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

The integration of Zn²⁺ ion-conducting groups (−SO₃H) in the polymer matrix and counter-anion trapping groups (−NH₃⁺) in the embedded nanoparticles enables the protective layer to achieve a Zn²⁺ transference number (t _Zn ²⁺) close to unity. This advanced design improves the uniformity of the deposition current, prolongs Sand's time, and mitigates dendrite formation.

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 _Zn ²⁺ = 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.