Room-temperature synthesis of Co(OH)2 hexagonal sheets and their topotactic transformation into Co3O4 (111) porous structure with enhanced lithium-storage properties

The beta-Co(OH)(2) sheets with uniform hexagonal shape were prepared using NaBH4 as the structure directing agent at room temperature. After thermal annealing in air at 450 degrees C for 2 h, the as-prepared beta-Co(OH)(2) sheets were converted into porous Co3O4 with the hexagonal sheet-like morphology (H-Co3O4). The textural properties of the as-prepared samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy and powder X-ray diffraction. The results of lithium storage capability indicate that the H-Co3O4 electrode exhibits excellent cycleability and rate capacity. At a charge/discharge current density of 50 mA g(-1), a reversible capacity of 914 mAh g(-1) can be maintained after 40 cycles. When the current density is increased to 1600 mAh g(-1), a reversible capacity of 800 mAh g(-1) can be still obtained. The superior electrochemical performance is attributed to the porous 2D structures with a finite lateral size and enhanced open-edges, which facilitate Li-ion and electron diffusion through active materials. (C) 2013 Elsevier Ltd. All rights reserved.