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Fluoride-ion conducting solid materials are applicable as solid electrolytes for sensing devices and next generation rechargeable batteries. Most of the previously reported materials have limited to the single-anion compounds such as fluorite-type, tysonite-type, and perovskite-type structures. These are suffered from further improvements by crystal structure modification which derives a paradigm shift in the material tailoring. Fluoride and sulfide ions prefer respective coordination environments because of the different ionic radii and electronegativity. This feature implies that fluorosulfide mixed-anion compounds have potential to form anion-ordering crystal structures with new fluoride-ion conducting layers. Herein, we have found that the fluorosulfide La2+xSr1−xF4+xS2 exhibits fluoride ion conduction. The presence of multiple anions results in the formation of anion-ordering two-dimensional crystal lattice with triple fluorite layers, which cannot be realized for metal fluorides. Sulfide ions in the crystal structure increases the number of interstitial sites of fluoride ions, forming fluoride ion conduction pathway.

Amorphous transition-metal polysulfides are promising positive electrode materials for next-generation rechargeable lithium-ion batteries because of their high theoretical capacities. In this study, sulfur anion redox during lithiation of amorphous TiS₄ (a-TiS₄) was investigated by using experimental and theoretical methods. It was found that a-TiS₄ has a variety of sulfur valence states such as S²⁻, S⁻, and S[δ−]. The S²⁻ species became the main component in the Li₄TiS₄ composition, indicating that sulfur is a redox-active element up to this composition. The simulated a-TiS₄ structure changed gradually by lithium accommodation to form a-Li₄TiS₄: S–S bonds in the disulfide units and polysulfide chains were broken. Bader charge analysis suggested that the average S valency decreased drastically. Moreover, deep lithiation of a-TiS₄ provided a conversion reaction to metallic Ti and Li₂S, with a high practical capacity of ∼1000 mAh g⁻¹ when a lower cutoff voltage was applied.

An archetypical Li-rich layered oxide, Li2MnO3, shows a large initial charge capacity of ~350 mAh g-1 with little oxidation of the constituent Mn ions, yet, the crystal structure of delithiated Li2MnO3 is still unclarified because the structural disorder induced by the considerable Li extraction makes the analysis challenging. X-ray pair distribution function (PDF) analysis is a powerful tool to experimentally elucidate the structure of the disordered phase. Here, we conducted a comprehensive analysis with a focus on PDF analysis in combination with the X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to reveal the disordered crystalline structure of the electrochemically delithiated Li2MnO3. The XRPD and TEM analyses clarified the formation of a low-crystallinity phase in the light of the average structure. The XAS and PDF analyses further revealed that the MnO6–based framework was rearranged with maintaining the MnO6 octahedral coordination after the initial charge. The difference pair distribution function (d-PDF) technique was therefore employed to extract the structural information of the low-crystallinity disordered phase. The delithiated phase was found to have a structure similar to the cubic spinel, LiMn2O4, rather than that of delithiated LiMn2O4 (λ-MnO2). In addition, the middle-range order of the delithiated phase deteriorated after the charge, indicating a decrease of coherent domain size to a single nm order. The composite structure formed after the first charge, therefore, consists of the disordered cubic spinel structure and unreacted Li2MnO3. The formation of the composite structure “activates” the electrode material structurally and eventually induces characteristic large capacity of this material.

Lithium- and manganese-rich layered oxides (LMRs) are promising positive electrode materials for next-generation rechargeable lithium-ion batteries. Herein, the structural evolution of Li1.2Ni0.2Mn0.6O2 during the initial charge–discharge cycle was examined using synchrotron-radiation X-ray diffraction, X-ray absorption spectroscopy, and nuclear magnetic resonance spectroscopy to elucidate the unique delithiation behavior. The pristine material contained a composite layered structure composed of Ni-free and Ni-doped Li2MnO3 and LiMO2 (M = Ni, Mn) nanoscale domains, and Li ions were sequentially and inhomogeneously extracted from the composite structure. Delithiation from the LiMO2 domain was observed in the potential slope region associated with the Ni2+/Ni4+ redox couple. Li ions were then extracted from the Li2MnO3 domain during the potential plateau and remained mostly in the Ni-doped Li2MnO3 domain at 4.8 V. In addition, structural transformation into a spinel-like phase was partly observed, which is associated with oxygen loss and cation migration within the Li2MnO3 domain. During Li intercalation, cation remigration and mixing resulted in a domainless layered structure with a chemical composition similar to that of LiNi0.25Mn0.75O2. After the structural activation, the Li ions were reversibly extracted from the newly formed domainless structure.

The charge/discharge reaction mechanisms of graphite negative electrodes in Li ion batteries were investigated via operando synchrotron X-ray diffraction at 0 °C and 25 °C. The intercalation of Li ions at 25 °C formed the stage 1 compound with an in-plane structure of LiC6; while intercalation at 0 °C only formed stage 2, with in-plane structures of LiC9 and LiC6. The degree of graphite expansion in the a, b-axes and c-axis directions by intercalation at 0 °C was less than that at 25 °C. Hence, it was difficult to form the stage 1 structure by further increases in the Li ion concentration, and the charging reaction at low temperature became difficult. De-intercalation at 0 °C did not follow the Daumas–Hérold model and proceeded discretely in the order: stage 1 → stage 2 → stage 4 → graphite, without going through stages 3, 5–8 and dilute stage 1.

Since the rechargeable Li-ion battery was invented in the early 1990s, its performance has evolved continually and Li-ion batteries are now installed in most mobile devices. In these batteries, graphite is used as a negative electrode material. However, the detailed reaction mechanism between graphite and Li remains unclear. Here we apply synchrotron X-ray diffraction, 7Li-nuclear magnetic resonance and Raman spectroscopy to operando analysis of the charge/discharge mechanism of a graphite electrode. The spectrum of the graphite electrode is measured repeatedly during the reaction. The operando dataset obtained is then analyzed synchronously with the composition of x in LiCx estimated from the charge/discharge curves. We propose a synchronized operando analysis method that provides useful information about the behavior of the C–C bond vibration mode and the interactions between Li and carbon atoms due to structural change during the charge/discharge reaction. In addition, we determine details of the intercalation mechanism.

A high anionic conductivity of ∼3.5 × 10–3 S cm–1 at room temperature is achieved for PbxSn2–xF4 (x = 1.21) obtained by annealing a mechanically milled PbF2/SnF2 mixture at 400 °C. The observed syn...

Vanadium sulfide (VS4) is one of the promising positive electrode materials for next-generation rechargeable lithium-ion batteries because of its high theoretical capacity (1196 mA h g−1). Crystalline VS4 has a unique structure, in which the Peierls-distorted one-dimensional chains of V–V bonds along the c axis are loosely connected to each other through van der Waals interactions. In this study, an amorphous VS4 is prepared by mechanical milling of the crystalline material, and its lithiation/delithiation behavior is investigated by solid-state nuclear magnetic resonance (NMR) spectroscopy. The amorphous VS4 shows a chain structure similar to that of crystalline VS4. The amorphous host structure is found to change drastically during the lithiation process to form Li3VS4: the V ions become tetrahedrally coordinated by S ions, in which the valence states of V and S ions simultaneously change from V4+ to V5+ and S− to S2−, respectively. When the Li insertion proceeds further, the valence state of V ions is reduced. After the 1st cycle, the amorphous VS4 recovers to the chain-like structure although it is highly disordered. No conversion to elemental V is observed, and a high capacity of 700 mA h g−1 is reversibly delivered between 1.5 and 2.6 V.

Intensive research is underway to further enhance the performance of lithium-ion batteries (LIBs). To increase the capacity of positive electrode materials, Li-rich layered oxides (LLO) are attracting attention but have not yet been put to practical use. The structural mechanisms through which LLO materials exhibit higher capacity than conventional materials remain unclear because their disordered phases make it difficult to obtain structural information by conventional analysis. The X-ray total scattering analysis reveals a disordered structure consisting of metal ions in octahedral and tetrahedral sites of Li layers as a result of cation mixing after the extraction of Li ions. Metal ions in octahedral sites act as rigid pillars. The metal ions move to the tetrahedral site of the Li layer, which functions as a Li-layer pillar during Li extraction, and returns to the metal site during Li insertion, facilitating Li diffusion as an adaptive pillar. Adaptive pillars are the specific structural features that differ from those of the conventional layered materials, and their effects are responsible for the high capacity of LLO materials. An essential understanding of the pillar effects will contribute to design guidelines for intercalation-type positive electrodes for next-generation LIBs.

The graphite negative electrode for Li-ion batteries was subjected to precision charge/discharge measurements at low current loads. The derivatives of the potential vs capacity curve and the potential vs C/Li composition curve were used to analyze elementary charge/discharge reactions. The number of peaks in the potential-capacity derivative curve increased with decreasing current load, and the elementary reactions, based on the formation of an unconfirmed superlattice structure, could be clearly separated and analyzed. By synchronizing these results with operando synchrotron X-ray diffraction data, a phase diagram of the Li-graphite intercalation compound formed by the charge/discharge reaction in Li-ion battery was established.

