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

Zachary W Lebens-Higgins; Hyeseung Chung; Mateusz J Zuba; Jatinkumar Rana; Yixuan Li; Nicholas V Faenza; Nathalie Pereira; Bryan D McCloskey; Fanny Rodolakis; Wanli Yang; M Stanley Whittingham; Glenn G Amatucci; Ying Shirley Meng; Tien-Lin Lee; Louis F J Piper

doi:10.1021/acs.jpclett.0c00229

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

J Phys Chem Lett. 2020 Mar 19;11(6):2106-2112. doi: 10.1021/acs.jpclett.0c00229. Epub 2020 Mar 4.

Authors

Zachary W Lebens-Higgins¹, Hyeseung Chung², Mateusz J Zuba³, Jatinkumar Rana³, Yixuan Li², Nicholas V Faenza⁴, Nathalie Pereira⁴, Bryan D McCloskey^{5

6}, Fanny Rodolakis⁷, Wanli Yang⁸, M Stanley Whittingham³, Glenn G Amatucci⁴, Ying Shirley Meng², Tien-Lin Lee⁹, Louis F J Piper^{1

3}

Affiliations

¹ Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, New York 13902, United States.
² Department of NanoEngineering, University of California San Diego, La Jolla, California 92093, United States.
³ Materials Science & Engineering, Binghamton University, Binghamton, New York 13902, United States.
⁴ Energy Storage Research Group, Department of Materials Science and Engineering, Rutgers University, North Brunswick, New Jersey 08902, United States.
⁵ Energy Storage and Distributed Resources Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
⁶ Department of Chemical and Biomolecular Engineering, University of California Berkeley, Berkeley, California 94720, United States.
⁷ Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States.
⁸ Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
⁹ Diamond Light Source Ltd., Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, U.K.

PMID: 32101006
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.