Fig. 4a gives a SEM photograph of the electrospun SnSb@C/PAN nanofibers, it reveals the fibrous structure. Fig. 4b–d shows the SEM images of SnSb@C/C hybrid nanofibers named sample A, B and C after heat treatment, respectively. For all the three samples, PAN was pyrolyzed to black carbon and the morphology changed from straight fibers to reticular structure, where gradient formed between layer by layer, and hole staggered with hole. Comparing among Fig. 4b–d, there are some protrusions on the surface of sample A, but the surface of sample B is smoother than sample A, while sample C has the smoothest surface and the gradient among layers is densest. The morphological change of sample C caused by carbonization process can be further confirmed by the TEM image shown in Fig. 4e. It can be clearly seen that SnSb@C nanoparticles dispersed in the carbonized fibers and there are many small pores around the particles. During the carbonization process of PAN, one byproduct is the CO2 gas, which evolves around the active particles and acts as a template, causing the formation of the pores around SnSb alloys [31]. The remarkable difference in morphology must influence the electrochemical performance significantly.