Accurate Visualization of Operating Commercial Batteries Using Specialized Magnetic Resonance Imaging with Magnetic Field Sensing

The lithium-ion cell is the leading electric energy-storage technology reducing the environmental impact of fossil fuels. Their high energy density makes Li-ion batteries inherently dangerous due to the possibility of thermal runaway. Prerelease battery diagnostics incorporated at the final stages of cell manufacturing can improve personal and public safety and reduce the environmental impact of failures. An innovative diagnostic technique termed inside-out magnetic resonance imaging (io-MRI) measures magnetic field (MF) perturbations outside the battery's conductive casing. Weak magnetic fields produced by an operating cell during charge-discharge events can reveal early signs of the battery's malfunction and shed light on the electrochemical phenomena occurring at the electrodes. Since commercial cells are strongly magnetic, and magnetic objects are known to bring about failures of MRI methodology, the choice of MRI technique becomes central to the analysis. Single-point ramped imaging with T₁ enhancement (SPRITE) is immune to notorious "susceptibility" artefacts due to its fully phase-encoded three-dimensional (3D) acquisition. SPRITE enables rapid distortion-free visualization of magnetic field patterns associated with a cell's mechanical integrity, state of charge, and operating mode. Io-SPRITE in combination with a solid-state detection-medium device achieved sensitive and safe measurements of current-induced magnetic fields very close to the surface of the cell.