Characterization of SEI layers on LiMn2O4 cathodes with in-situ spectroscopic ellipsometry

Abstract

In situ spectroscopic ellipsometry was employed to study the initial stage of SEI layer formation on thin-film LiMn 2 O 4 electrodes. It was found that the SEI layer formed immediately upon exposure of the electrode to EC/DMC (1:1 by vol) 1.0 M LiPF 6 electrolyte. The SEI layer thickness then increased in proportion to a logarithmic function of elapsed time. In comparison, the SEI layer thickness on a cycled electrode increased in proportion to a linear function of the number of cycles.

LiMn2O4 Surface Chemistry Evolution during Cycling Revealed by in Situ Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy

“…1.5− 1.65 nm SEI layer is present after exposure to carbonate based electrolyte and subsequent electrochemical cycling. 16 Delithiating to voltages >4.4 V also alters the near surface crystal structure and chemistry that transforms to Mn 3 O 4 -like material. 17 In situ Fourier transform infrared (FTIR) spectroscopy of LMO in ethylene carbonate (EC) -diethyl carbonate (DEC) based electrolyte indicates that during delithiation C O and COC peak intensities increase rapidly between 3.9 and 4.2 V, after which they steadily decrease with increasing voltage.…”

Interface Investigations of a Commercial Lithium Ion Battery Graphite Anode Material by Sputter Depth Profile X-ray Photoelectron Spectroscopy

“…X-ray photoelectron spectroscopy (XPS) is a rather powerful method of investigating the SEI. Compared to other methods such as impedance spectroscopy, spectroscopic ellipsometry, , and transmission electron spectroscopy, XPS can obtain very detailed information about the chemical composition of the SEI. However, the use of composite electrodes, as deployed in the battery, leads to drawbacks in the XPS technique.…”