Coaxial single-walled CNT@SnO2@N-doped carbon with high rate capability and cycling stability for lithium ion batteries

Abstract

To improve rate performance and cycling stability of SnO2-based anode material, we have used single-walled carbon nanotube (SWCNT) with extraordinary high electrical conductivity as a core to construct a coaxial nanocable of SWCNT@SnO2@N-doped carbon (SWCNT@SnO2@NC) by hydrothermal treatment, polymerization, and thermal annealing. In which, SWCNTs are served as flexible and conductive substrates for active SnO2 nanoparticles, which allow fast electrons transport and accommodate volume variation of SnO2 NPs during cycling. The coaxial structure can inhibit severe agglomeration of SnO2 nanoparticles during the growth process and maintain good electrical contact between active SnO2 nanoparticles and conductive network. Moreover, we have used PDA pyrolysis to synthesis the N-doped carbon layer. The intrinsic adhesive nature of PDA enables it to protect SnO2 nanoparticles from detaching from SWCNT conductive network much better. When used as a electrode, the N-doped carbon layer makes the solid electrolyte interphase (SEI) film stable and ensures good electrical contact between SnO2 and the conductive network during cycling tests. With these advantages of the structural design, the coaxial SWCNT@SnO2@NC anode demonstrates excellent rate capability and cycling stability.