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Intermediate honeycomb ordering to trigger oxygen redox chemistry in layered battery electrode.

Mortemard de Boisse B, Liu G, Ma J, Nishimura S, Chung SC, Kiuchi H, Harada Y, Kikkawa J, Kobayashi Y, Okubo M, Yamada A - Nat Commun (2016)

Bottom Line: Here using two polymorphs of Na2RuO3, we demonstrate the critical role of honeycomb-type cation ordering in Na2MO3.Ordered Na2RuO3 with honeycomb-ordered [Na(1/3)Ru(2/3)]O2 slabs delivers a capacity of 180 mAh g(-1) (1.3-electron reaction), whereas disordered Na2RuO3 only delivers 135 mAh g(-1) (1.0-electron reaction).We clarify that the large extra capacity of ordered Na2RuO3 is enabled by a spontaneously ordered intermediate Na1RuO3 phase with ilmenite O1 structure, which induces frontier orbital reorganization to trigger the oxygen redox reaction, unveiling a general requisite for the stable oxygen redox reaction in high-capacity Na2MO3 cathodes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan.

ABSTRACT
Sodium-ion batteries are attractive energy storage media owing to the abundance of sodium, but the low capacities of available cathode materials make them impractical. Sodium-excess metal oxides Na2MO3 (M: transition metal) are appealing cathode materials that may realize large capacities through additional oxygen redox reaction. However, the general strategies for enhancing the capacity of Na2MO3 are poorly established. Here using two polymorphs of Na2RuO3, we demonstrate the critical role of honeycomb-type cation ordering in Na2MO3. Ordered Na2RuO3 with honeycomb-ordered [Na(1/3)Ru(2/3)]O2 slabs delivers a capacity of 180 mAh g(-1) (1.3-electron reaction), whereas disordered Na2RuO3 only delivers 135 mAh g(-1) (1.0-electron reaction). We clarify that the large extra capacity of ordered Na2RuO3 is enabled by a spontaneously ordered intermediate Na1RuO3 phase with ilmenite O1 structure, which induces frontier orbital reorganization to trigger the oxygen redox reaction, unveiling a general requisite for the stable oxygen redox reaction in high-capacity Na2MO3 cathodes.

No MeSH data available.


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Structural changes of disordered and ordered Na2RuO3 during charge.(a) Interlayer distance of the different phases involved on desodiation as a function of x in disordered and ordered NaxRuO3. (b) Crystal structure of ilmenite-type Na1RuO3. All Na ions displace cooperatively towards Na vacancies in the honeycomb planes. (c) Observed and calculated (Rietveld method) synchrotron X-ray diffraction patterns for ordered Na1RuO3. Red crosses: experimental, black line: calculated, blue line: difference and green bars: Bragg positions. The inset shows the selected area electron diffraction (SAED) pattern for ilmenite-type Na1RuO3. Scale bar, 10 nm−1 (d) Ex situ XRD patterns showing the evolution of the superstructure peaks for ordered NaxRuO3 on charge.
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f4: Structural changes of disordered and ordered Na2RuO3 during charge.(a) Interlayer distance of the different phases involved on desodiation as a function of x in disordered and ordered NaxRuO3. (b) Crystal structure of ilmenite-type Na1RuO3. All Na ions displace cooperatively towards Na vacancies in the honeycomb planes. (c) Observed and calculated (Rietveld method) synchrotron X-ray diffraction patterns for ordered Na1RuO3. Red crosses: experimental, black line: calculated, blue line: difference and green bars: Bragg positions. The inset shows the selected area electron diffraction (SAED) pattern for ilmenite-type Na1RuO3. Scale bar, 10 nm−1 (d) Ex situ XRD patterns showing the evolution of the superstructure peaks for ordered NaxRuO3 on charge.

Mentions: To clarify the reaction mechanisms in Na2RuO3, we studied the structural changes of D-Na2RuO3 and O-Na2RuO3 during cycling (Fig. 4a–d). As reported previously19 and further supported by ex situ XRD patterns (Supplementary Fig. 2), D-NaxRuO3 undergoes a structural change from O3 to P3 (with Na in prismatic sites owing to the ABBCCA oxide-ion stacking) on charging23. This O3→P3 transition is commonly observed in O3-NaMO2 materials through gliding of the [Na1/3Ru2/3]O2 slabs from ABCABC (O3) to ABBCCA (P3) stacking925. The synchrotron XRD pattern of the charged state (D-Na1RuO3; Supplementary Fig. 3 and Supplementary Table 2) is fully fitted by the Rietveld refinement assuming a P3 structure (Rm space group, a=2.927(2) Å and c=16.774(12) Å), in which Na ions in the Na layer are located in prismatic sites (inset in Fig. 3a). The interlayer distance is significantly increased from 5.323(1) Å (x=2) to 5.591(4) Å (x=1) because of the high aspect ratio of the prismatic Na sites in the P3 structure (Fig. 4a).


