Efficient recovery of Al foil and regeneration of cathode materials from spent lithium-ion batteries with methanol-citric acid

Abstract

Efficient separation of cathode materials from current collectors is an important step to simplify the recycling process of spent lithium-ion batteries (LIBs). However, traditional methods have the shortcomings of incomplete separation, release of toxic substances and high cost. Here, the methanol-citric acid solvent (MeOH-CA), prepared from green and low-cost reagents methanol (MeOH) and citric acid (CA), can separate above 99.5 wt% of spent nickel-manganese-cobalt (NCM) cathode materials in 15 min with negligible metal loss at an ultralow temperature of 45 °C. The separated NCM has high purity and no structure changes, and the recovered Al foil is intact and non-corrosive. The mechanism analysis indicates that the reaction between MeOH-CA and Al foil and the inactivation of PVDF by the abundant hydrogen bonds in the MeOH-CA solvent cause the separation. Meanwhile, the formation of AlF3 passivation layer and the ester film on the surface of Al foil prevent further corrosion of Al foil. Through hydrothermal treatment combined with a short thermal annealing, the regenerated NCM delivers a reversible capacity of 151 mAh g−1 at 1C and 117 mAh g−1 after 100 cycles. The facile separation strategy provides a sustainable and economic solution for the recovery of spent LIBs.