Study On Regeneration Of Cathode Materials For Waste Lithium Iron Phosphate Batteries Through Metal Ion Doping Modification

With the launch of the country’s energy saving and emission reduction plan aimed at achieving "peak emission" and "carbon neutrality",the application of electric vehicles is increasing rapidly.It is foreseeable that LFP batteries,which are the main types of power batteries,will usher in a peak of obsolescence,and the effective recycle of it has become an issue of great practical significance and social value.In this study,the waste LFP battery was taken as the research object.Based on the principle of positive electrode repair and regeneration technology,the solid-phase regeneration method was optimized through introducing manganese and titanium metal ion doping methods.We thus established a complete treatment process for the regeneration of waste LFP cathode materials through metal ion doping modification,and developed a novel modification method of manganese-titanium co-doping.The appearance,morphology,crystal structure,and electrochemical performance of the regenerated LFP cathode materials obtained by manganese doping,titanium doping,manganese-titanium co-doping,and un-doping,were compared.The influence of doping amount on the appearance morphology,crystal structure and electrochemical performance of the regenerated LFP cathode materials produced by manganese doping,titanium doping and manganese-titanium co-doping was systematically studied,and the corresponding reaction mechanism was discussed.The optimal regeneration process conditions of different doping methods are determined.The modified regeneration process we proposed includes three steps,battery pretreatment,precursor preparation and modified regeneration material preparation.The battery first undergoes a pretreatment step to separate the cathode material.In the precursor preparation stage,the waste LFP cathode material is first supplemented with missing elements to a certain proportion with lithium carbonate as the lithium source,ammonium dihydrogen phosphate as the phosphorus source,and ferrous oxalate dihydrate as the iron source.And then manganese acetate tetrahydrate and/or nano-titanium dioxide were used as doping resources under different doping proportions to prepare precursors by manganese doping,titanium doping,and manganese-titanium doping methods.Finally,these precursors were treated with segmented calcination to form modified and regenerated positive electrode materials.Through the characterization and electrochemical performance measurement of these modified regenerated LFP materials prepared under different conditions,it was determined that the manganese-titanium co-doping at the ratio of Mn=0.02 and Ti=0.03 produces the modified regenerated LFP materials with the best comprehensive performance.The specific capacity of this LFP material during initial charge and discharge reaches 124.6 mAh/g,the 2C rate discharge capacity reaches more than 85 mAh/g,and the capacity retention rate can be retained above 99%after 50 cycles(0.1C).