Abstract: 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·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·g⁻¹ at 10 C, which is higher than that of spent LiFePO₄ (55.9 mAh·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.