Physically crosslinked gel electrolytes based on a self-assembling ABA triblock copolymer

Gel electrolytes were prepared by swelling a self-assembling ABA triblock copolymer with different amounts of a solution of 1 M lithium bis(trifluoromethylsulfonyl)imide salt in γ-butyrolactone. The triblock copolymer had endblocks of polyethylene (PE) and midblocks of poly(ethylene oxide-co-propylene oxide) (PEOPO), where the former blocks constituted 10 wt% of the copolymer. Thus, the electrolyte solution was contained in physical networks consisting of PEOPO chains interconnected by crystalline PE phase domains. The gels showed a stepwise increase in the ionic conductivity as a consequence of the melting of the PE domains at approximately 100 °C. Also, the conductivity at room temperature increased significantly after annealing above this temperature. Block copolymer gels containing 70 wt% of electrolyte solution reached conductivities of 1 mS/cm at 20 °C.