Evolution of Frustrated Coordination in Eutectic Electrolyte Driven by Ligand Asymmetry toward High-Performance Zinc Batteries.

Abstract

Eutectic electrolytes hold promise for aqueous zinc metal batteries in sustainable energy storage chemistries, yet improvement from perspective of molecule configurational engineering are ambiguous. Herein, we propose design strategy of increasing asymmetric molecular geometry in organic ligands to regulate frustrated coordination and disordered structure for eutectic electrolytes toward enhanced zinc metal batteries. The introduced asymmetry in eutectic component gives rise to relatively weak coordination strength and configurational disorder interaction among cation-anion-ligand, leading to suppressed local aggregation, steady eutectic phase and improved Zn2+diffusion kinetics. Such highly frustrated coordination state also enables disruption of hydrogen bonding network and reinforcement of anion participation, which results in confined side reactions, decreased water activity and the formation of inorganic-enriched solid electrolyte interphase. In comparison to highly symmetric ligands, asymmetric ligand-involved eutectic electrolytes with configurational disorderdeliver high Coulombic efficiency of 99.4 %, stabilized Zn plating/stripping of 5000 h and impressive rate capability even under harsh conditions such as small N/P, low temperature. The rationale in this work advances the deep understanding of asymmetric molecular engineering in eutectic electrolytes and showcases suitability of frustrated coordination to achieve high-performance zinc metal batteries.