Electric double layer reconstruction via dielectric-response-driven dynamic adsorption enables ultralow-overpotential long-life Zn anodes

Aqueous Zn-metal batteries are promising for sustainable energy storage, but their practical performance is limited by high overpotentials that cause energy loss and trigger dendrite growth and parasitic side reactions. Achieving ultralow overpotential remains challenging due to the complex coupling between interfacial processes and Zn deposition behavior. Here, we introduce sodium 2-mercaptoethanesulfonate (MESNA) as an electrolyte additive, enabling reversible Zn plating/stripping over 5800 h at an ultralow overpotential of 30 mV at 1 mA cm⁻²/1 mAh cm⁻². To elucidate the function of MESNA, we draw upon classical electrodeposition kinetics theory and decompose overpotential regulation into ion migration, desolvation, and nucleation. By combining electrochemical analysis with in situ electric double layer characterization, we reveal that MESNA reconstructs the electric double layer via dynamic interfacial adsorption driven by its dielectric response. This facilitates ion migration and desolvation, effectively reducing the deposition overpotential. Consequently, large-area Zn||Zn symmetric pouch cells (5 × 10 cm²) achieve a 5400-h cycle life with low overpotential. Notably, stable operation of these pouch cells exceeds 600 h at 100 mA, with a Zn plating/stripping capacity of 1000 mAh per half-cycle. These findings provide mechanistic insights into ultralow-overpotential Zn electrodeposition and highlight overpotential modulation as an effective paradigm for designing high-performance zinc batteries.