A team led by researchers at Pacific Northwest National Laboratory (PNNL) has shown that vapor from lithium oxide (Li2_O) sublimation accelerates a chemical reaction that forms single crystals when mixed with nickel-rich precursors. The sublimation happens at just one atmosphere of pressure. Single-crystal battery materials are thought to help batteries last longer.

An open-access paper on their work is published in Nature Energy.

The discovery offers a potentially faster, more efficient, and cheaper way to scale up the manufacturing of nickel-rich lithium-ion batteries.

—Jie Xiao, corresponding author

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. Nickel can store more energy than cobalt, so increasing the amount of nickel in a lithium-ion battery makes the materials more cost-effective. Nickel may also help reduce the cost of scaling up cathode manufacturing.

However, working with nickel still presents a challenge, Xiao said. Nickel-rich lithium cathode material tends to form as agglomerations known as “polycrystals”. Boundaries between the crystals become weaker as the battery discharges and charges. Over time, these weaknesses lead to cracking, which degrades the battery and shortens its lifetime.

Single-crystal cathodes don’t have the vulnerabilities that arise from polycrystal structures. So, we hope single crystals will mitigate and eventually eliminate all the big challenges in nickel-rich cathode materials.

—Jie Xiao

Over the last few years, Xiao’s team has been exploring different lithium salts supplied by industry partner Albemarle Corporation. Mixing these salt ingredients, or precursors, 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 Li_{2O at temperatures around 900 degrees Celsius, single-crystal cathode material readily formed.}

Xiao and her colleagues turned to their industry partner Thermo Fisher Scientific, which studied the reaction under an instrument called a MicroReactor. With those observations and a newly designed experiment, the team was able to successfully reveal the sublimation phenomenon. The new research confirms the mechanism is driven by Li₂O sublimation.

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

—Jie Xiao

The team further applied the Li₂O sublimation phenomenon to convert spent polycrystals directly into single crystals simply through a mixing-and-heating process. The successful formation of new single crystals shows that Li₂O salt considerably simplifies the recycling process of spent or waste polycrystals. Especially for those scraps from the production line, they can be quickly “remade” into high-performance single crystals by this salt ingredient, Xiao said.

New single crystals, either from fresh precursors or from spent polycrystals, withstood 1,000 charge/discharge cycles.

The team has more work to do before any batteries can be produced, Xiao said. Because Li₂O is not broadly used for materials synthesis, the cost to use it commercially is currently too high. However, Xiao noted that Li₂O is easily produced by processing other lithium salts, such as LiOH.

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.

Resources

• Wu, B., Yi, R., Xu, Y. et al. Unusual Li₂O sublimation promotes single-crystal growth and sintering. Nat Energy (2025). doi: 10.1038/s41560-025-01738-4