Microwave assisted recycling of spent Li-ion battery electrode material into efficient oxygen evolution reaction catalyst

Owing to the high utilization of Li-ion battery (LIB) in the industrial sector and subsequent production of waste from cycled LIB endows with the shortage of rare metals and environmental pollution. Herein, we demonstrate an efficient strategy for the conversion of spent LIB for the recovery of valuable metals through a facile microwave-assisted hydrometallurgy technique for the large-scale production of catalysts towards oxygen evolution reaction (OER). After performing a series of recycling procedures with the variation in H₂SO₄ concentration, H₂O₂ dosage, and microwave parameters, the optimum condition for the leaching are 60 ºC, 30 min, 0.5 M H₂SO₄, 50 W microwave power, 3 vol% H₂O₂ to achieve Li: 89.07%, Co: 94.57%, Ni: 94.25% and Mn: 100%. The leaching kinetics is further modeled through a diffusion control mechanism. Further coprecipitation reaction leads to the formation of mixed metal hydroxide containing a majority of α-Co(OH)₂ phase with traces of Ni and Mn. The optimized and recovered α-Co(OH)₂ exhibits pronounced OER activity with an overpotential of 131 mV to achieve 10 mA/cm² current density and Tafel slope of 80.2 mV/dec surpassing all the synthesized mixed metal, commercial Co(OH)₂ and benchmark electrocatalyst (IrO₂). Further, the recovered Co(OH)₂ exhibits pronounced long-term stability with negligible loss (5%) after 50 h of continuous OER. The recycling strategy using the microwave technique provides a pathway for low-cost recycling of waste material for the large-scale production of efficient electrocatalyst towards a sustainable future.