Solid Electrolyte Interphase (SEI) at TiO2 Electrodes in Li-Ion Batteries: Defining Apparent and Effective SEI Based on Evidence from X-ray Photoemission Spectroscopy and Scanning Electrochemical Microscopy

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• 作者：Edgar VentosaEdyta Madej ; Giorgia Zampardi ; Bastian Mei ; Philipp WeideHendrik Antoni ; Fabio La Mantia ; Martin Muhler ; Wolfgang Schuhmann
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2017
• 出版时间：January 25, 2017
• 年：2017
• 卷：9
• 期：3
• 页码：3123-3130
• 全文大小：506K
• ISSN：1944-8252

文摘

The high (de)lithiation potential of TiO₂ (ca. 1.7 V vs Li/Li⁺ in 1 M Li⁺) decreases the voltage and, thus, the energy density of a corresponding Li-ion battery. On the other hand, it offers several advantages such as the (de)lithiation potential far from lithium deposition or absence of a solid electrolyte interphase (SEI). The latter is currently under controversial debate as several studies reported the presence of a SEI when operating TiO₂ electrodes at potentials above 1.0 V vs Li/Li⁺. We investigate the formation of a SEI at anatase TiO₂ electrodes by means of X-ray photoemission spectroscopy (XPS) and scanning electrochemical microscopy (SECM). The investigations were performed in different potential ranges, namely, during storage (without external polarization), between 3.0–2.0 V and 3.0–1.0 V vs Li/Li⁺, respectively. No SEI is formed when a completely dried and residues-free TiO₂ electrode is cycled between 3.0 and 2.0 V vs Li/Li⁺. A SEI is detected by XPS in the case of samples stored for 6 weeks or cycled between 3.0 and 1.0 V vs Li/Li⁺. With use of SECM, it is verified that this SEI does not possess the electrically insulating character as expected for a “classic” SEI. Therefore, we propose the term apparent SEI for TiO₂ electrodes to differentiate it from the protecting and effective SEI formed at graphite electrodes.