Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor, and which involve electron transfer between the electrode and the electrolyte or species in solution.
A process of this kind can always be represented, as a chemical reaction and is known generally as an electrode process. Electrode processes take place within the double layer and produce a slight unbalance in the electric charges of the electrode and the solution. Much of the importance of lies in the ways that these potential differences can be related to the thermodynamics and kinetics of electrode reactions. In particular, manipulation of the interfacial potential difference affords an important way of exerting external control on an electrode reaction. The interfacial potential differences which develop in electrode-solution systems are limited to only a few volts at most. This may not seem like very much until you consider that this potential difference spans a very small distance. In the case of an electrode immersed in a solution, this distance corresponds to the thin layer of water molecules and ions that attach themselves to the electrode surface, normally only a few atomic diameters. Thus a very small voltage can produce a very large potential gradient.
Chemistry and electricity are linked. Atoms are made of nucleus and negative charged electrons. An atom is normally electrically neutral. Atoms can lose or gain electrons to form charged ions. Discharge of ions involves loss or gain of electrons. There are two types electric charge: positive and negative. The flow of electric charge in a conductor is an electric current. There will only be an electric current in a conductor when there is a potential difference across the conductor. It is measured in volts. Chemical reactions may be used to produce potential differences-electric current. These reactions are the basis of voltaic cells. Electricity is involved in the production of some chemicals by electrolysis.
An electrochemical cell is a device used for generating an electromotive force and current from chemical reactions, or the reverse, inducing a chemical reaction by a flow of current. The current is caused by the reactions releasing and accepting electrons at the different ends of a conductor. An electrochemical cell consists of two half-cells, it may use the same electrolyte, or they may use different electrolytes. Each half-cell consists of an electrode, and an electrolyte. The chemical reactions in the cell may involve the electrolyte, the electrodes or an external substance. In a full electrochemical cell, ions, atoms, or molecules from one half-cell lose electrons (oxidation) to their electrode while ions, atoms, or molecules from the other half-cell gain electrons.

An 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. The cell potential can be predicted through the use of electrode potentials. The difference in voltage between electrode potentials gives a prediction for the potential measured.
Cell potentials have a possible range of about zero to 6 volts. Cells using water-based electrolytes are usually limited to cell potentials less than about 2.5 volts, because the very powerful oxidising and reducing agents which would be required to produce a higher cell potential tend to react with the water. An electrical cell is a device that is used to generate electricity, or one that is used to make chemical reactions possible by applying electricity.