Many products that run on electricity require batteries. A battery is defined as any device containing two or more electrochemical cells that convert stored chemical energy into electrical energy. These cells are composed of a positive terminal (cathode) and a negative terminal (anode). The positive terminal has more electrical potential energy, while the negative terminal is the source of electrons that when connected to an external circuit will flow and deliver energy to any device attached to the battery. Electrolytes are able to move as ions and allow the chemical reactions to be completed at each terminal and deliver energy to the external circuit; the movement of ions within a battery allow the current to flow out and perform work. While a battery, by definition, has multiple cells, single cells are also popularly called batteries.
History of Batteries
The use of the term “battery” dates back to around 1748, when Benjamin Franklin (also famous for his contributions to the discovery of electricity) called multiple Leyden jars (a glass jar that “stored” static electricity and was used for early experiments of electricity, and has properties similar to that of a modern capacitor), working together a “battery.” Franklin borrowed this term from the military, as the original meaning of the word battery was “a group of two or more similar objects functioning together.”
The Voltaic Pile and Contact Tension
By 1780, Italian scientist Luigi Galvani discovered what he called “animal electricity” when he was dissecting a frog hanging from a brass hook using an iron scalpel, noting that the frog's leg twitched when it came in contact with the iron scalpel. However, Alessandro Volta, another Italian scientist, disagreed with Galvani's findings. Volta claimed that Galvani's “animal electricity” was merely the result of two different metals joined together by a moist intermediary. Volta verified his hypothesis through experiments and published his results in 1791.
In 1800, Volta invented the first true battery, the voltaic pile. This pile consisted of copper and zinc discs piled on top of each other, separated by moist intermediaries such as cloth or cardboard soaked in brine (electrolytes). This was an improvement over the Leyden jar in that it produced a continuous and stable current without losing a lot of charge while not in use. Volta used various metals while perfecting the voltaic pile, and then concluded that using zinc and silver as metals gave the best results.
Volta believed that contact tension—the result of two different materials touching each other—led to the current, rather than chemical reactions. However, this has largely been rejected. Volta's pile models had initial problems such as electrolyte leaking and short circuits due to the weight of the discs. William Cruickshank, a Scottish scientist, solved this problem by putting the elements in a box instead of stacking them. Cruickshank's design was called the trough battery. Volta made a variation on his original invention using a chain of cups filled with a salt solution linked by metallic arcs dipped into the liquid, or the Crown of Cups. While more efficient than his original model, it was not as popular.
Another issue for Volta's invention was short battery life (an hour). The current produced caused a film of hydrogen bubbles forming on the copper, increasing internal resistance (polarization, which is counteracted in today's batteries through several additional measures). In addition, minute short-circuits would form around zinc impurities, and cause the zinc to degrade. William Sturgeon, an English scientist, would treat the zinc's surface with mercury to prevent the degradation of the zinc.
The Daniell Cell
By 1836, John Daniell would solve the other problem in the Voltaic Pile (hydrogen bubbles) by using a second electrolyte to consume the hydrogen produced by the first. The Daniell cell, a copper pot with a copper sulfate solution immersed in a earthenware container filled with sulfuric acid and a zinc electrode. The earthenware barrier was porous, allowing ions to pass through, but prevented the solutions from mixing—if allowed to mix, copper ions would undergo reduction without producing a current, destroying the battery's life.
Copper buildup, however, blocked the pores and cut the battery's life short. The advantage it had over the Voltaic Pile is that it provided a longer and more reliable current because it deposited copper (a conductor) rather than hydrogen (an insulator, or non-conductor) on the cathode, and was also less corrosive. It was used in practical applications for telegraph networks. The Daniell cell was also the historical basis of the definition of the unit of electromotive force (volt).
Other variations of batteries came forth during the 19th century, including Bird's cell (1837), the porous pot cell (1838), and the gravity cell (1860s). The gravity cell was invented by a French scientist named Callaud, and was a variation on the Daniell cell that dropped the porous barrier and replaced it with a layer of zinc sulfate on top of a layer of copper sulfate. The Poggendorf cell (1842) and Grove cell (1839) were also developed, providing more voltages than the Daniell cell, but failed for various reasons. The Poggendorff cell required the user to raise the zinc plate when not in use, while the Grove used rare and expensive materials such as platinum, making it expensive to use, as well as gave off nitric oxide fumes when used. The Grove cell gained popularity in North America for a while, but was eventually replaced by the gravity cell.
Rechargeable Batteries and Dry Cell Batteries
1859 saw the development of the lead-acid battery, or the first rechargable battery. Gaston Plante invented this battery, and it was rechargeable by passing a reverse current through the battery. The anode was lead and the cathode was lead dioxide immersed in sulfuric acid. The reaction at the lead anode releases electrons, and the reaction at the lead dioxide cathode consumed them, producing a current. A reverse current thus recharged the battery. The LeClanche cell (1864) used a zinc anode and a manganese dioxide cathode wrapped in porous materials and dipped in a jar of ammonium chloride. This was widely used in telegraphy, signaling and electric bells.
