Superior polymer backbone with poly(arylene ether) over polyamide for single ion conducting polymer electrolytes

Effect of polyamide and poly(arylene ether) as backbones of bis(benzene sulfonyl)imide for single ion conducting polymer electrolytes on mechanical and electrochemical properties and device performance was investigated. Alternating copolymerization between 4,4′-fluorine bis(benzene sulfonyl)imide and 4,4′-dihydroxydiphenyl ether produced a poly(arylene ether) based polymer (LiPHFE). For comparison, 4,4′-dicarboxyl bis(benzene sulfonyl)imide was used to copolymerize with 4,4′-diaminodiphenyl ether to form a polyamide based polymer (LiPACA). Thermal stability, morphology, mechanical strength, electrochemical stability and battery performance were carefully measured. We conclude that the LiPHFE blend film is superior to the LiPACA blend film. Half-cells using LiFePO4 (LFP) and Li4Ti5O12 (LTO) incorporating the LiPHFE film as the electrolyte as well as the separator were tested separately at 1 C for 800 cycles. No obvious performance decay was observed, demonstrating exceptional device compatibility and stability. Finally, a full cell with the configuration of “LTO | LiPHFE | LFP” was assembled and subsequently tested at 0.5 C for 100 cycles. The device is capable of delivering a stable discharge capacity of 96 mAh g−1 normalized to the mass of LFP with the coulombic efficiency of 100%. This work paves a way for design of more robust single ion conducting polymer electrolytes to enable batteries to be operative with long cycle life and superior device safety.