Around 1936, archaeologists uncovered in a village near Baghdad a set of terracotta jars which each contained a rolled-up sheet of copper which housed an iron rod. Some scientists speculate these to be ancient galvanic cells (roughly 2,000 years old, though the find's age is still debated), and dubbed them the "Baghdad Batteries". It is believed a common food acid, such as lemon juice or vinegar, served as an electrolyte. Modern replicas have successfully produced currents, lending credence to this hypothesis. If the collection was indeed a battery, it could have been used for electroplating, to produce mild electric shocks as a source of religious experience, or simply used to store ancient scrolls.
In 1780, Luigi Galvani was dissecting a frog affixed to a brass hook. When he touched its leg with his iron scalpel, the leg twitched. Galvani believed the energy that drove this contraction came from the leg itself, and called it "animal electricity".
However, Alessandro Volta, a friend and fellow scientist, disagreed, believing this phenomenon was actually caused by two different metals being joined together by a moist intermediary. He experimentally verified this hypothesis, and published it in 1791. In 1800 Volta invented the first true battery which came to be known as the Voltaic Pile. The Voltaic Pile consisted of pairs of copper and zinc discs piled on top of each other, separated by a layer of cloth or cardboard soaked in brine (i.e. the electrolyte). Unlike the Leyden jar, the Voltaic Pile produced a continuous and stable current, and lost little charge over time when not in use, though his early models could not produce a voltage strong enough to produce sparks. He experimented with various metals and found that zinc and silver gave the best results.
Volta believed the current was the result of two different materials simply touching each other—an obsolete scientific theory known as contact tension—and not the result of chemical reactions (however, see thermoelectric effect). Consequently, he regarded the corrosion of the zinc plates as an unrelated flaw that could perhaps be fixed by changing the materials somehow. However, no scientist ever succeeded in preventing this corrosion. In fact, it was observed that the corrosion was faster when a higher current was drawn. This suggested that the corrosion was actually integral to the battery's ability to produce a current. This, in part, led to the rejection of Volta's contact tension theory in favor of electrochemical theory. Volta's illustrations of his Crown of Cups and Voltaic Pile (first figure, above), have extra metal disks, now know to be unnecessary, on both the top and the bottom. The figure associated with this section, of the zinc-copper voltaic pile, has the modern design, an indication that "contact tension" is not the source of electromotive force for the voltaic pile.
Volta's original pile models had some technical flaws, one of them involving the electrolyte leaking and causing short-circuits due to the weight of the discs compressing the brine-soaked cloth. An Englishman named William Cruickshank solved this problem by laying the elements in a box instead of piling them in a stack. This was known as the trough battery. Volta himself invented a variant which consisted of a chain of cups filled with a salt solution, linked together by metallic arcs dipped into the liquid. This was known as the Crown of Cups. These arcs were made of two different metals (e.g. zinc and copper) soldered together. This model also proved to be more efficient than his original piles, though it didn't prove as popular.
Another problem with Volta's batteries was short battery life (an hour's worth at best), which was caused by two phenomena. The first was that the current produced electrolysed the electrolyte solution, resulting in a film of hydrogen bubbles forming on the copper, which steadily increased the internal resistance of the battery (This effect, called polarization, is counteracted in modern cells by additional measures). The other was a phenomenon called local action, wherein minute short-circuits would form around impurities in the zinc, causing the zinc to degrade. The latter problem was solved in 1835 by William Sturgeon, who found that mixing some mercury into the zinc eliminated the local action.
Despite its flaws, Volta's batteries provided a steadier current than Leyden jars, and made possible many new experiments and discoveries, such as the first electrolysis of water by Anthony Carlisle and William Nicholson.
A British chemist named John Frederic Daniell searched for a way to eliminate the hydrogen bubble problem found in the Voltaic Pile, and his solution was to use a second electrolyte to consume the hydrogen produced by the first. In 1836, he invented the Daniell cell, which consisted of a copper pot filled with a copper sulphate solution, in which was immersed an unglazed earthenware container filled with sulphuric acid and a zinc electrode. The earthenware barrier was porous, which allowed ions to pass through but kept the solutions from mixing. Without this barrier, when no current was drawn the copper ions would drift to the zinc anode and undergo reduction without producing a current, which would destroy the battery's life.
