Graphene is a two dimensional layer of carbon atoms. That means it is one atom thick. It also means it is so incredibly thin it is transparent. It is also flexible, 200 times stronger than steel and as much as 1,000 times more conductive than copper.
Graphene’s remarkable properties have spurred research in industries as varied as energy, computer technology, medicine, and building materials. And while the potential uses are many, actual commercial applications to date have been few.
So far, commercial uses have been limited to graphene ink for imprinting security tags used in stores, flexible touch screens for mobile devices, and graphene composites in sporting equipment such as tennis rackets, skis, helmets and bicycle tires.
Many researchers believe graphene’s unique and even peculiar properties hold great promise in the fields of medicine and energy. In medicine, graphene is being explored for applications such as a non-invasive imaging and direct deciphering of DNA.
In energy, researchers say the graphene could double the output of photovoltaic cells and, with its conductivity and light weight, revolutionize energy storage.
Companies aim for commercialization
Some companies say they are close to introducing commercially viable graphene storage technologies. Sunvault Energy recently said it could use a graphene storage device at a solar + storage installation in Delaware. And Spanish company Graphenano says it is within months of being able to offer graphene polymer cell batteries with energy densities of 1,000 watt hours/kilogram — about five times the energy density of lithium-ion batteries.
The technologies offer promise, but some analysts are skeptical.
While graphene does appear to have the potential to revolutionize energy storage, the problem is that it is difficult and expensive to produce graphene of sufficient quality in commercial quantities.
Graphene was first isolated in 2004 at the University of Manchester in England, using a piece of Scotch tape and a lump of graphite, the same material found in an ordinary pencil.
That basic method works, but it is very expensive, producing tiny flakes of graphene for about $1,000/gram, which makes it one of the most expensive materials on Earth.
The leading alternative, chemical vapor deposition (CVD), is geared to industrial production and can produce graphene at about $100,000/square meter by depositing methane gas on heated copper substrate and then dissolving the copper. The resulting layer of graphene then has to be deposited on another medium, and it is not completely pure. Any gaps in graphene’s hexagonal atomic structure quickly degrades its conductive properties.
A 2014 article in the journal Nature noted that although CVD is a well established industrial process, it “seems generally unsuitable for mass-production of graphene for electrochemical energy storage because of its high cost, moderate product purity and rather low yield.”
Another extraction method uses chemical, thermal and electrochemical processes to produce graphene oxide (GO) and then make reduced graphene oxide (RGO). RGO has both intrinsic and extrinsic defects, but it the process can produce bulk quantities at lower costs.
While impure, GO has the benefit of being easily dispersed in a wide range of solvents that can be used as either active or inactive components in batteries.
Some academic research says graphene and graphene composites show promise as active components in batteries, but they cannot yet compete with cheaper and well-established activated carbons. In a 2012 article in the journal Small, which focuses on nano and micro technologies, researchers wrote that graphene would probably “fit in the approaching era of small-scale supercapacitors required to power the next generation of wearable- and micro-electronic devices.”
In larger applications, it is likely that graphene, especially graphene composites, will find success in enhancing conventional batteries rather than creating a new class of batteries.
'Graphene gold rush' a bust?
Graphene is also being explored for use in supercapacitors, but that could be an even bigger challenge than batteries. In a supercapacitor, graphene would be the primary material, and there a lot of competing materials in supercapacitor chemistry, says Anthony Vicari, a research associated with Lux Research.
Still, millions of dollars are being poured into what has been called the “graphene gold rush.” Vicari says companies such as XG Sciences and Angstron Materials are furthest along in incorporating graphene, either in nanoplatelets or composites, into energy storage devices.
But there are still barriers that need to be crossed before graphene revolutionizes energy storage. More important than cost of production is the challenge of converting graphene into a useable material, Vicari says. And unless an application can take advantage of graphene’s multiple properties, it will have a tough time competing with existing materials, he says.
Overall, adding graphene to batteries has the potential to improve energy, power, and lifetime by 5% or more, says Cosmin Laslau, senior analyst at Lux Research. “But the industry has done a terrible job of proving that, so there is no consistent apples-to-apples comparison that we are aware of that really proves the potential of graphene”