A team led by Hongmin Wang of the University of Washington set out to make a real electric brick. Specifically, they wanted to see if they could use a steam coating technique to turn ordinary red bricks into part of a supercapacitor. It is not actually enough strange as it sounds, considering that the red of a brick is an iron ore, and iron is a common component of some battery chemistries. Bricks are also often porous, which means that there is a lot of surface that a thin coating could interact with this iron.
The process (something they had developed before) involves heating the brick in an enclosure with hydrochloric acid and an organic compound that luckily shortens to “EDOT”. The two liquid substances evaporate and condense on the convoluted surface of the brick. The acid dissolves part of the iron ore, releasing iron atoms which help organic molecules bind together to form polymer chains (passing to “PEDOT”) that cover the surface. The polymer produces entangled microscopic fibers that form a continuous, electrically conductive layer on each face of the brick, which otherwise remains. (This, however, has the effect of making the brick black.)
The team tested performance in a few setups, including one with a robust gel electrolyte sandwiched between bricks like mortar. The epoxy coating of the whole thing makes it waterproof (as in, “runs underwater” waterproof) and also prevents the electrolyte from drying out. Many combinations of bricks connected in series and in parallel are obviously possible, although for testing they wired three units of tiny bricks the size of a sugar cube in series. After a full charge in 15 seconds, this setup powered an LED for about 11 minutes before the voltage dropped from the initial 2.7 volts to less than the 2.5 volts required by the LEDs.
Even with full-size bricks, the total energy storage is… less than huge. They estimate that a wall of these bricks could hold about 1.6 watt-hours per square meter of wall area. This means that a wall three by six meters (10 feet by 20 feet) could hold about 20 watt hours of electricity. As a result, the researchers’ argument for this idea is less dramatic than “turn your house into a battery!”
“Our supercapacitor technology adds value to a ‘cheap’ building material and demonstrates an evolutionary process allowing energy storage to power integrated microdevices in architectural applications using fired bricks,” they write. These powered walls are unlikely to be a challenge for Tesla’s Powerwall (13.5 weightwatt-hours in less than a square meter on the wall) anytime soon. But that’s a creative concept – one supercapacitor brick certainly wouldn’t be just another brick in the wall.
Nature Communications, 2020. DOI: 10.1038 / s41467-020-17708-1 (About DOIs).