Spatial Heterogeneities and Onset of Passivation Breakdown at Lithium Anode Interfaces

TL;DR

This study investigates how nanoscale heterogeneities at lithium anode interfaces influence passivation breakdown, revealing that grain boundary pores in Li2O facilitate lithium growth, while LiF offers better resistance, informing battery design.

Contribution

It provides a detailed atomic-level analysis of how surface heterogeneities affect passivation stability and lithium dendrite formation in solid-state batteries.

Findings

Li2O grain boundaries with large pores enable lithium insertion and electron leakage.

Strain reduces the overpotential needed for lithium growth.

LiF films are more resistant to lithium filament formation.

Abstract

Effective passivation of lithium metal surfaces, and prevention of battery-shorting lithium dendrite growth, are critical for implementing lithium-metal-anodes for batteries with increased power densities. Nanoscale surface heterogeneities can be "hot spots" where anode passivation breaks down. Motivated by the observation of lithium dendrites in pores and grain boundaries in all-solid batteries, we examine lithium metal surfaces covered with Li(2)O and/or LiF thin films with grain boundaries in them. Electronic structure calculations show that, at >0.25 V computed equilibrium overpotential, L(2)O grain boundaries with sufficiently large pores can accommodate Li(0) atoms which aid electron leakage and passivation breakdown. Strain often accompanies Li-insertion, applying a ~1.7% strain already lowers the computed overpotential to 0.1 V. Lithium metal nanostructures as thin as 12 Angstroms are thermodynamically favored inside cracks in Li(2)O films, becoming "incipient lithium filaments." LiF films are more resistant to lithium metal growth. The models used herein should in turn inform passivating strategies in all-solid-state batteries.