Direct regeneration of spent LiFePO4 cathode via a mild deep eutectic solvent process

With the rapid development of energy storage devices and electric vehicles over the past decades, a large amount of lithium iron phosphate (LiFePO 4 , LFP) batteries are going to retire. Instead of recycling the low value Fe and P elements, direct regeneration of LiFePO 4 cathode has been recognized as the most cost-effective way to deal with the spent LiFePO 4 (S-LFP) batteries. However, the regeneration methods for S-LFP reported so far suffer from either using complex pre-oxidation and high temperature sintering steps, or expensive organolithium salt, which will inevitably increase the regeneration cost and give rise to additional environmental pollution. Herein, a deep eutectic solvent (DES) composed of lithium iodide, urea, and ascorbic acid (referred to as IUA) as prepared at 80 °C in ambient atmosphere is employed to regenerate S-LFP. This DES creates a Li-rich and reductive environment, enabling it to simultaneously supplement the deficient Li + ions, reduce Fe 3+ ions, and rectify the Fe Li “anti-site” defects in S-LFP under ambient pressure and optimally at 100 °C for 10 h. The regenerated LiFePO 4 demonstrates excellent electrochemical performance, with a high discharge capacity of 160 mAh g −1 at 0.1C and a remarkable capacity retention ratio of 85.8 % even after 400 cycles at 1C. Furthermore, the utilized IUA can be refreshed and reused for subsequent rounds of S-LFP regeneration. This characteristic renders the DES regeneration process both environmentally friendly and economically advantageous, thereby holding great promise for the practical recycling of S-LFP batteries.