Santhana Eswara1 Alisa Pshenova1 Venkata Siva Varun Sarbada2 Lluís Yedra1 Andrew Kercher3 Kenneth Takeuchi4 5 Amy Marschilok4 5 6 Esther Takeuchi4 5 6 Nancy Dudney3 Tom Wirtz1 Robert Hull2

1, Advanced Instrumentation for Ion Nano-Analytics (AINA), MRT Department, Luxembourg Institute of Science and Technology, Belvaux, , Luxembourg
2, Dept. of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York, United States
3, Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
4, Dept. of Materials Science and Chemical Engineering, Stony Brook University, The State University of New York, Stony Brook, New York, United States
5, Dept. of Chemistry, Stony Brook University, The State University of New York, Stony Brook, New York, United States
6, Energy Sciences Directorate, Brookhaven National Laboratory, Upton, New York, United States

The performance of electrochemical energy materials depends crucially on the underlying nanoscale processes. The charge-discharge cycles of batteries result in gradual changes in nanoscale structure and chemistry of the different electrode layers with often detrimental consequences for the electrochemical properties [1]. To understand the nanoscale mechanisms causing the degradation of the battery materials and to develop strategies to counteract, high resolution imaging and analysis techniques are indispensable. While high-resolution Transmission Electron Microscopy (TEM) enables imaging of the nanostructures down to atomic resolution, analysis of light elements (Z < 6) and low concentrations (< 0.1 at. %) are difficult using typing analytical tools in a TEM such as Energy Dispersive X-ray Spectroscopy. In comparison, Secondary Ion Mass Spectrometry (SIMS) has an excellent sensitivity (can be as low as ppm range) and all the elements (including isotopes) of the periodic table can be analysed. However, the SIMS image resolution is limited to ~ 50 nm in most commercial SIMS instruments (except some new developments [2] where resolution < 20 nm has been demonstrated). Nevertheless, the resolution is still more than 2 orders of magnitude poorer than TEM imaging. To complement the strengths of TEM and SIMS in the same instrument, we developed an in-situ correlative microscopy technique combining TEM-SIMS [3, 4]. In this presentation, we will demonstrate the application of this new nanoscale characterization technique to elucidate the structural and chemical changes occurring in Li ion battery cathodes containing LiV3O8 thin film with different initial microstructures obtained by thermal annealing. Bright-Field TEM and corresponding SIMS images (e.g. Li+ and V+ maps) from uncycled and cycled samples were obtained to investigate the underlying materials phenomena (such as vanadium dissolution) in the cycled cathodes and to correlate the nanoscale processes with macroscopic electrochemical performance [5].
[1] Q. Zhang et al, Journal of The Electrochemical Society, 164 (7) A1503-A1513 (2017)
[2] D. Dowsett, T. Wirtz, Anal. Chem. 89 (2017) 8957-8965
[3] T. Wirtz, P. Philipp, J.-N. Audinot, D. Dowsett, S. Eswara, Nanotechnology, Vol. 26, 434001, 2015.
[4] L. Yedra, S. Eswara, D. Dowsett, T. Wirtz, Sci. Rep. 6, 28705, 2016
[5] Acknowledgements: LVO cathode samples are synthesized as part of the Center for Mesoscale Transport Properties, an Energy Frontier Research Center supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under award #DE-SC0012673.