Sustainable Recovery of Bifunctional Electroactive Material from Process Leach Liquor of Spent Lithium-Ion Battery

This study presents a comparative analysis of Ni-Co rich oxalate (rMOx) and oxide (rMO), developed from process leach liquor of spent lithium-ion batteries (LIBs) following an economic and environmentally friendly strategy, as an electroactive material for supercapacitor and the oxygen evolution reaction (OER) applications in alkaline media. Utilizing a tandem approach, rMOx and rMO were recovered from spent LIBs leach liquor, achieving >90% recovery of transition metal ions. rMOx shows a discharge specific capacitance of 220 Fg^–1at 1 Ag^–1, surpassing the rMO of 156.5 Fg^–1. An asymmetric supercapacitor device fabricated to analyze the practical applicability using rMOx and MXene achieved a discharge specific capacitance of 46 Fg^–1at 0.8 mA cm^–2with energy and power densities of 6.43 Wh kg^–1and 303.03 W kg^–1, respectively. In the case of OER, rMOx exhibited an overpotential of 176 mV at 10 mA cm^–2and a Tafel slope of 81 mV dec^–1, outperforming rMO and benchmark electrocatalyst IrO₂. The superior performance of rMOx can be attributed to its higher electrochemical active center formation due to metal-oxalate to metal-oxy-hydroxide conversion during electrode-electrolyte interaction. Thus, this study presents a novel approach for establishing electrochemical bifunctionality and energy sustainability.