Parallel-plate RF probe for magnetic resonance and magnetic resonance imaging studies of lithium-ion batteries
University of New Brunswick
Magnetic Resonance (MR) and Magnetic Resonance Imaging (MRI) have become essential techniques to interrogate Lithium-Ion Batteries (LIBs). They are non-destructive and non-invasive techniques that can be employed to study internal processes in LIBs during ex situ, in situ and in operando experiments. The ability to interrogate different chemical species inside the battery, has proven to be essential to study important processes such as lithium intercalation, lithium plating and solid electrolyte interface formation. Improving MR hardware is vital for better investigation leading to performance optimization of LIBs. The presence of conductive materials in the LIB, such as electrodes, and the thickness of these materials, poses challenges to the MR experiment. Signal attenuation during RF excitation and reception is one of the critical issues. In this thesis, Parallel-Plate Resonator (PPR) RF probes are presented and optimized for LIB studies. The PPR, with magnetic field B1 parallel to the plates avoids RF attenuation due to the presence of the conductive electrodes. The B1 homogeneity of the probe was improved with distributed capacitance in the corners of the probe. The PPR was first designed and optimized for thin-film imaging. With improved homogeneity and a nominal resolution of 10 µm, the PPR proved to be ideal for the study of flat cuboid samples. Bulk T1-T2 relaxation correlation measurements of LIBs were introduced in this thesis. A PPR combined with a cartridge-like LIB cell was employed in the measurement. The T1-T2 relaxation correlation detected lithium intercalated into graphite in addition to other Li species. The versatility of the PPR was also explored. The RF probe was tested over a wide range of frequencies from 8 MHz to 500 MHz. The PPR performed well in all situations with no change in the quality factor after sample insertion. Finally, the PPR was combined with a variable field superconducting magnet to perform multinuclear studies on a LIB. This preliminary study showed good sensitivity to the three nuclei under study. These results open the door to the development of new methods for detection and quantification of MR data from LIBs.