The big difference is that capacitors store power as an electrostatic field, while batteries use a chemical reaction to store and later release power. Inside a battery are two terminals (the anode and the cathode) with an electrolyte between them. An electrolyte is a substance (usually a liquid) that contained ions.
The introduction of battery-type materials into the positive electrode enhances the energy density of the system, but it comes with a tradeoff in the power density and cycle life of the device. Most of the energy in this system is provided by the battery materials, making it, strictly speaking, a battery-type capacitor.
It can be inferred from the graph that the capacitors have high specific power and low specific energy, while the opposite is true for batteries and fuel cells. Ragone plot of various energy storage devices (redrawn and reprinted with permission )
Capacitors exhibit exceptional power density, a vast operational temperature range, remarkable reliability, lightweight construction, and high efficiency, making them extensively utilized in the realm of energy storage. There exist two primary categories of energy storage capacitors: dielectric capacitors and supercapacitors.
Batteries can store substantial energy in small volumes but are limited in instantaneous power output capabilities. Supercapacitors occupy an intermediate niche, bridging the conventional capacitors and battery domains. They provide higher energy densities than conventional capacitors while retaining exceptionally high-power densities.
1. Three packs of supercapacitors (in the blue package), consisting of six D-size cells were able to provide and store the same amount of electrical energy as the smaller pack of six AA-size TLI 1550 Li-ion rechargeable batteries. Batteries and capacitors seem similar as they both store and release electrical energy.