Investigation on the effect of LiTFSI salt on PVDF-based Solid Polymer Electrolyte Membranes for Lithium-Ion Batteries

Solid polymer electrolytes provide an alternative approach to providing improved safety whilst concurrently acting as a performance enhanced separator within Lithium-ion batteries (LIBs). This investigation studies the effects of Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salts in a polymer blend with Polyvinylidene fluoride (PVDF) and Poly (vinylpyrrolidone) (PvP) or Poly (4-vinylpyridine) (P4VP) on the performance of SPE membranes. Characterization by X-ray diffraction and Fourier-transform infrared spectroscopy highlights the changes due to LiTFSI, specifically amorphization. Performance studies with increasing LiTFSI showed improved thermal stability and the inhibition of PVDF endotherms on differential scanning calorimetry (DSC) profiles. The drawbacks of increased LiTFSI content were evident on the mechanical performance with decreased thresholds on the tensile strength. Inversely, improvements on the dielectric performance and conductivity were observed with excellent workability from a wide electrochemical stability window of 0.5 to 3.64 V vs. Li+/Li. Additionally, the incorporation of metal-fillers; Aluminum Oxide, Zirconia Oxide and Silicon Oxide was similarly studied.