Researchers at the University of Waterloo have used nanotechnology to significantly improve the energy-storage devices known as supercapacitors. This is one step closer to charging cellphones in seconds.
This new design doubles the amount of electrical energy the rapid-charging devices can hold, helping pave the way for eventual use in everything from smartphones and laptops to electric vehicles and high powered lasers.
"We're showing record numbers for the energy-storage capacity of supercapacitors," said Michael Pope, a professor of chemical engineering who led the Waterloo research. "And the more energy-dense we can make them, the more batteries we can start displacing."
Supercapacitors are a green alternative to traditional batteries. Their benefits include improved safety and reliability along with the faster charging. But applications have been limited because of their relatively low storage capacity.
Existing commercial supercapacitors can only store enough energy to power cell phones and laptops for about 10 percent as long as rechargeable batteries.
In order to boost that capacity, Pope and his collaborators developed a method that coats atomically thin layers of a graphene with an oily liquid salt in supercapacitor electrodes.
The liquid salt acts as a spacer to separate the thin graphene sheets, preventing them from stacking like pieces of paper. This dramatically increases their exposed surface area, which is a key to maximizing energy-storage capacity.
At the same time, the liquid salt does double duty as the electrolyte needed to actually store electrical charge, which minimizes the size and weight of the supercapacitor.
"That is the really cool part of this," Pope said. "It's a clever, elegant design."
The innovation uses a detergent to reduce the size of the droplets of oily salt to just a few billionths of a meter, which improved their coating action. The detergent also functions like a chemical Velcro to make droplets stick to graphene.
Increasing the storage capacity of supercapacitors means they can be made small and light enough to replace batteries for more applications.
In the short term, Pope said better supercapacitors could displace lead-acid batteries in traditional vehicles, and be used to capture energy that would be otherwise lost by buses and high-speed trains when they brake.
Although they are unlikely to attain full storage capacity of batteries, supercapacitors have the potential to conveniently and reliably power consumer electronics devices, electrical vehicles and systems in remote locations like space.
"If they're marketed in the correct ways for the right applications, we'll start seeing more and more of them in our everyday lives," Pope said.
A paper on this research was published recently in ACS Nano.