Polyvinylidene fluoride binder removal through subcritical methanol for efficient liberation of cathode materials from lithium-ion batteries

Abstract

Polyvinylidene fluoride (PVDF) binder removal is critical for the recovery of valuable metal materials during the treatment of spent lithium-ion batteries (LIBs). This study proposed a new PVDF removal method through subcritical methanol extraction. The optimal conditions and mechanism of the method for the liberation of cathode materials were explored, and the recovered cathode materials, aluminum foils (Al foils), and extracted binder were characterized. Experimental results on actual cathode sheets show that under the extraction temperature of 200 °C, after holding and stirring time for 10 min, the cathode materials were recovered in the form of powder with an exfoliation efficiency of 98.51 % from Al foil without any damage. The removal efficiency of PVDF reached 78.74 wt% while the crystal structure of LiMn₂O₄ remained intact. Compared with the new binder, the recovered PVDF (R-PVDF) has a similar glass transition temperature and melting point but presents a more intricate surface morphology, lower crystallinity, and higher proportion α-phase crystallin. The results indicate that R-PVDF has the potential to be reused as a new binder in LIBs. This study aims to provide a new efficient and environmentally friendly solution for the recycling of spent LIBs.