Spent-battery-derived Mn-Co-Ni9S8 to achieve industrial-scale current densities for alkaline water splitting

Spent NMC532 cathode is upcycled into an electrocatalyst for water splitting. • CEC leaching enables over 94% recovery of Li, Ni, Mn, and Co from NMC532. • RNMC-S@NF reaches 4 A cm −2 with overpotential of 539 mV for OER and 414 mV for HER. • OER catalysed by RNMC-S@NF follows a LOM mechanism. • Conventional and MOR-assisted OWS reach 4 A cm −2 at 1.98 and 1.60 V, respectively. The disposal of spent lithium-ion batteries (LIBs) is emerging as a serious environmental issue due to the rapid expansion of electric vehicle market. Current recycling routes typically involve recovery of metals as separate metal salts but rarely convert them directly into functional materials, leaving a largely unmet opportunity for value-added utilization of recovered battery metals. In this work, a sustainable strategy is presented for converting spent LIB cathodes into a high-performance, bifunctional electrocatalyst. Briefly, contact electrocatalysis induced metal leachate solution from LiNi 0.5 Mn 0.3 Co 0.2 O 2 was directly used as a metal source along with thiourea to obtain a hierarchical 3D micro-flower sulfide supported on nickel foam (RNMC-S@NF) via hydrothermal process. The optimized RNMC-S@NF catalyst exhibits exciting electrocatalytic activity, requiring overpotentials of 240/539 mV for oxygen evolution reaction (OER) and 107/414 mV for hydrogen evolution reaction (HER) to reach 0.1/4 A cm −2 , respectively. In addition, a symmetrical 2-electrode (RNMC-S@NF||RNMC-S@NF) device requires a low cell voltage of 1.98 V to deliver industrial-scale current density of 4 A cm −2 , significantly outperforming commercial benchmarks of RuO 2 @NF||Pt/C@NF. RNMC-S@NF also shows high activity toward methanol oxidation reaction (MOR), and an MOR-assisted water splitting electrolyzer achieves 4 A cm −2 at a cell voltage of 1.60 V, demonstrating energy-saving hydrogen generation together with high-value formate production. This work not only establishes a scalable route from spent LIBs to industrial-scale green hydrogen, but also offers mechanistic insight into lattice-oxygen-driven OER catalysis and practical guidance for circular-economy battery-recycling policy. Download: Download high-res image (170KB) Download: Download full-size image Metals recovered from NMC532 cathode in spent lithium-ion battery via CEC-assisted leaching are converted into RNMC-S@NF electrocatalyst, driving industrial-scale current densities for efficient hydrogen generation in both conventional and MOR-assisted water splitting.