| With the rapid development of renewable energy sources, such as the solar and wind energy, large-scale electric energy storage systems are becoming extremely important to realize the smooth harvest of these intermittent energies into the power grid. Among the potential energy storage technologies, electrochemical secondary battery technology is one of the most promising means for large-scale electricity storage because of flexibility, high energy conversion efficiency and simple maintenance. So far, lithium-ion batteries are the most successfully developed technology, which have been widely used in portable electronic devices, electric vehicles, and so on. However further application raises concern for a possible shortage of the limited lithium resources in the Earth’s crust. Sodium, has similar physics and chemical properties with lithium, therefore, alternatively, sodium-ion batteries have again aroused a great deal of interest recently, particularly for large-scale stationary energy storage applications due to the practically infinite sodium resources and their low cost. However, up to now, there are few works based on sodium ion battery, and the technic and materials for sodium ion batteries are immature. Therefore, development of advanced anode and cathode materials for NIBs is urgently desired but remains a great challenge. Hence, research and decvelopment of electrode materials with high capacity and long cycle life for sodium-ion batteries remains a great challenge. Based on the analysis above, we carried out a series of experiments to explore cathode and anode materials for sodium-ion batteries on the basis of lithium-ion technology. In this thesis, we present some pioneering results and original insight of sodium-ion battery, the research contents and results are as follows:1. We first propose and realize a facile and large-scable strategy to fabricate flexible and porous 3D Cu O nanorod array by in situ engracing commercial copper foils. Moreover, the 3D Cu O nanorod array can directly used as electrode for sodium ion batteries without conductive carbon or polymer binders. This method not only decreases the batteries cost, but also simplifies the battery production process which is originally complicated. Furthermore, this 3D nano-array structured Cu O also showed many other advantages than other Cu O, such as high capacity of 630 m A h g-1 at a big current density, superior rate capability(8C, 200 m Ah g-1), and excellent cycling stability. We can draw a concluction from the above results that 3D porous Cu O nano-array is a promissing anode material for high performance sodium ion batteries.2. High capacity, high rate capacility and high energy density sodium ion batteries are realized by a 3D hieraichical single-crystalline Sn Se nanosheet clusters. Such Sn Se nanosheet clusters were synthesised by a fast and effecvtive aqueous method through adjusting suitable alkaline solution environment. It is found that a alkaline solution environment is essential for the synthesis of pure phase Sn Se. When used as anode material in sodium ion batteries, the 3D Sn Se nanosheet structure showed very high reversible capacity of 738 m Ah g-1, which is very close to its theoretical capacity, ultrafast rate capability(40 A g-1, ca. 2400C). Furthermore, when applied as anode material, a full cell based on the 3D Sn Se nanosheets showed a very high discharge platform(~ 3.4 V), a high energy density and excellent cycling stability.3. Na2V6O16·3H2O nanobelts is investigated as high performance sodium ion batteries cathode and symetry batteries electrodes. With uniform size and morphology Na2V6O16·3H2O 1D nanobelts was obtained by a facile hydrothermal method with V2O5, Na OH and H2 O as precursor. Compared with bulk materials, such 1D nanobelts structure has large specific surface area and outstanding flexibility. Additionally, this kind of sodium vanadate with such layered structure not only benificial for Na+ insertion and deinsertion, but can also provide more storage space for Na+. When it used as cathode material for sodium ion batteries, it shows a capacity near 200 m Ah g-1, even applied in symetry batteries, a capacity of more than 130 m Ah g-1 can be obtained in the first discharge process, and the energy density excess 80 Wh kg-1, and a high security can also be achieved.4. 1D pure phase single crystalline Na1.1V3O7.9 nanobelts is study as high capacity and long life sodium ion batteries cathode. A novle layered structure Na1.1V3O7.9 nanobelts were obtained by heat treated Na2V6O16·3H2O nanobelts. Rietveld refinement method was used to further confirm the pure phase and real structure of the obtained Na1.1V3O7.9. When used as cathode material for sodium ion batteries, an excellent performance can be obtained, such as a capacity of more than 170 m Ah g-1, outstanding cycling stability and rate capability. In addition, We also briefly discussed the charge and discharge mechanism of this material. |
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