Preparation And Modification Of High-voltage Lithium-ion Battery Cathode Material LiMn_1.5Ni_0.5O₄

The high voltage lithium-ion battery material Li Ni0.5Mn1.5O4 has the spinel structure, and also has high working voltage, high energy density and high specific capacity which make it a perspective material for the future application. However, because of the high voltage during working, the specific capacity drops seriously when it works. So the cycle performance needs to be enhanced. This article makes a study on the preparation and the modification of the Li Ni0.5Mn1.5O4 material.Here, the impact of the sintering parameters like the temperature and the cooling rate is carried out is studied. The cooling rate has the impact on the content of the Mn3+ in the material. The slower the cooling rate is, the less Mn3+ in the material. And by analyzing the contents of the Ni and Mn in the cycled materials and electrolyte, we found the fact that the less Mn3+ content in the material, the more Mn and Ni in the cycled electrolyte. And the cycle performance is better when the Mn3+ is much enough.To optimize the electrochemical performance of the Li Ni0.5Mn1.5O4 material, Zn O is coated on the surface of the Li Ni0.5Mn1.5O4 material by solid state reaction. And the cyle performances under room temperature and high temperature are enhanced.The capacity retentions increase from 84.39% to 86.41% under room temperature, 84.39% to 86.41% under 40 °C, from 73.28% to 87.58% under 55 °C.Doping are also applied to optimize the electrochemical performances of Li Ni0.5Mn1.5O4 material. Li Ni0.4Cr0.15Mn1.45O4 has 100% capacity retention when cycles under room temperature at 0.5C rate for 116 times and 99.1% capacity retention when cylces under room temperature at 1C for 200 times. Proper content of the F doped into the Li Ni0.5Mn1.5O4 material can increase the electrochemical performance, Li Ni0.5Mn1.5O3.975F0.05 has the capacity retention about 94.23% when cycles 50 times under 55°C at 0.5C rate. However, the Li Ni0.5Mn1.5O3.95F0.1 can only keep 54.2% of the capacity under the same condition.In conclusion, the control of the sintering parameters, the surface modification using Zn O and the substitution of Mn using the F and Cr elements can enhance the cycle performance of the Li Ni0.5Mn1.5O4 material.