It sounds like science fiction; a battery that charges in minutes holds an immense amount of power is lightweight and foldable. However, scientists at the University College London (UCL) have developed a new prototype supercapacitor that has the potential to replace batteries. Capacitors have been around for a long time and they are found in all electronic circuits. Ordinary capacitors simply store and release small amounts of electrical energy. Supercapacitors store and release more energy than regular capacitors, but not as much as batteries, until now.
What makes a supercapacitor super?
One of the main limitations of a battery is how long it takes to charge it. Even Tesla’s fast-charging battery takes an hour to charge from 40% to 80%, and another two hours to go from 80% to 100%. In contrast, a supercapacitor can go from a 0% charge to a 100% charge in about 10 minutes.
Another problem for today’s lithium-ion batteries is the rare earth elements needed to make them. The rarity of elements like lithium is the main reason batteries are so expensive. UCL’s experimental supercapacitor is made of graphene, which is made from carbon, an element that is cheap and readily available.
Lastly, batteries are heavy and they add significantly to the weight of EVs. In contrast, graphene is incredibly light. A sheet of graphene is composed of a single layer of carbon atoms. A sheet of graphene, if you held it edge-wise, is too thin to be visible to the naked eye!
All of those advantages make supercapacitors far superior to lithium-ion batteries. The only thing holding supercapacitors back is that they haven’t been able to hold as much charge as a lithium-ion battery can in a similar amount of space.
Why this breakthrough makes supercapacitor energy storage possible
According to the lead researcher in the study that developed the new supercapacitor, Dr. Zhuangnan Li (UCL Chemistry):
“We designed materials which would give our supercapacitor a high power density – that is how fast it can charge or discharge – and a high energy density – which will determine how long it can run for. Normally, you can only have one of these characteristics but our supercapacitor provides both, which is a critical breakthrough”
Dr. Zhuangnan Li and his team achieved that breakthrough by fine-tuning the pore size of the graphene sheet used. Those pores are spaces between the carbon atoms that make up the graphene used in the supercapacitor”.
How the supercapacitor compares to battery charge and power density
The new supercapacitor has an energy density of 88.1 Watt-hours per liter. That is a fraction of what lithium-ion batteries have, which is an energy density of over 200 Watt-hours per liter. Since energy density is a measure of how long the supercapacitor can provide power for, that means that a hypothetical EV equipped with supercapacitors may only have a fraction of the range of an EV equipped with lithium-ion batteries. However, the supercapacitor’s power density is over 10,000 Watt-hours per liter. In contrast, a lithium-ion battery has a power density of only 200 Watts per liter. Thanks to that, a supercapacitor can charge much faster than a lithium-ion battery.
How soon will these supercapacitors be available?
The new supercapacitor is at the proof-of-concept stage. This means that a small example device has been created to demonstrate that the idea works. The next step is to attempt to create a prototype, which would be an example of a supercapacitor that would be sold on the market. However, it can take years to go from proof-of-concept to working prototype.
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