Core-shell structured porous carbon nanofibers integrated with ultra-small SnO2 nanocrystals for fast and stable lithium storage

Abstract

• Core-shell structured SnO 2 /N-doped carbon nanofibers have been rational designed. • The structure and composition of the anodes have been precisely regulated. • Enhanced lithium storage capacity and excellent cyclic stability have been achieved. Significant improvements for lithium storage have been achieved by rational design and synthesis of porous composite nanofibers. In this work, ultrasmall SnO 2 nanoparticles (<5 nm) were anchored on one-dimensional MOF assembly derived N-doped porous carbon nanofibers, and were further coated by a disordered graphitized carbon shell (PCNF@SnO 2 @CN). In the constructed core–shell structured composite, the uniform distribution of ultrasmall SnO 2 nanoparticles can short the lithium diffusion distance and reduce the mechanical stress, the MOF electrospun nanofibers and polydopamine derived N-doped graphitized carbon can improve the conductivity and realize fast charge transport, and the hard carbon shell that could prevent the expansion of SnO 2 is also crucial to the cycling performance. Besides, the 1D porous structure not only buffers the expansion/contraction of the electrode but also depresses particle agglomeration during the charge/discharge process and improves the structural integrity. Moreover, the high surface area can make sufficient contact between active material and electrolyte. Based on the structural and compositional advantages, the PCNF@SnO 2 @CN electrode shows high rate capability, enhanced initial lithium storage capacity, and excellent cyclic stability (1101 mAh g −1 at 0.1 A g −1 after 100 cycles and 962 mAh g −1 at 5 A g −1 after 3500 cycles).