A new concept for obtaining SnO₂ fiber-in-tube nanostructures with superior electrochemical properties

Tin oxide (SnO₂) nanotubes with a fiber-in-tube structure have been prepared by electrospinning and the mechanism of their formation has been investigated. Tin oxide-carbon composite nanofibers with a filled structure were formed as an intermediate product, which were then transformed into SnO₂ nanotubes with a fiber-in-tube structure during heat treatment at 500°C. Nanofibers with a diameter of 85 nm were found to be located inside hollow nanotubes with an outer diameter of 260 nm.The prepared SnO₂ nanotubes had well-developed mesopores.The discharge capacities of the SnO₂ nanotubes at the 2nd and 300th cycles at a current density of 1 Ag^-1 were measured as 720 and 640 mAhg^-1, respectively, and the corresponding capacity retention measured from the 2nd cycle was 88%.The discharge capacities of the SnO₂ nanotubes at incrementally increased current densities of 0.5, 1.5, 3, and 5 Ag^-1 were 774, 711, 652, and 591 mAhg^-1, respectively.The SnO₂ nanotubes with a fiber-in-tube structure showed superior cycling and rate performances compared to those of SnO₂ nanopowder.The unique structure of the SnO₂ nanotubes with a fiber@void@tube configuration improves their electrochemical properties by reducing the diffusion length of the lithium ions, and also imparts greater stability during electrochemical cycling.