Since the commercialization of rechargeable Li ion batteries in the early 1990 s, the performance of these devices has continually improved. In such batteries, graphite is typically used as the negative electrode and the present work examined the reaction mechanisms at graphite negative electrodes based on operando synchrotron X-ray diffraction analyses during charge/discharge. The resulting in-plane diffraction patterns of the Li-intercalated graphite permitted a detailed analysis of changes in the three-dimensional structure of the electrode. As the intercalation proceeded from a dilute stage 1 (with less Li intercalation) to a final stage 1 (the formation of LiC6), the material transitioned from a random in-plane structure to a p(√3 × √3)R30° in-plane structure via a superlattice based on a p(3 × 3)R0° in-plane structure. The data also indicate that a series of superlattices was formed during the reaction of the electrode as a result of successive rearrangements, depending on the amount of Li intercalated into the graphite.

Lithium sulfide (Li2S) is one of the promising positive electrode materials for next-generation rechargeable lithium batteries. To improve the electrochemical performance of electronically resistive Li2S, a Fe-doped Li2S-based positive electrode material (Li8FeS5) has been recently designed and found to exhibit excellent discharge capacity close to 800 mAh g−1. In the present study, we investigate the structural and dynamic behavior of Li8FeS5 during charge–discharge cycling. In Li8FeS5, Fe ions are incorporated into the Li2S framework structure. The Li2S-based structure is found to transform to an amorphous phase during the charge process. The delithiation-induced amorphization is associated with the formation of S-S polysulfide bonds, indicating charge compensation by S ions. The crystalline to non-crystalline structural transformation is reversible, but Li ions are extracted from the material via a two-phase reaction, although they are inserted via a single-phase process. These results indicate that the delithiation/lithiation mechanism is neither a topotactic extraction/insertion nor a conversion-type reaction. Moreover, the activation energies for Li ion diffusion in the pristine, delithiated, and lithiated materials are estimated to be in the 0.30–0.37 eV range, which corresponds to the energy barriers for local hopping of Li ions along the Li sublattice in the Li2S framework.

Li2MnO3 is an important parent component in lithium- and manganese-rich layered oxides (LMRs), which are one of the promising positive electrode materials for next-generation lithium ion rechargeable batteries. Here, we report the layered-to-spinel phase transformation in Li2MnO3 during the initial charging process to characterise its unique delithiation behaviour, which gives an insight into the relationship between the structure, superior capacities and degradation of LMR electrodes. The atomic-scale observation using scanning transmission electron microscopy (STEM) techniques suggests that the structural transformation occurs in a biphasic manner within a single particle. The formed phase has a Li-defect spinel structure, indicating that the delithiation leads to Mn migration from the transition-metal layer to the Li layer, accompanied by some oxygen release. This layered-to-spinel phase transformation is an essential bulk process in the initial activation of Li2MnO3. During the lithiation in the 1st discharge, the Mn remigration occurs and the layered structure is again formed with significant disordering. During the multiple cycles, the defect spinel structure is stabilised and becomes more oxygen-deficient with a lower Mn valency. As a consequence, the amount of inserted Li decreases, which corresponds to the capacity and voltage fading observed in Li2MnO3 and LMRs.

Lithium- and manganese-rich layered oxides (LMRs) are promising positive electrode materials for next-generation rechargeable lithium-ion batteries. Herein, the structural evolution of Li1.2Ni0.2Mn0.6O2 during the initial charge–discharge cycle was examined using synchrotron-radiation X-ray diffraction, X-ray absorption spectroscopy, and nuclear magnetic resonance spectroscopy to elucidate the unique delithiation behavior. The pristine material contained a composite layered structure composed of Ni-free and Ni-doped Li2MnO3 and LiMO2 (M = Ni, Mn) nanoscale domains, and Li ions were sequentially and inhomogeneously extracted from the composite structure. Delithiation from the LiMO2 domain was observed in the potential slope region associated with the Ni2+/Ni4+ redox couple. Li ions were then extracted from the Li2MnO3 domain during the potential plateau and remained mostly in the Ni-doped Li2MnO3 domain at 4.8 V. In addition, structural transformation into a spinel-like phase was partly observed, which is associated with oxygen loss and cation migration within the Li2MnO3 domain. During Li intercalation, cation remigration and mixing resulted in a domainless layered structure with a chemical composition similar to that of LiNi0.25Mn0.75O2. After the structural activation, the Li ions were reversibly extracted from the newly formed domainless structure.

Vanadium sulfide (VS

Li-rich layered oxides have attracted attention as promising positive electrode materials for next-generation lithium-ion secondary batteries because of their high energy storage capacity. The participation of the oxygen anion has been hypothesized to contribute to these oxides' high capacity. In the present study, we used O K-edge and Mn L-edge X-ray absorption spectroscopy (XAS) to study the reversible redox reactions that occur in single-phase Li-rich layered manganese oxide, Li2MnO3. We semiquantitatively analyzed the oxygen and manganese reactions by dividing the charge/discharge voltage region into two parts. The O K-edge XAS indicated that the electrons at the oxygen site reversibly contributed to the charge compensation throughout the charge/discharge processes at operating voltages between 2.0 and 4.8 V vs. Li+/Li0. The Mn L-edge XAS spectra indicated that the Mn redox reaction occurred only in the lower-voltage region. Thus, at higher potentials, the electrons, mainly at the oxygen site, contributed to the charge compensation. Peaks whose energies were similar to peroxide appeared in and then disappeared from the O K-edge spectra obtained during the reversible redox cycles. These results indicate that the reorganization of the oxygen network in the crystal structure affects the redox components. By using two kinds of detection modes with different probing depths in XAS measurements, it was found that these redox reactions are bulk phenomena in the electrode.

The oxidation/reduction behaviours of lattice oxygen and transition metals in a Li-rich manganese-based layered oxide Li[Li0.25Ni0.20Mn0.55]O1.93 are investigated by using hard X-ray photoelectron spectroscopy (HAX-PES). By making use of its deeper probing depth rather than in-house XPS analyses, we clearly confirm the formation of O- ions as bulk oxygen species in the active material. They are formed on the 1st charging process as a charge compensation mechanism for delithiation and decrease on discharging. In particular, the cation-anion dual charge compensation involving Ni and O ions is suggested during the voltage slope region of the charging process. The Ni ions in the material are considered to increase the capacity delivered by a reversible anion redox reaction with the suppression of O2 gas release. On the other hand, we found structural deterioration in the cycled material. The O- species are still observed but are electrochemically inactive during the 5th charge-discharge cycle. Also, the oxidation state of Ni ions is divalent and inactive, although that of Mn ions changes reversibly. We believe that this is associated with the structural rearrangement occurring after the activation process during the 1st charging, leading to the formation of spinel- or rocksalt-like domains over the sub-surface region of the particles.

An archetypical Li-rich layered oxide, Li2MnO3, shows a large initial charge capacity of ~350 mAh g-1 with little oxidation of the constituent Mn ions, yet, the crystal structure of delithiated Li2MnO3 is still unclarified because the structural disorder induced by the considerable Li extraction makes the analysis challenging. We have performed X-ray pair distribution function (PDF) analysis in combination with the X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS) to reveal the disordered crystalline structure of the electrochemically delithiated Li2MnO3. The XRPD and TEM analyses clarified the formation of a low-crystallinity phase in the light of the average structure. The XAS and PDF analyses revealed that the MnO6–based framework was rearranged with maintaining the MnO6 octahedral coordination after the initial charge. The difference pair distribution function (d-PDF) technique was therefore employed to extract the structural information of the low-crystallinity disordered phase. The delithiated phase was found to have a structure similar to the cubic spinel, LiMn2O4, rather than that of delithiated LiMn2O4 (l-MnO2). In addition, the middle-range order of the delithiated phase deteriorated after the charge, indicating a decrease of coherent domain size to a single nm order. The composite structure formed after the first charge, therefore, consists of the disordered cubic spinel structure and unreacted Li2MnO3. The formation of the composite structure “activates” the electrode material structurally and eventually induces characteristic large capacity of this material.

