Exploring the sustainable frontier by investigating structural, electrochemical and ion transport properties of potassium salt-doped PVA-based polymer electrolyte for supercapacitor application

Abstract

In the current study, a biodegradable green polymer was used for energy storage application. Solid polymer electrolytes (SPEs) are fabricated by incorporating constant loading weight percent (40 wt%) potassium thiocyanate (KSCN) and various glycerol into PVA by the solution cast method. The X-ray diffraction (XRD) test shows that the most conductive electrolyte (σdc = 4.34 × 10−3 S cm−1) determined by electrochemical impedance spectroscopy (EIS) possesses the lowest degree of crystallinity (Xc = 11.4). The EIS test reveals that the PVKSG4 sample has the minimum resistance. The interaction between various constituents of the electrolyte was observed by the fourier transform infrared (FTIR) spectroscopy. The transport parameters (D, n, and μ) associated with moving cations as determined by both EIS and FTIR approaches are comparable and well matched with DC conductivity results. Ionic conductivity and dielectric parameters have the same trend with glycerol concentration. Transference numbers of ions (ti) and electrons (te) for the PVKSG4 are calculated to be 0.918 and 0.082, respectively, meaning that ions are the dominant species contributing to conduction. Linear sweep voltammetry (LSV) study displays that the PVKSG4 film possesses a breakdown voltage of 2.3 V which is enough for device construction. The equivalent series resistance (ESR) of the electric double layer capacitor (EDLC) device has been slightly increased from 59 to 68 Ω over the initial and finial cycle. The capacitive nature of EDLC was confirmed by the cyclic voltammetry (CV), and from the galvanostatic charge/discharge (GCD) test the values of specific capacitance, specific energy density, and specific power density were found to be 72 F g−1, 11 Wh Kg−1, and 1800 W Kg−1. The parameters of EDLC device is an indicative for the fact that the future of green energy is linked to supercapacitors as an alternative for toxic Li-ion batteries.