The Origin of Stress in the Solid Electrolyte Interphase on Carbon Electrodes for Li Ion Batteries

This paper focuses on stress generation during the initial stages of the Solid Electrolyte Interphase (SEI) formation on graphite electrodes. C-axis oriented graphitic carbon, grown via chemical vapor deposition (CVD), is used as a model system for this study, to enable reliable characterization using Secondary Ion Mass Spectroscopy (SIMS) and X-ray Photo-electron Spectroscopy (XPS). The SET formation was also probed by recording the stress development in-situ during constant voltage holds above the lithium intercalation threshold, using a Multi-beam Optical Stress Sensor (MOSS). This provides direct correlations between the potential, current and stress. SIMS and XPS analysis of the surface chemistry of the cycled samples show high carbon content near the surface. Cross-sectional TEM indicates that these surface layers are predominantly amorphous. Based on the evidence and analysis, the stress in this amorphous layer is believed to play an important role in stabilizing the inorganic SET layer. An understanding of this interlayer can be used to design a more mechanically stable SET layer, and is also potentially relevant to,other electrode materials which show much higher volume expansions. (C) 2013 The Electrochemical Society. All rights reserved