Selective Lithium Pre-Leaching from Pyrolyzed Industrial Lithium-Ion Battery Black Masses Using Dilute Organic and Inorganic Acids

Selective lithium pre-leaching can separate an accessible lithium fraction before complete black-mass dissolution while limiting the co-dissolution of accompanying elements. However, comparative evidence across compositionally different, industrially pyrolyzed black masses under a consistent operating framework remains limited. To address this gap, three such black masses were systematically investigated using water and dilute inorganic and organic acids (0.1–0.5 mol·L−1, 25–80 °C) without an external reducing agent. Water-leaching experiments were additionally performed to quantify the readily soluble lithium fraction. Lithium extraction after 120 min varied strongly with black mass origin and leaching conditions. Water leaching extracted 12–16% Li from BM1, 24–28% from BM2, and 36–47% from BM3. Under the most favourable water-leaching conditions, transition-metal dissolution remained negligible, resulting in substantially higher selectivity than in most acidic systems. Dilute acids increased lithium extraction in selected experiments, reaching up to 98%, but this was generally accompanied by increased dissolution of Co, Ni, Mn, Cu, and Al. The results demonstrate that lithium accessibility is governed more strongly by feed-specific phase composition and material history than by total lithium content. Selective pre-leaching should therefore be considered a feed-dependent conditioning step whose operating conditions must balance lithium removal against preservation of the transition-metal-rich solid fraction.