Quantity of energy able to be stored in a battery

What is the energy density of a battery ?

For a battery, energy density refers to the quantity of energy able to be stored and restored during the operation of the equipment.

Useful to know:

Energy density is a physical concept used to measure the energy able to be stored in a material or a device: this can be a battery or a superconductor, but also a liquid fuel such as petrol or a solid fuel such as coal, or even a radioactive element such as tritium, uranium or plutonium...

Energy density is expressed by unit of mass or based on volume.

We distinguish between the following:

  • mass energy density expressed in Wh/kg ;
  • volumetric energy density usually measured in J/m3: this indicator is more suited to fuels such as hydrocarbons.

For batteries, energy density is usually given as a function of mass, that is to say in Wh/kg.

Energy density of a battery: details

The energy density of batteries depends on the technology used.

Depending on the components and electrochemical reactions in question, we talk about lead, nickel-cadmium (NiCd), nickel-metal hydride (NiMH), lithium-ion (Li-ion), lithium-polymer (Li-Pol), sodium-sulfur (Na-S) batteries...

Examples and application

Depending on their energy density, batteries can serve the operation of different devices, or be allocated to different uses: mobile phones and laptops, cameras, portable tools, light electric or electric road vehicles...

In this area, technologies are constantly evolving to provide the best possible autonomy.

The energy density of batteries in numbers

With energy density of 0.027 7 kWh/kg, lead batteries are able to start a combustion engine vehicle.

Electric vehicles usually use lithium-ion (Li-ion) accumulator batteries which have a much higher energy density: around 0.2 kWh/kg.