2단계 자외선 가교가 PEO 고체 전해질막의 결정화도와 리튬이온 전도도에 미치는 영향

초록

Dual photo-crosslinking of PEO film was applied to enhance the ionic conductivity of the solid polymer electrolytes (SPEs) through the decreased crystallinity by the solution crosslinking and subsequent solid crosslinking. The UV irradiation energy, the concentration of photoinitiators and lithium salts were adjusted to optimize the SPE crosslinking. In particular, the PEO films containing LiPF6 or LiTFSI were cast via a solution process using acetonitrile as a solvent, both polymer films and polymer solutions were crosslinked under 365 nm LED-UV irradiation. The tensile toughness of the crosslinked SPE containing LiPF6 increased nearly seven folds from 0.5 GPa up to 3.4 GPa. Also XRD crystallinity of the dual-crosslinked SPE decreased from 71% up to 10% surprisingly. Maximum ionic conductivity of 1.1×10-3 mS/cm at 25 °C was obtained by dual crosslinking of SPE containing LiTFSI at an EO:Li ratio of 10:1. The SPEs also exhibited similar ionic conductivity to the gel polymer electrolyte containing 100 wt% liquid electrolyte. These findings support the dual-crosslinking as a viable route for the development of high-performance SPEs with superior mechanical strength.

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