Development of all-solid-state lithium-ion batteries (ASSLBs) has rapidly progressed in the recent years. In the case of sulfide-based ASSLBs, interfacial reaction between the cathode material and solid electrolyte is considered as a major reason for the decrease in capacity, while surface coating of the cathode material is employed to mitigate the interfacial reaction. In SOLiD-EV project, we established a new coating process reducing the time for coating, and also developed a new coating material being more chemically stable at high electric potentials and high temperatures than LiNbO₃, which is one of the most representative coating materials. In addition, the thicker new coating-layer can further improve the battery durability.

The magnetite-silica (Fe₃O₄-SiO₂) composites with high magnetite contents for microwave heating elements were fabricated by the non-firing solidification method. Although the obtained solidified composite had a relative density of 47-57% and was not a dense body, it had sufficient mechanical strength due to the solidification of the silica phase. The magnetite in the composite functions as the microwave heating phase, and the SiO₂ phase and pore phase function as the microwave permeable phase, resulting in a structure that allows uniform heating to reach the inside of the composite structure. It was clarified that the solidified composite could generate heat up to about 500°C without oxidizing during the microwave heating process.

Securing safe water remains an important global issue. PoU (Point of Use) water purification technology using filter media is promising for treating contaminated water in areas where infrastructure development is difficult. In this study, fabrication of a porous hydroxyapatite (HAp) bulk body with a connected pore structure was attempted as a filter that has the function of purifying water contaminated with microorganisms. HAp exhibits high adsorption properties for various substances such as proteins, bacteria, and viruses. In order to introduce a continuous pore structure into the porous body, corn starch, a polysaccharide, was used as a pore-forming agent. Three-dimensional observation of the internal structure of the porous body using a confocal laser fluorescent microscope and liquid immersion technique revealed a shell-like pore structure derived from the starch and the continuous pore structure inside the porous material. A filtration test of a buffer solution containing Escherichia coli (E. coli) was conducted and the filtrate did not contain detectable concentrations of E. coli. A high virus removal rate was demonstrated in a filtration test of a buffer solution containing human coronavirus. It was demonstrated that hydroxyapatite porous materials have excellent properties for filter applications to purify water contaminated with bacteria and viruses.

This study investigated the viability of Hf and/or W doping in Li₇La₃Zr₂O₁₂ (LLZO) through an alkoxide derived sol-gel process aimed at stabilizing the ion-conductive cubic garnet phase. Results revealed that Hf doping tends to favor the tetragonal garnet phase, while co-doping with Hf and W effectively stabilizes the cubic garnet structure. This stabilization is attributed to the similar ionic radii of Hf⁴⁺ (0.71 Å) and the slightly smaller W⁶⁺ (0.62 Å) compared to Zr⁴⁺ (0.72 Å), considering charge neutrality. In both doping scenarios, a coexisting Li-deficient pyrochlore phase is observed, likely due to the use of HfCl₄ and WCl₆ as starting reagents in the alkoxide process, which results in reduced Li-coordinated carboxyl sites attached to chelated Zr alkoxide. However, increasing the Li excess content above 30% effectively eliminates the pyrochlore phase, thus stabilizing the cubic garnet phase. Impedance measurements conducted on Hf-doped LLZO and Hf,W co-doped LLZO (with 40% excess Li) sintered ceramics reveal a significant enhancement in bulk ion conductivity, with the Hf,W co-doped LLZO pellet exhibiting two orders of magnitude higher conductivity (1.09 × 10⁻⁴ S cm⁻¹). This finding confirms the stability of the cubic phase even with partial substitution of W and with 40% excess Li.