Abstract:

LiNi_0.5-xAl_2xMn_1.5-xO₄(0≤2x≤0.15) was prepared by spray drying process. The effects of Al substitution for both Ni and Mn on the structural and electrochemical properties were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM), inductively coupled plasma-atomic emission spectrometry(ICP-AES), Fourier transform infrared spectrometer(FTIR), charge-discharge test and cyclic voltammetry(CV). The results show that the substitution of Al for Ni and Mn in the LiNi_0.5Mn_1.5O₄ resultes in the structural transformation from P4₃32 to Fd3m in terms of the space group, which is believed to relate to the increase of the lithium diffusion coefficient, and consequently upgrade the rate capability. At room temperature the LiNi_0.45Al_0.1Mn_1.45O₄ sample presents the best rate capability with the discharge capacity of 109 mA·h/g at 5 C rate, which is about 87% of its capacity of 126 mA·h/g at 0.5 C. Moreover, Al substitution for Ni and Mn can effectively suppress the dissolution of manganese into the electrolyte solution when electrode was operated at elevated temperature(50 ℃), resulting in a remarkable improvement in the cyclic performance at a high rate at elevated temperature. The LiNi_0.45Al_0.1Mn_1.45O₄ sample delivers a capacity of 121.7 mA·h/g with a capacity retention of 94% in 50 cycles operated at 3 C rate and 50 ℃.

Key words: Li-ion battery, Cathode material, Spray drying, LiNi_0.5-xAl_2xMn_1.5-xO₄ Electrochemical property