Importance of superstructure in stabilizing oxygen redox in P3-Na0.67Li0.2Mn0.8O2

DOI: 10.1002/aenm.202102325

Authors: Eun Jeong Kim (University of St Andrews; The Faraday Institution) , Philip A. Maughan (University of St Andrews; The Faraday Institution) , Euan N. Bassey (University of Cambridge) , Raphaële J. Clément (University of California, Santa Barbara) , Le Anh Ma (Uppsala University) , Laurent C. Duda (Uppsala University) , Divya Sehrawat (UNSW Australia) , Reza Younesi (Uppsala University) , Neeraj Sharma (UNSW Australia) , Clare P. Grey (The Faraday Institution; ALISTORE-ERI; University of Cambridge) , Robert Armstrong (University of St Andrews; The Faraday Institution; ALISTORE-ERI)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Energy Materials

State: Published (Approved)
Published: December 2021
Diamond Proposal Number(s): 26699

Abstract: Activation of oxygen redox represents a promising strategy to enhance the energy density of positive electrode materials in both lithium and sodium-ion batteries. However, the large voltage hysteresis associated with oxidation of oxygen anions during the first charge represents a significant challenge. Here, P3-type Na0.67Li0.2Mn0.8O2 is reinvestigated and a ribbon superlattice is identified for the first time in P3-type materials. The ribbon superstructure is maintained over cycling with very minor unit cell volume changes in the bulk while Li ions migrate reversibly between the transition metal and Na layers at the atomic scale. In addition, a range of spectroscopic techniques reveal that a strongly hybridized Mn 3d–O 2p favors ligand-to-metal charge transfer, also described as a reductive coupling mechanism, to stabilize reversible oxygen redox. By preparing materials under three different synthetic conditions, the degree of ordering between Li and Mn is varied. The sample with the maximum cation ordering delivers the largest capacity regardless of the voltage windows applied. These findings highlight the importance of cationic ordering in the transition metal layers, which can be tuned by synthetic control to enhance anionic redox and hence energy density in rechargeable batteries.

Journal Keywords: layered structures; oxygen redox; P3 structure; sodium-ion batteries; superstructures

Diamond Keywords: Batteries; Sodium-ion

Subject Areas: Materials, Chemistry, Energy


Instruments: I11-High Resolution Powder Diffraction

Other Facilities: BL27SU at Spring; Powder Diffraction beamline at Australian Synchrotron

Added On: 13/12/2021 09:17

Documents:
aenm.202102325.pdf

Discipline Tags:

Energy Storage Energy Physical Chemistry Energy Materials Chemistry Materials Science

Technical Tags:

Diffraction X-ray Powder Diffraction