ENHANCEMENT OF THE IONIC-CONDUCTIVITY AND THE AMORPHOUS STATE OF SOLID POLYMER ELECTROLYTES FOR RECHARGEABLE LITHIUM BATTERIES

Complexes of LiCF3SO3 and a polymer obtained by polymerization of triethylene glycol dimethacrylate (TRGDMA) and its copolymerization with acrylonitrile (AN) at molar ratios of 0.67, 2.0 and 4.0, both in the presence of poly(ethylene glycol) dimethylether as a plasticizer, provides a.c. conductivities in the range between 10(-5) and 10(-4) S/cm at ambient temperature. An increase of conductivities has been found at growing ratios of AN:TRGDMA from 0 to 2.0 and molar ratios of ethylene oxide (EO) units:LiCF3SO3 ranging from 12 to about 26. The conductivity is nearly independent of the content of AN at EO:Li+ = 52. Impedance measurements of cells modified with these solid electrolytes show that the electrochemical behaviour of the composite lithium/PEO-lithium salt-complex is determined by the properties of the phase boundary metal/solid electrolyte. The mechanical stability of the polymer, acting simultaneously as a separator between the active electrodes, determines the cycle life.