Intermediate honeycomb ordering to trigger oxygen redox chemistry in layered battery electrode.

Mortemard de Boisse B, Liu G, Ma J, Nishimura S, Chung SC, Kiuchi H, Harada Y, Kikkawa J, Kobayashi Y, Okubo M, Yamada A - Nat Commun (2016)

Structural changes of disordered and ordered Na2RuO3 during charge.(a) Interlayer distance of the different phases involved on desodiation as a function of x in disordered and ordered NaxRuO3. (b) Crystal structure of ilmenite-type Na1RuO3. All Na ions displace cooperatively towards Na vacancies in the honeycomb planes. (c) Observed and calculated (Rietveld method) synchrotron X-ray diffraction patterns for ordered Na1RuO3. Red crosses: experimental, black line: calculated, blue line: difference and green bars: Bragg positions. The inset shows the selected area electron diffraction (SAED) pattern for ilmenite-type Na1RuO3. Scale bar, 10 nm−1 (d) Ex situ XRD patterns showing the evolution of the superstructure peaks for ordered NaxRuO3 on charge.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4837481&req=5

f4: Structural changes of disordered and ordered Na2RuO3 during charge.(a) Interlayer distance of the different phases involved on desodiation as a function of x in disordered and ordered NaxRuO3. (b) Crystal structure of ilmenite-type Na1RuO3. All Na ions displace cooperatively towards Na vacancies in the honeycomb planes. (c) Observed and calculated (Rietveld method) synchrotron X-ray diffraction patterns for ordered Na1RuO3. Red crosses: experimental, black line: calculated, blue line: difference and green bars: Bragg positions. The inset shows the selected area electron diffraction (SAED) pattern for ilmenite-type Na1RuO3. Scale bar, 10 nm−1 (d) Ex situ XRD patterns showing the evolution of the superstructure peaks for ordered NaxRuO3 on charge.
Mentions: To clarify the reaction mechanisms in Na2RuO3, we studied the structural changes of D-Na2RuO3 and O-Na2RuO3 during cycling (Fig. 4a–d). As reported previously19 and further supported by ex situ XRD patterns (Supplementary Fig. 2), D-NaxRuO3 undergoes a structural change from O3 to P3 (with Na in prismatic sites owing to the ABBCCA oxide-ion stacking) on charging23. This O3→P3 transition is commonly observed in O3-NaMO2 materials through gliding of the [Na1/3Ru2/3]O2 slabs from ABCABC (O3) to ABBCCA (P3) stacking925. The synchrotron XRD pattern of the charged state (D-Na1RuO3; Supplementary Fig. 3 and Supplementary Table 2) is fully fitted by the Rietveld refinement assuming a P3 structure (Rm space group, a=2.927(2) Å and c=16.774(12) Å), in which Na ions in the Na layer are located in prismatic sites (inset in Fig. 3a). The interlayer distance is significantly increased from 5.323(1) Å (x=2) to 5.591(4) Å (x=1) because of the high aspect ratio of the prismatic Na sites in the P3 structure (Fig. 4a).

Bottom Line: Here using two polymorphs of Na2RuO3, we demonstrate the critical role of honeycomb-type cation ordering in Na2MO3.Ordered Na2RuO3 with honeycomb-ordered [Na(1/3)Ru(2/3)]O2 slabs delivers a capacity of 180 mAh g(-1) (1.3-electron reaction), whereas disordered Na2RuO3 only delivers 135 mAh g(-1) (1.0-electron reaction).We clarify that the large extra capacity of ordered Na2RuO3 is enabled by a spontaneously ordered intermediate Na1RuO3 phase with ilmenite O1 structure, which induces frontier orbital reorganization to trigger the oxygen redox reaction, unveiling a general requisite for the stable oxygen redox reaction in high-capacity Na2MO3 cathodes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical System Engineering, School of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan.

ABSTRACT
Sodium-ion batteries are attractive energy storage media owing to the abundance of sodium, but the low capacities of available cathode materials make them impractical. Sodium-excess metal oxides Na2MO3 (M: transition metal) are appealing cathode materials that may realize large capacities through additional oxygen redox reaction. However, the general strategies for enhancing the capacity of Na2MO3 are poorly established. Here using two polymorphs of Na2RuO3, we demonstrate the critical role of honeycomb-type cation ordering in Na2MO3. Ordered Na2RuO3 with honeycomb-ordered [Na(1/3)Ru(2/3)]O2 slabs delivers a capacity of 180 mAh g(-1) (1.3-electron reaction), whereas disordered Na2RuO3 only delivers 135 mAh g(-1) (1.0-electron reaction). We clarify that the large extra capacity of ordered Na2RuO3 is enabled by a spontaneously ordered intermediate Na1RuO3 phase with ilmenite O1 structure, which induces frontier orbital reorganization to trigger the oxygen redox reaction, unveiling a general requisite for the stable oxygen redox reaction in high-capacity Na2MO3 cathodes.

No MeSH data available.


Related in: MedlinePlus