Ionic/Electronic Conducting Characteristics of LiFePO[sub 4] Cathode Materials

Abstract

The ion diffusion coefficient of lithium iron phosphate cathode materials should not be measured by the standard method because there is no composition variation but the movement of the interface during Li insertion/extraction. A method to measure the intrinsic electronic and ionic conductivity of mixed conductive was reported, for the first time, based on the conductivity measurements of mixed conductive solid electrolyte using blocking electrodes. The conductivities of the three materials (mixed electronic/ionic conductor, electronic conductor, and ionic conductor), were measured using the proposed method, and the electronic and ionic conductivities were linked with their electrochemical reaction kinetics and rate capabilities. These samples have the same X-ray diffraction crystal structure and similar particle size, but different rate performance due to the difference in the ionic/electronic conductivity. The rate performance of the mixed electronic/ionic conductive is much higher than that of the electronic conductive and the ionic conductive .