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All-solid-state batteries are intensively investigated, although their performance is not yet satisfactory for large-scale applications. In this context, the combination of Li10GeP2S12 solid electrolyte and LiNi1-x-yCoxMnyO2 positive electrode active materials is considered promising despite the yet unsatisfactory battery performance induced by the thermodynamically unstable electrode|electrolyte interface. Here, we report electrochemical and spectrometric studies to monitor the interface evolution during cycling and understand the reactivity and degradation kinetics. We found that the Wagner-type model for diffusion-controlled reactions describes the degradation kinetics very well, suggesting that electronic transport limits the growth of the degradation layer formed at the electrode|electrolyte interface. Furthermore, we demonstrate that the rate of interfacial degradation increases with the state of charge and the presence of two oxidation mechanisms at medium (3.7 V vs. Li+/Li < E vs. Li+/Li) and high (E ≥ 4.2 V vs. Li+/Li) potentials. A high state of charge (>80%) triggers the structural instability and oxygen release at the positive electrode and leads to more severe degradation.

Lithium distribution in the composite electrode of an all-solid-state lithium battery was analyzed by microbeamparticle-induced X-ray emission and gamma-ray emission techniques. Two kinds of pellet-type cells, incorporating LiCoO2 as the cathode-active material and the superionic conductor Li10GeP2S12 as the solid electrolyte, were prepared: one in the as-prepared state and the other in the charged state. Changes in the lithium distribution near the interface of the composite cathode and separator were visualized by normalizing lithium/cobalt and lithium/ germanium intensity. Lithium extraction from LiCoO2 due to charging was confirmed by the decrease in normalized intensity at the cathode composite region. The evaluation of the lithium concentration variation in the composite electrode for the all-solid-state battery during the electrochemical reactions could provide essential information for construction of a favorable composite electrode to enable preparing high-performance all-solid-state lithium batteries.

Perovskite-type lithium ionic conductors were explored in the (LixLa1&minus, x/3)ScO3 system following their syntheses via a high-pressure solid-state reaction. Phase identification indicated that a solid solution with a perovskite-type structure was formed in the range 0 &le, x &lt, 0.6. When x = 0.45, (Li0.45La0.85)ScO3 exhibited the highest ionic conductivity and a low activation energy. Increasing the loading of lithium as an ionic diffusion carrier expanded the unit cell volume and contributed to the higher ionic conductivity and lower activation energy. Cations with higher oxidation numbers were introduced into the A/B sites to improve the ionic conductivity. Ce4+ and Zr4+ or Nb5+ dopants partially substituted the A-site (La/Li) and B-site Sc, respectively. Although B-site doping produced a lower ionic conductivity, A-site Ce4+ doping improved the conductive properties. A perovskite-type single phase was obtained for (Li0.45La0.78Ce0.05)ScO3 upon Ce4+ doping, providing a higher ionic conductivity than (Li0.45La0.85)ScO3. Compositional analysis and crystal-structure refinement of (Li0.45La0.85)ScO3 and (Li0.45La0.78Ce0.05)ScO3 revealed increased lithium contents and expansion of the unit cell upon Ce4+ co-doping. The highest ionic conductivity of 1.1 &times, 10&minus, 3 S cm&minus, 1 at 623 K was confirmed for (Li0.4Ce0.15La0.67)ScO3, which is more than one order of magnitude higher than that of the (LixLa1&minus, x/3)ScO3 system.

The establishment of three-electrode cells for all-solid-state lithium-ion batteries is an important issue to clarify the electrochemical behavior of the battery components and solve problems for the practical applications. Here we prepared an all-solid-state three-electrode cell with a chemically-reduced Li4Ti5O12 reference electrode and investigated electrochemical properties of a LiCoO2 composite electrode in a Li-In|Li10GeP2S12|LiCoO2 cell. Plateau potentials in charge-discharge curves were coincident with reported values. Cell impedance measured with two-electrode configuration agreed well with the sum of the impedances of the positive and the negative electrodes measured with the reference electrode. These results show that chemically-reduced Li4Ti5O12 reference electrode was worked as a Li7Ti5O12|Li4Ti5O12 reference electrode and electrochemical properties of the LiCoO2 electrode and the Li-In electrode were separated. From the temperature and the state of charge dependences of LiCoO2 impedance, resistances related to interface or interphase and charge-transfer reaction were identified. These results show that all-solid-state cells with chemically-reduced Li4Ti5O12 reference electrodes are promising candidates for three-electrode cells for all-solid-state lithium-ion battery systems.

