Toward Understanding of Electrical Limitations (Electronic, Ionic) in LiMPO[sub 4] (M=Fe, Mn) Electrode Materials

Abstract

To better understand the factors responsible for the poor electrochemical performances of the olivine-type , various experiments such as chemical delithiation, galvanostatic charge and discharge, cyclic voltamperometry, and impedance conductivity, were carried out on both and . Chemical delithiation experiments confirmed a topotactic two-phase electrochemical mechanism between and the fully delithiated phase (, , and ). We conclude that the limiting factor in the / electrochemical reaction is nested mostly in the ionic and/or electronic transport within the particles themselves rather than in charge transfer kinetics or structural instability of the phase. For instance, the electrical conductivity of ( at 573 K, ) was found to be several orders of magnitude lower than that of ( at 298 K, ).