Multi-technique analytical framework for quantifying manufacturing-induced binder heterogeneity in slurry-processed composite films

Abstract

During drying of slurry-cast composite films, solvent-driven binder migration can induce microstructural heterogeneity and compromise mechanical integrity. Despite its importance in manufacturing, quantitative assessment of binder redistribution remains challenging due to the compositional complexity of multicomponent systems and the limitations of single analytical techniques. In this study, we present a cross-validated multi-technique analytical framework designed for manufacturing process diagnosis, integrating micro-infrared (micro-IR) spectroscopy, electron probe microanalysis (EPMA), and micro-scratch testing (MST) to characterize binder heterogeneity and its mechanical implications. Micro-IR enables rapid, large-area mapping of polymer binders through molecular-specific vibrational signatures, while EPMA provides complementary validation of binder-related elemental contrast in multicomponent systems. MST further links near-surface binder enrichment to interfacial cohesion and mechanical integrity. Using polyvinylidene fluoride (PVDF)-based LiNixCoyMnzO2 cathode films as a representative system, we demonstrate increasing surface binder enrichment at higher drying temperatures. Consistent trends across molecular, elemental, and mechanical readouts establish quantitative processing–microstructure–mechanical response correlations in this PVDF-based system. The agreement among these three complementary contrast mechanisms cross-validates binder heterogeneity, demonstrates the value of the combined analytical approach beyond any single technique, and supports the broader design principle of the framework, with potential adaptation to other composite films. © 2026 Elsevier Ltd.