Suppressed phase separation in high-voltage LiNi0.5Mn1.5O4 cathode via Co-doping

Spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode material with high operating voltage and energy density. However, the poor rate performance caused by the two-phase reaction during charging and discharging limits its large-scale application. In this work, Co3+ doped LNMO cathode materials are prepared by co-precipitation method, and the effect of Co3+ doping replacing Mn4+, as well as the amount of Co3+ doping (LiNi0.5CoxMn1.5-xO4) are explored. Co3+ doping increases the content of Mn3+, thus improving the electronic conductivity of LNMO. Co3+ doping suppresses the phase transition of LNMO during discharging, which results in a smaller volume change and improves cycling stability. The presence of a solid solution intermediate allows for more uniform changes within the particles during the discharge process, thus increasing the diffusion rate of Li+ ion. LiNi0.5Co0.05Mn1.45O4 exhibits the best electrochemical performance compared to other samples, with a discharge specific capacity of 111.1 mAh g-1 after 500 cycles at 1 C and a capacity retention of 92.4%. At 10C high rate, the specific discharge capacity is 106.8 mAh g-1. Our research reveals that Co3+ doping can improve the electrochemical performance of LNMO and provide a deeper insight into Co3+ doping of other cathode materials.