First-Principles Study on a Layered Antiperovskite Li₇O₂Br₃ Solid Electrolyte.

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lithium-rich antiperovskites (LiRAPs) are emerging as promising solid electrolytes for solid-state lithium-ion batteries (SSLIBs).
• Layered Li7O2Br3 shows potential for higher Li+ conductivity than cubic Li3OBr, but pure phase synthesis and properties remain uninvestigated.
• SSLIBs offer enhanced safety and energy density compared to conventional lithium-ion batteries.

Purpose of the Study:

• To investigate the physical and electrochemical properties of Li7O2Br3 using density functional theory (DFT).
• To assess the stability, ion conductivity, and processability of Li7O2Br3.
• To explore synthesis conditions and the impact of defects on Li+ diffusion in Li7O2Br3.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model Li7O2Br3.
• Calculations included dynamic stability, bandgap, malleability, Li+ migration barriers, and defect effects.
• A pressure-temperature-Gibbs (PTG) phase diagram was constructed to predict synthesis conditions.

Main Results:

• Li7O2Br3 is dynamically stable with a wide bandgap (5.83 eV), indicating electrical insulation.
• Li7O2Br3 exhibits improved malleability over Li3OBr, beneficial for material processing.
• The Li+ migration barrier in Li7O2Br3 (0.26 eV) is lower than in Li3OBr (0.4 eV), attributed to softened edge-layer Li phonons.
• LiBr defects significantly enhance Li+ mobility.
• A PTG phase diagram was generated to guide experimental synthesis.

Conclusions:

• Li7O2Br3 is a dynamically stable material with promising properties for solid electrolytes.
• Its lower Li+ migration barrier and improved malleability make it a strong candidate for SSLIBs.
• Understanding defect effects and synthesis conditions is crucial for realizing its potential in advanced battery technologies.