How Bulk Sensitive is Hard X-ray Photoelectron Spectroscopy: Accounting for the Cathode–Electrolyte Interface when Addressing Oxygen Redox

Date Published
02/2020
Publication Type
Journal Article
Authors
DOI
10.1021/acs.jpclett.0c00229
Abstract

Sensitivity to the “bulk” oxygen core orbital makes hard X-ray photoelectron spectroscopy (HAXPES) an appealing technique for studying oxygen redox candidates. Various studies have reported an additional O 1s peak (530–531 eV) at high voltages, which has been considered a direct signature of the bulk oxygen redox process. Here, we find the emergence of a 530.4 eV O 1s HAXPES peak for three model cathodes—Li2MnO3, Li-rich NMC, and NMC 442—that shows no clear link to oxygen redox. Instead, the 530.4 eV peak for these three systems is attributed to transition metal reduction and electrolyte decomposition in the near-surface region. Claims of oxygen redox relying on photoelectron spectroscopy must explicitly account for the surface sensitivity of this technique and the extent of the cathode degradation layer.

Journal
The Journal of Physical Chemistry Letters
Volume
11
Year of Publication
2020
Issue
6
Pagination
2106 - 2112
ISSN Number
1948-7185
Short Title
J. Phys. Chem. Lett.
Refereed Designation
Refereed
Organizations
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