Molecularly engineered organic-inorganic gel electrolyte with hierarchical Zn2+ coordination for ultra-stable, cryogenic-tolerant flexible zinc-ion hybrid supercapacitors

This work presents a molecular-level design strategy for organic-inorganic composite gel electrolytes to address the performance degradation of aqueous zinc-ion hybrid supercapacitors (ZIHSs) under low-temperature conditions. A three-dimensional interpenetrating polymer network was constructed to synergistically enhance mechanical strength and ion transport kinetics. By integrating a water-ethylene glycol (EG) binary solvent system with ZnSO 4 electrolyte, the coordination hierarchy of Zn 2+ was modulated as Zn 2+ -SO 4 2+  > Zn 2+ -EG > Zn 2+ -H 2 O, where the preferential Zn 2+ -EG interaction facilitates rapid solvent exchange and accelerates Zn 2+ migration in EG-containing electrolytes. This molecular engineering strategy effectively resolves the ion transport limitations of conventional hydrogel electrolytes at subzero temperatures: the optimized electrolyte membrane exhibits excellent wide temperature range adaptability, and its ionic conductivity changes from 19.25 mS·cm −1 at room temperature to 11.11 mS·cm −1 at −30 °C. Furthermore, the dynamic Zn 2+ coordination network formed in situ enables uniform charge distribution, achieving ultrastable Zn plating/stripping in symmetric cells (1390 h cycling). The quasi-solid-state ZIHS device demonstrates an ultra-high specific capacity of 267.3 F·g −1 at 2 V operating voltage, and its energy density (165.22 Wh·kg −1 ). This work establishes a novel paradigm for designing wide-temperature-range zinc-based energy storage systems through molecular-scale electrolyte engineering.