Selective leaching of Li from spent LiNi0.8Co0.1Mn0.1O2 cathode material by sulfation roast with NaHSO4‧H2O and water leach

Extensive research efforts have been made in recycling spent lithium-ion batteries; however, there has been little focus on the selective recovery of lithium from spent lithium-ion batteries. In this paper, we report a new process for selective extraction of lithium from spent lithium-ion power batteries by roasting a mixture of LiNi0.8Co0.1Mn0.1O2 and NaHSO4·H2O followed by water leaching. The most suitable conditions included roasting LiNi0.8Co0.1Mn0.1O2:NaHSO4·H2O at 600 °C for 30 min in a mass ratio of 1:1.40, followed by water leaching at 60 °C for 30 min with a liquid/solid ratio of 25:1 (mL/g). Under the optimal conditions, extraction efficiencies of 99.3%, 0.01%, 3.69%, and 3.90% for Li, Mn, Co, and Ni, respectively, were obtained. X-ray diffraction, in situ X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry–differential scanning calorimetry, and thermogravimetry–mass spectrometry were performed to investigate the transformation of Li, Ni, Co, and Mn in the LiNi0.8Co0.1Mn0.1O2–NaHSO4·H2O roasting system. The results demonstrated that the SO3 produced by thermal decomposition of NaHSO4·H2O considerably affected the transformation of Li, Ni, Co, and Mn in the LiNi0.8Co0.1Mn0.1O2. The surface morphology of the roasted samples showed evidence of sintering and agglomeration. The thermodynamic analysis indicated that the roasting reaction is feasible and that the selective extraction of Li can be achieved by controlling the additive ratio of NaHSO4·H2O.