Revisiting the performance of electrical double-layer capacitors implementing a sodium perchlorate water-in-salt electrolyte
[ 1 ] Instytut Chemii i Elektrochemii Technicznej, Wydział Technologii Chemicznej, Politechnika Poznańska | [ P ] employee
2023
scientific article / paper
english
- Water-in-salt (WIS) NaClO4 electrolyte
- Porous carbon electrodes
- Electrochemical stability window (ESW)
- Electrical double-layer capacitors (EDLCs)
- Operative cell potential
EN A maximum cell potential of 2.3 V has been claimed in the literature for an electrical double-layer capacitor (EDLC) in 17 mol kg− 1 NaClO4 water-in-salt (WIS) electrolyte. Puzzled by this high cell potential compared to e. g., 1.8 V for an EDLC in 20 mol kg− 1 LiTFSI, and by the fact that the high electrochemical stability window (ESW) values reported in 17 mol kg− 1 NaClO4 were obtained only on non-porous electrodes, this contribution intends to carefully revisit the electrochemical properties of EDLCs based on this WIS electrolyte. Herein, an appropriate electrochemical approach was used to identify precisely the ESW of an activated carbon (AC) electrode (made from the YP50F carbon) and cell potential of electrical double-layer capacitors (EDLCs) when using an aqueous NaClO4 solution. It was found that the ESW is pushed from 1.7 V to 1.8 V and 2.0 V when increasing the NaClO4 concentration from 2 mol kg− 1 to 10 mol kg− 1 and 17 mol kg− 1 , respectively. In 17 mol kg− 1 NaClO4, the comparison of the stability limits of the AC electrode with the potential limits of electrodes (determined by galvanostatic cycling) in a symmetric AC/AC cell equipped with a silver quasi-reference electrode (AgQRE) led us to the conclusion that the maximum voltage of the EDLC is only 1.9 V. Furthermore, the determination of the coulombic and energy efficiency of AC/AC coin cells in 17 mol kg− 1 WIS NaClO4 electrolyte, as well as the electrochemical impedance spectroscopy measurements vs cell potential indicated an operative value of 1.8 V; this value was accurately confirmed by long term potentiostatic floating. Hence, these careful investigations demonstrate that inappropriate experimental conditions to determine the performance of EDLCs, as reported in the literature, may lead to completely biased results.
11.03.2023
142212-1 - 142212-9
Article number: 142212
other
100
5,5