Deconvoluting Slurry Rheology from Binder Performance in Si-Based Anodes

A systematic investigation was undertaken on the effect of sodium poly(acrylic acid) (NaPAA) binder molecular weight on silicon monoxide cycling performance. It was found that cycling performance was poor for low molecular weight binder, however this was primarily related to poor slurry rheology. We found that if propylene glycol is used instead of water as a slurry solvent, it can take over the role of viscosity modifier from the binder. When propylene glycol is used as a solvent for slurries with low MW NaPAA binders (e.g. 1.5 k NaPAA), the cycling outperformance of the resulting SiO electrodes outperforms conventionally made SiO electrodes with high molecular weight binder (e.g. 250 k NaPAA). These results show that binder molecular weight only affects the cycling performance of Si-alloy based electrodes because of its role as a slurry viscosity modifier. If propylene glycol is used to increase slurry viscosity, then the molecular weight has little effect.