Novel Electrospun Poly(vinylidene Fluoride-co-hexafluoropropylene)-in Situ Sio_2 Composite Membrane-based Polymer Electrolyte For Lithium Batteries

摘要

Composite membranes of poly(vinylidene fluoride-co-hexafluoropropylene) {P(VdF-HFP)} and different composition of silica have been prepared by electrospinning polymer solution containing in situ generated silica. These membranes are made up of fibers of 1-2 μm diameters. These fibers are stacked in layers to produce fully interconnected pores that results in high porosity. Polymer electrolytes were prepared by immobilizing 1 M LiPF_6 in ethylene carbonate (EC)/dimethy! carbonate (DMC) in the membranes. The composite membranes exhibit a high electrolyte uptake of 550-600%. The optimum electrochemical properties have been observed for the polymer electrolyte containing 6% in situ silica to show ionic conductivity of 8.06 mS cm~(-1) at 20 ℃, electrolyte retention ratio of 0.85, anodic stability up to 4.6V versus Li/Li~+, and a good compatibility with lithium metal resulting in low interfacial resistance. A first cycle specific capacity of 170 mAh g~(-1) was obtained when the polymer electrolyte was evaluated in a Li/lithium iron phosphate (LiFePO_4) cell at 0.1 C-rate at 25 ℃, corresponding to 100% utilization of the cathode material. The properties of composite membrane prepared with in situ silica were observed to be comparatively better than the one prepared by direct addition of silica.