Synthesis and electrochemical properties of Co3O4 nanofibers as anode materials for lithium-ion batteries
Introduction
During the past decade, lithium-ion batteries have been widely used as power sources for modern portable electronics devices. The cathode materials mainly determined the capacity of the lithium-ion batteries, but it was believed that the anodes materials play an important role on the properties of batteries such as cycling life, rate capability and safety. With progress of the electrode materials, it has been proposed that transitional metal oxides could be used as new anode materials for lithium-ion batteries [1], [2], [3], [4], [5], [6]. Among them, nanocrystalline tricobat teraoxide (Co3O4) has attracted considerable attention due to its high reversible capacity and electrochemical stability [7], [8], [9]. Generally, Nanostructured Co3O4 was prepared by various traditional methods such as solid-state reaction [6], hydrothermal oxidation [10] and template method [9].
In this work, we were successful in synthesizing Co3O4 with nanofiber structure through an electrospinning process. The morphology, crystal structure and electrochemical properties of Co3O4 nanofibers were systematically investigated in detail.
Section snippets
Experiments
Co3O4 nanofibers were synthesized according to the procedure described in a previous work by some of us [11], [12], [13]. All the chemicals were of analytical purity and used as received. Cobalt nitrate (Co(NO3)2·6H2O) and polyvinyl pyrrolidone (PVP, MW = 30,000) were dissolved into ethanol, then the resultant solution was continuously agitated at room temperature. The solutions contained 0.3 mol L− 1 of Co(NO3)2 and 20 wt.% of PVP. Then the solution of Cobalt nitrate/PVP composites was loaded
Results and discussion
The XRD patterns of Co3O4 nanofibers annealed at different temperature were shown in Fig. 2. All the hkl peaks could be indexed to the pure Co3O4 with spinel structure. When cobalt nitrate/PVP fibers membrane annealed at 500 °C, the crystalline peaks of Co3O4 appeared with low intensity. With the raise of the calcined temperature, all the peaks enhanced and the crystal structure tended toward perfection. To obtain perfect crystal structure of Co3O4 nanofibers, it was necessary to heat the
Conclusions
In this paper, Co3O4 nanofibers with high reversible capacity were prepared by using electrospinning. The average diameter of the Co3O4 nanofibers was about 200 nm and the nanofiber was composed of ultrafine Co3O4 nanoparticles with average diameter less than 50 nm. The initial discharge capacity of Co3O4 nanofibers annealed at 700 °C was 1336 mAhg− 1, after 40 cycles, the discharge capacity maintained 604 mAhg− 1.
Acknowledgements
This work was performed by the financial support of Natural Science Foundation of China (No:10372087, 10672138), Department of Science and Technology of Hunan province of China (No:03JZY1002) and Department of Education of Hunan province of China (No:07A071).
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