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Discovery opens doors for cheaper and quicker battery manufacturing

The sublimination process is captured with the Thermo Scientific Helios 5 UX and the MicroReactor. Video courtesy of the PNNL/Sara Levine

A new study published in Nature Energy has revealed that a common lithium salt may serve as a critical ingredient to manufacture cheaper, longer-lasting battery materials. The discovery centers on sublimation, the process whereby a solid turns directly into a vapor.

 

Scientists at the U.S. Department of Energy’s Pacific Northwest National Laboratory (PNNL), in collaboration with Thermo Fisher Scientific, have showed that vapor from lithium oxide (Li2O) sublimation accelerates a chemical reaction that forms single crystals when mixed with nickel-rich precursors.

 

Single-crystal battery materials are thought to help batteries last longer. What’s more, the sublimation happens at just one atmosphere of pressure, the everyday pressure felt at sea level.

 

“The discovery offers a potentially faster, more efficient, and cheaper way to scale up the manufacturing of nickel-rich lithium-ion batteries,” said Jie Xiao, co-author on the paper and a Battelle Fellow who holds a joint appointment with PNNL and the University of Washington. “The research shows us how materials science can be applied to simplify the manufacturing process.”

 

The promise of nickel

Creating materials for batteries is a little like baking: combine the right ingredients, apply heat, and produce something new. For batteries, researchers hunt for materials to make positive and negative electrodes of a battery (sometimes referred to as cathodes and anodes, respectively). Positive electrodes work by accepting ions and electrons, which creates the flow of electricity that powers devices like flashlights, laptops, cell phones, or even cars and data centers.

As demand for devices with rechargeable batteries grows, scientists are constantly looking for materials that can store more energy and last longer.

Conventional lithium-ion batteries are limited by cost and how much energy they can hold, Xiao said. To reduce the cost, cheaper nickel and manganese are often mixed with cobalt into the battery material.

But despite its benefits, working with nickel still presents a challenge. Nickel-rich lithium cathode material tends to form as agglomerations known as “polycrystals,” like a cookie packed with chocolate chips.

Libor Novák, Ph.D., R&D manager at Thermo Fisher, is pictured holding the MicroReactor next to a scanning electron microscope. Libor Novák, Ph.D., R&D manager at Thermo Fisher, is pictured holding the MicroReactor next to a scanning electron microscope.

Boundaries between the crystals—like the boundary between the cookie and the chocolate chips—become weaker as the battery discharges and charges. Over time, these weaknesses lead to cracking, which degrades the battery and shortens its lifetime. In the past five years, Xiao and her colleagues have been searching for materials that form single-crystal structures, like a plain chocolate cookie. The chocolate is still there, but it’s evenly distributed through the cookie rather than packed in clumps.

The mystery of sublimation

Xiao’s team has been exploring different lithium salts. Mixing these salt ingredients with nickel-rich precursors produces cathode material. One of the most common production methods is to melt the lithium salt, which then reacts with the nickel-rich precursor. For this process, researchers have preferred lithium hydroxide (LiOH) because it has a low melting point.

In contrast, Li2O has a high melting point at 1,438 degrees Celsius, so it’s rarely used for cathode material synthesis.

But when experimenting with Li2O in Xiao’s materials synthesis lab at PNNL, something surprising happened: when combining the nickel-rich precursor with Li2O at temperatures around 900 degrees Celsius, single-crystal cathode material readily formed.

To study – and confirm – this reaction at microscopic levels, the team turned to Thermo Fisher Scientific, which supported the work using the Thermo Scientific Helios 5 UX, an instrument with the most advanced electron and ion optics capabilities, and an add-on component called the MicroReactor.

The experiment involved heating the sample on the instrument and adding clean gas (oxygen) to simulate the high-temperature environment in which battery material is commercially made. The experiment enabled the team of scientists to successfully observe the Li2O sublimination reaction for the first time.

Jie Xiao, co-author of the study published in Nature Energy. Jie Xiao, co-author of the study published in Nature Energy.

“It was a very exciting moment during the experiment when we were able to not only record the reaction in real time, but to also confirm that the process may serve as a new approach to development more efficient and cost-effective batteries that are in very high demand globally,” said Libor Novák, Ph.D., research and development manager for the analytical instruments business at Thermo Fisher and inventor of the MicroReactor.

 

The new research confirms the mechanism is driven by Li2O sublimation. In the baking scenario, it would be like combining the cookie dough with vaporized chocolate. The cookie has no chunks of chocolate, just a chocolate cookie with no distinct boundaries.

 

“The vapor can penetrate everywhere, right into the other precursors’ pores or surface and immediately react,” Xiao said. “Single crystals form much faster in the presence of those vapors.”

Potential boon to manufacturing

The discovery may provide a new way to manufacture single crystals, but the team has more work to do to make the process more cost effective. With industry partners, Xiao and her team are now working to scale up the process with lower manufacturing costs.

 

The team hopes to provide single crystals to their strategic partners in 2026.

 

This work was funded by the Advanced Materials and Manufacturing Technologies Office and the Vehicle Technologies Office within the Department of Energy’s Energy Efficiency and Renewable Energy Office.

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