This toothpaste component could make the batteries of your electric car last longer

If I mention fluorine, you will surely first think of toothpaste. Indeed, this chemical element, obtained by processing the mineral fluorite, is used to make toothpaste, as it helps prevent cavities. However, it is not its only use: fluorine is also used, for example, to purify water, to manufacture anaesthetics, in lighting systems, and to build refrigeration systems… And it could soon become a key element in the manufacture of batteries for electric cars.

It all stems from research carried out by the Chemical Sciences and Engineering division of the Argonne National Laboratory, the first national research laboratory for science and engineering in the United States, based in Illinois. Here, researchers have discovered an application of the very same fluorine that protects your tooth enamel, so that electric car batteries last much longer.

How a lithium battery works

To better understand what fluorine can do when applied to battery manufacturing, let us review how a lithium battery works. All of them have the following elements: anode or negative electrode, cathode or positive electrode, and electrolyte, which acts as a separator between the two and allows lithium ions to flow from the anode to the cathode, creating a potential difference that produces the electric current.

In the constant search for alternative chemistries that allow batteries with higher energy density to be manufactured, the solution seems to lie in batteries with lithium metal anodes instead of the usual graphite; in these batteries, the cathode is made of a metal oxide that normally contains nickel, cobalt and manganese. But the problem is that the high energy density offered by this type of battery decreases rapidly as it is repeatedly charged and discharged, as the anode degrades as a result of the solvents and salts contained in the electrolytes.

Fluorine against cavities… and to protect the battery anode

What Argonne researchers have discovered is that replacing the hydrogen atoms in the electrolyte with fluorinated components significantly improves the internal operation of the battery, by forming a protective layer on the electrodes that allows the number of charge and discharge cycles to increase while maintaining high performance, thereby extending its lifespan. Specifically, a new fluorinated solvent formed by positive and negative ions is used.

So far, simulations run on a supercomputer reveal that the fluorinated component adheres to and accumulates on the surfaces of the anode and cathode during the battery’s charge and discharge cycles, forming a protective layer that is suitable and highly resistant compared with what is possible with conventional electrolytes. The key is to perfectly adjust the proportion of fluoride solvent to lithium salt so that this protective layer is neither too thin nor too thick, and allows lithium ions to flow efficiently between the electrodes during charging and discharging over hundreds of cycles. This does not seem likely to be a problem.

In addition, as further advantages, the new fluorine-based composite electrolyte is low cost because it can be manufactured in a single step with high purity and yield, it requires fewer solvents than traditional electrolytes, with the environmental benefit that this entails, and it is safer because it is not flammable.

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