Epitaxial LiNi1/3Co1/3Mn1/3O2 film electrodes with orientations of (104), (1−18) and (003) were fabricated on SrRuO3/SrTiO3 by pulsed laser deposition. The films have a thickness of 23.8 to 25.0 nm and a flat surface with a roughness of approximately 2 nm, which offered a model system for clarifying the reaction plane dependencies of lithium intercalation at the LiNi1/3Co1/3Mn1/3O2 surface. All reaction planes delivered reversible lithium intercalation for electrochemical charging–discharging between 3.0 V and 4.3 V (vs. Li/Li+). The (104) surface exhibited reversible behavior at a higher operation voltage between 3.0 V and 4.5 V, but the (1−18) and (003) planes showed fading of the discharge capacity and average discharge voltage. The anisotropic stability of the surface region indicates the importance of crystallographic facet control for the development of an LiNi1/3Co1/3Mn1/3O2 cathode with high cycle stability.

Novel lithium-ion (Li+)-conducting oxysulfides of the Li10GeP2S12 family were found in the ternary Li2S–P2S5–P2O5 system; Li10GeP2S12-type solid solutions with compositions Li3 + 5xP1 − xS4 − zOz (x = 0.03–0.08, z = 0.4–0.8) were confirmed. The solid solutions showed ionic conductivities from 4.14 × 10− 5 to 2.64 × 10− 4 S cm− 1 at 298 K and a wide electrochemical window of 0–5.0 V (vs. Li/Li+). Among the solid solutions synthesized, the purest phase had the composition Li3.35P0.93S3.5O0.5 (x = 0.07, z = 0.5). Structural analysis revealed that the novel oxysulfides are isostructural to the original Li10GeP2S12 structure and the (P/□)(S/O)4 tetrahedra, which indicates the presence of cation defects with oxygen substitution in the crystal structure. Electrochemical stability of the oxysulfides was confirmed in the voltage range of 0–5.0 V. The solid-electrolyte interphase (SEI) resistivity and its cycle-dependence evaluation for new materials demonstrated that the oxysulfides had lower resistivities and furnished well-contacted SEI layers during the charge–discharge process.

In general, the ionic conductivity of sulfide glasses decreases with their crystallization, although it increases for a few sulphide glasses owing to the crystallization of a highly conductive new phase (e.g., Li7P3S11: 70Li2S-30P2S5). We found that the ionic conductivity of 75Li2S-25P2S5 sulfide glass, which consists of glassy and crystalline phases, is improved by optimizing the conditions of the heat treatment, i.e., annealing. A different mechanism of high ionic conductivity from the conventional mechanism is expected in the glassy phase. Here, we report the glassy structure of 75Li2S-25P2S5 immediately before the crystallization by using the differential pair distribution function (d-PDF) analysis of high-energy X-ray diffraction. Even though the ionic conductivity increases during the optimum annealing, the d-PDF analysis indicated that the glassy structure undergoes no structural change in the sulfide glass-ceramic electrolyte at a crystallinity of 33.1%. We observed the formation of a nanocrystalline phase in the X-ray and electron diffraction patterns before the crystallization, which means that Bragg peaks were deformed. Thus, the ionic conductivity in the mixture of glassy and crystalline phases is improved by the coexistence of the nanocrystalline phase.

