Thursday, January 28

How do electric car batteries work?

The lithium-ion battery has gradually established itself as the benchmark technology and electric cars are no exception. But its functioning and its composition can still seem rather abstract. The opportunity to expand on the subject.

Battery Renault Zoé

Here’s how electric car batteries work.

How are electric car batteries made?

Contrary to what one might think, electric cars did not appear ten years ago at the instigation of the legislator. Long before the advent of the thermal car, some had already looked at the electric car. By the way, for the record, the first car to have exceeded 100 km / h is not a thermal model, but an electric model, “The never content”, in 1899. A car powered by an electric block powered by a lead-acid battery, a type of battery that we no longer find in our modern cars today, at least to provide traction.

Lead-acid batteries are now used simply to supply the electrical circuit of accessories or equipment specific to the thermal world such as the starter for example. Why are they not used on our electric cars? Quite simply because it offers only a limited capacity despite a size and a fairly significant weight.

However, this type of battery at least has the merit of being both economical and easy to produce or recycle. If they are still used in modern combustion cars, they obviously no longer need to be in our current electric cars. that use much more efficient storage devices. The fact remains that the lead-acid battery powered some electric cars until the 1980s, or even the 1990s with the EV1 from General Motors or the electric Citroën AX.

The never happy

The never happy, the first car to have reached the 100 km / h mark.

What are the components of a battery?

With regard to the batteries of our modern cars, there is no longer any question of hearing about lead-acid batteries, since they all use lithium-ion batteries. The lithium-ion battery is no longer very young since it was marketed from 1991 by Sony. It was primarily intended for the consumer electronics sector. Quickly, because of its capabilities, it intrudes into new devices requiring a rechargeable and portable battery.

How does a lithium battery work?

The principle of operation of a lithium-ion battery is quite simple in itself. It consists to circulate electrons by creating a potential difference between two electrodes, one negative and the other positive, immersed in an ionic conductive liquid called the electrolyte. When the battery powers an element, in this case an electric motor for our cars, the electrons accumulated in the negative electrode are released through an external circuit to join the positive electrode. This is called the discharge phase.

If there is a discharge phase, there is quite logically also the reverse: the charging phase. This is the action performed when you charge your battery, the energy transmitted by the charger makes the electrons of the positive electrode return to the negative.

But why are these batteries called “lithium-ion”? On the same principle of the lead-acid battery, it is obviously from the technology used that the battery gets its name. The different types of batteries vary depending on the type of ions, the electrode materials and the associated electrolyte. For example, in a lead-acid battery, we find an electrolyte containing lead ions and lead-based electrodes. In a lithium-ion battery, we find lithium ions (Li +).

What are the components of a lithium battery?

The lithium-ion battery that makes up our current vehicles is presented as an assembly of individual battery units also called cells. These cells are connected to each other and supervised by an electronic circuit. They are obviously decisive since their number, the size of each cell and the way in which they are arranged determine both the voltage delivered by the battery and its capacity. The capacity being the quantity of electricity that it is able to store. This is the data expressed in kWh in the automotive world.

Today, we find these lithium-ion batteries in many consumer electronic devices such as our phones or our laptops.

This success lies mainly in the storage density allowed by the technology. The density which corresponds to the ratio between the storage capacity offered by the battery and its size or weight. To compare the technological advances made since the lead-acid battery, know that a lithium-ion battery offers a density of around 300 to 500 Wh / kg, about ten times more than that of a lead-acid battery.

The Volkswagen ID battery pack.  Vision

On virtually all modern electric cars, the batteries are located under the floor.

In which cars can we find a lithium-ion battery?

As stated above, in virtually all electric cars on the market today. Thus, the Tesla Model 3, Model S, Model X and the next Model Y are equipped with a lithium-ion battery, just like the Renault Zoe, the Nissan Leaf e +, the Peugeot e-208, the Honda e or the DS 3 Crossback E-Tense.

For the moment, lithium-ion technology still seems to have a bright future, especially with the proliferation of electric cars within the ranges of manufacturers. It is indeed the best compromise between capacity, mass and volume. in a sector where, obviously, all these criteria are essential.

Other types of batteries could nevertheless replace the lithium-ion battery in the more or less long term. Among the most credible, we can cite solid electrolyte battery, which therefore replaces the liquid electrolyte with a solid material which can take the form of a polymer or powders similar to a kind of ceramic. The advantage of switching to a solid electrolyte would obviously be to theoretically eliminate the drawbacks linked to the use of a liquid electrolyte, but we will have to wait a few more years before a probable democratization of technology.

What is the lifespan of an electric car battery?

First of all, know that the life of a battery is expressed in cycles: a cycle is simply a charge and a discharge. Renault estimates for example that depending on the type of lithium-ion battery, the number of cycles is between 1000 and 1500. That is to say an endurance of 20 years for a Zoe traveling about 30 kilometers per day, by way of example. On average, a battery should last less.

Obviously, the more or less intensive use of your electric vehicle will necessarily affect the longevity of the battery, while its efficiency will also drop over the years. For its part, Tesla guarantees the battery of its connected cars for eight years. A period of time that could give us a little idea of ​​its lifespan, although it will be necessary to wait several more years to get a real opinion on the matter, with the necessary hindsight.

Also, technologies are not immune to evolve to make our batteries more robust in the future.

How to recycle electric car batteries?

As you can imagine, the production of these batteries does not have a completely neutral impact, the use of lithium-ion batteries has already raised many controversies, including environmental problems due to the extraction of lithium or the recycling of these batteries.

Environmental issues

The battery of an electric car contains several kilos of lithium, but also cobalt and manganese, among others. These three elements are metals, all extracted and processed to then be used in batteries. More than two-thirds of lithium resources come from the salt deserts of South America, mainly Bolivia, Chile and Argentina.

Several studies have already shown that the extraction and processing of these metals lead to soil pollution, the drying up of rivers, and can also lead to an increase in poisoning and serious illnesses for local populations. Cobalt, which is also needed for lithium batteries, more than half of the world’s production comes from Congolese mines. Mines which do not necessarily respect the security conditions and which are also singled out for the exploitation of children.

As with thermal cars and hydrocarbon extraction conditions, the electrical sector still has work to do. Nevertheless, the advancement of technology suggests new alternatives to these materials, just like how to extract or process them.

What about recycling?

Until recently, lithium was hardly recycled for three reasons: its high availability, low extraction cost and low collection rate. However, with a growing fleet of electric cars and tensions over supplies, the situation has changed and the recycling sector is being set up.

Obsolete electric vehicles, which are few in number compared to combustion vehicles, are almost entirely dismantled and the end-of-life battery elements such as lithium, cobalt, aluminum or even copper are collared and recycled. There are also other solutions for undamaged batteries, giving them a second life and using them for stationary use. Thus, they can be used to store renewable energies or even supply fast charging stations.

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