A water-based binder with 3D network enabling long-cycle-life silicon/graphite composite anode materials for lithium ion batteries

Abstract

A binder with strong bonding and 3D network is proven to be beneficial for the electrochemical performance of silicon anode material. Herein, a water-soluble binder with strong adhesion and 3D conductive structure is prepared by a one-pot method. The polymer consists of acrylic acid (AA), acrylamide (AM), and 2-acrylamide-2-methylpropanesulfonic acid (AMPS) forming a terpolymer (PtA), which is grafted to polyvinyl alcohol (PVA) chains to construct a strong hydrogen bonding 3D conductive network structure (PtA/PVA). The polar groups (-COOH and -CONH2) provide strong hydrogen bonding and intermolecular forces for adhesion, while the introduction of lithium salts and sulfonic acid groups provides fast channels for ion transport. In addition, the PVA links with abundant hydroxyl groups, conferring excellent electrochemical performance of silicon/graphite (Si@C 400) composite anodes. As a result, the Si@C 400 anode with the PtA/PVA binder has a reversible capacity of up to 329.8 mAh g−1 at 0.1C, and it shows a prolonged cycle life of 82.0% after 500 cycles at 0.5C. This study provides a promising strategy to design binder for silicon anodes with enhanced electrochemical properties.