By 1886, the first dry cell battery was invented by Carl Gassner, a German scientist. This battery in particular is called the dry cell because it did not have a free liquid electrolyte, instead opting to use ammonium chloride mixed with plaster of Paris to create a paste, along with a small amount of zinc chloride. This is also the first patented battery (U.S. Patent 373,064). Gassner's dry cell was solid, did not require maintenance, and did not spill. It also had a 1.5 volt potential. The National Carbon Company (NCC) started marketing the battery in 1896, and was considered the first battery for the masses, and could be used in portable electrical devices, one of which was the flashlight. The zinc-carbon battery is still being manufactured to this very day. Other batteries were patented in the second half of the 20th century as well, but a major breakthrough came through when Waldemar Jungner, a Swedish scientist, invented the nickel-cadmium battery in 1899, which was also rechargeable and made of nickel and cadmium electrodes in a potassium hydroxide solution. It was the first battery to use alkaline electrolytes, and it was sold commercially in Sweden in 1910 and made it to the United States by 1946. The major downside to these batteries were its high cost.
Twentieth Century: Nickel-Iron, Alkaline, Lithium
Jungner also invented a nickel-iron battery, but did not patent it as he found it inferior to the nickel-cadmium battery that he invented. American inventor and scientist Thomas Edison patented it for himself and started selling it in 1903. Edison intended to use them as car batteries, and eventually make electric cars the standard. However, by the time he did this, the Model T Ford, the first affordable car, was already using gasoline—but he managed to find other applications for electric and diesel-electric rail vehicles and lamps used in mines.
By the 1950s, the zinc-carbon battery was still popular, but still suffered from short battery life. Lewis Urry, an engineer with Union Carbide, said that alkaline batteries had more potential than the zinc-carbon ones. By 1959, he used a battery composed of a manganese dioxide cathode and a powdered zinc anode with an alkaline electrolyte.
Nickel-hydrogen batteries were used for communication satellites as well, but nickel-metal hydride batteries reached the market in 1989. In addition to having a longer battery life than the nickel-cadmium batteries, they also were less damaging to the environment (cadmium is toxic).
Lithium batteries are the most popular batteries today due to their low density and high electrochemical potential. While lithium was being experimented on as far back as 1912, it hit the market only in the 1970s. The 1980s saw the next great wave of innovation in the battery market. John B. Goodenough, an American chemist, discovered the LiCoO2 cathode (positive lead) and Moroccan scientist Rachid Yazami discovered the graphite anode (negative lead). Akira Yoshino of Asahi Chemical, a Japanese firm, built the first lithium-ion battery prototype in 1985, and by 1991, Sony started selling it on the market.
By 1997, the lithium polymer battery was released, holding their electrolyte in a solid polymer composite as opposed to a liquid solvent, with the electrodes and separators laminated to one another. This is an important development because it allowed batteries to be encased in a flexible wrapping instead of a rigid metal case, allowing it to be shaped to fit any device. These are the batteries we see in mobile phones today, also contributing to the thinning of smartphones.
Types of Batteries
There are many types of batteries as outlined above, but they are divided into primary and secondary batteries. The difference between the two is that primary batteries cannot be recharged because the chemical reactions cannot be easily reversed. Their applications are limited to devices that have low current drain, used only intermittently, or used away from alternative power sources. Primary batteries can produce current immediately on assembly. Zinc-carbon batteries and alkaline batteries fall under this category.
Secondary batteries have to be charged before they can be used and are assembled with active materials in the discharged state. These batteries can be charged and recharged by applying electric current. The batteries that fall under this category are lead-acid batteries, nickel-cadmium batteries, nickel-zinc batteries, nickel-metal hydride batteries, and lithium-ion batteries.
Capacities of Batteries and Battery Lifetime
Today, batteries' capacities are measured in milliampere hours (mAh). This can be affected by many factors: corrosion, self-discharge, and physical component changes. For example, disposable batteries can lose between 8 to 20 percent of its original charge per year at temperatures of 20 to 30 degrees Celsius (68 to 86 degrees Fahrenheit). The available capacity drops when temperature also drops; cold temperatures increase internal resistance and lowers the capacity of the battery. While high temperatures increase performance because of improved electrochemical reactions, its life will also be shortened.
Batteries should be used at around 20°C (68°F) for optimal performance. While batteries are still operational even at 30°C (86°F), its cycle life is reduced by 20 percent. At 40°C (104°F), their life cycle is reduced even further to 40 percent, and at 45°C (113°F), their life cycle is reduced by half. Going in the opposite direction will stunt the performance; at -20°C (-4°F) most batteries stop functioning, although nickel-cadmium batteries and lithium-ion batteries can withstand temperatures of up to -40°C (-40°F). This is especially important if you are camping or hiking in places with extreme conditions, such as deserts, polar regions, and high altitude regions.
Batteries are subject to hazards as well—they are composed of materials toxic to human beings (lead, mercury, and cadmium for instance), can corrode (exposing people to these toxic materials) and are also damaging to the environment. In recent times, however, e-waste recycling has allowed for batteries to be recycled, creating new batteries out of old ones. In addition, batteries are harmful or fatal if swallowed. Button cells in particular can cause tissue damage if swallowed.