ReaxFF molecular dynamics simulations on lithiated sulfur cathode materials.

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Sulfur is a promising cathode material for rechargeable energy storage.
• Sulfur cathodes experience volume variations and mechanical stress during cycling.
• Mechanical properties of lithiated sulfur compounds are not well understood.

Purpose of the Study:

• To develop a ReaxFF interatomic potential for Li-S interactions.
• To investigate the structural, mechanical, and kinetic behavior of amorphous lithiated sulfur (a-LixS) using molecular dynamics (MD) simulations.
• To understand the effect of lithiation on the mechanical properties of sulfur cathodes.

Main Methods:

• Developed a ReaxFF interatomic potential for Li-S interactions.
• Performed molecular dynamics (MD) simulations on a-LixS compounds.
• Calculated diffusion coefficients for lithium and sulfur.
• Used grand canonical Monte Carlo (GCMC) for open circuit voltage profile.
• Constructed the Li-S binary phase diagram using genetic algorithm tools.

Main Results:

• Increasing lithium content improves the strength of a-LixS compounds, but not linearly.
• Computed diffusion coefficients for Li and S at various lithiation stages.
• Calculated the open circuit voltage profile during cell discharge.
• Generated the Li-S binary phase diagram.

Conclusions:

• Simulation results provide crucial insights into the behavior of sulfur-based cathode materials.
• Understanding mechanical properties is essential for developing improved lithium-sulfur batteries.
• The developed ReaxFF potential and simulation methods aid in designing advanced energy storage solutions.