Li_3.6In₇S_11.8Cl: an air- and moisture-stable superionic conductor

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• All-solid-state batteries (ASSBs) are advanced energy storage solutions.
• Sulfide solid electrolytes offer high ionic conductivity but suffer from moisture sensitivity and H₂S release.
• Developing stable solid electrolytes is crucial for safe and high-performance ASSBs.

Purpose of the Study:

• To synthesize and characterize a novel, moisture-stable superionic conductor for ASSBs.
• To investigate the ionic conductivity and structural properties of Li₃.₆In₇S₁₁.₈Cl.
• To evaluate its potential as a safe electrolyte for next-generation batteries.

Main Methods:

• Synthesis of Li₃.₆In₇S₁₁.₈Cl.
• Ionic conductivity measurements at 25 °C and after humid air exposure.
• Multimodal investigations including structural analysis.
• Ab initio molecular dynamics simulations.
• ⁶Li NMR and relaxometry.

Main Results:

• Li₃.₆In₇S₁₁.₈Cl exhibits high structural stability in humid air.
• Achieved ionic conductivity of 1.1 mS cm⁻¹ at 25 °C, increasing to 4.2 mS cm⁻¹ post-humid exposure.
• Water presence within the pellet was found to facilitate ion conduction reversibly.
• Identified 3D isotropic Li⁺ diffusion pathways and active Li⁺ sites (Wyckoff 16c and 8a).

Conclusions:

• Li₃.₆In₇S₁₁.₈Cl is a promising superionic conductor with superior moisture stability.
• Its high ionic conductivity and stable cycling performance make it suitable for ASSBs.
• This material addresses safety concerns associated with traditional sulfide electrolytes.