MIT researchers have improved a new type of “concrete battery” by a factor of 10, paving the way for applications that could turn buildings, bridges, and sidewalks into giant energy stores capable of powering entire cities.
The material is called electronically conductive carbon concrete (or ec3) and is made from a combination of cement, water, a common liquid electrolyte, and a very fine carbon powder called nanoscale carbon black.
When the ingredients are mixed, they form a dense conductive network that can carry charge. Once solidified into concrete, the material and everything made from it (buildings, bridges, pavements, etc.) can store and release energy as needed.
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It’s a concept known as supercapacitive energy storage, and researchers hope it can provide a viable solution to one of renewable energy’s biggest challenges: how to store power locally when the sun isn’t shining or the wind isn’t blowing.
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In a new study published September 29 in the journal Proceedings of the National Academy of Sciences (PNAS), researchers say they have achieved a 10-fold increase in ec3’s energy storage capacity starting in 2023. Currently, 5 cubic meters (176.5 cubic feet) of the material can store more than 10 kilowatt-hours of electricity, almost enough to power a typical home for a day.
Just two years ago, this level of storage would have required nine times more capacity, the team says.
“With these higher energy densities and their demonstrated value in a broader range of applications, we now have a powerful and flexible tool that can help address a wide range of persistent energy challenges,” MIT researcher Damian Stefaniuk, lead author of the study, said in a statement.
“One of our biggest motivations was to support the transition to renewable energy. For example, solar power has made great strides in terms of efficiency. But it can only generate electricity if there is enough sunlight. The question then becomes: how do you meet your energy needs at night or on cloudy days?”
build a battery
Although ec3 can’t match the energy density of traditional battery technologies like lithium-ion (which packs hundreds of times more energy into the same weight or volume), the fact that it can be injected directly into building components without relying on rare or toxic materials and has the potential to last as long as the structure itself is particularly attractive to scientists.
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The new performance improvements came from a better understanding of the interaction between the carbon network and the electrolyte inside the concrete, as well as changes in how the material is manufactured.
Rather than immersing slabs of material in the electrolyte after curing, the researchers added the electrolyte directly to the water used for initial mixing. This made it possible to produce thicker, more energy-dense slabs without compromising conductivity.
The team also tested different types of electrolytes, including seawater, and found several viable options. The best results were obtained from a mixture of quaternary ammonium salts used in household disinfectants and acetonitrile, a conductive solvent common in industrial processes.
Power the block
Most exciting for scientists was the realization that ec³ could be produced by making small changes to the way concrete is made. This could present a huge opportunity for sustainable construction, with the material potentially being used to develop what researchers call “multifunctional concrete” that can store energy, absorb carbon dioxide from the atmosphere, and even repair itself.
The material has already been tested in Japan to warm sidewalks in snowy conditions, and could serve as an alternative to road salt. The team is currently working towards real-world applications, from homes operating off-grid to parking spaces and roads that could one day charge electric cars.
“What we’re most excited about is showing that you can do something completely new with a material as old as concrete,” study co-author James Weaver, an associate professor of materials science and engineering at Cornell University, said in a statement.
“Combining modern nanoscience with the building blocks of ancient civilizations opens the door to infrastructure that not only supports our lives, but also powers people.”
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