Black mass impurities effect on re-synthesized NMC811 by carbonate coprecipitation

The rapid expansion of electromobility and renewable energy storage has increased lithium-ion battery production, emphasizing the need for efficient end-of-life management and critical material recovery. Mechanical pretreatment of spent batteries yields a black mass containing valuable oxides and metallic impurities, primarily Al, Cu, and Fe. This study investigated the impact of Al 3+ , Cu 2+ and Fe 2+ impurities on the carbonate coprecipitation synthesis of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) precursors to simplify cathode resynthesis from acid leachate. Electrochemical testing showed improved performance for NMC811 materials doped with 1–3 at% Al 3+ , 2 at% Fe 2+ , or co-doped with Al–Fe at total concentrations of 2–4 at%, compared to undoped NMC811. Rietveld refinement of XRD patterns revealed reduced Li + /Ni 2+ cation mixing in these same concentrations, confirming structural stabilization. In contrast, Cu 2+ doping beyond 1 at%, whether alone or in combination, did not yield additional benefits and instead led to increased disorder. These findings suggest that leachates containing up to these impurity levels could be used directly in resynthesis without further purification, as the resulting NMC811 retained equal or improved performance. This supports a more sustainable and resource-efficient recycling process by reducing water, reagent, and energy consumption. • Impurity-tolerant recycling saves reagents and energy for greener NMC811 resynthesis. • Controlled Al 3+ and Fe 2+ content can enhance structural & electrochemical stability. • Cu impurities above 1 at% impair capacity and structural ordering in NMC811. • Al–Fe co-doping improves NMC811 rate capability and cycling stability.