Balancing interfacial protection and Zn²⁺ transport via an isomalt additive for stable zinc anodes

Aqueous zinc-ion batteries (AZIBs) have attracted significant attention owing to their intrinsic safety, low cost, and abundant zinc resources. However, their practical deployment is hindered by dendrite formation on the Zn anode, the hydrogen evolution reaction (HER), and severe corrosion induced by the high reactivity of water molecules. Electrolyte additives have been widely investigated to stabilize the Zn/electrolyte interface; however, most reported additives inevitably impede Zn²⁺ transport and retard interfacial reaction kinetics during the formation of a protective adsorption layer. Herein, we introduce isomalt (IM), a low-cost polyol with abundant hydroxyl groups, as a multifunctional electrolyte additive to simultaneously balance interfacial protection and Zn²⁺ transport. Zincophilic IM molecules strongly adsorb on the Zn surface, thereby reconstructing a water-deficient electric double layer (EDL) and effectively suppressing parasitic side reactions. Simultaneously, IM participates in the Zn²⁺ solvation structure and reconstructs the hydrogen-bond network, thereby reducing water activity while simultaneously accelerating Zn²⁺ desolvation and ion transport. This synergistic regulation promotes preferential Zn deposition along the (002) crystallographic plane, enabling uniform and dendrite-free Zn growth without compromising ion transport kinetics. Consequently, Zn‖Zn symmetric cells with the IM-modified electrolyte exhibit outstanding cycling stability for over 2700 h at 1 mA cm⁻² and 0.5 mA h cm⁻² while maintaining low voltage polarization throughout cycling. Under identical conditions, Zn‖Cu half-cells demonstrate stable operation over 1500 cycles with an average coulombic efficiency of 99.36%. Zn‖MnO₂ full cells retain 85.63% of their initial capacity after 1500 cycles at a current density of 1 A g⁻¹. Meanwhile, Zn‖MnO₂ pouch cells retain 81.56% of their capacity after more than 360 cycles, highlighting their strong potential for practical applications. These results indicate that IM is an effective additive. This study provides a promising strategy for developing high-performance and scalable aqueous zinc-ion batteries.