Abstract
High-frequency responsive electrochemical capacitor (EC), which can convert alternating current (AC) in the circuit to direct current (DC), is an ideal filtering capacitor with lightweight superiority to replace the bulky aluminum electrolytic capacitor (AEC). However, current electrodes are difficult to achieve high energy density and high-frequency response properties simultaneously, primarily due to the electrode structure dilemmas of maximizing the electrode area or accelerating the ion transport. Herein, strictly vertical graphene arrays (SVGAs) directly prepared by electric-field-assisted plasma enhanced chemical vapor deposition have been successfully designed as the main electrode material of ECs to ensure the ions rapidly adsorb/desorb within the richly available surface spaces. The SVGAs exhibit an excellent specific areal capacitance of 1.72 mF‧cm− 2 at Φ120 = 80.6° even after 500,000 cycles in the aqueous ECs, which is far better than that of most quasi-vertical electrodes and carbon-related materials. Impressively, the output voltage could also be improved to 2.5 V when using the organic electrolyte, and an ultra-high energy density of 4.75 mF‧V2‧cm− 2 at Φ120 = 80.6° can also be handily achieved. Moreover, both aqueous and organic ECs-SVGAs can well smooth arbitrary AC waveforms into DC signals, indicating that ECs-SVGAs have colossal potentials to replace outmoded AECs.
Vertical Graphene Arrays for AC Line-Filtering Capacitors
