Electrochemical double layer capacitors (EDLCs) are energy storage devices that can complement Li-ion batteries (LiBs) for high power uptake applications[1]. However, EDLCs suffer from limited energy density (about 10Wh/kg compared to 250 Wh/kg for LiBs). A way to increase the energy density still maintaining high power capability and long cycle life is the next challenge of this technology. An approach to achieve this objective is to increase the voltage window. Nevertheless, using a high voltage window lead to a faster ageing. So, a better understanding of degradation process during the ageing is needed to improve EDLCs storage and their cycle life.

In this work, degradation mechanisms at porous carbon electrodes have been investigated in non-aqueous electrolytes, following an ageing protocol previously reported [2]. Electrochemical performances before and after ageing have been compared. Then, post-mortem analyses were performed using various analytical methods. Raman spectroscopy allowed us for better understanding of degradation processes occurring at the carbon/electrolyte interface. Leading to a partial amorphization of the positive porous carbon electrode. The carbon disorder was further correlated with possible degradation mechanisms during ageing to explain the performance decrease.

References:

[1] P. Simon and Y. Gogotsi, ‘Perspectives for electrochemical capacitors and related devices’, Nature Materials, p. 13, doi: https://doi.org/10.1038/s41563-020-0747-z.

[2] Y. Liu, B. Soucaze-Guillous, P.-L. Taberna, and P. Simon, ‘Understanding of carbon-based supercapacitors ageing mechanisms by electrochemical and analytical methods’, Journal of Power Sources, vol. 366., pp. 123-130., 2017, doi: https://doi.org/10.1016/j.jpowsour.2017.08.104.