A Near-Single-Ion Conducting Protective Layer for Dendrite-Free Zinc Metal Anodes

Abstract

The instability of zinc metal anodes, including dendrite formation and corrosion, limits their application in aqueous zinc-ion batteries (AZIBs). Here, a near-single zinc-ion conducting (NSIC) protective layer that enables dendrite-free Zn anodes by integrating Zn²⁺-conducting polymer matrices with counter-anion trapping agents is presented. Sulfonic acid groups, covalently bonded to polymeric backbones enhance Zn²⁺ ion mobility while counter-anions are immobilized by amine-functionalized metal-organic frameworks embedded within the polymer layer. This synergistic combination enables near single zinc ion transport (t_Zn²⁺ = 0.91). The NSIC layer extends sand's time and promotes uniform Zn deposition along the (002) orientation, preventing dendrite formation. Consequently, full cells with thin Zn@NSIC anodes (14 µm) exhibit stable cycling performance over 5000 cycles at 5 A g⁻¹, with a low negative-to-positive areal capacity (NP) ratio of 3.3 and a Zn depth of discharge exceeding 30%. Furthermore, the NSIC layer is also adapted for enlarged Zn anodes (80 cm²) in large-sized full cells, delivering stable operation with a capacity of ≈300 mAh at 1 A g⁻¹. These results offer valuable insights into ion transport control within protective layers, advancing the development of practical AZIBs with high anode reversibility.