Soft X-ray Emission Studies on Hydrate-Melt Electrolytes

Highly salt-concentrated aqueous solutions are a new class of electrolytes, which provide a wide potential window exceeding 3 V and, hence, realize possibly inexpensive, safe, and high-energy-density storage devices. Herein, we investigate the evolution of the coordination structure and electronic state depending on the salt concentration through soft X-ray emission spectroscopy and first-principles molecular dynamics calculations. Close to the concentration limit, categorized as a hydrate melt, a long-range hydrogen-bond network of water molecules disappears with emerging localized electronic states that resemble those in the gas phase. Such localized electronic states are attributed not only to their geometrically isolated nature but also to their dominant electrostatic interaction with Li+ cations. Therefore, the electrical properties of water in the hydrate melt can be more gaslike than liquidlike.

Automated summary

This study investigates the electrolyte properties of highly salt-concentrated aqueous solutions, revealing that the structure and electronic states of water molecules in hydrate melts evolve with salt concentration, exhibiting electrical properties more similar to gas phase rather than liquid phase.