MIT researchers reported in the October 2025 issue of the Proceedings of the National Academy of Sciences that optimizing electrolytes and manufacturing processes have increased the energy storage capacity of the latest electron-conducting carbon concrete (ec³) supercapacitors by an “order of magnitude.” This finding resulted in 5 cubic meters of concrete (about the volume of a typical basement wall) with the improved electrolyte capable of storing enough energy to meet the daily needs of the average home.

Combining cement, water, ultra-fine carbon black (with nanoscale particles) and electrolytes, ec³ creates a conductive “nanonetwork” inside concrete that allows structures to store and release electrical energy—in effect, to serve as batteries.

“A key to the sustainability of concrete is the development of ‘multifunctional concrete,’ which integrates functionalities like this energy storage, self-healing and carbon sequestration.” says Admir Masic, lead author of the study, co-director of MIT’s Electron-Conducting Carbon-Cement-Based Materials Hub (EC³ Hub) and associate professor of civil and environmental engineering at MIT.

The team reconstructed the conductive nanonetwork at the highest resolution by using focused ion beams for the sequential removal of thin layers of the ec³ material, followed by high-resolution imaging of each slice with a scanning electron microscope. Doing so revealed that the network is essentially a fractal-like “web” that surrounds ec³ pores, which is what allows the electrolyte to infiltrate and current to flow through the system. 

They then experimented with different electrolytes at various concentrations to learn how that affected energy storage density. They discovered a wide range of electrolytes that could be viable candidates for ec³, including seawater, making the material a good candidate for marine applications.

Adding electrolytes to the mix instead of curing ec³ electrodes and then soaking them in electrolytes streamlined the process and enabled them to create thicker electrodes capable of storing more energy.

Switching to organic electrolytes, especially those that combine quaternary ammonium salts with acetonitrile (a clear, conductive liquid) produced the best performance and most storage.

Researchers believe ec³ can be incorporated directly into architectural elements such as slabs, walls, domes and vaults, and that they will last as long as the structures they’re part of. In the spirit of Roman architecture, the team built a miniature ec³ arch. It supported its own weight and additional load while powering a 9V LED light, but when the load increased, the light flickered, probably due to the way stress affects electrical contacts or the distribution of charges.

“There may be a kind of self-monitoring capacity here,” Masic said. “We may be able to use this as a signal of when and to what extent a structure is stressed, or monitor its overall health in real time.”

The team believes that ec³ will enable buildings and infrastructure to meet energy storage needs and is working on applications like parking spaces and roads that could charge electric vehicles, as well as homes that can operate fully off the grid. This material is currently used to heat sidewalks in Sapporo, Japan, due to its thermally conductive properties.