High-frequency electrochemical capacitors based on plasma pyrolyzed bacterial cellulose aerogel for current ripple filtering and pulse energy storage

There are great needs in developing compact-size kilohertz (kHz) high-frequency (HF) electrochemical capacitors (ECs) for ripple current filtering and environmental vibration energy harvesting. However, the previously demonstrated electrodes are generally limited to a very small areal capacitance density at 120 Hz due to sub-μm thick electrode used for meeting frequency requirement, which renders them unsuitable for practical ECs. Here, using crosslinked carbon nanofiber aerogel, derived from rapid microwave plasma pyrolysis of bacterial cellulose that was synthesized in a fermentation process, we demonstrated kHz HF-ECs with areal capacitance density as high as 4.5 mF cm⁻² at 120 Hz in an aqueous electrolyte. The cruciality of plasma pyrolysis on high frequency response of the derived carbon nanofiber aerogel was discussed. The electrode performance in an organic electrolyte was further studied for operation in a large potential window of more than 3 V. Using such kHz HF-ECs, we further demonstrated their applications in rapid pulse energy storage for vibrational energy harvesting, as well as in ripple current filtering for AC/DC conversion. The promising results suggest this technology has great potential for developing practical compact HF-ECs in substitution of electrolytic capacitors for several crucial applications.