A research team led by Prof. MENG Guowen and Prof. HAN Fangming from Institute of Solid State Physics, Hefei Institutes of Physical Science (HFIPS), Chinese Academy of Sciences (CAS), along with Prof. WEI Bingqing from the University of Delaware, miniaturized line-filtering capacitors featuring "Matryoshka doll" structure electrodes, which provided a powerful and space-saving solution for line-filtering applications.

The research was published in Joule recently.

Filter capacitors are vital components in converting alternating current (AC) to direct current (DC) for powering electronic devices. Current market dominators, such as aluminum electrolytic capacitors (AECs), are bulky and limit miniaturization efforts. Electric double-layer capacitors (EDLCs), with higher specific capacitance, hold promise, but their traditional curved and complex pore structures hinder line-filtering applications due to poor frequency response.

In this research, they introduce a novel design to solve this problem. Scientists employed a three-dimensional interconnected porous anodized aluminum oxide (3D-AAO) template. Through meticulous deposition processes, they created a 3D framework comprising double-layer or triple-layer carbon tubes with a coaxial structure, resembling the nested layers of Matryoshka dolls. This configuration maximizes surface area for charge storage and promotes rapid electrolyte ion transport.

Assembling symmetrical EDLCs with these "Matryoshka doll" 3Dmulti-layer carbon tube (MLCT) electrodes yielded impressive results. Devices exhibited exceptional impedance phase angles and low resistance-capacitance time constants, indicating efficient ion transport. Specific areal capacitance surpassed commercial AECs by two orders of magnitude, with minimal energy loss and remarkable energy storage efficiency.

Further testing confirmed the series-connected device bank's excellent frequency response and filtering capabilities, effectively transforming various input signals into stable DC outputs. A practical demonstration showcasing the device's ability to filter pulse voltages and illuminate an light-emitting diode (LED) underscores its potential for high-performance miniaturized filter capacitors.

"This Matryoshka doll structure 3D-MLCT electrodes for supercapacitors display high specific capacitance and exceptional frequency response performance," said Prof. MENG, "it offers a groundbreaking approach to the creation of next-generation high-performance miniaturized filter capacitors."

Schematic illustration of the synthesis process of the "Matryoshka doll" 3D-MLCT and the 3D-MLCT-based filter capacitor (Image by CHEN Gan)