Polyoxotungstate Featuring Zinc-Ion-Triggered Structural Transformation as An Efficient Electrolyte Additive for Aqueous Zinc-Ion Batteries

It is promising but still challenging for the widespread application of aqueous zinc batteries due to the poor reversibility of the zinc anode caused by prevalent dendrite growth and pronounced interfacial side reactions. Herein, we report a rare soluble and water-stable high-nuclearity {Nd₉Si₄W₃₉} polyoxotungstate. Interestingly, upon encountering Zn²⁺ ions, the discrete {Nd₉Si₄W₃₉} nanocluster undergoes a structural transformation to form an infinitely extended cluster-based {[Zn(H₂O)₄]₃[Nd₉Si₄W₃₉]₂} two-dimensional honeycomb layer, with which atomic-level Zn²⁺ ion effects in reconstructing the layer are determined. More interestingly, we demonstrate that the structural transformation property renders the {Nd₉Si₄W₃₉} cluster an efficient electrolyte additive for aqueous zinc batteries, enabling the formation of the 2D layer as a protective layer on the zinc anode, significantly enhancing the reversibility of the zinc anode. Compared to the pristine Zn//Zn symmetric battery, the Zn//Zn symmetric battery with the {Nd₉Si₄W₃₉} additive exhibits an extended lifespan of over 2000 hours at a current density of 1 mA cm^-2. In situ optical microscopy, Raman spectroscopy, and molecular dynamics simulations reveal that the formation of the protective layer effectively promotes uniform zinc deposition, and inhibits zinc agglomeration, dendrite growth, and side reactions, thereby enabling the zinc anode to exhibit high reversibility and long-term service life.