De-agglomeration of cathode composites for direct recycling of Li-ion batteries

摘要

Direct recycling of Li-ion batteries (LIBs) reclaims electrode materials using physical separation followed by materials' rejuvenation processes. The cathode composites in LIBs contain both carbon black and PVDF binders in its chemistry. For the rejuvenation process to work, an ability to remove these impurities is desirable. In the present work, de-agglomeration of individual components from the cathode composites has been carried out using a mechanical process that is developed for preserving functional integrity of the cathode active materials. It has been shown that the size of the cathode composites is effectively reduced upon a de-agglomeration process due to a liberation of PVDF binders from the cathode composites. The de-agglomeration performance has been evaluated by separating mixed materials by the degree in surface hydrophobicity using the froth flotation method. The performance improves with end-of-life (EOL) LIBs compared to new LIBs, benefiting from a degradation of PVDF binders after charging-discharging cycles. X-ray photoelectron spectra suggests that the de-agglomeration is done by breaking intermolecular bond between PVDF and cathode active materials as well as covalent bond within PVDF binders. The present work demonstrates a non-chemical method for liberating individual components from cathode composites for the direct recycling of LIBs.