Abstract:

LiNi_0.5Mn_1.5O₄ (LNMO) is a cathode material known for its high operating voltage (4.7 V), high energy density (650 Wh/kg), and low cost. However, owing to factors such as electrolyte decomposition, Jahn-Teller effect, and Mn dissolution, LNMO cathode materials usually demonstrate rapid capacity fading and poor rate capability. To improve their electrochemical performance, we prepared Mg-Cr co-doped LMMO materials via the hydrothermal method and studied the influence of Mg-Cr co-doping content on the electrochemical performance of the LNMO cathode. Our experimental results show that the optimal electrochemical performance is achieved when the doping content of Mg and Cr is 2% each. The Mg-Cr co-doped LMMO cathode exhibits a discharge capacity of 137.3 mAh/g at 0.1C rate and a capacity retention of 85.74% after 200 cycles at 1C rate, markedly outperforming the original LNMO cathode (116.5 mAh/g and 51.82%, respectively). In addition, it delivers capacities of 121.8 mAh/g at 0.5C and 94.3 mAh/g at 5C. Mechanistic analysis shows that Mg-Cr co-doping promotes the formation of a disordered Fd\overline{\mathrm{3}}m phase, enhancing the electronic conductivity of LMMO material and reducing the electrochemical polarization and charge transfer resistance of the cathode. This study presents a simple method to improving the electrochemical performance of LNMO cathode and offers valuable insights for designing high-performance lithium-ion battery cathode materials.

Key words: LiNi_0.5Mn_1.5O₄, cathode material, Mg-Cr co-doping, electrochemical characteristic