Through a facile hydrothermal method with a special surfactant triethanolamine (TEA) followed by thermal treatment, monodispersed micro-/nanostructured Co3O4 powders with unique morphology (cube) have been synthesized successfully as anode material for Li-ion batteries (LIBs). The regular Co3O4 microcubes (∼2.37 μm in the average side length) consist of many irregular nanoparticles (20-200 nm in diameter, 30-40 nm in thickness) bonded to each other, which greatly inherit the morphology and size of the precursor CoCO3. The specific surface area of Co3O4 powders is about 5.10 m(2)·g(-1) by the Brunauer-Emmett-Teller (BET) method, and the average pore size is about 3.08 nm by the Barrett-Joyner-Halenda (BJH) method. In addition, the precursor is verified as a single-crystal, while the mesoporous cubic Co3O4 is a polycrystalline characteristic assembled by numerous single-crystal nanoparticles. More remarkable, the high performance of the micro-/nanostructured cubic Co3O4 powders has been obtained by the electrochemical measurements including high initial discharge capacities (1298 mAhg(-1) at 0.1 C and 1041 mAhg(-1) at 1 C), impressive rate capability, and excellent capacity retention (99.3%, 97.5%, 99.2%, and 89.9% of the first charge capacities after 60 cycles at 0.1 C, 0.2 C, 0.5 C, and 1 C, respectively).

No abstract

No abstract

For advanced performance lithium-ion batteries (LIBs) various novel electrode materials with high energy density have been extensively investigated. Cobaltosic oxide (Co3O4), commonly used as an anode in LIBs, has attracted much interest because of its high theoretical specific capacity (890 mAh•g-1), high tap density, and stable chemical properties. However, its practical use has been hindered because of its low electronic conductivity and poor rate capability. To address these problems, we investigated a liquid phase precipitation method followed by thermal treatment and obtained a unique lamellar Co3O4 powder. Its X-ray diffraction (XRD) diffraction peaks match the standard pattern for cubic phase Co3O4 with good crystallinity. We found that the Co3O4 powder consists of many irregular sheets (1.5-3.0 µm in diameter, 100-300 nm in thickness) with numerous poles by scanning electron microscopy (SEM). Additionally, the surface area was about 30.5 m 2 •g-1 , and this was calculated from BET nitrogen adsorption isotherm measurement data. Remarkably, perfect performance was obtained as evaluated by electrochemical measurements, including a high initial discharge capacity (1444.5 mAh•g-1 at 0.1C) and excellent capacity retention (charge capacity after 50 cycles was still greater than 1100.0 mAh•g-1 at 0.1C). However, its rate capability was still not adequate (75.3% of the first charge capacity after 50 cycles at 1C). To improve the rate capability, commercial carbon nanotubes (CNTs) mixed with the Co3O4 powder was used to enhance the electronic conductivity. The charge capacity retention ratios were 96.3% after 70 cycles at 1C and 97.0% after 50 cycles at 2C. Therefore, enhanced electrochemical performance with impressive rate capability was obtained, as expected.