Voltage hysteresis loop as a fingerprint of slow kinetics Co2+-to-Co3+ transition in layered NaxCox/2Ti1−x/2O2 cathodes for sodium batteries

dc.bibliographicCitation.date2023
dc.bibliographicCitation.firstPage187
dc.bibliographicCitation.issue1
dc.bibliographicCitation.lastPage204
dc.bibliographicCitation.volume11
dc.contributor.authorMikhailova, Daria
dc.contributor.authorGorbunov, Mikhail V.
dc.contributor.authorAn Nguyen, Hoang Bao
dc.contributor.authorPohle, Björn
dc.contributor.authorMaletti, Sebastian
dc.contributor.authorHeubner, Christian
dc.date.accessioned2023-01-31T08:27:30Z
dc.date.available2023-01-31T08:27:30Z
dc.date.issued2022
dc.description.abstractSodium transition metal oxides are one of the most promising cathode materials for future sodium ion batteries. Chemical flexibility of layered Na-oxides including cobalt enables its partial substitution by other redox-active or non-active metals, often leading to structural stabilization. Sharing the same structural positions with other transition metals in layered oxides, Co can be double- or triple-charged, and as Co3+ can adopt a low-spin (LS), intermediate-spin (IS), high-spin (HS) state, or a combination of them. Using Ti4+ in the structure together with Co2+ results in a reduced number of phase transformations compared to Ti-free compositions. However, a large potential hysteresis of about 1.5-2.5 V between battery charge and discharge is observed, pointing a first-order cooperative phase transition. Based on several examples, we found that Na extraction from NaxCox/2Ti1−x/2O2 materials with high-spin HS-Co2+, crystallizing in the P2 or O3 structure, mostly results in valence and spin-state transition of Co, leading to the formation of a second phase with a low-spin LS-Co3+, and a much smaller unit cell volume. We elucidated a kinetic origin of the potential hysteresis, which can be minimized by increasing temperature or reduction of the current density during battery cycling with P2- and O3-Na0.67Co0.33Ti0.67O2 materials. The slow kinetics of the structural phase transition, especially upon Na-insertion, hampers the application of classical methods of electrochemical thermodynamics, such as determining the entropic potential dE/dT. We showed that the entropic potential depends only on the Na-content in NaxCo0.33Ti0.67O2 during battery charge or discharge, what additionally confirms a kinetic nature of the potential hysteresis.eng
dc.description.versionpublishedVersioneng
dc.identifier.urihttps://oa.tib.eu/renate/handle/123456789/11162
dc.identifier.urihttp://dx.doi.org/10.34657/10188
dc.language.isoeng
dc.publisherLondon [u.a.] : RSC
dc.relation.doihttps://doi.org/10.1039/d2ta07972k
dc.relation.essn2050-7496
dc.relation.ispartofseriesJournal of materials chemistry : A, Materials for energy and sustainability 11 (2023), Nr. 1
dc.relation.issn2050-7488
dc.rights.licenseCC BY 3.0 Unported
dc.rights.urihttps://creativecommons.org/licenses/by/3.0
dc.subjectActive metalseng
dc.subjectCathodes materialeng
dc.subjectChemical flexibilityeng
dc.subjectHigh spinseng
dc.subjectPartial substitutioneng
dc.subjectRedox-activeeng
dc.subjectSodium batteryeng
dc.subjectSodium ion batterieseng
dc.subjectTransition-metal oxideseng
dc.subjectVoltage hysteresiseng
dc.subject.ddc540
dc.subject.ddc530
dc.titleVoltage hysteresis loop as a fingerprint of slow kinetics Co2+-to-Co3+ transition in layered NaxCox/2Ti1−x/2O2 cathodes for sodium batterieseng
dc.typearticle
dc.typeText
dcterms.bibliographicCitation.journalTitleJournal of materials chemistry : A, Materials for energy and sustainability
tib.accessRightsopenAccess
wgl.contributorIFWD
wgl.subjectChemieger
wgl.subjectPhysikger
wgl.typeZeitschriftenartikelger
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