Poly(vinylidene fluoride-co-hexafluoropropylene)/poly(methylmethacrylate)/ nanoclay composite gel polymer electrolyte for lithium/sulfur batteries

A gel polymer electrolyte (GPE) was developed by trapping 1 M solution of lithium hexafluorophosphate (LiPF₆) in organic carbonate mixture in a polymer matrix composed of poly(vinylidene fluoride-co-hexafluoropropylene)/ poly(methylmethacrylate)/montmorillonite nanoclay (PVDF-HFP/PMMA/MMT). The physical and electrochemical properties of the resulting gel polymer electrolyte were investigated. AC impedance spectroscopy revealed that the ionic conductivity of gel polymer electrolyte containing 5 wt% MMT attains a maximum value of 3.06∈×∈10^-3 S cm^-1 at room temperature. Li/S cells assembled with the GPE-delivered reversible discharge capacities of 1,418 and 1,071 mAh g^-1 in the first and 100th cycles at 0.1 C, respectively, along with high coulombic efficiency (about 100 %) over 100 cycles. The excellent cycle performance was attributed to the suppression of shuttle effect by the gel polymer electrolyte leading to the higher sulfur utilization in the cell. Even at a high C rate (1 C), the system still delivered 492 mAh g^-1 specific discharge capacity, demonstrating the good ionic conductivity of the GPE.