CoAl-N Nanosheets Derived from Spent LiCoO ₂ Cathodes for High-Performance Bifunctional Oxygen Electrocatalysis

The surging worldwide demand for lithium-ion batteries (LIBs) has intensified the depletion of essential transition metals while concurrently producing substantial amounts of hazardous waste, underscoring the need for sustainable recycling strategies. Here, we demonstrate a simple and effective method for transforming spent LiCoO2 (LCO) cathodes into three-dimensional (3D) heterostructured 3D CoAl-N|B nanosheets, which serve as a bifunctional electrocatalyst for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The cobalt-based heterostructures are recovered from LCO leachates via a single-step electrochemical strategy onto a carbon-fiber electrode with tunable composition and nanoscale architecture. Among the developed heterostructured electrodes, the 3D CoAl-N|B nanosheets exhibit remarkable bifunctional activity, achieving an ORR onset potential of ∼0.88 V vs RHE with a high catalytic current density of −0.51 mA cm–2 and an OER overpotential of ∼330 mV at 10 mA cm–2 in 1.0 M KOH. This exceptional performance is due to electronic interactions among Co and Al, and N functionalities, which modulate the local electronic environment, improve the active-site accessibility, and accelerate interfacial charge transfer. The as-developed heterostructured 3D CoAl-N|B nanosheets demonstrate excellent methanol tolerance and long-term operational stability. The present study establishes a circular-economy strategy for redesigning battery waste into efficient oxygen electrocatalysts, providing a scalable and environmentally responsible pathway for next-generation energy conversion and storage systems.