Concrete Mix Forms Self

Researchers at MIT have discovered that by mixing cement and carbon black with water, the resulting concrete can self-assemble into an energy-storing supercapacitor. This supercapacitor has the ability to power a home or fast-charge electric cars. This development takes energy storage using concrete to the next level, as it eliminates the need for mesh electrodes in the concrete. Instead, the carbon black forms its own connected electrode structures during the curing process.

Water and cement react together in a way that creates a network of branching channels in the concrete as it hardens. The carbon black naturally migrates into these channels, forming carbon electrodes with a large surface area throughout the concrete. Once the concrete is bathed in a standard electrolyte, such as potassium chloride, these channels act as the plates of a supercapacitor. Supercapacitors are able to charge and discharge almost instantly, resulting in higher power density and output compared to standard lithium batteries. However, the tradeoff is that energy density is lower and adding more carbon black weakens the concrete.

This concrete energy storage device is advantageous because it does not need to be small. Concrete is typically used in bulk quantities for construction purposes. In fact, an average American home of about 2,000 square feet uses approximately 31 cubic yards of concrete. The MIT team estimates that a 1,589-cubic-foot block of nanocarbon black-doped concrete can store around 10 kWh of electricity, which is enough to cover a third of the power consumption for an average American home.

The MIT team has tested these concrete supercapacitors on a small scale, lighting up a 3-volt LED by using pairs of electrode discs cut from the concrete. They are now working on larger-scale demonstrations, aiming for a 1,589-cubic-foot, 10-kWh version. This technology has significant potential for various applications, including pairing the concrete supercapacitors with roadside solar panels and inductive charging coils for wireless EV charging roads. Additionally, it could potentially be used in large grid-based energy storage facilities. However, it is unclear whether this concrete would be suitable for outdoor use or if it can be poured on-site to self-assemble. The research is open-access and published in the journal PNAS.