The Effect of Silica Addition on the Properties of Poly((vinylidene fluoride)-co-hexafluoropropylene)-Based Polymer Electrolytes

The effect of fumed silica (SiO2) addition on the physical and electrochemical properties of poly((vinylidene fluoride)-co-hexafluoropropylene) based polymer electrolyte was investigated by various methods including morphology observation, thermal and crystallinity evaluations, impregnation test using an electrolyte solution, electrochemical stability analysis and impedance measurement. About 38 wt.-% of silica content proved to be the upper limit at which the silica could be no longer added to obtain a self-sustained polymer electrolyte film. As the silica content increased, a finer pore structure developed, a greater amount of electrolyte solution was absorbed, and thus higher ionic conductivity was shown. The electrochemical stability was preserved up to about 4.5 V for all the polymer electrolytes prepared. The interfacial resistance between the polymer electrolyte and the lithium electrode was reduced with the silica content and also showed a diminishing growth rate with time.