Effects of sodium carboxymethyl cellulose and poly (acrylic acid) on the agglomeration behavior of aqueous silicon suspensions

Abstract

We investigate the effects of carboxymethyl cellulose (CMC) and poly (acrylic acid) (PAA) on the dispersion state of silicon particles and the mechanism thereof. Here, we report severe agglomeration of silicon particles induced by the hydrophobic interaction arising from CMC(degree of substitution; DS 0.7). Although the adsorption amount of CMC (DS 0.7) onto the silicon surface is comparable to that of PAA, its effect on particle dispersion is significantly different. The agglomeration mechanism is systematically explored in terms of polymer-polymer and particle-polymer interactions by varying the DS of CMC and the pH of the suspensions. We demonstrate that the attraction between polymers adsorbed on the silicon surface and the affinity between the particle and polymer determine the degree of silicon agglomeration. The hydrophobic attraction of CMC(DS 0.7) promotes silicon agglomeration significantly, whereas CMC(DS 1.2) deficient in attraction disperses silicon particles well. Silicon particles weakly agglomerate in Si/PAA suspensions due to hydrogen bonding between PAA chains and due to the high affinity between PAA and the silicon surface. The dispersion of Si/CMC(DS 0.7 or 1.2)/PAA suspensions is primarily dominated by PAA through its high affinity with silicon and corresponding favorable adsorption on the silicon surface. This is the first attempt to quantitatively assess and compare the impact of CMC and PAA on the agglomeration behavior of silicon particles and reveal the underlying mechanism. This paper provides a fundamental understanding to control the dispersion homogeneity and stability of silicon-containing electrodes.