Non-Flammable fluorinated gel polymer electrolyte for safe lithium metal batteries in harsh environments

Abstract

Compared to liquid electrolytes, gel polymer electrolytes (GPEs) offer enhanced safety and represent an up-and-coming option for high-energy–density lithium metal batteries (LMBs). However, several challenges hindered the practical application of GPEs for LMBs, such as low ionic conductivity at room temperature, decomposition at high voltage, and poor interfacial compatibility with lithium anode. In this study, a non-flammable fluorinated GPE was synthesized using 2,2,2-trifluoroethyl acrylate (TFEA) and ethoxylated trimethylolpropane triacrylate (ETPTA) as precursor materials, with succinonitrile (SN) incorporated as a plasticizer and a dual-salt system of lithium bis(trifluoro-methane) sulfonimide and lithium difluoroxalate borate. Notably, the as-prepared GPE exhibits a high ionic conductivity of 1.33 mS cm⁻¹ at 30 °C, an electrochemical stability window of 5.15 V (vs. Li⁺/Li), and excellent interfacial compatibility with the high-nickel LiNi_0.93Co_0.035Mn_0.035O₂ (NCM-93) cathode and lithium metal anode. Consequently, the Li|NCM-93 cells demonstrated outstanding cycling stability at a cutoff voltage of 4.3 V at room temperature as well as exceptional safety performances under high-temperature conditions and intense radiation conditions. Furthermore, the fluorinated GPE effectively suppresses the gas generation from high-nickel cathode materials and inhibits the growth of lithium dendrites on the anode. This work offers a novel avenue for developing safe and high-voltage solid-state LMBs for working in harsh environments.