A useful everyday item whose intricacies are rarely understood is the battery. In technical terms, a battery is any self-contained unit that generates and stores power through an electrochemical reaction. Batteries are manufactured from a wide range of materials and are used in a multitude of applications. In fact, all organic bodies store and produce a small amount of charge, so by definition are batteries, including the famous 1.2 volt potato battery seen in science fairs the world over.
In 1800, the Italian physicist Alessandro Volta invented the first electrochemical cell called a voltaic pile. Over the next 200 years, scientists delved into the problem of creating less dangerous and more reliable and portable batteries.
Some of the significant contributions to this technology have come from both physicists and chemists seeking to improve the voltaic pile, developing a number of wet cell batteries, including the Daniel’s, Porous Pot, Gravity, and Chromic Acid cells. The earliest rechargeable battery was the lead-acid cell, invented by Gaston Planté in 1859. Lead-acid batteries are still used in automobiles and other applications where their heavy weight is not a concern.
Wet cell batteries had some drawbacks; they produced caustic and dangerous liquids like sulfuric acid, or gave off toxic fumes, or were simply too fragile to move. The solution was to develop an electrochemical cell that did not use a liquid solution as a medium and thus became more portable and less volatile, called a dry cell. The first dry cell battery was the zinc-carbon cell invented by Georges Leclanche in 1866, although his design had to be refined before it was commercially successful. Electrochemical dry cell technology continued to be perfected and new batteries came into production in the twentieth and twenty-first centuries.
Batteries are not only dry or wet; they are also categorized as primary or secondary cells. Primary cells are disposable because their components are depleted through use. They are very stable, maintaining capacity over time when stored. They commonly power things like flashlights, toys, and many other portable devices and tools. The most commonly used types of primary cells include the following:
- Atomic: power cells that use a radioactive source to generate power, include betavoltaics, optoelectric nuclear batteries and nuclear micro-batteries; very costly but have a high energy density and long lifespan making these batteries ideal in machines that are not regularly or easily maintained, such as on spacecraft, in wind turbines, in pacemakers and remote scientific research stations.
- Lithium: have a long life but are very costly; they have many applications, including in pacemakers, small portable electronic devices, laptops, calculators and remote automobile door locks, to name but a few.
- Zinc-Carbon: these are the most common and least expensive of the primary batteries and are often sold with electronic devices.
Secondary cells are rechargeable because the electrochemical reaction can be reversed, but they can lose capacity quickly when in use. There are a number of types, the most common being the following:
- Lithium-Ion and Lithium-ion polymer: commonly sold in electronics because they lose their charge slowly when not in use; however, there is considerable health and environmental risk if damaged.
- Nickel: including Nickel-metal hydride and Nickel-cadmium cells that have a high energy density and rapid recharge.
Batteries are in use everywhere in contemporary technology. Thus, understanding their structure and function is both pragmatic and interesting. For a comprehensive list of battery types, see Wikipedia’s List of battery types; for a list of battery and electricity related science projects, see MiniScience.com’s comprehensive library.