Turning Waste into Treasure: Directly Utilizing Ternary Lithium-Ion Battery Cathode Waste for an Efficient Oxygen Evolution Reaction through Defect Engineering

In response to the issue of time-consuming reutilization of LiNi1–x–yCoxMnyO2 (NCM) cathode material in waste lithium-ion batteries and to exploit the intrinsically high catalytic activity of Ni, Co, and Mn toward oxygen evolution reaction (OER), we have employed a defect engineering method to directly convert the waste NCM into an efficient OER catalyst. This strategy is achieved through ball milling, during which the oxygen vacancy defects are introduced into NCM powder, and its particle/grain sizes decrease with milling time within 35 h. The introduction of oxygen vacancy defects can increase the number of active sites, modulate the electronic structure, and enhance the conductivity of the NCM sample. The grain refinement increases its electrochemical active area, exposing greater quantities of active sites for the OER catalysis. Such positive impacts are responsible for the excellent OER performance of NCM powder ball-milled after 5 h, which exhibit an overpotential of 362.0 mV at 10 mA cm–2 and a Tafel slope of 87.4 mV dec–1 in a 1.0 M KOH electrolyte, along with good durability. This research offers a novel method of turning waste lithium-ion batteries into treasure for the preparation of economically viable and high-performance catalysts, promoting sustainable energy production based on effective resource recovery.