(Invited) Advanced Photoelectron Spectroscopy on Battery Materials: Lessons Learnt on Silicon- Containing Electrodes

Abstract

While Silicon (Si) is being incorporated more and more as an active material in commercial lithium-ion batteries, it is still a topic of intense research and the motivation for these research efforts remains unchanged: Silicon’s large volume expansion during cycling leads rapid capacity fading largely associated with changes in the Si surface chemistry and unstable solid electrolyte interphase (SEI). Using advanced photoelectron spectroscopy (PES) characterization, we have investigated crucial interfaces on Si model systems and Si-containing negative electrodes for Li-ion batteries. Here, we focus on two approaches to influence the SEI composition intrinsically: Binders and electrolytes.Starting with pristine Si powders, we studied the effect of carboxylic acids as electrode slurry additives on the Si surface chemistry before and after electrochemical cycling [1] using synchrotron PES depth profiling. Further, we used photoelectron spectroscopy to confirm cross-linking in poly-acrylic acid-based binder for Si electrodes and showed that the cross-linking agent pentaerythritol had no negative effect on the SEI thus attributing improved cycling performance to increased binder cross-linking [2].In silicon/graphite negative electrodes, we used PES to elucidate the influence of fluoroethylene carbonate (FEC) on the degradation phenomena in electrodes with varying silicon content [3]. Finally, photoelectron spectroscopy provided insights into what happens to the SEI on Si-containing electrodes if we replace the classical electrolyte solvent ethylene carbonate with either FEC or glyoxylic acetal-based alternatives [4, 5].[1] F. Jeschull, H.Q. Pham, A. Ghamlouche, P.K. Thakur, S. Trabesinger, J. Maibach, J. Phys. Energy 2023, 5 (2), 025002. https://doi.org/10.1088/2515-7655/acbbee.[2] J. He, C. Das, F. Yang, J. Maibach, Electrochimica Acta 2022, 411, 140038. https://doi.org/10.1016/j.electacta.2022.140038.[3] A. Ghamlouche, M. Müller, F. Jeschull, J. Maibach, J. Electrochem. Soc. 2022. https://doi.org/10.1149/1945-7111/ac4cd3.[4] L. Gehrlein, C. Njel, F. Jeschull, J. Maibach, ACS Appl. Energy Mater. 2022, 5 (9), 10710–10720. https://doi.org/10.1021/acsaem.2c01454.[5] L. Gehrlein, C. Leibing, K. Pfeifer, F. Jeschull, A. Balducci, J. Maibach, Electrochimica Acta 2022, 140642–140642. https://doi.org/10.1016/j.electacta.2022.140642.