Cross-Linked Polymer Binder Mitigating Silicon Pulverization via Synergistic Stress Dissipation and Preferential SEI Formation

Poly(acrylic acid) copolymers containing nitrile and hydroxyl groups are synthesized through free radical polymerization and used as binders for silicon anodes. The characteristics of these poly(acrylic acid) copolymers are that they can be further <i>in situ</i> cross-linked through the Ritter reaction. The cross-linked binder (<i>c</i>-PACH-2) can simultaneously address the challenges of mechanical degradation, sluggish kinetics, and interfacial instability in the Si anode. The cross-linked architecture can mitigate volume expansion and prevent particle pulverization via elastic stress dissipation. Concurrently, ionic pathways and hopping sites accelerate Li⁺ diffusion, enabling superior rate capability. Density functional theory calculations and X-ray photoelectron spectroscopy analyses reveal <i>c</i>-PACH-2's preferential reduction to form a robust LiF-rich SEI film, reducing parasitic reactions. The <i>c</i>-PACH-2 binder delivers exceptional electrochemical performance, and the <i>c</i>-PACH-2@Si||Li cell has a capacity retention of 67.2% after 100 cycles at 0.2 C. This covalent network design integrates mechanical resilience and ion transport in the binders for the Si anode, offering an effective strategy for developing high-performance batteries.