Thibaut Lalire - PhD student in materials science, IMT Mines Alès – Institut Mines-Télécom
"Material of the 21
st century," "revolutionary material," this is how graphene has been described since its discovery in 2004 by Konstantin Novoselov and Andre Geim. The work on graphene by these two scientists earned them the
2010 Nobel Prize in Physics, but what's the status 17 years after this breakthrough?
Flexible, strong, and with unusual electrical and electronic properties, graphene has many advantages in the lab, but applications are struggling to materialize.
Image Wikimedia
Graphene is globally renowned for its remarkable properties, whether mechanical, thermal, or electrical. Its perfect honeycomb structure composed of carbon atoms is why graphene excels in many fields. Its morphology—formed as a sheet only about one atom thick—allows it to belong to the family of 2D materials.
Since its discovery, industries have intensified research on the material. Various applications have emerged, particularly by harnessing graphene's electrical performance. Several sectors, such as aerospace, automotive, and telecommunications, are being targeted.
Is graphene present in airplanes?
Graphene is prized not only for its status as a champion of electrical conductivity but also for its low density and flexibility. These properties have earned it a place in the
exclusive club of materials used in the aerospace sector.
Lightning strikes and ice accumulation on the fuselage are common challenges faced when airplanes are at high altitudes. The impact of lightning on a non-conductive surface can cause severe damage, even leading to the aircraft catching fire. Adding graphene, thanks to its high electrical conductivity, helps dissipate this high-energy current. Aircraft are designed in such a way as to channel the current as far away as possible from high-risk areas, such as fuel tanks or control cables, to avoid losing control of the aircraft or even explosion.
The history of graphene begins here.
Umberto/Unsplash, CC BY
A coating made of resin reinforced with graphene, called a "nanocomposite," is used as a substitute for metallic coatings. Its low density allows for lighter materials than the originals, reducing the aircraft's weight and thus its fuel consumption. Electrically conductive materials required to dissipate lightning energy usually suffer the drawback of reflecting electromagnetic waves, making them unsuitable for stealth applications in the military sector.
To overcome this limitation, different forms of graphene have been developed to preserve its electrical conductivity while enhancing its stealth properties. "Graphene foam" is one such new structuring. Electromagnetic waves penetrate the material, and a phenomenon of reflections within the material in all directions gradually traps and attenuates the waves. No wave returns to the radar, rendering the aircraft effectively undetectable—a phenomenon known as "electromagnetic shielding."
Graphene for energy storage
Graphene has also found substantial use in the field of
electrical energy storage.
Graphene is an ideal candidate as an electrode for Li-ion batteries and supercapacitors. On one hand, its electrical conductivity is high; on the other, its high specific surface area (relating to the surface area available on the graphene to host ions and facilitate electron exchange between the graphene electrode and lithium) results in a large "storage capacity."
Indeed, many ions can easily insert themselves between the graphene sheets, enabling more electrons to exchange with the current collector, thereby increasing the electricity storage capacity and consequently the battery's autonomy. The ease with which ions insert into the graphene electrode and the material's high electrical conductivity (for faster electron transfer) enable significantly shorter charge/discharge cycles for the
battery.
Graphene's high conductivity allows for the release of a large amount of energy in a very short time, thereby increasing the power of supercapacitors. Additionally, graphene is an excellent thermal conductor, minimizing battery heating by dissipating heat.
Electric batteries are now omnipresent in modern life. Graphene could enhance their performance.
Markus Spiske/Unsplash, CC BY
At the industrial scale, there already exists an external battery developed by Real Graphene, capable of fully charging a smartphone in just
17 minutes. In a completely different domain, Mercedes is working on a prototype car with a graphene-electrode battery, claimed to feature a
700-kilometer range (approx. 435 miles) with a 15-minute recharge. At present, these figures seem astonishing, especially for electric vehicles requiring high-capacity batteries.
Finding its place in electronics
Where graphene currently struggles to stand out compared to semiconductors is in the
field of electronics.
Its electronic properties—due to its "band structure"—make controlling electrons impossible, causing graphene to behave like a semi-metal. As a result, using graphene in binary (digital) electronics remains challenging, particularly for transistors, which are typically made of semiconductors.
To use graphene in a transistor, its band structure must be modified, often degrading its honeycomb structure and its other electrical properties. To preserve its 2D structure, the chemical nature of the atoms making up the material must be altered—for example, by using boron nitride or transition metal dichalcogenides, which are also part of the
extensive family of 2D materials.
Microscopy of the interface between graphene and boron nitride (h-BN).
Oak Ridge National Laboratory, Flickr, CC BY However, if graphene is to be used, applications requiring mechanical properties (such as flexibility) are preferable—for example, in sensors, electrodes, and certain transistors reserved for analog electronics, such as
graphene field-effect transistors. Major phone manufacturers are also developing flexible smartphone screens for better ergonomics.
The
construction of future quantum computers might rely on materials known as "topological insulators." These materials are electrically conductive on their surfaces but insulating in their cores. Current research is focusing on the topological phase of graphene, with electrical conduction only occurring along its edges.
The diversity of graphene applications highlights the vast potential of this material, paving the way for new advancements in fields such as
optoelectronics and spintronics.
This material has already proven itself in industrial contexts, albeit without revolutionizing them as of yet. However, ongoing research continues to uncover new fields of application annually. Simultaneously, synthesis methods are being constantly developed to reduce the cost per kilogram of graphene while producing higher-quality material.