Atomic Level-Macroscopic Structure-Activity of Inhomogeneous Localized Aggregates Enabled Ultra-Low Temperature...

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.