Molten mixtures of lithium chloride and metallic lithium (LiCl-Li) play an essential role in the electrolytic reduction of various metal oxides. These mixtures possess unique high temperature physical and chemical properties that have been researched for decades. However, due to their extreme chemical reactivity, no study to date has been capable of definitively proving the basic physical nature of Li dissolution in molten LiCl. In this study, the evolution of structures of the molten LiCl-Li, as metallic Li is electrochemically introduced into the melt, is investigated in situ using synchrotron radiation based high energy wide angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). The scattering results indicate the presence of Cl^- ion “cages” with size of approximately 7.9Å, which suggests the formation of Li nanoclusters as previous reported. The structure factor of the melt derived from the SAXS results is in agreement with that obtained from ab-initio molecular dynamics (AIMD) simulation of lithium nanoclusters (Li₄, Li₆ and Li₈) in LiCl. A physical model based on the formation and suspension of metallic Li nanocluster in lithium chloride is proposed to explain various phenomena exhibited by these solutions that were previously unexplainable.

The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. http://energy.gov/downloads/doe-public-access-plan