Experimental Study On The Mechanochemical Recovery And Regeneration Of Typical Lithium-Ion Battery Cathode Materials

As lithium-ion batteries reach the end of their life span,the stockpile of used lithium-ion batteries continues to grow.There are a large number of valuable metals and organic solvents in the cathode material of lithium-ion batteries,which will cause pollution to the environment and waste of resources if not handled properly.Green,short-range and efficient recovery of the abundant valuable metal resources in them can eliminate the potential hazards to the environment and human health,but also provide raw materials for the production of lithium batteries,reduce the dependence on primary mineral resources and promote the sustainable development of the battery industry.Therefore,the recycling and reclamation of used lithium-ion batteries is of great significance to the efficient use of resources,environmental protection and reduction of lithium-ion battery costs in China,which has become a focus of industry-wide attention at home and abroad.This paper addresses the problems of high acid concentration,high leaching temperature,long recycling process and complicated process when recycling typical waste lithium-ion cathode materials by acid method,and proposes the use of mechanochemical method to recycle waste lithium cobaltate cathode materials,and the leach solution-precipitation-hydrothermal-heat treatment process to regenerate NCM622 cathode materials.The specific research content is as follows:1.The effects of various factors of the mechanochemical method on the leaching rate of cobalt ions were investigated.The results showed that the leaching of cobalt ions was significantly influenced by sulphuric acid concentration,hydrogen peroxide concentration,ball-to-material ratio and solid-to-liquid ratio.The highest leaching rate of cobalt ions was achieved at 95.2%when the sulphuric acid concentration was 0.5 mol/L,the hydrogen peroxide concentration was 2 mol/L,the ball-to-material ratio was 35:1 and the solid-to-liquid ratio was 20 g·L^-1.The response surface method was used to optimise the ball milling time,rotation speed and rotation speed of the single factor of the mechanochemical method,and it was found that the ball milling time had a very significant effect on the leaching of cobalt ions,the rotation speed had a significant effect on the leaching of cobalt ions and the rotation speed had an insignificant effect on the leaching of cobalt ions.The optimum solution was obtained by optimising the ball milling time of 120 min,the stroking speed of 100 r/min and the rotation speed of 468 r/min.After five validation experiments,the leaching rate of cobalt ions was 98.96%.2.The NCM622 cathode material was prepared by hydrothermal precipitation using leachate as raw material.When the transition metal to urea substance ratio was 1:3,the electrochemical performance of the produced cathode material was good and its specific capacity reached 154.4 mAh/g in the first cycle of discharge and the capacity retention rate reached 96.11%after 30 cycles.Its potential differenceΔEp=0.373 V and charge transfer resistance Rct was 38.01?.The regenerated NCM622 cathode material was analysed by means of XRD,SEM and EDS analysis,and it was observed that the regenerated NCM622 cathode material had a goodα-NaFeO₂ layered structure,was relatively intact spherical particles,and the atomic ratios of Ni,Co and Mn were basically in accordance with 6:2:2.