Introducing the oxygen-ion battery

Lithium-ion batteries are ubiquitous, from electric cars to smartphones. However, they are not always the best solution for all areas of application. TU Wein has developed an oxygen-ion battery that has some advantages; although it does not allow for quite as high energy densities as the lithium-ion battery, its storage capacity does not decrease irrevocably over time. It can be regenerated and thus may enable a long service life. Oxygen-ion batteries can also be reproduced without rare elements and are made of incombustible materials. A patent application for the new battery idea has already been filed together with cooperation partners from Spain. The oxygen-ion battery could provide a solution for large energy storage systems, for example to store electrical energy from renewable resources.

“We have had a lot of experience with ceramic materials that can be used for fuel cells for quite some time. That gave us the idea of investigating whether such materials might also be suitable for making a battery,” said Alexander Schmid from the Institute for Chemical Technologies and Analytics at TU Wein.

The ceramic materials that the TU Wein team studied can absorb and release doubly negatively charged oxygen ions. When an electric voltage is applied, the oxygen ions migrate from one ceramic material to another, after which they can be made to migrate back again, thus generating electric current. Professor Jürgen Fleig said the basic principle is very similar to the lithium-ion battery, but the oxygen-ion battery’s materials have some advantages.

Ceramics are not flammable — so fire accidents, which can occur with lithium-ion batteries, are practically ruled out. In addition, there is no need for rare elements, which are expensive or can only be extracted in an environmentally harmful way. Tobias Huber said that the use of ceramic materials is also advantageous because they can be adapted very well; certain elements that are difficult to obtain can also be replaced with others relatively easily. The prototype of the battery still uses lanthanum — an element that is not exactly rare but not completely common either. However, lanthanum can be replaced by something cheaper, and research into this is already underway. Cobalt or nickel, which are used in many batteries, are not used at all.

Perhaps the most important advantage of the new battery technology is its potential longevity. “In many batteries, you have the problem that at some point the charge carriers can no longer move. Then they can no longer be used to generate electricity, the capacity of the battery decreases. After many charging cycles, that can become a serious problem,” Schmid said.

The oxygen-ion battery, however, can be regenerated without any problems: if oxygen is lost due to side reactions, then the loss can simply be compensated for by oxygen from the ambient air. The new battery concept is not intended for smartphones or electric cars, because the oxygen-ion battery only achieves about a third of the energy density that one is used to from lithium-ion batteries and runs at temperatures between 200–400°C. The technology is, however, interesting for storing energy.

“If you need a large energy storage unit to temporarily store solar or wind energy, for example, the oxygen-ion battery could be an excellent solution. If you construct an entire building full of energy storage modules, the lower energy density and increased operating temperature do not play a decisive role. But the strengths of our battery would be particularly important there: the long service life, the possibility of producing large quantities of these materials without rare elements, and the fact that there is no fire hazard with these batteries,” Schmid said.

Image caption: A prototype of the battery at TU Wien. Image credit: TU Wien