Measuring cycle efficiency and capacitance of chemically activated carbons in propylene carbonate

Abstract

The cycle efficiency and capacitance of two KOH-activated carbons have been tested in 0.5M tetraethylammonium tetrafluoroborate in propylene carbonate (TEABF4/PC) under different conditions of temperature (room temperature and 70°C) and voltage (0–3V). The materials tested include a KOH-activated carbon before and after treatment with different acids and hydrogen at high temperature to remove most of the oxygen groups and inorganic impurities. Porous texture and surface chemistry characterization have been carried out before and after cycling to understand the changes in the properties of activated carbons during the cycles. It has been observed that the treatment with different acids and hydrogen at high temperature produces materials with higher cycling stability. The results point out that the observed electrode degradation is mainly due to some pore blockage caused by reaction of the solvent with the functional groups on the carbon. The blockage of porosity is higher for the sample with higher oxygen content, indicating that the treatment carried out to remove the oxygen groups has an important positive effect, giving electrodes with a much lower degradation under very aggressive conditions in a TEABF4/PC medium.