Reliable, high-capacity, rechargeable batteries are a critical component of many devices and vehicles. But the production of batteries for electric cars, for example, requires the use of a wide variety of elements, many of which are scarce, expensive and have a notable impact on the environment, among which lithium currently stands out (batteries lithium ion, LIB).
Another problematic component is cobalt, which is integrated into the electrodes of this type of battery and whose extraction has important environmental repercussions.
An international team including researchers from the University of Tokyo (Japan) has this week presented a viable alternative to cobalt that, in some aspects, can surpass state-of-the-art battery chemistry. Tests with the new design of LIB batteries show that they work very efficiently in a large number of recharge cycles and partially solve some environmental problems of this type of equipment.
Cobalt is widely used for a key part of LIBs, the electrodes. All batteries work in a similar way: two electrodes, one positive and one negative, promote the flow of lithium ions between them in what is called electrolyte when connected to an external circuit.
Cobalt, however, is a rare (scarce) element in nature. In fact, there is currently only one main source of supply: the mines located in the Democratic Republic of the Congo.
Many issues have been reported over the years about the environmental consequences of these mines, as well as the working conditions at these mines, including the use of child labor. Also from a supply perspective, the source of cobalt is an issue due to political and economic instability in the region.
"There are many reasons why we want to stop using cobalt to improve lithium-ion batteries," said Professor Atsuo Yamada of the Department of Chemical Systems Engineering at the University of Tokyo. “For us the challenge is technical, but its impact could be environmental, economic, social and technological. "We are pleased to report on a new alternative to cobalt by using a novel combination of elements in the electrodes, including lithium, nickel, manganese, silicon and oxygen, all of which are much more common and less problematic elements to produce and work with," says this researcher in a note released by his university.
The results of this research have been published (October 19, 2023) in the journal Nature Sustainability.
The new electrodes and electrolytes that Yamada and his team created not only lack cobalt, but in some ways improve current battery chemistry. The power density of the new LIBs is about 60% higher, which could equate to a longer lifespan, and they can deliver 4.4 volts, as opposed to about 3.2-3.7 volts for typical LIBs. . But one of the most surprising technological achievements was the improvement of charging features. Test batteries with the new chemistry were able to fully charge and discharge in more than 1,000 cycles (simulating three years of full use and charging), while only losing about 20% of their storage capacity.
“We are delighted with the results so far, but getting here was not without challenges. “It was a struggle trying to suppress several undesirable reactions that were taking place in early versions of our new battery chemistries that could have dramatically reduced the longevity of the batteries,” Yamada said. “And we still have a long way to go, as there are still minor reactions to mitigate to further improve safety and longevity. “We are currently confident that this research will lead to improved batteries for many applications, but some, where extreme durability and lifespan are required, may not be satisfied yet.”
Although Yamada and his team were exploring applications at LIB, the concepts underlying their recent development can be applied to other electrochemical processes and devices, including other types of batteries, water splitting (to produce hydrogen and oxygen), mineral smelting, electrocoating, among other possible applications.
Reference article: Seongjae Ko, Xiao Han, Tatau Shimada, Norio Takenaka, Yuki Yamada and Atsuo Yamada, “Electrolyte design for lithium-ion batteries with cobalt-free cathode and silicon oxide anode”, Nature Sustainability, https: //doi.org /10.1038/s41893-023-01237-y
