Preparation And Surface Modification Of Nickel-rich Cathode Materials For Lithium-ion Batteries

High-nickel cathode materials have the advantages of high capacity and low cost,and are considered to be widely used as cathode materials for lithium-ion power batteries.However,with the increase of nickel content,the synthesis process of materials is more complicated and difficult,cycle stability,rate performance and security performance also need to be further improved.Aiming at these problems,this paper takes Li Ni_0.8Co_0.1Mn_0.1O₂ as the research object and launches a series of modification studies.First,Li Ni_0.8Co_0.1Mn_0.1O₂ material with high crystallinity and good layered structure are synthesized by high-temperature solid-phase method.On the basis of this,the lithium phosphate coating is successfully formed on the surface NCM811 material by spray drying method using ammonium dihydrogen phosphate as a raw material.The results show that the lithium phosphate coating effectively reduces the residual lithium salt on the surface of the material,improves the interface properties,and improves the rate performance and cycle performance of the material.The 1 wt%lithium phosphate-coated material has a discharge capacity of 174.0 m Ah·g^-1 after 100 cycles at 1 C.And the capacity retention rate is 91.6%.Afterwards,tin oxide is used to coat Li Ni_0.8Co_0.1Mn_0.1O₂.It is found that the tin oxide coating layer can increase the electronic conductivity of the material,and the charge transfer resistance is significantly reduced during the charge and discharge cycle.Thereby,the material rate performance is improved.At the same time,the coating layer also relieves the side reaction between the electrode material and the electrolyte,stabilizes the material structure,and improves the cycle performance.When the coating amount is 1 wt%,the discharge capacity of the material remains at 191.4 m Ah·g^-1after 100 cycles at 1 C,and the retention rate is 98%.The discharge capacity can maintain 170.0 m Ah·g^-1 at 5 C.