A Solvent-Induced Solid Polymer Electrolyte with Controllable Polymerization for Low-Temperature Lithium Metal Batteries

Abstract

Solid-state electrolytes based on in situ ring-opening polymerization of 1,3-dioxolane (DOL) have attracted widespread attention in Li metal batteries because of their high interface compatibility. However, its conventional cationic polymerization mechanism frequently results in the formation of long polymer chains during in situ polymerization, thereby impeding Li⁺ transport. Here, we regulate the ring opening polymerization of DOL by introducing N,N-dimethyltrifluoroacetamide (FDMA), thus avoiding the formation of long polymer chains. Meanwhile, FDMA can derive a stable SEI rich in LiF during electrochemical cycling, improving interface stability and suppressing dendritic Li growth. Therefore, the full battery with LiFePO₄ as the cathode can achieve a high capacity retention rate of 83.9% after 400 cycles at a rate of 5.0 C. At −20 °C, the Li∥LiFePO₄ full battery can provide a high capacity of 137 mAh g^–1. The solvent-induced strategy provides a promising new avenue for designing a solid electrolyte with high temperature resistance.