One of the problems with li-ion batteries (lithium-iron) is the cobalt used in the cathode. About 60% of the world’s supply comes from the Democratic Republic of Congo (DRC), where the mining of the metal has been linked to human rights abuses, corruption, environmental destruction and child labour.
Many companies would like to reduce or eliminate cobalt in lithium batteries, but it is difficult to match its efficiency, and Tesla is one of the few that has been successful in replacing some of it with other chemicals.
Now a research team from McGill University in Montreal, Canada, has come up with a coating that might make it possible for iron and silicon – two of the world’s most abundant elements – to step in for cobalt.
Li-ion batteries with iron and silicon cathode
The McGill team’s work centred around a cathode made of lithium iron silicate. Theoretically it has a high capacity to hold energy over several charge-discharge cycles, but in practice, this hasn’t been achieved.
What the group did is experiment with the carbon coating that is applied to cathodes to improve capacity. This is a science unto itself. Cobalt is mixed with manganese, nickel or aluminum in the cathode, and some companies coat the crystals of the whole alloys.
Nano One, who we wrote about in April improve performance by coating the nanocrystals of the individual elements.
There are also different elements used as the coating of the crystal, carbon being one of the most common. But for the lithium iron silicate alloy the McGill group has been working on, they tried an electronically conductive polymer called PEDOT.
PEDOT (poly-ethylenedioxythiophene-polystyrene-sulfonate, if you’re really interested) was invented in the 1980s and first used as an anti-static for photographic film. Figuring out a way to apply it to the surface of the nanocrystals took almost two years, but the leader of the team, Majid Rasool, said “We were not expecting that big of a jump in performance over carbon coating.”
To validate the work, the cathodes were sent halfway across Canada to Canadian Light Source in Saskatchewan, where they were tested using the organization’s Soft X-ray Spectromicroscopy and Macromolecular Crystallography Facility.
Coating process opens new production strategies
“The testing information let us dig deeper and begin to explain why the PEDOT coating treatment and the sub-surface iron-rich layer improved performance so much.” Said Rasool. “There’s still work to be done to understand why and build on this, but this coating process opens up new engineering strategies for batteries.”
We’ll put in our usual disclaimer about battery research. It is a long way from laboratory results to you hooking the battery up to your electric boat motor. Rasool and his cohorts seem to have some advantages, though.
They are working with the huge utility, Hydro-Quebec, that is also working with Johnathan Goodenough on a new glass battery. Goodenough is one of the three men who received the Nobel Prize for inventing the lithium-ion battery.
Could drive down the cost of li-ion batteries
Aside from the ethical issues of cobalt, being able to use iron and silicon in the cathode could radically reduce the price of li-ion batteries. Some estimate that the cost of the cathode can make up 40% of a battery cell’s price.
So who knows? If the PEDOT coating (or something else that comes out of this research) is technically and commercially practical, you may be able to look forward to a boat battery made of iron and sand (silica) and start approaching the idea of being ‘dirt cheap’.