A Multifunctional Interlocked Binder with Synergistic In Situ Covalent and Hydrogen Bonding for High‐Performance Si Anode in Li‐ion Batteries

Silicon has garnered significant attention as a promising anode material for high-energy density Li-ion batteries. However, Si can be easily pulverized during cycling, which results in the loss of electrical contact and ultimately shortens battery lifetime. Therefore, the Si anode binder is developed to dissipate the enormous mechanical stress of the Si anode with enhanced mechanical properties. However, the interfacial stability between the Si anode binder and Cu current collector should also be improved. Here, a multifunctional thiourea polymer network (TUPN) is proposed as the Si anode binder. The TUPN binder provides the structural integrity of the Si anode with excellent tensile strength and resilience due to the epoxy-amine and silanol-epoxy covalent cross-linking, while exhibiting high extensibility from the random coil chains with the hydrogen bonds of thiourea, oligoether, and isocyanurate moieties. Furthermore, the robust TUPN binder enhances the interfacial stability between the Si anode and current collector by forming a physical interaction. Finally, the facilitated Li-ion transport and improved electrolyte wettability are realized due to the polar oligoether, thiourea, and isocyanurate moieties, respectively. The concept of this work is to highlight providing directions for the design of polymer binders for next-generation batteries.