Direct regeneration of LiFePO4 cathode by inherent impurities in spent lithium-ion batteries

Abstract

The direct regeneration method, recognized for its cost-effectiveness, has garnered considerable attentions in the field of battery recycling. In this study, a novel direct regeneration strategy is proposed to repair spent LiFePO4 (S-LFP) cathodes without the need for impurity removal. Instead, the residual conductive carbon and polyvinylidene fluoride (PVDF) in S-LFP are employed as inherent reductive agents. Systematic characterization and analysis reveal that the failure of S-LFP primarily originates from a substantial loss of Li+ and the conversion of LiFePO4 to FePO4. Meanwhile, it is demonstrated that both residual conductive carbon and PVDF play positive roles in promoting the regeneration of S-LFP through distinct mechanisms. As a result, the regenerated LFP exhibits significant recovery in crystal structure and chemical composition as compared to S-LFP, which leads to notably improved lithium storage performance. Furthermore, to further enhance the lithium storage property, a specific amount of glucose (10 %) is introduced during the regeneration of S-LFP, yielding a regenerated product that performs comparably to commercial LFP. Clearly, our approach, in contrast to traditional regeneration methods, maximizes the utilization of residual impurities within S-LFP, resulting in effective regeneration of S-LFP, thereby proving both informative and cost-effective.