Abstract:LiNi_0.5Mn_1.5O₄ was synthesized by two different coprecipitation methods: composite carbonate process and composite hydroxide method. The effects of calcination temperature of precursors on the physical properties and electrochemical performance of the samples were investigated. The results of scanning electron microscopy(SEM) show that as calcination temperature increases, the crystallinity of the samples is improved, and their grain sizes are obviously increased. X-Ray diffraction(XRD) data show that the LiNi_0.5Mn_1.5O₄ compounds obtained by two coprecipitation methods both exhibit a pure cubic spinel structure without any impurities. Furthermore, it is found that the samples prepared with relatively high temperature precursors present large initial discharge capacity (＞125 mA∙h/g) and excellent cycling stability with a capacity retention rate larger than 91% after 30 cycles at current density of 1 C. This probably derives from their higher crystallinity and larger grain sizes. However, the initial discharge capacity of LiNi_0.5Mn_1.5O₄ synthesized by composite carbonate process is smaller than that prepared by composite carbonate process, but it shows better capacity retention ability.

Key words: lithium ion battery; LiNi_0.5Mn_1.5O₄; coprecipitation method; precursor; spinel