Nickel positive electrode reaction

Oxygen evolution occurs on nickel oxide electrodes throughout charge, on overcharge, and on standby. It is the anodic process in the self-discharge reaction of the positive electrode in nickel-cadmium cells. Early work in the field has been reviewed [9], No significant new work has been reported in recent years. 

The ZEBRA cell shows the similar behavior during the charging reaction, in which the nickel is converted to nickel chloride within the reaction front. During the charging reaction the reaction front also moves from the / " -alumina into the positive electrode. 

Electrochemical Processes The charged positive electrodes of these batteries contain NiOOH, an oxide hydroxide of trivalent nickel, and the negative electrodes contain metallic cadmium or iron (M). As a rule, KOH solution serves as the electrolyte. The main current-producing reactions on the electrodes and in the cell in general can be written as... 

The processes taking place on the positive electrode actually are more comph-cated. Several modifications of nickel oxides exist which in particular differ in their degrees of hydration, so the equations above do not correctly describe the water balance in the reaction. The hydroxide of divalent nickel is formed as p-Ni(OH)2 and... 

The main cell reaction involves chlorination of high surface area nickel powder with sodium chloride to form the nickel chloride positive electrode and sodium ... 

Edison cell — A nickel-iron (Ni-Fe) secondary (rechargeable) cell independently developed by Edison in USA and W. Jiinger in Sweden in 1900. The cell (-> battery) is based on the use of nickel oxyhydroxide (NiOOH) at the positive electrode and metallic iron for the negative electrode, and a potassium hydroxide (KOH) solution containing lithium hydroxide (LiOH) is the electrolyte. The Ni-Fe cell is represented as ( Fe/KOH/NiOOH. The charge-discharge reactions for the Edison (Ni-Fe) cell are as follows ... 

Ni-Cd cells — The nickel-cadmium cell is a secondary - battery that has a nominal cell potential of 1.20-1.25 V. The negative electrode comprises nickel hydroxide-nickel oxyhydroxide, the positive electrode is cadmium, and the electrolyte solution is based on aqueous potassium hydroxide (KOH, 32% in water). At the anode, the discharge reaction is the oxidation of cadmium metal to cadmium hydroxide with the release of two electrons [i] ... 

Ni-MH cell — A -> secondary battery (-> accumulator) containing a nickel hydroxide positive electrode, a metal hydride negative electrode, and a strongly alkaline aqueous electrolyte solution. The electrode reactions are... 

Some of the more exotic electrode materials are nickel coated with manganese, tungsten or ruthenium oxides for positive electrodes. These metals give quicker action for the part of the reaction that occurs at the positive electrode. Nickel plated platinum can be used on the negative... 

Nickel-cadmium batteries use a hydrate nickel oxide as positive electrode, a metallic cadmium as negative electrode and an aqueous solution of potassium hydroxide as electrolyte [17]. The production of electrons at the negative plate during discharge occurs via the following semi-reaction ... 

The redox reaction of nickel hydroxide and nickel oxide hydroxide, the electrochemi-cally active compounds at the positive electrode of a nickel battery, was investigated. The thermodynamics of non-ideal solid solutions were applied to the reversible potential as a function of the state-of-discharge. In a temperature range 5 to 55°C two parameter activity coefficient models perform significantly better than one parameter models. 

By operating at about 650 °C, the kinetics of the oxygen reduction reaction at the positive electrode are sufficiently accelerated that it is no longer necessary to use platinum-based electrocatalysts. Usually, the positive electrode is fabricated from lithiated nickel oxide (Li Nii 0, where 0.02[Pg.211]

A Ni-H2 ceU may be viewed as a hybrid of the alkaline Ni-Cd ceU with the alkaline hydrogen-oxygen fuel cdl. Simply, the hydrogen electrode from the fud ceU is combined with the nickel oxide positive electrode from the Ni-Cd ceU, thus forming a battery system with two of the most reversible dectrodes. OveraU, the reaction within the Ni-H2 ceU is ... 

The positive electrode, the cathode, is similar to that in nicad cells and consists of a mixture of NiO(OH)/Ni(OH)3 and Ni(OH)2. An alloy that supports hydride formation replaces the cadmium as the negative anode. The alloy most commonly used is derived from LaNis, in which a mixture of other lanthanides replaces the lanthanum, and a nickel-rich alloy replaces the nickel, to give a general formula LnA/5. The anode is composed of an agglomeration of alloy powder. A small amount of potassium hydroxide is added as an electrolyte. The cell voltage is 1.3 V, making these cells suitable for the direct replacement of nicad batteries. The cell construction is identical to that of the nicad cell (Figure 9.10), with the cadmium replaced by metal hydride. The approximate cell reactions are as follows. 

As described in the relevant report, the tert-aUcylbenzene compound decomposes by oxidation at a potential of +4.6 to +5.0 V (relative value to that of lithium), and cobalt or nickel in the positive electrode rapidly dissolves and deposits on the negative electrode to inhibit a reaction of a carbonate in the non-aqueous electrolytic solution with a lithium metal deposited on the negative electrode. Further, in the invention, the internal short circuit may be formed in the battery by the deposition of cobalt and nickel, whereby the overcharge inhibitive effect can be attained and the safety of battery can be assured [133]. 

The ZEBRA cell, which is under development by the General Electric Co., uses a molten-sodium anode and a solid p,p"-alumina solid electrolyte as in the sodium-sulfur cell, but the positive electrode is large-surface-area nickel rather than molten sulfur with a large-surface-area current collector. The electrolyte on the cathode side of the ZEBRA solid electrolyte is an aqueous NaAlCLt containing NaCl and Nal as well as a little FeS. The FeS and Nal are added to limit growth of the Ni particles and to aid the overall cathode reaction, which is... 

The electrodes are referred to as anode and cathode in battery assembly. Anode is the positive electrode that is normally oxidized, ie, loses electrons in a chemical reaction within the cell. An anode should be an efficient reducing agent with good conductivity. Metallic materials such as zinc, nickel, and lithium are often used as anode materials. Cathode is the negative electrode, normally a metal oxide or sulfide, that is reduced or gains electrons. The main properties of a cathode material are that it should be an efficient oxidizing agent and should be stable when it comes into contact with electrolytes. 

The basic electrochemistry of the Ni-Cd battery was given in Table IIJ once again, however, the equations are misleading in that the reactions are not nearly as simple as indicated particularly at the positive electrode. In the nickel oxide paste, the oxidation state of the oxidized nickel species is uncertain and varies between - 2 and h-4 both the oxidized and reduced species exist in several crystal modifications and the important roles of water and potassium ions arc not included in the table. 

Nickel hydroxide is a layered oxide that has been studied as a positive electrode material. The desired structure is called turbostratic or a-Ni(OH)2, which has a higher theoretical capacity than j8-Ni(OH)2. One way to obtain the desired phase is to add 2 M ammonium hydroxide to 1 M NiS04 6H2O at pH 10 with ultrasonics (Xia, 2002). Washing with water and ethanol after reaction is important to maintain the a-phase (Cheng, 2001 Faure, 1991). Especially when the resulting powder is nanoscale, the amount of active material is increased and the depth of discharge is improved. 

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