It’s often said that supercapacitors are the future of energy storage, but for that statement to become reality, supercapacitor performance needs to increase greatly, and that is just what researchers at MIT have been working on. In a newly released study, researchers from MIT and a few other institutions have developed a novel class of liquids that could revolutionize how supercapacitors perform by increasing capacity by four or five times, improve reliability, and could reduce the risk of fire in the event of a catastrophic failure.
(Image Credit: Image: Xianwen Mao, MIT)
The new electrolyte is based on a class of materials known as ionic liquids, which are a type of liquid salts. Ionic liquids have been studied for a few decades now, but it's only recently that researchers have begun mixing them with surfactant-like compounds. The addition of these compounds causes the ionic liquids to become highly viscous. When used inside of a supercapacitor, this new viscous fluid is able to store more energy as its temperature increases.
This is similar to how other ionic liquid-based electrolytes behave, but in the case of this new formulation, the viscosity stays much higher than other electrolytes at high temperatures and has the ability to quickly increase energy storage capacity as the temperature rises. This is because the molecules in the new liquid automatically align with each other in layers on the electrode’s surface. These aligned layers prevent a phenomenon called “overscreening” where the first layer of ions that attach to the surface of the electrode contains more ions than there are corresponding charges on the surface which results in a diminished capacity.
"The reason why it’s behaving so differently from conventional electrolytes is because of the way the molecules intrinsically assemble themselves into an ordered, layered structure where they come in contact with another material, such as the electrode inside a supercapacitor," says T. Alan Hatton, a professor of chemical engineering at MIT and the paper’s senior author. “It forms a very interesting, sandwich-like, double-layer structure.”
“The material could help to improve the performance of supercapacitors. Such devices can be used to store electrical charge and are sometimes used to supplement battery systems in electric vehicles to provide an extra boost of power. Using the new material instead of a conventional electrolyte in a supercapacitor could increase its energy density by a factor of four or five.” MIT postdoc Xianwen Mao says. “Using the new electrolyte, future supercapacitors may even be able to store more energy than batteries, he says, potentially even replacing batteries in applications such as electric vehicles, personal electronics, or grid-level energy storage facilities.”
MIT researchers are calling this new class of materials Surface_Active Ionic Liquids or SAILs for short, and that supercapacitors made using SAILs could be highly effective in high-temperature environments such as oil drilling rigs, chemical plants, electrical production facilities, and even aerospace.
“The material could also be useful for a variety of emerging separation processes," Mao says. “A lot of newly developed separation processes require electrical control,” in various chemical processing and refining applications and in carbon dioxide capture, for example, as well as resource recovery from waste streams. These ionic liquids, being highly conductive, could be well-suited to many such applications."
If you would like to learn more about these new SAILs, or the team's research, please visit this link.
Source: MIT News