Molecularly Tailored Dual-Function Deep Eutectic Solvent Enhances Spent Lithium-Ion Battery Cathode Delamination and...

Area of Science:

• Materials Science
• Electrochemistry
• Green Chemistry

Background:

• Deep eutectic solvents (DES) show promise for recycling lithium-ion batteries.
• Current DES methods require high temperatures (>120°C) and slow kinetics (>30 min).
• Polyvinylidene fluoride (PVDF) binder presents a challenge in efficient cathode material separation.

Purpose of the Study:

• To design a novel, low-temperature, fast-acting DES for efficient cathode material and current collector separation.
• To investigate the degradation mechanism of PVDF binder using the developed DES.
• To demonstrate the recyclability of cathode materials with high purity and preserved structure.

Main Methods:

• A dual-function DES was synthesized using diethyl (hydroxymethyl) phosphonate (DHP) and malonic acid (MA).
• The DES's efficacy was tested for separating LiCoO2, LiFePO4, and LiNi0.3Co0.3Mn0.3O2 cathode materials.
• Separation efficiency, kinetics, temperature requirements, and material purity were analyzed.

Main Results:

• The DHP-MA DES achieved >99% separation efficiency for LiCoO2 within 15 minutes at 60°C.
• The DES facilitated PVDF binder degradation via nucleophilic attack and hydrogen bonding, reducing viscosity.
• Separated cathode materials showed low impurity content (<0.026 wt%) and minimal metal loss (<2 wt%), retaining their crystal structure.

Conclusions:

• The developed DHP-MA DES offers a highly efficient and low-temperature strategy for recycling lithium-ion battery cathode materials.
• This method enables the recovery of high-performance cathode materials suitable for reuse.
• The findings present a universal approach for sustainable battery recycling.