Structure Formation and Thermal Stability of Mono- and Multilayers of Ethylene Carbonate on Cu(111): A Model Study of the Electrode|Electrolyte Interface

Abstract

In this work, we aim at a molecular scale understanding of the interactions and structure formation at the electrode|electrolyte interface (EEI) in Li-ion batteries. Therefore, the interaction of the key electrolyte component ethylene carbonate (EC) with Cu(111) was investigated under ultrahigh vacuum conditions. Scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIRS), and dispersion-corrected density functional theory (DFT-D) calculations were employed. After vapor deposition of EC (sub-) monolayers on Cu(111) at 80 K, STM measurements (100 K) reveal a well-ordered commensurate superstructure, in which EC molecules assume different configurations and whose total adsorption energy is mainly governed by van der Waals interactions, as demonstrated by DFT-D. In the temperature range between 150−220 K, competing desorption and decomposition into −CO, −C−O−C−, −C−H, and −C−C− compounds, as derived by XPS and confirmed by FTIRS, result in distinct changes of the adlayer composition. Similar heating of an EC multilayer film from 80 K to room temperature results in a surface that is almost completely covered with adsorbed, carboncontaining decomposition products. This can be interpreted as the initial stage of chemical EEI formation, and the relevance of these results for battery applications is discussed.

Investigation on the Thermal Stability of Li2MnSiO4‐Based Cathodes for Li‐ion Batteries: Effect of Electrolyte and State of Charge

“…[49] Finally,t he small peak at 288.5 eV can be ascribed to C=Of ragments,w hich are most probably related to EC/DMC or their decomposition products. [50] Thes pectra in the C1sr egion arev ery similar with regard to intensity,p eak shape,a nd position for all three SOCs studied. Based on these findings,w ee xcludet he build-up of an extendedS EI film during cycling, which is usuallyf ormed at the electrode surface at high potentials and contains chemical species such as ROCO 2 Li, ROLi, or polycarbonates.…”

Insights into the reversibility of aluminum graphite batteries

“…Very likely, the peak at the highest binding energy (289.1 eV) is related to residual solvent from the rinsing process. 39 The peak at 286.5 eV can be associated with the oxidation of graphite C atoms, occurring upon the intercalation of AlCl 4 À . This is in agreement with the well-known redox-amphoteric behavior of graphite when used as intercalation host.…”

Interaction of Ultrathin Films of Ethylene Carbonate with Oxidized and Reduced Lithium Cobalt Oxide—A Model Study of the Cathode|Electrolyte Interface in Li‐Ion Batteries

“…One possible way to determine the initial stages of the SEI formation at the EEI at the atomic/molecular level involves the use of surface science techniques, studying the interaction of individual components of electrolytes, such as the typical key component EC (or other electrolyte components like ionic liquids), with well‐defined model electrodes under idealized ultrahigh‐vacuum (UHV) conditions, which is focus of the ongoing work in our laboratory. Following a previous study on the interaction of EC with Li‐free and lithiated highly oriented pyrolytic graphite (HOPG) as model for the anode, we here report the results of a similar type of study on the interaction of EC with well‐defined LiCoO 2 electrode surfaces, both fully oxidized LiCoO 2 and partly reduced LiCoO 2− δ surfaces, as models for the cathode.…”

“…This was derived from desorption of fragments like C 2 H 4 , C 2 H 4 O, and CO 2 , upon heating (possible products of the above Li‐containing species). Using scanning tunneling microscopy and X‐ray photoelectron spectroscopy (XPS) in combination with dispersion‐corrected density functional theory calculations to study the interaction of ultrathin EC films with Cu(111), we found that adsorbed EC molecules self‐assemble into a well‐ordered 2D arrangement on Cu(111) at 80 K, and that competing desorption and decomposition set in at ≈170 K . Studies on the interaction of battery‐relevant solvents with LiCoO 2 have been conducted for DEC, water, and dimethyl sulfoxide (DMSO) with the samples cooled to ≈110 K .…”