Study on the simple synthesis and high-rate and long-cycle performance of spinel-type LiCr_0.04Mn_1.96O₄ cathode materials

A Cr-doped LiCr_0.04Mn_1.96O₄ cathode material was synthesized via solid-state combustion method. The crystal structure, crystallinity, elemental composition and morphology of the material were characterized by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The electrochemical performance of the cathode material was tested by cyclic voltammetry (CV), galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy (EIS). The results show that the crystal structure of the Cr-doped modified LiCr_0.04Mn_1.96O₄ cathode material is consistent with the spinel LiMn₂O₄, and it has high crystallinity and good particle dispersion. The LiCr_0.04Mn_1.96O₄ cathode material delivered an initial discharge capacity of 100.3 mA·h·g^-1 at 1 C, and the capacity retention rate after 200 cycles is 83.3%. At 5 C the LiCr_0.04Mn_1.96O₄ cathode material showed a high initial discharge capacity of 90.4 mA·h·g^-1, with the capacity retention rate of 66.2% after 1000 cycles. Appropriate Cr doping can reduce the Jahn-Teller effect, and improve the structural stability of the material. The LiCr_0.04Mn_1.96O₄ material also has a larger lithium ion diffusion coefficient (1.18×10^-16 cm²·s^-1) and a smaller apparent activation energy (30.10 kJ·mol^-1), thus improving the cycle life and rate capacity of spinel LiMn₂O₄ cathode materials.