POLYMER SOLID ELECTROLYTES FROM THE PEG-PMMA-LICF3SO3 SYSTEM

Highly conductive solid polymeric electrolytes based upon low molecula r weight poly(ethylene glycol) and ethylene oxide/propylene oxide copo lymers blended with up to 50% by volume of poly(methyl methacrylate) h ave been synthesized using LiCF3SO3 (25:1 ether oxygen to cation ratio ). Room-temperature ionic conductivities were measured to be in the ra nge 10(-4) to 10(-5) S/cm for poly(methyl methacrylate) concentrations up to 30% by volume. In some cases, the addition of the poly(methyl m ethacrylate) enhanced the conductivity. All of the electrolytes studie d were either amorphous or crystallized below 0 degrees C. The variati on of conductivity with temperature and polymer composition was measur ed and the results were analyzed in terms of effective medium theory a nd semiempirical considerations. Ionic transport is coupled to the str uctural relaxation of the polymer segments. At lower temperatures acti vated processes were required. Both charge carrier mobility and charge concentration were found to contribute to conduction. The effective m edium theory quantitatively describes conductivities of amorphous hete rogenous systems of limited miscibility (microphase separation) quite well. For miscible or partially crystalline systems other effects not incorporated in this theory play an important role, and conductivities are measured to be higher than theoretically predicted. (C) 1994 John Wiley & Sons, Inc.