Power Electronics

Research Demystifies New Cathode Materials

Scientists at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory are investigating a group of new materials with the potential to improve the performance of Li-ion batteries. According to a recently published article by Laura Mgrdichian*, the scientists are studying a group of new cathode compounds consisting of lithium, cobalt, nickel, manganese, and oxygen.



“Despite the wide use of lithium-ion batteries, there have been very few studies on exactly how the cathode material behaves in the charging process,” said the study’s lead researcher, Brookhaven chemist Won-Sub Yoon. “How are the oxygen atoms involved? What is the relationship between the oxygen atoms and the other metal atoms in the compound? To design a better cathode material, and thus a better battery, these questions must be answered. An in-depth understanding of these problems will provide a road map for the development of these new materials.”



In addition to Yoon, the research group included Kyung Yoon Chung, Xiao-Qing Yang, and James McBreen, who are members of BNL’s Chemistry Department); Mahalingam Balasubramanian of Argonne National Laboratory; Clare Grey of Stony Brook University; and Daniel Fischer of the National Institute of Standards and Technology.



The scientists used x-ray techniques to discover how the various elements of the cathode change during battery charging. For example, as lithium ions exit the cathode, the nickel atoms lose electrons, but the manganese and cobalt atoms do not. Scientists also learned that positively charged “holes” are created in the cathode to compensate for the positive charges lost as lithium ions migrate to the anode. Moreover, scientists learned that these holes appear within the electron orbitals of oxygen atoms bound to the cobalt atoms.



These findings are expected to aid the development of better performing Li-ion batteries constructed using the new cathode materials. For more details on this research see “Investigation of the Charge Compensation Mechanism on the Electrochemically Li-Ion Deintercalated Li1-xCo1/3Ni1/3Mn1/3O2 Electrode System by Combination of Soft and Hard X-ray Absorption Spectroscopy” by Yoon, Balasubramanian, et al. This paper was published in the December 14, 2005, edition of the Journal of the American Chemical Society and is available online at http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2005/127/i49/abs/ja0530568.html .



* “At the NSLS, Scientists Working Toward Better Batteries,” available online at
http://www.bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=06-X8


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