Composite polymer electrolytes reinforced by non-woven fabrics

Composite electrolytes composed of a blend of polyethylene glycol diacrylate (PEGDA), poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) together with a non-woven fabric have been prepared by means of ultra-violet cross-linking. As the non-woven fabric serves as a mechanical support medium, the composite electrolyte has good integrity up to an initial liquid electrolyte uptake of 1000% (ethylene carbonate (EC)-dimethyl carbonate (DMC)-ethylmethyl carbonate (EMC-LiPF6). The ionic conductivity of the composite electrolytes reaches 4.5 mS cm(-1) at an ambient temperature of around 18degreesC and are electrochemically stable up to about 4.8 V versus Li/Li+. The conductivity and interfacial resistance remain almost constant even at 80degreesC. Scanning electron micrographs show that the high-temperature behavior is associated with structural stability that is induced by chain entanglement between PVdF, PMMA and PEGDA network. A MCMB/LiCoO2 cell using the composite electrolytes retains >97% of its initial discharge capacity after 100 cycles at the C/2 rate (150 mA), and delivers more than 80% of full capacity with an average load voltage of 3.6 V at the 2C rate. The cell also shows much better cycle-life than one with a PVdF-coated composite electrolyte at high temperatures because of the better liquid electrolyte retention capability. (C) 2003 Elsevier B.V. All rights reserved.