Construction of Homogeneously Porous Composite Hydrogel Electrolyte for Dendrite‐Free Aqueous Zinc‐Ion Batteries: An Alkali‐Etched Graphitized‐Carbon Nitride Induced Polymerization Strategy

ABSTRACT Aqueous zinc‐ion batteries (AZIBs) are promising for safe, large‐scale energy storage but suffer from dendrite growth and side reactions in liquid electrolytes. While hydrogel electrolytes can mitigate leakage, their electrochemical performance is often limited by slow ion transport and poor mechanics. Herein, a uniformly porous composite hydrogel electrolyte (CN‐PAM) was constructed via an alkali‐etched graphitized carbon nitride (g‐C 3 N 4 )‐induced polymerization strategy. The hydroxyl‐modified porous g‐C 3 N 4 nanosheets serve as a multifunctional cross‐linker, reinforcing the polyacrylamide (PAM) hydrogen‐bond network and pore channel skeleton. This results in a homogeneous 3D porous structure (1.59 µm), exceptional mechanical strength (stress: 119.3 kPa, strain: 840%), high ionic conductivity (22.21 mS cm −1 ), and an elevated Zn 2+ transference number (0.80). The strengthened composite hydrogel network regulates Zn 2+ flux and immobilizes free water, effectively suppressing dendrite growth and parasitic reactions. Consequently, Zn||Zn symmetric cells with CN‐PAM electrolyte achieve ultra‐stable cycling for over 3000 h at 1 mA cm −2 /1 mAh cm −2 . When matched with an NVO cathode, the full cell delivers a high reversible capacity of 194.7 mAh g −1 and maintains 92.6% capacity retention after 1000 cycles at 10 A g −1 . This work provides a facile template strategy for designing high‐performance hydrogel electrolytes toward durable and high‐safety AZIBs.