Many chemical cell reactions take place with release of energy. If this happens in an electrolyte, with one or more of the ionic species in it as participants, it is then possible that the energy released directly and solely increases the electrical potential energy of the ions. The chemical reactions is thus a source of electrical energy. The system can be used as a source of electrical power if the chemical reactions proceeds at a steady rate.  This is what one tries to achieve in an electrochemical cell, or battery. Now in a chemical reaction , the energy released can typically be about 2*10*10*10*10*10  joule per mole.

Daniel Cell