Graded lithium-ion battery pouch cells to homogenise current distributions and mitigate lithium plating

TL;DR

This paper proposes a graded electrode microstructure method for large lithium-ion pouch cells to achieve uniform current distribution, reduce lithium plating risk, and enhance high C-rate performance, validated through modeling and experiments.

Contribution

It introduces a novel electrode grading technique and an analytical model to optimize current distribution in large pouch cells, improving their high-rate capabilities.

Findings

Graded electrodes can increase the C-rate before lithium plating occurs from 2.4C to 4.3C.

The mathematical model accurately predicts temperature and voltage behavior.

Grading significantly homogenizes current distribution across the cell.

Abstract

Spatial distributions in current, temperature, state-of-charge and degradation across the plane of large format lithium-ion battery pouch cells can significantly impact their performance, especially at high C-rates. In this paper, a method to smooth out these spatial distributions by grading the electrode microstructure in-the-plane is proposed. A mathematical model of a large format pouch cell is developed and validated against both temperature and voltage experimental data. An analytical solution for the optimal graded electrode that achieves a uniform current distribution across the pouch cell is then derived. The model predicts that the graded electrodes could significantly reduce the likelihood of lithium plating in large format pouch cells, with grading increasing the C-rate at which plating occurs from 2.4C to 4.3C. These results indicate the potential of designing spatially varying electrode architectures to homogenise the response of large format pouch cells and improve their high rate performance.