Gel polymer electrolyte comprising a highly concentrated lithium salt/sulfolane electrolyte and partially fluorinated tetra-arm polymer

A gel polymer electrolyte (GPE) with enhanced mechanical strength and a high Li-ion transference number (tLi+) was developed via the crosslinking of tetra-arm poly(2,2,3,3-tetrafluoropropyl acrylate) in a sulfolane-based highly concentrated electrolyte ([Li(SL)3][TFSA]). The high tLi+ (0.64) was attributed to interactions between the fluorinated side-chain protons and TFSA anions. Moreover, rheological analysis indicated a low tan δ. The GPE showed oxidation stability up to 4.5 V and stable Li deposition/dissolution, highlighting its potential for battery applications.