Direct Liquid-Phase Regeneration of Eluting Spent LiFePO₄ Upgrade for Fast-Charging Cathodes Under Low Temperature and Ambient Pressure

With the widespread adoption of lithium iron phosphate (LiFePO₄, LFP)-based power batteries, it is anticipated that a huge volume of spent LFP cathodes will be generated in the near future. Therefore, it is imperative to develop advanced, ecofriendly, and efficient recycling technologies for spent LFP cathodes. In this work, a low-temperature direct hydrothermal regeneration strategy with a rapid eluting process is introduced for the spent LFP cathodes. This regeneration strategy can effectively achieve multiple goals, including supplementing Li⁺ ions, eliminating irreversible phase transitions, maintaining the bulk initial structure, and repairing the evenly carbon-coated layer. Moreover, the regenerated LFP can induce the formation of a thinner and more uniform CEI film during the initial charge-discharge process, achieving a fast Li⁺ ion diffusion rate, enhanced discharge capability, and improved structural stability. Thus, the regenerated LFP exhibits a high initial discharge capacity of 164.2 mAh g^-1 at a 0.1 C rate with an initial Coulombic efficiency of 98% and 132 mAh g^-1 at 5 C with a remarkable capacity retention rate of 93.1% after 800 cycles. Specifically, this direct regeneration method is shorter in process and lower in cost compared with the traditional hydrometallurgy, enabling an eco-friendly regeneration under a mild environment, which shows a huge development potential in industrial applications.