Many of the electric vehicle blogs that I follow are all buzzing right now over the idea of supercapacitors — well, more accurately, graphene-based supercapacitors, which could potentially solve a few of the issues that EV’s currently face with market adoption.
What’s the big deal? Well with batteries, one can store a great deal of energy in the cells, but the rate of discharge (and the rate of charging) is relatively limited. Capacitors on the other hand have the inverse problem, quick to charge and discharge, the amount of energy that they can hold however, is relatively small.
In theory, supercapacitors have the best qualities of both batteries and capacitors, featuring both high-energy capacities and quick discharge/recharge rates, and in this realm graphene is showing to have very promising results.
Basically a molecule-thin sheet of carbon atoms arranged in a lattice, until recently producing graphene has been a very laborious undertaking, and one that did not scale well for mass production. However, some clever scientists at UCLA have come up with a relatively cheap and easy way to produce graphene sheets, and the technology bodes well for making supercapacitors a more practical solution for electric vehicles.
Allowing vehicles to rapidly charge (as in within a few minutes, instead of hours), supercapacitors solve the great recharge-time issue with EV’s, and would potentially be on par with gasoline vehicles, if not quicker in this regard.
The down side is that graphene supercapacitors are currently about half as energy-dense as the current crop of lithium-ion batteries, which makes them physically cumbersome in applications like on a motorcycle.
That doesn’t mean that the technology is a no-go for automotive use though, as in Formula One and Le Mans, we already see teams using a hybrid supercapacitors/battery strategy, thus creating so-called “superbattery” systems.
Here, energy-dense lithium-ion batteries help feed the power-dense supercapacitors, which then discharge into an electric motor for when extra power is needed by the driver. The process in reverse occurs during breaking, with the kinetic braking force is used to recharge the supercapacitors for their next use.
Already capable of providing the power density required in four-wheel and two-wheel applications, supercapacitors still need to develop a great deal further on the energy-density side of the equation before being a practical replacement for lithium-ion batteries, which themselves are considerably less energy-dense than gasoline.
Cost is another considerable factor, though as the technology develops further both the cost and energy density figures will become more acceptable — interesting stuff.