Polymeric gel electrolytes reinforced with glass-fibre cloth for lithium secondary batteries

Polymeric gel electrolytes (PGE), based on polyacrylonitrile blended with p oly(vinylidene fluoride-co-hexafluoropropylene) (P(VdF-co-HFP)), which are reinforced with glass-fibre cloth (GFC) to increase the mechanical strength , are prepared for the practical use in lithium secondary batteries. The re sulting electrolytes exhibit electrochemical stability at 4.5 V against lit hium metal and a conductivity value of (2.0-2.1)x 10(-3) S cm(-1) at room t emperature. The GFC-PGE electrolytes show excellent strength and flexibilit y when used in batteries even if they contain a plasticiser. A test cell wi th LiCoO2 as a positive electrode and mesophase pich-based carbon fibre (MC F) as a negative electrode display a capacity of 110 mAh g(-1) based on the positive electrode weight at the 0.2 C rate at room temperature. Over 80% of the initial capacity is retained after 400 cycles. This indicates that G FC is suitable as a reinforcing material to increase the mechanical strengt h of gel-based electrolytes for lithium secondary batteries. (C) 2001 Elsev ier Science B.V. All rights reserved.