Tailoring Zn 2+ Solvation for Dendrite‐Free and High‐Efficiency Aqueous Zinc Batteries

ABSTRACT Aqueous zinc‐metal batteries (ZMBs) offer high capacity, intrinsic safety, and low cost but remain challenged by dendrite growth, hydrogen evolution, and interfacial instability. Here, we develop a solvation‐engineered hybrid electrolyte comprising 3 M Zn(OTf) 2 in water, methanol, and dimethyl sulfoxide (3:1:1, v/v/v). Methanol disrupts the hydrogen‐bond network, while DMSO stabilizes Zn 2+ coordination, collectively forming a unique solvation structure as confirmed by isothermal titration calorimetry, density functional theory, and Raman spectroscopy. This environment promotes preferential triflate anion decomposition, yielding an in situ fluorine‐rich solid electrolyte interphase (SEI) that passivates zinc, reduces water activity, and suppresses hydrogen evolution. As a result, Zn||Zn cells cycle stably for over 4000 h at 0.5 mA cm −2 , Zn||Cu cells achieve 99.8% coulombic efficiency over 2000 cycles, and Zn||MnO 2 cells deliver > 150 mAh g −1 at 1C with sustained cathode stability. This work demonstrates a simple, scalable solvation‐engineering strategy that stabilizes zinc interfaces without complex additives or highly concentrated electrolytes, advancing the practical deployment of aqueous ZMBs.