Mercedes-Benz, a subsidiary of Daimler, is researching ways to design cobalt and other “critical” materials like lithium out of lithium-ion batteries.
The German vehicle OEM is looking at a variety of post-lithium-ion batteries— mainly based on manganese— that use less critical resources as it investigates ways of increasing the energy density of its technology.
As well as performance and environmental concerns, the benefit of reducing the use of critical materials is cost. The biggest financial factor in the composition of the cathode is the use of nickel, manganese and cobalt. The anode is made from graphite powder, lithium, electrolytes and a separator.
Manganese is being researched because it is easier to mine and benefits from established recycling facilities from its use in alkali batteries. Daimler is exploring magnesium-sulfur batteries, which eliminates lithium use, but its research is only at the laboratory stage.
Other alternatives being explored include: replacing graphite powder with silicon to increase energy density by up to 25%; and a lithium-sulfur battery, although this could be many years from being used in passenger car applications.
Andreas Hintennach, senior manager of battery research at Mercedes-Benz, said: “With the current generation of battery cells, we have already been able to reduce the proportion of cobalt in the active material (nickel, manganese, cobalt, lithium) from around a third to less than 20%.
“In the laboratory we are currently working with less than 10% and the share is set to fall even more in the future. From a chemical perspective there are a lot of arguments for abstaining cobalt entirely. The more the mixture of materials is reduced, the easier and more efficient it is to recycle. The energy required for chemical production is also reduced because the mixture is easier to produce.”
He add: “There are even technologies that are superior to the lithium-ion battery. These include the solid-state battery. The technology has a very long life cycle, and also does not include any cobalt, nickel or manganese. However, its energy density is lower, which makes it relatively large and slow to charge. That is why it is good for commercial vehicles but not for passenger cars.”
Daimler will be using solid-state technology in its Mercedes-Benz eCitaro urban bus within the second half of the 2020s, said Hintennach.