Effects of Co doping on Li[Ni_(0.5)Co_xMn_(1.5-x)]O_4 spinel materials for 5 V lithium secondary batteries via Co-precipitation

摘要

Effect of Co substitution for Mn on Li[Ni_(0.50Co_xMn_(1.5-x))O_4 was investigated. Co-precipitation was employed to synthesize the [ Ni_(0.25)Co_xMn_(0.75-x)](OH)_2 as a precursor and it was fired with LiOH at 900 ℃ 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[Ni_(0.5)Co_xMn_(1.5-x)]O_4 were crystallized in cubic spinel structure with Fd3m space group and the final products presented spherical secondary morphology (3 jim in average). Electrochemical investigation revealed that Co~(3+) replacement for Mn~(4+) gave rise to improved rate and cycling performances probably due to the improved electronic conductivity and structural stability achieved by the presence of Co~(3+) in the spinel Li[Ni_(0.5)Co_xMn_(1.5-x)]O_4.