Alternatingly stacked thin film electrodes-based compact aqueous hybrid electrochemical capacitors for hundred-volts AC line filtering

Filtering capacitor with compact configuration and a wide range of operating voltage has been attracting increasing attention for the smooth conversion of the electric signal in modern circuits. Lossless integration of capacitor units can be regarded as one of the efficient ways to achieve a wider voltage range, which has not yet been fully conquered due to the lack of rational designs of the electrode structure and integration technology. This study presents an alternatingly stacked assemble technology to conveniently fabricate compact aqueous hybrid integrated filtering capacitors on a large scale, in which a unit consists of rGO/MXene composite film as a negative electrode and PEDOT:PSS based film as a positive electrode. Benefiting from the synergistic effect of rGO and MXene components, and morphological characteristics of PEDOT:PSS, the capacitor unit exhibits outstanding AC line filtering with a large areal specific energy density of 1,015 μF V² cm⁻² (0.28 μW h cm⁻²) at 120 Hz. After rational integration, the assembled capacitors present compact/lightweight configuration and lossless frequency response, as reflected by almost constant resistor–capacitor time constant of 0.2 ms and dissipation factor of 15% at 120 Hz, identical to those of the single capacitor unit. Apart from standing alone steadily on a flower, a small volume (only 8.1 cm³) of the integrated capacitor with 70 units connected in series achieves hundred-volts alternating current line filtering, which is superior to most reported filtering capacitors with sandwich configuration. This study provides insight into the fabrication and application of compact/ultralight filtering capacitors with lossless frequency response, and a wide range of operating voltage.