Aluminum based sulfide solid lithium ionic conductors for all solid state batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Lithium ionic conductors are crucial for next-generation energy storage devices.
• Organic liquid electrolytes pose safety and stability challenges.
• Developing high-performance solid-state electrolytes is a key research objective.

Purpose of the Study:

• To synthesize novel lithium ionic conductors based on the Li2S-Al2S3-GeS-P2S5 system.
• To investigate the effect of aluminum to germanium ratios on ionic conductivity.
• To evaluate the electrochemical properties and stability of the synthesized materials.

Main Methods:

• Synthesis via mechanical milling and single-step heat treatment at 550 °C.
• Characterization of crystalline powders.
• Measurement of ionic conductivity at room temperature and elevated temperatures.
• Electrochemical stability analysis using cyclic voltammetry.

Main Results:

• Achieved high lithium ionic conductivity (1.7 × 10⁻³ S cm⁻¹ at 25 °C, ~6 × 10⁻³ S cm⁻¹ at 100 °C) with an optimal Al:Ge ratio of 30:70.
• Obtained a low activation energy (Ea = 17 kJ mol⁻¹), superior to other solid electrolytes.
• Demonstrated excellent electrochemical stability within a wide voltage window (-0.3 to 5.0 V) with reversible lithium deposition/stripping peaks.

Conclusions:

• The Li2S-Al2S3-GeS-P2S5 system yields highly conductive and stable crystalline lithium ionic conductors.
• These materials show promise as alternatives to liquid electrolytes in electrochemical applications.
• The optimized composition offers a significant advancement in solid-state electrolyte technology.