Grain boundaries control lithiation of solid solution substrates in lithium metal batteries

TL;DR

This study investigates how microstructural features like grain boundaries influence lithium distribution and lithiation behavior in solid solution substrates, providing insights to improve lithium metal battery performance.

Contribution

It demonstrates the impact of grain boundary character and microstructure on lithiation, highlighting pathways to enhance battery stability and reduce dendrite formation.

Findings

Li nucleates at grain boundaries, not interiors

Grain size and boundary character affect lithiation kinetics

Microstructure influences mechanical constraints and lithiation behavior

Abstract

The development of sustainable transportation and communication systems requires an increase in both energy density and capacity retention of Li-batteries. Using substrates forming a solid solution with body centered cubic Li enhances the cycle stability of anode-less batteries. However, it remains unclear how the substrate microstructure affects the lithiation behavior. Here, we deploy a correlative, near-atomic scale probing approach through combined ion- and electron-microscopy to examine the distribution of Li in Li-Ag diffusion couples as model system. We reveal that Li regions with over 93.8% at.% nucleate within Ag at random high angle grain boundaries, whereas grain interiors are not lithiated. We evidence the role of kinetics and mechanical constraint from the microstructure over equilibrium thermodynamics in dictating the lithiation process. The findings suggest that grain size and grain boundary character are critical to enhance the electrochemical performance of interlayers/electrodes, particularly for improving lithiation kinetics and hence reducing dendrite formation.