Improving the Stability of Supercapacitors at High Voltages and High Temperatures by the Implementation of Ethyl Isopropyl Sulfone as Electrolyte Solvent

Abstract Two of the main weaknesses of modern electric double‐layer capacitors are the rather limited ranges of operating voltage and temperature in which these devices do not suffer from the occurrence of irreversible decomposition processes. These parameters are strongly interconnected and lowering the operating voltage when increasing the temperature is unavoidable, so as to protect the electric double‐layer capacitor from damage. With the aim to maintain the operating voltage as high as possible at elevated temperatures, in this study, the application of ethyl isopropyl sulfone as an electrolyte solvent for electric double‐layer capacitors is presented. It is shown that ethyl isopropyl sulfone‐based electrolytes display excellent thermal and electrochemical stability enabling high capacitance retention after floating tests for 500 h at 60 and 80 °C, e.g. 68% at 3.4 V at 60 °C. A possible reason for the above‐average stability is that decomposition products of ethyl isopropyl sulfone can deposit on the electrode surface which may act as a passivation layer and prevent further degradation.