NMR Study of Lithium-Ion Electrode Materials

1. NMR Study of Lithium-Ion Electrode Materials By Christina Zayas, Aquinas High School Hunter College of the City University of New York New York City Research Initiative Mentors: Dr. Steve Greenbaum, Professor of Physics at Hunter College Mr. George Bennett, CUNY Doctoral Student Mr. Ameesh Khalfan, CUNY Doctoral Student

2. Abstract Due to the varying environmental conditions that are present in space, batteries powering spacecrafts need to possess the ability to withstand variable temperatures. In addition, such batteries demand an increased cycle life at low depths of discharge while also requiring mechanical durability and compactness. Nuclear magnetic resonance (NMR) spectroscopy can shed light on a material at the atomic and molecular level. Through the use of a superconducting magnet and the application of electromagnetic radiation, we can learn of the structural properties of a given substance, i.e. a battery electrode. The structural quantities of interest in our study include relaxation times and the characterization of local environments of nuclei. The Jet Propulsion Laboratory (JPL) supplied the materials investigated and the nuclei probed were 7Li and 19F.

3. We can look at the line shapes of NMR absorption spectra of electrode materials prepared or cycled under different conditions to garner information regarding the structural integrity of prospective electrode materials. In terms of procedure, after testing the background of the probe, the sample was placed in the probe which was subsequently raised into the homogeneous field position of the magnet By implementing various radiofrequency pulse techniques, we can manipulate the magnetization to better understand the local environments of nuclei. A background 19F NMR signal was observed on an empty probe. Some of the background signal was suppressed so as to better resolve the signal arising from the actual sample when tested. Method

4. Results 7Li NMR MAS (Magic Angle Spinning) Spectra of a Cathode at Room Temperature   Cathode BF02 Anode BF01 BF02 BF04 BF05 BF06 Fluorine-19 NMR Spectra of Three Anode Materials, the Baseline Electrolyte in Black 7Li NMR MAS Spectra of Anode Materials at Room Temperature

5. Conclusions and Future Work By using NMR spectroscopy to identify the breakdown particles which inhibit the proper functioning of Li-ion batteries, we have concluded that the electrode additives have in fact changed the structural characteristics of the spectrum. Future experimentation will be pursued to further characterize electrode additives and their behavior under different temperatures and chemical conditions. Future experiments include but are not limited to the continuation in the variation of electrode additives and concentrations to help improve their behavior in various temperatures and surface chemistries.

6. References/Acknowledgements Grey, C.P. and Greenbaum, S.G. MRS Bulletin Vol. 27, No. 13; Materials Research Society, 2002. Hornak, J.P. The Basics of NMR. Hornak, 2004. [accessed 2 August 2005] http://www.cis.rit.edu/htbooks/nmr/inside.htm Nuclear Magnetic Resonance Spectroscopy. Sheffield Hallam University, 1999. [accessed 1 August2005] http://www.shu.ac.uk/schools/sci/chem/tutorials/molspec/nmr1.htm Acknowledgements I would like to thank Professor Greenbaum for all of his guidance and his assistance with not only NMR, but with college decisions. I would also like to thank Mr. Bennett for his mentorship, career advice, and words of wisdom. Lastly, I would like to thank Ameesh for taking the time out to explain NMR, help me with this poster, and challenge me with physics problems. Thanks to the members of the NMR lab at Hunter for countless enlightening conversations.