Lithium salt/amide-based deep eutectic electrolytes for lithium-ion batteries: electrochemical, thermal and...

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Deep eutectic solvents (DESs) are gaining attention as cost-effective alternatives to ionic liquids for electrochemical applications.
• Optimizing melting point and electrochemical stability is crucial for DESs in devices like lithium-ion batteries (LIBs).

Purpose of the Study:

• To investigate the thermal and electrochemical properties of Li-salt/amide-based electrolytes (DEEs) for LIB applications.
• To understand the correlation between molecular structure, coordination state, and electrochemical performance.

Main Methods:

• Molecular dynamics simulations were used to calculate the coordination state between lithium salts and amide components.
• Density functional theory (DFT) was employed to compute HOMO and LUMO levels for assessing electrochemical stability.
• Experimental cyclic voltammetry was performed to validate computational predictions.

Main Results:

• Hydrogen bonding donor (HBD)-free DEEs exhibited enhanced reduction stability compared to HBD-containing DEEs.
• The DEE composed of LiTFSI:1,1,3,3-tetramethylurea (1:5 mol%) demonstrated optimal melting point, electrochemical stability, and ionic conductivity.
• Computational methods accurately predicted experimental electrochemical stability.

Conclusions:

• DESs free of N-H bonds in amide components are promising for stable LIB electrolytes.
• The LiTFSI:1,1,3,3-tetramethylurea DEE is identified as a superior electrolyte candidate for LIBs.
• This research provides valuable insights for designing novel DES-based electrolytes.