Removal of Organics by Pyrolysis for Enhancing Liberation and Flotation Behavior of Electrode Materials Derived from Spent Lithium-Ion Batteries

Abstract

Organics retained in electrode materials decrease the liberation and flotation efficiency of electrode materials. The pyrolysis-assisted sustainable process was used to remove the organic binder and residual electrolyte that were wrapped on the surface of electrode particles for enhancing liberation efficiency and flotation behavior of electrode materials. The pyrolysis characteristics of organics in electrode materials were investigated. A high-resolution three-dimensional X-ray microanalyzer combined with a scanning electron microscope was utilized to reveal the liberation enhancement mechanism of electrode materials. Afterward, effects of pyrolysis on surface morphology and flotation behavior of electrode materials were evaluated. Pyrolysis characteristics demonstrate that organics can be adequately decomposed at a pyrolysis temperature of 500 °C resulting in a high liberation efficiency with a shorter crushing time. However, some pyrolysis oils remain on the surface of electrode materials at a pyrolysis temperature of 500 °C, which decrease flotation efficiency of electrode materials. Contact angle analysis indicates that the optimum flotation results are presented at a pyrolysis temperature of 550 °C due to the removal of residual pyrolysis oils and the cathode grade is up to 94.72% with a recovery of 83.75% in this condition. Wet-ball grinding can further improve cathode recovery from 83.75 to 91.35% by removing residual pyrolytic carbon.