Batteries and capacitors both of them are being used to store electric charges but their storing mechanism is completely different from each other.
Batteries have two electrical terminals (Positive and Negative) separated by chemical materials known as electrolytes. When you switch on the circuit of the battery then stored chemical energy inside the battery gets converted into electrical energy. Once the chemicals have all been depleted, the inside reactions stop and the battery is discharged. In a rechargeable battery, such as Lithium-ion, the inside reactions can happily run in either direction. So you can usually charge and discharge hundreds of times before replacing it.
Capacitors are a little bit different from batteries. They use static electricity to store energy. Inside a simple electrolytic capacitor, there are two conducting plates with insulating material between them. In the simple view, you can say that a dielectric or insulating material has been placed between two metallic plates. When potential or voltage has been applied across these two metallic plates then positive and negative charges build up across the dielectric material. This material allows a capacitor of a certain size to store more charges at the same voltage, so that dielectric material makes the capacitor more efficient as a charge-storing gadget like a battery.
Super-capacitors are quite different from ordinary or simple electrolytic capacitors. How? Let’s know about this.