Modeling of porous lithium metal electrodes: turning the Li-dendrite problem around

TL;DR

This paper presents a finite element model for porous lithium metal electrodes, showing how microstructural design can enhance stability and performance by controlling current distribution and preventing dendrite formation.

Contribution

The study introduces a new finite element modeling approach to analyze porous lithium electrodes, linking microstructure to electrochemical stability and performance improvements.

Findings

Peak current density scales with the square root of surface to bulk conductivity ratio and pore size.

Confining lithium plating within pores enhances morphological stability.

A dimensionless parameter predicts peak current density effectively.

Abstract

The properties of rechargeable lithium-ion batteries are determined by the electrochemical and kinetic properties of their constituent materials as well as by their underlying microstructure. Microstructural design can be leveraged to achieve a leap in performance and durability. Here we investigate a porous electrode structure, as a strategy to increase the surface area, and provide structural stability for Li-metal anodes. The porous architecture consists of a mixed electron/ion conductor that function as a scaffold for lithium metal deposition. A new finite element model was developed to simulate the large topological changes associated with Li plating/stripping. This model is used to predict the current density distribution as a function of material and structural properties. A dimensionless quantity that combines Li-ion conductivity, surface impedance and average pore size is shown to be a good indicator to predict the peak current density. Preventing current localization at the separator reduces the risk of cell shorting. The analyses show that the peak current scales as $(hG)^{1/2}$, where $h$ is the ratio between surface and bulk conductivity and $G$ is the average pore size. Stability analyses suggest that the growth is morphologically stable, and that confining Li-plating into pores can enable high-energy density solid-state batteries. In addition to optimizing porous electrodes design, this finite element method can be extended to studying other Li-battery structures.