Enhancing the depressed initial Coulombic efficiency of regenerated graphite anodes via the surface modification of a TiNb2O7 nanolayer

Spent graphite (SG) anodes are extensively overlooked despite being a potential anode material on account of their relatively low cost when compared to the valuable metal elements of cathode materials . However, the cracked surface structure and unstable solid electrolyte interphase (SEI) of SG will lead to depressed initial Coulombic efficiency (ICE), which hampers the application of graphite recovery techniques. Here, a uniform layer of TiNb 2 O 7 nanoparticles is successfully constructed on a damaged SG surface. Benefiting from the stable structure, the TiNb 2 O 7 coating can effectively protect the cracked sites and enhance Li +  diffusion. In addition, this layer can provide a high Li +  insertion potential and effectively suppress the unfavorable formation of an unstable SEI. The TiNb 2 O 7 coating can also provide extra capacity, compensating for the capacity fade of SG. After modification, the regenerated graphite not only exhibits enhanced rate performance by means of reconstructed Li +  transfer channels but also demonstrates a prolonged cycle life due to the stabilized bulk structure. A full cell containing LiFePO 4 and a regenerated graphite anode shows a high capacity retention, namely, 89.0% after 500 cycles at 1C. This study obtains regenerated graphite with a high ICE, thereby promoting the reutilization of spent graphite anodes.