Regeneration of graphite anode from spent lithium iron phosphate batteries: Microstructure and morphology evolution at different thermal-repair temperature

Recycling of graphite anode from spent lithium ion batteries is critical to the sustainability of the Li-ion battery industry. In this work, the effect of temperature on the microstructure morphology of graphite is studied systematically and the correspondence between the structure morphology and electrochemical properties is elucidated for the first time. The results show that heat treatment leads to the carbonization of organic impurities in spent graphite and the formation of an amorphous carbon layer on the graphite surface. The evolution of the carbon layer from formation to disappearance occurs at different heat-treatment temperatures, which is why the optimal heat-treatment temperature is not the highest heat-treatment temperature. Under optimal conditions, the regenerated graphite exhibits a charging capacity of 339.5 mAh g−1 at 0.1C, and displays a high retention rate of 97.7% after 60 cycles. Our work promotes the regeneration and utilization of spent graphite anode in the industry.