Study On Preparation And Coating Modification Of Nickel Cobalt Manganese Ternary Anode Materials For Lithium Ion Batteries

Lithium-ion batteries?LIBs?have become the focus of attention due to their high energy density,long cycle life,and low environmental pollution.Cathode materials are the most important component of lithium ion batteries,and are currently one of the key factors restricting the performance of batteries.As one of the most promising cathode material for LIBs,nickel-cobalt-manganese ternary cathode materials Li Ni_0.5Co_0.2Mn_0.3O₂?NCM523?have the advantages of high specific capacity,environmental friendliness and low cost,but there are also some problems that need to be solved urgently,such as cation mixing,low electronic conductivity and poor stability.However,the highly crystalline materials can reduce cation mixing,primary dispersion particles of sub-micron structure can shorten the diffusion path of lithium ions and electrons,improve the transport capacity of lithium-ions,the surface coating is conducive to stabilize the surface of the materials,improve their cycling performance,and hopefully solve the problems faced by nickel-cobalt-manganese ternary cathode materials:This paper focuses on the synthesis of primary particles of sub-micron NCM523 materials with high crystallinity.Based on the synthesis design of the material,the effect of high crystallinity sub-micron primary particles,and the electrode-coating on the performance of NCM523 material is explored.The specific research contents are as follows:1.The primary dispersion particles of highly crystalline submicron NCM523were prepared by ethanol aqueous solution co-precipitation method combined with solid-phase sintering technology.The effect of sodium carbonate and ammonia water separately added on the structure and performance of NCM523 under different p H conditions was studied in detail.The materials obtained by this method shows excellent cycle performance and rate performance.The NCM523-8 exhibited an initial discharge capacity of 193.6 m Ah g^-1at 0.2 C and the capacity retention was91.25%after 100 cycles in the voltage range of 3.0-4.5 V range.It also delivered superior rate performance with a reversible capacity of 130 m Ah g^-1at 5 C.The enhanced cycle performance and rate performance could be attributed to the perfect crystalline characteristics and sub-micron primary dispersed particles of NCM523.2.In order to improve the performance of the NCM523 materials,NCM523particles with exposure to{010}surface were successfully synthesized.The effect of the mixed dropwise addition of sodium carbonate and ammonia on the structure,morphology and performance of NCM523 under different p H conditions was studied in detail.The results showed that NCM-9 material has dispersed particle composition,with the primary particle size of about 0.3?m.The NCM-9 material has good crystallinity,better lamellar structure and the lowest cation mixing.According to the cyclic volt-ampere?CV?test,NCM-9 has better lithium ion diffusion coefficient(7.523×10^-8cm²s^-1),and its discharge capacity is up to 106.2 m Ah g^-1when the rate is10 C.3.By electrode-coating graphene on the NCM523 electrode,the rate performance and cycle performance of the electrode after coating were significantly improved.After 100 cycles,the capacity retention of composite material G3 coated with 0.5wt%was as high as 99%,while that of uncoated sample was only 74%.