The preferentially selective extraction of Li+ from spent layered transition metal oxide (LiMO2, M = Ni, Co, Mn, etc.) cathodes has attracted extensive interest based on economic and recycling efficiency requirements. Presently, the efficient recycling of spent LiMO2 is still challenging due to the element loss in multistep processes. Here, we developed a facile strategy to selectively extract Li+ from LiMO2 scraps with stoichiometric H2SO4. The proton exchange reaction could be driven using temperature, accompanied by the generation of soluble Li2SO4 and MOOH precipitates. The extraction mechanism includes a two-stage evolution, including dissolution and ion exchange. As a result, the extraction rate of Li+ is over 98.5% and that of M ions is less than 0.1% for S-NCM. For S-LCO, the selective extraction result is even better. Finally, Li2CO3 products with a purity of 99.68% can be prepared from the Li+-rich leachate, demonstrating lithium recovery efficiencies as high as 95 and 96.3% from NCM scraps and S-LCO scraps, respectively. In the available cases, this work also represents the highest recycling efficiency of lithium, which can be attributed to the high leaching rate and selectivity of Li+, and even demonstrates the lowest reagent cost. The regenerated LiNi0.5Co0.24Mn0.26O2 and Na1.01Li0.001Ni0.38Co0.18Mn0.44O2 cathodes also deliver a decent electrochemical performance for Li-ion batteries (LIBs) and Na-ion batteries (NIBs), respectively. Our current work offers a facile, closed-loop, and scalable strategy for recycling spent LIB cathodes based on the preferentially selective extraction of Li+, which is superior to the other leaching technology in terms of its cost and recycling yield.
Keywords: Li/Na-ion batteries; closed-loop strategy; proton exchange; selective extraction of lithium; spent LIB cathodes.