Preparation And Modification Of Lithium-rich Manganese-based Cathode Material

With the continuous rise of the new energy industry,more and more machinery and equipment are shifting from fossil fuel-powered to electricity-powered,posing a huge challenge to the current energy storage level.This means that people need a positive electrode material with high energy density and high discharge voltage to provide energy to these machinery and equipment with the smallest possible volume and weight.Li-rich manganese-based positive electrode materials（LRMO）have high energy density,high discharge voltage,and other advantages that meet the current development needs.However,current Li-rich manganese-based positive electrode materials still have a series of problems,including complex preparation processes that usually require long-term sintering at high temperatures of up to 900°C or higher.The high sintering temperature poses great safety hazards and affects the uniformity of the crystal structure due to uneven temperature during mass production.In addition,there are several problems with lithium-rich manganese-based materials themselves,including capacity attenuation,voltage attenuation,and poor rate performance,making it difficult to be substantially used in commercial areas.Therefore,this article uses the oxalate co-precipitation method to prepare a Li-rich manganese-based positive electrode material with the composition of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂（LRM）and studies the electrochemical properties of Li-rich manganese-based positive electrode materials prepared under different ratios of precipitating agent.Introducing mechanical ball-milling technology,the effect of the duration factor of mechanical ball-milling on the synthesis of Li-rich manganese-based positive electrode materials is explored.It is found that the prepared positive electrode material with the introduction of ball-milling technology has higher discharge voltage and moderate ball-milling can reduce particle size and improve its consistency.Then,different sintering insulation time and sintering temperature are studied to determine the optimal insulation time and sintering temperature.In addition,the LRM positive electrode material is modified by coating Li Ni_0.5Mn_1.5O₂,which has better stability under high voltage,on its surface.The coating of the high-voltage-resistant material achieves good protection of Li-rich manganese-based positive electrode materials,and Li Ni_0.5Mn_1.5O₂ itself as a positive electrode material can also participate in the reaction to provide additional capacity and higher potential.By coating the material with Li Ni_0.5Mn_1.5O₂ at different ratios,it is found that the coated positive electrode material has a certain capacity reduction,but its voltage is greatly improved,and its stability is also improved.Based on this,by adjusting the cut-off voltage during the battery charge and discharge process,it is proved that the threshold for LRM to undergo a phase transition is between 4.45～4.5 V,and the positive electrode activated after 4.6 V still has a considerable specific capacity even though the subsequent cut-off voltage is lowered,and its cycle stability can be greatly improved.