Contextual Solvation Control for Nonlinear Kinetic Optimization in Dual-Cosolvent Electrolytes for Aqueous Zinc Metal Batteries

Cosolvent engineering for aqueous Zn metal batteries has traditionally emphasized thermodynamic stabilization, whereas the kinetic dimension of Zn²⁺ charge transfer—particularly in multi-cosolvent systems—remains far less understood. Here, we uncover a contextual solvation control mechanism in a dual-cosolvent electrolyte pairing a strong cosolvent (dimethyl sulfoxide, DMSO) with a weak cosolvent (dimethyl carbonate, DMC). Mechanistically, the outer-shell weak cosolvent imposes mild yet favorable interactions that modulate Zn–ligand binding and facilitate solvent exchange, while simultaneously promoting the formation of a thin, well-regulated SEI that accelerates interfacial charge transfer kinetics. This contextual regulation preserves thermodynamic stability while, more importantly, enabling a nonlinear kinetic optimization that emerges exclusively at specific strong-to-weak cosolvent ratios. Using a multi-descriptor kinetic framework, we show that the dual-cosolvent regime lowers the reorganization energy and charge-transfer barrier by ~ 40% relative to single-cosolvent systems. As a result, the electrolyte supports stable Zn plating/stripping for over 2000 hours with suppressed dendrite formation. Full cells paired with vanadium-based cathodes further exhibit enhanced capacity retention, long-term cycling stability, and markedly improved rate performance.