Research On The Recovery And Regeneration Of Waste LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Materials

Lithium-ion batteries are widely used in portable electronic products,new energy vehicles,energy storage,military and other fields,because of their high specific energy,low self-discharge rate,and good cycle life.The high nickel series of lithium-ion batteries LiNi_0.6Co_0.2Mn_0.2O₂?NCM622?,have advantages of low price,low toxicity,and high energy density.At present,the demand and output are increasing year by year in the global,that will lead to explosive production of spent ternary lithium-ion batteries.A large number of spent ternary lithium-ion batteries will aggravate the environmental burden,while it contains abundant valuable metal resources.Therefore,it has become an important research to comprehensive recycling of spent lithium-ion batteries.This thesis aim at the traditional acid leaching-metal separation methods in the process of recycling spent ternary lithium-ion batteries problems such as difficult operation,long process,put forward the acid leaching-precipitation method and direct add lithium with coating modification methods to regenerate the ternary lithium-ion battery cathode materials.The main conclusions are as follows:Recycling of spent NCM622 cathode materials by acid leaching-precipitation method.First of all,the influence of acid concentration,reducing agent concentration,solid-liquid ratio,leaching time,and leaching temperature on metal leaching rate of spent NCM622 materials are analyzed by orthogonal experiment.Fnally,under the optimal experimental condition of 3 mol/L sulfuric acid concentration,3 vol%of H₂O₂,solid-liquid ratio of 20 g/L,the temperature is 80°C,the leaching time of 60 min,the leaching rate of Li,Ni,Co,Mn can reach more than 95%.Then use acid leaching solution as raw material,and NCM622 cathode materials are synthesized by carbonate precipitation-high temperature calcination method.The influence of calcining temperature on the electrochemical properties of regen erated materials is studied by XRD,SEM and electrochemical detection,etc.The results showes that the electrochemical properties of the material is the best when the calcination temperature is 850^oC.The discharge specific capacity can reach 173.4 mAh g^-11 at 0.1 C rates,cycling performance with 92.63%capacity retention after 100 cycles.Recycling of spent NCM622 cathode materials by adding lithium and coating modification methods.First,the NCM622 materials are regenerated by direct adding lithium-calcining method.The effects of different lithium supplementation on the electrochemical properties of regenerated materials are investigated by ICP,XRD,SEM and electrochemical test,etc.The results shows that the electrochemical properties of the regenerated materials is best when the amount of lithium added is5%.And then,the NCM622 composite materials are synthesized by Li_1.20Mn_0.54Ni_0.13Co_0.13O₂?LLO?surface modification method.The effects of surface modification on the electrochemical properties of reg enerated materials are studied by XRD,SEM,TEM,XPS and electrochemical test,etc.The results shows that,NCM622@1%LLO active materials discharge specific capacity can reach 178.2 mAh g^-11 at 0.2 C rates,cycling performance with 98.4%capacity retention after 100 cycles.The electrochemical performance of regeneration NCM622 can obviously be improved by Li1.20Mn0.54Ni0.13Co0.13O2 modification.