Researchers at the Massachusetts Institute of Technology (MIT) are exclaiming excitement over a new non-carbon semiconductor material that stands to open up new possibilities for energy storage, and more.
Until now, semiconductors utilizing conductive carbon had come close to being fully researched, with few new avenues to explore, but after years of tinkering with a class of materials called metal-organic frameworks, or MOFs, things are looking promising.
This, says researchers, could pay dividends in future electric vehicles, as capacitors have high discharge rates, and storage capacity may in time come close to that of batteries. Researchers also say grid storage that could help match usage times with generation times is possible, along with a host of possibilities.
The MOFs, are extremely porous, sponge-like structures with an extraordinarily large surface area for their size – much greater than seen in carbon materials.
“We’ve found an entirely new class of materials for supercapacitors,” said award-winning Mircea Dincă, an MIT associate professor of chemistry, who co-authored a paper being reported in the journal Nature Materials. “All double-layer supercapacitors today are made from carbon. They use carbon nanotubes, graphene, activated carbon, all shapes and forms, but nothing else besides carbon. So this is the first noncarbon, electrical double-layer supercapacitor.”
In short, the research could mean a superior and all-new type of supercap, but a bump in the research road is MOFs are not very electrically conductive – which they need to be.
“One of our long-term goals was to make these materials electrically conductive,” Dincă said, even though doing so “was thought to be extremely difficult, if not impossible.” But the material did exhibit another needed characteristic for such electrodes, which is that it conducts ions (atoms or molecules that carry a net electric charge) very well.
A major advantage of the new material is it can be made in much less harsh conditions than carbon-based materials which require temperatures over 800 deg C (1,472 deg F), and strong reagent chemicals for pretreatment.
What’s more, new devices the MIT team have produced already match or exceed key performance parameters of existing carbon-based versions, such as ability to withstand large numbers of charge/discharge cycles.
Tests showed they lost less than 10 percent of their performance after 10,000 cycles, which is comparable to existing commercial supercapacitors.
Further, the MOFs that Dincă et, al, are working with hold promises beyond energy storage.
“Our lab’s discovery of highly electrically conductive MOFs opened up a whole new category of applications,” Dincă says.
For example, the conductive MOFs could be used to make electrochromic windows, which can be darkened with the flip of a switch, and chemoresistive sensors, which could be useful for detecting trace amounts of chemicals for medical or security applications.
The cost of the material, while not as “dirt cheap” as carbon, is also not prohibitive meaning researchers are rubbing their hands together with the prospect of finding much more potential for the MOFs.
This view was verified by an independent third party peer reviewing the work done to date.
According to Alexandru Vlad, a professor of chemistry at the Catholic University of Louvain in Belgium, who was not involved in this research, a key advantage is that “this work shows only the tip of the iceberg.
“With carbons we know pretty much everything, and the developments over the past years were modest and slow,” Vlad continued. “But the MOF used by Dincă is one of the lowest-surface-area MOFs known, and some of these materials can reach up to three-times more [surface area] than carbons. The capacity would then be astonishingly high, probably close to that of batteries, but with the power performance [the ability to deliver high power output] of supercapacitors.”
Does it Matter?
To date, little has been done with super capacitors in cars we can drive, excluding Mazda’s i-ELOOP (pictured top).
A few years ago, big talk which has since hushed down was made of potentialities, including from startup companies that hyped carbon-based supercaps’ extraordinary potential – which never came through.
As the auto industry looks to more types of vehicles, and more use cases, the energy storage capability of a supercapacitor that exceeded previous examples could benefit cars of the future.
According to the researchers at MIT, and elsewhere who are at work on the technology, they may not have even scratched the surface. So, time will tell.