Reducing Interfacial Resistance between Solid and Liquid Electrolytes through Wet Polishing for Quasi-Solid Batteries

Abstract High interfacial resistance between a garnet-type solid electrolyte (lithium lanthanum zirconium oxide, LLZO) and a liquid electrolyte limits quasi-solid battery performance. Here, we demonstrate that wet-polishing LLZO in a nonaqueous Li salt solution drastically reduces the solid-liquid interfacial resistance by simultaneously removing surface impurities and forming a protective layer. Surface and electrochemical analyses reveal that the protective layer is thin and Li+-conductive, significantly enhancing Li+ transport at the solid/liquid interface. This approach enables effective utilization of Li+ conduction in LLZO for quasi-solid batteries, offering a promising strategy for next-generation energy storage systems.