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Despite promising performance at ambient temperature, the development of aqueous zinc batteries is jeopardized by the freeze of aqueous electrolytes and deteriorative electrode‐electrolyte interphase at low temperatures. Herein, inspired by the cryoprotective mechanism of extracellular polysaccharides in biological organisms, a quaternized galactomannan polysaccharide (q‐GPA) is proposed as a cryoprotective additive for improving low‐temperature performance of aqueous zinc batteries. Mechanistic studies revealed that a multi‐hydroxyl galactomannan backbone can substantially attenuate the activity of water molecules through the reconfiguration of the hydrogen bond network, which inhibits ice crystal formation at subzero temperatures and thus depress the freezing point of the electrolyte. Meanwhile, the quaternary ammonium groups tethered on the q‐GPA skeleton are intended to neutralize the interfacial electric field through electrostatic repulsion, thereby accelerating Zn2+ deposition kinetics and prohibiting zinc dendrite growth. Impressively, the q‐GPA–modified electrolyte enables an extended lifespan of over 1700 h in Zn||Zn symmetric battery at a high current density of 3 mA cm−2 and an ultralong cycle life of 5000 cycles with a capacity retention of 99.2% in the Zn||Na2V6O16·1.5H2O (NVO) full battery at −30 °C. This work provides unprecedented possibilities for optimizing the electrolyte formulation of low‐temperature aqueous batteries. [ABSTRACT FROM AUTHOR]

Aqueous zinc (Zn) batteries are highly desirable for sustainable and large-scale electrochemical energy storage technologies. However, the ceaseless dendrite growth and the derived dead Zn are principally responsible for the capacity decay and insufficient lifespan. Here, we propose a dissolved oxygen-initiated revitalization strategy to reactivate dead Zn via ferrocene redox chemistry, which can be realized by incorporating a trace amount of poly(ethylene glycol) as a solubilizer to improve the solubility of water-insoluble ferrocene derivatives. Ferrocene scaffold can be spontaneously oxidized to ferricenium cations by dissolved oxygen, which eradicates the dissolved oxygen-involved Zn corrosion and insulating by-product generation. Subsequently, the generated ferricenium cations as the scavenger can rejuvenate electrically isolated dead Zn into electroactive Zn2+ ions to compensate the zinc loss. Through this design, the symmetric cell exhibited improved cycle life of 3700 h at 10 mA cm-2, and 220 h under a high depth of discharge of 80%. Importantly, the Zn||NaV3O8·1.5H2O full cells demonstrated the impressive cycling stability over 1000 cycles at a low N/P ratio of 3.0. This work presents an innovative solution for the revitalization of dead Zn to extend the lifespan of deep-cycling metal batteries., (© 2024 Wiley‐VCH GmbH.)