A new eco-friendly battery concept made from abundant materials has twice the energy density compared with previous versions.

To facilitate a booming renewable energy industry that moves away from the mining of rare-earth minerals for large-scale batteries, researchers are attempting to find ways to produce more eco-friendly ones.

Now, researchers from Chalmers University of Technology, Sweden, and the National Institute of Chemistry, Slovenia, have unveiled an aluminium battery concept with twice the energy density compared with previous attempts.

Writing in Energy Storage Materials, the researchers said aluminium batteries offer several advantages including high theoretical energy density and the fact that the metal is so ubiquitous and well-established in manufacturing and recycling.

These significantly lower production costs – when compared with lithium-ion batteries – and could be ideal for large infrastructure projects such as solar farms and the storage of wind energy.

Previous designs for this type of battery used the aluminium as the anode (negative electrode) and graphite as the cathode (positive electrode). However, graphite was found to produce too low an energy content to make useful battery cells with enough performance.

A complementary battery

To differentiate from this, the Swedish and Slovenian researchers replaced graphite with an organic, nanostructured cathode made of the carbon-based molecule anthraquinone.

What gives this molecule an advantage in aluminium batteries is that it enables storage of positive charge carriers from the electrolyte, giving it higher energy density.

“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,” said Chalmers researcher Niklas Lindahl.

“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.”

Speaking about whether aluminium batteries could ever be commercially produced to the same extent as lithium-ion batteries, researcher Patrik Johansson added: “Above all, they can be complementary, ensuring that lithium-ion batteries are only used where strictly necessary.

“There remains work to do with the electrolyte, and with developing better charging mechanisms, but aluminium is in principle a significantly better charge carrier than lithium, since it is multivalent – which means every ion ‘compensates’ for several electrons.”