High Ion Conducting Solid Composite Electrolytes with Enhanced Interfacial Compatibility for Lithium Metal Batteries

Abstract The utilization of lithium metal anodes is crucial for further advancement of the energy density of lithium batteries. Solid electrolytes with high ionic conductivity at ambient temperature and good mechanical strength are key to realizing the large‐scale application of solid‐state lithium‐metal batteries. In particular, the formation of a homogeneous and stable solid‐electrolyte interphase is crucial for improving the safety and coulombic efficiency of lithium‐metal batteries. Herein, a solid composite electrolyte design based on a cyclic carbonate‐cyclic ether copolymer is exploited. The cyclic carbonate segments in the solid composite electrolyte provide high mechanical integrity, whereas the cyclic ether groups promote the dissociation of lithium salts and the formation of a stable solid‐electrolyte interphase. Thus, the solid composite electrolyte exhibits a high ionic conductivity of 1.58×10 −4 S cm −1 and a high lithium transference number of 0.55 at room temperature. Furthermore, optimization of the solid‐electrolyte interphase composition and the inhibition of lithium dendrites are demonstrated. Most importantly, excellent rate capability and cycling stability at room temperature and below (10 °C) are achieved in solid‐state lithium‐metal batteries with the solid composite electrolyte.