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Title
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Layered-to-tunnel structure transformation and oxygen redox chemistry in upon Li-extraction and insertion
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Author
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Abstract
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| Layered Li(M,Li)O2 (where M is a transition metal) ordered rock-salt-type structures are used in advanced metal-ion batteries as one of the best hosts for the reversible intercalation of Li ions. Besides the conventional redox reaction involving oxidation/ reduction of the M cation upon Li extraction/insertion, creating oxygen-located holes because of the partial oxygen oxidation increases capacity while maintaining the oxidized oxygen species in the lattice through high covalency of the M−O bonding. Typical degradation mechanism of the Li(M,Li)O2 electrodes involves partially irreversible M cation migration toward the Li positions, resulting in gradual capacity/voltage fade. Here, using LiRhO2 as a model system (isostructural and isoelectronic to LiCoO2), for the first time, we demonstrate an intimate coupling between the oxygen redox and M cation migration. A formation of the oxidized oxygen species upon electrochemical Li extraction coincides with transformation of the layered Li1−xRhO2 structure into the γ-MnO2-type rutile− ramsdellite intergrowth LiyRh3O6 structure with rutile-like [1 × 1] channels along with bigger ramsdellite-like [2 × 1] tunnels through massive and concerted Rh migration toward the empty positions in the Li layers. The oxidized oxygen dimers with the O−O distances as short as 2.26 Å are stabilized in this structure via the local Rh−O configuration reminiscent to that in the μ- peroxo-μ-hydroxo Rh complexes. The LiyRh3O6 structure is remarkably stable upon electrochemical cycling illustrating that proper structural implementation of the oxidized oxygen species can open a pathway toward deliberate employment of the anion redox chemistry in high-capacity/high-voltage positive electrodes for metal-ion batteries |
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Language
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English
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Source (journal)
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Inorganic chemistry / American Chemical Society. - Easton, Pa
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Publication
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Easton, Pa
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2016
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ISSN
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0020-1669
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DOI
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10.1021/ACS.INORGCHEM.6B01008
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Volume/pages
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55
:14
(2016)
, p. 7079-7089
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ISI
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000380181400035
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Full text (Publisher's DOI)
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Full text (open access)
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Full text (publisher's version - intranet only)
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