Structural Transformations within the Solvate Ionic Liquid [Li(Triglyme)][NTf₂]: Implications for Self-Diffusion,...

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Solvate ionic liquids (SILs) are emerging electrolytes for advanced lithium-ion batteries.
• Equimolar mixtures of lithium bis(trifluoromethanesulfonyl)imide ([Li][NTf2]) and triglyme (G3) are of particular interest due to potential ionic liquid-like behavior.
• The formation of stable [Li]+-glyme complexes is hypothesized to govern their properties.

Purpose of the Study:

• To investigate the structure and dynamics of [Li][NTf2]:G3 mixtures using molecular dynamics simulations.
• To characterize the coordination patterns of [Li]+ cations across various compositions and temperatures.
• To understand the impact of structural changes on the transport properties of these potential battery electrolytes.

Main Methods:

• Multimicrosecond molecular dynamics (MD) simulations were employed.
• Simulations covered a range of mixing ratios and temperatures.
• Analysis focused on cation coordination, complex formation, and transport properties (diffusion, viscosity).

Main Results:

• The structure of [Li][NTf2]:G3 mixtures is primarily dependent on composition and remarkably temperature-insensitive.
• [Li]+ cations exhibit varying coordination with G3 molecules and counterions ([NTf2]-) based on concentration.
• Increasing [Li][NTf2] content leads to decreased self-diffusion coefficients and increased viscosity.
• Stable 1:1 [Li]+-G3 complexes form at specific mole fractions, evidenced by concerted movement.

Conclusions:

• [Li][NTf2]:G3 mixtures exhibit high temperature stability, retaining SIL-like features above 200 °C.
• Composition-driven structural changes significantly influence electrolyte transport properties.
• These findings highlight the potential of these highly temperature-stable SILs for next-generation battery technologies.