We evaluated and compared the physical properties of electrolyte solutions consisting of lithium bis(fluorosulfonyl)amide and sulfone solvents (molar ratio = 1 : 3) and their mixtures containing aluminum oxide (α-Al₂O₃) or lithium lanthanum zirconate (LLZ) particles of various particle sizes. Sulfolane (SL), 3-methylsulfolane, and ethyl isopropyl sulfone were evaluated as sulfone solvents for the electrolyte solutions. The phase-change heat, phase-change temperature, and spin–spin relaxation time in nuclear magnetic resonance (NMR) measurements decrease in a mixture of SL electrolyte with a metal oxide, with an apparent average liquid thickness in the order of nm resulting from the SL electrolyte solution. This indicates a decrease in molecular mobility around the particle surface. For the α-Al₂O₃ system, no substantial changes are observed in the activation energy of ionic conductivity, self-diffusion coefficient of Li⁺ (determined via pulsed-field gradient NMR), or relative cross-peak intensities of Li⁺ and ¹H of SL in the two-dimensional NMR of the mixture. Therefore, despite its low molecular mobility, the SL electrolyte solution at the solid–liquid interface is considered to exhibit an ionic conductivity mechanism similar to that of the bulk electrolyte. It was suggested that LLZ system has a different ionic conduction mechanism than α-Al₂O₃ system.

For lithium-sulfur (Li-S) batteries, high-concentration electrolyte that inhibits the dissolution of Li polysulfide has been widely studied; one such electrolyte contains sulfolane. This study investigates the conditions under which a microporous activated carbon cathode, derived from azurmic acid, operates stably in a sulfolane-based electrolyte. We expected this cathode to maintain a stable capacity in a sulfolane-based electrolyte because its micropores stabilize the S species. However, Li-S batteries containing this cathode and electrolyte exhibit significant capacity decay during cycling. The cutoff voltage during charge-discharge cycling is varied to suppress the capacity decay. At a discharge voltage of 1.4 V or lower, the cycle life of the Li-S batteries is significantly reduced. Conversely, increasing the cutoff voltage during discharge suppresses the capacity decay of Li-S batteries. On the other hand, increasing the upper voltage limit during charging increases the reversible capacity. Thus, the operating voltage range is optimized. This study indicates that the voltage range of Li-S batteries should be carefully determined depending on the type of cathode material and electrolyte.

We have been developing sintered multilayer oxide-based all-solid-state batteries. Anode active material rutile-type TiO₂ was not reacted with amorphous Na superionic conductor (NASICON)-type solid electrolyte Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP) even after sintered at 600 °C in a nitrogen atmosphere from the XRD patterns. The charge/discharge behavior of the electrochemical measuring cell (when using a non-aqueous electrolyte) was not different from that of rutile-type TiO₂. However, anatase-type TiO₂ charge/discharge behavior changed after sintering process. Additionally, in the result of the input/output characteristics using multilayer oxide-based all-solid-state battery, rutile-type TiO₂ as anode material was 3 times higher discharge capacity than anatase-type TiO₂ at current value 25.6 µA mm⁻². Finally, we successfully measured the Raman spectroscopy of all-solid-battery and rutile-type TiO₂ Raman shift peaks were reversibility during charge/discharge. Based on these findings, we conclude that rutile-type TiO₂ maintained a strong crystalline structure and high Li diffusivity even when sintered with amorphous LAGP. It suggested that rutile-type TiO₂ is suitable as anode material for oxide-based all-solid-state batteries requiring the sintering process.

Accurate battery state of health (SOH) assessment is one of the keys to the safe and stable operation of battery systems. A novel fast SOH evaluation method for lithium-ion battery modules is proposed based on Lorenz plot (LP). The average Lorenz radius (ALR) of a module in a certain SOC interval is extracted as a health factor for this module SOH. The research results show that the ALR value of the module gradually increases in the low SOC range of the charging curve or the discharge curve as the battery module ages. When the ALR values at 20 % SOC are extracted as health factors, the ALR-SOH evaluation models present a linear negative correlation with a goodness of fit of over 0.99. When the voltage data from any SOC interval containing a voltage of 20 % SOC are extracted to calculate the ALR values of the module, the accuracy of the ALR-SOH evaluation models based on the discharge voltage is generally better than that based on the charging voltage. When the ALR values of the module are calculated using voltage data from any SOC interval starting from 10 % SOC during discharge, the goodness of fit of the ALR-SOH evaluation models based on the discharge voltage data is above 0.97, suggesting the robustness of the SOH evaluation method based on LP. This will provide ample options for the practical application of this method.

The Ni-Al layered double hydroxide materials with high crystallinity were synthesized by the room-temperature liquid process and applied as oxygen evolution reaction (OER) catalysts. It is interesting to note that the OER activity was found to be relatively high in comparison with the Ni-based materials. In addition, the structural analyses and the effects of interlayer anion specie on the OER activity were also evaluated. It was found that the changes in the interlayer anion species from F⁻ to OH⁻ resulted in the enhancement of the OER activity. The maintained chemical compositions and crystallinity after the electrochemical measurements were also observed through the X-ray analyses. The present work provides the insights about the possibility of the well-defined structures as the electrodes which were prepared by the unique liquid phase process.