Eutectic Crystallization Activates Solid‐State Zinc‐Ion Conduction

Abstract

Solid-state zinc (Zn) batteries offer a new candidate for emerging applications sensitive to volume, safety and cost. However, current solid polymeric or ceramic electrolyte structures remain poorly conductive for the divalent Zn²⁺ , especially at room temperature. Constructing a heterogeneous interface which allows Zn²⁺ percolation is a viable option, but this is rarely involved in multivalent systems. Herein, we construct a solid Zn²⁺ -ion conductor by inducing crystallization of tailored eutectic liquids formed by organic Zn salts and bipolar ligands. High-entropy eutectic-networks weaken the ion-association and form interfacial Zn²⁺ -percolated channels on the nucleator surfaces, resulting in a solid crystal with exceptional selectivity for Zn²⁺ transport (t <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow></mml:mrow> <mml:mrow><mml:mi>Zn</mml:mi> <mml:msup><mml:mrow></mml:mrow> <mml:mrow><mml:mn>2</mml:mn> <mml:mo>+</mml:mo></mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> =0.64) and appreciable Zn²⁺ conductivity (σ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow></mml:mrow> <mml:mrow><mml:mi>Zn</mml:mi> <mml:msup><mml:mrow></mml:mrow> <mml:mrow><mml:mn>2</mml:mn> <mml:mo>+</mml:mo></mml:mrow> </mml:msup> </mml:mrow> </mml:msub> </mml:math> =3.78×10^-5 S cm^-1 at 30 °C, over 2 orders of magnitude higher than conventional polymers), and finally enabling practical ambient-temperature Zn/V₂ O₅ metal solid cells. This design principle leveraged by the eutectic solidification affords new insights on the multivalent solid electrochemistry suffering from slow ion migration.