Small Molecule Slurry Additives for Si Alloy Coatings with CMC/SBR Binder

Abstract

Sodium carboxymethyl cellulose (CMC) jointly used with styrene butadiene rubber (SBR) has become a standard binder formulation for graphite negative electrodes in Li-ion batteries. Including Si-alloys in the electrode formulation can increase capacity, however CMC/SBR binders are not optimal for this task. Other advanced binders (e.g. polyacrylic acid, polyimide, etc.) have been found to be far superior to CMC/SBR when Si-alloys are used, however such binders can be difficult to use commercially. In this study the use of small molecule slurry additives to improve the performance of CMC/SBR binders is explored. It was found that additives with a high concentration of carboxyl groups can improve the capacity retention of Si-alloy in electrodes using CMC/SBR binders substantially. This could enable Li-ion cell manufacturers to incorporate Si-alloys in negative electrodes using existing binder systems.