Role of Inorganic Surface Layer on Solid Electrolyte Interphase Evolution at Li-Metal Anodes.

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Lithium metal anodes are crucial for high-energy rechargeable batteries.
• Solid electrolyte interphase (SEI) layers form on lithium metal, hindering ion transport.
• Existing models often overlook the impact of pre-existing passivation layers on SEI formation.

Purpose of the Study:

• To investigate the influence of nanometric Li2O, LiOH, and Li2CO3 passivation layers on lithium metal interfacial reactivity.
• To understand how these layers modify the decomposition of electrolytes and the subsequent SEI evolution.
• To correlate computational predictions with experimental observations of SEI formation.

Main Methods:

• Ab initio molecular dynamics (AIMD) calculations to simulate interfacial processes.
• X-ray photoelectron spectroscopy (XPS) measurements to analyze surface composition and SEI products.
• Analysis of electronic charge transfer and electrolyte decomposition pathways.

Main Results:

• Passivation layers (Li2O, LiOH, Li2CO3) reduce electronic charge transfer to the electrolyte, compared to pristine lithium metal.
• These layers alter the redox-based decomposition of bis(trifluoromethanesulfonyl)imide anions.
• Li2O-rich surfaces promote LiF formation, while LiOH-rich surfaces enhance sulfur decomposition.

Conclusions:

• Pre-existing inorganic passivation layers on lithium metal anodes play a critical role in SEI formation.
• The chemical nature of these passivation layers dictates the extent of electrolyte decomposition and SEI composition.
• Understanding these interfacial effects is key to designing stable and efficient lithium metal batteries.