Nickel Hydroxide Powder Research Articles

電池材料 Ｎｉ水素電池用高性能片状金属粉とそれを用いた電極作製技術の開発

New flake-like metal powder such as copper, nickel, nickel alloy and nickel-cobalt composite, which could provide good electrical conductivity and binding ability were developed as new electrode producing materials. A mixture of hydrogen storage alloy powder for metal hydride electrode or nickel hydroxide powder for nickel electrode with the flake-like metal powder was roll-pressed on a nickel-mesh substrate without polymeric binder and a formed nickel substrate. A laminated network structure of the flake-like metal powder was formed to connect tightly hydrogen storage alloy powder or nickel hydroxide powder in the electrode. The flake-like metal powder provided higher discharge capacity (utilization efficiency) and higher mechanical strength for the electrodes than a conventional powder.

Nickel Hydroxide as an Active Material for the Positive Electrode in Rechargeable Alkaline Batteries

Spherical nickel hydroxide powders coprecipitated with the additives , , and were prepared through a spraying technique. These powders, which have a higher tapping density and a much smaller pore volume and crystalline size than conventional powders, were used as the active materials of nickel hydroxide electrodes. The effects of the , , and additions on electrode properties such as charge‐discharge, reversibility of the electrode reaction, and cycle life, were studied. The relationship between the electrode swelling and the formation of γ‐NiOOH was also investigated. The results show that nickel hydroxide powders having a smaller crystallite size show better electrode characteristics such as lower overpotential, higher plateau discharge potential, and higher capacity. The utilization of the active material in the electrodes illustrates that for general use it is better to add , while for a wider temperature range, it would be better to consider the addition of . The cycle life of the electrode containing was improved obviously because there was less electrode swelling due to much reduced formation of γ‐NiOOH. © 1999 The Electrochemical Society. All rights reserved.

Effects of surface modification of nickel hydroxide powder on the electrode performance of nickel/metal hydride batteries

Our experimental results show that the electrodeposition of nickel on the surface of nickel hydroxide particles can increase greatly the conductivity of the nickel hydroxide electrode. Consequently, the capacity of the electrode is significantly increased. However, there is an optimal point in terms of the amount of deposited nickel. Insufficient nickel would not provide enough conductivity since nickel hydroxide is spontaneously formed and coated on the nickel surface in KOH electrolytes. Excessive deposited nickel, on the other hand, would lead to an increase of charge transfer resistance and decrease of the electrode capacity. The optimal amount of deposited nickel was found to be around 11 wt%, resulting in the electrode capacity approaching 236 mAh/g Ni(OH) 2 and utilization of active material approaching 82%. In addition, in comparison with electrodes without deposited Ni but containing cobalt oxide, the charge efficiency for the electrode with the nickel coating at elevated temperature was found to be superior.

The effect of Zn(OH)2 addition on the electrode properties of nickel hydroxide electrodes

Nickel hydroxide powders currently used in the positive electrode of nickel-metal hydride (Ni–MH) batteries require cobalt or cobalt oxides to make them viable and attractive. As a step to eliminate the cobalt-containing materials, spherical nickel hydroxide powders coprecipitated with Zn(OH)2 were prepared by a spraying technique. These powders, which have a higher tapping density and a much smaller pore volume than conventional powders, were used as the active materials of nickel hydroxide electrodes. The effects of the Zn(OH)2 additions on the electrode properties, such as percentage utilization and cycle life, were studied, and the relationship between the electrode performance and the formation of γ–NiOOH was investigated. The cycle life was increased because there was less electrode swelling due to much reduced formation of γ–NiOOH.

ChemInform Abstract: Synthesis of Nickel Hydroxide Powders by Urea Decomposition.

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Thermodynamic studies of cobalt and cadmium additions to nickel hydroxide as material for positive electrodes

Abstract Nickel oxide is used as the positive electrode in nickel–cadmium and nickel–metal-hydride batteries. The physical and the electrochemical effects due to the addition of cobalt and cadmium to nickel hydroxide powders are investigated. X-ray diffraction analysis shows that the d 001 value (interlayer distance in the nickel hydroxide) decreases with increase in cobalt content, while the d 100 value increases with increase in cadmium content. The open-circuit potential in discharge follows an S-shaped curve in 3 M KOH electrolyte. The results are discussed with respect to thermodynamic theory. The experimentally obtained OCP variation is in good agreement with calculated data using thermodynamic theory with one fitting parameter, φ / RT ; φ is an interaction energy parameter (J mol −1 ) and RT is the product of the gas constant and absolute temperature. The φ / RT and E 0 (standard electrode potential) values are found to decrease with increase in cobalt content, while the addition of cadmium has little effect on the φ / RT and E 0 values. A difference between the OCP data and the calculated value occurs at the end of discharge; this difference tends to increase with increase in cobalt content.

