Pyrolysis-Ultrasonic-Assisted Flotation Technology for Recovering Graphite and LiCoO2 from Spent Lithium-Ion Batteries

An environmentally-friendly technology of pyrolysis-ultrasonic-assisted flotation for recovering graphite and LiCoO2 from spent lithium-ion batteries has been evaluated in this paper. Surface properties and morphology of graphite and LiCoO2 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 LiCoO2. 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 LiCoO2 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 LiCoO2 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 LiCoO2 particles for the subsequent chemical metallurgy.