Plasma-Designed Multifunctional Carbon Electrodes for High-Frequency Line Filtering Applications

Abstract

Demand for higher power efficiency devices to be used in the various miniatured and portable equipment has increased and led to significant growth in the electrochemical capacitors. Currently, different available electrochemical capacitors mostly deliver the highest performance at low frequencies (less than 1 Hz) due to the microporous electrode structures and configurations. Due to these reasons, the use of such capacitors is still not commercialized because of the insufficient supply of direct current at a higher frequency range (between 100 and 200 Hz). Considering the large-scale electricity applications mainly carried with alternating current (AC), it is important to develop electronic devices that work on AC power sources. At the same time, high-power energy devices require a constant DC supply for large-scale applications. Therefore, an advanced device that can sufficiently convert AC to DC has stimulated contemporary research and designing filtering capacitors is gaining research attention. For such capacitors, it is important to design electrode architectures with high electrical conductivity, minimum contact resistance and a thickness between 1 and 10 μm, which can be achieved by depositing active material directly on the current collector. Plasma-enabled techniques have the key advantage of designing electrode architectures directly on the nanostructures and providing the desired morphology and orientation, which is favorable to maximize material–electrolyte interaction and ion transport. In this work, structure-controlled carbon nanostructures were designed using a plasma-enabled deposition approach using the advantage of the plasma catalysis effect. The nanostructures were used in the electrochemistry applications as electrodes in the filtering capacitor for the AC to DC conversion. The deposited nanostructures were vertical carbon nanoforests composed of multiple carbon nanotubes. The plasma-designed electrodes delivered a high capacitance of 430 μF in the high-frequency range (100 Hz) with a phase angle of ∼ -80°, which is excellent for filtering applications. Using such electrode architectures, a prismatic prototype was designed to test the capability of the capacitor to efficiently convert AC to DC, and the designed prototype delivered a capacitance of 12 mF at 100 Hz with long-term filtering stability (above 3 h). This excellent capacitance performance and filtering capabilities of plasma-designed carbon nanostructures open future pathways to replace conventional aluminum electrolytic capacitors for line frequency applications.