Anomalously High Ionic Conductivity of Li₂SiS₃-Type Conductors

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Development of safer, high-energy solid-state batteries requires electrolytes with high room-temperature ionic conductivity.
• The scarcity of known crystal structures for superionic conductors limits battery material innovation.

Purpose of the Study:

• To report a novel lithium superionic conductor with enhanced ionic conductivity.
• To investigate a new three-dimensional framework structure for solid-state electrolytes.

Main Methods:

• Synthesis and characterization of Li2SiS3 with tetragonal crystal symmetry.
• Measurement of ionic conductivity at room temperature (298 K).
• Crystallographic analysis to determine the novel framework structure.

Main Results:

• A new tetragonal crystal structure of Li2SiS3 was identified, featuring isolated edge-sharing tetrahedral dimers.
• This novel conductor exhibits a high ionic conductivity of 2.4 mS cm⁻¹ at 298 K.
• The conductivity is three orders of magnitude higher than its orthorhombic polymorph.

Conclusions:

• The newly discovered Li2SiS3 is a promising lithium superionic conductor.
• Its silicon-based framework, derived from abundant resources, offers potential for scalable solid-state electrolyte development.
• Further optimization could lead to next-generation solid-state batteries.