Efficient regeneration of retired LiFePO4 cathode by combining spontaneous and electrically driven processes

Abstract

Recycling retired lithium-ion batteries (LIBs) is critical for global environmental sustainability and significant to closed-loop utilization of future resources, whereas existing regeneration technologies have possessed numerous flaws, such as high chemical cost, large energy consumption, secondary pollution, and security concerns. Herein, we propose a consecutive resting-output current embedding-lithium process to recover retired LIBs. Specifically, the spent LiFePO₄ (LFP) cathode materials can be directly regenerated via a widely applicable aqueous electrolysis process combined with spontaneous lithium migration, driven by concentration polarization, and targeted electrically-driven lithiation, which possesses advantages in reaction time and current utilization efficiency. Besides, lithium salts in the whole process are recyclable, and no side reaction occurs. Furthermore, detailed electrochemical kinetic analysis under different processes, tested by electrochemical impedance spectroscopy (EIS) and Tafel, illustrates that both the pre-liquid phase transfer step and electrochemical reaction process dominate the lithiation rate in the rest process, then taken over by the chemical reaction step after applying the output potential. Benchmarking analysis presents that a high current utilization efficiency (more than 90%) is maintained during output current, proving the significant economic advantages of the method, and the regenerated LiFePO₄ cathode displays an excellent discharge capacity of 135.2 mA h g⁻¹ at 1 C, with a capacity retention rate of 95.30% after 500 cycles.