A sustainable delamination method to completely separate spent cathode foils via biomass-derived γ-valerolactone

Abstract

Complete and efficient delamination of cathode foil is a pivotal precondition for spent lithium-ion battery (LIB) recycling, determining the realizability of the subsequent operational processes. Current methods are based on the decomposition or dissolution of the polyvinylidene fluoride (PVDF) binder, which eliminates the adhesion between the components and thus results in separation. In this work, the analysis of solubility parameters has inspired the successful application of a green solvent, γ-valerolactone (GVL), for PVDF dissolution and was further utilised to delaminate spent cathode foils for direct recycling. Complete delamination of spent cathode foils was successfully achieved in GVL at 80 °C with 600 rpm stirring, and an ultrasound-assisted strategy was proposed to further improve the separation efficiency. The optimised conditions were determined by orthogonal experiments, with excellent delamination efficiency (99.2%) in the ultrasound-assisted GVL delamination process. Herein, a closed-loop recovery process has been proposed to completely reclaim cathode active materials, Al foil, carbon black, and PVDF binder from spent LIBs without complex treatments. Finally, a tentative exploration of possible delamination mechanisms has been discussed. Economic and environmental analyses based on the EverBatt model confirm the feasibility of its practical applications. This study provides an environmentally benign, highly safe, and sustainable pathway for recycling spent LIBs.