Positive alkaline-manganese batteries

The discharge of alkaline-manganese batteries comes from the electrochemical reactions at the anode and cathode. During discharge, the negative electrode material, zinc, is oxidized, forming zinc oxide at the same time, Mn02 in the positive electrode is reduced (MnOOH) ... 

Continuous research in primary alkaline manganese batteries ended up in the development of rechargeable alkaline manganese (RAM) cells. The design of these cells dated to 1975 [1], These batteries are basically an extension of the primary alkaline batteries. They also use zinc for the negative electrode, manganese dioxide for the positive electrode, and an aqueous solution of potassium hydroxide for the electrolyte. 

In acidic electrolytes only lead, because it forms passive layers on the active surfaces, has proven sufficiently chemically stable to produce durable storage batteries. In contrast, in alkaline medium there are several substances basically suitable as electrode materials nickel hydroxide, silver oxide, and manganese dioxide as positive active materials may be combined with zinc, cadmium, iron, or metal hydrides. In each case potassium hydroxide is the electrolyte, at a concentration — depending on battery systems and application — in the range of 1.15 - 1,45 gem"3. Several elec-... 

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. 

The only power sources feasible for all these portables are electrochemical batteries. Disposable batteries were the classical power source for flashlights, and still hold a very strong position (salt Leclanche later, alkaline dry cells of zinc-manganese dioxide type). Rechargeable batteries became ever more important first, nickel-cadmium, and more recently, nickel-hydride and lithium ion batteries. For convenient handling, a power source is usually placed somewhere inside the device, so it should respect certain limitations as to weight and volume. As a rule of thumb, a power source should not exceed 30-40% by mass and volume of the device powered by it. A similar upper limit 30-40% applies to the cost. 

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