Bioinspired phosphorylated cellulose nanocrystals-based multi-crosslinked binder for enhanced stability and sustainability in silicon anodes.

Silicon (Si) is a promising anode for high-energy-density batteries, but its ~300 % volume expansion causes particle fracture and electrode instability. Effective binders are essential for maintaining electrode integrity. Inspired by the adhesion mechanism of natural ivy, we developed a small-molecule-enhanced polymer binder derived from phosphorylated cellulose nanocrystals (PCNCs) and acrylic acid rosin to enhance the electrochemical and mechanical performance of Si anodes. PCNCs, with their high aspect ratio and surface activity, construct an interconnected three-dimensional (3D) network within the polymer matrix, reinforcing structural stability. Additionally, phosphate groups promote water-based polymer compatibility and ion transport, facilitating efficient lithium-ion conduction. Acrylic acid rosin mimics the adhesion mechanism of Parthenocissus tricuspidata, establishing strong hydrogen bonds, ion-dipole interactions, and covalent crosslinking with Si particles. This incorporation also forms a unique "soft outside, rigid inside" topology, buffering stress, protecting the solid electrolyte interface (SEI), and synergizing with polyacrylic acid (PAA) to form a robust network. The binder provides an excellent electrochemical performance, achieving a high initial coulombic efficiency (86.85 %), superior ionic conductivity (18.825 mS/cm2), and remarkable cycling stability at high silicon loading (maintaining 1272 mAh/g after 100 cycles at 0.2C). Its green synthesis and scalability offer a sustainable path for next-generation Si anodes.