Abstract:Spinel compound LiNi_0.5Mn_1.5O₄ with high capacity and high rate capability was synthesized by solid-state reaction. At first, MnCl₂·4H₂O and NiCl₂·6H₂O were reacted with (NH₄)₂C₂O₄·H₂O to produce a precursor via a low-temperature solid-state route, then the precursor was reacted with Li₂CO₃ to synthesize LiNi_0.5Mn_1.5O₄. The effects of calcination temperature and time on the physical properties and electrochemical performance of the products were investigated. Samples were characterized by thermal gravimetric analysis(TGA), scanning electron microscopy(SEM), X-ray diffractometry(XRD), charge-discharge tests and cyclic voltammetry measurements. Scanning electron microscopy(SEM) image shows that as calcination temperature and time increase, the crystallinity of the samples is improved, and their grain sizes are obviously increased. It is found that LiNi_0.5Mn_1.5O₄ calcined at 800 ℃ for 6 h exhibits a typical cubic spinel structure with a space group of Fd3m. Electrochemical tests demonstrate that the sample obtained possesses high capacity and excellent rate capability. When being discharged at a rate as high as 5C after 30 cycles, the as-prepared LiNi_0.5Mn_1.5O₄ powders can still deliver a capacity of 101 mA∙h/g, which shows to be a potential cathode material for high power batteries.

Key words: lithium ion battery; LiNi_0.5Mn_1.5O₄; cathode; solid-state reaction