SULFIDE-BASED SOLID ELECTROLYTE AND METHOD FOR REGENERATING THE SULFIDE-BASED SOLID ELECTROLYTE

An electrolyte composition includes a sulfide-based solid electrolyte having a surface layer comprising a phosphorous oxysulfide compound represented by a formula PSO, where x is an integer and y is an integer. The concentration of an oxygen (O) atom in the PSOis at least 15 atomic percent in an X-ray Photoelectron Spectroscopy (XPS) analysis.