Thermodynamics of Lithium Stripping and Limits for Fast Discharge in Lithium Metal Batteries

TL;DR

This paper uses thermodynamic and computational methods to analyze lithium metal surface behavior during discharge, identifying surface stability factors that influence fast discharge capabilities in lithium metal batteries.

Contribution

It introduces a thermodynamic framework and density functional theory calculations to understand vacancy formation and surface stability during lithium stripping.

Findings

(111) surface is least prone to pitting issues

Faceting control can enable both fast charge and discharge

Vacancy congregation is key to void and pit formation

Abstract

Lithium metal batteries are seen as a critical piece towards electrifying aviation. During charging, plating of lithium metal, a critical failure mechanism, has been studied and mitigation strategies have been proposed. For electric aircraft, high discharge power requirements necessitate stripping of lithium metal in an uniform way and recent studies have identified the evolution of surface voids and pits as a potential failure mechanism. In this work, using density functional theory calculations and thermodynamic analysis, we investigate the discharge process on lithium metal surfaces. In particular, we calculate the tendency for vacancy congregation on lithium metal surfaces, which constitutes the first step in the formation of voids and pits. We find that among the low Miller index surfaces, the (111) surface is the least likely to exhibit pitting issues. Our analysis suggests that faceting control during electrodeposition could be a key pathway towards simultaneously enabling both fast charge and fast discharge.