Kinetic characteristics of mixed conductive electrodes for lithium ion batteries

The rate performances of four mixed conductive electrodes (Li4/3Ti5/3O4, LiFePO4, LiCoO2 and LiCo1/3N1/3M1/3O2) were investigated using galvanostatic charge/discharge, electrochemical impedance Spectroscopy (EIS) and galvanostatic intermittent titration (GITT). These four electrode materials can be roughly divided into two groups according to the structure change during Li intercalation/extraction, i.e. the phase transition materials (Li4/3Ti5/3O4 and LiFePO4) and mixed phase transformation and solid solution materials (LiNi1/3Mn1/3Co1/3O2 and LiCoO2). Both the ionic conductivity and phase transition kinetics have a strong impact on the rate capability of the electrode material in addition to the generally accepted factors such as particle size and electronic conductivity. The rate capabilities of Li4/3Ti5/3O4 and LiFePO4, which have an extended flat region in the charge/discharge curves, mainly depended on their phase transition kinetics. The rate performance of the solid solution materials were controlled by the ionic conductivity, with some influence from the electronic conductivity. (c) 2006 Elsevier B.V. All rights reserved.