Batteries work through redox reactions, transferring electrons between an oxidizer and a reducer to create a direct current. Manganese dioxide and zinc are commonly used as oxidizers and reducers, respectively. Batteries have not substantially changed since their invention.
Batteries, or dry cells, work by connecting, through a circuit, a material that wants to donate electrons to another material that lacks electrons. These are called a reducer or reducing agent and an oxidant or oxidizing agent, respectively. The process is one of many redox reactions that include rusting iron and bleaching clothes.
When an oxidizer and a reducer meet, chemical reactions occur in both and electrons are transferred. The transfer of electrons creates a direct current (DC). In typical batteries, this is 1.5 volts.
One of the first oxidants to be studied in detail was elemental oxygen. Oxygen gains electrons from other substances such as iron, causing the material to oxidize. When iron oxidizes, it binds with oxygen molecules to create iron oxide or rust. There are many other oxidants, including bromine, chlorine and fluorine. In conventional batteries, manganese dioxide powder is used as an oxidizer, turning into manganese oxide when depleted.
The term reducer comes from metallurgy and refers to a chemical reaction in which a substance loses electrons. The chemical transformation is one from an oxide, such as iron oxide, to a non-oxide, such as iron. This chemical process has long been used to turn minerals into pure metals, and is so called because the reaction causes the sample to lose mass. In conventional batteries, the reducer is zinc.
A battery looks like one, but it’s actually two: an oxidizer and a reducer placed next to each other and separated by a barrier. Each is connected to an electrode, which are called positive and negative, depending on the substance to which they correspond. When the circuit between the positive and negative electrode is completed, the electrons flow and continue to flow until equilibrium is reached.
Usually, these power supplies are connected to an external load, which draws energy from the electron current. Sometimes, direct current is connected to an alternator, which converts it to alternating current (AC), which is the type of electricity used by our household appliances. Batteries have not substantially changed since they were invented and are a glaring weakness for the field of electronics, where price-performance increases have historically been exponential.
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