For the lithium super-ionic conductor Li 10 GeP 2 S 12 , the partial substitution of sulfur by oxygen is achieved via a solid-state reaction. The solid-solution range of oxygen is found to be 0 ≤ x 10 GeP 2 S 12− x O x . Structure refinements using synchrotron X-ray diffraction data confirm the preference for oxygen substitution in the PS 4 tetrahedra. The local structural change in the P(S/O) 4 tetrahedra upon substitution is also indicated by Raman spectroscopy. Ionic conduction properties are maintained even after the oxygen substitution in Li 10 GeP 2 S 12 ; the ionic conductivity of Li 10 GeP 2 S 12− x O x (0.3 ≤ x ≤ 0.6) ranges from 1.03 × 10 −2 to 8.43 × 10 −3 S cm −1 at 298 K. No redox current is observed by cyclic voltammetry from nearly 0 to 10 V versus Li/Li + except for that due to the lithium deposition/dissolution reactions. All-solid-state batteries using Li 10 GeP 2 S 12− x O x ( x = 0.3 and 0.6) as solid electrolytes with Li metal anodes show discharge capacities exceeding 100 mAh g −1 and better cycling performance compared to batteries using the original Li 10 GeP 2 S 12 . The partial substitution of oxygen for sulfur in Li 10 GeP 2 S 12 affords a novel solid electrolyte, Li 10 GeP 2 S 12− x O x , with high conductive properties and electrochemical stability.

In order to elucidate the magnetism and Li diffusion in LiFePO4, we have measured muon-spin rotation and relaxation (μ+SR) spectra for a polycrystalline LiFePO4 sample in the temperature range between 1.8 and 500K. Below TN ∼ 52K, two oscillatory signals together with onefast relaxation signal were clearly found in the zero-field (ZF) μ+SR spectrum. The three signals are reasonably explained using an antiferromagnetic (AF) spin structure proposedby neutron measurements, because electrostatic potential calculations suggests multiple different muon sites in the LiFePO4 lattice. However, the AF ordered moment estimated from μ+SR was about 3/4 of that reported by neutron, probably due to a different time window between the two techniques. In the paramagnetic state, ZF-and longitudinal-field (LF-) μ+SR spectraexhibiteda dynamic nuclear field relaxation. From the temperature dependence of the field fluctuation rate, a diffusion coeffcient of Li+ ions (DLi) at300K was estimated about 3.6×10−10 cm2/s, assuming that diffusing Li+ ions jump between the regular site and interstitial sites.

The formation and the evolution of lithium-containing species on the surface of grains of a layered 4 V material such as LiNi 1/2 Mn 1/2 O 2 along the electrochemical cycling have been followed using 7 Li MAS NMR, electrochemical impedance spectroscopy (EIS) and XPS. Materials displaying different specific surface areas and stored in different atmospheres have been investigated in order to study the influence of the surface/volume ratio and the influence of the initial surface state, respectively. It is shown that the presence of an initial interphase of Li 2 CO 3 influences the electrochemical behavior of the electrode, emphasizing the importance of the history of the electrode prior cycling. 7 Li MAS NMR experiments performed upon cycling indicate the formation of interphase species in reduction and their partial removal in oxidation, indicating the dynamic character of the interphase upon cycling. Combined NMR, EIS and XPS experiments show the strong influence of the electrode/electrolyte interphase evolution on the electrochemical performance. Such results lead us to draw conclusions on the optimal storage conditions of layered 4 V materials for Li-ion batteries such as LiNi 1/2 Mn 1/2 O 2 .

New Li-Ti-N solid-solution compounds with an anti-fluorite-type superstructure were synthesized by heating the mixture of Li3N and TiN at 800°C in Ar flow. The compositions of the new compounds seem to lie on the tie-line between the two well-known compounds, Li3N (hexagonal, P6/mmm) and Li5TiN3 (cubic, I21/a-3) by Li evaporation during heating in Ar gas flow, and nominally represented with Li5+yTi1-yN3-y. The solubility is large; the anti-fluorite-type superstructure of Li5TiN3 (y = 0) was retained up to y = ca. 0.9, which is close to the end member Li3N (y = 1) with a different layered structure. This finding opens up further exploring other new Li-M-N (M = transition metals, group XIII, or XIV elements) phases with some attractive functions.

