Cell reactions nickel cadmium

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] ... 

The average cell voltage of 1.2 V is slightly lower than that of the Edison cell. Cadmium is preferred to iron in the nickel-aUcaline cell because cadmium hydroxide is more conductive than iron hydroxide. The absence of higher oxidation states for cadmium minimizes side reactions, which occur in the Edison cell. The nickel-cadmium cell can also be charged at a lower voltage since there is no overvoltage, as there is at the iron electrode. 

Storage cell. The nickel-cadmium storage cell has recently come into use. The reactions are complex, involving mixed oxidation states of Ni, but the discharge process may be represented approximately by... 

When these two half-eell reactions occur (by connection of the electrodes to an external discharge circuit), the overall cell reaction converts cadmium to cadmium hydroxide at the anode and nickel oxyhydroxide to nickel hydroxide at the cathode,... 

The overcharge reactions for the cell are the same as for nickel—cadmium and nickel—hydrogen cells. The oxygen generated on the nickel electrode at the end of charge and overcharge finds its way to the anode and reacts to form water in the Ni—H2 case and Cd(OH)2 in the Ni—Cd case. 

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. 

Many types of rechargeable batteries are much more portable than a car battery. For example, there is now a rechargeable version of the alkaline battery. Another example, shown in Figure 11.20, is the rechargeable nickel-cadmium (nicad) battery. Figure 11.21 shows a nickel-cadmium cell, which has a potential of about 1.4 V. A typical nicad battery contains three cells in series to produce a suitable voltage for electronic devices. When the cells in a nicad battery operate as galvanic cells, the half-reactions and the overall cell reaction are as follows. 

Nickel(lll) oxide, prepared from a nickel(ii) salt and sodium hypochlorite, is used for the oxidation of alkanols in aqueous alkali [46]. Residual nickel(Ii) oxide can be re-activated by reaction with sodium hypochlorite. Nickel oxides have also long been used in the manufacture of the positive pole in the Edison nickel-iron rechargeable battery, now largely superseded by die lead-acid accumulator, and in the Jungner nickel-cadmium batteries used as button cells for calculators [47]. Here, prepared nickel oxide is pressed into a holding plate of perforated nickel. Such prepared plates of nickel(lli) oxide have been proposed as reagent for the oxidation, in alkaline solution, of secondary alcohols to ketones and primary alcohols to carboxylic acids [48]. Used plates can be regenerated by anodic oxidation. 

The reaction at the positive is the same as that in the nickel-cadmium cell ... 

As in the nickel-cadmium cell, the electrolyte is concentrated potassium hydroxide. Depending on the metal alloy used, the emf has a value usually in the range 1.32-1.35 V, which turns out to be almost the same as that of the nickcl-cadmium cell. Note that the electrolyte composition is completely invariant during cycling. Unlike the situation with the nickel-cadmium cell, water is not involved in the cell reaction. 

Nickel-cadmium, or "ni-cad," batteries are popular for use in calculators and portable power tools because, unlike most other dry-cell batteries, they are rechargeable (Figure 18.11). The anode of a ni-cad battery is cadmium metal, and the cathode is the nickel(III) compound NiO(OH) supported on nickel metal. The electrode reactions are... 

The rechargeable nickel-cadmium (Ni-Cad) batteries are used in a variety of cordless appliances such as telephones, battery operated tools, and portable computers. During discharge, cadmium metal (Cd) acts as the anode, and nickel dioxide (Ni02) as the cathode. Both metals form insoluble hydroxides due to the presence of the potassium hydroxide electrolyte. The cell reaction during discharge is... 

Lead-acid, nickel-iron (Ni-Fe), nickel-cadmium (NiCd), and nickel-metal hydride (NiMH) batteries are the most important examples of batteries with aqueous electrolytes. In lead-acid batteries, the overall electrochemical reaction upon discharge consists of a comproportionation of Pb° and Pb4+ to Pb2+. All nickel-containing battery reactions are based on the same cathodic reduction of Ni3+ to Ni2+, but utilize different anodic reactions providing the electrons. Owing to toxicity and environmental concerns, the formerly widely used Cd°/Cd2+ couple (NiCd cells) has been almost entirely replaced by H/H+, with the hydrogen being stored in a special intermetallic compound (NiMH). 

E) Nickel-Cadmium (NiCd or "nicad") secondary (rechargeable) cell, invented by Jugner86 in 1899, uses nickel oxyhydroxide NiO(OH) and Cd metal as electrodes in the discharge mode the cell reaction is... 

An especially important type of dry cell is the nickel-cadmium battery, in which the electrode reactions are as follows ... 

The overall reaction and standard cell potential at 25°C for the rechargeable nickel-cadmium alkaline battery is... 

The nickel-cadmium battery is the most popular alkaline secondary battery. The cell and its reaction are ... 

Combining the nickel cadmium and nickel-hydrogen systems technologies has given rise to the nickel-metal hydride rechargeable battery, one of the most advanced rechargeable systems commercially available and an environmentally friendlier alternative to nickel-cadmium batteries. The cell and its reaction may be written ... 

The nickel-cadmium cell (or nicad battery Fig. 17.8) is used in handheld electronic calculators and other cordless electric implements such as portable shavers. Its half-cell reactions during discharge are... 

Rechargeable batteries have become an essential part of our environmentally conscientious society. The nickel-cadmium cell battery is a rechargeable battery used in small electronic devices. The half reactions that take place in the nickel-cadmium battery during discharge are ... 

Leclanche cells are not rechargeable once the reactants are depleted, the battery must be discarded and replaced. Batteries that are not rechargeable are called primary batteries. A rechargeable battery is called a secondary battery or a storage battery. The nickel-cadmium (NiCd) battery is a popular rechargeable battery that uses the following redox reaction ... 

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