Chinese battery giant CATL is reportedly exploring a new type of air-breathing battery, a so-called lithium-air battery, that could theoretically provide a range of over 1,243 miles (2,000 km) for electric vehicles (EVs).
In addition, these so-called lithium-air batteries could deliver at least five times higher energy density than solid-state batteries. And all of this without putting any additional strain on the technology and, above all, on the electric vehicle.
It’s not all gravy, however. It turns out that lithium-air batteries are exceptionally good at storing energy (at least on paper). However, it turns out that it is very difficult to make them rechargeable, durable and practical.
For the uninitiated, it’s easiest to think of a lithium-air battery as a rechargeable battery that works a little like an internal combustion engine. It removes oxygen from the atmosphere to release energy instead of carrying all the reactive materials inside.
Batteries that breathe
In contrast, a traditional lithium-ion battery has two electrodes that contain materials that store and release energy. Everything it needs is essentially contained in the battery.
A lithium-air battery, on the other hand, does something completely different. They essentially use oxygen from the surrounding atmosphere as one of their reactants. During discharge, lithium metal reacts electrochemically with atmospheric oxygen to produce lithium peroxide (Li₂O₂) and release electrical energy.
This provides the free electrons to power the electric vehicle’s motors and systems during operation. When charging, electrical energy forces the reaction to reverse, decomposing the lithium peroxide, releasing oxygen and restoring the lithium metal.
The big advantage here is that you don’t have to carry the oxygen reactant around in the battery from the start. And this is where the technology’s enormous energy density of 3,505 watt hours per kilogram (Wh/kg) comes from.
Crucially, this is a theoretical number based on its chemistry and oxygen mass. This does not necessarily translate to the actual performance of the battery.
For comparison: a typical conventional lithium-ion cell has an energy density of around 200-300 Wh/kg. Advanced solid-state batteries have an output of 350-500 Wh/kg.
Still experimental, explains CATL
So quite an improvement, at least in theory. A big problem here is that the technology tends to “clog itself”. The lithium peroxide produced is a solid substance that accumulates in the battery’s porous electrode.
It can be compared to a sponge that gradually fills with a solid deposit. Over time, oxygen finds it difficult to penetrate the electrode, reactions become more difficult, and usable capacity decreases.
This should be reversed during the loading process, but the process is not 100 percent effective. Another problem is that air is not just pure oxygen; it contains other gases such as water and carbon dioxide.
Both can affect the chemistry of the battery and result in “contaminating” products that are difficult to remove. To operate at peak efficiency over time, such a battery would likely also need to have a built-in air filtration system.
CATL is not yet claiming that the new technology will revolutionize the industry. It is currently still a long-term exploratory research project. In other words, CATL is interested enough to research it, but has not yet demonstrated that the technology can be commercialized.
