Investigation On Selective Delithium Of Waste Ternary Cathode Materials And Exploration On Regeneration Of Ternary Cathode Materials

The new energy vehicle industry is developing vigorously,and the market scale of lithium ion battery is expanding year by year.The importance and urgency of recycling spent lithium ion battery is becoming increasingly prominent.In this paper,the recycling route of spent ternary cathode materials based on electrochemical method is proposed.By constructing different electrolyte system,the selective leaching process of lithium form the spent ternary materials with the corresponding system is investigated,and the similarities and differences as well as the advantages and disadvantages between different electrolyte system are illustrated,and the extraction mechanism and the evolution of the material structure,morphology and valence state are revealed.Besides,using the delithiated material as the precursor,the regeneration of ternary cathode material is studied,thereby realizing the efficient and green recycling of spent ternary cathode materials,and contributing to the further development of spent lithium ion battery recycling industry.（1）Based on the electrochemical recovery system of sodium chloride electrolyte,the selective leaching of lithium from spent ternary cathode materials(Li Ni_0.55Co_0.15Mn_0.3O₂)is studied.With the electrolytic approach of constant current followed by constant voltage,the maximum extraction rate of lithium can reach 95%,and leaching rate of the transition metals are less than 0.2%,which exhibits excellent selective leaching result of lithium.With the help of XRD,SEM and XPS,the structure of the delithiated materials（x=0.95）is determined to be Ni O₂ structure of hexagonal crystal system and（?）m space group,and its morphology is primary particles dispersed from secondary particles,and the valence state of transition metal oxides is dominated by+4.（2）Based on the electrochemical recovery system of chloride electrolyte,the selective leaching of lithium from spent ternary cathode materials(Li Ni_0.55Co_0.15Mn_0.3O₂)is studied.With the electrolytic approach of constant current followed by constant voltage,the maximum extraction rate of lithium is up to 90%,and the leaching rate of the transition metals are less than 0.2%,which exhibits excellent selective leaching result of lithium,but the maximum extraction rate of lithium is about 5%lower than that of sodium chloride electrolysis system.Via XRD,SEM and XPS,the phase of the delithiated materials（x=0.90）is determined to be the the H3phase and the Ni O₂ phase,and its morphology is primary particles dispersed from secondary particles,and the valence state of transition metal oxides is dominated by+4.（3）Based on the delithiated materials from the sodium chloride electrolysis system,its regeneration process to obtain electrode materials is studied.Using the insufficiently delithiated materials（x=0.65）as precursors,the maximum discharge capacity of the regenerated electrode materials through the two-stage roasting,can reach 140.5 m Ah g^-1,with a capacity retention of 75.8%after 100 cycles.Using the delithiated materials（x=0.95）after hydrothermal pretreatment as precursors,the maximum discharge capacity of the regenerated electrode materials through the two-stage roasting,can reach 148.3 m Ah g^-1,with a capacity retention of 87.9%after 100 cycles.