Deciphering multi-dimensional interfacial mechanisms via organic cosolvent engineering for sustainable zinc metal batteries

Introducing organic cosolvent is a common and cost-effective electrolyte engineering for aqueous Zn-battery, reshaping the solvation environment of electrolyte and modulating the interfacial electrochemistry on Zn-metal electrode. Clarifying the mechanisms governing interfacial dynamic evolution and electrochemical performance is essential for guiding cosolvent selection. However, the absence of direct visualization for dynamic interfacial evolution during Zn plating/stripping has impeded mechanistic understanding of cosolvent-mediated effects in electrolyte engineering. Here, we combine advanced in-situ spectroscopy with theoretical calculation to decouple the interfacial evolution at the molecular level. We find that cosolvents not only weaken the connectivity of the interfacial hydrogen-bond network between water molecules, thereby hindering the H+ transfer, but also accelerate the interfacial dynamic transition of Zn2+-(de)solvation from transient to steady state. Additionally, we observe a dynamic adsorption substitution between cosolvent and water, which weakens the electric field intensity exerted on interfacial water. Furthermore, we demonstrate that cosolvents can modify the components content and distribution of the passivation-layer via indirect regulation pathway, rather than a typical self-decomposition mechanism. These multidimensional insights bridge the knowledge gap in cosolvent functionality, offering rational principles for tailoring solvation structures and interfacial dynamics in next-generation aqueous batteries.