Fig. 1. Acid-extractable battery metals in black mass.

(A) The HCl-extractable battery metal contents (1 M HCl, 50°C) and the total quantification of battery metals (aqua regia, 50°C) in various black mass types (BM-1 to BM-7; Table 1), and the recovery yield (Y₀) of the battery metals from black mass by 1 M HCl. The error bars reflect the standard deviations (SDs) from at least three individual measurements. The same below. (B) pH-dependent leachability of lithium and transition metals [HCl(aq), 50°C] from BM-1. (C) High-resolution Co 2p spectra of BM-1 and raw LiCoO₂. The dashed line shows the position of the Co peak in LiCoO₂ for comparison. a.u., arbitrary units. (D) Gibbs free energy of dissolution for metals and their corresponding metal compounds in 1 M HCl. (E) High-resolution C 1s spectrum of BM-1. (F) Scanning electron microscopy (SEM) image of BM-1. Scale bar, 10 μm. (G) Ellingham diagram of carbon monoxide and various metal oxides. The dashed line denotes the FJH temperature at ~2120 K. (H) Vapor pressure–temperature relationship of various battery metals and carbon. AqR, aqua regia; TM, transition metals.