Utilizing waste lithium-ion batteries for the production of graphite-carbon nanotube composites as oxygen electrocatalysts in zinc–air batteries†

The increasing global demand for energy has led to a rise in the usage of lithium-ion batteries (LIBs), which ultimately has resulted in an ever-increasing volume of related end-of-life batteries. Consequently, recycling has become indispensable to salvage the valuable resources contained within these energy storage devices. While various methods have been developed for the recovery of valuable cathode metals from spent LIBs, the anode's active material, graphite, is mostly lost from circulation. This study introduces an innovative method to valorize black mass leach residue, a waste product from industrial hydrometallurgical LIB recycling processes. Predominantly composed of graphite and minor metal residues, this material can be converted into a valuable bifunctional oxygen electrocatalyst. This transformation is achieved by doping the leach residue with nitrogen and through the incorporation of carbon nanotubes into the modified matrix, to enhance the surface area and conductivity of the produced electrocatalyst. These novel catalyst materials can enhance the oxygen reduction reaction and oxygen evolution reaction in zinc–air batteries (ZAB). The best catalyst material exhibited a commendable power density of 97 mW cm⁻² in ZAB, demonstrating stable performance over 70 hours of continuous charge–discharge cycling. This research represents a significant advancement in the shrewd utilization of LIB recycling waste, which further enhances the goal of closed-loop materials circularity.