An amide based polyvinyl alcohol / protic ionic liquid (PVA / PIL) gel electrolyte for supercapacitor applications

An aqueous gel based on polyvinyl alcohol (PVA) and a mixture of two nitrate salts, namely lithium nitrate (LiNO3) and pyrrolidinium nitrate, PIL (PyrrNO3) was prepared and used as an electrolyte. The gel electrolyte shows a high conductivity in the presence of formamide (FMD), which was studied as an organic additive in the gel at 5 to 400 % with respect to the salt content. Their electrochemical behaviors were examined by cyclic voltammetry, galvanostatic charge-discharge and an impedance technique at room temperature (17°C). The 100 % of amide in the gel has shown a maximum ionic conductivity of 33 x 10-3 and 11.2 x 10-3 Scm-1 at 17°C and-20°C respectively. A two electrode supercapacitor (SC) was assembled and analyzed. The cycle life is improved by the additive over the bare gel, as evidenced by the galvanostatic cycling. The specific discharge capacitance of SC based on the 100% of amide can be used for delivering 34.2, 27.3 and 21 Fg-1 at 1.5 V under a constant current density of 50, 100 and 500 mAg-1 respectively. Moreover, the SC efficiency was maintained at 95%, and above as well as the capacity loss was minimized in the presence of the additive. This quasi solid-state supercapacitor will be capable of delivering an energy density of 12-13 Whkg-1 and maximum power density of 0.60 kWkg-1 at 2 V. The results confirm that the capacitive enhancement is at the lower limit of the FMD.