Grain‐Boundary‐Rich SEI Synergizing with an H ₂ O‐Poor EDL Enables Multidimensional Interfacial Regulation for Stable Zn Anodes

ABSTRACT The reversibility and sustainability of aqueous zinc‐ion batteries (AZIBs) are drastically compromised by interfacial issues arising from the H 2 O‐rich electric double layer (EDL) and unstable solid‐electrolyte interphase (SEI). Herein, trace biomolecule additive, zinc hyaluronate (HA‐Zn), is introduced to synergistically construct a grain‐boundary‐rich SEI and an H 2 O‐poor EDL for stable zinc anodes. Mechanistic studies reveal that HA‐Zn preferentially adsorbs onto the Zn anode and reconstructs an H 2 O‐poor EDL, effectively suppressing the water‐related side reactions. Simultaneously, the centred tetra‐oxygen ligands chelate Zn 2+ ions at the interface to homogenize ions distribution. This reconfigured interface further promotes the in situ decomposition of HA‐Zn and SO 4 2− , generating an organic‐inorganic hybrid SEI with abundant Zn 2+ ‐conductive grain boundaries, which not only accelerates Zn 2+ transport but also guides oriented Zn(101) deposition. Benefiting from the designed interface comprising HA‐Zn adsorption and grain‐boundary‐rich SEI, the Zn||Zn symmetric cells achieve long lifespans exceeding 4700 h and 1700 h at 1 and 4 mAh·cm −2 , respectively. More significantly, the Zn||I 2 full cells retain 88.67% capacity retention rate after more than 15000 cycles at 2 A·g −1 , and the Zn||I 2 pouch batteries (0.3 Ah) maintain 86.34% capacity over 3300 cycles at 0.5 A·g −1 .