Effect of La, Ce, Yb Doping on Properties of LiNi0.5Mn1.5O4 High Voltage Cathode Materials

High-voltage LiNi0.5Mn1.5O4 cathode materials doped with different rare earth elements were prepared by low temperature combustion method. The effects of different doping ratios (molar ratios of 0.5%, 1%, 2%) and different kinds of rare earth elements (La, Ce, Yb) on the material performance were investigated, and the influence mechanism was explored by X-ray diffraction, Raman spectrum, electron paramagnetic resonance and galvanostatic intermittent titration technique. X-ray diffraction pattern illustrates that rare earth doping can inhibit the generation of LixNi1-xO phase. The inductively coupled plasma spectroscopy illustrates that the doped rare earth elements are basically in accordance with the design proportion. Raman spectrum illustrates that rare earth elements can increase the ordered phase of the material and Ce doped sample has the most ordered phase. In combination with electron paramagnetic resonance oxygen vacancy test, it is found that Ce doped sample induces the increase of the proportion of ordered phase in the material, thus improving the stability of the material. Galvanostatic intermittent titration technique test showed that the diffusion coefficient of Ce-doped LiNi0.5Mn15O4 material was about 15 times higher than the undoped sample. In different doping proportion, the material with 1% doping amount had the best performance. Among the samples doping with the best amount of three rare earth elements, Ce doped samples had the best doping performance, and the specific discharge capacity of the first discharge can reach 133.3 mAh.g(-1), which was higher than the undoped group and the first discharge efficiency was increased by 18%. After 200 cycles at 1C, the capacity retention rate was 102%, which was 8% higher than the undoped group.