Aligned Nanostructures Resolve Zn 2+ Transport Bottlenecks via Interfacial Kinetics–Diffusion Coupling in Aqueous Zinc‐Ion Batteries

Abstract Aqueous zinc‐ion batteries (AZIBs) have garnered significant attention as a safe and cost‐effective alternative to lithium‐ion batteries for grid‐scale energy storage. However, their performance is hindered by sluggish Zn 2+ diffusion within the cathode and structural degradation. While pre‐intercalation strategies have demonstrated improvements in electrochemical performance, the comprehensive understanding between synthesis‐driven evolution, Zn 2+ diffusion, and interphase kinetics remains underexplored. Herein, it is investigated how synthesis time influences the structure and morphology of K 2 V 6 O 16 ·nH 2 O cathodes, as well as their Zn 2+ diffusion and charge transfer kinetics. By coupling operando‐ electrochemical impedance spectroscopy (EIS) and COMSOL simulation, that interfacial Zn 2 ⁺ accumulation, induced by limited solid‐state diffusion within the cathode, leads to pronounced transport bottlenecks—despite sufficient charge‐transfer kinetics is identified. This imbalance distorts the Zn 2+ flux directionality and creates spatial heterogeneity in ion transport. Notably, these bottlenecks are effectively alleviated by 1D nanostructured architectures, which promote continuous ion transport and facilitate interfacial reaction kinetics. Consequently, K 2 V 6 O 16 ·nH 2 O exhibits a tenfold increase in Zn 2+ diffusivity and 97.26% capacity retention over 5000 cycles. These findings offer valuable insights into the rational design of high‐performance AZIB cathodes through synthesis‐driven structural control.