SEI chemistry enlightened by liquid Madelung potential analysis and MLFF-MD simulation

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Lithium metal batteries (LMBs) offer high energy density but suffer from lithium metal's reactivity, causing electrolyte decomposition.
• The solid electrolyte interphase (SEI) is crucial for stabilizing the Li metal surface, but its formation is not fully understood.
• Controlling SEI properties is key to overcoming LMB limitations.

Purpose of the Study:

• To investigate how electrolyte composition, specifically anion species, influences SEI formation on lithium metal.
• To elucidate the mechanisms governing SEI chemistry and its impact on interfacial stability.
• To provide a computational framework for designing stable electrolytes for LMBs.

Main Methods:

• Electrode potential analyses using liquid Madelung potential calculations to assess Li+ stabilization.
• Machine-learning force field molecular dynamics (MLFF-MD) simulations to resolve interfacial decomposition reactions.
• Systematic investigation across electrolytes with varying anion species and concentrations.

Main Results:

• Highly delocalized anions in concentrated electrolytes weaken Li+ coordination, shifting the Li/Li+ redox potential positively.
• This shift reduces the kinetic barrier for SEI formation.
• These anions preferentially reduce at the lithium metal surface, forming dense, inorganic-rich SEI layers.

Conclusions:

• Electrolyte anion design significantly impacts SEI properties and lithium metal stability.
• A computational approach combining Madelung potential and MLFF-MD simulations offers insights into SEI formation.
• This framework enables rational design of electrolytes for enhanced lithium metal battery performance and safety.