Indigenous bioleaching strain enables efficient leaching of lithium, nickel, cobalt, and manganese from spent lithium-ion battery

• Two-step bioleaching outperforms one-step for black mass from spent LIBs. • A. ferriphilus is identified as a promising alternative to A. ferrooxidans strains. • Indigenous strain A. ferriphilus 9P1 exhibits the fastest leaching rate within 24 h. • 9P1 shows 59% Li, 42% Ni, 52% Co, and 68% Mn leaching efficiencies at 100 g/L (P/D). • Higher Eh and Fe 3+ /Fe 2+ indicate enhanced microbial activity in two-step bioleaching. The rapid growth of lithium-ion batteries (LIBs) usage led to a large accumulation of spent LIBs, raising concerns about environmental pollution and critical resource supply. Bioleaching is regarded as an eco-friendly strategy for recovering valuable metals such as lithium (Li), nickel (Ni), cobalt (Co), and manganese (Mn) from black mass, a pretreated spent LIB residue. However, its industrial deployment remains limited, primarily due to microbial inhibition by toxic metals under high pulp density (P/D) conditions. Here, we report the discovery and application of a novel indigenous single strain, Acidithiobacillus ferriphilus (9P1), which demonstrates unprecedented bioleaching performance at a high P/D of 100 g/L. Comparative tests with three indigenous strains and a reference strain ( Acidithiobacillus ferrooxidans , KCTC 4516) revealed that 9P1 achieved the highest leaching efficiencies of 77% for Li, 47% for Ni, 53% for Co, and 87% for Mn within only 24 h at 100 g/L. Furthermore, the two-step bioleaching strategy significantly enhanced microbial activity, as evidenced by higher redox potential (Eh) and Fe 3+ /Fe 2+ ratios compared to the one-step process. Our findings provide the demonstration of a robust indigenous strain that enables efficient multi-metal recovery from spent LIB black mass under industrially relevant high P/D conditions. This study not only establishes a bioleaching strategy that overcomes the critical challenge of low efficiency but also underscores its promise as a scalable and sustainable technology for LIB recycling.