A multifunctional self-healing binder with strong interfacial interactions and structural stability for high-energy-density silicon anodes

Abstract

Silicon (Si) is a promising anode material for high-energy-density lithium-ion batteries (LIBs); however, its severe volume expansion during repeated cycling induces particle pulverization and the loss of electrical contact, leading to rapid capacity degradation. To address these challenges, we propose a multifunctional self-healing polymer binder, poly(acrylic acid)-4-aminophenyl disulfide (PAA-APDS), designed to enhance interfacial adhesion and structural stability of Si anodes. The PAA-APDS binder effectively dissipates mechanical stress arising from volume changes through its three-dimensional (3D) network composed of multiple hydrogen bonds and dynamic disulfide bonds. Notably, it provides superior adhesion strength (6.5 N) via strong Cu–S interfacial bonding with the Cu current collector and spontaneously repairs microcracks owing to its intrinsic self-healing properties. As a result, the Si/PAA-APDS electrode exhibits an excellent capacity retention of 94.91% after 300 cycles while maintaining a robust electrode structure. Simultaneously, the optimized binder structure facilitates lithium-ion transport, yielding a 2.1-fold increase in the Li⁺ diffusion coefficient (D_Li⁺) compared to pristine PAA and improving the rate capability. Furthermore, a pouch full-cell configuration (NCM622||SiO_x@C/PAA-APDS20) maintained a capacity of 10 mAh after 50 cycles, demonstrating the practical applicability of this binder for Si-based high-energy density LIBs.