Fabrication of Hollow Co3O4 Nanospheres and Their Nanocomposites of CNT and rGO as High-Performance Anodes for Lithium-Ion Batteries

We report an efficient method for fabrication of Co3O4 hollow nanospheres (CHN) by self-assembly process using poly(styrene-b-2-vinylpyridine-b-ethylene oxide) micelle as a soft template and [(NH4)(2)Co(SO4)(2)center dot 6H(2)O] as cobalt source. To mitigate the capacity fading of Co3O4, nanocomposites of CHN with multi-walled carbon nanotubes (MWCNT) and reduced graphene oxide (rGO) were synthesized by a simple sonication followed by hydrothermal treatment. The cationic shell block with positively charged 2-vinylpyridine units (pH4) electrostatically interacts with anionic Co(II) species during the self-assembly and subsequently condenses to form CHN. A combined structural and morphological characterization indicates that the CHN, rGO, and MWCNT were well integrated within the nanocomposite. Powder X-ray diffraction (XRD) pattern of pristine CHN clearly confirms the formation of pure cubic phase of Co3O4. The morphological features such as particle size, void space diameter, and shell thickness were evaluated using a transmission electron microscope (TEM) and average diameter of hollow nanosphere was found to be 27 +/- 2nm. The nanocomposite CHN/rGO and CHN/CNT constructed electrodes exhibit higher charge/discharge capacities (similar to 943 mAh g(-1)) when compared to pristine CHN based electrode (similar to 678 mAh g(-1)) in LIBs after 50 cycles. Both CHN/rGO and CHN/CNT deliver high specific capacity, rate capability, and electrode stability vis-a-vis cycling performance compared to CHN.