What is the comparison between capacitor and battery?

A Capacitor stores charge using a pair of parallel plates with an insulating material known as the dielectric separating them. When a current is applied to the capacitor, the electrons can't cross the dielectric so they build up on one side and leave the other, meaning the plates become charged. When the current is removed, the electrons flow back and the charge is reduced. The speed at which they do this is dependant on the size of resistor in the circuit.

A Battery (Cell) creates its own current through chemical reactions. There are two parts to a cell, each known as a half cell. Each half cell consists of an electrode, which is immersed in a solution. Copper and Zinc are common metals used for the electrodes. The solutions are usually made of the same substance in a compound which dissociates; the copper electrode would be immersed in, for example, a copper sulphate solution. An equilibrium is then established between the copper electrode and the dissociated copper ions, with the electrons flowing into the other half cell, creating a potential difference. This circuit is completed by a link between the two substances known as a salt bridge.

Capacitors are useful for fast charge storage over a short time period, though the rate at which they discharge is exponential. Batteries are useful for providing a slow, steady flow of electrons for much longer periods of time.

Hope this helps!