Researchers at Argonne National Laboratory and the UChicago Pritzker School of Molecular Engineering (UChicago PME) have identified the source of a long-standing battery problem linked to fading capacity, shorter lifespans, and in some cases fires. The findings clarify why certain advanced lithium ion batteries break down faster than expected and how those failures might be reduced.

The work, published in Nature Nanotechnology, explains how extremely small internal stresses can build up inside battery materials and trigger cracking. These effects are especially important for batteries used in electric vehicles and other high demand technologies, where durability and safety are critical.

"Electrification of society needs everyone's contribution," said one of the corresponding authors 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."

Why New Battery Materials Fell Short

For years, engineers have struggled with cracking in lithium ion batteries that use polycrystalline nickel rich materials (PC-NMC) in their cathodes. These materials are made of many tiny crystal grains packed together, and repeated charging and discharging can cause them to fracture. To avoid this issue, researchers began shifting toward single-crystal nickel rich layered oxides (SC-NMC), which lack those internal grain boundaries.

Despite the promise, single-crystal cathodes did not always perform as well as expected. The new study explains why. The research was led by Jing Wang during her PhD work at UChicago PME through the GRC program, under the joint supervision of Prof. Shirley Meng's Laboratory for Energy Storage and Conversion and Amine's Advanced Battery Technology team.

The team found that design rules developed for polycrystalline cathodes were being incorrectly applied to single-crystal materials. That mismatch, they discovered, was at the heart of the performance problems.

Through the GRC program and UChicago's Energy Transition Network, Wang collaborated closely with national laboratory scientists and industry partners to push the research forward.

"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."

Rethinking Battery Design and Materials

The findings challenge both traditional battery design strategies and assumptions about which elements help or hurt performance. In particular, the study reshapes the understanding of how cobalt and manganese influence mechanical failure inside batteries.