Binding mechanisms of PVDF in lithium ion batteries

The binding mechanism of polyvinylidene fluoride (PVDF) in lithium ion batteries (LIBs) is important for the development of new binders and the peeling of active materials during the recovery of spent LIBs. This paper focuses on revealing the binding mechanism of PVDF by the simulation calculation using density function theory (DFT) and the analyses of the binding surfaces in LIBs. The results of the process simulation and theoretical calculation indicate that the binding interactions between LiFePO4 (LFP) and PVDF are much stronger than that between PVDF and Al in LFP batteries, whereas, the binding interactions between Li(Ni1-x-yCoxMny)O2 (NCM) and PVDF are weaker than that between PVDF and Al in NCM batteries. Scanning electron microscopy and Auger electron spectroscopy (AES) analyses indicate that PVDF are mainly distributed on the surfaces of LFP in LFP batteries, however, PVDF distribute uniformly between Al and NCM in NCM batteries. In addition, AES analyses indicate that no chemical interaction among the surfaces of active materials, PVDF, and Al, both in LFP and NCM batteries. This study provides a foundation for the development of new binders and the peeling of active materials in LIBs.