A low-toxicity and high-efficiency deep eutectic solvent for the separation of aluminum foil and cathode materials from spent lithium-ion batteries

The separation of cathode materials from aluminum (Al) foil is a key issue worthy of attention in the process of resource utilization of spent lithium-ion batteries (LIBs). Traditional technologies for the Al foil and cathode materials separation have the disadvantages of the use of corrosive acid/alkali, release of HF hazards, and environment and healthy risks of the toxicity reagent. In this study, a low-toxicity, high-efficiency, and low-cost deep eutectic solvent (DES), choline chloride-glycerol, was synthesized and applied to solving the separation dilemma of Al foil and cathode materials in spent LIBs. The experimental results show that separation of the Al foil and cathode materials can be achieved under optimal conditions designed by the response surface method: heating temperature 190 ℃, choline chloride: glycerol molar ratio 2.3:1, and heating time 15.0 min; the peeling percentage of cathode material can reach 99.86 wt%. Mechanism analysis results confirm that the separation of Al foil and cathode materials was the result of the deactivation of the organic binder polyvinylidene fluoride (PVDF), which can be attributed to an alkali degradation process caused by the attack of the hydroxide of choline chloride on the acidic hydrogen atom in PVDF.