Coaxial CNT@Si/SiO_x Nanowires Enable High-Capacity and Stable Lithium Storage

Si represents a promising anode material to complement graphite in commercial lithium-ion batteries (LIBs). Whereas, its practical implementation is still hampered by unsatisfactory cyclability, primarily caused by the lithiation/delithiation-induced large volume variation. One-dimensional (1D) Si-based nanostructures offer effective volumetric change accommodation, yet their facile fabrication remains challenging. Herein, we develop a facile sol-gel method to synthesize 1D coaxial core@shell structured CNT@Si/SiO_x nanowires. The material features a CNT core and a Si/SiO_x composite shell, in which sub-5 nm Si grains (3-5 nm) are uniformly embedded in an SiO_x matrix. The design achieves a high reversible capacity (1078 mAh g^-1 at 0.1 A g^-1), high-rate capability (540 mAh g^-1 at 10 A g^-1), and decent cyclability (867 mAh g^-1 after 200 cycles at 2 A g^-1). This contribution provides a scalable strategy for designing stable, high-capacity Si anodes.