Synthesis of LiNi0.01CrxMn1.99-xO4 (x ≤ 0.07) cathode materials by molten salt combustion and their electrochemical properties

Ni and Cr co-doped spinel LiNi0.01CrxMn1.99-xO4 (x ≤ 0.07) cathode materials were prepared via molten salt combustion to improve electrochemical performance of lithium ion battery cathode materials. The crystalline structure, micromorphology and phase composition of the as-prepared samples were characterized by the X-ray diffraction (XRD), the scanning electron microscopy (SEM), the X-ray photoelectron spectrometer (XPS). Moreover, the electrochemical performance was investigated by galvanostatic charge and discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results show that all samples are assigned to a spinel structure of LiMn2O4 with the single-phase, and the particle size is 50-100 nm. The x = 0.05 sample has a high Li+ diffusion coefficient and low charge transfer resistance, which indicates an excellent kinetic and electrochemical performance. The x = 0.05 sample exhibits an initial discharge specific capacity of 114.3 mA∙h∙g-1 with a capacity retention rate of 74.8% after 500 cycles at 1 C. Even at relatively high current rate of 20 and 30 C, the capacity retention rate can be retained at 51.9% and 43.1% after 1 000 cycles long-cycling, respectively. The proper amount of Ni-Cr co-doping enhances the crystal structure stability and improves the electrochemical performance of LiMn2O4. © 2020, Editorial Board of Journal of Chemical Engineering of Chinese Universities". All right reserved."