FAST-ION TRANSPORT IN NEW LITHIUM ELECTROLYTES GELLED WITH PMMA .1. INFLUENCE OF POLYMER CONCENTRATION

Conductivities and viscosities of gel electrolytes made of poly(methyl methacrylate) (PMMA)-LiClO4-propylene carbonate have been measured. In this paper, the influence of the concentration of polymer in the gell ed electrolytes is investigated. These gels are both anhydrous and lit hium ionic conductors. It is found that ionic conductivity decreases w ith increasing amount of polymer and lies in the range 5 x 10(-3) to 5 X 10(-5) S/cm at room temperature. On the other hand, the viscosity v aries greatly from 8 x 10(-3) to 6 x 10(6) Pa.s leading to a solid adh esive material. The thermal dependence of both conductivity and viscos ity can be accurately described by a VTF expression. The experimental results show that some change occurs in the conduction path of the gel around 30-35 w/o of polymer. For low concentrations of PMMA, the gela tinized electrolytes can be considered as a liquid electrolyte encaged in a polymer matrix. On the other hand, for high concentrations, some interactions may be created between the polymer chains and the conduc ting electrolyte leading to both a decrease of conductivity and an inc rease of the activation energy of conduction.