Atomic Level‐Macroscopic Structure‐Activity of Inhomogeneous Localized Aggregates Enabled Ultra‐Low Temperature Hybrid Aqueous Batteries.

The utilization of hybrid aqueous electrolytes has significantly broadened the electrochemical and temperature ranges of aqueous batteries, such as aqueous zinc and lithium‐ion batteries, but the design principles for extreme operating conditions remain poorly understood. Here, we systematically unveil the ternary interaction involving salt‐water‐organic co‐solvents and its intricate impacts on both the atomic‐level and macroscopic structural features of the hybrid electrolytes. This highlights a distinct category of micelle‐like structure electrolytes featuring organic‐enriched phases and nanosized aqueous electrolyte aggregates, enabled by appropriate low donor number co‐solvents and amphiphilic anions. Remarkably, the electrolyte enables exceptional high solubility, accommodating up to 29.8 m zinc triflate within aqueous micelles. This configuration maintains an intra‐micellar salt‐in‐water setup, allowing for a broad electrochemical window (up to 3.86 V), low viscosity, and state‐of‐the‐art ultralow‐temperature zinc ion conductivity (1.58 mS cm−1 at −80 °C). Building upon the unique nature of the inhomogeneous localized aggregates, this micelle‐like electrolyte facilitates dendrite‐free Zn plating/stripping, even at −80 °C. The assembled Zn||PANI battery showcases an impressive capacity of 71.8 mAh g−1 and an extended lifespan of over 3000 cycles at −80 °C. This study opens up a promising approach in electrolyte design that transcends conventional local atomic solvation structures, broadening the water‐in‐salt electrolyte concept. [ABSTRACT FROM AUTHOR]