Hollow Silicon–Tin Nanospheres Encapsulated by N-Doped Carbon as Anode Materials for Lithium-Ion Batteries

The hollow mesoporous silicon–tin nanohybrids modified through the homogeneous N-doped carbon matrix are purposely designed and triumphantly synthesized as anode materials of high-performance lithium-ion batteries (LIBs). The influences brought by the introduction of the Sn element and N-doped carbon layer on the structure, morphology, and properties of nanohybrids are studied in detail by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectra, X-ray photoelectron spectroscopy (XPS), and galvanostatic charge–discharge tests. It can be found that the hollow Si/Sn@N–C nanohybrids possess a steady cycling capacity of 1246 mA h g–1 after 200 cycles at 0.5 A g–1. In particular, the Si/Sn@N–C nanohybrids still deliver a reversible discharge capacity of 613 mA h g–1 even at a rate of 8 A g–1. The outstanding electrochemical performance can be assigned to the fact that the hollow porous microstructure can render adequate buffer space and shorten the transport path. Moreover, the presence of Sn element further relieves the volume change in virtue of the step-by-step alloying process, and the nitrogen-doped carbon layer forms a favorable conductivity framework, thus increasing the structural stability and rate capability. Furthermore, the design of the hollow mesoporous Si–Sn composite is a viable approach for improving the energy density of LIBs at the current cell configurations and manufacturing processes.