# Zinc Electrode Shape-Change in Secondary Air Batteries: A 2D Modeling Approach

## TL;DR

This paper introduces a 2D multi-physics model of zinc-air batteries that simulates zinc shape-change during cycling, validated with tomography, and used to optimize battery performance and lifespan.

## Contribution

It presents the first multi-dimensional simulation of zinc-air batteries, including zinc shape-change and validation with experimental tomography data.

## Key findings

- Zinc shape-change impacts cycle-life significantly.
- Charging current is the main factor limiting cycle-life.
- Optimized initial anode structure improves battery performance.

## Abstract

Zinc-air batteries offer large specific energy densities, while relying on abundant and non-toxic materials. In this paper, we present the first multi-dimensional simulations of zinc-air batteries. We refine our existing theory-based model of secondary zinc-air systems. The model comprises thermodynamically consistent multi-species transport in alkaline electrolytes, formation and dissolution of metallic zinc and passivating zinc oxide, as well as multi-phase coexistence in gas diffusion electrodes. For the first time, we simulate zinc shape-change during battery cycling by modeling convection of zinc solids. We validate our model with in-situ tomography of commercial button cells. Two-dimensional volume-averaged simulations of cell voltage and zinc electrode morphology during discharge agree with these measurements. Thus, we can study how electrolyte carbonation limits shelf-life and how zinc shape-change limits cycle-life. The charging current is found to be the major contributor to cycle-life limitations. Finally, we optimize initial anode structure and charge-discharge protocols for improved performance and cycle-ability.