In situ electrochemical dilatometry of carbide-derived carbons

The long life durability and extraordinary stability of supercapacitors are ascribed to the common concept that the charge storage is purely based on double-layer charging. Therefore the ideal supercapacitor electrode should be free of charge induced microscopic structural changes. However, recent in-situ investigations on different carbon materials for supercapacitor electrodes have shown that the charge and discharge is accompanied by dimensional changes of the electrode up to several percent. This work studies the influence of the pore size on the expansion behavior of carbon electrodes derived from titanium carbide-derived carbons with an average pore size between 5 and 8 Å. Using tetraethylammonium tetrafluoroborate in acetonitrile, the swelling of the electrodes was measured by in situ dilatometry. The experiments revealed an increased expansion on the negatively charged electrode for pores below 6 Å, which could be described with pore swelling.

► Carbide-derived carbon (CDC) supercapacitor electrodes undergo a dimensional change during charging and discharging.
► Using 1 M TEA-BF4 in acetonitrile, the maximum swelling in a 3 V window is ~ 2%.
► CDC swelling is dependent on the pore size and fully reversible.
► Large swelling corresponds with strong ion sieving.