Laser-directed covalent Si–N–C bonding at SiOx/3D graphene interface for durable composite anodes in lithium-ion battery

Silicon-carbon composite anodes hold the promise to resolve the irreversible capacity fading of silicon in lithium-ion batteries but face persistent challenges dominated by unstable, physical interfacial contacts. Herein, a laser-directed covalent bonding strategy is developed to construct atomic-scale Si–N–C bridges between silicon suboxide (SiOx) nanoparticles and a 3D nitrogen-doped graphene framework. Localized photothermal processing of polyimide-urea-SiOx precursors on carbon-coated copper foil enables in situ integration of chemically anchored SiOx within a conductive graphene network. The architecture achieves dual stabilization: (i) strong Si–N–C covalent bonds suppress interfacial cracking, while (ii) hierarchical porosity accommodates strain via elastic deformation. Critically, direct fabrication eliminates slurry-derived defects, ensuring structural integrity and minimized interfacial impedance. The optimized composite anode delivers 1826.4 mAh g-1 at 0.1 A g-1 and retains 91.3% capacity over 1000 cycles at a high current density of 2.0 A g-1, demonstrating exceptional stability under high-rate operation. Mechanistically, density functional theory (DFT) reveals that Si–N–C bonding lowers lithium-ion (Li⁺) adsorption energy (–6.549 eV) and redistributes interfacial charge density, synergistically accelerating ion transport. This work provides atomic-scale insights into covalent interface design and establishes a scalable laser-processing strategy of composite anodes for durable high-energy-density batteries.