Aligned Nanostructures Resolve Zn²⁺ Transport Bottlenecks via Interfacial Kinetics–Diffusion Coupling in Aqueous Zinc-Ion Batteries

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 Zn²⁺ diffusion within the cathode and structural degradation. While pre-intercalation strategies have demonstrated improvements in electrochemical performance, the comprehensive understanding between synthesis-driven evolution, Zn²⁺ diffusion, and interphase kinetics remains underexplored. Herein, it is investigated how synthesis time influences the structure and morphology of K₂V₆O₁₆·nH₂O cathodes, as well as their Zn²⁺ diffusion and charge transfer kinetics. By coupling operando- electrochemical impedance spectroscopy (EIS) and COMSOL simulation, that interfacial Zn²⁺ 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 Zn²⁺ 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, K₂V₆O₁₆·nH₂O exhibits a tenfold increase in Zn²⁺ 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.