Well-Dispersed Co/CoO/C Nanospheres with Tunable Morphology as High-Performance Anodes for Lithium Ion Batteries

Well-dispersed Co/CoO/C nanospheres have been designed and constructed through a facile electrospinning method with a strategy controlling the morphology of nanocomposites via adjusting the pre-oxidized and heat treatments. Scanning electron microscopy results reveal that the as-synthesized sample pre-oxidized at 275 °C shows better spherical morphology with a diameter of around 300 nm without conspicuous agglomeration. X-ray diffraction analysis confirms the coexistence of cobalt and cobalt monoxide in the sample. Furthermore, the electrochemical tests reveal that the sample pre-oxidized at 275 °C displays excellent cycling stability with only 0.016% loss per cycle even after 400 cycles at 1000 mA·g^-1 and enhanced high-rate capability with a specific discharge capacity of 354 mA·g^-1 at 2000 mA·g^-1. Besides, the sample pre-oxidized at 275 °C shows a specific capacity of 755 mA·g^-1 at 100 mA·g^-1 after 95 cycles. The improved electrochemical performance has been ascribed to the well dispersion of nanospheres, the improved electronic conductivity, and the structural integrity contribution from the carbon and cobalt coexisting nanocomposite. The strategy for preparing well-dispersed nanospheres by adjusting pre-oxidized and annealing processes could have insight for other oxide nanosphere synthesis.