Cooperation of covalent bonds and coordinative bonds stabilizing the Si-binder-Cu interfaces for extending lifespan of silicon anodes.

Binders provide a straightforward and efficient strategy to mitigate the significant challenge of volume expansion in silicon anodes for lithium-ion batteries. To improve the cycle life of silicon anodes, a cross-linked binder carboxymethyl cellulose-phytic acid-pyrrole (CMC-DP) is designed and synthesized using carboxymethyl cellulose, phytic acid, and pyrrole. The numerous hydroxyl groups in phytic acid provide abundant binding sites for the formation of hydrogen and ester bonds. The formation of hydrogen bonds and covalent bonds enhances the mechanical properties of the adhesive. The amino groups in the binder form NSiO covalent bonds with silicon particles, while the hydroxyl and carboxyl groups form (COO)Cu and (OH)Cu coordination bonds with the copper foil, enhancing interfacial adhesion. When the CMC-DP10 (10 µL pyrrole) binder is applied to silicon nanoparticles (∼30 nm), the specific capacity of the electrode can be maintained at around 1700 mAh/g after 500, whereas the CMC binder achieves only ∼100 mAh/g under the same conditions. This work demonstrates that the CMC-DP binder exhibits strong adhesion to both silicon nanoparticles and copper foil.