In Situ Prepared All-Fluorinated Polymer Electrolyte for Energy-Dense High-Voltage Lithium-Metal Batteries

SUMMARYSolid-state batteries are an emerging technology that delivers significantly higher safety than conventional lithium-ion batteries. However, the energy density of devices still needs to be improved. Herein, a quasi-solid all-fluorinated polymer electrolyte (AFPE) is developed for high-voltage, solid-state, lithium-metal batteries. The AFPE is obtained by polymerizing in situ trifluoroethyl methacrylate in fluorinated ethylene carbonate. The two salts present (LiTFSI and LiDFOB) form LiF- and B-rich solid electrolyte interphases that are highly stable against lithium metal and high-voltage LiCoO2. The corresponding Li|AFPE10|LiCoO2 battery was cycled 500 times at a cut-off voltage of 4.5 V with a 92% capacity retention and 99.82% average Coulombic efficiency. Lithium-metal batteries with high cathode mass loadings up to 25 mg cm−2 and energy densities as high as 546 Wh kg−1 were prepared. This work opens a new avenue of research by developing AFPEs that can be synthesized in situ.