CMC Staining Method for the Visualization of the Binder Distribution in Water-Based Electrodes with EDS

Abstract

The selective staining of cellulose materials is crucial for the accurate investigation of the binder distribution in electrodes of lithium-ion batteries. This paper investigates how (heptadecafluorodecyl)trimethoxysilane selectively reveals the binder distribution via EDS. Selectivity was granted by investigating individual electrode components: graphite, carbon black (CB), styrene–butadiene rubber (SBR), and sodium carboxymethyl cellulose (NaCMC). Each component was treated with the staining agent, stored at 60 °C for 16 h, washed with ethanol, and analyzed via energy dispersive spectroscopy (EDS). Only NaCMC shows a significant increase in fluorine concentration, proving selective staining. The study further explores the reaction mechanism by varying the degree of substitution (DS) of NaCMC, showing a correlation between carboxyl moieties and fluorine concentration and identifies 16 h of heated storage as a viable staining condition. Finally, the method’s applicability was demonstrated by comparing binder distribution in electrodes dried at different rates, revealing the NaCMC binder distribution via EDS.