Influence of the emulsification conditions on the microstructures and electrochemical characteristics of spinel lithium manganese oxide powders

Abstract

Lithium manganese oxide powders (LiMn2O4) with a spinel structure were synthesized via an optimized water-in-oil emulsion process. The influence of the emulsification conditions on the microstructures and physicochemical properties of LiMn2O4 powders was investigated. The phase purity of the synthesized powders significantly depends on the water-to-oil volume ratio in the emulsion. Increasing the water-to-oil ratio tends to decrease the stability of the emulsion that in turn leads to a segregation of water and oil phases. The unstable emulsion system results in the formation of an impure phase—Li2MnO3—that markedly decreases the charge and discharge capacities of the cathode materials. When water/oil volume ratio equals 1/5 or 1/10, monophasic spinel powders are formed at temperatures as low as 400 °C. In addition, decreasing the concentration of the aqueous phase substantially reduces the particle size of LiMn2O4 powders. Nanometered-LiMn2O4 powders with a particle size of 50 nm are obtained when the concentration of the aqueous phase is 1.0 M and the water-to-oil volume ratio is 1/5. Decreasing the particle size of LiMn2O4 powders was demonstrated to effectively increase the specific capacity and improve the cyclability of LiMn2O4 powders.