Impact of Surface Coating on the Low Temperature Performance of a Sulfide-Based All-Solid-State Battery Cathode

Cathode coating is a key technology in sulfide-based all-solid-state batteries (ASSBs). The coating serves as a protector, suppressing side reactions at the sulfide/cathode active material interface. Lithium niobate (LiNbO3) is a well-known coating material. In this study, sulfide-based ASSBs, which were uncoated and surface-coated with LiNbO3, are subjected to cell operation testing and electrochemical impedance spectroscopy (EIS) in a low-temperature environment (i.e., −60 °C), where a commercial liquid-type lithium-ion battery (LIB) is unable to operate because of partial freezing and significant viscosity increase. Unlike liquid-type LIBs, the coated and uncoated ASSBs successfully discharge at −60 °C, emphasizing their applicability in low-temperature environments. The coated ASSB exhibits better low-temperature performance than the uncoated one. In the absence of coating, the deconvoluted EIS resistance data show an increase in some resistance components at low temperature.