Hydrophobic deep eutectic solvents (HDESs) have emerged as promising, low-cost media for the selective recovery of critical metals from waste batteries. In this study, a series of HDESs, composed of various hydrogen bond donors (HBDs) and acceptors (HBAs), were synthesized and evaluated for their ability to extract critical metal ions—Co2+, Ni2+, and Li+—from aqueous solutions. Metal concentrations in the HDES phase were quantified using inductively coupled plasma mass spectrometry (ICP-MS). The solubility of each metal ion in the HDESs was measured across different temperatures to elucidate the thermodynamic and kinetic aspects of metal dissolution. Extraction efficiency was further validated using real NCM (LiNiCoMnOₓ) battery waste. In the meantime, molecular dynamics (MD) simulations were conducted to investigate the hydrogen bonding networks within the HDESs, metal ion diffusion behavior, solvation structures, and the influence of hydrogen bond interactions on metal ion mobility and coordination. This work systematically explores how HDES composition impacts critical metal recovery and offers molecular-level insights to guide the rational design of next-generation deep eutectic solvents for efficient and sustainable battery recycling.