Vanadium sulfide (VS4) is one of the promising positive electrode materials for high capacity lithium ion secondary batteries. In this study, we prepared an amorphous VS4 (a-VS4) by mechanical treatment of the crystalline VS4 (c-VS4) and characterize its local structure. Furthermore, its lithium insertion/extraction behavior was investigated using solid-state nuclear magnetic resonance (NMR), X-ray pair distribution function (PDF), and Raman spectroscopy analyses. Crystalline VS4 was synthesized from V2S3 (99%, Kojundo Chemical Lab.) and S (99.9%, Wako).1 The mixture was heated in a sealed glass tube under vacuum at 400 °C for 12 h. Then, the amorphous VS4 was prepared from the crystalline sample by mechanical milling for 40 h at 270 rpm. A working electrode was prepared from a mixture of the active material (a-VS4), conductive carbon, and Teflon binder in a weight ratio of 59:29:12. Coin-type or laminate-type cells were assembled in an Ar-filled glove box. The cells were cycled between 1.5 and 2.6 V at a constant current density of 59.8 mA g–1 using a TOSCAT-3100 battery-testing system (Toyo System). They were then carefully disassembled at selected discharge/charge states in the glove box and rinsed with dimethyl carbonate (DMC) to remove the residual electrolyte solution. Local structures of c-VS4 and a-VS4 were characterized and the structural changes of the electrode samples were examined by NMR spectroscopy, X-ray PDF analyses, and Raman spectroscopy. Operando 7Li NMR measurements were performed to study the Li insertion/extraction process under electrochemical operation.2 It is known that c-VS4 has a unique structure, in which the Peierls-distorted one-dimensional chains of V-V bonds along the c axis are loosely connected to each other through van der Waals interactions. We confirmed that a-VS4 shows a chain structure similar to that of c-VS4. The chain structure is found to change drastically during the Li insertion process to form amorphous Li3VS4, where the V ions become tetrahedrally coordinated by S ions. The valence states of V and S ions simultaneously change from V4+ and S– (a-VS4) to V5+ and S2– (a-Li3VS4), respectively. When the Li insertion proceeds further (i.e., a-Li3+d VS4), the valence state of V ion is reduced, and a broad 7Li NMR peak shifts to higher frequencies (Fig. 1). After the 1st cycle, the amorphous VS4 recovers the chain-like structure although it is highly disordered. It is also found that the conversion reaction to metallic V and Li2S are observed when the cell is discharged to 0.2 V. This study indicates that the Li insertion/extraction process of the amorphous sulfur-rich transition metal (TM) sulfides such as a-VS4 and a-TiS4 3 involves the amorphous-amorphous phase transformation, which is related to the changes in the bonding nature of sulfide species and the coordination number of TM ions. The amorphous host structure can accommodate these modifications, which is clearly different from the Li insertion/extraction mechanism in crystalline electrode materials. This work is based on results obtained from a project, “Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2)”, JPNP16001, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References Koganei et al., Solid State Ionics, 323, 32-36 (2018). Shimoda et al., RSC adv. 9, 23979-23985 (2019). Sakuda et al., J. Am. Chem. Soc., 139, 8796-8799 (2017). Figure 1

Introduction : In order to promote development of electric vehicle, it is required to improve the capacity density, the low-temperature performance, and the high-rate property of the batteries. Understanding the lithium intercalation and de-intercalation mechanism at graphite electrode of the storage battery (LIB) is very important for this purpose. Crystal structure changes of lithium-intercalated graphite during charge and discharge processes were investigated by operando X-ray diffraction (XRD) measurements using a synchrotron radiation facility. Low-temperature operando XRD measurements were now available by the development of a new temperature-controlled cell jacket.1-2 This study confirmed in-plane structure change along a- and b-axis as well as stage structure change along c-axis.3 As a result, it was elucidated that crystallinity of graphitic carbon caused differences in phase transition during discharge and this phenomenon affected low-temperature and high-rate discharge performances. Experimental : Coin cells composed of carbon and NMC electrodes were firstly prepared and subjected to the evaluation of the battery performances from the low-temperature (0℃) to the room temperature. Coin cells of several graphitic carbon were evaluated. Crystal structures of lithium-intercalated graphite during discharge process were investigated by operando analysis using synchrotron radiation X-ray diffraction (SR-XRD) at BL28XU beam line of SPring-8. Al-laminated half-cells composed of graphitic carbon and Li electrodes were prepared and subjected to the analysis of operando measurement. The graphitic carbons of different crystallite sizes were analysed. Al-laminated half-cells conditioned by several cycles were used for the measurement. Operando XRD measurements were carried out during charge and discharge processes. X-ray of 25keV (its wavelength of 0.0496 nm) with a beam size of 0.2 mm ×0.5 mm was used to obtain diffraction patterns. The exposure time was set to 10 s. The diffraction patterns were obtained by two-dimensional detector, PILATUS 100K (DECTRIS). Two-dimensional image data were converted to one-dimensional 2q profiles, and the diffraction peaks were separated using the Lorentz functions. The test cell underwent an aging treatment was charged (Li insertion) at room temperature. Thereafter, structural transition were analyzed during the discharging process (Li de-intercalation) in 0.2C at room temperature and in 0.1C at 0℃. Results and Discussion : Figure 1 shows the SR-XRD patterns of lithium-intercalated graphite at the discharge process with current density of 0.2C at room temperature. The result showed the in-plane structure change along a- and b-axis as well as stage structure change along c-axis. The detailed analysis of in-plane structure change and stage structure change for each graphitic carbon was performed using the operando measurements. It was identified that the crystallinity of graphitic carbon caused differences in phase transition during discharge. These results showed that crystallite sizes influence the phase transition and give major effect on LIB performances of graphite negative electrode at low-temperature or high-rate discharge. The Li diffusivity in the graphitic carbon is likely dependent on the crystallite size. The battery reaction mechanism influenced by crystallite size was elucidated by operando XRD measurements. The present results confirm that the crystallinity of the graphitic carbon affects the low-temperature and high-rate discharge characteristics. The detail results will be shown in the conference. Acknowledgment: This work was supported by the Research and Development Initiative for Scientific Innovation of New Generation Battery 2 (RISING2) project administrated by the New Energy and Industrial Technology Development Organization (NEDO). References: S. Takagi et al., “Operando Structure Analysis of Graphite Electrode by Synchrotron Radiation Diffraction” The 59th Battery Symposium, 2E14 (2018). S. Takagi et al., “Operando Structure Analysis of Graphite Electrode by Synchrotron Radiation Diffraction” The 60th Battery Symposium, 1B20 (2019). H. Fujimoto et al., “Operando analysis of charge/discharge reaction mechanism of graphite anode of Li ion battery using synchrotron radiation diffraction, Second report”, The 59th Battery Symposium, 2E16 (2018). Figure 1

Introduction The rechargeable Li-ion battery (LIB) is a successful energy storage device because of its high energy density and long cycle life. In order to improve its performance, quantitative understanding of elementary reactions in the LIB such as the reaction of Li intercalation from electrolyte solution into graphite and crystal structure change in graphite during the reaction must be a great help. Structure change of Li-intercalated graphite during the charge/discharge processes was recently observed by operando X-ray diffraction measurements using a synchrotron radiation at SPring-8.1 The operando XRD data at LiC18 charge/discharge state exhibited two peaks corresponding two different C-C grid distances in the same plane of graphite, while no change in interlayer distance was detected during the appearance and disappearance of these peaks; it implies only in-plane structure transition such as Li/6C layer to Li/9C layer changes.1 An AA to AB stack transition in graphite was characterized by (101) peak disappearance in the XRD data at the composition between LiC63–LiC72.2 To interpret and discuss these experimental results, we conduct first-principles calculations for the phase stability of graphite. Methods and Models The formation enthalpy ∆H f of Li-intercalated graphite is defined as ∆H f (Li n C m ) = ( E DFT(Li n C m ) − nE DFT(Li) − mE DFT(C) ) / (m+n) (1), where E DFT are the total energies of Li-intercalated graphite Li n C m , simple metal Li, and AB stacked graphite C from density functional theory (DFT) calculations. Formation enthalpy as a function of C-ratio, x C = m / (m + n) (2), was used to investigate the phase stability of Li n C m . Quantum ESPRESSO with a plane-wave basis3 and van der Waals functional4 was used to obtain DFT energies. Our previous study using this functional well reproduced the experimental lattice constants and electromotive forces (EMFs) of Li-intercalated graphite.5 It is known that Li-intercalated graphite exhibits stages from 1 to 8. These stages may take different combination of in-plane configurations and interlayer configurations. In-plane configurations considered are Li/6C, Li/9C, Li/18C, and Li/24C, which means the ratios of Li/C atoms are located on a single layer as shown in Fig. 1 (a). Three interlayer structures are considered here; (1) graphite layers stacked with AA overlap, (2) with AB, and (3) mixed (Li including layers are AA stacked, the other layers are AB stacked). Conventional LiC6 intercalated phase corresponds to the stage 1 of Li/6C AA stack structure (denoted as s1-Li/6C-AA, here s1, s2, s3, ... represents stage 1, stage 2, stage 3, ..., respectively). Results The calculated formation enthalpies ∆H f are plotted as a function of x C in Fig. 1 (b). At the composition of LiC6 (x C = 0.857), LiC12 (x C = 0.923), and C (x C = 1), respective most stable phases are s1-Li/6C-AA, s2-Li/6C-AA, and AB stack graphite ones as we could expect. At the composition of LiC18 (x C = 0.947), s2-Li/9C-AA structure is more stable than the s3-Li/6C-AA structure, which is consistent with the experimental observation.1 AB stack structures are more stable than AA at x C > 0.97 from the theoretical calculation, while the AA-AB transition has been observed at 0.984 < x C < 0.986 by experiments. At higher stages (x C > 0.94), mixed stack structure is predicted to be more stable than simple AA and AB structures. The formation enthalpies of s2-Li/9C-mixed and s3-Li/6C-mixed are almost the same (within 0.01 meV/atom) and these configurations are predicted to be the most stable at LiC18. However, these mixed stackings have not been detected by experiments. In the presentation, we will also present the theoretical EMF values of the Li-intercalated graphite electrode and compare them with experimental results. Acknowledgments This work was supported in part by the Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 Project (RISING2) administrated by the New Energy and Industrial Technology Development Organization (NEDO). References S. Takagi, K. Shimoda, H. Fujimoto, H. Kiuchi, T. Naka, T. Murata, K.-I. Okazaki, T. Fukunaga, E. Matsubara, Z. Ogumi, and T. Abe, “Operando Structure Analysis of Graphite Electrode by Synchrotron Radiation Diffraction” The 60th Battery Symposium, 1B20 (2019). H. Fujimoto , S. Takagi , H. Kiuchi , K. Shimoda , K.-I. Okazaki, T. Murata , T. Abe, Z. Ogumi, and E. Matsubara, “Operando analysis of charge/discharge reaction mechanism of graphite anode of Li ion battery using synchrotron radiation diffraction, Second report”, The 59th Battery Symposium, 2E16 (2018). P. Giannozzi et al., J. Phys.: Condens. Matter 21, 395502 (2009); ibid. 29, 465901 (2017). I. Hamada, Phys. Rev. B 89, 121103(R) (2014). J. Haruyama, T. Ikeshoji, and M. Otani, J. Chem. Phys. C 122, 9804 (2018). Figure 1