A systematic first-principles calculation based on density functional theory is carried out to discuss the redox mechanism of Li2MnO3. The lattices of structural models having C2/m- and C2/c-type stacking sequences can be regarded as hexagonal, while their symmetry is monoclinic. Different stacking sequences of [Mn2/3Li1/3] layers do not cause differences in the energy or crystallographic structure, suggesting a disordered stacking sequence. A calculation for Li2−xMnO3 assuming topotactic lithium removal indicates that lithium removal can occur at a potential of about 4.6 V with a wide potential plateau. The electronic structure of Li2−xMnO3 shows that the manganese ions remain in the charge state of Mn4+ and the charge of the removed lithium ions is compensated by the oxidation of oxygen.

Layered LiNi1/2Mn1/2O2 compound prepared by the classical coprecipitation method delivers a capacity loss upon cycling in a lithium battery, which increases upon the 5 first cycles, and then becomes less visible over the next 40 cycles. The charge–discharge polarization follows the same trend. The formation and the evolution of lithium-containing species on the grain surface of layered LiNi1/2Mn1/2O2 and the interfacial charge transfer resistance have been carefully investigated upon cycling, by coupling ex situ 7Li MAS NMR and in situ electrochemical impedance spectroscopy. An important increase in the amount of lithiated surface species is observed during the first electrochemical cycles along with an increase of the charge transfer resistance. After reaching a maximum, both integrated intensity of the NMR signal and charge transfer resistance decrease, indicating a strong correlation between these two different surface characteristics, obtained from ex situ and in situ experiments, respectively. The evolution of surface species, probed by NMR and impedance spectroscopy, follow the same kind of variation as electrochemical parameters, demonstrating a unique control by surface phenomena of the overall electrochemical behavior of an electrode material of lithium battery. Keywords: Lithium batteries, NMR, Interfaces, Positive electrode, Impedance spectroscopy

TEM observation and electron diffraction analysis of a laser ablation perovskite film was carried out. The film was deposited on a single-crystal substrate and showed epitaxial growth normal to the substrate. The crystal orientation of the perovskite film varies depending on the kind of single-crystal substrate. The surface structure of the atomic arrangement was investigated based on an analysis of electron diffraction patterns. Its relation to the kinetics of the reduction of molecular oxygen is discussed., ドライプロセスによる高速イオン移動界面の構築と高出力電極への展開

In order to investigate the microscopic magnetic nature of a sodium phospho- olivine, we have measured μ+SR spectra for NaxFePO4 using a powder sample in the temperature range between 2 and 500 K. ZF-μ+ SR measurements below 200 K at TRIUMF showed the appearance of static magnetic order below TN ~ 61 K, where the susceptibility-vs.- temperature curve exhibits a sharp maximum due to an antiferromagnetic (AF) transition. The wide distribution found for the internal magnetic field (Hint) was explained by the formation of AF order with the spread in Hint due to random distribution of Na vacancies. At higher temperatures, the ZF-spectrum for Na0.7FePO4, obtained at J-PARC, is found to change from a low-T static behavior to a high-T dynamic behavior above ~ 300 K. This is consistent with the fact that Na+ ions are reversibly extracted from and intercalated into the NaxFePO4 lattice, while there is no NMR study on Na-diffusion in NaxFePO4 due to large Fe moments.

The electrode surface of a lithium battery was characterized using in situ reflectivity techniques and epitaxial thin films. Epitaxial LiFePO4 thin films were fabricated by pulsed laser deposition. Changes in interfacial structures on the surface are determined by X-ray and neutron reflectivity (NR) measurements using an X-ray-transmission electrochemical cell. The LiFePO4 surface is stable during the first charge/discharge process. NR analysis indicates a reversible change in the concentration gradient of lithium ions at the LiFePO4/electrolyte interface on lithium deintercalation.

International audience; The changes appearing for LiFePO"4-C nano-composites exposed to atmosphere at 120^oC have been structurally and chemically examined by the use of TGA, XRD, XPS, Mossbauer, ^7Li MAS NMR and electrochemical methods. The results conclude that a highly disordered phase resulting from the aging of LiFePO"4 appears on the surface of the grains of the material, is assigned to a phosphate phase and can insert lithium around 2.6V with poor reversibility. The essential role of water has been investigated and clearly demonstrated. Thus, the aging mechanism occurring in hot humid air is completely different from a simple oxidation as well as from the aging process observed above 150^oC and involves the incorporation of hydroxyl groups. In addition, Fe"2O"3 formation has not been observed for such an aging in mild conditions.

