Study of Solvent Effect on PVDF-HFP Gel Polymer Electrolyte Containing Ionic Liquid Pyr_1,4TFSI for Lithium Batteries...

The development of polymer electrolytes is a promising strategy for increasing the safety and performance of lithium batteries. In particular, gel polymer electrolytes (GPEs) are closest to replacing conventional liquid electrolytes due to their properties from the incorporation of plasticizers and conductors into polymers. One family of these compounds, ionic liquids (IL), has the ideal range of properties for reducing the risk of fire, leaks, and toxic by-products. In this work, poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) copolymer was used to synthesize a GPE with lithium salt and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (IL), evaluating the effect of different solvents on the final properties of the material, such as thermal stability, crystallinity, microstructure and conductivity. The addition of IL was responsible for a reduction in the crystallinity of PVDF-HFP from an average of 31% to 11%, and a diminution in its thermal stability (T_2%) from 435°C to 350°C. Membrane microstructure was dependent on the solvent used, ranging from completely uniform with acetone to granular with dimethylformamide or dimethylacetamide. The dimethylacetamide electrolyte had the highest conductivity (0.43 mS cm^-1), while the N-methylpyrrolidone electrolyte showed better interaction with metallic lithium.