Effects of Co doping on Li[Ni0.5CoxMn1.5-x]O-4 spinel materials for 5 V lithium secondary batteries via Co-precipitation

Abstract

Effect of Co substitution for Mn on Li[Ni0.5CoxMn1.5-x]O-4 was investigated. Co-precipitation was employed to synthesize the [Ni0.25CoxMn0.75-x](OH)(2) as a precursor and it was fired with LiOH at 900 degrees C for 20 h in air. From Rietveld refinement of X-ray diffraction data and scanning electron microscopic examinations, it was found that the as-synthesized Li[Ni0.5CoxMn1.5-x]O-4 were crystallized in cubic spinel structure with Fd3m space group and the final products presented spherical secondary morphology (3 mu m in average). Electrochemical investigation revealed that Co3+ replacement for Mn4+ gave rise to improved rate and cycling performances probably due to the improved electronic conductivity and structural stability achieved by the presence of Co3+ in the spinel Li[Ni0.5CoxMn1.5-x]O-4.