A battery is a device that converts chemical energy into electrical energy. Each battery has two electrodes, an anode (the positive end) and a cathode (the negative end). An electrical pathway runs between these two electrodes (since there is a voltage/potential difference between them), going through a chemical called an electrolyte (which can be either liquid or solid). This unit consisting of two electrodes is called a cell (often called a voltaic cell). Batteries are used to power many devices and are also used make the spark that starts a gasoline engine.
The first battery-like discovery occurred in 1786, when Count Luigi Galvani (an Italian anatomist, 1737-1798) found that when the muscles of a dead frog were touched by two pieces of different metals, the muscle tissue twitched.
Count Alessandro Giuseppe Antonio Anastasio Volta (Feb. 18, 1745- March 5, 1827) was an Italian physicist who realized that the twitching was caused by an electrical current that was created by chemicals. Volta invented the chemical battery (also called the voltaic pile) in 1800. His first voltaic piles were made from zinc and silver plates (separated by a cloth) put in a salt water bath. (This is similar to the unpleasant phenomenon that happens when people with metal tooth fillings bite into aluminum foil – a small electrical current flows from one metal to the other metal, flowing through the acidic saliva and giving the biter an unpleasant sensation.) Volta soon improved the pile, using zinc and copper in a weak sulfuric acid bath. Volta’s invention provided the first generator of continuous electrical current.
In 1820, the French physicist André-Marie Ampère discovered many of the laws governing the relationship between electricity and magnetism, along with how a battery works. Ampere discovered that electricity moves through conductors, and that electrical charges flow from one electrode to the other. Ampere invented the astatic needle, which detected electrical currents.
Storage batteries are batteries that can be recharged (they are also called secondary batteries or accumulators). In 1859, the French physicist Gaston Plante (1834-1889) invented a battery made from two lead plates joined by a wire and immersed in a sulfuric acid electrolyte; this was the first storage battery. It was large and hard to move because of the liquid electrolyte.
The dry cell is a an improved voltaic cell with a cylindrical zinc shell (the zinc acts as both the cathode and the container) that is lined with a porous material (not a liquid) saturated with ammonium chloride (the electrolyte). A carbon rod (the anode) is in the center of the cylinder, surrounded by graphite. This type of battery decays when not in use. The dry cell battery was developed in the 1870s by Georges Leclanche of France, who used an electrolyte in the form of a paste.
Edison batteries (also called alkaline batteries) are an improved type of storage battery developed by Thomas Edison. These batteries have an alkaline electrolyte, instead of an acid. Its electrodes are plates of iron and nickelic oxide immersed in a caustic potash electrolyte (this is a base, and not acidic).