A supercapacitor can store far more electrical energy than a standard capacitor. They are able to charge and discharge far more rapidly than batteries, making them a much-discussed alternative to traditional batteries.
The main drawback of supercapacitors as a replacement for batteries is their limited storage: while they can store 10 to 100 times more electrical energy than a standard capacitor, this is still not enough to be useful as a battery replacement in smartphones, laptops, electric vehicles and other machines.
At present, supercapacitors can store enough energy to power laptops and other small devices for approximately a tenth as long as rechargeable batteries do.
Increases in the storage capacity of supercapacitors could allow for them to be made smaller and lighter, such that they can replace batteries in some devices that require fast charging and discharging.
A team of engineers at the University of Waterloo were able to create a new supercapacitor design which approximately doubles the amount of electrical energy that it can hold.
They did this by coating graphene with an oily liquid salt in the electrodes of supercapacitors. By adding a mixture of detergent and water, the droplets of the liquid salt were reduced to nanoscale sizes.
This salt acts as an electrolyte (which is required for storage of electrical charge), as well as preventing the atom-thick graphene sheets sticking together, hugely increasing their exposed surface area and optimising energy storage capacity.
“We’re showing record numbers for the energy-storage capacity of supercapacitors,” said Professor Michael Pope, a chemical engineer at the University of Waterloo. “And the more energy-dense we can make them, the more batteries we can start displacing.”
According to Professor Pope, supercapacitors could be a green replacement for lead-acid batteries in vehicles, capturing the energy otherwise wasted by buses and high-speed trains during braking. In the longer term, they could be used to power mobile phones and other consumer technology, as well as devices in remote locations, such as in orbit around Earth.
“If they are marketed in the correct ways for the right applications, we’ll start seeing more and more of them in our everyday lives,” said Professor Pope.