What is a Battery?
A battery is a device that converts chemical energy contained within its active materials directly into electric energy by means of an electrochemical oxidation-reduction (redox) reaction. This type of reaction involves the transfer of electrons from one material to another via an electric circuit.
While the term battery is often used the cell is the actual electrochemical unit used to generate or store electric energy.
In understanding the differences between a cell and a battery, one should think of a battery as one or more of these cells connected in series, or parallel, or both, depending on the desired output voltage and capacity.