Zhang Yunshi

Cyclic voltammetric studies of stabilized α-nickel hydroxide electrode

Abstract Substitution of aluminum for nickel in the lattice of nickel hydroxide, prepared by co-precipitation, leads to hydrofalcite-like compound of α-nickel hydroxide. This compound has been used as the electrochemical active material in the positive electrodes of rechargeable alkaline batteries. Cyclic voltammetric studies suggest that α-nickel hydroxide displays better reversibility of the Ni(OH) 2 /NiOOH redox couple. The mechanism of the electrode reaction is still found to be controlled by proton diffusion, and the proton diffusion coefficient differs with the content of aluminium.

Electrochemical studies of aluminum substituted α-Ni(OH)2 electrodes

Abstract Stabilized α -Ni(OH) 2 was used as an active material of pasted positive electrode in Ni/MH battery. Electrochemical properties such as discharge capacity and discharge potential were improved. Cyclic voltammetric studies indicated that α -Ni(OH) 2 electrode exhibited a better reversibility of Ni(OH) 2 /NiOOH redox reaction and higher oxygen evolution overpotential than β -Ni(OH) 2 electrode. This apparently would increase the charge efficiency, improve utilization of active material and minimize concurrent oxygen evolution.

Characteristics of novel Co-free MlNi4.2−xCu0.5Al0.3Znx (0<x<0.1) hydrogen storage alloys

Abstract The mischmetal-nickel-based hydrogen storage alloys MlNi 4.2− x Cu 0.5 Al 0.3 Zn x (Ml=La-rich mischmetal, 0 x

Surface analysis of a TiNiB hydrogen storage electrode

Abstract A TiNiB hydrogen storage alloy electrode was prepared by powder metallurgy. Using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), the chemical state and composition of the electrode surface were analysed before and after electrochemical charge-discharge cycles. The constituent elements on the surface existed as oxides or hydroxides. Titanium and boron segregated to the surface, especially boron. At a depth of about 300 A, the alloy bulk concentration was reached. The oxidized surface layer became thicker and the segregation of titanium and boron to the surface gradually increased during cycling. The preferential segregation to the surface was probably induced by chemical reaction. The oxidation and segregation of titanium were main reasons leading to the decrease in capacity of the electrode.

The characteristics of the microencapsulated TiNi alloys and their electrodes

Abstract In this work, we prepared TiNi and Ti 2 Ni alloys by sintering and melting and then microencapsulated the alloy powder with nickel or copper. The electrochemical capacities and cycle lives of all the alloys were determined; the influences of nickel content on capacity were also studied.

Nickel/metal hydride batteries using microencapsulated hydrogen storage alloy

Abstract Fine particles of MmNi5(Mm: abbreviation for mischmetal) multicomponent hydrogen storage alloys were encapsulated with a thin layer of nickel about 0.5 μm thick using a special chemical plating method. With the alloy as an anode material, metal hydride electrodes and sealed nickel/metal hydride ( Ni MH ) batteries of AA size were made. The electrode has a higher discharge capacity and a longer cycle life than that using the bare (uncoated) alloy. A battery discharge capacity of 1200 mAh is obtained, which is equivalent to 60 Wh kg−1 (180 Wh 1−1). After 1000 complete charge-discharge cycles, the battery capacity is only reduced by 5%. SEM analysis, X-ray diffraction patterns and corrosion measurement are used to show how the microencapsulation of the alloy is effective in improving the performance of the battery.

Characteristics of titanium-based C14-type Laves phase alloys and their hydride electrodes

Abstract The pressure-composition-temperature (PCT) isotherms, lattice parameters and electrode properties of titanium-based Laves phase alloys with various compositions were studied in this work. The as-cast pseudobinary Ti 1-x Zr x Fe 0.15 Mn 1.21-y V 0.64 Ni y alloys ( x = 0–0.2, y = 0–0.6) were found to have the same crystal structure of the C14-type Laves phase by analysis of X-ray diffraction patterns. The equilibrium characteristics of their hydrides obtained by measuring PCT isotherms at 30 °C were attributed to both geometric and electronic factors. The electrode properties of the hydrides were dependent on both the plateau pressure of the PCT curves and the electrocatalytic activity of their alloys.

Characteristics of the stoichiometric and non-stoichiometric Laves phase alloys and their hydride electrodes

The pressure-composition isotherms, lattice parameters and electrode properties of the stoichiometric and non-stoichiometric C14 Laves phase alloys with various compositions were studied in this work. The flatness of the plateau pressure of the stoichiometric alloys with vanadium was inferior; however the flatness of the non-stoichiometric alloys on adding manganese improved for the Ti1−xZrxFe0.15Mn0.21+yV0.64Ni1.0 (x = 0.2–0.4, y = 0–0.4) system. The changes in the hydrogen plateau pressure and flatness of the plateau pressure were attributed to the geometric factor and affinity of environmental elements of the tetrahedral interstices hydrogen occupation. The electrode properties of all alloys studied were dependent on the hydrogen plateau pressure and flatness of the plateau pressure of the alloy.

Accumulation of rare-earth metal on the surface of the microencapsulated hydrogen storage alloy

The rare-earth metal of MmNi5-based alloys (Mm=mischmetal) can accumulate on some microencapsulated surfaces. The accumulation is selective and may be due to the different tendency of Mm in the alloy to accumulate on the various coated-metal layers.

Preparation of Amorphous Ti-Ni Films and Study on the Electrocatalytic Properties

The film electrodes of amorphous Ti o.ss Ni 1.00 and Ti 1.59 Ni 1.00 were prepared by means of ion beam sputtering method using TiNi and Ti 3 Ni alloy targets, respectively The surface microstructures and chemical states of elements of the two films before and after HF treatment were examined by SEM and XPS. The electrocatalytic properties for hydrogen evolution reaction were measured by the galvanost&tic steady-state method in 1M NaOH at 40°C. The results showed that the surface microstructures and compositions of the treated films obviously changed as compared with the untreated films. The electrocatalytic activities of the both films before treatment were lower, but the electrocatalytic activities and exchange current densities significantly increased after treatment.