Yuta Kimura 교수

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 <i>operando</i> imaging of the mesoscopically inhomogeneous electrochemical reaction in a composite SSB e

Designing composite electrodes with optimal microstructure, composition, and choice of active material (AM) as well as solid electrolyte (SE) is critically important for the development of high-performance solid-state batteries (SSBs). To optimize AM loading, which includes loading amount, composition, and dispersion state, and to maximize AM utilization in composite SSB electrodes, we need to precisely understand how the AM loading affects electrochemical reactions taking place in the electrode

Young's and shear moduli and Poisson's ratio of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ ( LSCF 6428), La 0.6 Sr 0.4 Co O 3−δ ( LSC ), and La 0.6 Sr 0.4 FeO 3−δ ( LSF ) were investigated in the temperature range from room temperature to 1173 K and in the oxygen partial pressure, P ( O 2 ), 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 dr

Self-switching nanodiodes (SSDs) using zinc oxide (ZnO) were fabricated on glass substrates. The SSDs using ZnO have attracted significant attention as transparent devices because of their low cost, abundance in nature, and so on. Rectification characteristics in the SSDs were resemblance to the characteristics of conventional diodes with use of a doping junction or a barrier structure. The changes in characteristics depending on the shape of SSDs were investigated. Channel widths in the SSD of

Abstract Introducing a coating layer at an active material /solid electrolyte interface is crucial for ensuring thermodynamic stability of the solid electrolyte at interfaces in solid-state batteries. To thermodynamically protect the solid electrolyte, coating layers must maintain lithium chemical potential ( μ Li ) at coating layer/solid electrolyte interfaces within the electrochemical window of the solid electrolyte. However, a general coating layer design principle to achieve this remains un

We evaluated the influence of aging on mechanical properties of 8% yttria-doped zirconia (8YSZ) from room temperature to 1200 K. The temperature dependence of the dynamic Young’s and shear moduli of 8YSZ with and without the aging treatment was investigated by using a resonance method. The dynamic Young’s and shear moduli of 8YSZ without the aging treatment decreased by 33% below 700 K and gradually increased at higher temperatures with increasing temperature. On the other hand, those with the a

We experimentally evaluated the influence of stress on the Li chemical potential (μLi) and phase equilibrium in the two-phase battery electrode materials through the emf measurements while applying a mechanical load. In our measurements, we prepared an electrochemical cell by depositing a thin film of a two-phase electrode material (LiFePO4 or LiCoO2 in the two-phase region) on each of the solid electrolyte surfaces. Then we applied a mechanical load to the electrochemical cell through four-poin

The temperature dependency of the dynamic Young's modulus and of the internal friction of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF6428) was investigated by dynamic mechanical analysis. The significant decrease in the storage modulus of LSCF6428 with low oxygen vacancy concentration (LSCF1) and a following broad and asymmetric peak (P1) were interpreted as resulting from the motion of ferroelastic domain walls with a distribution of the relaxation time. The storage modulus of the LSCF6428 with higher oxyge

Rapid quenching is one of the methods for preparing silicide/Si composite alloy as an active material for negative electrode in lithium-ion batteries. In this study, we focused on the method's control over the positional relation between the Si and silicide phase by changing the additive elements. Various Si-alloys and the relationship between their lithiation and delithiation properties and their arrangement was investigated.

The stress-strain relationships of La 0.6 Sr 0.4 CoO 3- δ (LSC), La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3- δ (LSCF6428) and La 0.6 Sr 0.4 FeO 3- δ (LSF) was evaluated by uniaxial compression tests in the temperature range between room temperature and 1173 K. A nonlinear stress-strain relationship with a residual strain was observed below the phase transition temperature, while an almost linear relationship with no residual strain was observed above the phase transition temperature. Cyclic tests revealed

For devices encountering long-term stability challenges, a precise evaluation of degradation is of paramount importance. However, methods for comprehensively elucidating the degradation mechanisms in devices, particularly those undergoing dynamic chemical and mechanical changes during operation, such as batteries, are limited. Here, a method is presented using operando computed tomography combined with X-ray absorption near-edge structure spectroscopy (CT-XANES) that can directly track the evolu

We have reported the effects of substituting a transition metal in silicide on the electrochemical performance of the silicide/Si composite anode for lithium-ion batteries (LIBs); the Cr_0.5V_0.5Si₂/Si electrode exhibited much better cyclability compared with CrSi₂/Si and VSi₂/Si electrodes. Herein, we investigated the electrochemical performance of a Cr _<i>x</i> V_1-<i>x</i> Si₂/Si slurry electrode for its appl

We report on the fabrication and characterization of the self-switching nano-diodes using zinc oxide films grown on glass substrates for use as transparent rectifiers. Diode-like characteristics were clearly observed. The current clearly increased with increases in the channel length and the turn-on voltage sifted toward zero volt with decreasing the channel width. Overall, we found that the rectifying characteristics can be controlled by the device geometry. The rectifying characteristics were