Will Graphene Replace Lithium-Ion Batteries Before eVTOLs Take Off?
All the talk we’ve seen thus far in the eVTOL community that’s focused on the vehicle’s electric power source has been about lithium-ion. Lithium-ion batteries, it’s believed, have the properties eVTOLs will need to be commercially successful. They can generate the power necessary for vertical lift, achieve the speeds needed to be practical, have the longevity air taxis will require for profitability, and can charge and recharge relatively quickly.
What if there were another natural material that was capable of all those things but was cheaper, lighter, held a charge longer, and was easier to extract from the Earth? Some scientists say that material already exists. It just needs more attention and investment. That material is graphene, a variant of graphite, the same stuff people have used in pencils since graphite was first discovered in England in 1564.
Graphene Battery: Thick-skinned, Thin Profile
A graphene battery holds more power than a lithium-ion battery. It’s rapid-charging. And, it could propel a conventional automobile about 300 miles on a single charge.
Graphene is a sheet of carbon that’s a single atom thick.
In lab tests performed by NanoGraf, a Chicago, Illinois-based graphene battery developer, the company claims its graphene batteries run 50 percent longer than lithium-ion, produce a 25 percent lower carbon footprint, and weigh half as much as lithium-ion batteries. As an eVTOL developer, operator, or passenger, what’s not to like?
Unlike lithium alone, which is a comparatively poor conductor of electricity and deforms when discharging, a lithium battery coated with graphene will conduct electricity more efficiently, keep its shape, and last longer.
Over the course of decades, battery makers came to embrace lithium over silicon because it has a high electrical capacity. But lithium has two key problems: It conducts electricity poorly and tends to physically deform as it discharges, ultimately shearing and cracking. Mixing or coating the lithium with graphene — or, more recently, related nanomaterials like graphene oxides and reduced graphene oxides — solves both issues. Graphene is highly conductive, allowing electricity to flow, and rigid, so it helps the lithium keep its shape, allowing the battery to last longer.
Is Graphene Ready to Fly?
Christos Athanasiou, a postdoctoral researcher in engineering at Rhode Island’s Brown University, explained in his paper, “High-Toughness Inorganic Solid Electrolytes via the Use of Reduced Graphene Oxide,” published in the scientific journal, Matter, that because of graphene’s high electronic conductivity, if you add it to a silicon anode, the conductivity rate improves dramatically.
It’s also a strong material – about 200 times stronger than steel. That strength can help prevent a silicon anode from expanding and breaking. Nearly transparent, it absorbs just 2 percent of light, making it impermeable to atmospheric gases, such as hydrogen or helium.
Graphene’s nature is such that you can place it on the materials you want and vice versa. “There is a real beauty in its simplicity,” explains Vincent Bouchiat, research director at the Institut Néel in Grenoble, Switzerland, a division of the National Centre for Scientific Research (CNRS).
Graphene’s durability will likely yield additional lifecycles compared to traditional batteries. That could give them a longer useful life than the lithium-ion batteries under development now. Given the testing timelines, it may be three or four years before graphene batteries are ready for prime time. But, once they are… who knows, the sky’s the limit.
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