Reserch On Recycling Of Spent Lithium Cobaltate And Lithium Iron Phosphate Cathode Materials

Spent lithium-ion batteries are containing metal ions and organic electrolyte,which will be harmful to the ecological environment if not treated properly.The content of Li,Co,Fe and other metals in the cathode material is higher than that of the original ore and has significant economic value.In this paper,taking the resource utilization of spent lithium cobaltate and lithium iron phosphate cathode materials as the core,the systems of glycine alkaline slurry electrolysis recovery of spent lithium cobaltate and ionic liquid leaching of spent lithium iron phosphate were constructed respectively,and the reaction mechanisms of slurry electrolysis recovery of spent lithium cobaltate and ionic liquid leaching of spent lithium iron phosphate were analyzed by XRD,SEM,XPS and other characterization techniques.On this basis,the resource utilization methods of spent lithium cobaltate slurry electrolysis products and spent lithium iron phosphate leaching residue were explored.The research contents and main conclusions of this paper are as follows:（1）Conducted research on alkaline slurry electrolysis of glycine to recover spent lithium cobaltate cathode material,and established an alkaline slurry electrolysis system for partial repair of spent lithium cobaltate cathode material and preparation of battery-grade lithium carbonate.Results demonstrated that under the optimal process parameters of solid-to-liquid ratio of 20 g/L,electrolysis time of 8 h,current density of 50 m A/cm²,reaction temperature of80℃,glycine concentration of 1.0 mol/L and Li OH concentration of 2 mol/L,Li₂CO₃ was deposited in the anode area,the recovery of Li was 25%,and the product met the standard of Li₂CO₃（YS/T 582-2013）.The spent Li Co O₂ was partially repaired in the cathode area,Co mainly existed in the form of Co³⁺,the Co³⁺/Co²⁺area ratio increased,the sample particle size became smaller,and the particle surface was smooth.（2）Research on ionic liquid leaching for the recovery of spent lithium iron phosphate cathode materials was carried out,and an acidic system for ionic liquid leaching of spent lithium iron phosphate was constructed.The results showed that under the optimal process parameters of H₂O₂/Li molar ratio of 2.11,leaching time of 4 h,and ionic liquid concentration of 1-butanesulfonic acid-3-methylimidazole bisulfate of 0.05 mol/L,the leaching rates of Li and Fe were 95.5%and 3.1%,respectively,and H₂O₂ has strong oxidizing property under acidic conditions,which promoted the leaching of Li from Li Fe PO₄.The kinetics of ionic liquid leaching of spent lithium iron phosphate was investigated using a contraction kernel model,showing that the rate-limiting step of ionic liquid leaching of lithium is controlled by a combined diffusion-interfacial chemistry reaction with an apparent activation energy of18.607 k J/mol for Li.（3）Conducted research on lithium cobaltate repair and lithium iron phosphate regeneration,and formed a recycling process route for spent lithium-ion batteries.The results revealed that the lithium-cobalt molar ratio of partially repaired Li Co O₂ in the cathode region was adjusted using the slurry electrolytic anode precipitates Li₂CO₃,and the high temperature backfired product was matched with Li Co O₂ standard card（JCPDS#75-0532）.The Li Co O₂ samples with a lithium-cobalt molar ratio of 1.1 were refired at high temperature,and the characteristic crystal surfaces of（003）,（006）and（104）of Li Co O₂ were significantly enhanced,and the specific capacity decayed from 129.9 m Ah/g to 65.58 m Ah/g with a capacity retention rate of50.48%after 100 weeks of cycling.Based on the slurry electrolytic anode deposit Li₂CO₃and spent Li Fe PO₄ leaching residues Fe PO₄ as raw materials,the carbothermal reduction method re-product matches the main peak of Li Fe PO₄ standard card（JCPDS#83-2092）with irregular flakes and clusters in morphology.Results indicated the feasibility of regenerating Li Fe PO₄by carbothermal reduction using leaching residue（Fe PO₄）and Li₂CO₃ as raw materials.