Rheological behavior and microstructure formation of Si/C anode slurries for Li-ion batteries

Abstract

In this study, we systematically investigate the rheological behavior and microstructure formation of the anode slurries containing silicon (Si), carbon black (CB), and carboxymethyl cellulose (CMC) from the perspective of interactions between the constituent components, aiming to provide a fundamental understanding of the dispersion characteristics of Si-based anode slurries. The CMC adsorbs onto both particles (CB/Si) but has different effects on the inter-particle interactions (CB–CB and Si–Si). It stabilizes the CB particles through electro-steric interactions, whereas it agglomerates the Si particles through bridging interactions, in aqueous medium. In the meanwhile, the CMC selectively adsorbs onto CB particles among the two particles. Therefore, at a CMC content lower than the optimum graft density where CB particles are adsorbed and saturated by CMC, it acts as a dispersant in the slurries. However, at a higher content, the CMC that remains after adsorption on CB particles adsorbs onto Si particles and acts as a flocculant for the particles in the slurries. The origin of selective adsorption is understood in terms of the driving forces for adsorption and the surface energy analysis. We anticipate our findings provide a useful guideline for the Si slurry design in terms of its dispersion and contribute to the development of Si anode technology.