Li₅Sn, the Most Lithium-Rich Binary Stannide: A Combined Experimental and Computational Study

Area of Science:

• Materials Science
• Solid-State Chemistry
• Computational Materials Science

Background:

• Lithium-tin (Li5Sn) intermetallic compounds are crucial in battery technology.
• Previous studies predicted Li5Sn crystal structures using electronic calculations, but experimental validation was limited.

Purpose of the Study:

• To experimentally determine the crystal structure of Li5Sn.
• To computationally investigate the thermodynamic stability of different Li5Sn structures.
• To reconcile experimental observations with theoretical predictions.

Main Methods:

• Single-crystal X-ray diffraction was used to solve the crystal structure of experimentally synthesized Li5Sn.
• Extensive ab initio calculations, including thermodynamic integration with Langevin dynamics and machine-learning potentials, were performed.
• A structure enumeration algorithm was employed to systematically derive and evaluate potential Li5Sn structures.

Main Results:

• A well-crystallized orthorhombic Li5Sn structure (space group Cmcm) was isolated and characterized.
• Computational analysis identified a new, energetically most stable Li5Sn structure with space group Immm at 0 K.
• The Immm structure was found to be thermodynamically more stable than the Cmcm structure at finite temperatures.

Conclusions:

• The experimentally observed Cmcm Li5Sn structure is likely favored due to kinetic factors, not thermodynamic stability.
• Computational methods, including machine learning potentials, are powerful tools for predicting stable material structures.
• This study provides critical insights into the phase stability of lithium-tin compounds for potential energy storage applications.