Biomass‐Derived Ion‐Selective Binder Modulates Zn 2+ Solvation Enabling High‐Capacity Cathodes in Aqueous Zinc Batteries

Abstract The electrochemical performance of aqueous zinc batteries (AZBs) critically relies on advanced binders to regulate the solvation structure of hydrated Zn 2+ and accelerate the redox kinetics at the cathode interface. However, conventional hydrophobic polyvinylidene fluoride (PVDF) binders fail to achieve this goal due to their weak interactions with H 2 O and Zn 2+ . Here, we present a bioinspired sulfate‐rich polysaccharide binder network derived from marine ι‐carrageenan (CAG), which mimics biological ion channels to enable selective ion coordination and dynamic hydration regulation. By establishing dual ion‐selective coordination sites, the zincophilic ─OSO 3 − and hydrophilic ─OH groups of CAG form Zn 2+ ─OSO 3 − and H 2 O─OH interactions, effectively disrupting the primary solvation shell of Zn 2+ ─H 2 O and accelerating Zn 2+ desolvation kinetics, thereby enabling adaptive ion transport across the cathode interface. Consequently, Zn||CAG@Mn 0.15 V 2 O 5 ·nH 2 O batteries deliver an ultrahigh capacity of 421 mAh g −1 at 0.6 A g −1 , which is 76% higher than PVDF‐based counterparts (239 mAh g −1 ). This water‐processable binder demonstrates universal applicability across various cathode materials (e.g., MnO 2 , V 2 O 5 , and organics), providing a green, scalable solution for high‐performance AZBs. This study establishes a biomimetic binder design paradigm, where sulfate‐hydroxyl dual coordination emulates biological ion transport, enabling precise regulation of Zn 2+ solvation and interfacial chemistry.