High-frequency AC line filtering with silicon carbide-based flexible supercapacitors

Filtering supercapacitors (SCs) are emerging as a potential alternative to bulky aluminum electrolytic capacitors (AECs) for compact power filter electronics, thanks to their high capacitance and fast charge/discharge performance. However, achieving high-frequency responsiveness and effective ripple suppression remains a significant challenge. Although silicon carbide (SiC) has demonstrated great potential as a supercapacitor electrode material, its capabilities for high-frequency applications have not been fully realized due to limitations in current fabrication methods. Therefore, ultra-ultrafast flexible symmetric supercapacitors (FSSCs) using SiC thin films with finely tailored porous nanostructures are fabricated using a binder-free magnetron sputtering method for stable filtering over a wide frequency range. The optimized FSSCs deliver an impressive high-frequency response (f0) of 3.2 kHz, a high volumetric capacitance of 0.67 F cm−3 at 120 Hz, and an outstanding cycling stability of 84.39% after 25 000 cycles. This superior performance is attributed to the synergistic effect of the nanocauliflower morphology and the ultrathin electrode design, which facilitates surface-dominated charge storage and shortens ion transport pathways for efficient alternating current (AC) line filtering. Furthermore, the FSSC smooths the AC signal (2.65 V; 50 Hz) into a direct current (DC) output, exhibiting an 80 mV fluctuation, 4.5 times smaller than that from the AEC (360 mV). The FSSCs successfully filter AC waveforms at a high frequency of 2 kHz into stable DC signals with minimal ripple, underscoring their potential for next-generation electronics.