Influence of the solvent properties on the characteristics of a double layer capacitor

Electrochemical and electrical double layer characteristics for the phase boundary nanoporous carbon \1.0 M triethylmethylammonium tetrafluoroborate (TEMA) solution in acetonitrile (AN), gamma-butyrolactone (GBL), acetone (DMK) and propylene carbonate (PC) have been studied using the cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS) methods. The constant current and constant power charge/discharge characteristics of capacitor modules constructed and filled with different electrolytes were tested over the temperature range from -30 to +60 degreesC. Tests for "lifetime" of the capacitors were performed at elevated temperature. Energy density versus power density, i.e. so-called Ragone plots were constructed to characterize the performance of the capacitor modules. It was established that the energy density, power density, discharge time, etc. of the electrical double layer capacitors (EDLC) depend on the pore size distribution and conductivity of the nanoporous electrode material. It was shown that the energy output of capacitor depends on the viscosity and molar conductivity of a solvent. The power output of the capacitor increased in the order of solvent PC < DMK < GBL < AN in agreement with the dependence of the Ragone plot parameters on temperature. (C) 2004 Elsevier B.V. All rights reserved.