Yanwei Li

Synthesis and electrochemical performance of α-nickel hydroxide codoped with Al3+ and Ca2+

Abstractα-Nickel hydroxide codoped with Al3+ and Ca2+ was prepared by chemical coprecipitation method. The phase structure and surface morphology of the prepared samples were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrochemical performances of the prepared samples were analyzed by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and charge/discharge tests. XRD and SEM tests reveal that the Al3+/Ca2+ codoped α-nickel hydroxide has a relatively good crystallization and a very coarse surface. Electrochemical tests show that the Al3+/Ca2+ codoped α-nickel hydroxide has higher proton diffusion coefficient, lower electrochemical reaction resistance, and higher discharge capacity (395.3xa0mAhxa0g−1 at 0.2xa0C) than the Al3+ singly doped α-nickel hydroxide, which indicates its potential application as an electrode material for secondary alkaline batteries.

Synthesis and Electrochemical Properties of Y-Doped LiNi1/3Mn1/3Co1/3O2 Cathode Materials for Li-Ion Battery

The layered Li(Ni1/3Co1/3Mn1/3)1-xYxO2 cathode materials (x = 0, 0.03, 0.06, 0.09) were prepared by a co-precipitation method. The properties of the Y-doped LiNi1/3Mn1/3Co1/3O2 were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. XRD studies show that the Y-doped LiNi1/3Mn1/3Co1/3O2 has the same layered structure as the undoped LiNi1/3Mn1/3Co1/3O2. SEM images exhibit that the particle size of Y-doped LiNi1/3Mn1/3Co1/3O2 is smaller than that of the undoped LiNi1/3Mn1/3Co1/3O2 and the smallest particle size is only about 2μm. The Y-doped LiNi1/3Mn1/3Co1/3O2 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra (EIS). The optimal doping content of Y is that x = 0.06 in the Li(Ni1/3Co1/3Mn1/3)1-xYxO2 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through Y-doping. The improved electrochemical performances of the Y-doped LiNi1/3Mn1/3Co1/3O2 cathode materials are attributed to the addition of Y3+ ion by stabilizing the layer structure.

Ab initio investigations on the geometric and electronic structures of a diblock molecular diode under the influence of an external bias

Theoretical investigations on the diblock molecular diode, thiophene–thiazole compound, have been carried out at the Hartree–Fock (HF) level by considering the interaction under the external bias. They demonstrate that the electronic structures of this kind of diode molecule are essentially different from those based on the Aviram and Ratner model, in which donor and acceptor π-conjugated segments are separated by an insulating σ-bonded segment, in terms of the energy levels of the frontier molecular orbitals as well as their spatial distributions. The introduction of the external bias modifies both the geometric and electronic structures. In particular, the spatial distributions of the frontier molecular orbitals are also shifted under the external bias. Moreover, all these features show a strong dependence on the polarity of the applied bias due to the build in intrinsic molecular asymmetric structures, which could be used to intuitively interpret the asymmetrical current–voltage behaviours of molecules.

Structure and Properties of the Copper Nitride Films Doped with Ti

Copper nitride (Cu3N) films were prepared by a reactive radio frequency magnetron sputtering apparatus. The surface morphology and microstructure of pure and Ti doped Cu3N films were characterized by atomic force microscope (AFM) and X-ray diffraction (XRD) technique. AFM images demonstrate that the pure Cu3N films has a smooth structure, while the films becomes compact after Ti doping. XRD tests indicate that the Ti atom is successfully doped in the Cu3N films. The lattice constant of the films decreases after Ti doping, and the texture direction of the films changes from (111) to (100) with the increase of Ti content. The optical transmission spectrum was obtained by ultraviolet-visible (UV-VIS) spectrophotometer. The optical band gap of the films ranges from 1.53 to 1.71eV. Four-probe method was employed to study the electric resistivity. The results show that both the pure and Ti-doped Cu3N films are semiconductor. Moreover, the optical band gap and electrical resistivity of the films increases with the increase of Ti content in the films.

Theoretical Investigation on the Electron Transport Behavior of Fe-Porphyrin Complexes

The electron transport behaviors of oxygen and carbon monoxide complexes of Fe-porphyrin (FeP) are investigated by nonequilibrium Greens function techniques combined with Density Functional Theory calculations. The results show that the molecular current of FeP decreases dramatically after adsorptions of oxygen and carbon monoxide. The molecular current decreases with a order of FeP > FeP+O2 complex > FeP+CO complex. This change of the molecular current after adsorption of oxygen or carbon monoxide can be potentially used to design a molecular sensor or a molecular switch.

Effect of Multi-Wall Carbon Nanotubes on the Electrochemical Performance of Al/Ca Codoped α-Nickel Hydroxide

The effect of multi-wall carbon nanotubes (MCNTs) addition on the electrochemical performance of Al/Ca codoped α-nickel hydroxide is studied. The microstructure and electrochemical performance of the prepared samples are characterized by XRD, SEM, electrochemical impedance spectroscopy, cyclic voltammetry, and charge-discharge tests. The results show that the addition of MCNTs could decrease the electrochemical reaction impedance dramatically, improve the electrochemical reaction reversibility, and increase the specific discharge capacity.