Research On The Recovery And Regeneration Of Waste Lithium Iron Phosphate Cathode Materials

Production and sales of lithium iron phosphate are increasing year by year with the rapid development of electric vehicles and energy storage field due to its advantages of non-toxic,low cost,safety,etc.,and large quantities of spent lithium iron phosphate batteries will be produced.Spent lithium iron phosphate batteries without treatment in time will pollute the environment,and waste a lot of metal resources.In order to protect the environment and achieve the comprehensive utilization of resources,it is necessary to recycle the spent lithium iron phosphate battery.This thesis mainly solves the problems of the long-term recycling process and complicated operation in the existing recycling method of spent lithium iron phosphate.The main research and discussion are as follows:A novel spray drying method is used to replace the precipitation method in order to solve the shortage of the acid leaching-precipitation-solid phase recovery process,such as many control conditions and complicated operation.The oxidic spent lithium iron phosphate is obtained by pretreating the cathode plate.Then the precursor powder is prepared by leaching and spray drying.Finally,the porous spherical LiFePO₄/C is regenerated by a high-temperature solid phase method.The effects of two-stage calcination temperature on the structure,morphology,and electrochemical properties of LiFePO₄ are studied by TG/DSC,XRD,SEM,TEM,and electrochemical detection,etc.The optimal electrochemical performance of LiFePO₄/C material is calcined at650°C.The first specific discharge capacity is 149.4 mAh/g at 0.1 C rate.The capacity retention rate is up to 90.3%after 600 cycles at 1 C rate.The material also has excellent rate performance,and the specific discharge capacities are 129.7 and 107.7mAh/g at 5 C and 10 C rate,respectively.In order to further simplify the recovery process,a solid phase method of mechanochemical activation assisted V⁵⁺doping lithium-iron-phosphate is proposed,and high-performance 1-xLiFePO₄·xLi₃V₂?PO₄?₃/C?1-xLFP·xLVP/C?is prepared.The effect of different vanadium doping contents on the structure,morphology and electrochemical properties of LiFePO₄ is studied by TG/DSC,XRD,SEM,TEM,and electrochemical detection,etc.The regenerated 1-xLFP·xLVP/C?x=0.01?shows uniform particle size distribution,high crystallinity,and optimal electrochemical performance.The initial specific discharge capacity is 154.3 mAh/g at 0.1 C rate.The capacity retention is still 100%after 100 charge/discharge cycles at 1 C rate.In addition,the material has excellent rate performance,and the specific discharge capacities are 121.8 and 104.8 mAh/g at 5 C and 10 C rate,respectively.This study effectively simplifies the recycling process of spent lithium iron phosphate and prepares LiFePO₄/C material with excellent electrochemical performance,which provides a new idea for the recycling of spent lithium iron phosphate battery.