021/acs.nanolett.6b00334 Figure 1

In an attempt to enhance the microstructural and electrochemical (EC) properties, LiCoO2 thin films were doped with titanium or zirconium. RF magnetron sputtering technique has been employed for the deposition of films on Au/Ti/SiO2/Si substrates from lithium-rich LiCoO2 target with mosaic configuration. The as-deposited and Ti- and Zr-doped LiCoO2 thin films at lower doping concentration exhibited the α-NaFeO2 structure with R-3 m symmetry as confirm from X-ray diffraction and Raman studies. The cyclic voltammogram of micro-electrodes in aqueous electrolyte exhibited perfect redox peaks with good reversibility. The chronopotentiometry studies revealed that the discharge capacity of pure LiCoO2 was 64 µAh cm-2 µm-1, while 2% Ti- and Zr-doped films showed enhanced capacities 69 and 68 µAh cm-2 µm-1 (248 mC cm-2 µm-1, 245 mC cm-2 µm-1) respectively. The Zr-doped films exhibited good structural stability even after 25 cycles with the capacity retention of 95%. The kinetics of lithium ions in pure and Ti/Zr-doped LiCoO2 thin film cathodes and their cycleability are studied using both aqueous Pt//LiCoO2and and non-aqueous Li//LiCoO2 cells and the results will be presented.

This paper presents recent progress in Li-ion batteries with the active sub-micron sized particles of the positive electrode chosen in the family of lamellar compounds LiMO2 where M stands for a mixture of Ni, Mn elements, and in the family of yLi2MnO3•(1-y)LiNi½Mn½O2 layered-layered integrated materials. The structural, physical and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters that include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M elements and composition y. Their electrochemical properties are also reported and discussed, to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling.

Blended cathode materials made by mixing LiFePO4 (LFP) with LiMnPO4 (LMP) or LiNi1/3Mn1/3Co1/3O2 (NMC) that exhibit either high specific energy and high rate capability were investigated. The layered blend LMP-LFP and the physically mixed blend NMC-LFP are evaluated in term of particle morphology and electrochemical performance. Results indicate that the LMP-LFP (66:33) blend has better discharge rate than the LiMn1-yFeyPO4 with the same composition (y=0.33) and NMC-LFP (70:30) delivers a remarkable stable capacity over 125 cycles. Finally, in situ voltage measurement methods were applied for the evaluation of the phase evolution of blended cathodes and gradual changes in cell behaviour upon cycling.

Prof. Ogumi is one the leading pioneers of lithium-ion technology in Japan and worldwide. His research studies on battery materials include LiCoO2, graphite, and highly oriented pyrolytic graphite (HOPG), Much of his research involved in situ techniques that utilized X-ray, Raman spectroscopy and atomic force spectroscopy (AFM) to investigate the SEI (passivation layer) and lithium intercalation in graphite and HOPG in propylene carbonate (PC)- and ethylene carbonate (EC)-based electrolytes. In this presentation, we will show data and video movies that were obtained during studies of lithium-ion and solid-state batteries using various In operando studies and in situ techniques involving scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction and ultraviolet-visible absorption spectroscopy (UV-vis). These in situ studies are helpful to understand the mechanisms for volume expansion of anodes consisting of lithium metal (20 %), graphite (10 %) and LTO (0 %). Another example that will be discussed is the dimensional changes of the anode, cathode and electrolyte that occur during charge/discharge. The mechanism of lithium dendrite formation was also studied, and details will be discussed in this presentation. [Don’t know what is meant by Bleand and deleted because I‘m not sure it is needed.] Lithium/solid polymer electrolyte (SPE)/sulfur cells were studied by two in situ techniques: SEM and UV-vis. During the operation of the cell, extensive polysulfide dissolution in the solid polymer electrolyte (cross-linked polyethylene oxide) leads to the formation of a catholyte. A clear micrograph was obtained of the thick passivation layer on the sulfur-rich anode and the decreased SPE thickness during cycling confirmed the failure mechanism; the capacity decays by reducing the amount of active material, which contributes to a charge inhibiting mechanism called polysulfide shuttle. The formation of elemental sulfur is clearly visible in real time during the charge process beyond 2.3 V. The non-destructive UV-vis also shows the characteristic absorption peaks that evolve with cycling, demonstrating the accumulation of various polysulfide species, and the predominant formation of S4 2- and of S6 2- during discharge and charge, respectively. This finding implies that the charge and discharge reactions are not completely reversible and proceed along different pathways.

We describe a new device able to photo-oxidize LiFePO4 nanocrystals to FePO4 in the presence of a N719-Ruthenium-dye using a three-electrode system. Under Open Circuit Voltage (OCV) the LiFePO4 nanoparticles spontaneously delithiated and converted to heterosite FePO4 with the assistance of the ruthenium-dye (see Figure 1). Our results can open interesting perspectives to solar rechargeable battery field. Figure 1 : a-c) XRD pattern and HRTEM of LiFePO4 nanocrystals, b-d) XRD pattern and HRTEM image of FePO4 nanocrystals, e) Charging of LiFePO4 by N719 dye in presence of the light followed by an open circuit voltage (OCV) Figure 1