Tokyo team develops cobalt-free batteries

With the ongoing difficulties in sourcing ethical, clean materials for electric vehicles and battery storage, researchers from the University of Tokyo have presented a viable alternative to the most controversial element used in lithium-ion batteries – cobalt.

High-capacity and reliable rechargeable batteries are increasingly becoming a critical piece of most devices and even modes of transportation. As the need for lithium-ion batteries rises, so too does the demand for cobalt, a metal tied to many environmental, economic, and even social issues.

While many research teams around the world have been attempting to create batteries without such a strong dependence on cobalt, a team at Tokyo University has presented a viable alternative, which they say, in some ways, can outperform state-of-the-art battery chemistries and survive a large number of recharge cycles.

In addition, the underlying theory for their breakthrough can also be applied to other problems.

For decades, lithium-ion batteries have been the standard way of powering portable or mobile electronic devices and machines. Chances are, you are reading this on a laptop or smartphone, and if not, you probably own at least something that requires batteries.

As the world transitions from fossil fuels, batteries are being increasingly seen as a critical part for use in electric vehicles and other clean energy technologies, especially if one needs to store excess energy during low production times like solar and wind.

But just as batteries hold a positive and negative end, lithium-ion batteries hold negative points that set against their positive ones.

The downside of lithium-ion

One of the negatives is that although lithium-ion batteries are some of the most power-dense portable power sources available, many people wish they could hold even more energy to make them either last longer or power even more demanding machines.

Also, they degrade with time and recharge cycles. We have all experienced this with smartphone batteries that used to last all day but now need to be plugged in to get through the evening. Ultimately, the ideal battery would be one that can survive more recharge cycles, maintains its capacity for longer, and does not negate the benefit a battery brings in its very production.

While clever chemistries and workarounds can slowly develop the first two points, perhaps the most alarming problem with current lithium-ion batteries lies in one of the elements used in their manufacture.

Cobalt is widely used in one of the essential parts of lithium-ion batteries, their electrodes.

All batteries work in a similar way: two electrodes, one positive and one negative, promote a flow of ions (lithium) between them in what is called the electrolyte when connected to an external circuit.

Cobalt, however, is a relatively rare ingredient. So rare, in fact, that most of the world's supply comes from a series of mines located in the Democratic Republic of Congo.

Many issues have been reported there over the years about the environmental consequences of these mines, but more importantly, the labor conditions, which include the use of child labor to dig up this material. From a supply perspective, the source of cobalt is an issue due to the ongoing political and economic instability in the region.

"There are many reasons we want to transition away from using cobalt in order to improve lithium-ion batteries," said Professor Atsuo Yamada from the Department of Chemical System Engineering at Tokyo University. "For us the challenge is a technical one, but its impact could be environmental, economic, social and technological. We are pleased to report a new alternative to cobalt by using a novel combination of elements in the electrodes, including lithium, nickel, manganese, silicon and oxygen – all far more common and less problematic elements to produce and work with."

Cobalt replacement

The new electrodes and electrolyte Yamada and his team created are not only devoid of cobalt, but they actually improve upon some current battery chemistries.

Their new lithium-ion batteries' energy density is reportedly 60% higher, which equates to a longer use-life and can deliver up to 4.4 volts, as opposed to the conventional 3.2 to 3.7 volts. However, one of the most surprising technological achievements was improving recharging capabilities.

Through various lab tests with the new chemistry, the team was able to fully charge and discharge over 1,000 cycles – which simulated roughly three years of full use and charging – resulting in losing about 20% of its storage capacity.

"We are delighted with the results so far, but getting here was not without its challenges. It was a struggle trying to suppress various undesirable reactions that were taking place in early versions of our new battery chemistries which could have drastically reduced the longevity of the batteries," said Yamada. "And we still have some way to go, as there are lingering minor reactions to mitigate in order to improve the safety and longevity even further. At present, we are confident that this research will lead to improved batteries for many applications, but some, where extreme durability and lifespan are required, might not be satisfied just yet."

According to their research paper published in "Nature Sustainability," the team removed cobalt and instead changed the carbon anode material from graphite to silicon, resulting in a lower cost, higher sustainability, and higher theoretical energy density battery.

In their paper, complex chemistry details are laid out, but ultimately, the team was able to improve upon decades of research to stably create a cobalt-free silicon anode battery – SiOx|LiNi0.5Mn1.5O4.

Although Yamada and his team were exploring applications in lithium-ion batteries, the concepts that underlie their recent development can be applied to other electrochemical processes and devices, including other kinds of batteries, water splitting (to produce hydrogen and oxygen), ore smelting, electro-coating, and more.

With this new breakthrough, a different approach to clean energy technologies may result in batteries that do not rely on the questionable cobalt from DRC and many other interesting and, hopefully, greener technologies begin to surface.