Mechanochemical upcycling of Li-ion battery leaching residues into core–shell bifunctional catalysts for flexible zinc–air batteries

Converting spent lithium-ion batteries (LIBs) into functional electrocatalysts provides an efficient route to turn battery waste into high-value materials. Herein, an efficient waste-to-value route is reported to convert leaching residues from spent LIBs into bifunctional electrocatalysts that promote both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in zinc–air batteries. Transition-metal species in the residues are transformed into core–shell nanoparticles anchored by nitrogen dopants on graphite substrate. Nitrogen incorporation generates abundant metal–nitrogen coordination environments, which stabilize and expose Ni/Fe/Co active sites and promote the formation of a core–shell architecture. As-synthesized catalysts exhibit outstanding bifunctional activity, with a half-wave potential of 0.93 V for ORR and an OER overpotential of only 310 mV at 100 mA cm⁻², together with excellent durability in alkaline media. The flexible zinc–air batteries are assembled by using residue-derived material as the air cathode catalyst, delivering a peak power density of 94.87 mW cm⁻² with stable cycling performance. This work provides a practical strategy for producing low-cost and durable bifunctional electrocatalysts from retired LIB residues for zinc–air batteries.