Nickel Sulfide Phase Research Articles

Charge–discharge mechanism of mechanically alloyed NiS used as a cathode in rechargeable lithium batteries

Nickel sulfide (NiS) as a cathode material for a lithium rechargeable battery was charged and discharged at elevated temperature (80 °C) using a PEO solid polymer electrolyte. In order to synthesize a homogeneous NiS phase, very fine nickel metal powder was ball milled with sulfur powder for 12 h under argon gas. We found using ex-situ XRD measurements that the NiS cathode active material was transformed into other phases such as Ni 3S 2, nickel and sulfur during discharge. The initial discharge capacity of the NiS positive electrode was 580 mAh/g NiS at 1.5 V vs. Li/Li + with PEO electrolyte. It has good cycling properties, retaining 93% of the initial discharge capacity even after 200 cycles with a PEO solid polymer electrolyte.

Nickel sulfide synthesized by ball milling as an attractive cathode material for rechargeable lithium batteries

Nickel sulfide (NiS) powders were prepared by ball milling and melting as cathode materials for a lithium rechargeable battery which was charged and discharged at room temperature (30 °C). The NiS powders prepared by melting were composed of several phases such as Ni 3S 2, Ni 7S 6, Ni x S 6, and Ni 3S 4, as derived from XRD. In order to synthesize a homogeneous nickel sulfide (NiS) phase, ball milling (BM) was adopted. A homogeneous NiS phase was easily formed after ball milling up to 12 h under an Ar atmosphere. The ball milled NiS particles were relatively large compared to those of the starting materials and they had a nanocrystalline structure. The initial discharge capacity of the NiS positive electrode prepared by ball milling is 580 mAh/g-NiS, at 1.4 V vs. Li/Li +. The NiS powders synthesized by ball milling show a better cycling property than NiS prepared by melting and also had a better rate capability. It exhibited 87% of its theoretical capacity at a current rate of 2C, comparable with that of 1/6C. This may be related with the small sized grains of NiS prepared by ball milling.

Electrochemical properties of NiS as a cathode material for rechargeable lithium batteries prepared by mechanical alloying

Nickel sulfide (NiS) as a cathode material for a lithium rechargeable battery is charged and discharged at room temperature (30 °C). In order to synthesize a homogeneous NiS phase, mechanical alloying (MA) was adopted. The homogeneous NiS phase is easily formed after ball milling for 12 h under Ar atmosphere. The ball-milled NiS particles are relatively larger than those of the starting materials and have a nanocrystalline structure. The initial discharge capacity of the NiS positive electrode is 580 mAh/g-NiS, at 1.4 V versus Li/Li +. The NiS powders synthesized by MA show proper cycling properties, by retaining 65% of the initial discharge capacity even after 100 cycles at 30 °C. Also, NiS has a good rate capability. It has 87% of its theoretical capacity at a current rate of 2 C, comparable with that of 1/6 C.

In situ TEM observation of nickel promoted WS 2 thin-film crystallization

In the present study, the crystallization of amorphous Ni/WS 3+ X (0< X<2) thin films is observed in real time during an in situ annealing of the thin-film samples in a transmission electron microscope. The obtained results make possible for the first time the development of a consistent growth model for promoted WS 2 thin-film growth. In this model, the nickel film reacts with the excess sulfur in the amorphous WS 3+ X film to form large NiS X drops, which are liquid at the annealing temperature of 800°C. Small WS 2 crystallites, which are in contact with the liquid nickel sulfide phase, are dissolved in the melt. At the same time, large WS 2 crystallites grow laterally from this saturated solution.

HDS Activity and Characterization of Zeolite-Supported Nickel Sulfide Catalysts

Catalysts of nickel sulfide supported on zeolite Y have been prepared (by impregnation or ion exchange) and characterized by means of thiophene hydrodesulfurization (HDS), sulfur analysis, temperature-programmed sulfiding, 129Xe-NMR, HREM and dynamic oxygen chemisorption. The catalysts show large differences in catalytic behavior dependent on the preparation method (impregnation vs ion exchange) and the pretreatment conditions (method of sulfidation). Especially the ion-exchanged catalysts show a high initial activity, but due to the presence of acid sites deactivation is very strong. The initial activity of these catalysts can be improved significantly by drying prior to sulfidation. In all cases sulfidation results in quantitative formation of nickel sulfide, with Ni3S2 being the main product. Occasionally, also some NiS appears to be present. The major part of the nickel sulfide phase is invariably located on the outside of the zeolite particles. The fraction of nickel sulfide in the zeolite pores depends on the preparation method and the pretreatment conditions. The differences in catalytic activity are ascribed not only to variations in overall nickel sulfide dispersion but also to the acidity of the support, and the presence of very active small nickel sulfide clusters in the pores of the zeolite can have a strong influence on the thiophene HDS activity.

Microstructural and Microchemical Characterization of Nickel Sulfide Inclusions in Plate Glass

Nickel sulfide inclusions have been implicated in the spontaneous fracture of large windows of tempered plate glass. Two alternative explanations for the fracture-initiating behaviour of these inclusions have been proposed: (1) the volume increase which accompanies the α to β phase transformation in stoichiometric NiS, and (2) the thermal expansion mismatch between the nickel sulfide phases and the glass matrix. The microstructure and microchemistry of the small inclusions (80 to 250 μm spheres), needed to determine the cause of fracture, have not been well characterized hitherto. The aim of this communication is to report a detailed TEM and EDS study of the inclusions.

Redox‐Controlled Solubility of Palladium in a Borosilicate Glass Melt

Palladium establishes the Pd2+–Pd0 redox equilibrium in a reference alkali borosilicate melt. Most of the palladium exists as the insoluble metal, with only a small fraction of the palladium present as the divalent palladium ion dissolved in the melt. The relative reduction potential of this Pd2+–Pd0 redox couple in the reference glass melt is greater than such easily reduced couples as Ni3+–Ni2+ and Mn3+–Mn2+. Palladium metal in glass melts containing appropriate amounts of nickel and sulfur readily partitions into an immiscible nickel sulfide phase; palladium also tends to associate with tellurium in insoluble particulates.

EMF Measurements on the Li ‐ Al / Ni3 S 2 Couple in Molten Salt Electrolytes

The (emf) vs. temperature curve for the couple was determined in (eutectic electrolyte), , , and in electrolyte. The results indicate that with these electrolytes the emf value of the couple at a given temperature is independent of the electrolyte composition. Equilibrium emf values were obtained instantaneously upon heating or cooling at rates of ∼0.2°C/min, while at higher rates (∼0.5°C/min) equilibrium values were obtained after at a given temperature. X‐ray diffraction analyses of the positive electrodes from the cells tested indicate that the only nickel‐sulfur phase formed in the electrode reaction is . Thermochemical analyses also suggest as the active nickel sulfide phase.