Polyfluorinated Crosslinker-based Solid Polymer Electrolytes for Long-Cycling 4.5 V Lithium Metal Batteries

Abstract Solid polymer electrolytes (SPEs), which are favorable to form intimate interfacial contacts with electrodes, are promising electrolyte of choice for long-cycling lithium metal batteries (LMBs). However, typical SPEs with easily oxidized oxygen-bearing polar groups exhibit narrow electrochemical stability window (ESW), making it impractical to increase specific capacity and energy density of SPE based LMBs with charging cut-off voltage of 4.5 V or higher. Here, a polyfluorinated crosslinker has been applied to enhance oxidation resistance of SPEs via inductive electron-withdrawing effect of polyfluorinated segments transmitted through crosslinked networks. As a result, polyfluorinated crosslinked SPE exhibits a wide ESW, and the Li|SPE|LiNi0.5Co0.2Mn0.3O2 cell with a cutoff voltage of 4.5 V delivers a high discharge specific capacity of ~ 164.19 mAh g− 1 at 0.5 C and capacity retention of ~ 90% after 200 cycles. This work opens a new direction in developing SPEs for long-cycling high-voltage LMBs by using polyfluorinated crosslinking strategy.