Maximizing Functional Diversity of Electrolyte Additives through Modular Molecular Engineering to Stabilize Zinc Metal Anodes

Abstract

Molecule design is significant for achieving the functional diversity of electrolyte additives in aqueous zinc-ion batteries, yet the strategy is underutilized. Here modular molecular engineering is proposed to segregate and recombine hydrophilic (hydrophobic) and zincophobic (zincophilic) modules within electrolyte additives to maximize the efficacy of electrolytes in promoting Zn stability and reversibility. By using an electrolyte with a polyoxometalate (POM) additive, (NH₄)₃[PMo₁₂O₄₀], which contains the zincophilic-hydrophobic polyoxoanion [PMo₁₂O₄₀]³⁻ and the zincophobic-hydrophilic cation NH₄⁺, a promising electrolyte system is developed. Experimental and theoretical analyses unravel that [PMo₁₂O₄₀]³⁻, consisting of a weak hydrophilic [Mo₁₂O₃₆] shell encapsulating a zincophilic intensifier PO₄³⁻ core, can alter the Zn²⁺-solvation sheath and Zn-electrolyte interface. Meanwhile, NH₄⁺ disrupts hydrogen bond networks of water, synergistically realizing high electrochemical stability of the electrolyte and Zn anode at both room and low temperatures. As a result, Zn//NaV₃O₈∙1.5H₂O batteries with (NH₄)₃[PMo₁₂O₄₀] additive exhibit outstanding cycling stability, achieving over 10 000 cycles at 5 A g⁻¹ at 25 °C and 800 cycles at 0.2 A g⁻¹ at −30 °C. This work highlights the significance and promising of molecule design for electrolyte additives and expands the research scope of POM chemistry.