Recycling of cathode materials from spent Li-ion batteries using bio-based reductant: Experimental insights and molecular dynamic simulations

The surging volume of spent lithium-ion batteries (LIBs) from consumer electronics and electric vehicles emphasizes the need for recycling routes that are both high-yield and environmentally benign. Plant-derived reagents can rival conventional H 2 SO 4 /H 2 O 2 systems while eliminating hazardous oxidants and valorizing agricultural residues. This study presents an eco-friendly method for hydrometallurgical dissolution of critical metals from NMC-type LIB black mass using bell pepper extract (BPE) as a bio-reduction. BPE exhibited high antioxidant activity (306.9 ± 1.1 mg Trolox/L) and total phenolic content (228.6 mg gallic acid/L), which play a crucial role in facilitating metal dissolution. Phenolic and flavonoid constituents in BPE donate electrons to reduce Ni, Mn, and Co oxides to their soluble divalent ionic forms via a bio-assisted redox mechanism in acidic media. Process variables were optimized by batch leaching in 2 M H 2 SO 4 . Under optimum conditions (30 vol% BPE, 20 g/L pulp density, 70 °C, 120 min) leaching efficiencies reached 98.7 % Li, 98.9 % Ni, 97.9 % Mn, and 96.1 % Co achieving nearly complete dissolution and yielding two–to–threefold higher efficiencies than conventional acid leaching without BPE. SEM-EDS confirmed that the post-leach residue is essentially metal-free. Density functional theory (DFT) and molecular dynamics (MD) simulations provided mechanistic insights into the interactions between H 2 SO 4 and metal ions (Co 2 + , Ni 2+ , Mn 2+ , Li + ), revealing the role of surface charge density and solvation structure in leaching behavior. Radial distribution functions and coordination number analysis confirmed valence-dependent sulfate complexation and distinct hydration shells, supporting the observed trends in leaching efficiency. • Bell pepper extract (BPE) was used as a novel and eco-friendly reductant for recycling LIBs. • High antioxidant and phenolic levels provide strong reducing power. • 30 vol% BPE + 2 M H₂SO₄ leaches > 96 % Li, Ni, Co, Mn in 120 min at 70 °C. • MD reveals strong, valence-driven sulfate coordination in black mass leachate cations