Supramolecular Self-Assembly Enables Controlled Lithium Replenishment Toward High-Performance and Sustainable Regeneration of Spent LiFePO₄ Batteries

With the rapid expansion of lithium–ion battery deployment, spent LiFePO₄ (LFP) regeneration is vital for closing material loops. However, in conventional solid-state regeneration, limited solid–solid contact and the premature formation of a dense conductive carbon layer hinder the effective coordination of lithium replenishment, structural defect repair, and interfacial reconstruction, thereby limiting lithium utilization efficiency and structural restoration. This paper presents a self-assembled supramolecular (SAS) regeneration system spontaneously formed from trithiocyanuric acid (TMT) and lithium acetate (CH₃COOLi). Through Li–S coordination and hydrogen-bonding interactions, the precursor self-assembles into an ordered supramolecular architecture that regulates the thermal evolution of the solid-state regeneration process. Unlike the independent thermal decomposition of mechanically mixed precursors in conventional solid-state regeneration, the ordered supramolecular architecture regulates the reaction sequence, enabling lithium to preferentially enter the LiFePO₄ lattice before the formation of a dense conductive carbon layer, thereby achieving efficient lithium replenishment and structural restoration. Subsequently, an in situ generated N/S co-doped conductive carbon layer elevates interfacial conductivity of regenerated LFP. The regenerated cathode delivers 160.3 mAh g⁻¹ (0.1 C) and 143.0 mAh g⁻¹ (1 C), maintaining 88% capacity over 500 cycles at 1 C, while the pouch cell exhibits 81% capacity retention after 500 cycles at 0.5 C.