Sep 22 2022Reviewed by Mila Perera
Scientists at the University of California, Irvine, and four national laboratories have formulated a method to create lithium-ion battery cathodes without adding cobalt, as cobalt is plagued by price instability and geopolitical impediments.
Working with researchers at four US national laboratories, Huolin Xin, UCI Professor of Physics & Astronomy, has found a way to fabricate lithium-ion batteries without using cobalt, a rare, costly mineral extracted under inhumane conditions in Central Africa. Image Credit: Steve Zylius/UCI
The researchers explain how they surpassed the chemical, mechanical, and thermal variability of cathodes largely made up of nickel — a typical alternative for cobalt — by including many other metallic elements. The study was published in Nature.
Through a technique we refer to as ‘high-entropy doping,’ we were able to successfully fabricate a cobalt-free layered cathode with extremely high heat tolerance and stability over repeated charge and discharge cycles. This achievement resolves long-standing safety and stability concerns around high-nickel battery materials, paving the way for broad-based commercial applications.
Huolin Xin, Study Corresponding Author and Professor, Physics and Astronomy, University of California, Irvine
According to the article’s authors, cobalt is a significant supply chain hazard obstructing the extensive adoption of electric trucks, cars, and other electronic gadgets necessitating batteries.
The mineral, chemically well-matched to stabilize lithium-ion battery cathodes, is almost exclusively mined in the Democratic Republic of Congo under cruel and abusive circumstances.
Electric vehicle manufacturers are eager to curtail the use of cobalt in their battery packs not only for cost reduction but to counter the child labor practices used to mine the mineral. Research has also shown that cobalt can lead to oxygen release at high voltage, causing damage to lithium-ion batteries. All of this points to a need for alternatives.
Huolin Xin, Study Corresponding Author and Professor, Physics and Astronomy, University of California, Irvine
Nickel-based cathodes have their own issues, however, like low heat tolerance, which can result in thermal runaway, oxidization of battery materials, and even explosions.
While high-nickel cathodes can handle larger capacities, volume strain from recurrent expansion and contraction can cause poor stability and safety issues.
The scientists aimed to look into these problems through compositionally multifaceted high-entropy doping using HE-LMNO, a combination of transition metals such as molybdenum, titanium, manganese, magnesium, and niobium in the interior of the structure, with a subset of these minerals applied on its surface and interface with other battery constituents.
Xin and his colleagues used various transmission electron microscopy, synchrotron X-Ray diffraction, and 3D nanotomography instruments to establish that their zero-cobalt cathode showed an unparalleled volumetric change of zero during recurrent use. The stable structure can endure high temperatures and over 1,000 cycles, comparable to cathodes possessing much lower nickel quantity.
For some of these study tools, Xin worked with scientists at the National Synchrotron Light Source II (NSLS-II), situated at the US Department of Energy’s Brookhaven National Laboratory in New York.
As a DOE Office of Science user facility, NSLS-II let the team use three of its 28 scientific instruments — known as beamlines — to explore the inner structure of the new cathode.
The combination of the different methods at NSLS II beamlines enabled the discovery of a trapping effect of oxygen vacancies and defects inside the material, which effectively prevents the crack formation in the HE-LMNO secondary particle, making this structure extremely stable during cycling.
Mingyuan Ge, Study Co-Author and Scientist, NSLS-II
“Using these advanced tools, we were able to observe the dramatically increased thermal stability and zero-volumetric-change characteristics of the cathode, and we’ve been able to demonstrate extraordinarily 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.
He stated that the study is a step closer to realizing the twin goal of stimulating the spread of clean transportation and energy storage while resolving environmental justice problems surrounding the mining of minerals used to manufacture batteries.
This study was funded by the US Department of Energy Office of Energy Efficiency and Renewable Energy.
The study also involved scientists from Washington’s Pacific Northwest National Laboratory, Illinois’ Argonne National Laboratory, and California’s SLAC National Accelerator Laboratory.
Journal Reference
Zhang, R., et al. (2022) Compositionally complex doping for zero-strain zero-cobalt layered cathodes. Nature. doi.org/10.1038/s41586-022-05115-z.
Source: https://news.uci.edu