Study Of Synthesis Amplification And Modification For Ni-rich Ternary Material In Lithium Ion Battery

With the rapid development of the matket for power battery,cathode material of battery has been becoming one of the main directions for industrial scale researches.And the Ni-rich Li Ni_0.8Co_0.1Mn_0.1O₂ oxide material,which can show high discharge specific capacity(200 m Ah g^-1)and be low-cost,is becoming the the next pivotal frontier of industrialization.From now on,the most common and developed synthesis method of Nirich ternary material is that the precursor of using ternary material is synthesized via coprecipitation firstly,then the precursor mixed with lithium is calcined under high temperature,which could obtain the powder with controllable size distribution,high tap density and spherical ternary cathode material.After years of small studiesies in laboratory,reserachers have found the conditions to control the tap density and particle diameter,and researched some critical factors such as temperature,p H value,ammonia/total metal ion feeding ratio and so on,which adjust the primary partical,packing density and tap denstity.What’s more,our group has explored the stable technology and prepared high tap density(ρ>2.1 g cm^-3)processor,and has the conditions for synthesis amplification of precursor.This thesis was in the point of view of the industrialization,using co-precipitation method to have research on synthesis amplification,studied on the tap dengsity and partical size for Ni_0.8Co_0.1Mn_0.1（OH）₂ from the perspectives of cristal nucleation and growth separately.Through the enlarged tank reactor,effects of base solution amount on primary nucleation and agglomeration was studied,which particularly analyzed the influence factors of stirrer paddle,solid-liquid ratio,crystal size and mixing speed on secondary nucleation.Moreover the impacts of mixing speed,stirrer paddle,solid-liquid ratio and reaction time on the cristal growth.Based on the deceloped small-scale technology in lab,we aimed at the phenomena such as constant nucleation,low tap density and changed partical size,which were casused by mixing problems.and designed new technology to have got the high tap density(ρ=2.04 g cm^-3),small-sized precursor,whose rate and cycling performance are superior to the commercial material.To the industrialization of Ni-rich ternary material,one of the essential problems is too alkaline,which also has bad effects on the performace of the cathode material.In order to solve the problem,this thesis propose a washing process tu reduce the residual lithium compounds on surface of LNCM material via protonated polyaniline（PANI）,which improved the diffusion of lithium ions and electronic conductivity for active material without any harmful effect on the structural integrity.In addition,this method would not decrease the discharge capacity and make capacity loss,promoting the rate and cycling performance for Ni-rich ternary material overall.What’s more,PANI could be coated on the surface during the washing process,and function as the protection layer to further enhance the cycling stability.