FeF3 has attracted considerable attention as a positive electrode material for next-generation rechargeable lithium ion batteries, because of its low cost, low risk, and high energy density, which facilitate a conversion-type lithiation/delithiation reaction. However, the conversion reaction of the FeF3 electrode is known to suffer from capacity fading during repeated discharge–charge cycles. Herein, we find an interesting correlation between capacity fading behavior and spectral evolutions in electrochemical operando nuclear magnetic resonance (NMR) measurements. The operando 7Li NMR spectra demonstrate the reversible formation of metallic Fe by the conversion process during the early discharge–charge cycles. However, it is gradually suppressed after repeated cycles. Moreover, LiF is augmented at the fully charged states, indicating that FeF3 is no longer recovered after repeated cycles. The active material can converge into FeF2 and LiF in the degraded electrode. Another factor associated with capacity degradation is the electrolyte decomposition occurring at high voltages, which results in a resistive film coating the electrode surface. We therefore conclude that the film accumulation on repeated discharging inhibits the conversion reaction to metallic Fe and LiF, leading to a characteristic capacity fading behavior of FeF3.

1.Introduction In recent years, the development of innovative batteries that exceed the performance of lithium-ion batteries has been desired. One of the candidates is a fluoride shuttle battery (FSB). It is an anion-based, rechargeable batteries operating under fluoride shuttling, and rests upon the foundation of a redox-active fluoride ion transporting electrolyte of high electrochemical stability. To realize the FSB, we have developed a lactone-based Li+/F- hybrid electrolyte, in which Li+ and F- ions that normally cannot coexist in organic solvents form some complexes soluble in GBL. The thus reformed electrolyte, together with its delicate and unique anion accepting (AA) function, largely expands the negative potential window to or beyond the standard redox potential of Li+/Li. In this study, in order to clarify the electrochemical behaviors of BiF3/Bi electrode combined with the electrolyte, the operando analysis was carried out by the synchrotron radiation diffraction (SRD) measurement. 2. Experimental The BiF3 powder mixed with acetylene-black and PVdF was used as the working electrode. The activated carbon and Ag metal were used as the counter and reference electrodes, respectively. The Al-laminated half-cell composed of above-mentioned electrodes was assembled using a newly developed hybridized electrolyte. Thus prepared cell was pre-discharged (0th cycle) in advance in the potential range of -1.5 V – 1.0 V at ca. 0.04C. Then, several charge/discharge cycles were repeated with the same conditions. SRD was measured with BL28XU beam line at Super Photon ring-8, Japan during the whole charge/discharge process. High-energy X-ray with a wavelength of 0.049592 nm was used to obtain 2D diffraction patterns. The exposure time was set to 10 s, and several thousand diffraction profiles were obtained during the discharge/charge process. In order to analyze the obtained enormous profiles data in conjunction with the charge/discharge curves and their differential curves (V-dQ/dV), an analysis software called “Profile Chaser” was newly developed. By using the software, all the profiles of electrode during charge/discharge processes are loaded automatically in the computer. The profiles were successively displayed on a monitor as a series of profiles in conjunction of compositions estimated from the charge/discharge curves, so that the profile change was traced from the monitor. 3. Results and discussions Fig.1 shows the SRD profile changes in the discharge process of 0th and 1st cycles. In both cycles, the intensity of 111 diffraction of BiF3 decreased and that of 012 diffraction of Bi increased as the discharge reaction proceeded. However, the formation of BiF3 was hardly observed in the charge process. It indicates that the bismuth fluoride formed in the charge process is amorphous or solved in the electrolyte. Figure 1

Introduction : In order to promote development of electric vehicle, it is required to improve the capacity density of a battery, the battery performance at a low temperature, and the high rate property of a battery. Characterization of the size distribution and the average size of carbon in the negative electrode significantly influence on the battery performance. We have studied clarification of graphitic carbon’s properties influencing on performance of LIB especially at low temperature. Firstly, the X-ray diffraction profiles of several graphitic carbons were analyzed by the fundamental parameter (FP) method. Further, the structure changes of lithium-intercalated graphite during the charge and discharge processes were investigated by operando measurement using synchrotron radiation at BL28XU of SPring-8 in Japan. The time resolution of the apparatus is the order of milliseconds for analyzing one diffraction pattern. Experimental : Crystallite size and its distribution of several graphitic carbons were analyzed by the fundamental parameter (FP) method using X-ray diffraction profiles. X-ray wavelength of 0.154 nm was used to obtain X-ray diffraction profiles. In order to analyze crystallite size and its distribution, X-ray diffraction profiles were calculated by using software called PDXL2 (Rigaku Corporation). Coin cells composed of carbon and NMC electrodes were prepared and subjected to the evaluation of the battery performances from the low temperature to the room temperature. Coin cells conditioned by several cycles were evaluated. Further, crystal structures of lithium-intercalated graphite during charge and discharge processes were investigated by operando analysis using synchrotron radiation diffraction at BL28XU beam line of SPring-8. Al-laminated half-cells composed of graphitic carbon and Li electrodes were prepared and subjected to the evaluation of operando measurement. The graphitic carbons of different crystallite sizes and their distributions were analysed. Al-laminated half-cells conditioned by several cycles were used for the measurement. Operando measurements were carried out during charge and discharge processes. X-ray of 25keV (its wavelength of 0.0496 nm) with a beam size of 0.2 mm ×0.5 mm was used to obtain diffraction patterns. The exposure time was set from 0.5 s to 10 s. The diffraction patterns were obtained by two-dimensional detector (Rigaku Corporation). Results and Discussion : The experimental X-ray diffraction profile of graphitic carbon and that calculated profile by the fundamental parameter (FP) method were obtained. The calculated profile showed a good fit with the measured one. The each plane of graphitic carbon was analyzed properly. The analysis of FP method revealed that crystallite sizes and their distributions of graphitic carbons influences on LIB performance especially at low temperature. The results indicate that the low temperature characteristics improve as the crystallite size and distribution of the graphite (102) plane decreases. The same results were also obtained for the relationship between the crystallite size distribution of the graphite (102) plane and the high-rate discharge characteristics of LIB. The crystallite size distribution of the graphite (102) plane is thought to express the Li diffusivity. Figure shows the result of synchrotron radiation diffraction pattern of lithium-intercalated graphite at the discharge process with current density of 0.2C. The stage change was analysed clearly as shown in Figure.The difference of stage change of each carbon was revealed in considerable detail by Operando measurement. The crystallite size and its distribution influencing on the battery performance at low temperature was examined in detail. The result showed that crystallite sizes and their distributions influence on the phase structure changes and give major effect on charge and discharge performances of graphite negative electrode at low temperature. Their battery reaction mechanism influenced by crystallite size distribution was elucidated by the Operando measurement. The detail results will be shown in the conference. Acknowledgment: This work was supported by the Research and Development Innovative for Scientific Innovation of New Generation Battery 2 (RISING2) project of the New Energy and Industrial Technology Development Organization (NEDO). Figure 1

Vanadium sulfide (VS4) is one of the promising positive electrode materials for high capacity lithium ion secondary batteries. In this study, we prepared an amorphous VS4 (a-VS4) by mechanical treatment of the crystalline VS4 (c-VS4) and characterize its local structure. Furthermore, its lithium insertion/extraction behavior was investigated using solid-state nuclear magnetic resonance (NMR), X-ray pair distribution function (PDF), and Raman spectroscopy analyses. Crystalline VS4 was synthesized from V2S3 (99%, Kojundo Chemical Lab.) and S (99.9%, Wako).1 The mixture was heated in a sealed glass tube under vacuum at 400 °C for 12 h. Then, the amorphous VS4 was prepared from the crystalline sample by mechanical milling for 40 h at 270 rpm. A working electrode was prepared from a mixture of the active material (a-VS4), conductive carbon, and Teflon binder in a weight ratio of 59:29:12. Coin-type or laminate-type cells were assembled in an Ar-filled glove box. The cells were cycled between 1.5 and 2.6 V at a constant current density of 59.8 mA g–1 using a TOSCAT-3100 battery-testing system (Toyo System). They were then carefully disassembled at selected discharge/charge states in the glove box and rinsed with dimethyl carbonate (DMC) to remove the residual electrolyte solution. Local structures of c-VS4 and a-VS4 were characterized and the structural changes of the electrode samples were examined by NMR spectroscopy, X-ray PDF analyses, and Raman spectroscopy. Operando 7Li NMR measurements were performed to study the Li insertion/extraction process under electrochemical operation.2 It is known that c-VS4 has a unique structure, in which the Peierls-distorted one-dimensional chains of V-V bonds along the c-axis are loosely connected to each other through van der Waals interactions. We confirmed that a-VS4 shows a chain structure similar to that of c-VS4. The chain structure is found to change drastically during the Li insertion process to form amorphous Li3VS4, where the V ions become tetrahedrally coordinated by S ions. The valence states of V and S ions simultaneously change from V4+ and S– (a-VS4) to V5+ and S2– (a-Li3VS4), respectively. When the Li insertion proceeds further (i.e., a-Li3+d VS4), the valence state of V ion is reduced, and a broad 7Li NMR peak shifts to higher frequencies (Fig. 1). After the 1st cycle, the amorphous VS4 recovers the chain-like structure although it is highly disordered. It is also found that the conversion reaction to metallic V and Li2S are observed when the cell is discharged to 0.2 V. This study indicates that the Li insertion/extraction process of the amorphous sulfur-rich transition metal (TM) sulfides such as a-VS4 and a-TiS4 3 involves the amorphous-amorphous phase transformation, which is related to the changes in the bonding nature of sulfide species and the coordination number of TM ions. The amorphous host structure can accommodate these modifications, which is clearly different from the Li insertion/extraction mechanism in crystalline electrode materials. References 1. Koganei et al., Solid State Ionics, 323, 32-36 (2018). 2. Shimoda et al., RSC adv. 9, 23979-23985 (2019). 3. Sakuda et al., J. Am. Chem. Soc., 139, 8796-8799 (2017). Figure 1

