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