To increase storage capacity in future batteries, GM and Argonne (working separately) are modifying the nickel-manganese-cobalt material in a couple of ways, says Jeff Chamberlain, manager of Argonne’s battery program.
First, they are changing the relative proportions of the three metals, to create a material able to store more lithium ions. Second, they are “activating” some of the inactive components, by freeing lithium from the inactive material so that it can move between the cathode and the anode. Once the lithium ions are free, they move only in and out of the active material, and the inactive material continues to play its stabilizing role.
Much work remains before these materials can be used in cars. “It’s one thing to make powder in a reaction vessel here at Argonne; it’s a very different thing to make a battery pack,” Chamberlain says. “There is a lot of innovation on the engineering side in terms of turning these materials into batteries.”
Doubling the energy density of the cathode does not double the amount of energy the battery pack as a whole can store. The storage capacity of the anodes has to keep pace, and the electrolytes have to be modified to work at higher voltages. Also, all three of these main components of the battery have to be engineered to work well together—for example, in order to limit unwanted chemical reactions. Once engineers have successfully incorporated the electrodes and electrolytes into working battery cells, more engineering is needed to incorporate the cells into battery packs.
The stability of the new materials suggests a way to increase energy density at the pack level, Chamberlain says. The current Volt battery pack is designed with extra energy-storage capacity to ensure that the car’s performance doesn’t suffer much as the battery ages. He says if future batteries lasted without needing the extra capacity, this would decrease the cost of the pack.
“This is probably the most capable cathode material that we have seen out there, and that’s the reason that we think it’s really critical that we get started working on this material now, so that we can get it on the road,” Lauckner says. “It’s going to take some years to further develop it and validate it. The idea is we want to get this on the road for the next generation of battery packs that come out.”
Several other companies are working with Argonne’s technology, including one, Envia, that is working with Argonne to combine advanced nickel-manganese-cobalt electrode materials with advanced silicon anode materials. This project, which is being funded by the Department of Energy’s Advanced Research Projects Agency for Energy, aims to produce batteries that store three times as much energy as today’s lithium-ion car batteries.