The formula: cement, water, and carbon black

In a study published July 31, 2023, in the Proceedings of the National Academy of Sciences (PNAS), an MIT team led by professors Franz-Josef Ulm, Admir Masic, and Yang-Shao Horn, along with co-author Nicolas Chanut, detailed how to transform concrete into an energy storage system.

The process relies on three basic materials: water, cement, and carbon black, which is a highly conductive, fine carbon powder resembling pure soot.

When mixed together, water naturally forms a branching network of microscopic channels within the curing cement. The carbon black particles migrate into these open spaces, self-assembling into a continuous, interconnected wire-like structure throughout the concrete.

To turn this material into a functioning supercapacitor, the cured concrete is soaked in a standard electrolyte, such as potassium chloride salt. This salt provides the charged particles that accumulate on the internal carbon framework.

Unlike standard lithium-ion batteries, which store energy through slow chemical reactions that degrade over time, a supercapacitor stores energy physically. When an electric current is applied, the salt ions migrate to opposite sides of the carbon network, creating a strong electric field. This allows the material to charge and discharge rapidly across thousands of cycles without losing performance.

Scaling the numbers: from leds to households

The initial laboratory demonstration proved the concept on a small scale. The researchers wired three small, coin-sized concrete units in series, charged them using a solar panel, and successfully powered a single LED bulb.

While small blocks only power basic electronics, the real value of the technology lies in its volume. Because concrete forms the structural foundation of modern cities, the available mass is immense.

The critical metric established by the MIT team highlights this potential:

• 45 cubic meters of carbon-black-doped concrete can store approximately 10 kilowatt hours (kWh) of energy.
• This capacity equals roughly the entire daily electricity consumption of an average household.

A standard residential home built with a foundation of this material could theoretically store a full day’s worth of power generated by rooftop solar panels.

Challenges and development tracking

The primary motivation behind this research is addressing the environmental impact of building construction. Concrete production accounts for roughly 8% of global carbon dioxide emissions. Finding a way to make this passive, carbon intensive material actively store clean energy could offset some of its environmental cost.

However, moving this technology from a laboratory environment to commercial construction sites requires solving major engineering hurdles. The development timeline shows the progression of this effort:

Future infrastructure: roads that charge EVs

If researchers can successfully scale the material while maintaining its structural strength, the applications extend well beyond home foundations.

The MIT team envisions creating public roadways built directly from this energy-storing concrete. These roads could be paired with solar fields to capture energy during the day and then use built-in inductive charging technology to wirelessly recharge electric vehicles as they drive over the pavement.

While the material holds less energy per cubic meter than a standard lithium-ion battery, its strength lies in its scale. Concrete forms the framework of roads, bridges, and buildings worldwide. Converting even a small fraction of that global mass into a durable, fast-charging storage network could provide the exact type of large-scale backup grid needed to balance renewable energy.