Nondestructive Inline Evaluation of Wet-Deposited LFP Electrode Films Using an Ultrabroadband Photonic FMCW Radar

Non-destructive inspection of lithium-ion battery components using terahertz technologies is emerging as a powerful approach for quality control during electrode manufacturing. In this work, we present inline terahertz reflectometry measurements of LiFePO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> (LFP) cathode coatings immediately after wet deposition onto the aluminum current collector. Using a photonic frequency-modulated continuous wave (FMCW) radar system with tunable bandwidth, we probe the optical response of the wet coating and evaluate thickness in the presence of strong solvent absorption. Our results demonstrate the capability of the terahertz photonic FMCW radar for non-contact, real-time monitoring during the wet coating process. Given the system's compact form factor and spectral flexibility, future implementations may extend this approach to simultaneous multi-point inspection across different production stages, offering a scalable solution for full-process battery quality control.