Citric Acid as a Small Molecule Binder for Si-Based Li-Ion Battery Anode Materials

In this study, citric acid (CA) dissolved in propylene glycol (PG) was shown to be an effective binder/solvent system for Si-based anode materials in Li-ion batteries. In this system, PG serves both as a slurry solvent and provides viscosity to the slurry to inhibit the settling of active particles and for proper rheology during the coating process, while the small CA molecule serves as a binder/artificial solid electrolyte interphase. After 50 cycles, SiO/carbon black/CA electrodes had a higher capacity retention (93%) than conventional electrodes with lithium polyacrylate (LiPAA) polymeric binder (68%), due to superior maintenance of adhesion amongst active particles. This demonstrates that small molecules may be used as effective binders for Si-based anode materials when a slurry solvent is used that can take on the role of maintaining the slurry rheology.