Molecularly Tailored Dual‐Function Deep Eutectic Solvent Enhances Spent Lithium‐Ion Battery Cathode Delamination and Regeneration

Abstract

ABSTRACT Deep eutectic solvents (DES) are efficient for separating cathode materials and current collectors from spent lithium‐ion batteries due to their high solubility and tunable properties. However, they suffer from slow reaction kinetics (>30 min) and high‐temperature requirement (>120°C). Herein, a dual‐function DES composed of diethyl (hydroxymethyl) phosphonate (DHP) and malonic acid (MA) with low temperature and faster kinetics was designed. The nucleophilic groups (─OH and alkoxy) on DHP and MA created extensive negative electrostatic potential regions, facilitating the degradation of polyvinylidene fluoride (PVDF) binder at low temperatures. Concurrently, the formed hydrogen‐bonding network weakened intermolecular interactions, reducing viscosity and enhancing mass transfer. For LiCoO 2 , a separation efficiency of >99% was achieved within 15 min at 60°C. Separation mechanism confirmed that PVDF degradation was triggered by the reaction of DHP–MA molecules with H‐atoms, forming solvent channels. Furthermore, with the penetration of H + and MA towards channels, the activation of the corrosion‐passivation reaction brought about the accelerated cathode material detachment. The separated material exhibited low impurity content (<0.026 wt%), minimal metal loss (<2 wt%), and a well‐preserved crystal structure, conducing to the repair of high‐performance materials. Similar results were achieved for LiFePO 4 and LiNi 0.3 Co 0.3 Mn 0.3 O 2 , offering a universal strategy for high‐quality cathode materials recycling.