Grotthuss Mechanism for Stable Zinc Anodes: Time-Resolved pH Buffering in Aqueous Batteries

In zinc ion batteries, the curtailed lifespan and diminished Coulombic efficiency are primarily ascribed to the hydrogen evolution reaction, surface corrosion, and rampant dendrites, all related to unstable interfacial pH at the anode. To tackle these challenges, hydrogen-bonded organic frameworks (HOFs) are designed possessing outstanding zincophilic and hydrogen storage capabilities on the surface of Zn, thereby creating a dendrite-free anode (MACA@Zn). By leveraging the innate and reversible proton-hopping mechanism of MACA, the interfacial pH at the anode is able to be controlled. In situ scanning electrochemical microscopy has demonstrated a time-resolved local pH buffering effect. Moreover, the presence of MACA induces preferential growth of the (002) plane, resulting in a uniform and dense Zn deposition layer. Consequently, the Zn//Zn cell with MACA@Zn anode delivers an exceptional cycling stability of ≈2000 h at 5 mA cm⁻² and 1 mAh cm⁻², with a high cumulative plating capacity of 4950 mAh cm⁻². When paired with an α-MnO₂ cathode, the cell retains a specific capacity of 70.4 mAh g⁻¹ after 990 cycles, demonstrating a capacity retention of 44.87%. This research emphasizes the multifunctional protective effects of HOFs on the anode surface and offers critical insights for advancing the development and real-world implementation of ZIBs.