In-situ polymerized fluorinated polyurethane-based gel polymer electrolyte for high-stability lithium metal batteries

Abstract

A fluorinated polyurethane-based gel polymer electrolyte (GPE) with flame-retardant properties and high interfacial stability for lithium metal batteries (LMBs) is developed by in-situ polymerization of polycaprolactriol, dicyclohexylmethane diisocyanate, and a fluorinated chain extender (octafluoro-1,6-hexanediol) in carbonate-based electrolyte. This GPE exhibits ionic conductivity of 2.78 × 10 −3 S cm −1 , oxidative stability up to 4.75 V, and a lithium ion transference number of 0.54. The introduction of fluorinated segments promotes the formation of a LiF-rich solid electrolyte interphase (SEI) on the lithium anode, effectively suppressing lithium dendrite growth. The gel polymer electrolyte enables stable cycling of Li/Li symmetric cell for over 500 h at 1 mA cm −2 . Moreover, the Li/LiFePO 4 cell achieves a capacity retention of 87.85% after 600 cycles at 2C, and Li/NCM811 cell maintains 76% capacity retention after 150 cycles at 0.5C. Furthermore, this GPE also exhibits good flame retardancy, indicating that this fluorinated polyurethane-based GPEs offer promising prospects for the application of LMBs with enhanced safety.