In Situ Li₃ PS₄ Solid-State Electrolyte Protection Layers for Superior Long-Life and High-Rate Lithium-Metal Anodes

A thin and adjustable Li₃ PS₄ (LPS) solid-state electrolyte protection layer on the surface of Li is proposed to address the dynamic plating/stripping process of Li metal. The LPS interlayer is formed by an in situ and self-limiting reaction between P₄ S₁₆ and Li in N-methyl-2-pyrrolidone. By increasing the concentration of P₄ S₁₆ , the thickness of the LPS layer can be adjusted up to 60 nm. Due to the high ionic conductivity and low electrochemical activity of Li₃ PS₄ , the intimate protection layer of LPS can not only prevent the formation of Li dendrites, but also reduces parasitic side reactions and improves the electrochemical performance. As a result, symmetric cells with the LPS protection layer can deliver stable Li plating/stripping for 2000 h. Full cells assembled with the LPS-protected Li exhibit two times higher capacity retention in Li-S batteries (≈800 mAh g^-1 ) at 5 A g^-1 for over 400 cycles compared to their bare Li counterparts. Furthermore, high rate performances can be achieved with Li-LPS/LiCoO₂ cells, which are capable of cycling at rates as high as 20 C. This innovative and scalable approach to stabilizing the Li anode can serve as a basis for the development of next-generation high-performance lithium-metal batteries.