Over time, copper buildup would block the pores in the earthenware barrier and cut short the battery's life. Nevertheless, the Daniel cell provided a longer and more reliable current than the Voltaic cell because the electrolyte deposited copper (a conductor) rather than hydrogen (an insulator) on the cathode. It was also safer and less corrosive. It had an operating voltage of roughly 1.1 volts. It saw widespread use in telegraph networks until it was supplanted by the Leclanché cell in the late 1860s.
The Grove cell was invented by William Robert Grove in 1839. It consisted of a zinc anode dipped in sulfuric acid and a platinum cathode dipped in nitric acid, separated by porous earthenware. The Grove cell provided a high current and nearly twice the voltage of the Daniell cell, which made it the favoured cell of the American telegraph networks for a time. However, it gave off poisonous nitric oxide fumes when operated. The voltage also dropped sharply as the charge diminished, which became a liability as telegraph networks grew more complex. Platinum was also very expensive. The Grove cell was replaced by the cheaper, safer and better performing gravity cell in the 1860s.
Up to this point, all existing batteries would be permanently drained when all their chemical reactions were spent. In 1859, Gaston Planté invented the lead-acid battery, the first ever battery that could be recharged by passing a reverse current through it. A lead acid cell consists of a lead anode and a lead oxide cathode immersed in sulphuric acid. Both electrodes react with the acid to produce lead sulfate, but the reaction at the lead anode releases electrons whilst the reaction at the lead oxide consumes them, thus producing a current. These chemical reactions can be reversed by passing a reverse current through the battery, thereby recharging it.
Planté's first model consisted of two lead sheets separated by rubber strips and rolled into a spiral. His batteries were first used to power the lights in train carriages while stopped at a station. In 1881, Camille Alphonse Faure invented an improved version that consisted of a lead grid lattice into which a lead oxide paste was pressed, forming a plate. Multiple plates could be stacked for greater performance. This design was easier to mass-produce.
Compared to other batteries, Planté's was rather heavy and bulky for the amount of energy it could hold. However, it could produce remarkably large currents in surges. It also had very low internal resistance, meaning a single battery could be used to power multiple circuits.
The lead-acid battery is still used today in automobiles and other applications where weight isn't a big factor. The basic principle has not changed since 1859, though in the 1970s a variant was developed that used a gel electrolyte instead of a liquid (commonly known as a "gel cell"), allowing the battery to be used in different positions without failure or leakage.
Today cells are classified as "primary" if they produce a current only until their chemical reactants are exhausted, and "secondary" if the chemical reactions can be reversed by recharging the cell. The lead-acid cell was the first "secondary" cell.
Sometime during the 1860s, a Frenchman by the name of Callaud invented a variant of the Daniell cell called the gravity cell. This simpler version dispensed with the porous barrier. This reduced the internal resistance of the system and thus the battery yielded a stronger current. It quickly became the battery of choice for the American and British telegraph networks, and was used right up until the 1950s. In the telegraph industry, this battery was often assembled on site by the telegraph workers themselves, and when it ran down it could be renewed by replacing the consumed components.
The gravity cell consisted of a glass jar, in which a copper cathode sat on the bottom and a zinc anode was suspended beneath the rim. Copper sulfate crystals would be scattered around the cathode and then the jar would be filled with distilled water. As the current was drawn, a layer of zinc sulfate solution would form at the top around the anode. This top layer was kept separate from the bottom copper sulfate layer by its lower density and by the polarity of the cell.
The zinc sulfate layer was clear in contrast to the deep blue copper sulfate layer, which allowed a technician to measure the battery life with a glance. On the other hand, this setup meant the battery could only be used in a stationary appliance, else the solutions would mix or spill. Another disadvantage was that a current had to be continually drawn to keep the two solutions from mixing by diffusion, so it was unsuitable for intermittent use.
In 1866, Georges Leclanché invented a battery that consisted of a zinc anode and a manganese dioxide cathode wrapped in a porous material, dipped in a jar of ammonium chloride solution. The manganese dioxide cathode had a little carbon mixed into it as well, which improved electrolyte conductivity and absorption. It provided a voltage of 1.4 to 1.6 volts. This cell achieved very quick success in telegraphy, signalling and electric bell work. It was used to power early telephones—usually from an adjacent wooden box affixed to the wall—before telephones could draw power from the line itself. It couldn't provide a sustained current for very long. In lengthy conversations, the battery would run down, rendering the conversation inaudible. This was because certain chemical reactions in the cell increased the internal resistance and thus lowered the voltage. These reactions reversed themselves when the battery was left idle, so it was only good for intermittent use.
