The electric car: how does its lithium-ion battery work?

Published by on 10.18.2019 - 3 min

The lithium-ion battery has established itself as the technology of reference in the world of electric cars. How does it work and what are its qualities? Read on to find out.

First commercialized in 1991, the lithium-ion battery was initially created for the consumer electronics sector. It quickly lent itself to further applications, eventually becoming standard for all devices requiring a portable rechargeable battery. It superseded nickel cadmium (NiCd) and nickel-metal hydride (Ni-MH) technologies.

The operation of a lithium-ion battery

The principle behind the lithium-ion battery is to circulate electrons by creating a difference in potential between two electrodes, one negative and the other positive, that are immersed in a conductive ionic liquid called the electrolyte. When the battery is powering a device, the electrons accumulated in the negative electrode are released via an external circuit to travel to the positive electrode: this is the discharging phase. Conversely, when the battery is charging, the energy supplied by the charger sends the electrons back from the positive electrode to the negative.

The different battery types  vary by ion types, electrode materials and the associated electrolytes. The 12-volt lead-acid battery that has traditionally been used to power the starter of a combustion-engine vehicle, for example, relies on an electrolyte containing lead ions and electrodes that are lead-based. As for the lithium-ion battery, it uses lithium ions (Li+): hence the name given to this technology.

A lithium-ion battery such as the one inside a car like the ZOE is designed as an assembly of individual battery units (cells), connected to each other and monitored by a dedicated electronic circuit. The number of cells, the size of each cell and the way in which they are arranged determine both the voltage delivered by the battery and its capacity, meaning the amount of electricity it is able to store. This is generally stated in watt-hours (Wh), or in kilowatt-hours (kWh) in the automotive industry.

The properties of a lithium-ion battery

ZE 50 Battery

Lithium-ion batteries can just as well be found in consumer electronics (telephones, laptops) as in electric cars. The main reason for this large-scale success essentially lies in the storage density that lithium-ion technology allows for.

This concept of density refers to the ratio between the storage capacity  offered by the battery and its bulk or weight. By way of comparison, a lithium-ion battery offers a density of around 300 to 500 Wh/kg, i.e. some ten times more than a lead-acid battery.

While we await the potential development of innovations like the solid-state battery , lithium-ion technology today represents the best compromise between capacity, volume and mass in the electric mobility sector. It offers high voltage, easy recharging and durability, which lend themselves to usage scenarios that complement each other throughout its life cycle, in line with the principles of the circular economy.

Copyrights : Pagecran, Olivier Le Moal

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