Recycling and crystal regeneration of commercial used LiFePO4 cathode materials

Abstract

Currently extensive attentions on recycling application from scrapped LiFePO4 power batteries of electric vehicles is attracted to the researchers. Owing to its stable olivine crystal structure and expensive preparation process relative to other cathode materials, the re-synthesis of LiFePO4 from spent batteries becomes an economical and convenient way. Herein, we combine the mechanical separation and high-temperature pyrolysis to regenerate the performance of used LiFePO4 cathode materials from retired electric vehicles. Spent LiFePO4 cathode material is first successfully regenerated through Li/Fe/P elements compensation and structure reshaping via heat treatment method. The results show that when the content of Li/Fe/P elements in the used LiFePO4 material is restored to the initial conditions, the surface and particle sizes of the material are recovered to smooth and small, respectively. From the crystal structure, the crystal distortion of the used LiFePO4 material is also repaired, indicating by the restored interplanar spacing of the (111) plane and the improved crystallinity. With the successful repair of microstructures and components, the electrochemical performance of the repaired LiFePO4 is reverted, such as long cycle and rate performance, when compared with the used LiFePO4.