Battery

A battery is a device that stores chemical energy and is converted into electricity, making them small chemical reactors. The earliest battery was discovered in 1938 by the Director of the Baghdad Museum and was dated around 250 BC and of Mesopotamian origin. The most common and enduring batteries is the lead-acid battery, invented in 1859 and still used in the majority of internal combustion engine automobiles and is the oldest example of rechargeable batteries.

The term battery was used in 1749 by Benjamin Franklin during his experiments with electricity using a set of linked capacitors. The first battery as understood by modern usage was developed in 1800 by Italian physicist Alessandro Volta. The battery comprised of stacked discs of copper and zinc separated by cloth soaked in salty water produced a stable continuous current of electricity, a stable current of 0.76 Volts.

The standard construction of a battery follows Volta's early example in using two metals or compounds, the anode and cathode, with different chemical potentials and separating them with a porous insulator. The chemical potential is then imparted to moving electrons which are allowed to move through the connected external device. The conducting fluid used to transfer soluble ions from one compound to the other during the reaction is called an electrolyte.

Primary batteries are the most common type of battery, which produces a flow of electrons which cannot be reversed and leaves the battery flat. Of these, the zinc-carbon battery, or alkali battery, are the most common type.

Rechargeable batteries, the earliest example being the nickel-cadmium battery, allow the battery to be electrically recharged after use. The early types of rechargeable batteries, nickel-cadmium and nickel-metal hydrogen are both sensitive to over-charging and over-heating during charge, and therefore their charge rate is controlled below a maximum rate resulting in slow charge rates.

Lithium-ion batteries present an advantage over these. Lithium is one of the lightest elements on the periodic table with one of the largest electrochemical potentials, offering a battery that is lightweight and compact with higher voltages than traditional rechargeable batteries. In lithium-ion batteries, the lithium is combined with a transition metal, such as cobalt, nickel, manganese or iron, and oxygen. Originally developed in 1980 by American physicist Professor John Goodenough, the lithium-ion battery was improved in 1990s by the introduction of a stable lithium-ion cathode based on lithium iron and phosphate. This meant the cathode was thermally stable and the new materials can be made safely into large format cells that can be rapidly charged and discharged.