New Battery Could be Grid Storage Solution

New Battery Could be Grid Storage Solution

May 14, 2023

Lithium-ion batteries are ubiquitous today – from electric cars to smartphones. But that does not mean that they are the best solution for all areas of application. TU Wien has now succeeded in developing an oxygen-ion battery that has some important 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 an extremely long service life.
In addition, oxygen-ion batteries can be produced 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 be an excellent solution for large energy storage systems, for example to store electrical energy from renewable sources. 
“We have had a lot of experience with ceramic materials that can be used for fuel cells for quite some time,” says Alexander Schmid from the 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 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.
“The basic principle is actually very similar to the lithium-ion battery,” says Prof. Jürgen Fleig. “But our materials have some important advantages.” Ceramics are not flammable – so fire accidents, which occur time and again 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.
“In this respect, the use of ceramic materials is a great advantage because they can be adapted very well,” says Tobias Huber. “You can replace certain elements that are difficult to obtain with others relatively easily.” The prototype of the battery still uses lanthanum – an element that is not exactly rare but not completely common either. But even lanthanum is to 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.

But 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,” says Alexander 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, 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 and 400 °C. The technology is, however, extremely 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,” says Alexander Schmid. “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.”

Lithium-ion batteries can be problematic for grid storage given their high cost and reliance on materials with limited geographical reserves, such as cobalt and lithium—as well as their potential to catch fire. Flow batteries, which store energy in large tanks of low-cost chemicals, show promise for grid storage, but the materials used in them, such as vanadium, are expensive. Meanwhile, other battery technologies such as sodium sulfur and molten salt, just like lithium-ion batteries, use volatile liquid electrolytes that can pose a safety risk in case the device fails.
–

Tests done on full cells of the oxygen-ion batteries showed volumetric energy densities of up to 140 milliwatt-hours per cubic centimeter, which corresponds to about 30 percent of the volumetric energy density of today’s lithium-ion batteries.
Reliance on oxygen ions to store energy gives the new chemistry a unique advantage over lithium, though. “Oxygen is abundant in the atmosphere,” says Schmid. “Lithium-ion batteries often lose capacity because ions are lost due to side reactions and parasitic current. This can also happen in oxygen-ion battery but we can regenerate any lost oxygen simply from the atmosphere.”
This gives the batteries a much longer lifetime than lithium ion. The team has tested their prototype for about 1,000 charge cycles, but they expect the device to last for over hundreds of thousands of charge cycles by regenerating any lost oxygen.
The electrodes are made mostly from abundant elements such as iron, calcium, titanium, chromium, and manganese. And while the team hasn’t calculated what the cost would be, the use of plentiful materials should tip the scale in their favor, Schmid says. There is also an advantage in terms of production of these ceramic materials, he adds, because “there already exists some infrastructure to make such materials from the solid-oxide fuel-cell community. This group of materials is well understood”