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Covalency does not suppress O2 formation in 4d and 5d Li-rich O-redox cathodes

DOI: 10.1038/s41467-021-23154-4 DOI Help

Authors: Robert A. House (University of Oxford; The Henry Royce Institute; The Faraday Institution) , John-Joseph Marie (University of Oxford; The Henry Royce Institute; The Faraday Institution) , Joohyuk Park (University of Oxford) , Gregory J. Rees (University of Oxford; The Henry Royce Institute; The Faraday Institution) , Stefano Agrestini (Diamond Light Source) , Abhishek Nag (Diamond Light Source) , Mirian Garcia-Fernandez (Diamond Light Source) , Ke-Jin Zhou (Diamond Light Source) , Peter G. Bruce (University of Oxford; The Henry Royce Institute; The Faraday Institution)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Communications , VOL 12

State: Published (Approved)
Published: May 2021
Diamond Proposal Number(s): 25589

Open Access Open Access

Abstract: Layered Li-rich transition metal oxides undergo O-redox, involving the oxidation of the O2− ions charge compensated by extraction of Li+ ions. Recent results have shown that for 3d transition metal oxides the oxidized O2− forms molecular O2 trapped in the bulk particles. Other forms of oxidised O2− such as O22− or (O–O)n− with long bonds have been proposed, based especially on work on 4 and 5d transition metal oxides, where TM–O bonding is more covalent. Here, we show, using high resolution RIXS that molecular O2 is formed in the bulk particles on O2‒ oxidation in the archetypal Li-rich ruthenates and iridate compounds, Li2RuO3, Li2Ru0.5Sn0.5O3 and Li2Ir0.5Sn0.5O3. The results indicate that O-redox occurs across 3, 4, and 5d transition metal oxides, forming O2, i.e. the greater covalency of the 4d and 5d compounds still favours O2. RIXS and XAS data for Li2IrO3 are consistent with a charge compensation mechanism associated primarily with Ir redox up to and beyond the 5+ oxidation state, with no evidence of O–O dimerization.

Journal Keywords: Batteries; Electronic materials

Diamond Keywords: Batteries; Lithium-ion

Subject Areas: Materials, Chemistry, Energy

Instruments: I21-Resonant Inelastic X-ray Scattering (RIXS)

Added On: 24/05/2021 13:58


Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Scattering Spectroscopy Resonant Inelastic X-ray Scattering (RIXS) X-ray Absorption Spectroscopy (XAS)