Microphase‐Separated Hydrogel Electrolytes with Selective Ion Transportation Pathways for Flexible Zinc‐Ion Batteries

Abstract Flexible aqueous zinc‐ion batteries (ZIBs) are promising candidates for next‐generation wearable electronics and soft robotics, yet their development is hindered by the non‐selective ion transport of conventional hydrogel electrolytes, which induces concentration polarization, uneven Zn 2+ flux, and dendrite formation, ultimately causing battery failure. Here, a microphase‐separated single‐zinc‐ion conducting hydrogel electrolyte (SIHE) constructed via polymer chain disentanglement within a polyanionic zinc‐alginate (ZA) matrix is reported. Due to the pronounced steric disparity between Zn 2+ and the alginate chains, ZA holds intrinsic potential for ion‐selective transport. However, spontaneous chain entanglement within the alginate network under the applied electric field severely impedes the formation of continuous ion transport pathways, limiting Zn 2+ conduction. By incorporating Nafion, well‐defined hydrophilic/hydrophobic domains are induced that simultaneously relax the entangled polymer network and establish continuous Zn 2+ ‐conducting pathways. This microstructural engineering enables a high Zn 2+ transference number of 0.967 and ionic conductivity of 25.5 mS cm −1 , resolving the long‐standing trade‐off between ion selectivity and transport kinetics. The zinc‐alginate/Nafion (ZA/N) electrolyte enables dendrite‐free cycling for over 4600 h. The ZA/N‐based flexible ZIB retains 90% capacity after 5000 cycles at 10 A g −1 . This work presents a general strategy to engineer high‐performance SIHEs for safe and durable flexible zinc‐ion batteries.