Pyrolysis and physical separation for the recovery of spent LiFePO4 batteries

Abstract

In this study, a novel process consisting of pyrolysis and physical separation was proposed to comprehensively recycle spent lithium ion batteries (LIBs). The discharge and pyrolysis behaviors of spent LIBs, the recovery of electrolyte from the spent LIBs by low-temperature volatilization, and the recovery of valuable materials from the pyrolytic residues through physical separation were studied in detail. The results indicated that approximately 99.91% of the organic electrolytes was recycled, and the lithium salt (LiPF₆) in the batteries was disposed by pyrolysis process. The active materials could be effectively separated from current collectors after the pyrolysis under N₂ at 550 °C for 2 h. The pyrolytic gas was mainly composed of light alkenes, and the pyrolytic tar was mainly composed of aromatic long chain alkenes and light alcohols. Pyrolytic residues were recycled by color sorting, high-pressure water cleaning and flotation processes, and about 99.34% of Al, 96.25% of Cu, and 49.67% of cathode active materials were recovered from the spent LIBs. Finally, electrochemical tests indicate that the cathode active materials obtained by the process can be used to produce new batteries.

Keywords: Cathode active materials; Color sorting separation; Flotation; Pyrolysis; Spent LiFePO(4) batteries.