|Graphene and the many shapes it can|
be made into
Where are these emissions coming from? More than a quarter of it is produced by transportation. When broken down into the most common modes of transportation, air, rail, road, and water, road transportation is not only the largest offender but is also has the simplest solution in sight. Fairly efficient electric cars are already being developed and are being developed well, with the Tesla Model S being selected by Consumer Reports as the “Best Overall Car” of 2014. Electric cars remove the dependence on fossil fuels from car owners and instead pulls energy from the grid. This means that as power companies switch to renewable energy sources, so do the cars, solving two problems at once. Despite the electric car’s recent appeal, they are being held back by one thing: the battery.
The battery of the tesla Model S, a luxury sedan costing ~$70,000, lasts for an optimal 265 miles on a charge. Under perfect conditions, this charge can be completed with a wall socket in just under 40 hours, a wait far too long for many, especially for that price tag. The more affordable Nissan Leaf only has a driving range of about 70 miles, making it even more impractical for the average commuter. The solution to this problem may lie in the combination of an existing battery technology with a new nanomaterial. Lithium-sulfur batteries can hold more than four times the amount of energy than the currently popular lithium-ion batteries, and their effectiveness was proven in their use to power the longest unmanned airplane flight, lasting 14 days. The only drawback of these batteries is that they traditionally have a short lifespan as the cathode degrades very quickly.
Researchers at Pacific Northwest National Laboratory (PNNL) have discovered a new method of developing lithium-sulfur batteries, allowing them to drastically increase their longevity. Batteries are conventionally made of two parts, an anode and a cathode. A lithium-sulfur battery contains sulfur in the cathode, and although this better stores energy, the sulfur degrades easily. Most research has gone towards preventing the leakage of the sulfur cathode but the researchers at PNNL took a different approach; they used graphite, the same material found in pencils, to shield the anode from the cathode, making the battery’s components more stable. Their efforts lead to the battery being able to recharge over 400 times, much better than the previous 100 especially after such little testing.
Researchers at Tsinghua University in China improved on this result by using the recently discovered nanomaterial, graphene, in an intrinsically unstacked double-layer formation as a cathode material. By producing flakes of graphene, the researchers created a good support structure for the sulfur in the cathode, allowing it to produce in increased power output as well as being able to recharge 1000 times.
Using renewable energy to power electric cars could cut the world’s greenhouse gas emissions by 25%. Although electric cars have been facing problems with battery efficiency, the work of the researchers at PNNL and Tsinghua University has paved the way for drastic improvements in lithium-sulfur batteries allowing for rapid adoption of electric cars in the future.