Catalyst–Electrolyte Synergy Enables Ultrafast and Long‐Life Two‐Electron Aqueous Zinc–Iodine Batteries

ABSTRACT Two‐electron aqueous Zn–I 2 batteries deliver doubled cathode capacity yet remain constrained by the thermodynamic instability of I + and sluggish, multistep interfacial kinetics. By systematically correlating electrochemical behavior with ZnCl 2 concentration, we demonstrate that strengthened Cl − coordination mitigates ICl hydrolysis but concurrently aggravates charge‐transfer resistance. Thus, suppressing hydrolysis alone proves insufficient, underscoring the need to address interfacial kinetics. To address this, we design a single‐atom catalytic confinement host featuring atomically dispersed Co–N 4 sites on N‐doped carbon hollow nanospheres (CoSAs@NC). These isolated Co sites strongly chemisorb polyiodides, expedite electron exchange, and facilitate Zn 2+ transport within a hierarchically mesoporous framework, coupling high stability with fast kinetics. Operando spectroscopy and kinetic analyses reveal that atomic catalysis significantly decreases the Tafel slope, enhances exchange current density, and reduces charge‐transfer resistance. With high‐iodine‐content cathode, Co‐SAs@NC‐based cells achieve 190.6 mAh g −1 at 30 A g −1 , and ultralong cycling stability with only 0.00179% capacity decay per cycle over 20000 cycles. Pouch cells deliver high energy density of 218.6 Wh kg − 1 (based on total electrode mass). This integrated catalysis–confinement strategy resolves the intrinsic stability–kinetics trade‐off, advancing practical, high‐rate Zn–I 2 energy storage.