I first learned of graphene in early 2012 while researching the status of carbon nanotube commercialization. At that time, CNTs were the darlings of science and technology with seemingly endless possibilities. Since that time however, graphene, a sheet of carbon one atom thick, has apparently supplanted CNTs as one of the most hyped materials to solve far-reaching problems. Graphene is likely at the “peak of inflated expectations” in Gartner’s Hype Cycle. Among those many expectations is the considerable promise this material offers to resolve a number of lingering limitations with electric vehicles. The allure of graphene is its multitude of intriguing properties ranging from its near resistant-free conductivity and ability to attach to a wide variety of molecules to its incredible strength and transparency. These make it an excellent candidate for improving vehicle energy storage, onboard electronics, and body materials. Let’s explore some of these possibilities.
Graphene oxide has been combined with sulfur as a cathode in prototype Lithium Sulfur Graphene batteries at Lawrence Berkley National Laboratory. For awhile now, lithium sulfur (Li-S) has been considered a superior battery combination than today’s lithium ion (Li-ion) in terms of energy density (specific energy, actually) but suffered from deterioration after only a dozen or so recharging cycles. Combining the graphene oxide with the sulfur seems to have resolved that issue and now provides over 1,500 cycles; a 50% improvement over Li-ion. Li-S batteries hold promise to provide over twice the energy density of Li-ion and extend driving range to over 300 miles on a single charge. Tesla has been rumored to be pursuing this as a means to extend driving range to as much as 500 miles.
Graphene also holds promise for improvements in supercapacitor performance. Supercapacitors are also storage devices but, in many ways, perform exactly the opposite of batteries. They charge and discharge very quickly with high power density but low energy density. Though currently more expensive than batteries, they do not deteriorate over many charging cycles. What makes them intriguing is the possibility to combine them with batteries; using their burst of energy output to accelerate the vehicle and then quickly recharge them using the vehicle’s regenerative braking. This would spare the battery from its biggest energy drain and then only be needed to sustain the vehicle’s momentum and power the rest of the car.
Lower Power Electronics
The excellent conductivity of graphene makes it a possible candidate to replace silicon as the reigning king of electronics. A fair amount of energy used in today’s electronics ends up as waste heat due to the resistant inherent in silicon circuits. The lower resistance of graphene represents an estimated energy savings of as much as 50% according to some credible researchers. As I’ve mentioned on several occasions, extending electric vehicle driving range cannot be focused exclusively on battery technology.
Lighter Vehicle Body Parts
The strength of carbon in its many allotropes including graphene is well documented. This makes it attractive for use as material for several components that make up the vehicle body as they would be quite a bit lighter than steel. Ford just obtained a nifty $6 million of the $55 million DOE has allocated to advanced vehicle efficiency technology to research carbon fiber as part of an overall goal to reduce vehicle weight by 30%. Researchers have been investigating the use of graphene oxide among other materials to provide carbon fiber of superior strength. Here again is an opportunity to increase driving range irrespective of battery improvements.
Graphene obviously holds a lot of appeal to solve several EV challenges and maybe even some of the world’s other most insidious problems. We’ll see how this shakes out as graphene moves through the rest of the Hype Cycle but several important questions come to mind now. While production capacity is probably not going to be a issue given the amount of graphene that is likely required, the cost of graphene may be the bigger concern. Health safety may be another big concern. While graphene is biodegradable, there are likely issues of toxicity, especially since it is easily transportable by water. This was also a concern expressed regarding the application of CNTs. Another noteworthy concern is that graphene may face some stiff competition from hemp as time goes on but that’s a discussion for another day.