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The impact of air exposure on LiFePO4–C nanocomposites has been investigated at moderate temperature. We show here that the storage in 120 °C hot air for 30 days leads not only to the material delithiation but also to the formation of an amorphous ferric phosphate side-phase, accounting for 38% of the total iron. The formed phase is found to be partially hydrated, suggesting a water-driven aging mechanism and a proposed hypothetic formula: LixFePO4(OH)x. The side-phase displays new electrochemical activity but poor cyclability and the overall battery performance is thus deteriorated. The regeneration of pristine structure, together with the performance recovery can be achieved by a simple thermal treatment under inert atmosphere. Keywords: Li-ion, Cathode, LiFePO4, Aging, Moisture

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A series of LiMnyFe1−yPO4 samples have been prepared in the whole range 0 ≤ y ≤ 1. Chemical delithiation could be achieved to obtain MnyFe1−yPO4 in the range 0 ≤ y ≤ 0.8, keeping the same crystal phase (olivine structure, space group Pnma). The composition y = 0.8 is the limit where the delithiated phase is still crystallized, but abruptly suffers strains at the molecular scale evidenced by both optical spectroscopy and X-ray diffraction. The analysis of the magnetic properties shows that in all the samples the concentration of impurities is negligible. The concentration of polarons, either holes associated to Li vacancies in LiMnyFe1−yPO4 or electrons associated to the existence of Li left in the matrix of MnyFe1−yPO4, is found to be small (≤1%) in all the samples. For y ≤ 0.6, all the Mn3+ ions MnyFe1−yPO4 are in the high-spin state (S = 2). At larger manganese concentration, however, the Mn3+ ions in excess of the critical concentration yc = 0.6 undergo a transition to the low-spin state (S = 1). As a consequence, and in contrast with prior works, we find that Mn0.8Fe0.2PO4 has magnetic interactions that are much smaller, and no antiferromagnetic ordering in this compound is detected, at least above 20 K. Antiferromagnetic ordering that had been reported so far for MnyFe1−yPO4 at large y-composition might come from incomplete delithiation. The spin-transition of Mn3+ in concentration (y–yc) to the low-spin state is at the origin of the strain fields at the molecular scale that increase with y for y > 0.6, and ultimately prevents the full delithiation for y > 0.8. This result sheds light on the reason for the degradation of cathode properties in Mn-rich compounds of the heterosite–purpurite series, while the electrochemical properties are good in the range y ≤ 0.6 but only at slow rates, due to the very small hopping mobility of the small polaron.

International audience; Li-7 MAS NMR, usually a bulk characterization technique, is used here to analyze the positive electrode/electrolyte interphase. The sharpening of the NMR spectra line shape as the amount of surface species increases shows that the observed signal is clearly the sum of signals due to the distribution of lithium ions in the interphase in terms of distance from the bulk of electrode active material. This technique is then used to compare characteristics of the interphase coming from the contact with LiPF6-based electrolyte in the case of storage or electrochemical cycling. A clear influence of the change of potential on the interphase configuration and in particular on its intimacy with the bulk of active material is deduced from the change in NMR spectra lineshape. This information is hardly obtained by other characterization technique, making NMR a powerful tool for the study of interphases and passivation layers in lithium batteries materials.

The magnetic properties of the olivine-type compounds LiMPO 4 (M = Mn, Co, Ni) are probed using muon spin rotation/relaxation ( μ SR). These materials pose an appealing magnetic structure and a high -potential technological interest as cathode materials for future rechargeable Li-ion batteries. The LiMPO 4 family of compounds consists of a corner-sharing MO6 octahedra of high-spin M 2+ ions manifesting an antiferromagnetic ground state below TN ≈ 30 K. Additionally, these compounds belong to a class of materials exhibiting properties between two-and three dimensional systems. A comparative study between the family members is presented.