Filtering capacitors with wide operating voltage range are essential for smoothing ripples in line-powered system, which are still unsatisfactory due to low energy density and limited working voltage scopes. Herein, we report an aqueous hybrid electrochemical capacitor with areal specific energy density of 1.29 mF V2 cm−2 at 120 Hz, greater than common aqueous ones. Interestingly, it can be easily integrated at scale to show excellent flexibility, controllable and stable filtering performance, in which an integrated device (e.g., seven units in series) exhibits fluctuation of 96 mV, 10 times smaller than an aluminum electrolytic capacitor with similar capacitance. A record-high 1,000 V can also be achieved after integrating 670 units, exceeding those reported so far, and about 1.5 times of commercial bulk aluminum electrolytic capacitors (~700 V). This work opens up a new insight for promising applications in multiple electricity transmission systems that requiring high smoothness under harsh voltage.

Compared with currently prevailing Li-ion technologies, sodium-ion energy storage devices play a supremely important role in grid-scale storage due to the advantages of rich abundance and low cost of sodium resources. As one of the crucial components of the sodium-ion battery and sodium-ion capacitor, electrode materials based on biomass-derived carbons have attracted enormous attention in the past few years owing to their excellent performance, inherent structural advantages, cost-effectiveness, renewability, etc. Here, a systematic summary of recent progress on various biomass-derived carbons used for sodium-ion energy storage (e.g., sodium-ion storage principle, the classification of bio-microstructure) is presented. Current research on the design principles of the structure and composition of biomass-derived carbons for improving sodium-ion storage will be highlighted. The prospects and challenges related to this will also be discussed. This review attempts to present a comprehensive account of the recent progress and design principle of biomass-derived carbons as sodium-ion storage materials and provide guidance in future rational tailoring of biomass-derived carbons.