Constructing an interconnected gel with ionic fluid channels for AC line-filtering

Electric double-layer capacitors operating at 120 Hz are promising alternatives to bulky aluminum electrolytic capacitors for AC line-filtering. However, a pivotal challenge in developing high-performance filtering electrodes is achieving the rapid ion response of pathways without compromising high capacity. Here, we construct a 3D interconnected gel framework consisting of reduced graphene oxide (rGO) and carboxylated multi-walled carbon nanotubes (MWCNTs), featuring ionic fluid channels. The mixed MWCNTs effectively inhibit the re-stacking of rGO, forming an interconnected open network that ensures high-density electron transport and ultra-fast ionic accessibility. Systematic investigations reveal that the electrochemical performance is governed by a synergistic balance among conductive continuity, interfacial wettability, and open fluid ion-transport channels. The optimized electrode achieves an ultralow series resistance of 43.5 mΩ cm² and a high areal capacitance of 3.56 mF cm^-2 at 120 Hz (φ = -81.1°). This study is the first to apply fluid gel channels to filtering capacitors, providing a reliable theoretical basis for advanced carbon-based electrochemical capacitors in the next generation of power electronic systems.