How Batteries Are Made

Building Blocks of the Alkaline Battery

Alkaline batteries, the most common type of household battery over the past several decades, not to be confused with rechargeable types such as nickel cadmium batteries, are so named for the alkaline character of the potassium hydroxide solution inside them (an earlier generation of batteries used an acidic solution). The primary ingredients, along with the potassium hydroxide, are manganese dioxide, carbon black (a type of amorphous carbon generated by the partial combustion of several petroleum products), and zinc. The positively charged part of an alkaline battery is called the cathode, while the negative part is known as the anode. Within the interior of the battery, the anode is the innermost layer and is concentrically surrounded by the cathode. The cathode is a mixture of the manganese dioxide and carbon black, which is similar to graphite; zinc is the main element of the anode.

At the beginning of the manufacturing process, the manganese dioxide, carbon black and potassium hydroxide are mixed and then turned into a granulated powder. After the powder is aged, it is squeezed into a tablet shape called a "preform" (more than one of which may be used in a battery) for insertion into the nickel-plated steel can of the battery shell. The shell, directly contacting the preforms, thus becomes part of the cathode.

The anode, primarily made of zinc, is typically a gel containing smaller amounts of other substances. The gel is injected into the center of the cathode, where it is insulated from direct contact with the cathode by a paper or synthetic separator that has been soaked in an electrically conductive electrolytic alkaline solution. Once joined in a closed electrical circuit that is created by touching each end of the battery to leads, the internal unattached ends of the cathode and anode will instigate a flow of oxygen atoms that generates electricity.

A brass nail, a small insulating gasket, a washer and an end cap make up the sealing assembly. These components are inserted into the center of the can where they become electrically connected to the negatively charged anode and are locked into place with a flat metal bottom cap. The convex top cap, a steel plate containing a center protrusion that is a standardized symbol of the positively-charged end of the battery, is welded tight or glued with epoxy. The batteries are tested and labeled, which is normally done by applying a shrink-wrap label, before being sent to markets. Eventually, after use, the sealed enclosure of the can and the two ends can be expected to leak corrosive fluids that may not be containable if put into landfills. The federal government and some localities have laws and guidelines regarding safe battery disposal.