XPS Analysis of K-based Reference Compounds to Allow Reliable Studies of Solid Electrolyte Interphase in K-ion Batteries

Abstract

As for Li-and Na-ion batteries, the electrolyte reactivity (i.e. the salts and solvents decomposition) also plays a crucial role on the electrochemical performance of K-ion batteries (KIBs). However, X-ray photoelectron spectroscopy (XPS) analysis of the solid electrolyte interphase (SEI) in KIBs remains based on Li-ion and Na-ion literature so far. This may lead to incorrect interpretations of the results considering that the first ionisation potential difference between the alkali metals is expected to significantly change the binding energy values observed by XPS for a given M-based (M=Li, Na or K) compound. Therefore, this work aims at providing XPS characterization of numerous commercial K-based reference compounds, including some that were still missing in the literature. In particular, absolute and relative binding energy values are given and compared to corresponding Li and Na counterparts. This work will thus help researchers to get reliable XPS analysis of the SEI in KIBs.

Impact of the Salt Anion on K Metal Reactivity in EC/DEC Studied Using GC and XPS Analysis

“…XPS quantification was performed using the relative sensitivity factor provided with the Escalab machine. Quantification values were consistent with the stoichiometry of the deducted compounds and were based on a K reference compound database previously reported by some of us …”

“…Quantification values were consistent with the stoichiometry of the deducted compounds and were based on a K reference compound database previously reported by some of us. 25 ■ RESULTS AND DISCUSSION Visual Inspection and Gas Chromatography. Figure 3 shows the GC/MS and GC/FTIR spectra obtained for the K metal (green) and Li metal (red) after storage for 3 weeks in EC/DEC, 0.8 M MPF 6 EC/DEC, and 0.8 M KFSI EC/DEC as well as a summary of all gases detected and photos of metalcorresponding electrodes.…”

Comparing the Solid Electrolyte Interphases on Graphite Electrodes in K and Li Half Cells

“…Therefore, in this first part a small XPS reference table was generated to confirm binding energies from relevant and existing entries (KF, K 3 PO 4 , and CH 3 COOK), as well as to add new entries of SEI-characteristic compounds such as K 2 CO 3 and KPF 6 . In addition, our results are compared to a recently published work of Caracciolo et al for validation.…”

“…Previously reported BEs for K 2 CO 3 lie in the range of 288.6−289.0 eV. 16,17 Differences may also relate to slightly different points of reference. For potassium acetate (CH 3 COOK), the signal intensity of the CH 3 -group is overlapping with the signal of the Cu-tape at 285 eV, which leads to a significant overestimation of the atomic ratio for this carbon signal.…”

High-performance SiO electrodes for lithium-ion batteries: merged effects of a new polyacrylate binder and an electrode-maturation process

“…Thus, the binding energy of the F 1s spectrum is possibly shifted a few eV higher than that of the C 1s spectrum used for calibration, resulting in the appearance of unidentified peaks in the 690-695 eV range. In the HAXPES spectra of LiF and LiPF 6 composite mixed with AB and polyvinyl alcohol binder on Cu foil (Figure S8), a broad peak shifted to higher binding energies than the reference peak, 43,48 indicating that the F 1s spectrum may be strongly influenced by the charge-up effect. In the P 1s spectra…”