Fluoroethylene Carbonate as Co-Solvent for Propylene Carbonate Based Electrical Double Layer Capacitors

Abstract

The electrochemical characteristics of the electrical double layer capacitors consisting of the microporous titanium carbide derived carbon (TiC-CDC) electrode in 1M (C2H5)3CH3NBF4 solutions in 4-methyl-1,3-dioxolan-2-one, (so-called propylene carbonate (PC)), 4-fluoro-1,3-dioxalan-2-one, (so-called fluoroethylene carbonate (FEC)), and in various mixtures of named solvents like FEC:PC (1:1 volume ratio), FEC:PC (1:9) and FEC:PC (1:19) have been studied using cyclic voltammetry and electrochemical impedance spectroscopy methods. The specific capacitance, phase angle and series resistance values dependent on the solvent system used and temperature applied (from −45°C to 90°C) have been established. The region of ideal polarizability ΔE ≥ 3.0 V has been demonstrated for TiC-CDC electrodes in all electrolytes and at temperatures investigated, except at T ≥ 90°C. Specific conductivity and viscosity values have been obtained and correlated with electrochemistry data. The limiting capacitance, the characteristic time constant and complex power values depend noticeably on the solvent used for preparation of electrolyte, i.e. on the viscosity and specific conductivity of electrolyte solution used.