Probing electrochemical phenomena in commercial pouch cells using a multimodal magnetic resonance approach

Abstract

Further advances in portable electrochemical energy storage will increasingly depend on multifunctional in situ diagnostic tools capable of probing materials at the molecular level under realistic operating conditions. This capability is essential for achieving an optimal balance between energy density, cycle life, and safety. The increasing energy density of battery cells reinforces the need for rapid, reliable, and non-destructive diagnostics, including evaluation of state-of-health (SoH) and state-of-charge (SoC). Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) are highly sensitive to the environment and dynamics of key electrochemical elements, but most common industrial cell designs present significant obstacles: (a) interrogated nuclear spins are shielded from the radio-frequency (RF) field by conductive metallic structures such as casings and jelly roll sheets of the current collectors, and (b) magnetism from bulk metallic components causes misregistration artefacts and reduces resolution and signal-to-noise ratio. Surface-scan MRI and plug-and-play (PnP) NMR are two distinct in situ modalities designed to address these challenges. In this work, we combine the PnP RF adapter and surface-scan MRI sensor into a single multimodal device suitable for a wide range of academic and industrial applications, including SoH analysis and recycling. We illustrate the capabilities of this approach through complementary NMR and MRI experiments, highlighting diverse lithium environments and their transformations during electrochemical cycling in commercial LiCoO₂‖graphite pouch cells.