Surface analysis insight note: X‐ray photoelectron spectroscopy analysis of battery electrodes—Challenges with nickel–manganese–cobalt and Li examples using an Al Kα x‐ray source

Abstract

X‐ray photoelectron spectroscopy (XPS) has become a highly important tool for the analysis of battery materials and components. However, both anecdotal and detailed analysis of selected parts of the literature indicate that many reports of XPS on battery electrodes have significant analysis or data flaws. In this paper, we highlight several of the common challenges that analysts face when using XPS for battery materials, pointing to recent literature that addresses many of the critical issues associated with sample preparation as well as data collection and analysis. A common error for battery materials (and other materials) involves ignoring peak overlaps and interferences. Specifically, when a “minor” peak associated with a component in relatively high concentration overlaps or contributes to the primary peak (or one recommended for quantitative analysis) from a different element in the material. Overlap issues apply to many battery electrodes composed of many elements with complex photoelectron peak structures, as well as those involving peaks with seemingly simpler spectral envelopes such as Li and F. Examples of issues associated with battery systems are highlighted by a discussion of challenges associated with XPS analysis of Li and nickel–manganese–cobalt (NMC) electrodes in battery systems. Lithium analysis has challenges associated with the preparation and an often‐unrecognized peak overlap with F. In our laboratory and in the literature, NMC electrodes are often examined and new XPS users do not always recognize interference of the Auger signal from FKLL (in or on the electrode) with Ni 2p photoelectron spectrum when generated with Al Kα X‐rays. The use of simulated spectra involving both F and NiO demonstrates the extent of F Auger contributions to the Ni 2p signal strength as a function of the F/Ni atom ratio in the material and suggests spectra information that can be used to identify how significant effects will be on the resultant spectra. Our analysis demonstrates that in many cases overlap issues are significant for real electrode materials.

Stable Supercapacitors Based on Activated Carbon Prepared from Italian Orange Juice

“…X-ray photoelectron spectroscopy (XPS) provides in-depth insight into the elemental composition, chemical state, and electronic state of the elements present in a material [ 46 ]. From Figure 5 and Table 3 , a detailed understanding of the surface chemistry of the 5:1@120 AC sample can be extrapolated.…”

“…In essence, the increasing KOH ratio not only aids in diminishing defects but also promotes the formation of layered carbon structures, making the samples progressively more graphitic. X-ray photoelectron spectroscopy (XPS) provides in-depth insight into the elemental composition, chemical state, and electronic state of the elements present in a material [46]. From Figure 5 and Table 3, a detailed understanding of the surface chemistry of the 5:1@120 AC sample can be extrapolated.…”

Surface analysis insight note: Accounting for X‐ray beam damage effects in positive electrode‐electrolyte interphase investigations

“…Several sources of artifacts can result from beam damage during physical and chemical characterization. The use of Ar-ion and gas-cluster ion beams (GCIB) to perform depth profiling by X-ray photoemission spectroscopy (XPS), [6][7][8][9][10] time of flight secondary ions mass spectroscopy (ToF-SIMS), [11][12][13] or focused ion beam (FIB) [14][15][16] induces SEI chemical and morphological changes due to the preferential etching occurring during beam exposure. Exposure to the electron gun when using scanning electron microscopy (SEM) or transmission electron microscopy (TEM) [17][18][19] can also be a source of damage due to charging effects and local heating induced by electrical current density dispersed through the SEI.…”