Crystal Structure Influences Migration along Li and Mg Surfaces

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Dendrite formation on lithium metal anodes is a major obstacle for developing high-energy-density rechargeable batteries.
• Understanding the fundamental mechanisms of metal anode surface behavior is crucial for designing stable battery systems.

Purpose of the Study:

• To investigate the surface migration energy barrier (MEB) as a descriptor for dendrite nucleation on metal anodes.
• To compare the dendrite formation propensity of lithium (Li) and magnesium (Mg) using computational methods.

Main Methods:

• Utilized density functional theory (DFT) calculations to determine the migration energy barriers (MEBs) for surface transport of Li and Mg atoms.
• Analyzed the atomic coordination and surface distortion associated with atom migration on different crystallographic structures.

Main Results:

• The MEB for the hexagonal close-packed (HCP) structure was found to be significantly lower than that for the body-centered cubic (BCC) structure for both Li (40 meV) and Mg (270 meV).
• Mg surfaces exhibit lower MEBs compared to Li surfaces, suggesting a reduced tendency for dendrite formation.
• Close-packed facets demonstrate lower MEBs due to minimal changes in atomic coordination and reduced surface distortion during migration.

Conclusions:

• The migration energy barrier is a valid descriptor for predicting dendrite nucleation on metal anodes.
• Magnesium anodes are predicted to be less prone to dendrite formation than lithium anodes due to differences in their surface migration energetics.
• The reduced surface distortion on close-packed facets contributes to their lower migration energy barriers and potentially enhanced stability.