Most Americans have supported the idea of using more renewable energy sources, less fossil fuels and being less wasteful for some time. But a big key to untethering ourselves from current consumption habits – like replacing our cell phones every few years, driving gas-guzzling vehicles and powering our homes with energy from fossil fuels – is developing better technology for storing energy. According to one Drexel researcher, that technology is already here and is ready to help us move past the energy storage limits of today’s batteries.
Yury Gogotsi, PhD, director of the A.J. Drexel Nanomaterials Institute in the College of Engineering, is one of the prominent researchers in the development of new materials and architectures for this technology. He has written extensively on how nanomaterials can be used to vault our energy management into the future. Gogotsi and his collaborator Patrice Simone, PhD, of Université Paul Sabatier, in France, recently published a perspective in the journal Nature Materials about how one particular type of energy storage device – the electrochemical capacitor, or “supercapacitor” – could play a pivotal role in our sustainable future.
Gogotsi took some time to explain his research in this area and the work that remains for this technology to realize its full potential. (Author’s note: In case you’re wondering, here’s a short primer on the difference between batteries and supercapacitors).
As you’ve looked at the progress in this field over the last decade you suggest that the development of batteries and electrochemical capacitors are converging around the goal of being able to quickly store and disburse more energy — which of the two devices do you think have greater strides to make in order to achieve this goal?
Batteries have been progressing faster and better than electrochemical capacitors — also called “supercapacitors” or “ultracapacitors” — largely due a hundred times larger investment into the field.
However, what is very important is that both technologies are moving toward the same goal of high-rate charging and long lifetime and they may end up meeting at the same point a few years down the road.
Currently, they often complement each other. For example, about five years ago SEPTA installed a battery/supercapacitor hybrid system than can recover 1.5-2 megawatt-hours of electricity per day by collecting the energy of braking trains. The addition of the supercapacitors, which store charge electrostatically rather than chemically, and do it much faster than lithium-ion batteries, enables the trains to capture more energy during braking.
Supercapacitors are capable of storing or delivering more energy than batteries within just a short period of breaking — only a minute or less. Using supercapacitors for this also reduces the strain on the battery and extends its life. SEPTA is just one of many public transit systems using the technology this way and more systems will be using it in the future.
You mentioned a number of very important applications for electrochemical supercapacitors in everyday technology – from computer battery back-up, to recharging batteries in public transit and hybrid and electric cars during braking, to harvesting energy from renewable resources like wind and sun – ECs have been around just as long as batteries, why do you think they are still the lesser-known of these two devices among the general public?
In general, supercapacitors are still used less frequently than batteries because there is a smaller market for them. One thing they have going against them is actually their excellent durability compared to batteries. Conventional carbon-based electrical double-layer capacitors have the lifetime of more than a million of charge-discharge cycles. If your device is powered by a supercapacitor, it’s likely that you will never have to change it — unlike batteries.
People are more familiar with batteries because they see them more frequently when they have to replace them in remote controls, watches and other devices — or when they see their battery performance of their cell phones declining. But most people have never seen a supercapacitor because they are hidden inside our gadgets and never need to be replaced. This also means people aren’t buying a lot of supercapacitors in a lifetime, hence there is a smaller market for them.
Not surprisingly, a number of important contributions to the development of ECs have been made at Drexel. Which of those do you think researchers will view as the most significant contribution when someone writes a review article about ECs 20 years from now? Why?
Carbide-derived carbon, which we studied for more than decade, is now being used in the best European supercapacitors produced by Skeleton Technologies.
Our latest research has been focusing on MXenes, 2D carbides and nitrides that have a higher conductivity than porous carbon or graphene — which means a higher power for a supercapacitor — and also can store energy chemically, like a battery, which means more energy stored. We are confident that these new materials will have a major impact on the field of energy storage in general.
You noted that many new research tools and applications have been important in making the basic scientific discoveries that have enabled progress in EC development. What sort of tool is still needed to continue making strides in this area?
The performance of a supercapacitor or a battery is largely determined by the materials used in the electrodes, current collectors, separators, packaging, etc., as well as the electrolyte chemistry. As the action happens in the nanometer-thin layer at the interface between the electrode material and the electrolyte, we need to study the atomically and molecularly thin layer. Therefore, we need the best microscopes and spectrometers used for nanoscale research to see what is going on at the interfaces where charge is stored.
Which industry do you anticipate being the largest driver behind EC development in the next 20 years?
Internet of Things (IoT) and wearable internet, such as health monitors, smart smoke detectors, and other digital devices that gather and share data, will require energy storage devices that last for the lifetime of the gadget. Since batteries very quickly lose their efficiency per unit of volume when scaled down and have a limited lifetime, supercapacitors may offer a solution and become embedded into our future distributed electronic devices, thus powering the Internet of Things.
Which industry has already had the greatest impact on taking new EC discoveries from lab to consumer thus far?
Transportation, including energy recovery from trams, trains, hybrid buses, etc. We are also seeing them used widely for engine starting in cars, especially in the start-stop applications. Many European countries require manufacturers to design cars that turn engines off when stopping at traffic lights, so ECs are used to quickly start them again — their long cycle lifetime is very important in this application. They are also being used in industrial manufacturing machinery, such as robots, port gantry cranes, or uninterruptable power supplies.
Your group along with Drexel researchers at the Center for Functional Fabrics, has already made some very important progress toward the integration of ECs into wearable devices, what do you believe will be the first wearable tech breakthrough enabled by ECs?
This is going to be one of the fastest growing technology sectors, in general, in the coming years, so we are likely to see a number of important breakthroughs enabling this growth. According to a recent IDTechEx market report on wearable technology, this industry will see a three-fold growth in its market cap from over $24 billion today to over $70 billion in 2025. Also, the global market for electronic textiles is projected to reach nearly $5.55 billion in 2025 at a compound annual growth rate of 30.4% over the forecast period.
Textile-based energy storage devices will be required for various smart textile applications. Wearable augmented reality devices are among the promising markets and industries to explore. Especially, with more people likely to shift to work-from-home due to the coronavirus pandemic, there is a need for development of new augmented reality and virtual reality tools that can facilitate engagement of people without the need to be in the office or a plant.
Harvesting energy from movement, body temperature or even radio waves, and storing it, for powering sensors, antennas, RFID tags embedded in clothes will be a good job for supercapacitors.
Gogotsi is the Distinguished University and Bach professor in the Department of Materials Science and Engineering in Drexel’s College of Engineering. He has received numerous accolades for his research on two-dimensional materials and their application for energy storage. The American Chemical Society recently recognized Gogotsi as the recipient of its 2021 Award in the Chemistry of Materials. Gogotsi and Michel Barsoum, PhD, Distinguished professor in Drexel’s College of Engineering, recently organized the first international conference on MXene materials research held in the United States.
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