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

Abstract

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.