Green solvent-based separation and regeneration of layered ternary cathode materials for sustainable lithium-ion battery recycling

Abstract

Direct regeneration serves as a promising approach for recovering layered ternary cathode materials. However, efficient separation of cathode materials from Al foil remains a key challenge for this approach. In this study, LiNi_1/3Co_1/3Mn_1/3O₂ (NCM111) is used as a model material, and a green separation strategy based on Hansen solubility parameters is developed. Using triethyl phosphate (TEP) to separate the cathode electrode sheets, the molecular structure of polyvinylidene difluoride (PVDF) is effectively destroyed at 110 °C, and the separation rate between the cathode material and the Al foil reached 94.1%. The separation mechanism is driven by hydrogen bond competition. Density functional theory calculations confirmed that TEP forms stronger hydrogen bonds with the –OH groups on the Al foil surface than PVDF, promoting its detachment. Additionally, TEP's high dielectric constant and solubility compatibility enhance PVDF dissolution. The recovered cathode material is regenerated using the eutectic molten salt method, with LiOH–Li₂CO₃ eutectic salt as the lithium supplement. The regenerated NCM111 exhibits excellent electrochemical performance, with a discharge specific capacity of 141.4 mAh g⁻¹ at 1C and 86.9% capacity retention after 100 cycles. This TEP-based strategy provides a sustainable and efficient closed-loop recycling solution, offering new insights for the development of environmentally friendly battery recycling technologies.