Electrochemical Properties of Fiber-in-Tube- and Filled-Structured TiO₂ Nanofiber Anode Materials for Lithium-Ion Batteries

Phase-pure anatase TiO₂ nanofibers with a fiber-in-tube structure were prepared by the electrospinning process. The burning of titanium-oxide-carbon composite nanofibers with a filled structure formed as an intermediate product under an oxygen atmosphere produced carbon-free TiO₂ nanofibers with a fiber-in-tube structure. The sizes of the nanofiber core and hollow nanotube were 140 and 500 nm, respectively. The heat treatment of the electrospun nanofibers at 450 and 500 C under an air atmosphere produced grey and white filled-structured TiO₂ nanofibers, respectively. The initial discharge capacities of the TiO₂ nanofibers with the fiber-in-tube and filled structures and the commercial TiO₂ nanopowders were 231, 134, and 223 mA h g^-1, respectively, and their corresponding charge capacities were 170, 100, and 169 mA h g^-1, respectively. The 1000th discharge capacities of the TiO₂ nanofibers with the fiber-in-tube and filled structures and the commercial TiO₂ nanopowders were 177, 64, and 101 mA h g^-1, respectively, and their capacity retentions measured from the second cycle were 89, 82, and 52 %, respectively. The TiO₂ nanofibers with the fiber-in-tube structure exhibited low charge transfer resistance and structural stability during cycling and better cycling and rate performances than the TiO₂ nanofibers with filled structures and the commercial TiO₂ nanopowders. Phase-pure anatase TiO₂ nanofibers with a fiber-in-tube structure are prepared by the electrospinning process. The prepared TiO₂ nanofibers with a fiber-in-tube structure show better cycling and rate performances than the TiO₂ nanofibers with filled structure and the commercial TiO₂ nanopowders.