A Boat-Paddle-Like Molecule Binder with Twining-Blocked and Ultrafast Self-Healing Functionalities for Stable Silicon Anodes.

Self-healing binder is a prospective and efficient strategy to alleviate volume expansion of silicon (Si) anodes. However, excellent mechanical strength and healing ability tend to be mutually exclusive, due to enhanced tensile stress limit by twining polymer chains, while inhibiting polymer diffusion rate and inducing healing failure by blocked chains. Herein, inspired by the planning course of boat and paddles, a novel self-healing binder (PVA-4FBA-PEI) is designed and synthesized with mobile parallel structure and twining-blocked characteristics. The boat-like intermediate (4-formylphenyl) boronic acid (4FBA) blocks entanglement of poly(vinyl alcohol) (PVA) and poly(ethyleneimine) (PEI) chains, where two parallel chains as paddles can simultaneously form to ensure rapid diffusion of chains during bond breakage. Remarkably, it endows dynamic synergistic covalent bonds via C═N and B─O─C junctions within 4FBA, providing the binder with an ultrafast self-healing time of merely 2 min. Moreover, the binder integrates superior plasticity and flexibility of each chain, showing a high tensile strength (14.4 MPa) and stretchability (1163%) among state-of-the-art polymer binders, thus significantly improving structural integrity and electrochemical stability of Si anode during cycling. This work proposes a dynamic reversible structure via figurative molecular coordination, affording a rational viewpoint on synergetic functionalities of polymer binders for Si anodes.