Asymmetry in anodic and cathodic polarization profile for LiFePO₄ positive electrode in rechargeable Li ion battery

Abstract

Asymmetric kinetics in the electrochemical charge–discharge reaction has been investigated in the two-phase coexistence system at LiFePO₄ positive electrodes for rechargeable Li ion batteries. The analyses of the electrochemical polarization profiles obtained by galvanostatic-pulse cycles reveals that nucleation and mass-transport is rate determining process for anodic and cathodic (charge and discharge) reaction, respectively, at high-rate conditions. We suggest that present two-phase system of LiFePO₄–FePO₄ forms core–shell type construction in each particle or agglomerate of particles, where LiFePO₄ prefer to reside at outer shell-region of particles maybe due to smaller interfacial energy with electrolytes.