Li metal stability enhancement of Sn-doped Li₂S-P₂S₅ glass-ceramics electrolyte

All-solid-state lithium ion batteries (ASSLIBs) are very promising next-generation lithium ion batteries with high energy density and safety. Among the solid electrolytes that can be applied to ASSLIBs, sulfide glass-ceramics electrolytes are attracting attention because of their high ionic conductivity and good mechanical deformability. However, the lack of the chemical and electrochemical stability of the sulfide electrolytes under prolonged cycle operation has become a barrier limiting their practical use and commercialization. We investigated the effects of Sn substitution on the electrochemical and chemical stability enhancement of Li₂S-P₂S₅ glass-ceramics electrolytes. Also, we analyzed the cause of the degradation by side reactions and lithium dendrite growth. For 80Li₂S-15P₂S₅-10SnS₂ glass-ceramics electrolyte, only the redox current of the lithium deposition/dissolution was observed in cyclic voltammetry test with lithium metal. And the result of X-ray photoelectron spectroscopy analysis demonstrated a reduction in the amount of Li₂S and decomposition product from the sulfide solid electrolytes. ASSLIBs using 80Li₂S-15P₂S₅-10SnS₂ as solid electrolytes with Li metal or Li-In anodes showed improved cycling performance compared to batteries employing 80Li₂S-20P₂S₅ glass-ceramics. These results showed that Sn substitution is effective to improve the chemical and electrochemical stability of Li₂S-P₂S₅ glass-ceramics electrolyte to lithium metal.