Preparation and properties of cross-linked poly(ethylene glycol)/poly[(vinylidene fluoride)-co-hexafluoropropylene] interpenetrating network-type electrolytes for secondary lithium batteries

Cross-linked poly(ethylene glycol)/poly[(vinylidene fluoride)-co-hexafluoropropylene] (XPEG/PVDF-HFP) gel-type polymer electrolyte interpenetrating polymer networks (IPNs) were prepared by cross-linking the PEG molecules in the presence of PVDF-HFP molecules. Thermal, mechanical, swelling and electrochemical properties, as well as microstructures of the prepared polymer electrolytes, were investigated for various polymer compositions. The mechanical strength increased, but the swelling ratio in electrolyte solution decreased with increasing PVDF-HFP content. The ion conductivity was highly affected by the type of electrolyte salt, and increased with increasing XPEG concentration. The Arrhenius-type relationship was observed in the temperature dependence of ion conductivity. The polymer electrolyte systems prepared in this study were electrochemically stable up to about 5 V.