Preparation of 3D hierarchical porous Co 3 O 4 nanostructures with enhanced performance in lithium-ion batteries.

Three-dimensional hierarchical Co 3 O 4 microspheres assembled by well-aligned 1D porous nanorods have been synthesized by hydrothermal methods with the help of CTAB and subsequent heat treatment. The morphology and compositional characteristics of the hierarchical Co 3 O 4 microspheres have been investigated using different techniques. Based on the SEM and TEM analyses, the growth direction of the nanorods is in the [110] direction. The hierarchical Co 3 O 4 microspheres have a comparatively large Brunauer-Emmett-Teller surface area of about 50.2 m 2 g -1 , and pore size distribution is mainly concentrated at 12 nm. On the basis of the time tracking experiment, a possible growth mechanism has been proposed. It demonstrates that the overall mechanism includes nucleation, oriented growth and self-assembly processes. These hierarchical Co 3 O 4 microspheres provide several favorable features for Li-ion battery applications: (1) large Brunauer-Emmett-Teller surface area, (2) porous structure, and (3) hierarchical structure. Therefore, measurement of the electrochemical properties indicates that the specific capacity can maintain a stable value of about 1942 mA h g -1 at a current of 100 mA g -1 within 100 cycles.