Effect of pyrolysis pretreatment combined with micro-nanobubbles on the eco-friendly recycling of spent lithium-ion batteries

In recent years, there has been a growing emphasis on the recovery of cathode and anode active constituents extracted from spent lithium-ion batteries (LIBs) due to their significant value and technological importance. Prior to the flotation separation of spent LIBs, pyrolysis pretreatment plays a critical role in the removal of organic binding components from the particle surface. However, the presence of residual impurities on the material's surface can hinder the flotation process. This study proposes an environmentally friendly approach to recycling spent LIBs by combining pyrolysis with grinding, ultrasonic treatment, and micro-nanobubbles (MNBs), utilizing the electrode active materials from the batteries as raw materials. Various analytical techniques, including X-ray Diffractometer (XRD), Field-emission Scanning Electron Microscope with Energy Disperse Spectroscopy (FSEM-EDS), X-ray Photoelectron Spectroscopy (XPS), and contact angle measurements, are employed to analyze the samples. The experimental results reveal that the flotation performance is enhanced through the use of pyrolysis-grinding and pyrolysis-ultrasonic techniques combined with MNBs, resulting in improved recovery and metal content. The most optimal flotation performance is achieved with the pyrolysis-ultrasonic-MNBs method at a pyrolysis temperature and duration of 350 °C and 15 min, respectively, leading to an increase in the metal content of cathode materials from 65 ± 3 % to 95 ± 2 %. •Effect of pyrolysis and MNBs on the performance of spent LIBs flotation was studied.•Surface properties of pyrolytic materials were analyzed.•Elimination of organic binders was achieved through pyrolysis at 350 °C for 15 min.•Improved flotation performance was observed with using of PGM and PUM.•Two-stage flotation processes with MNBs upgraded the grade of CMs up to 95 ± 2 %.