Long-Life Oxygen-Ion Battery Shows Promise as an Environmentally-Friendly Lithium-Ion Alternative

A research team from TU Wien in Vienna has built a fully-functional oxygen-ion battery — which, they claim, can serve as a safer, longer-lasting, and more environmentally-friendly alternative to the ubiquitous lithium-ion battery, at least for certain applications.

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

The ceramic material developed by the team forms the basis of the battery's electrodes, thanks to its ability to absorb and release doubly-negatively charged oxygen ions. Apply a voltage, and the ions migrate from one electrode to the other; draw a current and they'll migrate back again, releasing the stored energy in the process.

"The basic principle is actually very similar to the lithium-ion battery," says Jürgen Fleig, TU Wein professor and co-author on the paper. "But our materials have some important advantages." Perhaps the biggest of these is safety: lithium-ion batteries react explosively when punctured, bursting into flames which are difficult to extinguish. The oxygen-ion battery, by contrast, isn't flammable even if pierced or crushed.

Another advantage is that the oxygen-ion battery doesn't need lithium, cobalt, or other rare elements, making it theoretically cheaper to produce and more environmentally friendly. "In this respect, the use of ceramic materials is a great advantage because they can be adapted very well," says co-author Tobias Huber. "You can replace certain elements that are difficult to obtain with others relatively easily." The only catch: the prototype is built using relatively uncommon lanthanum, which the team is seeking to replace in the future.

"In many batteries, you have the problem that at some point the charge carriers can no longer move," adds Schmid of another problem with lithium-ion batteries. "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, though, could last for many more charging cycles — simply harvesting free oxygen from the surrounding air to replace any it has lost over time.

The only real catch, as there always must be, is that the prototype oxygen-ion battery can't match lithium-ion's impressive energy storage capacity — maxing out at around one-third the energy density. Another issue which may limit its use in smartphones and other portable devices is its high operating temperature of 200-400°C (392-752°F), considerably higher than you'd want to consider carrying around in your pocket.

"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," Schmid proposes of potential use-cases for the battery design. "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."

The team's work has been published under open-access terms in the journal Advanced Energy Materials.