High-Entropy Electrolytes Downsizing Solvated Clusters and Enabling Parallel Ion Transport for Low-Temperature Aqueous Zinc Batteries

Rechargeable zinc-based batteries are promising candidates for electrochemical energy storage, but their deliverable capacity, rate capability, and cycle performance are limited by conventional aqueous electrolytes at low temperatures. Here, we report an aqueous electrolyte formulation by increasing the chloride salt diversity to maximize both mixing and excess entropies. In a ternary-chloride-salt electrolyte, we reveal that the increased mixing entropy can tune the coordination environments, which disrupts the hydrogen-bonding network and reduces the aggregation of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mo>[</mml:mo><mml:msub><mml:mrow><mml:mi>ZnCl</mml:mi></mml:mrow><mml:mrow><mml:mi>m</mml:mi></mml:mrow></mml:msub><mml:mo>]</mml:mo></mml:mrow><mml:mi>n</mml:mi><mml:mrow><mml:mn>2</mml:mn><mml:mi>n</mml:mi><mml:mo>-</mml:mo><mml:mi>m</mml:mi><mml:mi>n</mml:mi></mml:mrow></mml:msubsup></mml:math> clusters to increase tetrahedral entropies and total pair-correlation excess entropies. The high-entropy electrolyte exhibits a lower freezing temperature, higher ionic conductivity, and diverse and small solvated clusters at low temperatures. Furthermore, the entropy-mediated solvation structures desolvate and access the Zn anode in a parallel process with a high Zn²⁺ flux for uniform plating and stripping, which breaks through the traditional sequential isolated desolvation/deposition pathway of large aggregated clusters that induce dendritic anode morphology. The formulated electrolyte endows Zn||Zn cells with stable cycling over 13320 h at 1 mA cm^-2 with 99.97% average Coulombic efficiency for Zn plating/stripping and matches cathodes of tetrachlorobenzoquinone, VOPO₄·<i>x</i>H₂O or Na₃V₂(PO₄)₃ to enable full cells working at -60 °C.