Synthesis of Multicomponent Olivine by a Novel Mixed Transition Metal Oxalate Coprecipitation Method and Electrochemical Characterization

Abstract

The multicomponent olivine cathode material, LiMn 1/3 Fe 1/3 Co 1/3 PO 4, was prepared via a novel coprecipitation method of the mixed transition metal oxalate, Mn 1/3 Fe 1/3 Co 1/3 (C 2 O 4 )·2H 2 O. The stoichiometric ratio and distribution of transition metals in the oxalate, therefore, in the olivine product, was affected sensitively by the environments in the coprecipitation process, while they are the important factors in determining the electrochemical property of electrode materials with multiple transition metals. The effect of the pH, atmosphere, temperature, and aging time was investigated thoroughly with respect to the atomic ratio of transition metals, phase purity, and morphology of the mixed transition metal oxalate. The electrochemical activity of each transition metal in the olivine synthesized through this method clearly was enhanced as indicated in the cyclic voltammetry (CV) and galvanostatic charge/discharge measurement. Three distinctive contributions from Mn, Fe, and Co redox couples were detected reversibly in multiple charge and discharge processes. The first discharge capacity at the C /5 rate was 140.5 mAh g −1 with good cycle retention. The rate capability test showed that the high capacity still is retained even at the 4 C and 6 C rates with 102 and 81 mAh g −1, respectively.