Preparation of porous, chemically cross-linked, PVdF-based gel polymer electrolytes for rechargeable lithium batteries

This study reports the development of a new system of porous, chemically cross-linked, gel polymer electrolytes based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) copolymer as a polymer matrix, polyethylene glycol (PEG) as a plasticizer, and polyethylene glycol dimethacrylate (PEGDMA) as a chemical cross-linking oligomer. The electrolytes are prepared by a combination of controlled evaporation and thermal polymerization of PEGDMA. PVdF-HFP/PEG/PEGDMA gel polymer electrolytes with a composition of 5/3/2 exhibit both high ambient ionic conductivity, viz., >1 mS cm(-1), and a high tensile modulus of 52 MPa, because of their porous and network structures. All the blends of electrolytes are electrochemically stable up to 5 V versus Li/Li+ in the presence of I M LiPF6/ethylene carbonate-diethyl carbonate (EC-DEC). With these polymer electrolytes, rechargeable lithium batteries composed of carbon anode and LiCoO2 cathode have acceptable cycleability and a good rate capability. (C) 2004 Elsevier B.V. All rights reserved.