Multivalent Amide-Hydrogen-Bond Supramolecular Binder Enhances the Cyclic Stability of Silicon-Based Anodes for Lithium-Ion Batteries.

A supramolecular polymer, poly(N-acryloyl glycinamide) (PNAGA), with a bisamide group on each side of the chain forming multiple amide-hydrogen bonds was synthesized in this work as a binder for silicon (Si)-based anodes. This supramolecular polymer binder with improved mechanical properties presents good interfacial adhesion with Si particles forming hydrogen bonds and enhances the adhesive strength between the electrode material film and the copper current collector. Benefiting from the highly stable inter- and intramolecular multiple amide-hydrogen bonds of the PNAGA binder, the electrode structure maintains integrity and a stable solid electrolyte interphase (SEI) layer is formed on the surface of Si particles. The effect of different binders on the composition of the SEI film was also investigated by X-photoelectron spectroscopy (XPS) characterization. In comparison with polyacrylamide (PAM), which has a similar structure to PNAGA, and the traditional sodium alginate (SA) binder, the Si electrode containing the PNAGA binder shows improved electrochemical performance. The capacity retention is 84% after 100 cycles at 420 mA g-1, and the capacity remains at 1942.6 mAh g-1 after 400 cycles at 1260 mA g-1. Even with a mass loading of 1.2 mg cm-2 Si, the electrode with the PNAGA binder exhibits high initial areal capacity (2.64 mAh cm-2) and good cycling performance (81% capacity retention after 50 cycles). Moreover, the application of the PNAGA binder also brings a stable cycle performance to the commercial Si-graphite (SiC) anode material.