Researchers from the Department of Architecture and Civil Engineering at Sweden’s Chalmers University of Technology have released outline details of a new concept for rechargeable batteries made of cement. The concept could allow buildings to become giant renewable energy storage units.

The idea involves a cement-based mixture with small amounts of short carbon fibres added to increase the conductivity, sandwiched between a metal-coated carbon fibre mesh with iron for the anode, and nickel for the cathode.

“Results from previous studies into concrete battery technology showed very low performance, so we realised we had to think out of the box, to come up with another way to produce the electrode,” says lead researcher Dr Emma Zhang. “This particular idea – which is also rechargeable – has never been explored before. Now we have proof of concept at lab scale,” she says.   

Working with Professor Luping Tang, the pair produced a rechargeable cement-based battery with an average energy density of 7 Watthours per square metre. A modest estimate is that the performance of the new Chalmers battery could be more than ten times that of earlier attempts at concrete batteries. The energy density is still low in comparison to commercial batteries, but this limitation could be overcome because of the huge volume at which the battery could be constructed when used in buildings.    

According to Dr Zhang, the fact that the battery is rechargeable is its most important quality. “The possibilities for utilisation if the concept is further developed and commercialised are huge,” she says. Energy storage in building is an obvious possibility. The researchers see applications that could range from powering LEDs, providing 4G connections in remote areas, or cathodic protection against corrosion in concrete infrastructure.

It could also be coupled with solar cell panels, for example, to become the energy source for monitoring systems in highways or bridges, where sensors operated by a concrete battery could detect cracking or corrosion,” suggests Dr Zhang.

The concept of using structures and buildings in this way could be revolutionary, because it would offer a large volume of energy storage. Concrete is the world’s most commonly used building material, says Zhang, but from a sustainability perspective, it is far from ideal. The potential to add functionality to it could offer a new dimension.

“We have a vision that in the future this technology could allow for whole sections of multi-storey buildings made of functional concrete. Considering that any concrete surface could have a layer of this electrode embedded, we are talking about enormous volumes of functional concrete,” she says.