Tokyo Institute of Technology · Engineering
Professor Hajime Arai's research lab specializes in advanced materials for energy storage, with a primary focus on developing and characterizing high-performance electrode materials for lithium-ion and metal-air batteries. The lab investigates the structural, electronic, and electrochemical properties of layered oxides, spinel-type materials, and titanium-based anodes using in situ and operando techniques such as XANES, XRD, and XAFS. Key research directions include enhancing thermal stability, understanding phase transitions during charge-discharge cycles, and improving the kinetics and durability of battery materials under practical operating conditions. The lab also explores bifunctional catalysts for metal-air batteries, emphasizing electrode-electrolyte interfacial behavior and reaction mechanisms.
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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