Pyrolysis-Ultrasonic-Assisted Flotation Technology for Recovering Graphite and LiCoO 2 from Spent Lithium-Ion Batteries

An environmentally-friendly technology of pyrolysis-ultrasonic-assisted flotation for recovering graphite and LiCoO 2 from spent lithium-ion batteries has been evaluated in this paper. Surface properties and morphology of graphite and LiCoO 2 derived from spent lithium-ion batteries were carefully studied, and on this basis, their pyrolysis characteristics were investigated by thermogravimetry–gas chromatography–mass spectroscopy. Advanced analysis techniques, scanning electron microscopy, X-ray fluorescence spectrometry, and X-ray photoelectron spectroscopy, were utilized to analyze the effect of pyrolysis and ultrasound on the surface properties and morphology of graphite and LiCoO 2 . Flotation tests were conducted to evaluate the reinforcing effect of pyrolysis–ultrasound on flotation behavior. Results show that organic binder and electrolyte are the main reasons that graphite and LiCoO 2 are hard to separate by flotation; meanwhile, pyrolysis can effectively decompose organic binders at a pyrolysis temperature of 500 °C, and ultrasonic cleaning can effectively remove residual pyrolysis products. Pyrolysis-ultrasonic-assisted flotation can make the LiCoO 2 grade improve from 67.25% to 93.89% with the recovery improving from 74.62% to 96.88%. This research work may provide an alternative process for the preparation of high purity LiCoO 2 particles for the subsequent chemical metallurgy.