Janus Electrolyte with Modified Li+ Solvation for High‐Performance Solid‐State Lithium Batteries

Abstract Solid‐state lithium‐metal batteries attract great attention due to their high energy density and superior safety. However, the sluggish Li+ kinetics of solid electrolyte and poor interface compatibility between electrolyte and lithium anode lead to unsatisfied performance at room temperature, which severely limit their practical application. Herein, a Janus quasi‐solid electrolyte (JSE) design is reported, which modifies the Li+ solvation environment in succinonitrile (SN) plastic crystal electrolyte and creates 1D Li+ transportation channels. Density functional theory calculations and Raman results reveal that Li1.3Al0.3Ti1.7(PO4)3 changes the Li+ solvation environment from SN units to aggregated ion pairs, which accelerates the diffusion rate of Li+. As a result, JSE presents excellent ionic conductivity (0.73 mS cm−1) and high lithium transference number (0.72). With this efficient JSE, Li symmetric cells deliver excellent cycle stability over 600 h with a low over potential of 60 mV. LiFePO4|JSE|Li solid‐state battery delivers an impressive performance with a specific discharge capacity of 152 mAh g−1 after 100 cycles at room temperature under 0.5 C. Moreover, the corresponding pouch cell also shows outstanding performance (140 mAh g−1 under 0.5 C) and withstands abuse tests such as bending and cutting, demonstrating its superior safety for future utilization.