Stable Zinc Metal Battery Development: Using Fibrous Zirconia for Rapid Surface Conduction of Zinc Ions With Modified Water Solvation Structure

The two most critical technical issues in Zn-based batteries, dendrite formation, and hydrogen evolution reaction, can be simultaneously addressed by introducing negatively charged fibrous ZrO₂ as a separator. Electron redistribution between ZrO₂ and Zn²⁺ ions renders the ZrO₂ surface a preferred adsorption site for Zn²⁺ ions, making surface conduction the primary ion-transport mode. Surface conduction enables fibrous ZrO₂ to exhibit a 6.54 times higher single-Zn-ion conductivity than that of conventional glass fiber, minimizing the concentration gradient of Zn²⁺ and suppressing dendrite formation. Additionally, strong Zr─O─Zn bonding stabilizes the Zn²⁺ ions with fewer solvated H₂O molecules (≈2), preventing water molecules from approaching the electrode surface, as evidenced by a 58.8% decrease in the hydrogen evolution rate. Consequently, the cycling stability of a fibrous-ZrO₂-based Zn/Zn symmetric cell (3000 h at 1 mAh cm⁻² and 5 mA cm⁻²) is approximately ten times greater than that of the conventional variant. Furthermore, a fibrous-ZrO₂-based Zn–I₂ full cell exhibits a notably high energy density (271.4 Wh kg⁻¹) as well as a long lifespan (≈5000 cycles) at an ultrahigh current density (4 A g⁻¹).