Tunable ion conductivity via terahertz-modulated interfacial monolayer water on metal surfaces.

Monolayer water (MW) on metal electrode surfaces commonly functions as a physical barrier that hinders the approach of molecules and ions onto the metal surface, thereby markedly diminishing interfacial ionic conductivity in aqueous ion batteries. This so-called "water poisoning" phenomenon is particularly pronounced in aqueous zinc-ion batteries, due to the larger hydrated radius of zinc ions compared to lithium or sodium ions. Using molecular dynamics simulations, we demonstrate that frequency-specific terahertz stimulation (TS) can disrupt the hydrogen-bond networks of interfacial MW through resonance mechanism, facilitating zinc ions transport onto the platinum electrode surface and boosting the ionic conductivity by up to 17-fold, as calculated from the Nernst-Einstein equation. Interestingly, the conductivity can rapidly drop to the initial level within hundreds of nanoseconds after the TS removal, indicating a reversible response. These findings offer molecular-level insights into the role of TS strategy in governing aqueous ion battery performance, while elucidating the frequency-selective regulation of confined interfacial water and suggesting broader implications for transport phenomena in nanoconfined environments, where interfacial water structure critically governs fluid mobility and solute transport dynamics.