Mechanochemical Synthesis and Characterization of Metastable Hexagonal Li₄SnS₄ Solid Electrolyte

Area of Science:

• Solid-state chemistry
• Materials science
• Electrochemistry

Background:

• Development of advanced solid electrolytes is crucial for safer and more efficient lithium-ion batteries.
• Existing materials often face challenges with conductivity, stability, or scalability.

Purpose of the Study:

• To synthesize and characterize a novel crystalline lithium-ion conducting material, Li4SnS4.
• To evaluate the structural, electrical, and chemical properties of the synthesized material.

Main Methods:

• Mechanochemical synthesis followed by heat treatment.
• Synchrotron X-ray powder diffraction for crystal structure analysis.
• Ionic conductivity and activation energy measurements at room temperature.

Main Results:

• A new crystalline phase of Li4SnS4 with hexagonal symmetry (space group P63/mmc) was successfully prepared.
• Fractional occupation of tetrahedral sites by Li and Sn ions was observed.
• An ionic conductivity of 1.1 × 10^-4 S cm^-1 at room temperature and a conduction activation energy of 32 kJ mol^-1 were achieved.
• The material demonstrated superior chemical stability in air compared to Li3PS4 glass-ceramic.

Conclusions:

• Li4SnS4 is a promising crystalline solid electrolyte with good ionic conductivity and air stability.
• The unique crystal structure and ion site occupancy contribute to its conductive properties.
• Further optimization could lead to its application in next-generation lithium-ion batteries.