Synthesis of NiO Nanofibers Composed of Hollow Nanospheres with Controlled Sizes by the Nanoscale Kirkendall Diffusion Process and Their Electrochemical Properties

NiO nanofibers composed of hollow NiO nanospheres with different sizes were prepared by electrospinning method. The mean size of the hollow NiO nanospheres was determined by the mean size of the Ni nanocrystals of the Ni-C composite nanofibers formed as an intermediate product. Porous-structured NiO nanofibers were also prepared as a comparison sample by direct oxidation of the electrospun nanofibers. The discharge capacities of the nanofibers composed of hollow nanospheres reduced at 300, 500, and 700 °C for the 250th cycle were 707, 655, and 261 mA h g^-1, respectively. However, the discharge capacity of the porous-structured NiO nanofibers for the 250th cycle was low as 206 mA h g^-1. The nanofibers composed of hollow nanospheres had good structural stability during cycling.