EFFECTIVE-MEDIUM THEORY IN STUDIES OF CONDUCTIVITY OF COMPOSITE POLYMERIC ELECTROLYTES

The application of effective medium theory to a description of a tempe rature and composition dependence of conductivity of composite polymer ic electrolytes is presented. Conductivities of several composite syst ems containing conducting (NASICON) or nonconducting (Theta-Al2O3, pol yacrylamide) additives are analyzed in terms of effective medium theor y approaches. All of the systems studied are based on polyether matric es. The influence of grain size distribution, concentration and type o f additives on conductivity of composite systems is discussed. The mod el presented assumes that an increase in the conductivity in compariso n to polyether based electrolytes is due to the formation of highly co nductive layers at the polyether matrix-filler interface. Variation of the conductivity of this layer with grain sizes, and the concentratio n of a filler is assumed and discussed. The theoretical assumptions ar e confirmed by experimental data obtained by several techniques, such as impedance spectroscopy, DSC, NMR and energy dispersive X-ray diffra ctometry.