Absorption ability and kinetics of a liquid electrolyte in PVDF–HFP copolymer containing or not SiO2

Gel polymer electrolytes have been prepared from PVDF–HFP copolymer with various silica contents incorporating Gamma valerolactone (VL) or VL/EC (80/20 in mole) (EC: ethylene carbonate) solutions of lithium bis(trifluoromethane sulfone) imide (LiTFSI). The influence of temperature, salt content and silica addition on the kinetics of absorption and wettability of the copolymer has been investigated. An empirical model, taking into account gel swelling during the absorption allows us to relate, at constant temperature, the wetting time and the volumetric fraction of trapped electrolyte, which is a critical factor for ionic conductivity of the gel. Increasing the silica content in the dry copolymer increases the porosity and consequently the rate of absorption and thus the amount of incorporated liquid phase at saturation. To a lower extent, an increase in the temperature of absorption has the same effects. The prepared gels have good mechanicals properties and conductivities. As an example, a gel of composition:imagePVDF–HFP/SiO2/VL/EC/LiTFSIofmolarpercentages 36/6.7/42/10.5/4.8 exhibitsaconductivityof2.9mScm−1 at293K.