ENCYCLOPEDIA OF THE BATTERIES
The energy density describes the amount of energy that can be stored in a battery per mass or per volume.
Thus, the amount of energy per kg (Wh/kg) or the amount of energy per liter (Wh/L).
There is a “volumetric energy density“, short “energy density” and a specific energy density also known as gravimetric energy density.
Some people call the energy density in short as “Energy” like the “specific energy”. However, this can be confusing as the energy in physics is a “state” and not a density.
Products that require long run times at moderate loads are optimized for high-energy density; the ability to deliver high current loads can be rather neglected. Electric cars require lithium-ion batteries with a high-energy density, since a passenger car usually wants to drive for a long time at a constant rate.
For electric cars, volumetric energy density is more important than specific energy density because battery space is limited. For electric aviation and aviation in general, the specific energy density is relevant because gravity has to be overcome constantly.
The energy density of a battery pack often is specified in e-car marketing.This figure takes into account all the components of a battery pack. This energy density of the “battery pack” is useful for the end user because this energy density is also effectively used in an electric car or other device. The high-energy density in LIB battery packs is responsible, among other things, for the good environmental balance in passenger cars.
In development and in the trade, the energy density of the “bare cell” is often specified. This is higher than the energy density of the battery pack because “inactive battery components”(components which do not hold energy) such as a BMS, metal components, sealing materials, adhesives, thermal pastes and insulation materials that do not store energy are not included in the energy density.
The following components are included here: active electrode materials, conductor films, electrolytes, separator, and a simple cell envelope.
The highest energy density is usually given by researchers who investigate and develop a specific material. Here, for the most part, only the mass of the ACTIVE electrode material under investigation is considered (without additives, electrolytes, separator, and active counter-electrode).
This is justified, since in science one wants to investigate and compare individual materials.
However, for the researchers and readers of the research results, it is necessary to always describe exactly which cell components were considered in calculations for energy density, power, and capacity.
Science for Dummies
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