A THEORETICAL-MODEL FOR COMPOSITE ELECTROLYTES .2. PERCOLATION MODEL FOR IONIC-CONDUCTIVITY ENHANCEMENT

A novel method of a combination of a percolation model with the space charge layer model is derived. For the first time, this gives an analy tical solution for the ionic-conductivity enhancement of composite ele ctrolytes, The conductivity enhancement is directly related to the siz e of second phase particles and matrix particles, the density of the d efects as charge carriers and temperature. The theoretical optimum-con tent of the second phase with an ideal random distribution is solved a s 40 vol%. At the optimum-content, the ionic conductivity of the compo site electrolytes reaches the maximum. With the introduction of the no n-ideal random distribution of matrix particles or second phase partic les, an analytical solution based on the percolation model was derived . The theoretical results fit the experimental data quantitatively ver y well for LiI/Al2O3 and CuCl/Al2O3 systems in the whole range of the second phase content admired in the matrix. The shift effect of optimu m-content away from the theoretical optimum-content of 40 vol%, the re ason for which is unknown so far, is caused by the non-uniform distrib ution of either matrix particles or second phase particles and this no n-uniform distribution always degenerates the conductivity enhancement seriously.