Transition metal migration and O2 formation underpin voltage hysteresis in oxygen-redox disordered rocksalt cathodes

DOI: 10.1038/s41467-022-32983-w

Authors: Kit Mccoll (University of Bath; The Faraday Institution) , Robert A. House (The Faraday Institution; University of Oxford) , Gregory J. Rees (The Faraday Institution; University of Oxford) , Alexander G. Squires (University of Bath) , Samuel W. Coles (University of Bath; The Faraday Institution) , Peter G. Bruce (The Faraday Institution; University of Oxford) , Benjamin J. Morgan (University of Bath; The Faraday Institution) , M. Saiful Islam (University of Bath; The Faraday Institution)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Communications , VOL 13

State: Published (Approved)
Published: September 2022
Diamond Proposal Number(s): 29028

Abstract: Lithium-rich disordered rocksalt cathodes display high capacities arising from redox chemistry on both transition-metal ions (TM-redox) and oxygen ions (O-redox), making them promising candidates for next-generation lithium-ion batteries. However, the atomic-scale mechanisms governing O-redox behaviour in disordered structures are not fully understood. Here we show that, at high states of charge in the disordered rocksalt Li2MnO2F, transition metal migration is necessary for the formation of molecular O2 trapped in the bulk. Density functional theory calculations reveal that O2 is thermodynamically favoured over other oxidised O species, which is confirmed by resonant inelastic X-ray scattering data showing only O2 forms. When O-redox involves irreversible Mn migration, this mechanism results in a path-dependent voltage hysteresis between charge and discharge, commensurate with the hysteresis observed electrochemically. The implications are that irreversible transition metal migration should be suppressed to reduce the voltage hysteresis that afflicts O-redox disordered rocksalt cathodes.

Journal Keywords: Atomistic models; Batteries

Diamond Keywords: Batteries; Lithium-ion; Electric Vehicles

Subject Areas: Materials, Chemistry, Energy


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

Added On: 12/09/2022 11:36

Documents:
s41467-022-32983-w.pdf

Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Scattering Resonant Inelastic X-ray Scattering (RIXS)