Li2TiO3 is a Li-rich cathode/anode material similar to Li2MnO3. These materials crystallize into monoclinic structures with ABC-stacked atomic layers, approximated by pseudo-trigonal cells. In these crystals, transition-metal layers are occupied not only by transition-metal atoms but also by Li atoms, forming ordered/disordered atomic arrangements. Faults Rietveld analysis was conducted, showing that Li2TiO3 crystalizes into a monoclinic structure with the space group C2/c, in which Li and Ti atoms are configured in an imperfectly ordered arrangement at the transition-metal layer and a large number of stacking faults are generated in the crystal. To precisely evaluate the site occupancies in such imperfect crystals, our structural analysis found that the structures should be analyzed by powder diffraction while taking stacking faults and atomic mixing into account. The atomic mixing at the transition-metal layer tends to gradually increase as the synthesis temperature is raised.

An investigation was made on the electronic structure of 4d transition metal layered oxide material of Li2RuO3 using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The intensity of O [Formula: see text] pre-edge peak increased for Li ion extracted samples, suggesting increased ligand holes. The Ru 3d XPS spectrum suggested the variation of local structure around Ru ions by extraction of Li ions. We conclude that the delithiation from Li2RuO3 is charge compensated by O anions, and that the creation of the ligand holes reorganizes electronic structures composed of highly hybridized Ru 4d and O 2p orbitals.

The electrochemically-driven conversion reaction of BiF3 with Li+ ions is of interest for potential application as a positive electrode system in conversion type rechargeable batteries. Here, we use synchrotron radiation diffraction and 7Li nuclear magnetic resonance (NMR) for complementary operando observations of reversible or quasi-reversible conversion reactions of α-BiF3 nanocomposite electrode at room temperature. The nanocomposite electrode was fabricated by ball milling and subsequent heat treatments. A pronounced XRD peak broadening indicated a disordered fine crystalline state in the electrode. The operando synchrotron radiation diffraction measurements revealed a quasi-reversible smooth crystallographic transformation between α-BiF3 and metallic Bi. The operando 7Li NMR measurement quantitatively showed reversible conversion reactions. The series of in-situ 7Li NMR spectra contained sharp signals from Li+ ions in the electrolyte and a broad signal associated with a solid phase of LiF. These signals followed a stoichiometric relationship that conformed to a three-electron BiF3 conversion pathway.

Delithiation and lithiation behaviors of ordered spinel LiNi0.5Mn1.5O4 and disordered spinel LiNi0.4Mn1.6O4 were investigated by using in situ (in operando) 7Li NMR and ex situ 6Li MAS NMR spectroscopy. The in situ 7Li monitoring of the ordered spinel revealed a clear appearance and subsequent disappearance of a new signal from the well-defined phase Li0.5Ni0.5Mn1.5O4, suggesting the two-phase reaction processes among Li1.0Ni0.5Mn1.5O4, Li0.5Ni0.5Mn1.5O4, and Li0.0Ni0.5Mn1.5O4. Also, for the disordered spinel, Li0.5Ni0.4Mn1.6O4 was identified with a broad distribution in Li environment. High-resolution 6Li MAS NMR spectra were also acquired for the delithiated and lithiated samples to understand the detailed local structure around Li ions. We suggested that the nominal Li-free phase Li0.0Ni0.5Mn1.5O4 can accommodate a small amount of Li ions in its structure. The tetragonal phases Li2.0Ni0.5Mn1.5O4 and Li2.0Ni0.4Mn1.6O4, which occurred when the cell was discharged down to 2.0 V, were very different in the Li environment from each other. It is found that 6, 7Li NMR is highly sensitive not only to the Ni/Mn ordering in LiNi0.5Mn1.5O4 but also to the valence changes of Ni and Mn on charge-discharge process.

1Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan 2Department Materials Structure Science, The Graduate University for Advanced Studies, Hayama 240-0193, Japan 3J-PARC Center, Japan Atomic Energy Agency, Naka-gun, Ibaraki 319-1195, Japan 4Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8530, Japan 5Institute for Advanced Materials Research, Hiroshima University, Higashi-Hiroshima 739-8530, Japan

The first preparation of Li-graphite intercalation compound (Li-GIC) was attempted by Hérold et al. in 1955. Since then, a lot of reports have been made mainly by the research groups in France, and with regard to the stage I and II compounds, it is clarified that they take the in-plane structures called by P(√3×√3)R30°. Though there have been many reports since 1970s, the detail discussion has not been done so far concerning the intercalation mechanism and in-plane structure of higher stage compounds. The first reason is that the concentration of Li species becomes smaller in the higher stages. The second reason is the strong preferred orientation of graphite. Such reasons make difficult to clarify the intercalation mechanism and in-plane structure. In order to improve the performance of Li-ion battery, it is essential to investigate the detail structure change of graphite electrode during the charge/discharge process. In this study, in order to elucidate the intercalation mechanism and structure change not only along c-axis, but also along the a,b-axes, we traced dynamically the intercalation reaction in Li-ion battery negative electrode by Operando measurement with synchrotron radiation diffraction.

Rechargeable lithium-ion batteries (LIBs) are currently accepted to be one of the most suitable energy storage resources in portable electronic devices because of their high gravimetric and volumetric energy density. To understand the behavior of Li^{+} ions on electrochemical lithium extraction/insertion process, we performed in situ^{7}Li nuclear magnetic resonance (NMR) measurements for LiC_{o}O_{2} cathode in a plastic cell battery, and the spectral evolutions of the ^{7}Li NMR signal of Li_{x}C_{o}O_{2} (0 ≤ x ≤ 1) were well investigated. Very narrow solid solution region of Li_{x}C_{o}O_{2} (∼0.99 ≤ x < 1) was explicitly defined from the large intensity reduction of Li_{x}C_{o}O_{2} signal at ∼0 ppm, which is related to the localized nature of the electronic spin of paramagnetic Co^{4+} ion formed at the very early delithiation stage. With further decreasing the signal intensity of LiC_{o}O_{2} , a Knight-shifted signal corresponding to an electrically conductive Li_{x}C_{o}O_{2} phase emerged atx = 0.97, which then monotonously decreased in intensity for x < 0.75 in accordance with the electrochemical lithium de-intercalation from Li_{x}C_{o}O_{2}. These observations acquired in situ fully confirm the earlier studies obtained in ex situ measurements, although the present study offers more quantitative information. Moreover, it was shown that the peak position of the NMR shift for Li_{x}C_{o}O_{2} moved as a function of lithium content, which behavior is analogous to the change in its c lattice parameter. Also, the growth and consumption of dendritic/mossy metallic lithium on the counter electrode was clearly observed during the charge/discharge cycles.

The atomic and electronic structures of binary Li2S-P2S5 glasses used as solid electrolytes are modeled by a combination of density functional theory (DFT) and reverse Monte Carlo (RMC) simulation using synchrotron X-ray diffraction, neutron diffraction, and Raman spectroscopy data. The ratio of PSx polyhedral anions based on the Raman spectroscopic results is reflected in the glassy structures of the 67Li2S-33P2S5, 70Li2S-30P2S5, and 75Li2S-25P2S5 glasses, and the plausible structures represent the lithium ion distributions around them. It is found that the edge sharing between PSx and LiSy polyhedra increases at a high Li2S content, and the free volume around PSx polyhedra decreases. It is conjectured that Li(+) ions around the face of PSx polyhedra are clearly affected by the polarization of anions. The electronic structure of the DFT/RMC model suggests that the electron transfer between the P ion and the bridging sulfur (BS) ion weakens the positive charge of the P ion in the P2S7 anions. The P2S7 anions of the weak electrostatic repulsion would causes it to more strongly attract Li(+) ions than the PS4 and P2S6 anions, and suppress the lithium ionic conduction. Thus, the control of the edge sharing between PSx and LiSy polyhedra without the electron transfer between the P ion and the BS ion is expected to facilitate lithium ionic conduction in the above solid electrolytes., 次世代硫化物ガラス電解質の構造解明に成功 －複雑なガラス構造中のリチウムイオン伝導制御に期待－. 京都大学プレスリリース. 2016-02-22.

