Zinc-carbon batteries cylindrical

The zinc-carbon battery is made in two basic shapes, cylindrical and flat, and is available in many sizes. The weight can range from 6g to 900g and the capacity from 300 mAh to 40 Ah... 

The zinc-carbon battery is made in many sizes and a number of designs but in two basic constructions cylindrical and flat. Similar chemical ingredients are used in both constmc-tions. 

Types of activated carbon which have electrical conductivity can be used instead of manganese dioxide as a depolarizer in dry-cell batteries.77 Powdered activated carbon is treated with ammonium chloride and pressed into a porous cylindrical shape that is placed in a zinc container forming the outer electrode. If provision is made for a sufficient. supply of air, the effect of the activated carbon cylinder is similar to that of"manganese dibxide. The potential of the activated carbon batter is 0.1 volt lower than that of the manganese dioxide type, but the voltage is steadier and is practically constant throughout the life of the battery. 

Alkaline cells use the same zinc-manganese dioxide couple as Leclanche cells. However, the ammonium chloride electrolyte is replaced with a solution of about 30 wt% potassium hydroxide (KOH) to improve ionic conductivity. The ceU reactions are identical to those above, but the battery construction is rather different (Figure 9.7). The negative material is zinc powder, and the anode (negative terminal) is a brass pin. The positive component is a mixture of Mn02 and carbon powder that surrounds the anode. A porous cylindrical barrier separates these components. The positive terminal (cathode) is the container, which is a nickel-plated steel can. 

In batteries with metallic container one terminal must be electrically insulated from it. In low-temperature batteries for this purpose rubber or plastic gaskets are used, which provide a sufficient effective sealing of joints. But in sealed batteries with an alkaline electrolyte solution (e.g., in cylindrical alkaline manganese-zinc batteries), after some time the alkaline solution begins to creep around most sealing gaskets and then forms on the outside white patches of alkali carbonates. 

A standard dry cell is made with a zinc anode (negative pole), in the form of a cylindrical pot, with a carbon cathode (positive pole) in the form of a central rod. The electrolyte is ammonium chloride in the form of a paste. Ammonium chloride and manganese dioxide are present in the remaining space between the electrolyte and carbon cathode. In some modem types of high-power batteries, the ammonium chloride has been replaced by zinc chloride. 

The following cross-sectional drawings provide a quick comparison as to how these considerations influence the final battery design and electrode configurations. Figures 1, 2, and 3 show the cross sections of the three most common cylindrical ceU designs. Figure 1 is referred to as a carbon zinc construction where the center carbon electrode, which is used as a cathode current collector and gas vent, is most evident, and... 

Figures 11J5 and 11.16 illustrate two designs of Leclanche battery. The first shows the traditional cylindrical design. The negative zinc electrode is a zinc lining to the metal can which is amalgamated with mercury to minimize hydrogen gas formation by reaction of the metal with water the separator is a paper stiffened with cellulose or starch placed adjacent to the zinc can. The positive current collector is a carbon rod at the centre of the can, while most of the volume is taken up by the positive paste. This is a mixture of powdered manganese dioxide ainmotmtm chloride and acetylene black (carbon) to increase the conductivity the pores are filled with an aqueous electrolyte (NH Cl + ZnCl ) gelled by addition of starch. The can is totally scaled.

Construction of the zinc chloride cylindrical battery (Fig. 8.3) differs from that of the Leclanchd battery in that it usually possesses a resealable, venting seal. The carbon rod serving as the current collector is sealed with wax to plug any vent paths (necessary for... 

The flat cell is illustrated in Fig. 8.5. In this construction, a duplex electrode is formed by coating a zinc plate with either a carbon-filled conductive paint or laminating it to a carbon-filled conductive plastic film. Either coating provides electrical contact to the zinc anode, isolates the zinc from the cathode of the next cell, and performs the function of cathode collector. The collector function is the same as that performed by the carbon rod in cylindrical cells. When the conductive paint method is used, an adhesive must be placed onto the painted side of the zinc prior to assembly to effectively seal the painted surface directly to the vinyl band to encapsulate the cell. No expansion chamber or carbon rod is used as in the cylindrical cell. The use of conductive polyisobutylene film laminated to the zinc instead of the conductive paint and adhesive usually results in improved sealing to the vinyl however, the film typically occupies more volume than the paint and adhesive design. These methods of construction readily lend themselves to the assembly of multi-cell batteries. 

Cylindrical alkaline manganese batteries have an inverted construction compared with the familiar Leclanch carbon-zinc battery construction. A typical construction of this type of battery is shown in Figure 21.1. 

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