New UChicago Research Redefines Battery Failure In EV Cathodes

New research from Argonne National Laboratory and the UChicago Pritzker School of Molecular Engineering has identified previously misunderstood degradation mechanisms in lithium-ion battery cathodes—findings that could enable longer-lasting and safer batteries for electric vehicles and other technologies.

Published in Nature Nanotechnology, the study examines why single-crystal nickel-rich cathode materials, which were expected to outperform conventional polycrystalline designs, have not consistently delivered improved durability or performance in real-world battery systems.

“Electrification of society needs everyone’s contribution,” said Khalil Amine, Argonne Distinguished Fellow and joint professor at UChicago. “If people don’t trust batteries to be safe and long-lasting, they won’t choose to use them.”

The research was conducted by first author Jing Wang during her PhD work at the UChicago Pritzker School of Molecular Engineering through the Grid Storage Launchpad Research Consortium (GRC) program. The work was jointly supervised by Shirley Meng’s Laboratory for Energy Storage and Conversion and Amine’s Advanced Battery Technology team at Argonne National Laboratory. Through the GRC program and UChicago’s Energy Transition Network, Wang worked closely with scientists at national laboratories and industry partners as part of a collaborative research effort.

“When people try to transition to single-crystal cathodes, they have been following similar design principles as the polycrystal ones,” said Wang, now a postdoctoral researcher working with UChicago and Argonne. “Our work identifies that the major degradation mechanism of the single-crystal particles is different from the polycrystal ones, which leads to the different composition requirements.”

In conventional polycrystalline cathodes, degradation arises from the repeated expansion and contraction of primary particles during charging and discharging. Over time, this motion widens grain boundaries between crystals, allowing electrolyte intrusion that can trigger unwanted side reactions and oxygen release, raising safety concerns such as thermal runaway. More commonly, the result is gradual capacity degradation as batteries lose their ability to deliver the same charge over time.

“Typically, it will suffer about five to 10% volume expansion or shrinkages,” Wang said. “Once an expansion or shrinkage exceeds the elastic limits, it will lead to the particle cracking.”

Single-crystal cathodes eliminate grain boundaries altogether, yet degradation continued to occur. The study showed that switching to single-crystal materials is not a simple substitution, as degradation in these cathodes is driven by a distinct mechanical failure mode.

“We demonstrate that degradation in single-crystal NMC cathodes is predominantly governed by a distinct mechanical failure mode,” said Tongchao Liu, a chemist at Argonne and a corresponding author on the paper. “By identifying this previously underappreciated mechanism, this work establishes a direct link between material composition and degradation pathways, providing deeper insight into the origins of performance decay in these materials.”

Using multi-scale synchrotron X-ray techniques and high-resolution transmission electron microscopy, the researchers observed that cracking in single-crystal cathodes is primarily driven by reaction heterogeneity. Different regions within a single particle react at varying rates, generating internal strain rather than strain between crystals, as seen in polycrystalline materials.

The findings also challenge long-standing assumptions about the roles of cobalt and manganese in cathode design. Polycrystalline cathodes typically balance nickel, manganese, and cobalt contents, with cobalt historically used to mitigate lithium–nickel disorder despite its contribution to cracking.

By constructing and testing nickel–cobalt cathodes without manganese and nickel–manganese cathodes without cobalt, the team found that the opposite behavior applies to single-crystal materials. In these systems, manganese was more detrimental to mechanical properties, whereas cobalt improved durability.

“Not only are new design strategies needed, but different materials will also be required to help single-crystal cathode batteries reach their full potential,” said Meng, who is also director of the Energy Storage Research Alliance based at Argonne. “By better understanding how different types of cathode materials degrade, we can help design a suite of high-functioning cathode materials for the world’s energy needs.”

Cobalt’s cost remains a challenge, and Wang noted that the next step toward real-world application will be identifying lower-cost materials that replicate cobalt’s stabilizing effects.

“Advances come in cycles,” Amine said. “You solve a problem, then move on to the next. The insights outlined in this collaborative paper will help future researchers at Argonne, UChicago PME, and elsewhere create safer, longer-lasting materials for tomorrow’s batteries.”

(Citation: “Nanoscale Strain Evolution in Single Crystal Battery Positive Electrodes,” Wang et al., Nature Nanotechnology, December 16, 2025. DOI: 10.1038/s41565-025-02079-9)

Source: UChicago Pritzker School of Molecular Engineering

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