A Universal\nPlug-and-Play Approach to <i>In Situ</i> Multinuclear Magnetic\nResonance Analysis of Electrochemical Phenomena\nin Commercial Battery Cells

Advancing electrochemical\nenergy storage devices relies on versatile\nanalytical tools capable of revealing the molecular mechanisms behind\nthe function and degradation of battery materials <i>in situ</i>. The nuclear magnetic resonance phenomenon plays a pivotal role\nin fundamental studies of energy materials and devices because of\n its exceptional sensitivity to local environments and the dynamics\nof many electrochemically relevant elements. The jelly roll architecture\nis one of the most energy-dense and, therefore, most popular concepts\nimplemented in pouch, prismatic, and cylindrical Li- and Na-ion cells.\nSuch widely commercialized designs, however, represent a significant\nobstacle for a range of powerful <i>in situ</i> magnetic\nresonance-based methodologies due to negligible radio frequency electromagnetic\nfield penetration through conductive metal casings and current collectors.\nIn this work, we introduce an experimental setup that enables direct\nRF wave transmission through the cell terminals and current collectors,\nand provides efficient excitation and detection of NMR signals. An\nRF adapter designed as a <i>plug-and-play</i> device effectively\nturns the battery cell into an NMR probe that can be tuned to a broad\nrange of Larmor frequencies. Due to its exceptional sensitivity, versatility,\nand multinuclear capability, the proposed methodology is suitable\nfor fundamental research and industrial high-throughput screening\napplications. <i>In situ</i> NMR lineshapes provide a direct\nquantitative description of the chemical environments of electrochemically\nactive elements and enable new metrics for the accurate assessment\nof state-of-charge (SoC) and state-of-health (SoH). Specifically,\nin commercial pouch cells based on lithium cobalt oxide, lithium nickel\nmanganese cobalt oxide, and sodium nickel iron manganese oxide chemistries, <sup>7</sup>Li and <sup>23</sup>Na NMR data unambiguously show electrochemical\ntransformations between intercalated and metallic forms of charge\ncarrier ions, and reveal anisotropic magnetic properties of the electrode\ncoating.