Vinylene Carbonate as Co-Solvent for Low-Temperature Mixed Electrolyte Based Supercapacitors

Abstract

The electrochemical characteristics of supercapacitors consisting of molybdenum carbide derived carbon C(Mo2C) electrodes in 1M NaPF6 solutions in various mixtures (0.5–5%) of vinylene carbonate (VC) with propylene carbonate (PC) and ethyl acetate (EA) (1:1 by volume) have been studied using cyclic voltammetry, constant current charging/discharging and electrochemical impedance spectroscopy methods. The specific capacitance and series resistance values dependencies on the used solvent mixture and applied temperature (from −40°C to 60°C) have been established. The region of ideal polarizability has been established for C(Mo2C) electrodes in all electrolytes and temperatures investigated, except at T ≥ 40°C. Specific conductivity values have been measured and correlated with electrochemistry data. Limiting capacitance, calculated characteristic time constant and complex power values depend noticeably on the solvent mixture used in the electrolyte, i.e. on the viscosity and specific conductivity of the electrolyte solution. The studied electrolytes are potential candidates for low-temperature supercapacitors.