Innovative methodology for green recycling of spent lithium-ion batteries: Effective pyrolysis with DMF

Abstract

The separation and recycling of cathode active materials (CAMs) and Al foils are the key steps for the green utilization of spent lithium-ion batteries (LIBs). Herein, an effective pyrolysis with dimethyl formamide (DMF) was proposed to effectively separate CAMs from Al foils, which is difficult to be achieved by a facile process. The results indicate that the addition of DMF can enhance the separation of CAMs and Al foils by generating micro bubbles (Consisting of CH4, CO2, H2O, HF and CO) between them and about 98.93% of CAMs is recovered after the pyrolysis at 450 °C via facile screening process. During the pyrolysis process, DMF can also accelerate the decomposition of toxic electrolyte to non-toxic small molecule compounds, thus achieving the safe disposal of organic pollutants contained in spent LIBs. The SEM-EDS and XPS analyses reveal that the CAMs recovered by the process hardly contain Al impurity, which is beneficial to the regeneration of spent LiFePO4. The TGA-MS and TGA-FTIR analyses imply that PVDF and DMF are the two main substances that underwent chemical reactions during the pyrolysis process, in which lots of micro bubbles are produced between CAMs and Al foils. In situ FTIR spectroscopy and quantum-chemical simulations indicate that the intermediate pyrolysis products of DMF can promote the thermal decomposition of PVDF, which also favors the efficient separation of CAMs and Al foils. This study provides an efficient and environmentally friendly way to separate and recover CAMs and Al from spent LIBs.