Highly selective metal recovery from spent lithium-ion batteries through stoichiometric hydrogen ion replacement

Spent lithium-ion battery recycling has attracted significant attention because of its importance in regard to the environment and resource importance. Traditional hydrometallurgical methods usually leach all valuable metals and subsequently extract target meals to prepare corresponding materials. However, Li recovery in these processes requires lengthy operational procedures, and the recovery efficiency is low. In this research, we demonstrate a method to selectively recover lithium before the leaching of other elements by introducing a hydrothermal treatment. Approximately 90% of Li is leached from high-Ni layered oxide cathode powders, while consuming a nearly stoichiometric amount of hydrogen ions. With this selective recovery of Li, the transition metals remain as solid residue hydroxides or oxides. Furthermore, the extraction of Li is found to be highly dependent on the content of transition metals in the cathode materials. A high leaching selectivity of Li (>98%) and nearly 95% leaching efficiency of Li can be reached with LiNi_0.8Co_0.1Mn_0.1O₂. In this case, both the energy and material consumption during the proposed Li recovery is significantly decreased compared to traditional methods; furthermore, the proposed method makes full use of H⁺ to leach Li⁺. This research is expected to provide new understanding for selectively recovering metal from secondary resources.