Co-Regulation of Interface and Bulk for Enhanced Localized High-Concentration Electrolytes in Stable and Practical Zinc Metal Batteries

Abstract

Rechargeable zinc metal batteries (RZMBs) are promising for energy storage due to their high capacity and cost-effectiveness. However, their commercialization is hindered by challenges including dendrite growth, parasitic reactions, and cathode degradation, particularly under low current densities and negative/positive (N/P) capacity ratios. Localized high-concentration electrolytes offer potential solutions, but their reliance on high salt concentrations to replicate solvation structures of high-concentration electrolytes limits their practicality, due to diluent's inherent inertness that limits its role in interfacial chemistry. Here, we present a co-regulation strategy that integrates bulk and interfacial properties to develop an interfacial-enhanced localized high-concentration electrolyte (ILHCE). By incorporating non-coordinating 1,4-dioxane diluent and 1-ethyl-3-methylimidazolium (emim⁺) cations into dilute aqueous electrolytes, dioxane molecules are pulled into electric double layer (EDL) through the interaction between emim⁺ and dioxane, achieving a pronounced dilution effect from bulk electrolyte to the EDL. This generates an anion-rich and water-depleted EDL at both anode and cathode interfaces, enhancing Zn²⁺ transport dynamics, ensuring cathode stability and deriving a robust anion-derived solid-electrolyte interphase. Full batteries using Mn_0.5V₆O₁₃ cathodes with a low N/P ratio of 1.77 demonstrate 80% capacity retention over 300 cycles at 0.2 A g⁻¹, highlighting ILHCE as a transformative electrolyte design toward real-world applications.