Layers nickel hydroxides

Layered nickel hydroxide can be used as an electrode for alkaline secondary cells. To improve its properties, modification has been carried out by incorporation of other metal elements to form Ni/M LDHs, including Co [221], Zn [222], Al [223], Cr or Mn [224] and Fe [225]. For example, Chen et al. reported the electrochemical performance of Al-substituted layered a-... 

SYNTHESES OF MDOED LAYERED NICKEL HYDROXIDE MANGANESE OXIDES BY HYDROTHERMAL INTERCALATION REACTION AND EXFOLIATION-RESTACKING HYDROTHERMAL REACTION... 

In acidic electrolytes only lead, because it forms passive layers on the active surfaces, has proven sufficiently chemically stable to produce durable storage batteries. In contrast, in alkaline medium there are several substances basically suitable as electrode materials nickel hydroxide, silver oxide, and manganese dioxide as positive active materials may be combined with zinc, cadmium, iron, or metal hydrides. In each case potassium hydroxide is the electrolyte, at a concentration — depending on battery systems and application — in the range of 1.15 - 1,45 gem"3. Several elec-... 

For the less reactive, longer n-alcanols the activation of the nickel hydroxide electrode is necessary (Table 3). For that purpose several layers of black nickel oxide hydroxide are deposited on the electrode surface from a buffered nickel sulfate solution by changing the electrode polarity every 5-10 sec n.isb,20,21)... 

The nickel hydroxide electrode is used since decades in the mckel-iron(Edison)-or nickel-cadmium(Jungner)-storage battery Here the anodes consist mainly of nickel oxide powder pressed into a support and current feeder, whilst for electro-organic oxidations and electroanalytical measurements a thin nickel oxide hydroxide layer on a nickel support is used. 

The lower amines have been oxidized in similar yields to nitriles at silver oxide and copper oxide anodes Activation of the electrode by deposition of a nickel hydroxide oxide layer is less essential than with alcohols due to the higher reactivity... 

The voluminous nickel hydroxide, that is produced from the oxidant, tends to adsorb organic compounds. This renders the isolation of the product sometimes difficult. In the electrolysis, however, the oxidant forms only a thin layer at the anode surface, which causes no problems in the work-up. 

The many varieties of practical nickel electrodes can be divided into two main categories. In the first, the active nickelous hydroxide is prepared in a separate chemical reactor and is subsequently blended, admixed, or layered with an electronically conductive material. This active material mixture is... 

It was as early as 1946 that de Lange and Yisser (1) published their finding that the precipitate formed on adding alkali hydroxide to a suspension of diatomaceous earth in a nickel salt solution is not merely a mixture of nickel hydroxide and diatomaceous earth, but that a reaction has taken place between the hitherto supposed inert carrier and the nickel compound. They ascertained the occurrence of such a reaction from the very great increase in accessible surface and the more difficult reduction of the reaction-product as compared with that of nickel hydroxide, and, on the basis of their X-ray work, suggested the formation of nickel hydrosilicates having a layer structure. Further, they assumed that after reduction... 

Since dehydration produces a change of color from light green for the hydroxide to yellowish green for the oxide, it has been possible to observe that decomposition does not take place simultaneously at the surface of all the particles in a thick layer ( 10 mm) of nickel hydroxide. On the contrary, a well-defined reaction interface moves downward in the powdered sample at a constant rate. It has been ascertained that the reaction rate is then proportional to the interface area and that the apparent reaction order for the dehydration process changes if the shape of the pan containing the reactants is modified (23). However, the... 

Nickel batteries use P-Ni(OH)2 as electrode material. This material converts to P-NiOOH during the charging process and this rearranges to y-NiOOH when it is overcharged. This last process is accompanied by a significant expansion, because of the difference in density between P-NiOOH and y-NiOOH, which may result in poor electric contact between the current collector and P-Ni(OH)2/p-NiOOH, with concomitant decrease in the discharge capacity of the battery. Among others, layered double hydroxides of Ni and other metals, often termed stabilized a-Ni(()H), or doped Ni(0H)2, have been tested as electrode materials (Bernard et al., 1996). The effect of the interlayer anions on the electrochemical performance of layered double hydroxide electrode materials has been recently studied by Lei et al. (2008) (see Chapter 6). 