We demonstrate a method to improve the promising hydrogen storage capabilities of ammonia borane by making composites with alkaline-earth metal hydrides using ball-milling technique. The ball-milling for the mixtures of alkaline-earth metal hydride (MgH2 or CaH2) and ammonia borane (AB) yields a destabilization compared with the ingredient of the mixture, showing the hydrogen capacity of 8.7 and 5.8 mass% at easily accessible dehydrogenation peak temperatures of 78 and 72 °C, respectively, without the unwanted by-product borazine. Through detailed analyses on the dehydrogenation performance of the composite at various ratios in the hydride and AB, we proposed a different chemical activation mechanism from that in the LiH/AB and NaH/AB systems reported in a previous literature.

Metal aluminum amides M[Al(NH2)4]x (M = K, Mg, and Ca; x = 1 and 2) were synthesized along with previously reported LiAl(NH2)4 and NaAl(NH2)4 by ball milling technique under liquid NH3. The profiles of synchrotron radiation X-ray diffraction suggest that KAl(NH2)4, Mg[Al(NH2)4]2 and Ca[Al(NH2)4]2 have been indexed with single phases, which have never been reported so far. Combination of both FT-IR and 27Al MAS/3QMAS nuclear magnetic resonance suggest that they all have an anion complex unit [Al(NH2)4]− as a basic component, indicating successful synthesis of the metal aluminum amides. Thermogravimetry-differential thermal analysis coupled with mass spectroscopy showed the release of NH3 below the temperatures of 140 °C during the thermal decomposition and a NH3 desorption peak temperature (Tdes) decreased with the increasing atomic number. Additionally, a relationship between 27Al isotropic chemical shift and Tdes was discussed. The present study gives an useful information that the thermal stability of the anion complex [Al(NH2)4]− can be controlled by a cation M.

Structural information on divalent cations such as Mg 2+ should have important implications for magmatic liquids because of their abundance in the Earth’s interior; nevertheless, little is confirmed about their coordination environments. We here apply a 25 Mg triple-quantum magic-angle spinning (3QMAS) NMR technique at an ultra-high magnetic field (21.8 T) and successfully show the occurrence of multiple Mg sites in MgSiO 3 glass. We find that these sites are distinguished by the degree of polyhedral distortion, not by the coordination number. The present study concludes that the highly distorted MgO 6 species occur in MgSiO 3 glass, in strong contrast with a recent radial distribution study.

The chemical structure of an amorphous slag with blast furnace composition was investigated by means of molecular dynamics simulation. Our calculation suggested that the slag had a depolymerized network of SiO4 and AlO4 tetrahedra with interstitial cations, Ca2+ and Mg2+. The structural properties such as average coordination number obtained at 300 K were in good agreement with a recent NMR study, supporting the feasibility of the structure prediction by such simulation technique. At 1 873 K, the coordination numbers of the ions almost remained unchanged, while the intertetrahedral angles were found to be narrower, and the Qn distribution of AlO4 tetrahedra was slightly modified. The small amount but significant incorporation of MgO and Al2O3 influences the network connectivity, which should affect macroscopic properties such as viscosity.

The atomic and electronic structures of binary Li2S-P2S5 glasses used as solid electrolytes are modeled by a combination of density functional theory (DFT) and reverse Monte Carlo (RMC) simulation using synchrotron X-ray diffraction, neutron diffraction, and Raman spectroscopy data. The ratio of PSx polyhedral anions based on the Raman spectroscopic results is reflected in the glassy structures of the 67Li2S-33P2S5, 70Li2S-30P2S5, and 75Li2S-25P2S5 glasses, and the plausible structures represent the lithium ion distributions around them. It is found that the edge sharing between PSx and LiSy polyhedra increases at a high Li2S content, and the free volume around PSx polyhedra decreases. It is conjectured that Li(+) ions around the face of PSx polyhedra are clearly affected by the polarization of anions. The electronic structure of the DFT/RMC model suggests that the electron transfer between the P ion and the bridging sulfur (BS) ion weakens the positive charge of the P ion in the P2S7 anions. The P2S7 anions of the weak electrostatic repulsion would causes it to more strongly attract Li(+) ions than the PS4 and P2S6 anions, and suppress the lithium ionic conduction. Thus, the control of the edge sharing between PSx and LiSy polyhedra without the electron transfer between the P ion and the BS ion is expected to facilitate lithium ionic conduction in the above solid electrolytes.

Lithium- and Manganese-Rich layered oxides (LMRs) are one of the promising candidates of positive electrode materials for the advanced LIB due to their high reversible capacities. The chemical formula is often described as xLi2MnO3•(1–x)LiMO2 that consists of Li2MnO3- and LiMO2-rich nano-domains. The LMR-based electrodes show a voltage plateau at ca. 4.5 V in the initial charge process, which leads to an irreversible capacity. This plateau is understood to appear for the activation of Li2MnO3.[1,2] This activation process is not thoroughly understood yet and the elucidation of this reaction would lead to the practical use of this material. Some groups have reported that the charge compensation on the delithiation from Li2MnO3 is associated with the oxidation of oxide ion including O2release from the structure.[3,4] The present work focuses on clarifying the structural changes taking place inside LMR bulk at the initial delithiation (charge) using SR-X ray diffraction, STEM, and solid-state NMR.[5] SR-XRD profiles showed that all the diffraction intensities were gradually decreased and broadened during the initial charge up to 4.8 V, which indicated that the initial delithiation caused the change to highly disordered material. The high-resolution 6Li MAS NMR spectra showed that Li+ was monotonously extracted from both the Li and TM layers. EELS mapping by STEM suggested that the Li+extraction from the sample of 50% SOC occurred in a biphasic manner inside a single particle. The lattice structures of the active material after charge-discharge cycle was also examined on samples at the 20th discharged and 21stcharged states. This work was supported by the Research and Development Initiative for Scientific Innovation of New Generation Batteries (RISING) and the Research and Development Initiative for Scientific Innovation of New Generation Batteries II (RISING II) projects from the New Energy and Industrial Technology Development Organization (NEDO), Japan. [1] Thackeray et al., J. Mater. Chem., 2007, 17, 3112. [2] Yu & Zhou, J. Phys. Chem. Lett., 2013, 4, 1268. [3] Yu et al., J. Electrochem. Soc., 2009, 156, A417. [4] Oishi et al., J. Mater. Chem. A, 2016, 4, 9293. [5] Shimoda et al., J. Mater. Chem. A, 2017, 5, 6695.

In the cell model, a thermodynamic model of slag, the fractions of heterogeneous cation pairs are calculated which compose cells with an oxygen atom in between by the minimization of free energy of slag with energy parameters. On the other hand, by using NMR the fractions can be measured. Therefore, a new method can be proposed to evaluate the energy parameter values used in the cell model so that the calculated fractions in the slag with its minimum of free energy coincide with the measurement. The possibility of this evaluation method of energy parameter values was examined by the comparison of bridging oxygen/non-bridging oxygen (BO/NBO) ratio calculated by the cell model with energy parameter assessed elsewhere with measured BO/NBO ratio by NMR. The BO/NBO ratios of three SiO2–Al2O3–CaO slags with different basicities calculated by the use of cell model with energy parameter values assessed elsewhere were 42.5/57.5, 45/55 and 70/30, respectively. On the other hand, from 17OMAS spectrum and 27Al→17O CP/MAS spectrum of the same slags fully labeled and calcinated at 1600 centigrade degree, the ratios of BO/NBO in the slags were determined as 48.5/51.5, 42/58 and 76/24, respectively. This agreement supports the energy parameter values assessed elsewhere and gives a good expectation to the proposed method.

