Self‐Regulated Gradient Hydrogel Electrolyte with Ultrafast Ion Channels for Robust Zinc‐Ion Batteries

ABSTRACT Hydrogel electrolytes are crucial for advancing safe and flexible aqueous zinc‐ion batteries. However, conventional homogeneous hydrogels suffer a trade‐off between fast Zn 2+ transport and stable Zn/electrolyte interfaces. Herein, we report a surface energy‐driven self‐regulated gradient hydrogel electrolyte (SRG‐HE) that resolves this conflict via a spatially modulated polymer network. The SRG‐HE shows dense layers at the Zn/SRG‐HE interfaces provide robust passivation, while a low‐density bulk supports rapid Zn 2+ diffusion. During in situ polymerization, amphiphilic Triton X‐100 induces spontaneous component migration and surface enrichment, forming a symmetric surface–bulk–surface gradient. The dense surface layers suppress free‐water activity to stabilize interfaces, whereas the hydrated bulk delivers high ionic conductivity (97.7 mS cm − 1 ). Polar groups in SRG‐HE further immobilize OTf − , enabling selective Zn 2+ transport with a high transference number of 0.88. Consequently, Zn||Zn cells cycle stably for 1365 h at 4 mA cm − 2 with uniform (002)‐textured deposition. When paired with V 2 O 5 cathodes, the full cells maintain a reversible capacity of 234 mAh g − 1 after 2000 cycles at 1000 mA g − 1 , achieving near 100% Coulombic efficiency. Even under mechanical deformation, SRG‐HE‐based pouch cells retain functionality, underscoring their potential for durable, high‐performance energy storage systems.