MIT team uses cement and carbon black to create battery alternative

1 Aug 2023

Image: MIT

A mixture of cement, carbon black and water can help create a device that can be the future of batteries and help keep grids stable.

Scientists in the US have created a new device that can store large amounts of renewable energy in a cheap and scalable way.

Made of abundantly available materials such as cement, water and carbon black (a material similar to charcoal powder), the so-called supercapacitor device is an alternative to batteries that could store large amounts of electricity for a variety of applications.

This includes incorporating the device into the concrete foundation of a house where it could store a full day’s worth of energy without any additional cost to the foundation or weakness to the house’s structural integrity.

Researchers based at the Massachusetts Institute of Technology (MIT), who developed the device, also said the supercapacitor could be used in the form of a concrete road that may someday be able to provide contactless recharging for electric cars as they travel over it.

Cement, carbon black and water are some of the most ubiquitous materials in our world today. Key to the supercapacitors developed by this team is a method of producing a cement-based material with an extremely high internal surface area that makes conductivity conducive.

This material – cement mixed with the highly conductive carbon black – is mixed with water and allowed to cure. Scientists said 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.

This allows for fractal-like structures with branches sprouting out to allow for an extremely large surface area within the confines of a relatively small volume. The material is then soaked in an electrolyte material, such as potassium chloride which provides the charged particles.

“The material is fascinating because you have the most-used manmade material in the world, cement, that is combined with carbon black, that is a well-known historical material — the Dead Sea Scrolls were written with it,” said MIT professor Admir Masic, who co-wrote the paper.

“You have these at least two-millennia-old materials that when you combine them in a specific manner you come up with a conductive nanocomposite, and that’s when things get really interesting.”

However, there is a trade-off between the material’s storage capacity and its structural strength. While adding more carbon black increases the capacity of the supercapacitor, it also reduces the strength of the concrete. The team found a “sweet spot” at around 10pc of carbon black.

The study was published in the PNAS journal yesterday (31 July). Other than Masic, the paper was co-written by MIT professors Franz-Josef Ulm and Yang Shao-Horn, as well as four others at MIT and at the Wyss Institute for Biologically Inspired Engineering.

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Vish Gain is a journalist with Silicon Republic