Oligomerization of lithium ions in water-in-salt electrolytes

26 October 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Water-in-salts (WiS) have recently emerged as promising electrolytes for energy storage applications, ranging from aqueous batteries to supercapacitors. Here, ab initio molecular dynamics is used to study the structure of a 21 m LiTFSI WiS. The simulation reveals a new feature, in which the lithium ions form oligomer-like nanochains that involve up to 10 ions. Despite the strong Coulombic interaction between them, the ions in the chains are found at a distance of 2.5 Angstroms. They display a drastically different solvation shell compared to the isolated ions, in which they share on average two water molecules. The nanochains have a highly transient character due to the low free energy barrier for forming/breaking them. Providing new insights into the nanostructure of WiS electrolytes, our work calls for re-evaluating our current knowledge of highly concentrated electrolytes and the impact of the modification of solvation of active species on their electrochemical performances.


highly concentrated electrolytes
ab initio molecular dynamics
lithium ions

Supplementary materials

Supplementary Information
Supplementary figures showing additional details on the structural properties of the system, validation with experiments, and comparison with the literature.


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