Comparative operando study of degradation mechanisms in carbon-based electrochemical capacitors with Li2SO4 and LiNO3 electrolytes

This paper reports on the operando study of degradation mechanisms in carbon-based electrochemical capacitors with Li2SO4 and LiNO3 electrolytes. Several electrochemical techniques, coupled with mass and Raman spectrometry have been implemented to recognize and describe the processes occurring at the carbon electrode/aqueous electrolyte interface. It has been shown that for the systems operating with mild, water-based electrolytes, the performance fade might have a different origin; dependently on the salt used for electrolyte preparation, carbon surface might be either oxidized or anion might be reduced. A detrimental effect of oxygen evolution at elevated voltages (up to 1.8 V) has also been observed. An in-depth study involving the implementation of the operando techniques also allowed the most optimal voltage for both systems to be determined, taking into account their long-term performance as well. (C) 2017 Elsevier Ltd. All rights reserved.