Determination of Electrochemical Windows of Novel Electrolytes for Double Layer Capacitors by Stepwise Cyclic Voltammetry Experiments

Dominik Moosbauer,¹ Steffen Jordan,² Franz Wudy,¹ Sheng S. Zhang,³ Michael Schmidt⁴ and Heiner J. Gores^1,*

¹ University of Regensburg, Institute of Physical and Theoretical Chemistry, Universitaetsstrasse 31, D-93053 Regensburg, Germany
² Steffen Jordan, Infineon AG, Regensburg, Germany
³ U.S. Army Research Laboratory, Sensors and Electron Devices Directorate, Adelphi, MD 20783-1197, USA
⁴ Michael Schmidt, Merck KGaA, D-64271 Darmstadt, Germany
* Corresponding author: E-mail: Heiner.gores@chemie.uni-regensburg.de

Abstract
In this work we synthesized two novel salts for electrochemical double layer capacitors, i.e. N,N-dimethylpyrrolidinium tetrakis(trifluoroacetato)borate (DMPBTFAc) and N-ethyl-N-methyl-pyrrolidinium bis[1,2-oxalato(2-O,O’)]borate (EMPBOX), and determined the electrochemical window of their solutions in acetonitrile (AN) by using stepwise cyclic voltammetry. The electrochemical window plays an important role in electrochemical double layer capacitors (EDLCs) as the energy density of such devices depends on the square of the operating voltage. Because anodic and cathodic decomposition voltages may be shifted with respect to the open circuit voltage (OCV), the OCV is another important characteristic of such an electrolyte. Both DMPBTFAc and EMPBOX solutions show wide electrochemical windows of about 4 V with nearly equal voltage gaps for the anodic and cathodic decomposition at activated carbon electrodes.

Keywords: Double layer capacitor, EDLC, DLC, electrochemical window, cyclic voltammetry, Faradaic Fraction