Air to power future long storage batteries

While lithium-ion batteries have become omnipresent for nearly all portable energy needs, we have quickly found that they are ultimately limited in what they are capable of. Enter Vienna University of Technology, where German scientists have found a way to harness the most abundant element on earth to breathe new life into the future of energy storage.

Exploring new battery chemistries for the green energy transition, researchers at Vienna University of Technology, or TU Wien, have succeeded in developing an oxygen-ion battery.

Though this technology does not allow for quite as high energy densities as its lithium-ion predecessor, oxygen-ion batteries have some important advantages that may provide a solution to the elemental demands of its dominant cousin.

One, its storage capacity apparently does not decrease irrevocably over time; two, it can be regenerated and thus has the possibility of enabling extremely long service life; three, it is made of noncombustible materials; and four; and the most important aspect, oxygen-ion batteries can be made without rare elements.

With all these factors, oxygen-ion batteries could be an excellent solution for large, stationary energy storage systems that are needed to store energy from renewable sources.

Secret was in the ceramic

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

The ceramic materials that the TU Wien team studied can absorb and release double negatively charged oxygen ions. This means that when an electric voltage is applied, the oxygen ions will migrate from one ceramic material to another, after which they can be made to migrate back again, thus generating an electric current.

"The basic principle is actually very similar to the lithium-ion battery," said Professor Jürgen Fleig, Head of Institute for Chemical Technologies and Analytics. "But our materials have some important advantages."

As is widely known, ceramics are not flammable – so fire hazards, which occur time and again with lithium-ion batteries, are ruled out.

However, its most significant benefit is it won't need those materials that are limiting the widespread adoption of low-carbon technologies like nickel and cobalt.

"In this respect, the use of ceramic materials is a great advantage because they can be adapted very well," said TU Wien Institute of Structural Engineering co-author Tobias Huber. "You can replace certain elements that are difficult to obtain with others relatively easily."

The prototype battery still does require a specific material – alas, it's not magical electrified pottery – it needs lanthanum.

While lanthanum is a rare earth element, it is more abundant than its lanthanide counterparts and is being produced in excess alongside the magnet rare earths needed for electric vehicle motors, wind turbines, and an array of other commercial products.

Despite this, the researchers already have a goal to replace the lanthanum with something cheaper.

Oxygen is key to a long life

Although another potential battery that won't need the critical materials used in lithium-ion is significant, the TU Wien team press that its most important advantage is its potential longevity.

"In many batteries, you have the problem that at some point the charge carriers can no longer move," said Schmid. "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."

The oxygen-ion battery can be regenerated without any problems as any oxygen lost due to side reactions can simply be recouped from the ambient air.

Nevertheless, the new battery concept is not intended for smartphones or electric cars – because the oxygen-ion battery can only achieve about a third of the energy density of a typical lithium-ion battery as well as running between 200 to 400 degrees Celsius (392 to 752 degrees Fahrenheit) – the technology is primed for storing energy.

"If you need large energy storage unit to temporarily store solar or wind energy, for example, the oxygen-ion battery could be an excellent solution," the first author said. "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."

A patent application for this new battery idea has already been filed. The team's work has also been published under open-access terms in the journal "Advanced Energy Materials."