Shape-controlled synthesis of cobalt-based nanocubes, nanodiscs, and nanoflowers and their comparative lithium-storage properties.

Facile hydrothermal methods have been developed to synthesize large Co3O4 nanocubes, β-Co(OH)2 hexagonal nanodiscs and nanoflowers. Samples are thoroughly characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller method, and thermogravimetric analysis. The Co3O4 nanocubes have an average size of about 350 nm with a perfect cubic shape, and the β-Co(OH)2 nanodiscs are uniform hexagonal platelets, whereas the β-Co(OH)2 nanoflowers are assembled from large sheetlike subunits. After thermal annealing in air at a moderate temperature, the as-prepared β-Co(OH)2 samples can be converted into spinel Co3O4 without significant alterations in morphology. We have also investigated the comparative lithium storage properties of these three Co3O4 samples with distinct morphologies. The nanoflower sample shows highly reversible lithium storage capability after 100 charge-discharge cycles.