Additive effect on reductive decomposition and binding of carbonate-based solvent toward solid electrolyte interphase...

Area of Science:

• Electrochemistry
• Materials Science

Background:

• The solid-electrolyte interphase (SEI) is critical for lithium-ion battery (LIB) stability and performance.
• SEI formation involves the reductive decomposition of electrolyte solvent molecules.

Purpose of the Study:

• To investigate the effects of vinylene carbonate (VC) additive on ethylene carbonate (EC) solvent decomposition in LIB electrolytes.
• To elucidate the thermodynamic and kinetic mechanisms of SEI formation with and without VC.

Main Methods:

• Density functional theory (DFT)-based molecular dynamics with explicit solvent.
• Blue-moon ensemble technique for free energy calculations.
• Analysis of one-electron (1e) and two-electron (2e) reduction pathways, and anion radical attacks.

Main Results:

• The study accurately reproduced experimentally observed gaseous SEI products.
• A novel mechanism was identified where VC preferentially reacts with EC anion radicals, suppressing EC's 2e reduction.
• This VC-mediated pathway enhances initial SEI formation and is consistent with reduced irreversible capacity.

Conclusions:

• Vinylene carbonate plays a primary role in modifying ethylene carbonate decomposition pathways.
• The findings challenge the conventional view of VC's sacrificial reduction, proposing a new mechanism for improved SEI formation.
• The proposed mechanism explains reduced irreversible capacity, offering insights into enhanced LIB performance.