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Alkaline battery

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An alkaline battery is a type of primary battery that provides electrical energy through chemical reactions.

Alkaline-battery-english
Alkaline-battery-english

These batteries are defined by their electrolyte, which is a substance that allows ions to move. In alkaline batteries, this electrolyte is typically potassium hydroxide (KOH). Because potassium hydroxide has a pH value above 7, the substance is considered alkaline. This distinguishes them from older zinc–carbon batteries, which use acidic electrolytes like ammonium chloride or zinc chloride. Compared to those older models, alkaline batteries offer a higher energy density and a longer shelf life while maintaining a standard voltage.

The mechanism of an alkaline battery relies on a specific chemical reaction between two electrodes. The negative electrode, or anode, is composed of zinc. The positive electrode, or cathode, consists of a compressed paste of manganese dioxide (MnO2) mixed with carbon powder for conductivity.

Alkaline-battery-english
Alkaline-battery-english

A separator made of cellulose or a synthetic polymer sits between these electrodes. This separator allows ions to pass through but prevents the materials from touching and causing a short circuit. During discharge, the zinc is oxidized, changing from an oxidation state of 0 to +2. Simultaneously, the manganese is reduced, changing from an oxidation state of +4 to +3. The potassium hydroxide electrolyte is not consumed during this process because the ions produced and consumed in the reactions are equal.

Alkaline batteries are manufactured in several distinct forms to suit different needs. They are commonly found in cylindrical shapes, such as the standard AA, AAA, C, and D sizes. These cylindrical cells are housed in a drawn stainless steel can, which serves as the cathode connection. They are also available in small button or coin cell formats.

Button cells and 9v cells (3)
Button cells and 9v cells (3)

Some devices require more power, so multiple cells can be connected in series. For example, connecting three cells together will produce a total voltage of approximately 4.5 V. In a standard cylindrical cell, the negative electrode is at the flat end, while the positive terminal is the raised button.

The history of alkaline technology involves several important inventors and milestones. Waldemar Jungner first developed batteries using an alkaline electrolyte in 1899. In 1901, Thomas Edison developed nickel–iron batteries that also utilized a potassium hydroxide electrolyte.

Thomas Edison's nickel–iron batteries
Thomas Edison's nickel–iron batteries

The modern alkaline dry battery used today was invented by Canadian engineer Lewis Urry in the 1950s. Urry worked in Canada before joining Union Carbide's Eveready Battery division in Cleveland, Ohio. On October 9, 1957, Urry, Karl Kordesch, and P. A. Marsal filed a patent for this technology. This patent was granted in 1960 and assigned to the Union Carbide Corporation.

Alkaline batteries are incredibly significant in the global market and daily life. Worldwide, over 10 billion individual units are produced. In the United States, these batteries account for 80% of all manufactured batteries. Their popularity is reflected in sales statistics across different regions. In Switzerland, they represent 68% of sales, while in the UK, they make up 60%. In the European Union, they account for 47% of all battery sales, including secondary types. In Japan, they represent 46% of all primary battery sales. They power a vast range of household items, including digital cameras, toys, flashlights, and portable media players.

Understanding how capacity and voltage work is essential for using these batteries effectively. A fresh alkaline cell typically has a nominal voltage of 1.5 V. However, the actual zero-load voltage can range from 1.58 V to 1.60 V depending on the purity of the manganese dioxide. The capacity of the battery depends heavily on the load placed upon it. For example, an AA battery might have a high effective capacity at a low drain. However, at a high load of 1.0 A, such as that required by digital cameras, the capacity can drop significantly. A cell is generally considered fully discharged when its voltage drops to approximately 0.9 V.

While highly useful, alkaline batteries require careful handling due to potential leakage.

Alkaline Battery Leakage Inside a Product
Alkaline Battery Leakage Inside a Product

As batteries discharge or age, they can generate hydrogen gas. This gas increases internal pressure, which may rupture the seals or the outer metal canister. When this happens, the caustic potassium hydroxide can leak out. This substance can cause irritation to the skin, eyes, and respiratory system. It can also corrode metals like aluminum. If the leak reaches the air, the potassium hydroxide can react with carbon dioxide to form potassium carbonate. This creates a feathery, crystalline structure that can spread and damage electronic circuit boards. To prevent this, it is best to store batteries in a dry place at room temperature and remove them from devices when not in use.

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🖼️ Images & Media (4)
File:Thomas Edison's nickel–iron batteries.jpg
Thomas Edison's nickel–iron batteries.jpg
File:Button cells and 9v cells (3).png
Button cells and 9v cells (3).png
File:Alkaline-battery-english.svg
Alkaline-battery-english.svg
File:Alkaline Battery Leakage Inside a Product.png
Alkaline Battery Leakage Inside a Product.png
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