A biomacromolecule-based covalent-hydrogen bonding dual network binder for ultra-high initial coulombic efficiency silicon anode in lithium-ion batteries

Silicon anodes are regarded as one of the most promising alternatives to commercial graphite anodes due to their exceptionally high theoretical specific capacity (4200 mAh g −1 ). However, their widespread application is currently hindered by challenges such as significant volume expansion (>300 %), an unstable solid electrolyte interphase (SEI) layer, and poor electrical conductivity. To address these limitations, this study introduces a novel covalent–hydrogen bonding dual-network binder (Si@PCG) for silicon anodes, composed of the highly polar biomolecule chondroitin sulfate (CS), the ionic conductor polyethylene oxide (PEO), and conductive graphene oxide (GO). Compared to conventional binders such as PVDF (initial Coulombic efficiency, ICE: 32.8 %) and CMC (ICE: 82.3 %), the Si@PCG anode achieves significantly higher ICE (89.7 % at 0.01–1.5 V and 92.3 % at 0.01–3 V). Additionally, the PCG binder exhibits strong interfacial adhesion and lower hardness, enabling its elastic dual-network structure to efficiently dissipate stress caused by silicon volume expansion. This results in outstanding structural stability, reflected in a remarkably low thickness increase of only 5.49 % after 100 cycles. Furthermore, the PCG binder promotes the formation of a LiF-rich inorganic SEI layer, which further stabilizes the interface and enhances long-term cycling. The Si@PCG anode exhibits excellent ICE, high rate capability, and superior cycling performance in both half-cell and full-cell configurations. These results demonstrate a simple and scalable strategy for developing high-performance binders for silicon anodes and advance the practical application of lithium-ion batteries. • This study introduces a dual-network binder for silicon anode with initial Coulombic efficiency and cycling stability.