Linear Matching Strategy of Cathode–Anode Capacity and Kinetics Enhances the Performance of Sodium‐Ion Capacitors

ABSTRACT Sodium‐ion capacitors (SICs) have garnered significant attention as a new type of electrochemical energy storage device. However, their development is severely limited by the kinetics discrepancy between sluggish Na ⁺ storage anodes and rapid capacitive cathodes. To overcome this limitation, a novel slope‑dominant carbon material designated SC─O was utilized to demonstrate the feasibility of a capacity‑kinetics linear matching strategy for achieving enhanced performance in SICs. The SC─O anode maintains high‐capacity retention at high rates, enabling linear capacity–kinetics matching between the anode and cathode in SICs and thus achieving optimal performance. When integrated with an activated carbon (AC) cathode, the fabricated SIC demonstrates remarkable energy density (81.3 Wh kg ⁻¹ at 9891.2 W kg ⁻¹ ) and an ultralong lifespan (92.05% capacity retention after 12 000 cycles). This work provides important guidance for the future design of practical, high‐power, long‐cycle sodium‐ion capacitors based on high‐rate/high‐capacity battery‐type anodes.