Revealing Electronic Signatures of Lattice Oxygen Redox in Lithium Ruthenates and Implications for High-Energy Li-Ion Battery Material Designs
Name
nihms-1548502.pdf
Description
Accepted version
Size
1.67 MB
Format
Adobe PDF
Checksum (MD5)
479d9a0800db5c283f92eaba527cfacc
Author(s)
Yu, Yang
Karayaylali, Pinar
Nowak, Stanisław H.
Giordano, Livia
Gauthier, Magali Aurelie Marie
Hong, Wesley
Kou, Ronghui
Li, Qinghao
Vinson, John
Kroll, Thomas
Date Issued
September 2019
Journal
Chemistry of Materials
Publisher
American Chemical Society (ACS)
Citation
Yu, Yang et al. "Revealing Electronic Signatures of Lattice Oxygen Redox in Lithium Ruthenates and Implications for High-Energy Li-Ion Battery Material Designs." Chemistry of Materials 31, 19 (October 2019): 7864–7876 © 2019 American Chemical Society
Version
Author's final manuscript
Abstract
Anion redox in lithium transition-metal oxides such as Li2RuO3 and Li2MnO3 has catalyzed intensive research efforts to find transition-metal oxides with anion redox that may boost the energy density of lithium-ion batteries. The physical origin of the observed anion redox remains debatable, and more direct experimental evidence is needed. In this work, we have shown electronic signatures of oxygen-oxygen coupling, direct evidence central to lattice oxygen redox (O2-/(O2)n-), in charged Li2-xRuO3 after Ru oxidation (Ru4+/Ru5+) upon first electron removal with lithium deintercalation. Experimental Ru L3-edge high-energy-resolution fluorescence-detected X-ray absorption spectra (HERFD-XAS), supported by ab initio simulations, revealed that the increased intensity in the high-energy shoulder upon lithium deintercalation resulted from increased O-O coupling, inducing (O-O) σ*-like states with πoverlap with Ru d-manifolds, in agreement with O K-edge XAS spectra. Experimental and simulated O K-edge X-ray emission spectra further supported this observation with the broadening of the oxygen nonbonding feature upon charging, also originated from (O-O) σ∗ states. This lattice oxygen redox of Li2-xRuO3 was accompanied by a small amount of O2 evolution in the first charge from differential electrochemistry mass spectrometry but diminished in the subsequent cycles, in agreement with the more reduced states of Ru in later cycles from Ru L3-edge HERFD-XAS. These observations indicated that Ru redox contributed more to discharge capacities after the first cycle. This study has pinpointed the key spectral fingerprints related to lattice oxygen redox from a molecular level and constructed a transferrable framework to rationally interpret the spectroscopic features by combining advanced experiments and theoretical calculations to design materials for Li-ion batteries and electrocatalysis applications.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
Massachusetts Institute of Technology. Research Laboratory of Electronics
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DOI of Published Version
https://doi.org/10.1021/acs.chemmater.9b01821
