Fast and stable charge transfer at the lithium-sulfide (electrolyte) interface via an in situ solidified Li⁺-conductive interlayer

With high Li⁺ conductivity and mechanical plasticity, sulfide electrolytes such as glassy 75Li₂S-25P₂S₅ (LPS) have become promising solid electrolytes for building rechargeable lithium-metal batteries. However, sulfide electrolytes usually show unstable interfacial electrochemistry versus Li metal, which could cause parasitic reactions and dendrite formation, thus leading to rapid performance fading and battery failure. In this work, we show that, by applying a LiF-rich in situ solidified Li⁺-conductive interlayer (LCI), the interfacial contact and charge transfer stability between LPS and Li metal are notably improved, which leads to inhibition of electrolyte decomposition and dendrite-free Li plating/stripping at the interface. At room temperature, Li-Li symmetric cells assembled from LCI-modified LPS electrolyte demonstrate stable cycling performance for over 1500 hours at 0.1 mA cm⁻², and a high critical current density of up to 5 mA cm⁻². This work sheds light on the rational design of the Li-sulfide interface towards practical realization of high-energy solid-state batteries.