| Lithium cobalt oxide (LiCoO2) is the main cathode materials in the commercial Lithium-ion batteries. Because its capacity will fade badely if the charging voltage is higher than4.2V, so its charge cutoff voltage is set to4.2V, corresponding to a utilization of50%(its theoretical capacity is274mAhg-1, practical capacity is only137mAhg1),So, increasing the cycle stability of LiCoO2at high voltage is signi ficant. In this paper, we used CuO as the coating material for the first time to improve the cycle stability of LiCoO2at1.5V. Moreover, the product has excellent performance at high charge-discharge rate. In addition, we research detai ledly about the synthesis, growth mechanism, properties of carbon composites materials. We synthesized Cu-core@C-sholl polyhedral composites via a one-pot hydrothermal process, and could release Cu from the carbon shell to30nm size Cu particles under the convergent electron beams in a transmission electron microscope. Finally, MnO nanospheres encapsulated in carbon (MnO@C) composites were synthesized through a one-step solid state reaction, and they could be converted into regular MnO2nanorods through a simple subsequent annealing process. The main research contents are listed as follows:1. We syn thes i zed200-700nm sized Li CoO2particles via a sol-gel method. And employed the reaction of Cu(NO3)2and NaOH in the room temperature to coate the surface of LiCoO2with Cu(OH)2, which is then decomposited to CuO. When the amount of CuO is2wt.%,50nm sized CuO particle were distributed uniformly on the surface of LiCoO2. In the condition of3-4.5V,1C, the capacity of2wt.%CuO coated LiCoO2was155mAhg-1, corresponding to a retention was97%. But the capacity of uncoated LiCoO2faded rapidly t110mAhg-1(retention was68%). The electrochemistry impedance spectroscopy analysis revealed that CuO coating played a important role in decreasing the resistance of cell. The cyclic voltammograms result indicated that CuO coated sample reduced the polarization and improved the electrochemical activity of cathode. In addition, the2wt.%CuO coated LiCoO2performed well at high rates (10-50C). It supplied159.3mAhg-1at10C and hoded96.6%after10cycles; when the rate was50C (6850mAg-1), the charging time only needed1.2min, it still had123.1mAhg-1, and hoded76.9%after10cycles. Compared with the reports, the CuO coated LiCoO2performed excel lently at high rates. This work was published in Electrochimica Acta.2. Cu is widely used in electronics, catalysts, resins, thermal conductivities, but, it is easily oxidized by O2, especially on a nanoscale or microscale. Empolying a coating shell on Cu is a effective methode to isolate Cu from external harsh environments. We utilized the reduction and carbonization of glucose to synthesize Cu-core@C-shell composite via a one-pot hydrothermal process. The thermal stability analysis revealed that Cu was not oxided under325℃, and we did not find oxides of Cu even the composites was exposed to air, these indicated that the carbon shell could prevent oxidation of Cu to some extent. In adiition, when the convergent electron beams in a TEM irradiated the composite, the amount of interior copper gradually dwindled and some of it rushed out to form lots of30nm sized Cu particles. The composite might possess potential applications as a sensitive detector and the "transfer station" of Cu. This work was published in Langmuir.3. MnO@C composites were synthesized through a one-step solid state reaction. The detailed structure is that MnO nanospheres encapsulated in carbon curvy plates. And, the composites could be translated into MnO2nanorods, whose diameters were100-300nm and length were2.5um. We researched the growth mechanism of the MnO@C and MnO2nanorodes through observing the samples under different reaction time in TEM. The result indicated that MnO@C curvy plates were from the fracture of honeycomb intermediates. And the MnO2nanorods were translated from unregular particles. This work was published in Journal of Alloys and Compounds.
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