New Prismatic Line Unlocks Powerful Possibilities for U.S. Battery Research

RICHLAND, Wash.—A major step in energy storage development hummed to life this month as researchers flipped on a new battery production line at the Department of Energy’s Pacific Northwest National Laboratory.

The production line, made up of 16 pieces of equipment that fill an entire 1400-square-foot laboratory space, will create a cutting-edge type of battery cell called a prismatic cell. A first for the national laboratories, the prismatic cell line will allow researchers to test emerging energy storage technology that may become vital to supporting grid operations.

And because even the tiniest amount of water can damage battery materials, the prismatic line is housed in a dry lab where the humidity is lower than the driest places on Earth. 

“With the new prismatic line, we can create, test and demonstrate real-world prismatic cells at an industrially relevant scale. This helps our researchers bridge the gap between science and industry,” said Adam Jivelekas, operations manager of DOE’s Grid Storage Launchpad, which is operated by PNNL on its campus in Richland and funded by DOE’s Office of Electricity. “We can help external researchers or industry partners test and validate their prismatic cell designs.”

A new look for batteries

Batteries come in many different shapes and sizes. Coin cells are small and can be found in things like wristwatches. Pouch cells, meanwhile, are bigger and might fit into a power tool like an electric drill. Then there are standard cylindrical batteries like double- and triple-As, or larger cylindrical batteries that fit in electric vehicles.

While these other battery formats continue to have applications, prismatic cells are gaining popularity for grid-scale applications. They’re rectangular, shaped more like a classic 9-volt battery, but larger. They’re also built with a heavier metal casing that makes them less prone to overheating. Metal conducts heat better than other materials, meaning heat can escape the battery more easily, said Mark Weller, a materials scientist at PNNL who is principal investigator on the project.

The prismatic cell shape allows them to be stacked efficiently, fitting more cells into a smaller space compared to other cell types like cylindrical cells. At the pack level, efficient packing confers better energy density (more energy available in a smaller package) and makes prismatic cells attractive for grid applications.

“If you have better heat transport, if the cells are more mechanically uniform, if they’re packed more efficiently, all those things can translate to not just higher safety, but lower cost,” Weller continued. 

First steps for the prismatic line

The prismatic line completed testing in February, and the researchers are currently finalizing operating procedures before putting it to work with a major project intended to validate its efficacy.

“It’s one thing to have this capability, it’s another to show our partners that we can use it to consistently make high-quality prismatic cells for different applications,” Weller said. “Making a coin cell takes a few milligrams of material; making a prismatic cell takes at least a kilogram. When you scale up like that, you can’t assume that a chemistry that worked well in a coin cell will work just as well in a prismatic cell.”

To prove that point, PNNL researchers picked two different battery chemistries to use in prismatic cells: sodium-ion and lithium-iron-phosphate. Sodium is seen as a potential replacement for lithium in energy storage systems for the grid because it’s much more abundant on Earth than lithium. Lithium-iron-phosphate also relies on more abundant materials (e.g., iron, whereas traditional battery materials nickel and cobalt are both rare) and tends to be safer.

The team will produce those two prismatic cell types and then submit them to a number of tests to validate the performance and safety of the cell under varying conditions, said Weller.

“These tests will establish a baseline that we can take to potential collaborators and say ‘Here are our results for these chemistries, here’s our process and here’s what we can do for your chemistry,’” Weller continued. “Because of the benefits of the prismatic cell design and the categorically larger scale of cell fabrication and testing, we see PNNL’s prismatic line as a unique way to bridge the gap between new battery concepts and prospective industry partners. With this capability, we can do the research and development and pilot-scale testing that is difficult for companies to justify and help facilitate a smoother handoff to get advanced battery concepts to market.”

Now that the prismatic line is up and running, the team at the Grid Storage Launchpad hopes to start working with private battery companies who want to test their own chemistries in a prismatic cell format.