Building materials are getting closer to doubling as batteries

Concrete already builds our world, and an MIT-invented variant known as electron-­conducting carbon concrete (ec³, pronounced “e c cubed”) holds out the possibility of helping power it, too. Now that vision is one step closer. 

Made by combining cement, water, ultra-fine carbon black, and electrolytes, ec³ creates a conductive “nanonetwork” that could enable walls, sidewalks, and bridges to store and release electrical energy like giant batteries. To date, the technology has been limited by low voltage and scalability challenges. But the latest work by the MIT team that invented ec³ has increased the energy storage capacity by an order of magnitude. With the improved technology, about five cubic meters of concrete—the volume of a typical basement wall—could store enough energy to meet the daily needs of the average home.

MIT EC³ HUB

The researchers achieved this progress by using high-resolution 3D imaging to learn more about how the conductive carbon network—essentially, the electrode—functions and interacts with electrolytes. Equipped with their new understanding, the team experimented with different electrolytes and their concentrations. “We found that there is a wide range of electrolytes that could be viable candidates for ec³,” says Damian Stefaniuk, a research scientist at the MIT Electron-Conducting Carbon-Cement-Based Materials Hub, led by associate professor Admir Masic. “This even includes seawater, which could make this a good material for use in coastal and marine applications, perhaps as support structures for offshore wind farms.”

At the same time, the team streamlined the way electrolytes were added to the mix, making it possible to cast thicker electrodes that stored more energy.

While ec³ doesn’t rival conventional batteries in energy density, itcan in principle be incorporated directly into architectural elements and last as long as the structure itself. To show how structural form and energy storage can work together, the team built a miniature arch that supported its own weight and an additional load while powering an LED light.