In Situ Polymerization of Fluorinated Polyacrylate Copolymer Solid Electrolytes for High-Voltage Lithium Metal Batteries at Room Temperature

Poly(ethylene oxide) is a promising solid polymer electrolyte (SPE) matrix. However, its low ionic conductivity, narrow electrochemical window, and sluggish interfacial charge transfer limit its use in solid-state batteries at room temperature. Herein, we report the in situ polymerization of poly(2,2,3,4,4,4-hexafluorobutyl acrylate-copolymer-2-(2-(2-methoxyethoxy) ethoxy)ethyl acrylate) (P(HFBA-co-MEA)) with lithium bis(trifluoromethane sulfonamide) (LiTFSI) to form a fluorinated SPE (P(HFBA-co-MEA)/LiTFSI). When the molar ratio of HFBA to MEA is 1:1, P(HFBA1:1-co-MEA) exhibits a lower lithium-ion absorption energy (−4.602 eV) than that of PMEA (−4.372 eV), providing a fast transport pathway for lithium ions. The electron-absorbing properties of the −C–F group can reduce the lone-pair electron density around the ether-oxygen group and increase the electrochemical window of P(HFBA1:1-co-MEA)/LiTFSI to 4.9 V. In addition, P(HFBA1:1-co-MEA)/LiTFSI demonstrates excellent compatibility with lithium anodes, and the Li|P(HFBA1:1-co-MEA)/LiTFSI|LiNi0.5Co0.3Mn0.2O2 battery has a capacity retention of 62.3% after 170 charge–discharge cycles at 0.1C.