In situ Detection of the Molecule-Crowded Aqueous Electrode–Electrolyte Interface

Electrode–electrolyte interface plays a crucial role in determining the stability and behavior of electrochemical electrodes. Although X-ray photoelectron spectroscopy has been established as a powerful analytical technique for interface chemistry, the necessity for ultrahigh vacuum remains a significant obstacle to directly detecting dynamic interfacial evolution, particularly in aqueous environments. Here, we employ tender-energy ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to bridge the gap between ultrahigh vacuum and near-atmospheric pressure, enabling an in-depth investigation of the molecule-crowded aqueous interface evolution in a Zn metal anode. The results demonstrate that the persistent presence of additive molecules effectively inhibits direct contact between reactive Zn and H₂O, while also facilitating uniform Zn deposition. In situ optical microscopy observations and synchrotron radiation X-ray diffraction further verified the uniform and dense Zn deposition, attributed to lateral growth induced by the (002) crystal facet evolution. As proof of its effectiveness, batteries incorporating the Zn//Zn, Zn//Cu, and full cell with the additive demonstrate significantly improved stability and reversibility. This finding opens up new avenues for exploration of interfacial chemistry at the molecule level, offering insights into the design of highly stable metal anodes of aqueous ion batteries for practical applications.