Collection of batteries

Aluminium battery potential boosted by new materials

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A collaboration of Swiss materials scientists has identified two materials which could render aluminium batteries far more usable and adaptable.

Researchers are constantly on the search for materials and techniques to improve battery technology, particularly as high-capacity batteries are increasingly required to store electricity generated by solar and wind power.

One field of battery technology generating interest concerns aluminium batteries, which produce electricity as aluminium reacts with oxygen in the air. Aluminium batteries are mostly made from cheap and naturally abundant materials. They have extremely high energy density, although have so far failed to reach mass market appeal, in part due to corrosion of the battery components in the highly aggressive electrolyte fluid.

Solving this problem could set aluminium batteries on the road to widespread usage and to compete with lithium batteries. Despite considerable interest surrounding lithium battery technology, this type of battery contains costly, toxic and rare materials.

Materials scientists based at ETH Zurich and the Swiss Federal Laboratories for Materials Science and Technology (Empa), who have been long involved with aluminium battery research, have identified new materials which could help advance aluminium battery technology. One of the materials – a corrosion-resistant material – could be used in the conductive parts of the battery, while the other could be used as an adaptive material for the battery’s anode.

Titanium nitride – which is a conductive ceramic – is easy to manufacture and is resistant to corrosion by electrolyte fluid. The researchers tried using this material in the form of thin films to create aluminium batteries; they believe that it could also be possible to use thin films of titanium nitride to coat existing conductors. This could even be printed onto plastic in tracks.

“The potential applications of titanium nitride are not limited to aluminium batteries. The material could also be used in other types of batteries; for example, in those based on magnesium or sodium, or in high-voltage lithium-ion batteries,” said Professor Maksym Kovalenko, an ETH Zurich materials scientist.

The second material, the hydrocarbon polypyrene, could be used for the anode - the positive pole - of aluminium batteries. At present, aluminium batteries tend to have aluminium cathodes (negative poles) and graphite anodes. Experimentation with polypyrene demonstrated that it allowed an aluminium battery to store a similar amount of energy as a graphite anode, but had the advantage high of adaptability. Polypyrene electrodes could be adjusted by scientists such that their properties, such as porosity, are changed to best suit the application.

“In contrast, the graphite used at present is a mineral,” said Kovalenko. “From a chemical engineering perspective, it cannot be modified.”

As both the ceramic and hydrocarbon share the property of flexibility, the researchers suggest that they could be suitable for use in soft batteries designs, such as in ‘pouch cells’.

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