A dry-cell battery uses an immobili

A dry-cell battery uses an immobilized electrolyte that minimizes moisture and allows for superior portability.


A Zinc-Carbon Dry-Cell Battery

An illustration of a zinc-carbon dry cell. In it, a zinc casing acts as the anode, surrounding a carbon rod, which acts as a cathode. Between them, the electrolyte paste works as the battery.

Key Points

A battery contains electrochemical cells that can store chemical energy to be converted to electrical energy.

A dry-cell battery is a subtype of battery. It stores energy in an immobilized electrolyte paste, which minimizes the need for water. A low-water requirement maximizes portability.

Common examples of dry-cell batteries include zinc-carbon batteries and alkaline batteries.

The overall reaction of energy storage can be represented through balanced chemical equations.

Terms

cathode

The electrode of an electrochemical cell at which reduction occurs.
anode

The electrode of an electrochemical cell at which oxidation occurs.
electrolyte

a substance that, in solution or when molten, ionizes and conducts electricity

Rate these SmartNotes:

In electricity, a battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. The dry cell is one of many general types of electrochemical cells.

A dry cell has the electrolyte immobilized as a paste, with only enough moisture in it to allow current to flow. Unlike a wet cell, a dry cell can operate in any orientation without spilling, as it contains no free liquid. This versatility makes it suitable for portable equipment. By comparison, the first wet-cell batteries were typically fragile glass containers with lead rods hanging from an open top. They therefore needed careful handling to avoid spillage. The development of the dry-cell battery allowed for a major advance in battery safety and portability.

A common dry-cell battery is the zinc-carbon battery, which uses a cell that is sometimes called the dry Leclanché cell. The cell is made up of an outer zinc container, which acts as the anode. The cathode is a central carbon rod, surrounded by a mixture of carbon and manganese (IV) oxide (MnO2). The electrolyte is a paste of ammonium chloride (NH4Cl). A fibrous fabric separates the two electrodes, and a brass pin in the center of the cell conducts electricity to the outside circuit. Below is an illustration of a zinc-carbon battery.

Figure 1

Chemical reactions occur in every part of the battery to allow for energy storage; the reactions can be described using balanced chemical equations that delineate the electron flow. The paste of ammonium chloride reacts according to the following half-reaction:

The manganese (IV) oxide in the cell removes the hydrogen produced by the ammonium chloride, according to the following reaction:

The combined result of these two reactions takes place at the cathode. Adding these two reactions together, we get:

Finally, the anode half-reaction is as follows:

Therefore, the overall equation for the cell is:

Another example of a dry-cell battery is the alkaline battery. Alkaline batteries are almost the same as zinc-carbon batteries, except that the electrolyte used is potassium hydroxide (KOH) rather than ammonium chloride. In some more modern types of so-called "high-power" batteries (with much lower capacity than standard alkaline batteries), the ammonium chloride is replaced by zinc chloride.