Electrospun Poly(vinylidene fluoride)-Lithium Bistrifluoromethanesulfonamide Separators for Applications in Ionic Liquid Batteries

In batteries the separator plays a crucial role within the cell. Commercially available separators, e.g. polyolefins, glass fibres, or polyolefins with ceramic coatings, do not have ideal compatibility with ionic liquid (IL) electrolytes. In this study, we report on the use of electrospinning to fabricate poly(vinylidene fluoride) (PVDF) membranes for use with IL electrolyte based batteries. Four electrospun membranes have been prepared; a neat PVDF, PVDF doped with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), and two LiTFSI-doped membranes based on either thermal or UV cross-linking. The membranes were characterised by a number of techniques and the key characteristics of all electrospun membranes included small fibre sizes and high porosity. The tensile strengths of the cross-linked membranes approached those of commercial membranes. Electrochemical performance was measured using coin cell cycling and the thermally cross-linked membrane gave the lowest cell overpotential as well as the lowest cell resistance.