MIT study uses cement to produce supercapacitor

A study by the Massachusetts Institute of Technology (MIT) has found that combining cement and carbon black, which resembles very fine charcoal, may form the basis for a novel, low-cost energy storage system. The technology could facilitate the use of renewable energy sources such as solar, wind and tidal power by allowing energy networks to remain stable despite fluctuations in renewable energy supply.

According to the study, cement and carbon black can be combined with water to make a supercapacitor — an alternative to batteries — that could provide storage of electrical energy. The key to the new supercapacitors developed by this team comes from a method of producing a cement-based material with an extremely high internal surface area due to a dense, interconnected network of conductive material within its bulk volume. The researchers achieved this by introducing carbon black, which is highly conductive, into a concrete mixture along with cement powder and water, and letting it cure. The water naturally forms a branching network of openings within the structure as it reacts with cement, and the carbon migrates into these spaces to make wire-like structures within the hardened cement. 

These structures have a fractal-like structure, with larger branches sprouting smaller branches, and those sprouting even smaller branchlets, and so on, ending up with an extremely large surface area within the confines of a relatively small volume. The material is then soaked in a standard electrolyte material, such as potassium chloride, a kind of salt, which provides the charged particles that accumulate on the carbon structures. Two electrodes made of this material, separated by a thin space or an insulating layer, form a very powerful supercapacitor, the researchers found.

The MIT researchers who developed the system say that their supercapacitor could eventually be incorporated into the concrete foundation of a house, where it could store a full day’s worth of energy while adding little (or no) to the cost of the foundation and still providing the needed structural strength. The researchers also envision a concrete roadway that could provide contactless recharging for electric cars as they travel over that road using the same kind of technology used for wirelessly rechargeable phones. Initial uses of the technology might be for isolated homes or buildings or shelters far from grid power, which could be powered by solar panels attached to the cement supercapacitors, the researchers say.