A battery technology that could be far more powerful than lithium-ion is being developed by a team of researchers in Sweden and Slovenia.

Aluminium has been long been seen as a better potential base for batteries than lithium as it is able to exchange three electrons for every ion, compared to one for lithium, enabling up to three times more energy density. State-of-the-art aluminium-based batteries are being designed and tested in various laboratories around the world.

But researchers from Chalmers University of Technology in Gothenburg, Sweden, and the National Institute of Chemistry in Ljubljana, Slovenia, believe they have come up with a technology that will double the energy density of other aluminium-based batteries, and could lead to reduced production costs and less environmental impact.

“The material costs and environmental impacts that we envisage from our new concept are much lower than what we see today, making them feasible for large-scale usage, such as solar cell parks, or storage of wind energy, for example,” says Chalmers physics professor Patrik Johansson.

The team says that previous designs for aluminium batteries have used graphite as the cathode (the positive electrode), which has “too low an energy content to create battery cells with enough performance to be useful”.

The new concept uses an organic, nanostructured cathode made from the carbon-based organic molecule anthraquinone ( C14H8O2 ), developed by Jan Bitenc at the Slovenian facility.

“The advantage of this organic molecule in the cathode material is that it enables storage of positive charge-carriers from the electrolyte, the solution in which ions move between the electrodes, which make possible higher energy density in the battery,” the researchers say.

Chalmers researcher Niklas Lindahl adds: “Because the new cathode material makes it possible to use a more appropriate charge-carrier, the batteries can make better usage of aluminium’s potential. Now, we are continuing the work by looking for an even better electrolyte. The current version contains chlorine – we want to get rid of that.”

The aluminium batteries developed so far are only half as energy dense as lithium-ion ones, explains Johansson. “But aluminium is in principle a significantly better charge carrier than lithium, since it is multivalent – which means every ion 'compensates' for several electrons. Furthermore, the batteries have the potential to be significantly less environmentally harmful.”

It will also be a lot easier to recycle aluminium batteries than lithium ones, as “there already exists an established industry for its manufacturing and recycling”.