Enhanced Ionic Conductivity at the Solid Electrolyte Interphase of Oxygen-Doped Li₆PS₅Cl

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• The solid electrolyte interphase (SEI) at the Li metal | solid-state electrolyte (SSE) interface is critical for all-solid-state battery performance.
• This buried interphase significantly impacts interfacial resistance but is difficult to study experimentally.

Purpose of the Study:

• To investigate the formation and transport properties of SEI at the Li$_{6}$PS$_{5-x}$ClO$_{x}$ | Li interface.
• To elucidate the role of oxygen doping on SEI composition and properties.

Main Methods:

• Utilized machine-learned interatomic potential molecular dynamics (MLIP-MD) simulations.
• Employed a machine-learning phase identification framework to analyze SEI structures.
• Simulated interfaces with varying levels of oxygen doping.

Main Results:

• Identified the dominant SEI phase as Li$_{2}$S$_{1-x-y}$P$_{0.5x}$Cl$_{0.5x}$O$_{y}$, an anion-substituted Li$_{2}$S structure.
• Found that moderate oxygen doping enhances SEI ionic conductivity.
• Observed that excessive oxygen doping reduces bulk electrolyte conductivity and SEI stability.

Conclusions:

• The study provides an atomistic understanding of SEI formation and the impact of oxygen doping.
• A trade-off exists between enhanced ionic conductivity and reduced stability with increased oxygen content.
• This explains the non-monotonic relationship between oxygen content and interfacial performance in experiments.