Paschen-Back Effect-Driven Coordination Modulation of SO₄²⁻ Hydration for Dendrite-Free Zn Ion Batteries via Magnetized Electrolyte

Abstract Tuning the anionic solvation structure and dynamic processes at solid‒liquid interfaces are critical yet challenging for stabilizing Zn metal anodes in Zn ion batteries. Here, we demonstrate that highly hydrated SO₄²⁻ can be modulated under a strong magnetic field (MF) via the Paschen-Back effect on the O-H stretching mode, which reorients individual water molecules to manipulate Zn²⁺ solvation and protonated water clusters (H₃O⁺). This high level of hydration was confirmed through Raman spectroscopy, molecular dynamics (MD) simulations, and ¹⁷O/¹H nuclear magnetic resonance (NMR) with coaxial insert tubes. Our findings reveal that the MF disrupts the hydrogen-bonded water structure (DDAA), leading to charge redistribution and localization onto the SO₄²⁻ -4H₂O (DDA) complex, inhibiting the intra-molecular Fermi resonance of free O-H stretch water (DAA-OH) and suppressing the Zn²⁺-6H₂O interaction. Additionally, MD simulations and electrochemical characterizations show that these hydrated SO₄²⁻-H₂O complexes favor Zn²⁺ nucleation and deposition on the (002) plane, with the preferential adsorption of oxygen on Zn (002) inhibiting 2D Zn²⁺ diffusion. Combined with density functional theory (DFT) analysis, we demonstrate that magnetically treated ZnSO₄ electrolytes exposed to a 3 T MF for 25 minutes can disrupt the Grotthuss proton-transport mechanism, suppressing H₂ evolution and achieving 100% dendrite-free growth. This work highlights the critical role of magnetization pretreatment in enhancing the stability of electrochemical interfaces, offering insights for the molecular design of interfacial water in various aqueous Zn-based batteries.