Fast method for assessing binder migration in lithium-ion battery electrodes using glow discharge-sector field-mass spectrometry.

A high amount of energy needed for the production of lithium-ion batteries is used for the drying and solvent recovery of N-methyl-2-pyrrolidone (NMP) in electrodes with polyvinylidene fluoride-based binder (PVdF) systems. Therefore, controlling the amount of used solvent as well as developing efficient drying procedures is of major importance. Furthermore, the drying process and solid content of the electrode paste directly affect the battery performance due to the risk of transport of the binder towards the electrode surface. This work focuses on an analytical approach for rapidly and reliably assessing the degree of this migration by measuring the fluorine distribution via glow discharge-sector field-mass spectrometry (GD-SF-MS). A sample with notably more binder migration based on preliminary cross-section imaging via scanning electron microscopy combined with energy-dispersive X-ray spectroscopy and a reference sample with no visualized binder migration were evaluated, with the former displaying a severely elevated degree of binder migration over the reference based on GD-SF-MS analysis. The developed method could also be applicable to electrodes based on sodium carboxymethyl cellulose (Na-CMC) binders by investigating the Na distribution instead.