Microstructural Engineering‐Driven Electrochemical Performance in Water‐in‐Salt Electrolytes

Abstract Water‐in‐salt electrolytes (WiSE) emerge as a promising strategy for aqueous zinc‐based batteries through effective hydrogen evolution suppression and significantly improved cycling reversibility. However, current research lacks an in‐depth understanding of the microstructure‐macroscopic performance correlation mechanism, particularly in terms of macroscopic‐scale simulations. This study presents a comprehensive investigation of the concentration‐dependent electrochemical regulation mechanism through integrated electrochemical testing, electrolyte characterization, and modeling. First, microstructural features fundamentally govern critical battery performance metrics such as cycling efficiency and polarization behavior. Then, through an innovatively designed open‐circuit potential difference experiment, the solvation energy parameters of the WiSE particles are successfully determined, while Raman spectroscopy analysis reveals the concentration‐dependent evolution of the Zn 2+ coordination environment and water molecule solvation structures. More importantly, a multiphysics‐coupled model incorporating dynamic solvation reactions and dissolution‐deposition processes is developed, which successfully reproduces the voltage response characteristics of zinc symmetric cells and resolves the spatiotemporal concentration distribution of electrolytes. This work not only deepens the understanding of the structure‐performance relationship in WiSE, but also establishes a multiscale research methodology and structure‐activity correlation model. This approach offers a new paradigm for resolving multiscale structure‐property relationships in concentrated systems such as ionic liquids, with strategic implications for advancing electrochemical energy storage systems.