Interfacial Chemistry Enables Stable Cycling of All-Solid-State Li Metal Batteries at High Current Densities.

The application of flexible, robust, and low-cost solid polymer electrolytes in next-generation all-solid-state lithium metal batteries has been hindered by the low room-temperature ionic conductivity of these electrolytes and the small critical current density of the batteries. Both issues stem from the low mobility of Li ions in the polymer and the fast lithium dendrite growth at the Li metal/electrolyte interface. Herein, Mg(ClO) is demonstrated to be an effective additive in the poly(ethylene oxide) (PEO)-based composite electrolyte to regulate Li ion transport and manipulate the Li metal/electrolyte interfacial performance. By combining experimental and computational studies, we show that Mg ions are immobile in a PEO host due to coordination with ether oxygen and anions of lithium salts, which enhances the mobility of Li ions; more importantly, an - formed Li-conducting LiMgCl/LiF interfacial layer homogenizes the Li flux during plating and increases the critical current density up to a record 2 mA cm. Each of these factors contributes to the assembly of competitive all-solid-state Li/Li, LiFePO/Li, and LiNiMnCoO/Li cells, demonstrating the importance of surface chemistry and interfacial engineering in the design of all-solid-state Li metal batteries for high-current-density applications.