TiO2-coated LiNi1/3Co1/3Mn1/3O2 materials were prepared by the hydrolyzation of Ti(OBu)4. The impact of TiO2 coating on the structure and electrochemical properties of LiNi1/3Co1/3Mn1/3O2 was investigated using X-ray diffraction, scanning electron microscope, and charge–discharge tests. The results indicated that TiO2 coating did not affect the lattice of LiNi1/3Co1/3Mn1/3O2, but exhibited obvious effects on its discharge capacity and cycling stability. As coated TiO2 increased from 0.0 to 2.0 mol%, the initial capacity of samples decreased slightly, but the cycling stability over 2.5∼4.3 V increased remarkably. The capacity retention reached 99.5% at the 50th cycle at a coating amount of 2.0 mol%. 相似文献
A novel process was proposed to synthesize the pyrolytic polyacrylonitrile (PAN)/SnCl2 composite anode material for Li-ion batteries. The preparation started with the dissolution of PAN and SnCl2 in dimethylformamide (DMF), followed by drying of the solution and pyrolysis of the dried mixture of PAN and SnCl2 at 300 °C, leading to homogenous dispersal of SnCl2 in pyrolytic PAN, which becomes conducting polymer matrix. The composite presented stable cycling capacity of about 490 mAh/g. It is demonstrated that SnCl2, which has been considered to be an inactive electrode material, can become active by the proposed composite technique. This paves the promising way to prepare electrode materials for Li-ion batteries. 相似文献
Metal oxide additives are added into LiFePO4 electrodes attempting to improve cell power performances. Electrochemical performances are tested with 5 wt% different sizes of neutral alumina, nano Al2O3, and nano MgO individually comparing with those with 5 wt% more active LiFePO4 and acetylene black. The polarization between charge and discharge plateaus is reduced not only by adding more conductive acetylene black, but also by adding all these insulated metal oxide additives. Adding natural alumina and nano MgO can significantly increase rate capacities. This might be because of their “lithium ion saver” effect. 相似文献
A wide range of symmetrical and unsymmetrical glycosyl disulfides is synthesized with focus on the use of α-glycosyl thiols. Oxidation of α-glycosyl thiols with iodine leads to symmetrical α,α-glycosyl disulfides, while unsymmetrical disulfides are readily synthesized from α- and β-glycosyl thiols under the action of DDQ. Thus, glycosyl disulfides containing at least one α-glycosidic linkage are made available. 相似文献
Meeting the demand for sugars : The importance of oligosaccharides and glycoconjugates in biological systems has stimulated a need to access significant amounts of these compounds. Much effort has been devoted to the stereoselective generation of the key glycosidic bond, both between carbohydrate residues (see scheme) and to the aglycone. Various methodologies are now available for the efficient synthesis of structurally defined complex oligosaccharides and glycoconjugates.
Recent developments in the direct observation of J couplings across hydrogen bonds in proteins and nucleic acids provide additional information for structure and function studies of these molecules by NMR spectroscopy. A JNN-correlated [15N, 1H] TROSY experiment proposed by Pervushin et al. (Proc. Natl. Acad. Sci. USA 95, 14147–14151, 1998) can be applied to measure hJHN in smaller nucleic acids in an E.COSY manner. However, it cannot be effectively applied to large nucleic acids, such as tRNATrp, since one of the peaks corresponding to a fast relaxing component will be too weak to be observed in the spectra of large molecules. In this Communication, we proposed a modified JNN-correlated [15N, 1H] TROSY experiment which enables direct measurement of hJHN in large nucleic acids. 相似文献