Structural Investigations on Lithium-Doped Protic and Aprotic Ionic Liquids.

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Ionic liquids (ILs) are promising electrolytes for lithium-ion batteries.
• Lithium bis(trifluoromethanesulfonyl)imide (LiNTf2) is a common lithium salt used in IL electrolytes.
• Understanding ion solvation is key to optimizing electrolyte performance.

Purpose of the Study:

• To investigate the solvation of Li+ ions in various [NTf2]--based ionic liquids.
• To evaluate the impact of cation structure on Li+ solvation and mobility.
• To compare Li+ solvation in protic and aprotic ionic liquids.

Main Methods:

• Molecular dynamics (MD) simulations (classical and ab initio).
• Systematic variation of ionic liquid cation structures (ring size, alkyl chain, acidic proton absence).
• Analysis of Li+ coordination numbers, mobility, and autocorrelation functions.

Main Results:

• Ionic liquids largely maintain their structure upon LiNTf2 addition.
• Slightly higher Li+ coordination numbers observed in aprotic ILs compared to protic ones.
• Rattling motion of Li+ cations within [NTf2]--based cages was analyzed.

Conclusions:

• The solvation mechanism of Li+ in ILs is detailed, influenced by cation structure and hydrogen bonding.
• MD simulations provide insights into Li+ ion transport in IL electrolytes.
• Findings contribute to the design of improved electrolytes for lithium-ion batteries.