Mg²⁺ Ion Exchange for Constructing a Stable 2D Interlayer toward a Zinc-Ion Battery at a High Rate

The commercialization of aqueous zinc-ion batteries is hindered by the growth of irreversible dendrites at the anode interface. While metal–organic framework (MOF)-based coatings can homogenize ion flux, their structural and electrochemical stability degrades severely under high-rate operation, accelerating localized dendrite nucleation. Here, we develop a cation-substituted two-dimensional zeolitic imidazolate framework (M-2D ZIF-8) through a Mg²⁺/Zn²⁺ ion-exchange route. Replacing Zn²⁺ nodes with Mg²⁺ not only preserves the 2D layered architecture but also enhances framework robustness and facilitates regulated Zn²⁺ transport. The resulting M-2D ZIF-8 interphase stabilizes Zn deposition, enabling symmetric cells to cycle stably more than 1000 h at 5 mA cm⁻² and 5 mA h cm⁻², five times longer than those of cells with unmodified ZIF-8 coatings. When paired with a Zn_xV₂O₅·nH₂O cathode, after 2500 cycles, the coated anode maintains 81.4% of its capacity, with a reversible capacity of 210 mA h g⁻¹ at 3 A g⁻¹. This work demonstrates that targeted cationic exchange in 2D MOFs offers an effective route to high-rate, dendrite-suppressed zinc metal anodes.