Study On Preparation And Modification Of High Nickel Ternary Cathode Material

The global electric vehicle market has developed rapidly,and the research on new energy vehicles has become more and more extensive,and higher requirements have been put forward on issues such as cruising range,charging rate,and safety performance.Although there are various technical researches on these issues,However,cathode materials for lithium-ion power batteries are a key technology,and it is very necessary to study electrode materials with high energy density,superb power density,wider working voltage window,and improving cycle life.The high nickel ternary material is one of the most promising electrode materials for large-scale commercial applications in the next generation.It has the advantages of excellent specific capacity,high operating voltage,supernal energy density and low cost.The defects in the structure of the nickel ternary material have caused its large-scale commercial application due to the mixed dislocation of cations,residual alkali on the surface,interfacial reaction with the electrolyte,and high temperature loss of oxygen during its synthesis and application.In order to further solve the above problems,this paper studies the effect on active materials through bulk doping and surface modification.The active material Li Ni_0.8Co_0.1Mn_0.1O₂ was bulk doped with aluminum as the dopant,obtain active materials with different doping ratios of Li(Ni_0.8Co_0.1Mn_0.1)_1-xAl_xO₂,where x=0,0.01,0.02,0.03,0.04.The research results show that Li(Ni_0.8Co_0.1Mn_0.1)_0.97Al_0.03O₂（NCMA3）has the best electrochemical performance.After 50 cycles at 0.1C rate,the capacity is 185.6 m Ah/g,and the capacity retention rate is 92.02%.Under 1C cycle After the 100 cycles,the capacity is 168.8m Ah/g,the mixing of cations is suppressed to a certain extent,and the reversibility and cycle stability of the active material are improved.The surface coating modification of the active material NCMA3 was carried out by magnetron sputtering and wet chemistry,and the effect of the Al₂O₃ coating layer obtained by different methods on the active material was compared.Among them,the active material NCM-Al₂O₃-C modified by the Al₂O₃ coating obtained by the method of magnetron sputtering shows good electrochemical performance.It is still has a big surplus of capacity about 202.9 m Ah/g which after 50 cycles,besides,the rate of charge and discharge is 0.1C,it can keep the original capacity of 93.3%.In the process of charge and discharge,the remnants of capacity is 148.12 m Ah/g which after 100cycles at a rate of 1C,however,the electrochemical performance of surface modification by wet chemistry is slightly worse.Using plasma vapor deposition（PECVD）to carry out the vapor deposition of methane plasma to form a carbon coating layer on the surface of the active material.The composition structure and electrochemistry of the active material under four different process conditions of time,temperature,power and atmosphere were studied of performance impact.After comparison,the NCM-N obtained under N₂ atmosphere showed the best electrochemical performance.Through 50 cycles,the capacity is 204.9m Ah/g which charge and discharge at a rate of 0.1C,actually,the capacity could retain94.21%.After 100 cycles,the capacity still has 188.5 m Ah/g which at a rate of 1C to charge and discharge,and the capacity could maintain 95.06%.It can maintain an average capacity of 131.7 m Ah/g at a high rate of 5C.The research results show that increasing the reaction time,increasing the output power,reducing the reaction temperature,and introducing nitrogen can improve the electrochemical performance of the active material.