Grain Boundaries Control Lithiation of Solid Solution Substrates in Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Sustainable transportation and communication demand improved lithium-ion battery energy density and capacity retention.
• Solid solution substrates with body-centered cubic lithium enhance anode-less battery cycle stability.
• The influence of substrate microstructure on lithium-ion battery lithiation behavior is not well understood.

Purpose of the Study:

• To investigate how substrate microstructure affects lithium (Li) lithiation behavior in Li-Ag diffusion couples.
• To elucidate the mechanisms governing lithiation at high current densities.
• To identify microstructural features critical for enhancing electrochemical performance.

Main Methods:

• Employed a correlative, near-atomic scale probing approach.
• Combined ion- and electron-microscopy techniques.
• Utilized a Li-Ag diffusion couple as a model system for high current density lithiation.

Main Results:

• Lithium-rich regions (over 93.8 at.%) nucleated specifically at random high-angle grain boundaries within the silver substrate.
• Grain interiors remained unlithiated, indicating selective lithiation.
• Evidence suggests kinetics and mechanical constraints from microstructure dominate over equilibrium thermodynamics.

Conclusions:

• Substrate microstructure, specifically grain size and grain boundary character, critically influences lithium-ion battery performance.
• Optimizing grain boundaries can enhance lithiation kinetics.
• Reducing dendrite formation is a key benefit of controlling microstructure for improved electrochemical performance.