Moisture Exposure as Pretreatment of Sulfide Solid Electrolytes for All-Solid-State Batteries

Sulfide all-solid-state batteries have been actively studied for practical use in vehicle applications. Modifications are often required at the interface between the sulfide solid electrolyte and oxide cathode active material. Scholars have reported that only the surface of the sulfide solid electrolyte is degraded by moisture exposure at a dew point equal to that of a dry room for common lithium-ion battery fabrication and that the surface-degraded material contains lithium carbonate and other lithium salts. Additionally, researchers have reported that lithium salts including lithium carbonate are effective for surface modification of cathode active materials. This paper reports how lithium carbonate is formed by the reaction of a carbon-free solid electrolyte with carbon-free water and that degraded surface of sulfide solid electrolyte by exposure to moisture acts as an effective modifying layer at the interface between the active material and solid electrolyte for all-solid-state batteries.