Improved electrochemical properties of Lu-doped LiNi0.5Mn1.5O4 cathode materials for 5 V lithium-ion batteries

LiNi0.5Mn1.5O4 (LNMO) is considered as a promising cathode material for the next-generation high-energy-density lithium-ion batteries. However, the application of LNMO is hindered by its severe Mn dissolution and capacity decay at high voltages. To address this issue, a novel LiNi0.5-x/2Mn1.5-x/2LuxO4 (x = 0, 0.005, 0.02, 0.04) material was successfully prepared using a solid-state method to investigate the effects of phase structures and morphologies induced by Lu3+ doping on the electrochemical properties of the LNMO. When compared to the pristine LNMO material, the LNMO doped with Lu3+ exhibited a significant increase in lattice parameters, resulting in a larger lithium-ion diffusion channel. Furthermore, the truncated octahedral structure enhanced the contact area with the electrolyte, leading to a substantial decrease in Mn3+ concentration. It's noteworthy that the LiNi0.49Mn1.49Lu0.02O4 (LNMO-Lu0.02) sample exhibits the most favorable electrochemical properties. After 200 charge-discharge cycles at a current density of 1 C, the LNMO-Lu0.02 sample demonstrates a discharge capacity of 129.54 mAh/g with a capacity retention rate of 97.46 %. Even at a high current density of 20 C, it maintains a discharge capacity of 107.19 mAh/g, which is much better than the pristine sample. The results indicate a significant improvement in the electrochemical properties and structural stability of Lu-doped LNMO cathode materials.