High‐Entropy Gel Polymer Electrolyte for Wide‐Temperature Operatable Li‐Metal Batteries

Abstract The practical application of Li‐metal batteries faces the bottlenecks of thermal‐safety hazard, interfacial problems and limited operating‐temperature. The solid electrolyte can overcome the safety hazard, yet the narrow operating‐temperature and unstable electrode/electrolyte interface may not be easily addressed by single‐phase solid electrolyte. Herein, a high‐entropy gel polymer electrolyte with 40 vol% dioxolane precursor (i.e., HEGE (40%PDOL) ) possessing outstanding ionic conductivity (4.42 mS cm −1 at −25 °C) and high cation transport number (0.84) is fabricated through controlled Li + solvation structure and in situ polymerization of dioxolane. The obtained Li|HEGE (40%PDOL) |Li cell shows stable cycling performance over 3000 h at 25 °C. The HEGE (40%PDOL) enables LiNi 0.8 Co 0.1 Mn 0.1 O 2 (active material content >97%, 1.2 mAh cm −2 )||Li coin cell with capacity retention over 75% after 500 cycles at −25 °C and the pouch cell assembled from thin Li (40 µm) with a high capacity retention of 72.5% after 400 cycles. Based on the molecular dynamic simulation, the solvation structure‐related model revealing the relationship between system diversity and Li + transport efficiency is established, providing physical insight for the excellent electrochemical performance of HEGE (40%PDOL) . Such high‐entropy electrolyte realizes the coexistence of safety, stable cycling, and wide operating‐temperature, providing a new step for solid‐state batteries.