Mechanochemical Activation as a Key Step for Enhanced Ammonia Leaching of Spent LiCoO2 Cathodes

The growing demand for lithium-ion batteries (LIBs) has led to an urgent need for sustainable recycling strategies for spent cathode materials. In this study, a mechanochemical approach was developed for the recovery of lithium and cobalt from end-of-life LiCoO2 cathodes using high-energy ball milling. For the first time, aluminum and carbon were employed as internal reducing agents, facilitating the in situ decomposition of LiCoO2 into CoO, Li2O, and metallic Co. X-ray diffraction analysis confirmed significant structural disorder, phase transitions, and the formation of CoO, AlCo, and spinel-like CoAl2O4. The Taguchi method was applied to optimize milling parameters, identifying 800 rpm, 60 min, and a ball-to-powder ratio of 50:1 as the most effective conditions for structural activation. Subsequent ammonia leaching under fixed conditions (3.0 M NH3·H2O, 1.0 M (NH4)2CO3, 60 °C, 25 mL/g, 6 h) demonstrated high recovery efficiencies: up to 94.6% for lithium and 83.7% for cobalt in the best-performing samples. These results highlight the synergistic benefits of mechanical activation and reductant-assisted phase engineering for enhancing metal recovery. The proposed method offers a simple, scalable, and eco-friendly route for the hydrometallurgical recycling of LIB cathodes without requiring extensive chemical pretreatment.