Ion transport and electrochemical properties of proton conducting SPE for EDLC with constant specific capacitance and energy density

Abstract

Chitosan (CH): poly(2-oxazoline) (POZ): ammonium thiocyanate (NH4SCN): glycerol electrolytes with developed conductivity are organized using solution casting technique. The loading of 50 wt. % glycerol maximized the conductivity to 1.58 × 10−3 S/cm. The simulations of electrochemical impedance spectroscopy (EIS) data with the electrical equivalent circuit (EEC) method are used to determine fundamental ion transport parameters. The diffusion coefficient (D) of 4.67 × 10-7 cm2 s−1, mobility (μ) of 1.82 × 10-5 cm2 V−1 s, and carrier density (n) of 5.42 × 1020 cm−3 are measured successfully for the highest ion conducting system. Dielectric properties such as dielectric constant, dielectric loss and electric modulus are studied as a function of frequency. Conductivity and dielectric analysis are found to follow the same trend. There are observable peaks in both ε“ and tanδ spectra. Various electrochemical tests are measured for the highest ion conducting sample. Transference numbers of ion (tion) and electron (te) for the CSPZNHSN5 are measured to be 0.8 and 0.2, respectively, which show that ions are the majority charge carriers. The electrochemical stability of the CSPZNHSN5 which is measured by linear sweep voltammetry (LSV) was found to be 2.2 V. The electric double layer capacitor (EDLC) internal resistance is between 68 Ω and 82 Ω. Using the GCD measurement, the capacitance, energy, and power density of the EDLC are 100F/g, 14.5 Wh/kg, and 1500 W/kg.