東京工業大学 · 工学
Arai教授の研究室は、リチウムイオン電池の高効率・高安定性な電極材料の開発を主眼としており、特にニッケル・マンガン尖晶石系正極材料やリチウムチタンニカナイド系負極材料の構造・物性関係をX線吸着スペクトロスコピー（XANES/XAFS）やX線回折（XRD）を用いて精密に解明しています。また、電極反応の動的挙動や熱的安定性の向上に関する基礎的知見を提供し、次世代バッテリーデバイスの実現に貢献しています。
Figures are computed from collected data and may differ slightly.
We report the synthesis and electrochemical properties of highly stoichiometric samples. With the excess lithium method, samples with a well‐defined layered structure can be prepared in air. A large rechargeable capacity of about 200 mAh g−1 is obtained for 10% substitutives. Structural changes during charging and lithium ordering phenomena are discussed. We describe the thermal behavior of the substitutives and report the enhanced thermal stability and large rechargeable capacity of the mangane
Lithium nickelate is a promising electrode material for lithium-ion batteries, however, its low thermal stability is a problem that should be solved. We studied the thermal stability of delithiated lithium nickelate compounds in the presence of electrolyte solvents/solutions. We measured the exothermal heat generation of the reaction system using differential scanning calorimetry. We examined simple systems such as ethylene carbonate with using hermetically sealed pans that allowed us to perform
The activity and stability of bifunctional air electrodes for electrically rechargeable metal air batteries were investigated using ac impedance spectroscopy. The poly(tetrafluroethylene) bonded electrodes consisted of a perovskite-type catalyst (La<sub>0.6</sub>Ca<sub>0.4</sub>CoO<sub>3</sub>) dispersed on high surface area carbon (Ketjen black) or on graphitized carbon (Vulcan XC 72). The impedance spectra were analyzed using an equivalent circuit containing two finite diffusion terms. The dif
In situ time-resolved X-ray absorption near-edge structure (XANES) and X-ray diffraction (XRD) measurements are applied to track the phase transition processes of LixNi0.5Mn1.5O4, which is one of the most promising positive electrode materials for lithium ion batteries with its high redox potential of 4.7 V vs. Li/Li+ and good rate capability. Thanks to the high time resolution brought by a strong synchrotron X-ray beam, the XANES and XRD measurements separately capture the three phases involved
X-Ray absorption fine structure (XAFS) spectroscopy was carried out on submicron sized TiO2-B, which is one of the promising candidates for negative electrode materials, in order to clarify the electronic and local structural changes during its lithium-ion insertion process. From the extended X-ray absorption fine structure (EXAFS) results of lithiated LixTiO2-B, we propose the changes in lithium-ion insertion sites during electrochemical discharging. The lithium ions are inserted into the five-
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