A Highly Efficient Additive for Direct Reactivation of Waste LiFePO4 with Practical Electrochemical Performance

Recovering the electrochemical performance of waste lithium iron phosphate (LiFePO4) directly under unbroken conditions has become a research topic of great concern. However, there are still severe challenges for the current solid-phase approach in regenerating waste LiFePO4 with unsatisfactory battery performance. Herein, we propose a highly efficient additive of polyvinylpyrrolidone (PVP) to dramatically facilitate the regenerated effect of waste LiFePO4 by a simple mechanical ball milling and calcination process. The microstructures and electrochemical performance of regenerated LiFePO4 were completely repaired. Expectedly, in comparison with new LiFePO4, the battery with regenerated LiFePO4 shows a totally recovered performance of 156 mAh/g at 0.05 C. Such capacity can be strongly maintained at 145 mAh/g even discharged 1 C and a high retention rate of 84.14% after 600. The findings show that the PVP as a dispersant not only can effectively prevent the agglomeration of LiFePO4 particles but also can be used as carbon and nitrogen sources to form the nitrogen-doped carbon capping on the surface of LiFePO4. This work provides a promising route to significantly enhance the electrochemical performance of regenerated LiFePO4 and also highlights the feasibility of a direct regeneration approach for the waste LiFePO4.