Selective Lithium Leaching from Spent Lithium-Ion Batteries via a Combination of Reduction Roasting and Mechanochemical Activation

The pretreatment of cathode material from spent lithium-ion batteries is employed for the purpose of selective lithium leaching, which combines reduction roasting with mechanochemical activation without any additives. Under a nitrogen atmosphere (600 °C, 240 min), lithium in the cathode material changes into lithium salts and other metals transform into low-valence/elemental states via intricate reactions between LiMnxCoyNizO2 and inherent carbon. Then, the transition metals at low-valence and elemental states exhibit relatively slow leaching rates in a short time period, while lithium can efficiently migrate into solution. To further optimize this process, mechanochemical activation via ball milling (10 Hz, 30 min) is employed, decreasing the particle size and inducing a transition from crystal to an amorphous phase, facilitating the efficiency of lithium leaching. Under the low-temperature and short-duration leaching conditions (35 °C, 5 min, 2 mol/L H2SO4, 100 g/L), nearly 91.6% lithium is leached out, and the selectivity reaches 92.2%. The lithium solution is further purified by the extractant Versatic 10, and high-purity Li2CO3 is precipitated by adding Na2CO3. This method is also applied to selectively leach lithium from LiCoO2 and LiNiO2 cathodes, achieving remarkable leaching efficiencies of 95.8 and 100%, respectively.