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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 characterization of disordered and ordered Na2RuO3.Observed and calculated (Rietveld method) synchrotron X-ray diffraction patterns for (a) disordered and (b) ordered Na2RuO3. Red crosses: experimental, black line: calculated, blue line: difference and green bars: Bragg positions. The black arrows in b indicate the superstructure peaks that were not considered for the refinement. Insets of a,b correspond to the 99Ru Mössbauer spectra recorded at 4.2 K for both pristine materials. Vertical error bars represent 1σ s.d. of counting statistics. Selected area electron diffraction (SAED) patterns in the (c) [001]hex zone axes of disordered Na2RuO3, and in the (d) [001]hex and (e) [10]hex zone axes of ordered Na2RuO3. The red circles and arrows, respectively, indicate the central and fundamental diffraction spots, which are common to disordered Na2RuO3. Un-marked diffraction spots in between correspond to superstructure peaks. Scale bars, 10 nm−1.
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f2: Structural characterization of disordered and ordered Na2RuO3.Observed and calculated (Rietveld method) synchrotron X-ray diffraction patterns for (a) disordered and (b) ordered Na2RuO3. Red crosses: experimental, black line: calculated, blue line: difference and green bars: Bragg positions. The black arrows in b indicate the superstructure peaks that were not considered for the refinement. Insets of a,b correspond to the 99Ru Mössbauer spectra recorded at 4.2 K for both pristine materials. Vertical error bars represent 1σ s.d. of counting statistics. Selected area electron diffraction (SAED) patterns in the (c) [001]hex zone axes of disordered Na2RuO3, and in the (d) [001]hex and (e) [10]hex zone axes of ordered Na2RuO3. The red circles and arrows, respectively, indicate the central and fundamental diffraction spots, which are common to disordered Na2RuO3. Un-marked diffraction spots in between correspond to superstructure peaks. Scale bars, 10 nm−1.

Mentions: Ordered Na2RuO3 (hereafter denoted O-Na2RuO3) was synthesized by a thermal decomposition method, in which Na2RuO4 was annealed at 850 °C for 48 h under an Ar atmosphere21. Disordered Na2RuO3 (hereafter denoted D-Na2RuO3) was synthesized for comparison according to our previously reported procedure19. The 99Ru Mössbauer spectra of both compounds (insets in Fig. 2a,b) show a singlet absorption peak with an isomer shift around −0.3 mm s−1, which is a typical value for Ru4+ (for example, −0.25 mm s−1 for Y2Ru2O7 and −0.33 mm s−1 for SrRuO3)22, suggesting successful formation of stoichiometric Na2RuO3 compositions from both syntheses. The synchrotron X-ray diffraction (XRD) pattern of D-Na2RuO3 (Fig. 2a) is fully indexed to the O3 structure (Rm space group, a=3.0969(3) Å and c=15.970(2) Å); all diffraction peaks are well-fitted by Rietveld refinement with a structural model in which Na and Ru are randomly distributed in the [Na1/3Ru2/3]O2 slabs (Fig. 1 and Supplementary Table 1). Na in the Na layer occupies octahedral sites and the oxide ions are stacked in an ABCABC arrangement (O3 structure)23. The selected area electron diffraction (SAED) pattern along the [001]hex zone axis (Fig. 2c) shows diffraction spots fully indexed by the Rm model with disordered [Na1/3Ru2/3]O2 slabs.


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 characterization of disordered and ordered Na2RuO3.Observed and calculated (Rietveld method) synchrotron X-ray diffraction patterns for (a) disordered and (b) ordered Na2RuO3. Red crosses: experimental, black line: calculated, blue line: difference and green bars: Bragg positions. The black arrows in b indicate the superstructure peaks that were not considered for the refinement. Insets of a,b correspond to the 99Ru Mössbauer spectra recorded at 4.2 K for both pristine materials. Vertical error bars represent 1σ s.d. of counting statistics. Selected area electron diffraction (SAED) patterns in the (c) [001]hex zone axes of disordered Na2RuO3, and in the (d) [001]hex and (e) [10]hex zone axes of ordered Na2RuO3. The red circles and arrows, respectively, indicate the central and fundamental diffraction spots, which are common to disordered Na2RuO3. Un-marked diffraction spots in between correspond to superstructure peaks. Scale bars, 10 nm−1.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f2: Structural characterization of disordered and ordered Na2RuO3.Observed and calculated (Rietveld method) synchrotron X-ray diffraction patterns for (a) disordered and (b) ordered Na2RuO3. Red crosses: experimental, black line: calculated, blue line: difference and green bars: Bragg positions. The black arrows in b indicate the superstructure peaks that were not considered for the refinement. Insets of a,b correspond to the 99Ru Mössbauer spectra recorded at 4.2 K for both pristine materials. Vertical error bars represent 1σ s.d. of counting statistics. Selected area electron diffraction (SAED) patterns in the (c) [001]hex zone axes of disordered Na2RuO3, and in the (d) [001]hex and (e) [10]hex zone axes of ordered Na2RuO3. The red circles and arrows, respectively, indicate the central and fundamental diffraction spots, which are common to disordered Na2RuO3. Un-marked diffraction spots in between correspond to superstructure peaks. Scale bars, 10 nm−1.
Mentions: Ordered Na2RuO3 (hereafter denoted O-Na2RuO3) was synthesized by a thermal decomposition method, in which Na2RuO4 was annealed at 850 °C for 48 h under an Ar atmosphere21. Disordered Na2RuO3 (hereafter denoted D-Na2RuO3) was synthesized for comparison according to our previously reported procedure19. The 99Ru Mössbauer spectra of both compounds (insets in Fig. 2a,b) show a singlet absorption peak with an isomer shift around −0.3 mm s−1, which is a typical value for Ru4+ (for example, −0.25 mm s−1 for Y2Ru2O7 and −0.33 mm s−1 for SrRuO3)22, suggesting successful formation of stoichiometric Na2RuO3 compositions from both syntheses. The synchrotron X-ray diffraction (XRD) pattern of D-Na2RuO3 (Fig. 2a) is fully indexed to the O3 structure (Rm space group, a=3.0969(3) Å and c=15.970(2) Å); all diffraction peaks are well-fitted by Rietveld refinement with a structural model in which Na and Ru are randomly distributed in the [Na1/3Ru2/3]O2 slabs (Fig. 1 and Supplementary Table 1). Na in the Na layer occupies octahedral sites and the oxide ions are stacked in an ABCABC arrangement (O3 structure)23. The selected area electron diffraction (SAED) pattern along the [001]hex zone axis (Fig. 2c) shows diffraction spots fully indexed by the Rm model with disordered [Na1/3Ru2/3]O2 slabs.

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