In sheet-type all-solid-state lithium-ion batteries with the sulfide-based solid electrolyte, composite electrodes consist of active material, solid electrolyte, conductive additive material, and binder. Thus, they form a three-dimensional ionic and electronic conduction pass. In composite electrodes, the reaction inhomogeneity derived from their morphology exerts a remarkable effect on battery performance. In this study, we prepared sheet-type composite electrodes for all-solid-state lithium-ion batteries with the sulfide-based solid electrolyte using different binder materials with different solvents and investigated the reaction distribution within the electrodes using the 2D-imaging X-ray absorption spectroscopy. Thus, we demonstrated that the dominant factor of the reaction distribution formation is the ionic conduction, depending on the structure of the composite electrode, and that the structure is influenced by the combination between the binder and the solvent used in the preparation of the sheet-type composite electrode.

In this study, the efficiency of ionic transport through proton-conducting ceramic electrolytes for energy conversion applications was discussed.

The oxygen vacancy containing Li-rich cathode Li1.2Ni0.13Co0.13Mn0.54O2−δ showed excellent energy density retention.

Shape memory alloys recover their original shape after deformation, making them useful for a variety of specialized applications. Superelastic behavior begins at the critical stress, which tends to increase with increasing temperature for metal shape memory alloys. Temperature dependence is a common feature that often restricts the use of metal shape memory alloys in applications. We discovered an iron-based superelastic alloy system in which the critical stress can be optimized. Our Fe-Mn-Al-Cr-Ni alloys have a controllable temperature dependence that goes from positive to negative, depending on the chromium content. This phenomenon includes a temperature-invariant stress dependence. This behavior is highly desirable for a range of outer space–based and other applications that involve large temperature fluctuations.

Oxygen release from a Li-rich cathode material was quantitatively evaluated and discussed based on defect chemistry and thermodynamics.

Two-dimensional X-ray absorption spectroscopy was carried out to observe the reaction distribution in a LiCoO2 composite electrode from the shift of the peak top energy in Co K-edge X-ray absorption spectra. The influence of ionic transportation to the inhomogeneous reaction was evaluated by using the model electrode, which sandwiched the LiCoO2 composite electrode between an aluminum foil and a polyimide ion blocking layer. When the model electrode was charged with the currents of 6, 9, and 12 mA cm–2, the observed capacities were 51, 20, and 12 mAh g–1 and the charged areas visualized from the shift of the peak top energy in Co K-edge X-ray absorption spectra were formed within ca. 700, 500, and 200 μm from the edge of the electrode, respectively. The observed reaction distribution indicated that the electrochemically active region decreases with increasing the current density because of the large potential loss of the electrochemical processes.

The performances of electrochemical systems such as solid-state batteries (SSBs) can be severely hindered by the three-dimensional (3D) and mesoscopically inhomogeneous electrochemical reactions that take place in the electrodes. However, the majority of existing methods for analyzing such inhomogeneous reactions are restricted to one-or two-dimensional observations. Herein, we performed 3D operando imaging of the mesoscopically inhomogeneous electrochemical reaction in a composite SSB electrode using hard X-ray computedtomography with X-ray absorption near edge structure spectroscopy (CT-XANES). The 3D inhomogeneous reaction evolution during (dis)charge was successfully visualized for the first time. Furthermore, our 3D quantitative analysis unambiguously revealed the origin of the inhomogeneous reaction in the investigated electrode. Our results suggested that slow ion transport through active material particles can considerably restrict SSB performances. Our technique therefore provides new insights into the electrochemical reactions taking place in electrodes and enables us to maximize the performance of electrochemical systems.

Young's and shear moduli and Poisson's ratio of La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF6428), La0.6Sr0.4CoO3−δ (LSC), and La0.6Sr0.4FeO3−δ (LSF) were investigated in the temperature range from room temperature to 1173 K and in the oxygen partial pressure, P(O2), range from 1 × 10−1 to 1 × 10−4 bar by the resonance method. The Young's and the shear moduli decreased with increasing temperature at low temperatures and drastically increased at intermediate temperatures. The drastic increase was associated with the second‐order phase transition. In contrast, the Poisson's ratios of LSCF6428, LSC, and LSF decreased around the phase transition temperature. The P(O2) dependence of the Young's and the shear moduli of LSCF6428 showed different tendencies depending on temperature. At 873 K, the Young's and the shear moduli were almost independent of P(O2), whereas they increased with decreasing P(O2) at 973 K. At 1073 K, they first increased with decreasing P(O2) under higher P(O2) and then gradually decreased under lower P(O2). At 1173 K, they monotonically decreased with decreasing P(O2). Such complicated P(O2) dependence were interpreted by complex influences of the phase transition, the chemical expansion and the variation of the oxygen nonstoichiometry and the cation mean valence.