Ionic conductors are promising electrolyte of solid-state batteries. Their major advantages are high ionic conductivity, electrochemical stability and inflammability. Various works have been done to explain the origin of high ionic conductivity. For example, the high ionic conductivity in the order of 10-3 Scm-1 at room temperature of Li7P3S11 metastable crystal, which is synthesized by annealing (Li2S)70(P2S5)30 glass at 513 K [1, 2], has attracted much interest. By analyzing its synchrotron X-ray powder diffraction pattern, Yamane et al. showed that Li ions are situated in the conduction pathways formed by PS4 tetrahedra and P2S7 ditetrahedra units [3]. The conduction pathway has been attributed to as the structural origin of high conductivity. We thus applied 6/7Li and 31P solid-state NMR to examine structural/dynamical origins of high conductivity of glass and glass-ceramics Li2S-P2S5 samples. (Li2S) x (P2S5)100 – x (mol %; x = 70 and 75) glasses were prepared by mechanical milling. Li2S and P2S5 crystalline powders were used as the starting materials. The glass-ceramics sample was prepared by heating the glass at 290 °C for 2 h. All the processes were performed in a dry Ar atmosphere. The NMR measurements were made using a JEOL ECA600 NMR spectrometer at 14 T. The MAS NMR spectra were observed by using a single pulse with the Hahn-echo. The spin-lattice relaxation times (T 1) were measured under MAS by using the conventional saturation-recovery method. To examine the origin of the linewidth of signals of 31P NMR, we applied the two-dimensional (2D) Radio Frequency Driven Recoupling (2D-RFDR). It was performed with an experimentally optimized p pulse length of 2.2 ms using XY16 phase cycling. While 6/7Li and 31P spin-lattice relaxation times exhibit that 31P relaxation of the glass sample is governed by 7Li motion, those of the glass-ceramics sample indicate 31P motion is appreciable at temperatures higher than ca. 310 K. The results showed that dynamics of the PS4 tetrahedra and P2S7 ditetrahedra units in (Li2S)70(P2S5)30 glass-ceramic is not appreciable at temperatures below ca. 310 K, where the ionic conductivity is low. At higher temperatures, however, significant motion especially for the P2S7 ditetrahedra unit is apparent in both of 31P-T 1 and 31P MAS lineshapes. High-resolution 31P MAS NMR spectra of the glass-ceramics sample bear the 31P signals of PS4, P2S7, and P2S6. In addition to these signals reported previously, we found two signals, which have not yet been assigned. Interestingly, these two signals are merged into the P2S7 signal at higher temperatures. Further, we applied 31P-31P dipolar correlation experiment to examine the 31P linewidth, which is reduced by motion at higher temperatures. It was shown that the linewidth of the P2S7 unit is attributable to distribution of local structures of and around the P2S7 ditetrahedra unit. With these, we concluded that the significant motional fluctuation of the P2S7ditetrahedra unit at above 310 K allows facile diffusive motion of lithium ions, leading to the high ionic conductivity [4]. As has been described, NMR is a powerful tool to correlate the local environment of ions and ion transportation (= ionic conductivity) and can be applied to other systems including F- (or other ion) conductive systems. 1) F. Mizuno et al., Adv. Mater. 17, 918-921 (2005). 2) F. Mizuno et al., Electrochem. Solid-State Lett. 8, A603-A606 (2005). 3) H. Yamane et al., Solid State Ionics 178, 1163–1167 (2007). 4) M. Murakami et al., J. Phys. Chem. C 119, 24248-2425 (2015). Acknowledgment: This work was financially supported by the RISING project of the New Energy and Industrial Technology Development Organization (NEDO).

Introduction LiFePO4 is a promising cathode material for lithium-ion batteries1 as it exhibits high rate performance.2 The origin of the high rate performance exemplified in LiFePO4 should provide design principles for further development of high rate cathode materials. The (dis)charge reaction of LiFePO4 proceeds through a two phase behavior between Li-rich Li1-αFePO4 (LFP) and Li-poor LiβFePO4 (FP).3 Under high rate cycling, we revealed the formation of a metastable phase of Li x FePO4 (x = 0.6–0.75) (L x FP) which acts as a buffer layer between LFP and FP.4 However, the detailed reaction between LFP and FP during high rate cycling has not fully been understood due to short lifetime of metastable L x FP phase. To investigate the phase transition mechanism, with respect to L x FP phase, cycling at low temperatures was performed because metastable L x FP phase might have long lifetime to fully capture its spatial-temporal formation. Phase transition mechanism is analyzed by operando time-resolved X-ray diffraction (TR-XRD) measurements at low temperatures. Experimental Three-electrode aluminum-laminated pouch-type cells were fabricated for operando TR-XRD measurements. LiFePO4/C particles were synthesized by hydrothermal methods.4 The working electrode comprised a composite mixture of LiFePO4/C, carbon black (Denka), and polyvinylidene fluoride (Kureha) at a ratio of 75:15:10 (wt%) and coated on aluminum foil current collectors. Lithium foil was used as counter and reference electrodes. The electrolyte was 1 mol dm–3 of LiPF6 dissolved in a mixture of ethylene carbonate and ethyl methyl carbonate (3:7 volume ratio, Battery Grade, Kishida). operando TR-XRD measurements were performed in transmission mode at the beam line BL28XU at SPring-8 (Japan). The wavelength of X-ray was 0.9998Å. The cells were set at fixed temperatures (–5, 5 and 25 °C) using temperature-controlled jackets,5 and were charged and discharged at constant rates of 1C (170 mA g–1), 5C (850 mA g–1) and 10C (1700 mA g–1) between 2.0 and 4.3 V versus Li/Li+ for 5 cycles. Results and Discussions In the charge-discharge cycle at 25ºC and rate of 1C, operando TR-XRD pattern looks typical of the two-phase reaction between the LFP and FP phases. LFP 211 and 020 diffractions disappeared and the FP 211 and 020 diffractions simultaneously appeared, as the cell was charged. Conversely, the FP diffractions disappeared and the LFP diffractions appeared, as the cell was discharged. On the other hand, the behavior of the operando TR-XRD patterns in the first charging at –5°C is different from that at 25°C. The intensity bridge between LFP and FP 211 was observed. This indicates the formation of the LxFP phase even in the first charging. The diffraction peaks of FP phase disappeared and the peak of the LxFP phase at 19.4° appeared as the cells were discharged. These results suggest that the first charging process is different from the first discharging process except for the condition of 1C rate and 25°C. Moreover, at 10C rates and –5°C, the fact that the discharging finishes at the single LxFP phase suggests that the phase transition between the LxFP and LFP phases is slow. The difference of phase transition kinetics between LFP/LxFP and LxFP/FP cause the initial irreversible capacity at high rate, and/or low temperature conditions. References (1) Padhi, A. K.; Nanjundaswamy, K. S.; Goodenough, J. B. J. Electrochem. Soc., 1997, 144, 1188. (2) Meethong, N.; Kao, Y.-H.; Carter, W. C.; Chiang, Y.-M. Chem. Mater., 2010, 22, 1088. (3) Yamada, A.; Koizumi, H.; Nishimura, S. I.; Sonoyama, N.; Kanno, R.; Yonemura, M.; Nakamura, T.; Kobayashi, Y. Nat. Mater., 2006, 5, 357. (4) Orikasa, Y.; Maeda, T.; Koyama, Y.; Murayama, H.; Fukuda, K.; Tanida, H.; Arai, H.; Matsubara, E.; Uchimoto, Y.; Ogumi, Z. J. Am. Chem. Soc., 2013, 135, 5497. (5) Takahashi, I.; Murayama, H.; Sato, K.; Naka, T.; Kitada, K.; Fukuda, K.; Koyama, Y.; Arai, H.; Matsubara, E.; Uchimoto, Y.; Ogumi, Z. J. Mater. Chem. A, 2014, 2, 15414. Acknowledgement This study was partially supported by the Research and Development Initiative for Scientific Innovation of New Generation Battery (RISING) Project under the auspices of New Energy and Industrial Technology Development Organization (NEDO), Japan.

1. Introduction Li-rich type (manganese) oxides are one of the most featured cathodes for lithium ion batteries in recent years, owing to their high capacity and cyclability. In these cathodes, partial substitution of manganese by other transition metals such as Ni and Co has been proposed and shown to be effective in improving the performance, [1] however, the role of such metals in the battery performance has not been clarified in detail. We have synthesized Ni ion substituted Li excess manganese oxides (Li2Mn1-xNixO3) as a simple model of Li2MeO3 phase in solid solution cathode to understand the effect of introduced Ni by using the combination of in situ X-ray absorption spectroscopy (XAS) and X-ray diffraction spectroscopy (XDS) analysis. Diffraction anomalous fine structure (DAFS) spectra are achieved by XDS analysis, that there were quantitatively showed potential-dependent transbilayer migration of nickel and manganese and their reversibility. 2. Experimental procedure The active material of nickel substituted Li2MnO3 (Li2Mn1-x NixO3, x = 0 ~ 0.25) was prepared from solid phase calcination at 1173 K for 12 h in air. The working electrode consisted of active material (80 wt.%), acetylene black (10 wt.%) and polyvinylidene difluoride (PVdF) binder (10 wt.%), coated on aluminum current foil. The electrochemical measurements of the electrode were employed using aluminum pouch type cells, metallic lithium as counter and reference electrodes, 1 mol dm-3 LiPF6 in a 3:7 mixture of EC/DMC, and a polyolefin film as a separator. The electrochemical charge and discharge tests were performed at room temperature and the potential range was between 2.0 and 4.8 V. XAS measurements were performed by the three-electrode cell with charging and discharging processes (in Operando). The XAS measurements of the Ni-K and Mn-K edge region were performed using a solid-state detector at beamlines BL28XU in SPring-8 (Hyogo, Japan). The XDS measurements were conducted at beamline BL28XU, SPring-8, Japan. A two-dimensional Pilatus detector (Dectris Co., Ltd.) was mounted onto an arm of a multi-axis goniometer and was used to measure the diffraction profile, and two ionization chamber was used for the absorption correction of the DAFS spectra. 3. Results and Discussion The obtained X-ray absorption near edge structure (XANES) region spectra at N-K energy region of Li2Mn1-x NixO3 (x = 0.25) in the 1st charging and discharging processes are shown in Fig. 1. The edge energy was shifted to high energy, which is suggested that Ni element function as a charge compensation species. However the end of charging region around 4.7 V to 4.8 V was shifted to low energy as seen in previous XAS report [2], which means the reduction of nickel on average in this region. As our group have published before,[3] XANES-like spectra only from selected sites (i.e. DAFS spectra) can be extracted from the XDS analysis. Fig. 2 shows the DAFS spectra of initial sample. The Ni-K edge XANES-like spectra shows that there was cation mixing in the lithium layer of the pristine material. In contrast, Mn-K edge XANES-like spectra shows that manganese mostly occupied in transition metal layer. XDS analysis of the fully charged sample indicated that Ni element further migrated to the lithium layer. These analytical approaches are important to understand the metal migration behavior as a function of operation potential together with the charge compensation mechanism during electrochemical charging and discharging. References [1] Thackeray, M. M.et al., J. Mater. Chem. 2007, 17, 3112. [2] Ito, A. et al., J. Power Sources 2011, 196, 6828. [3] Kawaguchi, T. et al., J. Synchrotron Rad. 2014, 21, 1247. Acknowledgement This work was supported by RISING of NEDO. Fig. 1 In situ Ni-K edge XAS spectra at 1st charging to 4.5V (a), irreversible plateau region (b), end of charging region 4.7-4.8 V (c), discharging to 2.0 V (d). Fig. 2 DAFS spectra of Ni-K edge XANES-like spectra (a) and Mn-K edge XANES-like spectra (b). Figure 1

