Nat. Commun. 9, 1776 (2018)

Magnetic resonance imaging (MRI) is a widely known medical imaging technique for diagnostics. However, its application in battery characterization is greatly limited due to the reliance of MRI on radiofrequency penetration, which can be easily impeded by the conductive enclosures in commercial cells. Now, Jerschow and co-workers employ MRI to non-destructively identify the state of charges and defects in a rechargeable lithium-ion cell without need for disassembly.

This is achieved by measuring permanent and small induced magnetic field changes using magnetic resonance methods. The magnetic susceptibility χ is material dependent and changes due to variation of the oxidation states of the anode and cathode materials during charge/discharge cycles. The researchers map the evolution of the magnetic field distribution over the cycles. By matching the magnetic field changes to the levels of charge, they can extract the magnetic susceptibility and information about the state of charge. Aside from examining the state of the lithium-ion cell over time, MRI is also capable of assessing the quality of the cell. It is very sensitive and thus not only identifies the flaws but also probes reproducibility of the cell construction. The MRI method for diagnosing remaining charge and cell health can come in handy in manufacturing processes.