Breaking the Kinetics–Loading Trade‐Off in Zinc‐Ion Hybrid Capacitors Through Synergistic Electron–Ion Transport Design

ABSTRACT Zinc‐ion hybrid capacitors (ZIHCs) are promising for safe, low‐cost, large‐scale energy storage, yet the poor kinetics of high‐mass‐loading carbon cathodes hinder their practical deployment. Most reported ZIHCs employ low mass loadings (< 2 mg cm − 2 ), resulting in overestimated electrochemical performance and limited practical relevance. Here, the kinetic limitations induced by high mass loading are systematically elucidated, and a synergistic transport‐engineering strategy is developed to overcome them. Increasing the mass loading from 2 to 10 mg cm − 2 causes severe rate deterioration, with capacity retention decreasing from 43.8% to 17.0% at 20 A g − 1 , accompanied by increased charge‐transfer resistance and nearly one‐order‐of‐magnitude suppression of Zn 2 + diffusion. To address these limitations, electronic and ionic transport are independently optimized through carbon nanotube (CNT) conductive networks and low‐tortuosity pore channels generated by directional freeze‐drying. While mesoporous carbons show limited benefits, aligned pore architectures accelerate ion transport, and CNTs effectively mitigate electronic resistance. Integrating these features enables simultaneous optimization of electron and ion pathways in thick electrodes. Consequently, a practical pouch cell with a high mass loading (10 mg cm − 2 ) and low N/P ratio (∼ 16.4) delivers 38.3 mAh g − 1 at 10 A g − 1 over 3000 cycles. This work establishes a scalable electrode‐design strategy for practical high‐mass‐loading ZIHCs.