Preparation of PVDF/P(MMA-co-PEGMA) Porous Membranes via Phase Inversion Process for Gel Polymer Electrolyte

Conducting separator based on porous membrane is one of the key materials for high performance lithium ion batteries. A brush-like amphiphilic copolymer called poly (methyl methacrylate-co-ethylene glycol methacrylate), P(MMA-co-PEGMA), was synthesized and used as additive to prepare porous PVDF membranes via immersion precipitation phase inversion process. Then the membranes were immersed in liquid electrolyte to form lithium ion conducting gel polymer electrolyte membranes (Li-GPEM). It was found that the membranes have porosity higher than 70% and quite well-defined sponge-like structure. The adoption of brush-like P(MMA-co-PEGMA) can efficiently improve the ion conductivity of Li-GPEM (as high as 3.01x10(-3)S/cm for the membrane made from casting solution containing PVDF/ P(MMA-co-PEGMA) in 10/4 by weight) while keeping the decomposition voltage higher than 5.0V (versus Li+/Li). These results primarily indicate the activation of P(MMA-co-PEGMA) in porous PVDF membranes used for Li-GPEM.