A device containing two conducting
electrodes, one positive and the other negative, made of
dissimilar materials (usually metals) that are immersed in a
chemical solution, known as an electrolyte, that transmits
positive ions from the negative to the positive electrode and
thus forms an electrical charge. One or more cells constitute a
battery.
An extremely important class of oxidation and reduction
reactions are used to provide useful electrical energy in
batteries. A simple electrochemical cell can be made from copper
and zinc metals with solutions of their sulfates. In the process
of the reaction, electrons can be transferred from the zinc to
the copper through an electrically conducting path as a useful
electric current.
An electrochemical cell can be created by placing metallic
electrodes into an electrolyte where a chemical reaction either
uses or generates an electric current. Electrochemical cells
which generate an electric current are called voltaic cells or
galvanic cells, and common batteries consist of one or more such
cells. In other electrochemical cells an externally supplied
electric current is used to drive a chemical reaction which
would not occur spontaneously. Such cells are called
electrolytic cells.
