Delocalized electron holes on oxygen in a battery cathode

Robert A. House, Gregory J. Rees, Kit McColl, John Joseph Marie, Mirian Garcia-Fernandez, Abhishek Nag, Ke Jin Zhou, Simon Cassidy, Benjamin J. Morgan, M. Saiful Islam, Peter G. Bruce

Research output: Contribution to journalArticlepeer-review

22 Citations (SciVal)
223 Downloads (Pure)

Abstract

Oxide ions in transition metal oxide cathodes can store charge at high voltage offering a route towards higher energy density batteries. However, upon charging these cathodes, the oxidized oxide ions condense to form molecular O2 trapped in the material. Consequently, the discharge voltage is much lower than charge, leading to undesirable voltage hysteresis. Here we capture the nature of the electron holes on O2− before O2 formation by exploiting the suppressed transition metal rearrangement in ribbon-ordered Na0.6[Li0.2Mn0.8]O2. We show that the electron holes formed are delocalized across the oxide ions coordinated to two Mn (O–Mn2) arranged in ribbons in the transition metal layers. Furthermore, we track these delocalized hole states as they gradually localize in the structure in the form of trapped molecular O2 over a period of days. Establishing the nature of hole states on oxide ions is important if truly reversible high-voltage O-redox cathodes are to be realized.

Original languageEnglish
Pages (from-to)351-360
Number of pages10
JournalNature Energy
Volume8
Issue number4
DOIs
Publication statusPublished - 16 Feb 2023

Bibliographical note

Funding Information:
We are indebted to the Engineering and Physical Sciences Research Council (EPSRC), the Henry Royce Institute for Advanced Materials (EP/R00661X/1, EP/S019367/1, EP/R010145/1, EP/L019469/1) and the Faraday Institution (FIRG007, FIRG008, FIRG016) for financial support. We thank the HEC Materials Chemistry Consortium (EP/R029431/1) for supercomputer facilities. We acknowledge Diamond Light Source for time on I21 under proposal MM25589-1. This project was supported by the Royal Academy of Engineering under the Research Fellowship scheme. B.J.M. acknowledges support from the Royal Society (UF130329 and URF\R\191006).

Data availability
All the data generated or analysed during this study are included in the published article and its Supplementary Information. Source data are provided with this paper.

For the purpose of open access, the author has applied a CC BY public copyright licence to any author accepted manuscript (AAM) version arising from this submission.

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Energy Engineering and Power Technology

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