Epitaxial Regeneration of Spent Graphite Anode Material by an Eco-friendly In-Depth Purification Route

Recovery of spent graphite (SG) anode has been largely overlooked and undervalued due to the difficult regeneration process and the relative low price of graphite compared to valuable elements in the cathode. Moreover, lacking feasible low-cost techniques for the recovery of SG seriously restricts the development of all-component recycling of end-of-life batteries. Here, a novel in-depth purification process via KOH–NaOH composite alkali etching is proposed to eliminate impurities incorporated in SG. Residual acid-insoluble impurities, such as Al- and Fe-related compounds, can be removed effectively by alkali roasting treatment at 180–300 °C. Furthermore, in situ TEM investigation is conducted to unravel the gradual graphitization of the coating layer and the construction of Li+ transport channels between the newly formed structures and the original graphite bulk particles via an epitaxial growth manner during the regeneration process. After optimized purification and regeneration treatments, the recycled graphite can be used suitably as a regenerated anode, and a full cell containing commercial LiFePO4 and recycled graphite shows satisfactory capacity retention of 85.8% after 500 cycles at 1 C. This work demonstrates a promising recyclization route of SG anodes.