Poly-crystalline silicon particles with a diameter of 80∼100 nm were synthesized by the plasma arc discharge method. Natural graphite, poly-crystalline silicon, poly-crystalline silicon/graphite composite and phosphorus doped poly-crystalline silicon/graphite composite particles were used as the anode materials of lithium secondary batteries and their electrochemical performances were compared. The phosphorus component on the surface and internal structure of the silicon particles were observed by XPS and SIMS analyses, respectively. In our experiments, the phosphorus doped silicon/graphite composite electrode exhibited better cycle performance than the intrinsic silicon/ graphite composite electrode. The discharge capacity retention efficiency of the intrinsic silicon/graphite composite and phosphorus doped silicon/graphite composite electrodes after 20 cycles were 8.5% and 75%, respectively. The doping of phosphorus leads to an increase in the electrical conductivity of silicon, which plays an important role in enhancing the cycle performance. The incorporation of silicon into graphite has a synergetic effect on the mitigation of the volume change and conducting medium in the composite electrode during the charge-discharge reaction.

We have demonstrated an approach to the synthesis of SiOx ‐core nanowires, on which ZnO shell layer would be subsequently deposited. We have discussed the possible growth mechanism of SiOx nanowires, in regard to the role of Au catalyst. For a comparison study between uncoated and coated nanowires, samples were characterized by X‐ray dif‐ fraction (XRD), transmission electron microscopy (TEM), and photoluminescence spectroscopy (PL). This method can be applied to a wide range of materials and results in various heterostructures, which may serve as potential building blocks in various nanodevices. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

This study reports the production of magnesium oxide (MgO) whiskers on silicon (Si) substrates by the thermal heating of MgB 2 powders. We investigated the structural properties of the as-synthesized whiskers by using X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and scanning electron microscopy. The product consisted of onedimensional whiskers with a square cross-section. The whiskers had a singlecrystalline cubic structure of MgO. The photoluminescence measurement with the Gaussian fitting exhibited visible light emission bands centered at 2.39 eV and 2.91 eV. We proposed the growth of MgO whiskers to follow the vapor-solid mechanism.

We have prepared MgO/Au core-shell nanowires, subsequently demonstrating the fabrication of Au nanotubes by using MgO nanowires as a sacrificial template. The samples were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. MgO nanowires were coated with a conformal layer of Au via sputtering. By etching away the MgO core in aqueous (NH3)2SO4 solution, hollow nanotube-like structures of Au were readily obtained. This approach offers a potentially useful route for the fabrication of a variety of hollow metallic structures.

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Carbonaceous material has been used as an anode in lithium-ion secondary batteries due to their good stability during charging and discharging. But this material has the problems like irreversible capacity and low specific capacity that is about 372mAh/g. Because of the problems as stated above, silicon-based materials have been reported as possible anode materials to replace carbon. But they have high electrical resistivity and large volume changes associated with alloying and dealloying of lithium during electrochemical cycling. This study is performed to obtain higher capacity of anode material with a good cycle performance and to reduce electrical resistivity. It is expected that phosphor doping silicon and graphite mixture exhibit higher capacity than that of raw graphite and the doping of phosphorous will be able to decrease electrical resistivity of anode materials.