In 1887 Carl Gassner patented a variant of the Leclanché cell which came to be known as the dry cell because it did not have a free liquid electrolyte. Instead, the ammonium chloride was mixed with Plaster of Paris to create a paste, with a bit of zinc chloride added in to extend the shelf life. The manganese dioxide cathode was dipped in this paste, and both were sealed in a zinc shell which also acted as the anode.
Unlike previous wet cells, Gassner's dry cell was more solid, did not require maintenance, did not spill and could be used in any orientation. It provided a potential of 1.5 volts. The first mass-produced model was the Columbia dry cell, first marketed by the National Carbon Company in 1896. The NCC improved Gassner's model by replacing the plaster of Paris with coiled cardboard, an innovation which left more space for the cathode and made the battery easier to assemble. It was the first convenient battery for the masses and made portable electrical devices practical. The flashlight was invented that same year.
The zinc-carbon battery (as it came to be known) is still manufactured today.
In 1899, a Swedish scientist named Waldmar Jungner invented the nickel-cadmium battery, a rechargeable battery that had nickel and cadmium electrodes in a potassium hydroxide solution. It was commercialised in Sweden in 1910 and reached the United States in 1946. The first models were robust and had significantly better energy density than lead-acid batteries, but were much more expensive.
Jungner also invented a nickel-iron battery the same year as his Ni-Cad battery, but found it to be inferior to its cadmium counterpart and consequently never bothered patenting it. It produced a lot more hydrogen gas when being charged, meaning it couldn't be sealed, and the charging process was less efficient (it was, however, cheaper). However, Thomas Edison picked up Jugner's nickel-iron battery design, patented it himself and sold it in 1903. Edison wanted to commercialise a more lightweight and durable substitute for the lead-acid battery that powered some early automobiles, and hoped that by doing so electric cars would become the standard, with his firm as its main battery vendor. However, customers found his first model to be prone to leakage and short battery life, and it did not outperform the lead-acid cell by much either. Although Edison was able to produce a more reliable and powerful model seven years later, by this time the inexpensive and reliable Model T Ford had made gasoline engine cars the standard. Nevertheless, Edison's battery achieved great success in other applications.
Up until the late 1950s the zinc-carbon battery continued to be a popular primary cell battery, but its relatively low battery life hampered sales. In 1955, an engineer working for Eveready (now known as Energizer) named Lewis Urry was tasked with finding a way to extend the life of zinc-carbon batteries, but Urry decided instead that alkaline batteries held more promise. Up until now, longer-lasting alkaline batteries were unfeasibly expensive. Urry's battery consisted of a manganese dioxide cathode and a powdered zinc anode with an alkaline electrolyte. Using powdered zinc gave the anode a greater surface area. These batteries hit the market in 1959.
The first consumer grade NiMH batteries for smaller applications appeared on the market in 1989 as a variation of the 1970s nickel hydrogen battery. NiMH batteries tend to have longer lifespans than NiCd batteries (and their lifespans continue to increase as manufacturers experiment with new alloys) and, since cadmium is toxic, NiMH batteries are less damaging to the environment.
Lithium is the metal with lowest density and has the greatest electrochemical potential and energy-to-weight ratio, so in theory it would be an ideal material with which to make batteries. Experimentation with lithium batteries began in 1912 under G.N. Lewis, and in the 1970s the first lithium batteries were sold.
In the 1980s, an American chemist John B. Goodenough led a research team at Sony that would produce the lithium ion battery, a rechargeable and more stable version of the lithium battery; the first ones were sold in 1991.
In 1996, the lithium ion polymer battery was released. These batteries hold their electrolyte in a solid polymer composite instead of a liquid solvent, and the electrodes and separators are laminated to each other. The latter difference allows the battery to be encased in a flexible wrapping instead of a rigid metal casing, which means such batteries can be specifically shaped to fit a particular device. They also have a higher energy density than normal lithium ion batteries. These advantages have made it a choice battery for portable electronics such as mobile phones and PDAs, as they allow for more flexible and compact design.