Selective lithium recovery from LFP-Type black Mass: Comparative evaluation of inorganic and organic acid systems...

The rapid growth of lithium iron phosphate (LiFePO₄, LFP) batteries in electric vehicles has intensified the need for efficient and sustainable recycling. This study systematically compares five acid-oxidant systems, H₂SO₄, HCl, HNO₃, H₂C₂O₄, and CH₃COOH, for selective lithium recovery from spent LFP black mass under constant-pH leaching conditions. The effects of pH, temperature, and H₂O₂ concentration were evaluated using a statistically designed framework. Characterization by SEM-EDX, Raman spectroscopy, XRD, and ToF-SIMS confirmed that the feed consisted of crystalline LiFePO₄ and graphitic carbon phases with Li- and F-enriched surfaces. All systems achieved high Li extraction (>95%) under optimized conditions, but selectivity depended on acid chemistry and oxidation potential. Sulfuric and hydrochloric acids enabled near-complete Li recovery, with HCl showing superior selectivity (Li:Fe > 100) at 38 °C. Nitric acid alone exhibited limited oxidative strength, but addition of H₂O₂ significantly improved efficiency. Oxalic acid dissolved Li completely but lacked selectivity due to ferrioxalate complexation. Acetic acid delivered the best overall performance, achieving 96% Li recovery with negligible Fe (<0.1%) and minimal P (3%) dissolution at pH 4.3 and 25 °C. Cost analysis showed that while sulfuric acid is least expensive, acetic and hydrochloric acids offer the best balance of selectivity, efficiency, and safety. This study provides a unified framework for evaluating leaching systems and demonstrates that selective lithium recovery from LFP can be achieved under mild, low-acid conditions with minimal environmental impact.