Non-invasive Current Density Imaging of Lithium-Ion Batteries

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.

Modular optically-pumped magnetometer system

“…OPMs offer reduced separation distances over SQUIDs, which is of particular interest for magnetoencephalography (MEG) [4][5][6][7], where OPM-MEG is able to offer an improved spatial [8,9], and spatio-temporal [10] resolution. These advantages can be similarly applied to the diagnostic measurement of batteries through non-invasive current mapping [11,12], and for fundamental physics research [13,14]. While OPMs offer many advantages over SQUIDS, a number of challenges remain, especially around the construction of dense arrays.…”