Preparation And Modification Of High Nickel Ternary Lithium-ion Battery Cathode Materials By Hydrothermal Method

Lithium-ion batteries with high operating voltage and energy density are widely used in new energy vehicles.The high nickel ternary cathode material Li Ni_1-x-yCo_xMn_yO₂（0.6≤1-x-y≤1.0）,on the other hand,has become the most dominant cathode material for long-range power batteries due to its higher energy density;In order to further improve the range of new energy electric vehicles,increasing the specific capacity has become a key factor,which can be done in two directions:composition and structure.In this regard,the effects of sodium ion doping and zirconium ion coating co-modification on the structural morphology and electrochemical properties of high nickel materials were investigated.In terms of microstructure,the control of surfactants on the morphology was investigated,and the effects of different properties of surfactants,different hydrothermal processes and different calcination processes on the crystal growth and electrochemical properties of the high nickel ternary materials were investigated.The products were characterized by XRD,SEM and TEM,assembled into button cells for electrochemical testing and blue power testing to investigate the relationship between different influencing factors and the crystal structure,microscopic morphology and electrochemical properties of the materials.Specifically this thesis carries out research from three aspects,the research includes:（1）In this paper,firstly,the high nickel ternary precursor Ni_0.8Co_0.1Mn_0.1（OH）₂ was prepared by hydrothermal method with sodium hydroxide as precipitant and ammonia as complexing agent,and the effects of different hydrothermal time and temperature and different nature of surfactants and their contents on the structure and morphology of the high nickel ternary precursor were investigated to obtain the optimal precursor preparation process:hydrothermal temperature of 170℃,hydrothermal time of 12 hours,and modification with cationic surfactant benzalkonium bromide,which can obtain ternary precursors with uniform particle size,uniform distribution and high crystallinity.（2）The high nickel ternary cathode material LiNi_0.8Co_0.1Mn_0.1O₂ was obtained by calcination of the precursor mixed with lithium source under the optimal process conditions,and its effects on the structural morphology and electrochemical properties of the high nickel ternary cathode material were investigated by controlling the calcination temperature and time.The optimum calcination process was obtained by XRD,SEM characterization and electrochemical analysis:calcination temperature was 750℃,calcination time was 8 h,and the high nickel ternary cathode material with uniform morphology,the lowest lithium-nickel mixing degree and the highest crystallinity was obtained,and the discharge specific capacity reached 181.6 m Ah·g^-1at a multiplicity of 0.2C.（3）The high nickel ternary cathode material co-modified by Na ion doping and Zr element coating was prepared by hydrothermal method,and the Li layer spacing was enlarged by introducing Na ions to occupy the Li layer to inhibit Li-Ni mixing and thus improve the cycling performance of the material,and the Li layer space was increased to improve the multiplicity performance.The Na/Zr co-modified high nickel ternary cathode material has a discharge specific capacity of 210.5 m Ah·g^-1at a multiplicity of 0.2C and a retention rate of97.2%after 100 cycles.The capacity retention rate reached 95.7%after 50 cycles of charging and discharging at multiplicities of 0.2C,0.5C,1C,2C,and 0.2C.