A Surprising Failure Mechanism in Symmetric Supercapacitors at High Voltages

Arie Borenstein, Ran Attias, Ortal Hanna, Shalom Luski, Richard B. Kaner, Doron Aurbach

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


Ionic liquids (ILs) are attractive candidates for high-voltage electrochemical energy storage systems, owing to their high electrochemical stability. Recently, a unique eutectic mixture of ILs was reported to demonstrate outstanding performance in supercapacitor systems at low temperatures. Yet, many publications using this or similar IL mixtures reported only a limited voltage or cyclability when utilizing them with practical activated carbon electrodes. With supercapacitors consisting of symmetric electrodes, in which voltages higher than 3 V are applied, fast capacity fading and activity termination are observed. In order to exceed the limit of 3 V for supercapacitors that use electrolyte solutions possessing wide electrochemical windows, we thoroughly investigated the (unexpected) failure mechanism, using several analytical methods. This is the most important aspect of the paper. By this, we discovered a pronounced difference in the electrochemical behavior of the negative and the positive electrodes, which has significant implications on the operation of full symmetric cells at high voltages. Finally, we propose a solution that enables stable operation of cells up to 3.4 V. By balancing the mass of the electrodes, we prevent high-voltage failure and control the voltage split to use the full electrochemical window of each electrode and obtain a higher cell voltage of 3.4 V and an energy density higher than 40 Wh/kg (of the electrode materials). The most important aspect of this work was a rigorous study of the failure mechanism.

Original languageEnglish
Pages (from-to)2660-2668
Number of pages9
Issue number10
StatePublished - Oct 2017

Bibliographical note

Publisher Copyright:
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim


  • high voltage supercapacitors
  • ion intercalation
  • ionic liquid electrolytes
  • mass balance
  • voltage split


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