What is the supercapacitor with the highest energy density

Energy density

The energy density is an important parameter of energy storage and should be limited in the context of IT knowledge to the classic chemical energy storage, the batteries, accumulators, fuel cells and the electrical energy storage, the capacitors and ultracapacitors.


The energy density of these components determines the service life of mobile devices, systems and electric vehicles. In the case of the components mentioned, the energy density refers to the amount of energy related to the volume and weight of the batteries or capacitors, i.e. watt hours (Wh) per volume unit (Wh / ccm) or per weight unit (Wh / kg). In this context, one speaks of energy volume or volumetric energy density and, based on weight, of energy weight or gravimetric energy density. Both energy densities should be as high as possible so that the battery has a high energy density and takes up little space or weighs little. The common form of representation for comparing the energy density of energy storage systems is the Ragone diagram. The energy density parameter is also used in magnets for half the product of flux density (B) and magnetic field strength (H).

The energy density is the mean discharge voltage (V) multiplied by the discharge current (A) and the time (h) until the final discharge voltage is reached, divided by the volume. As far as the energy density is concerned, the values ​​for lithium-ion batteries are up to 200 Wh / kg for lithium-polymer batteries at over 150 Wh / kg and are thus higher than those for NiMH batteries. The energy density of solid-state batteries is around 500 Wh / kg, which is more than twice as high as that of lithium-ion batteries. Compared to batteries, the energy density of fuel cells is 100 Wh / kg to 1,000 Wh / kg and that of supercapacitors is 5 Wh / kg to 30 Wh / kg. The lithium-air battery, which can reach over 10 kWh / kg, has the highest energy density. This value is more than ten times higher than that of a lithium-ion battery.

In addition to the energy density, there is also the specific energy density (Wh / kg) or power density, which refers to the power in watts per unit of weight or volume (W / kg or W / ccm).

Another performance parameter of batteries is the specific power (W / kg), at which the power is related to the weight until the discharge voltage is reached. It is calculated from the mean discharge voltage (V) multiplied by the discharge current (A) and divided by the weight (kg).