Research On Recycling And Regeneration Of Waste Ternary Cathode Materials

With the development of new energy vehicles,consumer electronics,smart products in the market,as well as the rapid iterative upgrade of battery product technology,used batteries were showing explosive growth.The development of waste lithium-ion battery recycling technology is important to protect the environment and save resources.Among the many types of lithium-ion batteries,the ternary lithium-ion battery contained a variety of valuable metal elements and has high recycling value.In this paper,the waste ternary cathode material was taken as the research object,efficiently recycled and reused.In this paper,a combination of pyrometallurgy and hydrometallurgy was used for recycling.First,the waste ternary cathode material was pyrolytically reduced,and the lattice of the waste was destroyed to remove lithium.The waste ternary cathode material was reduced to a mixture of metal elements and metal oxides.Secondly,the reduction product was subjected to leaching and recovering lithium elements.Then the washed product was subjected to acidolysis,Fe and Al impurity elements in the reducing material were removed.Finally,the ratio of nickel,cobalt,and manganese in the salt solution after impurity removal was adjusted,the ternary precursor Ni_0.5Co_0.2Mn_0.3（OH）₂was regenerated.The Ni_0.5Co_0.2Mn_0.3（OH）₂was calcined into a ternary cathode material Li Ni_0.5Co_0.2Mn_0.3O₂,and its morphology and electrochemical performance were tested to determine the reliability of the recycling method.（1）According to the TG-DSC comprehensive thermal analysis method and the XRD and SEM images of the reduction products,it can be seen that the waste ternary cathode materials undergoed self-decomposition and reduction reactions under the natural gas atmosphere in the temperature range from 550 to 750,the reactions mainly produced Li₂O,Ni O,Ni,Co O,Co and Mn O.The mixture of Li₂O,Ni,Co and Mn O was mainly formed at 800℃.（2）The optimal lithium leaching conditions were obtained by the single-factor control variable method.The leaching time was 1 h at room temperature,the solid-liquid ratio was1:4,and the number of times of water immersion was twice.Under these conditions,the lithium leaching rate was 95.5%;The lithium element in the liquid was recovered in the form of Li₂CO₃,and the optimum recovery temperature was 80°C.Under this condition,the lithium recovery rate was 63.5%,and the purity of the crude Li₂CO₃ is 95.2%.（3）According to the thermodynamic calculation and analysis,the hydrolysis precipitation p H range of Al³⁺,Fe³⁺,Ni²⁺,Co²⁺,Mn²⁺were determined,and the optimal impurity removal conditions were determined by experiment.Solution p H was 4.6,reaction time was 1h,reaction temperature was 70℃.Under these conditions,the removal rates of aluminum and iron were 99.67%,99.72%,and the loss rates of nickel,cobalt,and manganese were 5.84%,2.17%,and 2.25%,respectively.（4）According to the XRD and SEM patterns of the regenerated precursor and the regenerated cathode material,they had good crystallinity and no other impurity phases were observed,but the degree of cation mixing was high and the layered structure was poor.In terms of electrochemical tests,the capacity retention rate was 71%after 50 cycles at a rate of0.5C,and the coulombic efficiency was above 98%.The first charge specific capacity reached 136.9m Ah.g-1,and the discharge specific capacity was 98.62m Ah.g-1.