Magnesium rechargeable battery, which uses magnesium metal anode, is one of the candidates for the next generation batteries. The magnesium metal anode has a high theoretical volumetric capacity (3832 mAh/cm3), and relative low reduction potential (-2.356 V vs. standard hydrogen potential). However, conventional electrolytes consisting of inorganic salts and ester solvents, as widely used in lithium ion batteries, do not occur reversible deposition/dissolution of magnesium metal. This is because a passivation layer is formed at the magnesium metal anode surface that blocks both magnesium ions and electron transport. The limitation of available electrolytes prevents the magnesium battery from being used in a practical application. Recently, it has been reported that reversible magnesium deposition/dissolution reactions can occur in inorganic magnesium salts dissolved in glyme-based solvents electrolytes 2, 3. However, the reaction mechanism of magnesium metal anode has not been clearly understood. To clarify the reaction mechanism, it is necessary to investigate the interfacial structure of magnesium ion at anode/electrolyte interface. In this study, we investigated the bulk structure of the glyme-based electrolyte using Raman spectroscopy, X-ray absorption spectroscopy (XAS) and the theoretical calculation. Furthermore, we observed the electronic and local structure of the electrolyte at the interface during magnesium deposition using operando soft x-ray absorption spectroscopy. 0.5 M Mg(TFSA)2/triglyme and 0.5 M Mg(TFSA)2/2-MeTHF electrolytes were prepared by stirring Mg(TFSA)2 with triglyme or 2-MeTHF in an Ar-filled glove box. Raman spectroscopic measurements were carried out using LabRAM HR-800 equipped with He-Ne laser (633 nm) at room temperature. operando XAS measurements at Mg K-edge were conducted at the beam line BL27SU at SPring-8 (Japan). XAS spectra were obtained at different potential during magnesium deposition. Magnesium deposition/dissolution occurred in Mg(TFSA)2/triglyme as observed in previous report3. In contrast to Mg(TFSA)2/triglyme, magnesium metal deposition did not observe in Mg(TFSA)2/2-MeTHF. Raman spectroscopy showed that TFSA anion exists as uncoordinated state with magnesium ion in the Mg(TFSA)2/triglyme, while TFSA anion strongly coordinates with magnesium ion in the 2-MeTHF-based electrolyte. operando Mg K-edge XAS observed that the local structure attributed to first coordination shell changed more smaller with decreasing potential in the Mg(TFSA)2/triglyme than in the Mg(TFSA)2/2-MeTHF at anode/electrolyte interface. In the Mg(TFSA)2/triglyme, the solvation structure of magnesium ion without coordination of TFSA anion, may suppress its local structure change during approaching the anode/electrolyte interface, resulting in the reversible magnesium deposition/dissolution. ACKNOWLEDGMENTS This study was partially supported by Synchrotron radiation experiment was performed at BL27SU of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI). REFERENCES [1] Aurbach, D.; Lu, Z.; Schechter, A.; Gofer, Y.; Gizbar, H.; Turgeman, R.; Cohen, Y.; Moshkovich M.; Levi, E., Nature, 2000, 407, 724-727. [2] Ha, S.-Y.; Lee, Y.-W.; Woo, S. W.; Koo, B.; Kim, J.-S.; Cho, J.; Lee, K. T.; Choi, N.-S., ACS Appl. Mater. Interfaces, 2014, 6, 4063-4073. [3] Orikasa, Y.; Masese, T.; Koyama, Y.; Mori, T.; Hattori, M.; Yamamoto, K.; Okado, T.; Huang, Z. -D.; Minato, T.; Tassel, C.; Kim, J.; Kobayashi, Y.; Abe, T.; Kageyama, H.; Uchimoto, Y., Sci. Rep., 2014, 4, 5622.

Magnesium rechargeable batteries have much attention for next generation batteries because of the high theoretical volumetric capacity, safety, and abundance of magnesium metal anode. In order to improve the efficiency of magnesium metal anode, it is required to develop the electrolyte that enables magnesium deposition and dissolution reversibly. Although Grignard reagents have been widely known as the electrolyte for magnesium deposition/dissolution[1], the stability of the electrolytes in high potential and their corrosive nature are major problems. In recent years, magnesium deposition/dissolution in magnesium inorganic salts with triglyme solvents have been reported[2,3]. For the further development of electrolyte for magnesium batteries, the reaction mechanism at electrolyte/magnesium metal interface should be elucidated. In this study, we have developed operando soft X-ray measurement system and apply to the analysis of electronic and local structure of electrolyte during magnesium deposition. Furthermore, bulk structure of electrolyte is investigated by Raman spectroscopy, X-ray absorption spectroscopy (XAS) and the theoretical calculation. 0.5 M Mg(TFSA)2/triglyme and 0.5 M Mg(TFSA)2/2-MeTHF electrolytes were prepared by mixing Mg(TFSA)2 (KISHIDA CHEMICAL Co., Ltd., 99.9%>) with triglyme (KISHIDA CHEMICAL Co., Ltd. 99%>) or 2-MeTHF (Merck, 98%>) in an Ar-filled glove box. Electrochemical properties of the electrolyte were investigated by cyclic voltammetry (CV) with the three-electrode cell. Platinum plate and magnesium rod were used as working electrode and counter electrode, respectively. Operando XAS measurements at Mg K-edge were carried out at the beam line BL27SU at SPring-8 (Japan). XAS spectra were obtained at different potential during magnesium deposition. Raman spectroscopic measurements were carried out using LabRAM HR-800 (HORIBA, Ltd.) equipped with He-Ne laser (633 nm) at room temperature. While magnesium deposition/dissolution is observed in Mg(TFSA)2/triglyme and Grignard system, magnesium is not deposited in Mg(TFSA)2/2-MeTHF. From the results of Raman spectroscopy, TFSA anion exists as uncoordinated state with magnesium ion in the triglyme system, while TFSA anion coordinates with magnesium ion in the 2-MeTHF system. Fourier transform from Mg K-edge EXAFS oscillation measured at different potentials in 0.5 M Mg(TFSA)2/triglyme and 0.5 M Mg(TFSA)2/2-MeTHF indicate that peak intensity of Mg-O bond decreases with decreasing potential.The decreases of peak intensity reflect the desolvation process of triglyme and 2-MeTHF from magnesium ion. These results suggested that reason of high overpotential in 0.5 M Mg(TFSA)2/2-MeTHF is specific adsorption of TFSA anion. The specific adsorped TFSA anion may inhibits charge transfer raction of magnesium ion. ACKNOWLEDGMENTS This study was partially supported by the Research and Development Initiative for Scientific Innovation of New Generation Battery (RISING) Project under the auspices of New Energy and Industrial Technology Development Organization (NEDO), Japan. Synchrotron radiation experiment was performed at BL27SU of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI). REFERENCES [1] Aurbach, D.; Lu, Z.; Schechter, A.; Gofer, Y.; Gizbar, H.; Turgeman, R.; Cohen, Y.; Moshkovich M.; Levi, E., Nature, 407, 724 (2000). [2] Ha, S.-Y.; Lee, Y.-W.; Woo, S.W.; Koo, B.; Kim, J.-S.; Cho, J.; Lee, K.T.; Choi, N.-S., ACS Appl. Mater. Interfaces 6, 4063 (2014). [3] Orikasa, Y.; Masese, T.; Koyama, Y.; Mori, T.; Hattori, M.; Yamamoto, K.; Okado, T.; Huang, Z. -D.; Minato, T.; Tassel, C.; Kim, J.; Kobayashi, Y.; Abe, T.; Kageyama, H.; Uchimoto, Y., Sci. Rep., 4, 5622 (2014).

We have reported the 25Mg triple-quantum magic-angle spinning (3QMAS) NMR spectra of silicate glasses. The two-dimensional spectra suggest that the magnesium ions in MgSiO3, CaMgSi2O6, Ca2MgSi2O7, Mg3Al2Si3O12, and Li2MgSi2O6 glasses are mainly in octahedral environments, although in Na2MgSi2O6, K2MgSi2O6, and K2MgSi5O12 glasses they form tetrahedral species. We discussed the coordination environments of Mg based on the field strength of competing Mg2+, Ca2+, Na+, K+, and Li+ cations, and convincingly demonstrated that there is a correlation between them. These results indicate that the two-dimensional NMR spectroscopy such as MQMAS technique is a very useful method to analyze the local environments of nonframework cations in noncrystalline solids.