Interfacial modification between argyrodite-type solid-state electrolytes and Li metal anodes using LiPON interlayers

Abstract

Solid-state batteries (SSBs) using lithium (Li) metal anodes and solid-state electrolytes (SSEs) can offer both improved energy densities and, by removing flammable liquid electrolytes, improved safety. The argyrodite-type Li₆PS₅Cl ceramic is an attractive candidate SSE material because of its high ionic conductivity (>1 mS cm⁻¹) at room temperature and relatively ductile mechanical properties. However, interface contact issues between the SSE and Li metal hamper the practical development of solid-state Li metal batteries. In this work, we show that the interfacial resistance between the Li₆PS₅Cl SSE and Li metal anode can be reduced to as low as 1.3 Ω cm² in symmetric cells by introducing a thin amorphous and Li-ion conducting lithium phosphorus oxynitride (LiPON) interlayer. We demonstrate that this interlayer improves the wetting behaviour of the Li₆PS₅Cl SSE, and helps form an effective conformal interfacial contact between the Li₆PS₅Cl SSE and Li metal. LiPON coated Li₆PS₅Cl symmetric cells with reduced interfacial resistance exhibit stable Li plating/stripping cycling for over 1000 h at 0.5 mA cm⁻², and a dramatically improved critical current density of 4.1 mA cm⁻² at 30 °C. These results demonstrate a reliable thin-film coating strategy for improving contact between the SSEs and Li metal anodes, stabilizing interfaces and realizing the practical application of solid-state Li metal batteries.