Enhanced Electrochemical Performance of a Silica Bead-Embedded Porous Fluoropolymer Composite Matrix for Li-Ion Batteries

Abstract

Potential composite polymer electrolyte (CPE) membranes, comprising a poly(vinylidene difluoride) (PVdF) and poly(vinylidene fluoride-hexafluoropropylene) (P(VdF-HFP)) blend with embedded silica spheres are fabricated through a spinning cum immersion precipitation technique. Especially, when the weight percentage of PVdF/P(VdF-HFP)/SiO2 is 55/40/05, the membrane exhibits low electrolyte leakage and low thermal shrinkage. The fabricated membranes and the corresponding polymer electrolytes are utilized as CPEs for Li+ batteries, and their electrochemical performances are evaluated. Among the membranes studied in this work, the ionic conductivity of S5-CPE is measured to be the highest value of 9.9 mS cm-1 at room temperature, which is favorable for displaying good electrochemical performances. A LiFePO4|Li cell with the as-prepared S5-based CPE exhibits a higher initial discharge capacity of 157 mAh g-1 and outstanding cyclic stability with 92% capacity retention at 0.2C rate after 500 cycles. The lithium transference number (t+) of the system is found to be 0.28. This can be attributed to the excellent compatibility of the synthesized CPE membrane possessing high cyclic stability and capacity retention for Li+-ion batteries.