Characterization of commercial supercapacitors for low temperature applications

Electrochemical characterizations at low temperature and floating tests have been performed on 600F commercial supercapacitor (SC) for acetonitrile (AN)-based and AN + methyl acetate (MA) mixed electrolytes. From -40 to +20 degrees C, AN electrolyte showed slightly higher capacitance than those of AN + MA mixed electrolytes (25 and 33 vol.% of MA). At -55 degrees C, however, AN electrolyte did not cycle at all, while MA mixed electrolyte normally cycled with a slight decrease in their capacitance. From electrochemical impedance spectroscopy measurements, the whole resistance for AN-based cells at -55 degrees C was found to be about 10,000 times higher than that of +20 degrees C. while a 40-fold increase in the cell resistance was obtained for the MA mixture between 20 and -55 degrees C. From the results of floating tests at 2.7 V and 60 degrees C for 1 month, the 25 vol.% MA mixture showed no change and slight decreased but stable capacitance. (C) 2012 Elsevier B.V. All rights reserved.