Dynamic Proton‐Coordination Equilibrium Enables Nonfreezing Ion Transport for Ultralow‐Temperature Zinc Batteries

ABSTRACT Hydrogel electrolytes (HEs) are promising for aqueous zinc batteries, yet suffer from freezing‐induced loss of ionic transport and interfacial instability at subzero temperatures. Here we report a proton‐mediated coordination equilibrium that enables nonfreezing Zn 2+ transport in hydrogel electrolytes under ultralow‐temperature conditions. By coupling phytic acid with zinc phytate, proton activity and Zn–O coordination are dynamically balanced, continuously reconstructing the local hydration environment to suppress hydrogen‐bond ordering, stabilize bound water, and prevent water crystallization. Simultaneously, reversible coordination exchange sustains Zn 2+ dissociation and migration through a hopping transport mechanism. At the Zn anode, proton‐mediated interfacial evolution drives the formation of a ZnS/Zn 3 (PO 4 ) 2 ‐rich hybrid interphase that accelerates interfacial kinetics and suppresses degradation. Consequently, the optimized electrolyte achieves an ionic conductivity of 2.4 mS cm − 1 and an apparent Zn 2+ transference number of 0.24 at −60°C, enabling Zn||Zn cells to cycle stably for over 3400 h and Zn||PANI full cells to retain 60.1% of their capacity after 4000 cycles at −60°C. These findings identify proton‐mediated coordination equilibrium as a general mechanism for preserving ionic transport in frozen aqueous environments and provide a blueprint for low‐temperature electrochemical energy storage.