Ionic liquid based PVDF/PMMA gel polymer electrolyte for lithium rechargeable battery

Abstract

The microstructure of a polymer blend as a gel polymer electrolyte affects significantly the electrochemical performances of a Lithium ion battery. Therefore, an appropriate control of the composition of the blending is crucial to obtain a porous structure. In this paper, PVDF/PMMA membrane was successfully prepared via phase-separation method by using salicylic acid as a foaming agent to produce a porous structure within the polymer blend matrix. Ionic liquid-salt mixtures of 1-ethyl-3 methyl imidazolium triflouromethanysulfonyl imide and lithium bis-triflouromethylsulfonyl imide were used to activate the PVDF/PMMA membrane. The as-prepared PVDF/PMMA membrane contains pores when observed from scanning electron microscope, which leads to the high ionic-liquid electrolyte uptake. The membrane with 10 wt% PVDF and 90 wt% PMMA exhibited a high ionic conductivity of 3.097 mS cm-1 at room temperature with high lithium ion transference number (0.7922) and wide electrochemical stability window (4.3 V). Its electrochemical performance was evaluated by LiFePO4 half-cell, suggesting that this ionic-liquid gel polymer electrolyte is possible to be developed as an electrolyte in lithium rechargeable battery.