Synthesis of nickel hydroxide powders by urea decomposition

Synthesis of nickel hydroxide from aqueous solutions by decomposition of urea was investigated. Spherical agglomerates of nanocrystalline particles were obtained. Precipitated powders show turbostratic α-phase with significant carbonate intercalated into the structure. Addition of dispersant HPMC increases the specific surface area and reduces the median agglomerate size, whereas increase in aging time increases the precipitation yield considerably.

Electrochemical and thermodynamic studies of nickel electrodes in alkaline electrolytes

The nickel electrode is widely used as a positive electrode in rechargeable alkaline batteries. The electrochemical behaviour of nickel hydroxide powders in several kinds of electrolyte is investigated. The open-circuit voltage (OCV) of the nickel oxide electrode in 3 M KOH displays an S-shaped curve in the reduction process. On the other hand, the nickel oxide electrode in 3 M NaOH and 3 M LiOH shows two-step reduction OCV curves. In the first stage, the OCV curves are S-shaped, while in the second stage, the OCV curves are L-shaped. The S-shaped stage of the OCV curve is examined by using thermodynamic considerations. The thermodynamic simulation and experimental results are in fairly good agreement with one fitting parameter φ/RT; φ is an interaction energy parameter (J mol −1) and RT has the usual significance. The interaction energy parameter ( φ) is found to increase in the order 3 M LiOH < 3 M NaOH < 3 M KOH. This concluded that the alkaline cation intercalated into the nickel oxide lattice decreases the interaction energy parameter ( φ).

Structural defects and electrochemical reactivity of β-Ni(OH) 2

Electrochemical reactivities and structural properties of several nickel hydroxide powders were analysed by X-ray diffraction, Raman spectroscopy and extended X-ray absorption fine structure (EXAFS). It is shown that the electrochemical efficiency of β-Ni(OH) 2 is associated with the amount of proton vacancies included in the crystal lattice. The number of those proton vacancies increases when the crystallite size decreases or when the ratio of co-precipitated cobalt increases. Proton vacancies shift the oxidation potential of β-Ni(OH) 2 towards less anodic values and, therefore, improve the chargeability and the electrochemical efficiency of nickel hydroxide. It is shown that both Raman spectroscopy and X-ray diffraction techniques can be used to predict effectively the electrochemical efficiency of β-Ni(OH) 2 hydroxide. EXAFS results indicate also that the oxidation level of nickel atoms inside the hydroxide is not modified by the existence of proton vacancies. It means probably that to maintain the electroneutrality in the whole crystal induces others singularities. Finally, the influence of co-precipitated additives such as cadmium and cobalt on the rate of defects has been investigated.

Effect of cobalt addition to nickel hydroxide as a positive material for rechargeable alkaline batteries

Nickel hydroxide powder is used widely as an active material in pasted-type nickel electrodes. The effect on the electrochemical behaviour of cobalt addition (0.19–9.9 wt.%) to the nickel hydroxide powder is investigated. The physical properties of several nickel hydroxide powders containing different amounts of cobalt compound are examined by inductively coupled spectroscopy, laser diffraction, BET, X-ray diffraction and scanning electron microscopy measurements. The interlayer distance of the layered nickel hydroxide diminishes to a small value with increase in cobalt content. Moreover, the charge and discharge potentials of nickel hydroxide samples decrease with an increase in cobalt content. The chemical diffusion coefficients of the proton (D̄) in the nickel hydroxide samples with different amounts of cobalt are measured by a current-pulse relaxation technique. The D̄ and D 0 values increase with an increase in cobalt content, and the activation energy for proton diffusion is in the 0.20–0.33 eV range.

Effects of dopants on electrochemical performance of nickel cathodes

A paste-type electrode using spherical nickel hydroxide powder as the main active material and a foamed nickel grid as a current collector has been prepared. The effects of dopants such as cobalt, cadmium, zinc, copper and H-absorbing alloy on the electrode performance are examined. The most effective dopant and its optimum content is identified.

Physical and electrochemical characteristics of nickel hydroxide as a positive material for rechargeable alkaline batteries

Nickel hydroxide is widely used as an active material in pasted-type nickel electrodes. Physical properties of several nickel hydroxide powders have been examined by laser diffraction, BET, X-ray diffraction, thermal analysis and SEM. Nickel hydroxide powder with a smaller crystalline size shows better charge-discharge cyclic characteristics. The chemical diffusion coefficients of the proton in the nickel hydroxide sample are measured by a current pulse relaxation method. Nickel hydroxide with a smaller crystalline size shows a higher proton diffusion coefficient, giving excellent cycling behaviour.