We develop a new system and capability for performing in situ electrochemical nuclear magnetic resonance (EC-NMR) spectroscopy on batteries with the aim to measure spectroscopic data during battery cycling. In traditional battery NMR, the battery under investigation is placed inside a solenoid coil. The metal battery electrodes, essential to the battery operation, are necessarily also placed inside the coil, which lowers the sensitivity and resolution of the resulting data. In the case of electrodes that are thick compared to the radiofrequency skin depth at the NMR frequency, in situ NMR may be impossible. In that case, the rf field is effectively screened by the metal electrodes and is prevented from imparting the magnetic energy necessary for NMR to the interior of the battery. Our system, in contrast, uses an internal stripline detector. The essential 2-dimensional stripline detector is built into the battery itself during fabrication, and allows high quality NMR data to be obtained in situ during battery operation regardless of the thickness of the electrodes. Initial ⁷Li NMR results on pouch cell batteries with a variety of cathode materials (LiFePO₄, LiCoO₂, and LiNi₅Mg₃Co₂O₂) versus a graphite anode are discussed. The EC-NMR system can be used to study any NMR active nucleus of interest and so is versatile in studying a variety of battery types. This technique has the potential to allow investigation of many poorly-understood battery chemistries, and provides the means to monitor the creation and consumption of chemical species during actual battery operation conditions.

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This work was funded by the Sandia Exploratory Express LDRD program.