Sustainable\nRecovery of Bifunctional Electroactive\nMaterial from Process Leach Liquor of Spent Lithium-Ion Battery

This study presents a comparative analysis of Ni-Co rich\noxalate\n(rMOx) and oxide (rMO), developed from process leach liquor of spent\nlithium-ion batteries (LIBs) following an economic and environmentally\nfriendly strategy, as an electroactive material for supercapacitor\nand the oxygen evolution reaction (OER) applications in alkaline media.\nUtilizing a tandem approach, rMOx and rMO were recovered from spent\nLIBs leach liquor, achieving >90% recovery of transition metal\nions.\nrMOx shows a discharge specific capacitance of 220 Fg<sup>–1</sup> at 1 Ag<sup>–1</sup>, surpassing the rMO of 156.5 Fg<sup>–1</sup>. An asymmetric supercapacitor device fabricated to\nanalyze the practical applicability using rMOx and MXene achieved\na discharge specific capacitance of 46 Fg<sup>–1</sup> at 0.8\nmA cm<sup>–2</sup> with energy and power densities of 6.43\nWh kg<sup>–1</sup> and 303.03 W kg<sup>–1</sup>, respectively.\nIn the case of OER, rMOx exhibited an overpotential of 176 mV at 10\nmA cm<sup>–2</sup> and a Tafel slope of 81 mV dec<sup>–1</sup>, outperforming rMO and benchmark electrocatalyst IrO<sub>2</sub>. The superior performance of rMOx can be attributed to its higher\nelectrochemical active center formation due to metal-oxalate to metal-oxy-hydroxide\nconversion during electrode-electrolyte interaction. Thus, this study\npresents a novel approach for establishing electrochemical bifunctionality\nand energy sustainability.