Structure-property relationships in lithium superionic conductors having a Li10GeP2S12-type structure

Area of Science:

• Solid-state chemistry
• Materials science
• Crystallography

Background:

• Superionic conductors are crucial for advanced energy storage applications.
• Lithium-ion conductivity in materials like Li10GeP2S12 (LGPS) is of significant interest.
• Understanding ion diffusion mechanisms is key to optimizing battery performance.

Purpose of the Study:

• To determine the crystal structures of Li9.81Sn0.81P2.19S12 and Li10.35Si1.35P1.65S12.
• To investigate the lithium ion distribution and diffusion pathways in these LGPS-type materials.
• To compare the ionic conduction mechanisms across different LGPS-type phases (Si, Ge, Sn).

Main Methods:

• Neutron diffraction analysis over a wide temperature range (12-800 K).
• Maximum entropy method to clarify lithium distribution.
• Analysis of structural parameter changes.

Main Results:

• The crystal structures of the studied Sn and Si compounds, both with LGPS-type structures, were determined.
• The Sn system demonstrated one-dimensional lithium diffusion along the c-direction.
• In contrast to the typically observed three-dimensional diffusion in Ge-based LGPS, the Sn system showed restricted diffusion pathways.

Conclusions:

• The study reveals distinct ionic conduction mechanisms in LGPS-type materials based on the central element (Si, Ge, Sn).
• The Sn-based material exhibits anisotropic, one-dimensional lithium diffusion.
• Structural variations significantly influence the ionic transport properties, impacting potential battery applications.