Cobalt-Free Cathode Developed for Lithium-Ion Batteries

Scientists at the University of California, Irvine, and four national labs have developed a method to make lithium-ion battery cathodes without adding cobalt, as price instability and geopolitical obstacles have plagued cobalt.

Cobalt-free cathode developed for lithium-ion batteries

Huolin Xin, UCI professor of physics and astronomy, in collaboration with researchers from four US national laboratories, has found a way to make lithium-ion batteries without the use of cobalt, a rare, costly mineral grown in inhumane conditions in central Africa is dismantled. Credit: Steve Zylius/UCI

The researchers explain how they surpassed the chemical, mechanical and thermal variability of cathodes made largely of nickel – a typical alternative for cobalt – by incorporating many other metallic elements. The study was published in Nature.

Through a technique we refer to as “high entropy doping”, we have successfully fabricated a cobalt-free layered cathode with extremely high thermal tolerance and stability over repeated charge and discharge cycles. This achievement resolves long-standing safety and stability concerns related to high-nickel battery materials and paves the way for broad-based commercial applications.

Huolin Xin, corresponding study author and professor, Physics and Astronomy, University of California, Irvine

According to the authors of the article, cobalt poses a significant threat to the supply chain that is hampering the widespread adoption of electric trucks, cars and other electronic devices that require batteries.

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The mineral, which is chemically well-suited to stabilizing lithium-ion battery cathodes, is mined almost exclusively in the Democratic Republic of the Congo under cruel and abusive conditions.

Electric vehicle manufacturers are striving to limit the use of cobalt in their battery packs, not only to reduce costs but also to discourage child labor practices in mining the mineral. Research has also shown that at high voltage, cobalt can lead to the release of oxygen, which can damage lithium-ion batteries. All of this points to the need for alternatives.

Huolin Xin, corresponding study author and professor, Physics and Astronomy, University of California, Irvine

However, nickel-based cathodes have their own problems, such as B. Poor heat tolerance that can lead to thermal runaway, oxidation of battery materials, and even explosion.

While high-nickel cathodes can handle larger capacities, volume stress from repetitive expansion and contraction can cause poor stability and safety issues.

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Scientists aimed to investigate these issues through compositionally multifaceted high-entropy doping using HE-LMNO, a combination of transition metals such as molybdenum, titanium, manganese, magnesium and niobium inside the structure, with a subset of these minerals on its surface and interface with applied to other battery components.

Xin and his colleagues used various transmission electron microscopy, synchrotron X-ray diffraction and 3D nanotomography instruments to determine that their zero cobalt cathode showed an unprecedented zero volume change with repeated use. The stable structure withstands high temperatures and over 1,000 cycles, comparable to cathodes with much lower nickel content.

For some of these study tools, Xin worked with scientists at the National Synchrotron Light Source II (NSLS-II), located at the US Department of Energy’s Brookhaven National Laboratory in New York.

As the DOE Office of Science user facility, NSLS-II had the team use three of its 28 science instruments — known as beamlines — to probe the internal structure of the new cathode.

The combination of the different methods on NSLS II beamlines enabled the discovery of a trapping effect of oxygen vacancies and defects inside the material, which effectively prevents cracking in the HE-LMNO secondary particle and makes this structure extremely stable during cycling.

Mingyuan Ge, study co-author and researcher, NSLS-II

With these advanced tools, we have been able to observe the dramatically increased thermal stability and properties of the cathode with no volume change, and demonstrate greatly improved capacity retention and cycle life. This research could set the stage for the development of an energy-dense alternative to existing batteries‘ Xin added.

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He explained that the study is one step closer to realizing the twin goals of promoting the spread of clean transportation and energy storage while addressing the environmental justice issues related to the mining of minerals used to make batteries .

This study was funded by the US Department of Energy Office of Energy Efficiency and Renewable Energy.

The study also involved scientists from the Pacific Northwest National Laboratory in Washington, Argonne National Laboratory in Illinois and the SLAC National Accelerator Laboratory in California.

magazine reference

Zhang, R. et al. (2022) Compositional complex doping for zero-strain cobalt layered cathodes. Nature.


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