Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides

Jihyun Hong; William E Gent; Penghao Xiao; Kipil Lim; Dong-Hwa Seo; Jinpeng Wu; Peter M Csernica; Christopher J Takacs; Dennis Nordlund; Cheng-Jun Sun; Kevin H Stone; Donata Passarello; Wanli Yang; David Prendergast; Gerbrand Ceder; Michael F Toney; William C Chueh

doi:10.1038/s41563-018-0276-1

Metal-oxygen decoordination stabilizes anion redox in Li-rich oxides

Nat Mater. 2019 Mar;18(3):256-265. doi: 10.1038/s41563-018-0276-1. Epub 2019 Feb 4.

Authors

Jihyun Hong^{1

2

3

4

5}, William E Gent^{6

7}, Penghao Xiao⁸, Kipil Lim^{1

2

3

4}, Dong-Hwa Seo⁹, Jinpeng Wu^{3

7}, Peter M Csernica¹, Christopher J Takacs², Dennis Nordlund², Cheng-Jun Sun¹⁰, Kevin H Stone², Donata Passarello², Wanli Yang⁷, David Prendergast¹¹, Gerbrand Ceder^{12

13}, Michael F Toney^{14

15}, William C Chueh^{16

17

18}

Affiliations

¹ Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
² Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
³ Stanford Institute for Materials & Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
⁴ Applied Energy Division, SLAC National Accelerator Laboratory, Menlo Park, CA, USA.
⁵ Center for Energy Materials Research, Korea Institute of Science and Technology (KIST), Seoul, Republic of Korea.
⁶ Department of Chemistry, Stanford University, Stanford, CA, USA.
⁷ The Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
⁸ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
⁹ Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.
¹⁰ The Advanced Photon Source, Argonne National Laboratory, Lemont, IL, USA.
¹¹ The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
¹² Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA. gceder@berkeley.edu.
¹³ Department of Materials Science and Engineering, University of California, Berkeley, CA, USA. gceder@berkeley.edu.
¹⁴ Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA, USA. mftoney@slac.stanford.edu.
¹⁵ Applied Energy Division, SLAC National Accelerator Laboratory, Menlo Park, CA, USA. mftoney@slac.stanford.edu.
¹⁶ Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA. wchueh@stanford.edu.
¹⁷ Stanford Institute for Materials & Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA, USA. wchueh@stanford.edu.
¹⁸ Applied Energy Division, SLAC National Accelerator Laboratory, Menlo Park, CA, USA. wchueh@stanford.edu.

PMID: 30718861
DOI: 10.1038/s41563-018-0276-1

Abstract

Reversible high-voltage redox chemistry is an essential component of many electrochemical technologies, from (electro)catalysts to lithium-ion batteries. Oxygen-anion redox has garnered intense interest for such applications, particularly lithium-ion batteries, as it offers substantial redox capacity at more than 4 V versus Li/Li⁺ in a variety of oxide materials. However, oxidation of oxygen is almost universally correlated with irreversible local structural transformations, voltage hysteresis and voltage fade, which currently preclude its widespread use. By comprehensively studying the Li_2-xIr_1-ySn_yO₃ model system, which exhibits tunable oxidation state and structural evolution with y upon cycling, we reveal that this structure-redox coupling arises from the local stabilization of short approximately 1.8 Å metal-oxygen π bonds and approximately 1.4 Å O-O dimers during oxygen redox, which occurs in Li_2-xIr_1-ySn_yO₃ through ligand-to-metal charge transfer. Crucially, formation of these oxidized oxygen species necessitates the decoordination of oxygen to a single covalent bonding partner through formation of vacancies at neighbouring cation sites, driving cation disorder. These insights establish a point-defect explanation for why anion redox often occurs alongside local structural disordering and voltage hysteresis during cycling. Our findings offer an explanation for the unique electrochemical properties of lithium-rich layered oxides, with implications generally for the design of materials employing oxygen redox chemistry.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.