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

Lithium manganese oxide powders (LiMn 2 O 4 ) 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 LiMn 2 O 4 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-Li 2 MnO 3 -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 ¢XC. In addition, decreasing the concentration of the aqueous phase substantially reduces the particle size of LiMn 2 O 4 powders. Nanometered-LiMn 2 O 4 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 LiMn 2 O 4 powders was demonstrated to effectively increase the specific capacity and improve the cyclability of LiMn 2 O 4 powders.