Shape matters: Understanding the effect of electrode geometry on cell resistance and chemo-mechanical stress

TL;DR

This paper investigates how electrode shape influences electrical resistance and mechanical stress in 3D battery electrodes, revealing a trade-off between reduced resistance and increased stress concentrations, with interdigitated designs offering a balanced solution.

Contribution

It introduces a combined electrostatics and chemo-mechanics modeling approach to analyze the effects of electrode geometry on performance and stress in shaped battery cells.

Findings

Shaped electrodes significantly reduce electrical resistance.

Interdigitated electrode designs balance resistance reduction and stress concentration.

Shape optimization can improve battery performance but may increase mechanical stress.

Abstract

Rechargeable batteries that incorporate shaped three-dimensional electrodes have been shown to have increased power and energy densities for a given footprint area when compared to a conventional geometry, i.e., a planar cathode and anode that sandwich an electrolyte. Electrodes can be shaped to enable a higher loading of active material, while keeping the ion transport distance small, however, the relationship between electrical and mechanical performance remains poorly understood. A variety of electrode shapes have been explored, where the electrodes are individually shaped or intertwined with one another. Advances in manufacturing and shape and topology optimization have made such designs a reality. In this paper, we explore sinusoidal half cells and interdigitated full cells. First, we use a simple electrostatics model to understand the cell resistance as a function of shape. We focus on low-temperature conditions, where the electrolyte conductivity decreases and the governing dimensionless parameters change. Next, we use a chemo-mechanics model to examine the stress concentrations that arise due to intercalation-driven volume expansion. We show that shaped electrodes provide a significant reduction in resistance, however, they result in unfavorable stress concentrations. Overall, we find that the fully interdigitated electrodes may provide the best balance with respect to this trade-off.