Regeneration of spent LiFePO4 as a high-performance cathode material by a simultaneous coating and doping strategy

With the number of decommissioned electric vehicles increasing annually, a large amount of discarded power battery cathode material is in urgent need of treatment. However, common leaching methods for recovering metal salts are economically inefficient and polluting. Meanwhile, the recycled material obtained by lithium remediation alone has limited performance in cycling stability. Herein, a short method of solid-phase reduction is developed to recover spent LiFePO4 by simultaneously introducing Mg2+ ions for hetero-atom doping. Issues of particle agglomeration, carbon layer breakage, lithium loss, and Fe3+ defects in spent LiFePO4 are also addressed. Results show that Mg2+ addition during regeneration can remarkably enhance the crystal structure stability and improve the Li+ diffusion coefficient. The regenerated LiFePO4 exhibits significantly improved electrochemical performance with a specific discharge capacity of 143.2 mAh center dot g(-1) at 0.2 C, and its capacity retention is extremely increased from 37.9% to 98.5% over 200 cycles at 1 C. Especially, its discharge capacity can reach 95.5 mAh center dot g(-1) at 10 C, which is higher than that of spent LiFePO4 (55.9 mAh center dot g(-1)). All these results show that the proposed regeneration strategy of simultaneous carbon coating and Mg2+ doping is suitable for the efficient treatment of spent LiFePO4.