  Lithium based deep eutectic solvents (DESs) are excellent candidates for
eco-friendly electrolytes in lithium ion batteries. While some of these DES
have shown promising results, a clear mechanism of lithium ion transport in
DESs is not yet established. This work reports the study on the solvation and
transport of lithium in a DES made from lithium perchlorate and acetamide using
Molecular Dynamics (MD) simulation and neutron scattering techniques. Based on
hydrogen bonding (H-bonding) of acetamide with neighbouring molecules/ions, two
states are largely prevalent: 1) acetamide molecules which are H-bonded to
lithium ions (~ 36 %) and 2) acetamide molecules that are entirely free (~
58%). Analysing their stochastic dynamics independently, it is observed that
the long-range diffusion of the former is significantly slower than the latter
one. This is also validated from the neutron scattering experiment on the same
DES system. Further, the analysis the lithium dynamics shows that the diffusion
of acetamide molecules in the first category is strongly coupled to that of
lithium ions. On an average the lithium ions are H-bonded to ~ 3.2 acetamide
molecules in their first solvation. These observations are further bolstered
through the analysis of the H-bond correlation function between acetamide and
lithium ions, which show that ~ 90% of lithium ionic transport is achieved by
vehicular motion where the ions diffuse along with its first solvation shell.
The findings of this work are an important advancement in understanding
solvation and transport of lithium ion in DES.
