Polyvinylpyrrolidone as binder for castable supercapacitor electrodes with high electrochemical performance in organic electrolytes

Polyvinylpyrrolidone (PVP) is presented as a "greener" alternative to commonly used supercapacitor binders, namely polyvinylidenedifluoride (PVDF) or polytetrafluoroethylene (PTFE). The key advantages of using PVP are that it is non-toxic and soluble in ethanol and it can be used to spray coat or drain cast activated carbon (AC) electrodes directly on a current collector such as aluminum foil – in contrast to PTFE that requires rolling or PVDF that requires toxic N-methylpyrrolidone (NMP). The electrodes with the best mechanical stability incorporated 3.5 mass% of 1.300.000 g mol−1PVP. Compared to PTFE or PVDF, the resulting pore volume was significantly higher and the specific surface area significantly larger when using PVP (normalized to the amount of AC). A good electrochemical performance was observed in organic electrolytes for AC–PVP electrodes: 112 or 97 F g−1at 0.1 A g−1in 1 M TEA–BF4in propylene carbonate or acetonitrile, respectively. The performance stability was comparable to PTFE-bound electrodes when adjusting the maximum cell voltage to 2.5 V while preserving the manufacturing features of PVDF–AC films. (Electro)chemical stability is shown by electrochemical testing and infrared vibrational spectroscopy for propylene carbonate and acetonitrile.