One-step redox-flow desalination for simultaneous separation of lithium, nickel, and cobalt

초록

The rapid growth of lithium-ion batteries (LIBs) has intensified the demand for sustainable recycling approaches to recover valuable metals and reduce environmental risks. Electrochemical separation technologies have emerged as attractive alternatives to conventional hydrometallurgy, but most existing strategies rely on single ion targeting or sequential, multi-stage processing, limiting their scalability. Here, we present a single-cell redox-flow desalination (RFD) system that simultaneously separates Li+, Ni2+, and Co2+ in one step. The design integrates two complementary mechanisms: a cation-exchange membrane (f-CEM) functionalized with PAH/PSS multilayers, which enables Li+ transport while repelling divalent cations, and EDTA-assisted chelation that converts Ni2+ into NiY2− for selective transport through an anion-exchange membrane (AEM), leaving Co2+ in the central chamber. Key operating parameters were systematically evaluated, including applied current (10–200 mA), electrolyte concentration (50–200 mM), and EDTA:Ni molar ratio (0–1.2). Under optimized conditions, recoveries reached 98.3 % for Li+, 78.0 % for Ni2+, and 77.3 % for Co2+, with low specific energy consumptions of 0.9 kWh mol−1 (Li+) and 1.2 kWh mol−1 (Ni2+). The system maintained performance with synthetic battery leachates, demonstrating tolerance to realistic ionic strength and composition. This compact and integrated RFD provides a scalable pathway for simultaneous multi-ion fractionation, reducing chemical consumption and process complexity, and supporting closed-loop LIB recycling in a circular economy.

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