Cation Group‐Driven Dual‐Track Regulation Enables Dendrite‐Free and Low‐Temperature Zn‐Ion Hybrid Supercapacitors

ABSTRACT Despite their promising potential, the advancement of zinc‐ion hybrid supercapacitors (ZHSCs) is significantly impeded by sluggish zinc‐ion migration, parasitic side reactions, and dendrite growth, challenges that are exacerbated under low‐temperature conditions. Current research predominantly focuses on zinc ions, while the critical role of anions in mediating these degradation pathways has been largely overlooked. Herein, we present a “cation group‐driven dual‐track regulation” strategy by engineering a cationic hydrogel electrolyte composed of poly(acryloyloxyethyl trimethyl ammonium chloride) (PDAC) and ZnCl 2 . The immobilized quaternary ammonium groups (─N + (CH 3 ) 3 ) electrostatically confine Cl ‒ anions, thereby creating highly efficient Zn 2+ ‐selective migration channels and suppressing competing side reactions. Simultaneously, these cationic groups adsorb onto high‐energy zinc crystal facets, guiding (002)‐oriented Zn deposition and effectively inhibiting dendrite growth. The optimized PDAC‐based electrolyte delivers a high ionic conductivity of 5.3 mS cm −1 at −50°C, a Zn 2+ transference number of 0.87, and exceptional average reversibility of Zn plating/stripping (98%) in Zn||Cu cells down to −40°C. Moreover, PDAC‐optimized ZHSCs demonstrate outstanding cyclability over 20 000 at −40°C (95.2% capacity retention). This work establishes a generalizable electrolyte design paradigm that concurrently addresses kinetic and interfacial limitations, paving the way for dendrite‐free, high‐performance Zn‐based energy storage systems operable under low‐temperature conditions.