Nickel electrodes are usually based on nickel hydroxides. Several forms of nickel hydroxides and oxyhydroxides are involved in the electrochemical process of nickel electrodes, which have been described in literature as a-Ni(0H)2i j8-Ni(OH)2. 7-Ni(0H)2, -NiOOH and y-NiOOH . The three divalent nickel hydroxides have different chemical compositions, but all of them have a lattice structure of alternate layers, differing in the relative spacing of hexagonal structure. The starting material for the formation of the alkaline electrode is the a-form hydroxide which is denoted as a-Ni(OH)2.xH2O,2 where x varies between 0.5 and 0.7. 

It can be obtained by the electrochemical precipitation of NiCNOjJj- water of hydration is an integral part of this compound and is believed to be responsible for the much larger distance between the hydroxide layers when compared to that in jS-Ni(0H)2, which does not contain water and is denoted as the brucite or C6-type structure. Another form of nickel hydroxide, known as the y-modification, can be prepared from concentrated KOH, leading to the incorporation of potassium ions into the lattice. The inclusion of K and other species as well can alter considerably the physicochemical properties of the otherwise pure... 

Lotmar and Feitknecht investigated variations in ionic distances of bivalent basic metal halogenides with layered structures of the Cdl2 type. In this context they needed the unit cell dimensions of nickel hydroxide as well as cobalt hydroxide. 

Cathodic electroprecipitation is a technique used commercially to prepare nickel hydroxide deposits in the battery field.25 In this case a nickel salt is present in solution at low pH (ca. 3.0) and hydrogen gas evolution around the cathode causes a local increase in pH, resulting in the precipitation of an adherent layer of nickel hydroxide at the metal surface. Similarly, anodic electroprecipitation is used commercially26 to produce layers of another highly active battery material, y-MnO2. 

More recent x-ray absorption studies of Co sorption complexes on quartz [77] suggest that for quartz at relatively low density coverage, first-sorbed Co species provide energetically favorable nucleation sites for the subsequent formation of multinuclear hydroxide-like surface complexes. This is also seen for Ni " " adsorbed onto silica [78] where the first species adsorbed are seen as nickel phyllosilicates and not hydroxides. Subsequent layers are either more nickel phyllosilicate or nickel hydroxide depending on the activity of the sdica. If the silica is more active, for example due to smaller particles or greater surface area, then more metal-sUicate species are formed either at the... 

Ion intercalation into nickel oxide is often performed in aqueous media. On immersion of nickel oxide into an alkaline solution, such as aqueous KOH, a spontaneous chemical conversion of NiO into a hydrous metal oxide phase Ni(OH)2 proceeds [25]. Hydrous NiO resembles V2O5 in respect to the two-dimensional layered host structure. The Ni(II)/Ni(III) couple responsible for the reversible color change on electrochemical cycling has been identified as the nickel hydroxide/oxy-hydroxide phases [25, 26]... 

Apostolova, R. D., Y. A. Tkachenko, O. V. Kolomoyets, and E. M. Shembel. 2012. Thin-layer electrolytic nickel hydroxide NifOFIJj in an electrochemical capacitor. Surface Engineering and Applied Electrochemistry 48 170—174. 

The terms supercapacitor and ultracapacitor are used to describe any double layer or redox capacitor with specific energy and specific power intermediate to batteries and traditional capacitors. Typically, ultracapacitor refers to a device comprised of two carbonaceous electrodes whereas supercapacitor refers to a similar device in which the two carbonaceous electrodes are catalyzed with metal oxides such as Ru02. This chapter will use the term supercapacitor to describe EAP-based capacitors, since that seems to be the most commonly used term for such materials. Another charge storage configuration uses an EAP electrode and a battery-type carbonaceous electrode in what is known as a hybrid device (however, outside of the EAP-based supercapacitor field, hybrid may refer to the combination of a battery electrode such as nickel hydroxide with a carbon electrode) [1]. 

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