Synthesis And Modification Of Nickel-rich LiNi_0.8Co_0.1Mn_0.1O₂ Cathode Material For Lithium-ion Batteries

With the rapid development of society and the large consumption of traditional fossil energy,human beings are facing serious energy shortages and environmental problems.Promoting the new energy vehicle industry is an effective way to alleviate energy and environmental problems,and therefore has attracted widespread attention worldwide.The core component of new energy vehicles is energy storage batteries.Lithium-ion battery is a typical representative of the power batteries for new energy vehicles due to their many advantages,such as high voltage,high energy density,high output power,low selfdischarge,long cycle life,and high rate performance.However,the energy density of traditional lithium-ion batteries has not been able to meet people’s needs for the high range of new energy vehicles.The positive and negative materials that make up the batteries ultimately determine the energy density of the batteries.Under the premise that graphite is mainly used as the negative electrode materials in the current market,the performance of the positive electrode material plays a decisive role in the energy density of the batteries.Among the positive electrode materials,nickel rich ternary materials have higher energy density advantages than LiFePO4 and LiCoO2,so they got attention by enterprises and scientific researchers.However,the nickel rich ternary material has structural instability during the charge and discharge process,and the cycle performance of the batteries is poor.This article takes the high nickel ternary material LiNi0.8Co0.1Mn0.1O2 as the research object,starting from the fine preparation and doping modification of the material,systematically studies the preparation process and elemental doping of LiNi0.8Co0.1Mn0.1O2 cathode material and their influences to physical properties and electrochemical properties aiming to improve its cycling performance.It has a certain role in promoting the commercial application of LiNi0.8Co0.1Mn0.1O2 cathode materials.The specific research content is as follows:The pure phase LiNi0.8Co0.1Mn0.1O2 material was prepared by hydrothermal method and subsequent calcination.The effects of sintering temperature and lithium content on the electrochemical performance of the material were systematically studied.It is found that too low calcination temperature will cause serious nickel-lithium cation mixing,and too high calcination temperature will make the material particles coarse.It has the best cycle performance when calcined at 850℃,and the best rate performance at 800℃.At the same calcination temperature,the proportion of less lithium will form a nonstoichiometric compound,which will inhibit the performance of the material.If the amount of lithium is too high,excessive residual lithium compounds will be formed,and the performance of the material will be deteriorated.When the lithium content is 1.02,it has the best cycle and rate performance.Compared with the material synthesized by the coprecipitation method,the cycling performance and rate performance have been greatly improved.At the current density of 0.5 C,the capacity retention rate of 100 circles is increased by 7.7%,and at a high current density of 10 C,the rate performance is improved by 40.7 mAh g-1.From the perspective of elemental doping,a LiNi0.8Co0.1Mn0.1O2 material co-doped with Al,Mg,and Ti elements was prepared.The effects of various elements were combined to improve the kinetics of lithium ion diffusion in the material and suppress the increase of resistance and structural damage of the material during the cycling process,improving the cycling performance,high voltage performance,and rate performance of the batterie.The main reasons for the co-doping of Al,Mg,Ti elements to improve the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 materials can be summarized as follows:1)Al,Mg,Ti doping and O form stronger Al-O,Mg-O and Ti-O bonds make the material have higher structural stability;2)Doping increases the(003)crystal plane of the material,facilitates lithium ion transmission,and improves lithium ion diffusion kinetics Performance;3)Doping reduces the nickel-lithium cation mixing of the material.