Ethylene oxide–based polymer electrolytes with fluoroalkyl moieties for stable lithium metal batteries

In this study, we have developed a new ethylene oxide (EO)-based polymer electrolyte (PE) that contains fluoroalkyl moieties. The developed PE possesses high oxidative decomposition potential as well as adequate ionic conductivity ( σ ) and favorable mechanical properties for application to Li metal batteries. In particular, we designed a partially fluorinated copolymer, which is improved in conventional polyethylene oxide systems and could be used both as stable electrolyte matrix and electrode binder for high-voltage applications. The results indicated that the stabilization of the EO-based PE during the high-voltage operation of Li metal batteries was significantly improved by the introduction of a fluoroalkyl moiety via simple radical copolymerization. The synthesized copolymer exhibited satisfactory physical stability and unprecedented high oxidation decomposition voltage threshold, which exceeded 4.5 V. Moreover, the copolymer-based PEs presented moderate σ values (> 0.3 mS cm −1 at 60 °C) and retained the intrinsic properties of the EO-based PE.