Hydrogel neutral electrolyte of PVA/HEC for flexible supercapacitor

In this study, hydrogel neutral electrolyte was synthesized from PVA/HEC (polyvinyl alcohol/ hydroxyl ethyl cellulose) using CA (citric acid) as the chemical crosslinking. The neutral electrolyte of Na2SO4 (sodium sulphate) was used to obtain higher cell voltages of supercapacitor. To investigate the performance of the flexible supercapacitor, we varied the concentration of CA (0-30%). The supercapacitor consisted of the hydrogel and two activated carbons which were assembled in between. The resulted supercapacitors were then characterized using FTIR (Fourier Transform Infrared) to evaluate the chemical bond formation in the hydrogel electrolyte. Electrochemical characteristic of the supercapacitors was also analyzed by EIS and cyclic voltammetry measurements. The results showed that the addition of 15% and 30 % CA yielded the crosslinking reaction of PVA/HEC as represented by reduction of O-H groups and the existence of C=O groups. The hydrogel of 15% CA produced the lowest ESR (Equivalent Series Resistance) of 45 Ω and the highest specific capacitance of 43.05 F/g. Therefore, it can be concluded that hydrogel neutral electrolyte of PVA/HEC can be utilized as a high voltage flexible supercapacitor.