Abstract
In this article, we present Near Ambient Pressure (NAP)-X-ray Photoelectron Spectroscopy (XPS) results from model and commercial liquid electrolytes for lithium-ion battery production using an automated laboratory NAP-XPS system. The electrolyte solutions were (i) LiPF6 in EC/DMC (LP30) as a typical commercial battery electrolyte and (ii) LiTFSI in PC as a model electrolyte. We analyzed the LP30 electrolyte solution, first in its vapor and liquid phase to compare individual core-level spectra. In a second step, we immersed a V2O5 crystal as a model cathode material in this LiPF6 solution. Additionally, the LiTFSI electrolyte model system was studied to compare and verify our findings with previous NAP-XPS data. Photoelectron spectra recorded at pressures of 2–10 mbar show significant chemical differences for the different lithium-based electrolytes. We show the enormous potential of laboratory NAP-XPS instruments for investigations of solid-liquid interfaces in electrochemical energy storage systems at elevated pressures and illustrate the simplicity and ease of the used experimental setup (EnviroESCA).
Highlights
X-ray Photoelectron Spectroscopy (XPS) as a powerful and non-destructive technique for material and surface analysis provides quantitative elemental and chemical information of the studied samples
The second part of our study focused on the model electrolyte based on 1 M bis(trifluoromethane) sulfonimide lithium salt (LiTFSI) in propylene carbonate (PC), which offers the advantage that both salt and solvent signals can be observed and clearly distinguished from each other in Near Ambient Pressure (NAP)-XPS
The immersed V2 O5 single crystal was probed with Near-Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) after cleaning and drying
Summary
X-ray Photoelectron Spectroscopy (XPS) as a powerful and non-destructive technique for material and surface analysis provides quantitative elemental and chemical information of the studied samples. Near Ambient Pressure (NAP) XPS has been developed to enable the analysis of real-world samples under working conditions [1,2,3,4,5]. The transformation of XPS from a UHV-based method towards environmental conditions has revolutionized XPS dramatically and opens completely new fields of research. NAP-XPS is used extensively for in situ measurements and operando studies of industrial relevant (electro) chemical reactions and catalytic processes, especially at gas-liquid, gas-solid, and liquid-solid interfaces [6,7,8,9,10]. Probing realistic battery environments with NAP-XPS is of special interest.
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