Leclanche

Sheets of galvanised iron are used for roofing, guttering and the like. Alloys of zinc, notably brass, are used extensively. The metal is used m wet and dry Leclanche batteries. 

Salmiak, m. sal ammoniac (ammonium chloride). -clement, n. Elec.) sal ammoniac cell, Leclanch cell, -geist, m. aqueous ammonia, -kristall, m. (crystallized) sal ammoniac, -lakritze, /. sal ammoniac-licorice pastilles. -Idsung, /. ammonium chloride solution, -salz, n. sal volatile (ammonium carbonate) ... 

The zinc chloride cell, which was first patented in 1899, IS actually an adaptation of the Leclanche cell. The major innovation was the development of plastic seals that permitted the replacement of animoliitim chloride in the electrolyte. 

Cross-section of a Leclanche cell battery. (Gale Group, Inc.)... 

Leclanche or dry cell Alkaline Cell Silver-Zinc Reuben Cell Zinc-Air Fuel Cell Lithium Iodine Lithium-Sulfur Dioxide Lithium-Thionyl Chloride Lithium-Manganese Dioxide Lithium-Carbon Monofluoride... 

No gas is produced. The alkaline dry cell, although more expensive than the Leclanche cell, has a longer shelf life and provides more current. 

Le Chatelier s principle A relation stating that when a system at equilibrium is disturbed it responds in such a way as to partially counteract that change, 337-338 buffers and, 385 compression effects, 339-340 expansion effects, 339-340 precipitation equilibrium, 442 reaction conditions, 348q temperature changes, 340 Lead, 2,501 Leclanch cell, 500 Leucine, 622t... 

The power density / (Wkg-1) of the element results if the power is related to the battery weight. Figure 7 shows the current-voltage characteristic of a Leclanche element. 

The dry cell was invented by Leclanche in the 1860s. This type of battery was developed in the 19th century. In the 1940s, Rubel achieved significant progress in alkaline-zinc batteries, and manufactured zinc powder with high surface area to prevent zinc passivation. 

Figure 2 shows a comparison of the discharge characteristics between alkaline-manganese batteries and Leclanche batteries. The capacity of the alkaline-manganese batteries is about three times as large as that of the Leclanche batteries. 

Figure 1 shows the principal Zn-carbon (Leclanche) cell and Figure 2 shows the basic construction of a cylindrical AA-size alkaline Zn - Mn02 cell. 

Figure 1. The design principle of a cylindrical Zn-carbon (Leclanche) cell [21. I, Zinccan 2, separator MnO, bobbin (Reproduced by courtesy of Varta Battery AG).

Zn - Mn02 batteries [2] dominate the world s small-format battery industry. In 1995 Zn-carbon batteries (the carbon rod in the center of Leclanche cells is the reason for this name) comprised 67 percent of the world market, and the other 33% belonged to alkaline cells (Table 1). 

Leclanche cells can be assumed. The accuracy of the total capacity calculations is not better than 10 percent due to temperature and other variations, but the economy of recharging is clear. 

Figure 2. Schematic semi-ideal discharge curves of Mn02 in 9 mol L 1 and 5 mol L 1 NH4CI2 + 2 mol L l ZnCl2 solutions. IL, range of discharge capacity of commercial alkaline MnO, - Zn R2, range of discharge capacity of commercial Leclanche or zinc chloride cells.

The "classical" Leclanche cell uses zinc sheet formed into a cylindrical can serving simultaneously as the anode and as the cell container (AB1C1). The cathode is a mixture of Mn02 and graphite wrapped into a piece of separator and contacted by a central carbon rod. The can dissolves slowly when the cell is not in use and faster when the cell delivers electrical energy. The reaction following the primary electrochemical zinc dissolution [Eq. (19)] leads, in the case of an ammonium chloride electrolyte, to a zinc diammine cation ... 

The alkaline version of the Mn02 / zinc cell follows a different concept because it turns the construction of the Leclanche cell completely around now the cathode (Mn02 + carbon) forms a hollow cylinder contacting the inner wall of the cell container (steel) along its outer surface. The inner cavity has to accommodate anode, electrolyte, separator, and current collector. Usually, the separator forms a basket, which is automatically inserted and pre-... 

Perhaps the first practical application of carbonaceous materials in batteries was demonstrated in 1868 by Georges Le-clanche in cells that bear his name [20]. Coarsely ground MnO, was mixed with an equal volume of retort carbon to form the positive electrode. Carbonaceous powdered materials such as acetylene black and graphite are commonly used to enhance the conductivity of electrodes in alkaline batteries. The particle morphology plays a significant role, particularly when carbon blacks are used in batteries as an electrode additive to enhance the electronic conductivity. One of the most common carbon blacks which is used as an additive to enhance the electronic conductivity of electrodes that contain metal oxides is acetylene black. A detailed discussion on the desirable properties of acetylene black in Leclanche cells is provided by Bregazzi [21], A suitable carbon for this application should have characteristics that include (i) low resistivity in the presence of the electrolyte and active electrode material, (ii) absorption and retention of a significant... 

The studies by Biermann et al. [28] indicate that the carbon blacks used as the conductive matrix in Leclanche cells remain chemically inert, that is, they do not undergo oxidation during storage or discharge of the cell. However, Caudle et al. [29] found evidence that the ion-exchange properties of carbon black, which exist because of the presence of surface redox groups, are responsible for electrochemical interactions with Mn02. The extent of MnO, reduction to MnOOH depends on the carbon black (i.e., furnace black > acetylene black). 

FIGURE 12.21 A commercial dry cell. The dry cell is also called the Leclanche cell, for Georges Leclanche, the French engineer who invented it in about 1866. The electrolyte is a moist paste. 

From the 1960s onward, alkaline zinc-manganese dioxide batteries started to be produced. They have appreciably better electrical performance parameters (see Section 19.4.3) but do not differ from Leclanche batteries in their operating features, are produced in identical sizes, and can be used interchangeably with them. Thus, a gradual changeover occurred and phaseout of the older system is now almost complete. 

Compared with the Leclanche batteries, alkaline manganese dioxide batteries offer better performance at high discharge currents and lower temperatures and a better shelf life. They are more expensive than Leclanche batteries, but their cost per unit of energy is competitive and resources of raw materials are sufficient for mass production of these batteries. 

Rather than natural ores as in Leclanche batteries, electrolytic manganese dioxide (EMD), which is produced by anodic oxidation of Mn ions at graphite electrodes in solutions of manganese salts, is used as the active material for the positive... 

Laar, Johannes Jacobus van, 106 Laidler, Keith I., 240 Landman, U., 684 Langmuir, Irving, 158 Leclanche, Georges, 350 Leiva, Ezequiel, 674 Letheby, H., 458... 

The Leclanche cell (also known as the dry cell) is frequently used to power flashlights, watches, calculators, and a number of other portable devices. Despite the name dry cell, this battery does contain an electrolyte solution but only in the form of dense paste. There are two versions of this cell, the acid version and the alkaline version. 

The acid version of the cell was patented in 1866 by the French chemist George Leclanche, and is shown schematically in Figure 6.14 (A). The cell, in shorthand notation, corresponds to ... 

The Leclanche dry cell with zinc replaced by magnesium offers considerable advantages. In the electromotive series, magnesium occupies a more basic position as compared to zinc ( n = -0.76 V / g = -2.38 V), and this means that the voltage of a magnesium cell is greater than that of a similar zinc cell. 

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