A Flexible Solid Polymer Electrolyte based Polymerized Ionic Liquid for High Performance Solid‐State Batteries

Abstract Solid polymer electrolytes (SPEs) combine the benefits of ceramic electrolyte and polymer electrolyte, and have broad application prospects in high‐energy lithium metal batteries. However, low Li⁺ conductivity and tensile strength are crucial elements that hinder the application of solid polymer electrolytes. In this paper, an effective solid polymer electrolyte was proposed to solve these problems. A polymerized ionic liquid (PIL) was chosen as the ionic transport material to synthesize three‐dimensional cross‐linked ion channels through thermal polymerization, which can effectively improve the ionic conductivity. This work is different from some other reports that add ionic liquid without C=C double bond. We used the vinyl ionic liquid (IL) as matrix via polymerization with azobis initiator (AIBN) and the obtained co‐polymer has excellent flexibility and non‐flowing character. Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (LLZTO) ceramic filler was added to enhance the thermal stability and tensile strength of the electrolyte. Meanwhile, solid‐state batteries (SSBs) assembled with LiFePO₄ cathode and high‐voltage LiNi_0.8Co_0.1Mn_0.1O₂ cathode can deliver remarkable cell performance. This work presents an appropriate device for the structure of modern polymerized ionic liquid solid polymer electrolytes, and shows significant implication for the progress of high‐property polymer electrolytes.