Binder Influence on Rheological Impedance and Graphite Anode Properties

This study investigates the application of simultaneous rheology and impedance spectroscopy (rheo-impedance) for aqueous graphite anode slurries using sodium carboxymethyl cellulose (NaCMC) of varying degrees of substitution (DS), with and without the addition of styrene-butadiene rubber (SBR). Rheo-impedance results reveal that lower DS leads to higher slurry impedance. Interestingly, SBR addition reduces impedance across all formulations, with the strongest effect for DS 0.34, suggesting an unanticipated role of surfactants present in commercial SBR formulations in enhancing carbon additive dispersion. The trends in rheo-impedance are directly translated into the electrical resistance of the anodes, with stronger correlations for less dispersing systems like DS 0.34. However, other anode properties, such as adhesion and water retention, are not affected by changes in rheo-impedance. Electrochemical testing confirms that optimal performance is achieved from a balance between dispersion and water retention, with DS 0.75 showing the best rate capability in this comparison. Thereby, this study demonstrates the potential of rheo-impedance to help better understand electrically relevant features of the slurry and carbon dispersion without the need for coating.