Ionically Cross‐Linked Composite Hydrogel Modulating an Electrical Double Layer on Zn Metal Anodes for Enhanced Kinetics and Stability

Abstract Achieving high interfacial kinetics for Zn metal anodes, without triggering the hydrogen evolution reaction (HER) and corrosion, remains a challenge. Particularly, studies on promoting kinetics in an H₂O‐poor electrical double layer (EDL) are extremely rare. This study introduces a macromolecular hydrogel interfacial layer, comprising alginate (Alg), poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) (PAMPS), and polyaniline (PANI) (APP), to address this issue by engineering the EDL on Zn. The APP layer facilitates Faradaic processes such as de‐solvation and surface diffusion through PANI, while suppressing the HER and corrosion through an H₂O‐poor and SO₄²⁻‐poor EDL. The uniform distribution of the electric field and ion flux, along with the high mechanical stability offered by APP, effectively mitigates Zn dendrite growth. Consequently, APP‐Zn electrodes demonstrate excellent electrochemical performance, including a high Coulombic efficiency (≈99.6%) over 700 cycles at 10 mA cm⁻² in asymmetric cells and a high cumulative capacity of 1.8 Ah cm⁻² in symmetric cells.