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The alkaline battery gets its name because it has an alkaline electrolyte of potassium hydroxide.

As illustrated in Figure 1, the battery’s container is a cylindrical steel can, and serves as a current collector. The cathode of manganese dioxide and carbon is a hollow cylinder within the can, located very close to the can surface. Inside the hollow cathode are separator rings, which are positioned in layers, and inside the separator rings is the anode. The battery has either a metal or plastic jacket, as well as covers on its bottom and top, to help control polarity in applications.

General Information

The alkaline-manganese dioxide battery was introduced in the early 1960’s and remains in a strong position in today’s battery market. Theoretically, alkaline-manganese dioxide cells have a higher capacity than Leclanche, or zinc-carbon cells, of similar sizes. This is due to higher purity and activity of the manganese dioxide, the dense cathode with little electrolyte, and the efficient spacing of components. The voltage for this battery begins above 1.5 volts, which decreases gradually during discharge. In addition, the battery can function at temperatures up to 55 degrees Celsius.

Evolution of Today’s Alkaline-Manganese Dioxide Battery

The alkaline system has many advantages over the competing Leclanche or zinc-carbon battery. Alkaline batteries come in two forms, either as large cylindrical cells, or as miniature cells resembling buttons. Since its beginnings, the alkaline system has gone through many changes. First, it began using a gelled and amalgamated zinc powder anode within a compartment in its center while at the same time employing vented plastic seals. A butt-seam metal finish allowed the battery better internal volume. Furthermore, the use of organic inhibitors helped bulge and leakage problems, and a reduction of mercury helped make the battery even more efficient and environmentally sound. Today's version is 60% more powerful than the original alkaline battery that was introduced in the early 1960’s.

Chemistry

The alkaline-manganese dioxide battery contains electrolytically manufactured manganese dioxide and aqueous alkaline electrolyte, as well as zinc metal as a powder. Electrolytic manganese dioxide is more pure than standard reagent manganese dioxide, and has a greater reactivity. The electrolyte is caustic, and therefore, reduces the hydrogen gassing rate.

The cathode is comprised of a manganese dioxide and carbon mixture. Binders may also be added, as well as an electrolyte solution or water, to help build the cathode. The manganese dioxide causes the oxidation. Carbon is used in the cathode because manganese dioxide is not a good conductor on its own. Often, the carbon is in a graphite or acetylene black form, and the anode contains zinc powder, which is very pure due to distilling or electroplating from an aqueous solution. The powder is formed by atomization. The gelling agents are usually starch, polyacrylates, or ethylene maleic anhydride copolymers. The separators must be ionically conductive while at the same time insulating, and must be stable during oxidation and reduction. The battery’s container does not assist discharge in any way, and is usually made of steel.

The zinc-carbon battery or dry cell is the technological foundation of today's growing battery industry.

The components of the zinc-carbon battery are housed within a solid zinc can, which also serves as the battery's anode (Figure 1). The cathode mix is usually a moist substance of manganese dioxide powder, special carbon black, an electrolyte, and solution blended together. A carbon electrode rod runs down the middle, and the positive top cover and negative bottom cover are both metal. Zinc-carbon batteries usually provide 1.4 to 1.7 volts of D.C. electric power that gradually declines to .9 volts during use. The cells aren’t affected by the many impurities their ingredients contain, and remain inexpensive whether used on heavy or light electrical loads. Despite their low cost, the cells have excellent shelf life, and have very low leakage when unused for long periods of time.

The zinc-carbon cell, or dry cell, is the forefather of today’s cells, and is often called the Leclanche cell after its inventor, Georges Leclanche. The original Leclanche cell utilized only one liquid material, an ammonium chloride solution that replaced the acid electrolyte used in earlier cells. A manganese dioxide and carbon dry mix replaced the depolarizing solution of most previous cells, and a carbon bar, whose function was both a current collector and positive electrode, went down the middle. At its invention, it was restricted to laboratories due to its liquid content.

The first dry cell, also a zinc-carbon cell, appeared between 1886 and 1888, and was developed by Karl Gassner. At first, the electrolyte was composed of a paste made up of zinc oxide, sal ammoniac, and water, and the zinc negative electrode was also the container for the cell’s contents. The carbon rod went down the center of the battery, and served as its positive electrode.

The zinc-carbon cell has a zinc anode, a manganese dioxide cathode, and an electrolyte of ammonium chloride or zinc chloride, which is dissolved in water. For each unit of electrical energy a galvanic cell creates, an equivalent amount of electrode material salts must move or be altered to provide energy. Ammonium chloride and zinc chloride in an aqueous solution combine to form a moist mixture: the cathode contains solid ammonium chloride, which acts as a fuel reserve for the cell during intermittent operation, and materials such as gum karaya and ion exchange resins may be added to the cathode in order to increase the discharge efficiency. In addition, zinc carbon cells contain separators up to 3.5 mm thick that are made of cereal paste and electrolyte solution, and serve as an electrolyte reservoir as well as a membrane between the electrodes.