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, (NH 4 ) 3 [PMo 12 O 40 ], which contains the zincophilic‐hydrophobic polyoxoanion [PMo 12 O 40 ] 3− and the zincophobic‐hydrophilic cation NH 4 + , a promising electrolyte system is developed. Experimental and theoretical analyses unravel that [PMo 12 O 40 ] 3− , consisting of a weak hydrophilic [Mo 12 O 36 ] shell encapsulating a zincophilic intensifier PO 4 3− core, can alter the Zn 2+ ‐solvation sheath and Zn‐electrolyte interface. Meanwhile, NH 4 + 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//NaV 3 O 8 ∙1.5H 2 O batteries with (NH 4 ) 3 [PMo 12 O 40 ] 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.