Mixtures of acetonitrile and ethyl isopropyl sulfone as electrolytes for electrochemical double layer capacitors

In this work we report about the properties of electrolytes containing the solvent ethyl isopropyl sulfone (EiPS) as well as of mixtures of EiPS and acetonitrile (ACN), and about their use as electrolytes for electrochemical double layer capacitors (EDLCs). These electrolytes display transport and thermal properties suitable for use in EDLCs and their use allows the realization of high voltage devices. The maximum operative voltage achievable with an electrolyte purely based on EiPS is 3.4 V, whereas mixtures of EiPS and ACN (in wt%-ratios of 75:25 and 50:50) were found to allow an operative voltage of 3.0 V. EDLCs containing the mixture EiPS:ACN (75:25) only lose 3% of their initial capacitance after 500 h of float test at 3 V, which is a truly remarkable value. Compared to the pure EiPS electrolyte, this mixture also leads to systems with lower ESR values, which makes it a promising candidate for high energy EDLCs. (c) 2019 Elsevier Ltd. All rights reserved.