An electrochemical cell is a device used for generating an electromotive force (voltage) 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. A common example of an electrochemical cell is a standard 1.5-volt battery. Batteries are composed of usually multiple Galvanic cells.

An electrochemical cell consists of two half-cells. The two half-cells 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 (as in fuel cells which may use hydrogen gas as a reactant). 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 (reduction) from their electrode. A salt bridge is often employed to provide electrical contact between two half-cells with very different electrolytes—to prevent the solutions from mixing. This can simply be a strip of filter paper soaked in saturated potassium nitrate (V) solution. Other devices for achieving separation of solutions are porous pots and gelled solutions. A porous pot is used in the Bunsen cell below (between the electrodes).