High‐Performance All‐Solid‐State Lithium Metal Batteries: Special Cationic Polymerization Interface Chemistry

Abstract Polyethylene oxide (PEO) based solid polymer electrolytes (SPEs) are severely hindered in their commercialization process due to their room temperature ionic conductivity and unstable electrolyte/electrode interface. Herein, it is reported that a small amount of TiF 4 ionic compound powder is added to the PEO‐based solid electrolyte with Li‐bis(trifluoromethyl)sulfonimide (LiTFSI). The introduction of TiF 4 exhibits special cationic polymerization interface chemistry with LiTFSI and PEO, thus generating more grain boundaries, improving ionic conductivity and Li + migration number, and improving oxidation stability and thermal stability. As a result, an ionic conductivity of 0.22 mS cm −1 is achieved. In the Li‐ LiNi 0.8 Mn 0.1 Co 0.1 O 2 system, when the charging voltage is adjusted to 4.2 V, the battery can still maintain cycling stability at 0.5C. When the mass loading is increased to 15.0 mg cm⁻ 2 , the assembled Li‐LiFeO 4 pouch cell cycles stably for 300 cycles at 0.25C, with a high cycle retention rate of 91.2%. The energy density is 307.3 Wh kg⁻¹. More importantly, solid lithium–sulfur batteries exhibit an initial discharge capacity of 872 mAh g −1 at 0.25C, and after 500 cycles, the decay rate of each cycle is only 0.094%. This work provides a new approach for achieving ultra‐long cycle life for all‐solid‐state lithium metal batteries at room temperature.