Ionic liquid-gelled polyvinylidene fluoride/polyvinyl acetate polymer electrolyte for solid supercapacitor

•A novel PVDF/PVAc/IL GPE for solid-state electrochemical devices was successfully prepared.•By tuning the IL contents, the GPE could form a uniform, translucent, and very flexible film.•The GPE presented both good thermal stability and satisfactory electrochemical properties.•A 3.0 V cell using this GPE showed both high specific capacitance and good cycling stability.

A promising ionic liquid-gelled polymer electrolyte (GPE) based on semi-crystal polyvinylidene fluoride (PVDF), amorphous polyvinyl acetate (PVAc) and ionic conductive 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) is successfully prepared via solution-casting method. The structures and morphologies of the GPEs are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the thermal stability of the GPEs is measured by thermogravimetric/differential scanning calorimetry (TG/DSC). Highly homogenous, translucent, and flexible GPE films are easily obtained by adjusting the ionic liquid (IL) contents. The PVDF/PVAc/IL (IL, 50 wt%) GPE film presents good thermal stability (∼300 °C), wide electrochemical window (>4.0 V), and acceptable ionic conductivity (2.42 × 10−3 S cm−1 at room temperature) as well. A 3.0 V C/C solid-state capacitor cell using this GPE film was assembled and measured. It is found that the capacitor cell shows specific capacitance of 93.3 F g−1 (based on activated carbon) at the current density of 200 mA g−1, and can retain more than 90% of the initial capacitance after 5000 charge–discharge cycles.

Graphical abstractA 3.0 V solid-state C/C capacitor cell using the fabricated flexible PVDF/PVAc/IL GPE film presents good electrochemical performance.Figure optionsDownload full-size imageDownload as PowerPoint slide