Direct regeneration of fluorine-doped carbon-coated LiFePO4 cathode materials from spent lithium-ion batteries

Abstract

The popularity of LiFePO₄ (LFP) batteries in electric vehicles and energy storage has raised concerns about their disposal and recycling after application. Traditional recycling methods have economic and environmental limitations. Direct recycling is the most promising method. However, irreversible structural degradation and unavoidable impurities hinder the practical application of direct recycling. Here, a sustainable strategy, the methanol–citric acid separation of spent electrode scraps followed by the repair of the separated LFP through the residual polyvinylidene fluoride (PVDF), is proposed for direct recycling. The methanol–citric acid solvent can completely separate the electrode scraps into damage-free spent LFP and non-corrosive Al foil at room temperature. Through the solid-phase sintering method, as the PVDF content is 5 wt% in the spent LFP materials, the crystallinity and microstructure regenerate well, and a fluorine-doped carbon three-dimensional conductive network structure is coated on regenerated LFP particles. The conductive carbon black, which still remains stable in the regenerated LFP, is used again in the battery. The regenerated LFP cathode materials exhibit a good discharge capacity of 141.5 mA h g⁻¹ and a retention rate of 99.6% at 1C after 100 cycles. Our work provides an environmentally friendly and cost-efficient strategy for the recovery of spent LFP.