Electrode-to-electrode relithiation of spent LiFePO₄ cathodes

The rapid expansion of the lithium iron phosphate (LiFePO₄, LFP) battery market is creating a growing need for efficient recycling strategies for low-value retired batteries. However, prevailing approaches based on element extraction and materials regeneration often suffer from high energy consumption, substantial environmental burdens, and poor economic profitability, thereby limiting the sustainable development of battery recycling. Here we report an electrode-to-electrode relithiation strategy for the direct regeneration of lithium-loss-dominated spent LiFePO₄ cathodes. By applying an external voltage, electrochemically active Li⁺ can be controllably transferred at room temperature from retired Li-containing electrodes, including spent LiNi_1/3Co_1/3Mn_1/3O₂ (SNCM) and LiFePO₄ (SLFP), to lithium-deficient spent LiFePO₄ cathodes. This process enables accurate lithium compensation and in situ lattice restoration without high-temperature treatment and chemical lithiation reagents. The regenerated LiFePO₄ cathodes show recovered specific capacity, rate capability and cycling stability close to the level of commercial LFP electrodes. This electrode-level route shortens the recycling chain by replacing powder recovery and material resynthesis with direct disassembly, relithiation and cell remanufacturing, thereby preserving more of the structural and electrochemical value of retired batteries.