Researchers at the US Department of Energy’s (DOE) Argonne National Laboratory have a long history of pioneering discoveries in the field of lithium-ion batteries. Many of these results are for the battery cathode, called NMC, nickel manganese and cobalt oxide. A battery with this cathode now powers the Chevrolet Bolt.
Argonne researchers have achieved another breakthrough in NMC cathodes. The team’s new tiny cathode particle structure could make the battery more durable and safer, able to operate at very high voltages and provide longer travel ranges.
“We now have guidance that battery manufacturers can use to make high-pressure, borderless cathode materials,” Khalil Amin, Argonne Fellow Emeritus.
“Existing NMC cathodes present a major hurdle for high voltage work,” said assistant chemist Guiliang Xu. With charge-discharge cycling, performance drops rapidly due to the formation of cracks in the cathode particles. For decades, battery researchers have been looking for ways to repair these cracks.
One method in the past used tiny spherical particles composed of many much smaller particles. Large spherical particles are polycrystalline, with crystalline domains of various orientations. As a result, they have what scientists call grain boundaries between particles, which can cause the battery to crack during a cycle. To prevent this, Xu and Argonne’s colleagues had previously developed a protective polymer coating around each particle. This coating surrounds large spherical particles and smaller particles within them.
Another way to avoid this kind of cracking is to use single crystal particles. Electron microscopy of these particles showed that they have no boundaries.
The problem for the team was that cathodes made from coated polycrystals and single crystals still cracked during cycling. Therefore, they conducted extensive analysis of these cathode materials at the Advanced Photon Source (APS) and Center for Nanomaterials (CNM) at the US Department of Energy’s Argonne Science Center.
Various x-ray analyzes were performed on five APS arms (11-BM, 20-BM, 2-ID-D, 11-ID-C and 34-ID-E). It turns out that what scientists thought was a single crystal, as shown by electron and X-ray microscopy, actually had a boundary inside. Scanning and transmission electron microscopy of CNMs confirmed this conclusion.
“When we looked at the surface morphology of these particles, they looked like single crystals,” said physicist Wenjun Liu. â�<“但是，当我们在APS 使用一种称为同步加速器X 射线衍射显微镜的技术和其他技术时，我们发现边界隐藏在内部。” â� <“但是 ， 当 在 在 使用 使用 种 称为 同步 加速器 x 射线 显微镜 的 技术 和 其他 时 ， 我们 发现 边界 隐藏 在。” “However, when we used a technique called synchrotron X-ray diffraction microscopy and other techniques at APS, we found that the boundaries were hidden inside.”
Importantly, the team has developed a method to produce single crystals without boundaries. Testing small cells with this single-crystal cathode at very high voltages showed a 25% increase in energy storage per unit volume with virtually no loss in performance over 100 test cycles. In contrast, NMC cathodes composed of multi-interface single crystals or coated polycrystals showed a capacity drop of 60% to 88% over the same lifetime.
Atomic scale calculations reveal the mechanism of cathode capacitance reduction. According to Maria Chang, a nanoscientist at CNM, boundaries are more likely to lose oxygen atoms when the battery is charged than areas further away from them. This loss of oxygen leads to degradation of the cell cycle.
“Our calculations show how the boundary can lead to oxygen being released at high pressure, which can lead to reduced performance,” Chan said.
Eliminating the boundary prevents oxygen evolution, thereby improving the safety and cyclic stability of the cathode. Oxygen evolution measurements with APS and an advanced light source at the US Department of Energy’s Lawrence Berkeley National Laboratory confirm this conclusion.
“Now we have guidelines that battery manufacturers can use to make cathode materials that have no boundaries and operate at high pressure,” said Khalil Amin, Argonne Fellow Emeritus. â�<“该指南应适用于NMC 以外的其他正极材料。” â�<“该指南应适用于NMC 以外的其他正极材料。” “Guidelines should apply to cathode materials other than NMC.”
An article about this study appeared in the journal Nature Energy. In addition to Xu, Amin, Liu and Chang, the Argonne authors are Xiang Liu, Venkata Surya Chaitanya Kolluru, Chen Zhao, Xinwei Zhou, Yuzi Liu, Liang Ying, Amin Daali, Yang Ren, Wenqian Xu , Junjing Deng, Inhui Hwang, Chengjun Sun, Tao Zhou, Ming Du, and Zonghai Chen. Scientists from the Lawrence Berkeley National Laboratory (Wanli Yang, Qingtian Li, and Zengqing Zhuo), Xiamen University (Jing-Jing Fan , Ling Huang and Shi-Gang Sun) and Tsinghua University (Dongsheng Ren, Xuning Feng and Mingao Ouyang).
About the Argonne Center for Nanomaterials The Center for Nanomaterials, one of five US Department of Energy nanotechnology research centers, is the premier national user institution for interdisciplinary nanoscale research supported by the US Department of Energy’s Office of Science. Together, NSRCs form a suite of complementary facilities that provide researchers with state-of-the-art capabilities for fabricating, processing, characterizing, and modeling nanoscale materials and represent the largest infrastructure investment under the National Nanotechnology Initiative. The NSRC is located at the US Department of Energy National Laboratories in Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia, and Los Alamos. For more information about the NSRC DOE, visit https://​science​.osti​.gov/​Us​er​-​F​a​c​i​lit​​​​​ie​s​/ ​Us​ er​-​F​a​c​i​l​it​ie​ie​s​-​at​-a​​Glance.
The US Department of Energy’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the most productive X-ray sources in the world. APS provides high-intensity X-rays to a diverse research community in materials science, chemistry, condensed matter physics, life and environmental sciences, and applied research. These X-rays are ideal for studying materials and biological structures, the distribution of elements, chemical, magnetic and electronic states, and technically important engineering systems of all kinds, from batteries to fuel injector nozzles, which are vital to our national economy, technology. and body The basis of health. Each year, more than 5,000 researchers use APS to publish more than 2,000 publications detailing important discoveries and solving more important biological protein structures than users of any other X-ray research center. APS scientists and engineers are implementing innovative technologies that are the basis for improving the performance of accelerators and light sources. This includes input devices that produce extremely bright X-rays prized by researchers, lenses that focus X-rays down to a few nanometers, instruments that maximize the way X-rays interact with the sample under study, and the collection and management of APS discoveries Research generates huge data volumes.
This study utilized resources from Advanced Photon Source, a US Department of Energy Office of Science User Center operated by Argonne National Laboratory for the US Department of Energy Office of Science under contract number DE-AC02-06CH11357.
The Argonne National Laboratory strives to solve the pressing problems of domestic science and technology. As the first national laboratory in the United States, Argonne conducts cutting-edge basic and applied research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state, and municipal agencies to help them solve specific problems, advance US scientific leadership, and prepare the nation for a better future. Argonne employs employees from over 60 countries and is operated by UChicago Argonne, LLC of the US Department of Energy’s Office of Science.
The Office of Science of the US Department of Energy is the nation’s largest proponent of basic research in the physical sciences, working to address some of the most pressing issues of our time. For more information, visit https://​energy​.gov/​science​ience.