Non-invasive Current Density Imaging of Lithium-Ion Batteries

TL;DR

This paper introduces a non-invasive magnetometry technique to image internal current distributions in lithium-ion batteries, enabling rapid assessment of battery health and safety without opening the cell.

Contribution

It presents a novel application of external magnetometry sensors to visualize internal current flows in batteries, advancing diagnostic capabilities.

Findings

Good agreement between measured and modeled magnetic fields.

Detection of percent-level deviations in current density.

Potential for real-time battery health monitoring.

Abstract

The rapid pace of replacing fossil fuel propelled transport by electric vehicles is critically dependent on high-performing, high energy density and efficient batteries. Optimal and safe use of existing battery cells and development of much-needed novel battery chemistries and geometries require a large range of diagnostic and monitoring tools. While structural and chemical information is readily extracted through a host of imaging techniques, non-invasive functional detection of interior battery processes remains limited. Here we introduce sensitive magnetometry performed outside the battery that reveals a battery cell's internal current distribution. As a key application, we use an array of sensors to image the magnetic field present under cycling of a pouch cell between charge states. We find good agreement between measured and modelled fields with sufficient resolution to detect percent-level deviations around areas of high current density. This opens the path towards rapid and reliable assessment throughout the battery life cycle, from battery development and manufacturing quality assurance to operational safety and optimised use.