Unveiling the Influence of Dehydrofluorination of Poly(vinylidene fluoride) Binder on the Failure of Graphite Anode in Potassium‐ion Batteries

The poly(vinylidene fluoride) (PVDF) binder has been successfully employed in lithium-ion batteries (LIBs), but it unexpectedly exhibits detrimental effects on the anode performance in potassium-ion batteries (PIBs). The PVDF-based graphite electrode shows a low Coulombic efficiency and even fails to maintain the electrode integrity after several cycles in the 0.8 M KPF₆ ethylene carbonate/diethyl carbonate electrolyte. In this study, we unveil that the dehydrofluorination reaction of PVDF initiated by potassium ethoxide may be the key factor causing the above issues. The dehydrofluorination not only disables the binder but also releases detrimental ethanol into the electrolyte. The released ethanol can dissolve the organic components of solid electrolyte interphase (SEI) and deplete the potassium resource, thereby resulting in a reduction of Coulombic efficiency and a more severe accumulation of SEI. The crowding of more accumulated SEI coupled with the large volume expansion of intercalated graphite results in the failure of PVDF-based graphite electrodes. This fundamental finding may provide a deeper insight into the failure mechanism of PVDF as a binder in PIBs, and meanwhile, give valuable guidance for the use of PVDF in battery communities containing sodium-ion batteries and LIBs.