Pitting Corrosion Mechanism-Driven Cathode Exfoliation for Enhanced Direct Regeneration from Spent Lithium-Ion Batteries

Exfoliating the cathode material from Al foil can significantly enhance the recycling efficiency of spent lithium-ion batteries (LIBs). Herein, we propose a green, low-cost, and efficient method for this exfoliation process. Ultralow-concentration organic acids (0.1 M malic acid or 0.025 M citric acid) efficiently exfoliate 99.9% of cathode material from Al foil at room temperature (∼25 °C) within 20 min, resulting in the recovery of high-purity cathode materials and intact Al foil. This process relies on the ionization of organic acids to create a mildly acidic environment, which disrupts the binder–Al foil interactions via the pitting corrosion of the Al2O3 layer. Key factors that contribute to the success of this exfoliation process include the dissociation constant (pKa) and the concentration of the organic acid. An organic acid with a moderate pKa and a low concentration is essential for effective exfoliation without destroying the crystal structure of the cathode material. Due to the ultralow concentration of organic acid and short exfoliation time, cathode material dissolution is negligible. Additionally, the organic acid solution is reusable, and the exfoliated cathode materials are suitable for direct regeneration. This approach, characterized by its low cost, ambient operation, nontoxicity, and high efficiency, offers a promising method for the direct recycling of spent LIBs.