High-Energy Metallic Lithium Batteries Enabled by Polymer-in-Salt Electrolytes of Cyclic Carbonate Substituted Polyethers

A class of polymer-in-salt electrolytes (PISEs) based on cross-linkable polyethers bearing pendant cyclic carbonate groups has been developed. This type of cyclic carbonate substituted polyether has a low glass transition temperature and shows good chemical and electrochemical stability. We have revealed the effects of the spacer length and the backbone on the ion conduction in detail. The PISE with a moderate interaction between polymer segments and lithium ions exhibits a higher ionic conductivity, and a nearly 3-fold increase in lithium ion transference number compared to that of conventional salt-in-polymer electrolytes. With a high concentration of salt, the growth of dendrites from the lithium–metal anode can be effectively suppressed and a uniform lithium deposition has been observed, which has been related to the formation of the inorganic-rich solid electrolyte interphase. Moreover, the in situ cross-linking of the PISE gives rise to a flexible yet mechanically robust elastomeric thin film with a fast lithium ion conduction, which eventually enables the good-performance all-solid-state Li/LiFePO4 batteries with high cycling stability and Coulombic efficiency at ambient conditions. This work is anticipated to advance the research of PISEs for potential applications in high-energy lithium metal batteries.