Hierarchically porous 3D Y-branched carbon tube grids for high-performance filter capacitors

The rapid development of sustainable green energy, which often generates fluctuating electrical signals, has driven the demand for high-performance filter capacitors in alternating/direct current conversion. Replacing bulky aluminum electrolytic capacitors with electric double-layer capacitors（EDLCs） holds promise for electronics miniaturization. However,EDLCs face a trade-off between charge storage ability and ion/electron transport speed. Here, we demonstrate three-dimensional Y-branched carbon tube（3D-YCT） grids with a hierarchically porous structure as electrodes for line-filtering EDLCs.The branching patterns and positions within the 3D-YCT are precisely tailored through the nanochannels inside anodic aluminum oxide templates. These integrated 3D Y-branched CT arrays provide unobstructed pathways for fast frequency response and extensive surfaces for high capacitance. The resulting 3D-YCT-based EDLC achieves a desirable specific areal capacitance（CA） of 3.6 mF cm-2 with a phase angle of-80° at 120 Hz, outperforming most reported line-filtering EDLCs and demonstrating excellent line-filtering performance. These findings offer valuable insights for constructing miniaturized filter capacitors.