Thermodynamic and Kinetic Properties of the Lithium-Silver System

Area of Science:

• Materials Science
• Computational Chemistry
• Electrochemistry

Background:

• Carbon-silver anodes suppress dendrite formation in solid-state lithium-ion batteries.
• The specific function of silver in reversible lithium deposition/stripping is not understood.
• Thermodynamic and kinetic properties of lithium-silver (Li-Ag) alloys are largely unknown.

Purpose of the Study:

• To investigate phase stability and diffusion mechanisms in Li-Ag alloys using first-principles calculations.
• To elucidate the role of silver in enhancing lithium anode performance in batteries.

Main Methods:

• First-principles density functional theory (DFT) calculations.
• Analysis of phase stability, intermetallic phase formation, and diffusion pathways.
• Investigation of vacancy formation and migration energies across various Li-Ag alloy compositions.

Main Results:

• Two new stable intermetallic phases, Li3Ag and Li11Ag2, were identified in Li-rich Li-Ag alloys.
• Anharmonic energy surface of lithium persists in Li-Ag alloys, impacting stability and mechanical properties.
• Complex diffusion mechanisms, including two-atom and second-nearest neighbor hops, were observed in B2 and γ-brass phases.
• Exceptionally low migration barriers (0.1 eV) were predicted in the D03 Li3Ag phase with increasing lithium concentration.

Conclusions:

• The study provides fundamental insights into the thermodynamic and kinetic behavior of Li-Ag alloys.
• Identified stable phases and low diffusion barriers in Li-rich alloys offer potential for improved lithium anode design.
• Understanding Li-Ag alloy properties is crucial for optimizing next-generation solid-state lithium-ion batteries.