Syntheses, Characterizations, And Applications In Lithium Ion Batteries Of SnO Nanocrystals

Particular attentions have been paid to the development of metal oxide nanocrystals with defined sizes and shapes in recent years. During this development, the unique optical, electronic, and magnetic properties of metal oxide nanocrystals have been utilized for the practical applications, such as transparent electrodes, catalysis, and gas sensors. Such applications mainly focus on metal oxide nanocrystals with zero- or one-dimensional (0D or 1D) structures, because of the well-developed ability to control their size and size distribution. Comparatively less is known about three-dimensional (3D) metal oxide nanocrystals, accompanied by the synthetic complexity and difficulty. As one of these complicated 3D structures, metal oxide nanoflowers have recently attracted great interest for their unique technical potential that is inaccessible with the 0D or 1D counterpart. For instance, metal oxide nanoflowers were reported to be ideal structures for fabrications of high-rate electrochemical capacity in energy storage applications. It is expected to obtain good electrochemical performance by preparation of hierarchical SnO nanocrystals. Recently, a few synthetic routes have been used to synthesize SnO nanocrystals. SnO nanoribbons, diskettes, dendrites, plates, meshes, truncated bipyramid and stacked combs have been produced.A facile and reproducible approach was reported to synthesize nanoparticle-attached SnO nanoflowers via decomposition of an intermediate product Sn6O4(OH)4. Sn6O4(OH)4 formed after introducing water into the traditional nonaqueous reaction, and then decomposed to SnO nanoflowers with the help of free metal cations, such as Sn2+, Fe2+, and Mn2+. This free cation-induced formation process was found independent on the nature of the surface ligand. It was demonstrated further that the as-prepared SnO nanoflowers could be utilized as good anode materials for lithium ion rechargeable batteries with a high capacity of around 800 mA·h·g-1, close to the theoretical value (875 mA·h·g-1).Hierarchical SnO nanocrystals are synthesized by a reproducible and facile way via decomposition of an intermediate product tin oxide hydroxide, Sn6O4(OH)4. By changing the amount of injecting water, layer-plates like, nest like, stepwised-bipyramid like, and defective stepwised-bipyramid like hierarchical SnO nanocrystals could be obtained. All these hierarchical SnO nanostructures are constructed by smaller nanosheets. The drive force of aggregation is reducing surface energy of nanocrystals. Water played a key role in the control morphologies of hierarchical SnO nanostructures. New water control decomposition (WCD) mechanism was proposed to explain the effect of water to the morphologies. Based on reaction kinetic, the different left injected water after reaction would restrain the decomposition of Sn6O4(OH)4, different amount of left injected water would induce different reaction rate. At different reaction rate, SnO nanosheets would have different size and different approach to aggregate, so different hierarchical SnO nanocrystals appeared by injecting different amount of water into reaction. Typically, hierarchical SnO nanocrystals as an anode material for lithium ion batteries are studied. These SnO nanocrystals show good potential for lithium battery materials. Among these SnO nanostructures, stepwised-bipyramid like nanostructure shows the best properties.SnO nanoplates, nanosheets and nanorings have been synthesized by a simple and facile approach. By changing the reaction temperature, SnO nanoplates would become to individual SnO nanosheets. Complex nanostructures disassemble to its basic unit. When reaction temperature is much higher, novel SnO nanorings by assemble of nanosheets appear. Assemble processes and disassemble processes are observed in this experiment. Ligand plays a key role in the morphology evolution of nanocrystals. The ligand interaction mechanism is proposed to explain the transition from nanoplates to nanosheets, and ligand protection mechanism is used to explain the formation of nanorings.