Heat capacities and an updated thermodynamic model for the Li-Sn system

Area of Science:

• Materials Science
• Thermodynamics
• Electrochemistry

Background:

• Accurate thermodynamic data is crucial for optimizing lithium-ion battery performance.
• Existing thermodynamic models for the lithium-tin system require refinement.

Purpose of the Study:

• Synthesize phase-pure Li17Sn4 and Li7Sn3 intermetallic compounds.
• Measure their heat capacities to develop improved thermodynamic models.
• Enhance the thermodynamic description of the Li-Sn system for better predictive capabilities.

Main Methods:

• Synthesis of intermetallic compounds using controlled heat treatment in tantalum crucibles.
• Characterization via inductively coupled plasma optical emission spectroscopy (ICP-OES) and powder X-ray diffraction (powder-XRD).
• Heat capacity measurements using the step method with a Setaram C80 Tian-Calvet calorimeter.

Main Results:

• Successful synthesis and characterization of phase-pure Li17Sn4 and Li7Sn3.
• Experimentally determined heat capacity data for these compounds.
• Development of restricted Maier-Kelley models and re-optimization of the Li-Sn thermodynamic system.
• Improved agreement between calculated and experimental data for heat capacity, thermodynamics, electrochemistry, and phase diagrams.

Conclusions:

• The re-optimized thermodynamic models provide a more accurate representation of the Li-Sn system.
• These models, based on reliable heat capacity data, can predict electromotive force (emf) values.
• The findings support the development of advanced lithium-ion battery technologies with improved performance predictions.