Effect of binder types on performance of spherical and flaky silicon electrodes

Silicon nanomaterials have received much attention due to their ability to adapt to large volume changes and thus avoid fragmentation. Studies have shown that two-dimensional flaky silicon particles (F–Si) have better mechanical stability than spherical silicon particles (S–Si), but the larger specific surface area of flaky silicon highlights the problem of chemical stability. A suitable binder can stabilize the surface of the silicon particles through interaction with the silicon particles. This work is a comparative study of various binder systems for S–Si and F–Si: sodium carboxymethyl cellulose (CMC), polyacrylic acid (PAA), and sodium alginate (SA). The relationships between the rheological properties of the electrode slurry, the functional group states of the silicon particles and electrode coatings, the state of the dried electrode surface, and the type of binder were investigated. The experimental analysis shows that CMC and SA as rigid binders exhibit better cycling performance in S–Si/F–Si electrodes due to their better dispersion states. The dispersion of S–Si electrodes with higher silanol (Si–OH) content is dominantly influenced by electrostatic repulsion, and that of F–Si electrodes with lower Si–OH content is dominantly influenced by bridging. The experimental analysis demonstrates that CMC and SA as rigid binders exhibit better cycling performance in S–Si/F–Si electrodes, respectively, due to their better dispersion states. The dispersion of S–Si electrodes with higher silanol Si–OH content is dominantly influenced by electrostatic repulsion, and that of F–Si electrodes with lower Si–OH content is dominantly influenced by bridging.