The cornlike ordered mesoporous silicon (OM-Si) particles modified by the nitrogen-doped carbon layer (OM-Si@NC) are successfully fabricated and used as the anode of lithium-ion battery (LIBs). The influences of the N-doped carbon layer on the structure and electrochemical properties of the OM-Si@NC composite are detailedly investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectrum, X-ray photoelectron spectroscopy (XPS), and charge/discharge tests. The results reveal that the amorphous N-doped carbon layer can offer the abundant conductive pathways for fast lithium ion transportation and electron transfer, which not only leads to a high specific capacity under high ampere density but also serves as a structural barrier maintaining the whole integrity and settling the mechanical breaking due to the huge volume changes of Si host. Therefore, the as-synthesized OM-Si@NC composite exhibits a high original discharge capacity of 2548 mA h g under 0.2 A g as well as a large reversible capacity of 1336 mA h g under 1 A g after 200 circles. The OM-Si@NC composite prepared by a relatively simple and feasible synthesis method shows excellent electrochemical performances and turns out to be promising for the application of high power LIBs.

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Silicon (Si) has been considered as the most promising anode material for next generation lithium-ion batteries (LIBs) due to its ultrahigh theoretical specific capacity (4,200 mAh g–1) and volume capacity (9,786 mAh cm–3), relatively low operating voltage (∼0.5 V vs Li+/Li), the abundant natural Si source, and environmental benignity. However, the huge volume expansion and poor conductivity limit seriously the electrochemical reversibility and cycling stability of silicon-based anode materials, and thus hinder their commercial application. To address these issues, herein we put forward a strategy to prepare the spherical graphite/silicon/graphene oxides/carbon (Gr/Si/GO/C) composite by electrostatic self-assembly and spray drying process. The structure and morphology of the as-prepared samples are characterized by X-ray diffraction (XRD), Raman spectrum, Fourier transform infrared spectroscope (FTIR), scanning electron microscope (SEM), electron backscatter diffractometer (EBSD), and transmission electron microscope (TEM). The results show that the as-synthesized Gr/Si/GO/C composite has a high discharge capacity of 1212.0 mAh g–1 at 200 mA g–1 with the initial Coulombic efficiency (ICE) of 80.4%, and the capacity retention rate is 81.7% after 100 cycles. Apparently, the as-prepared spherical Gr/Si/GO/C composite can well buffer the volume expansion of silicon, maintain the structural integrity of the electrode, enhance stability by reducing silicon aggregation, and promote the electric and ionic conductivity as well Li storage ability. Therefore, this strategy of reasonable structure design provides a beneficial exploration for the large-scale industrial application of silicon-based anode materials.

At present, the main limitations for the practical application of silicon (Si) as an anode material of a lithium-ion battery are huge volume variation and low electrical conductivity. Core–shell silicon/carbon (Si/C) composites can greatly relieve the Si large volume change and accelerate the low Li+ conductivity; however, cracking of carbon shell and the failure of the electrode structure still limit the lithium storage capability and cyclic life. Herein, a flexible freestanding N-doped core–shell Si/C nanofiber (SC-NF) anode is prepared by the double-nozzle electrospinning technique. It has been found that in such fibers, Si particles are encapsulated by the carbon shell of fibers, which can settle the shortcomings of pulverization and volume variation of Si. Furthermore, the highly conductive N–C shell derived from carbonized PAN can accelerate the diffusion of Li+ and charge transport. As a result, the as-prepared core–shell SC-NF-0.24 electrode exhibits an initial specific discharge capacity of 1441 mAh g–1 with a high capacity retention of 76.9% at 0.5 A g–1, and the capacity decay rate of per cycle is only 0.1% (starting on the third cycle), showing a good cycle property. Therefore, the as-prepared freestanding core–shell SC-NF material is a prospective anode material for high-performance lithium-ion batteries.