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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.


Related in: MedlinePlus

Calculated electronic structure of ordered Na2RuO3 upon charge.Calculated density of states (DOS) for ordered (a) O3-Na2RuO3 and (b) ilmenite-type Na1RuO3.
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f7: Calculated electronic structure of ordered Na2RuO3 upon charge.Calculated density of states (DOS) for ordered (a) O3-Na2RuO3 and (b) ilmenite-type Na1RuO3.

Mentions: The O K-edge spectrum of pristine O-Na2RuO3 (t2g4eg0) shows a large peak at 534 eV, which is ascribed to the unoccupied hybridized orbital of O 2p–Na 3p, and its peak intensity simply reflects the amount of Na in the lattice30. The calculated density of states for O-Na2RuO3 (Fig. 7a) also indicates that the O 2p–Na 3p hybridized orbital exists in this energy range. For the lower energy region that represents the redox reaction, the calculated oxygen K-edge spectrum agrees well with the spectra from 528 to 533 eV. Thus, the peaks around 529 eV and 532 eV can be ascribed to the unoccupied hybridized orbitals of O 2p–Ru t2g and O 2p–Ru eg, respectively3132. At the voltage plateau of 2.5 V, desodiation diminishes the O 2p–Na 3p signal, whereas the peak intensity of O 2p–Ru t2g (around 529 eV) increases on charging, indicating hole generation on the O 2p–Ru t2g orbital. The increase in the peak intensity around 529 eV is also in good agreement with the calculated oxygen K-edge spectrum for ilmenite-type Na1RuO3.


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)

Calculated electronic structure of ordered Na2RuO3 upon charge.Calculated density of states (DOS) for ordered (a) O3-Na2RuO3 and (b) ilmenite-type Na1RuO3.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f7: Calculated electronic structure of ordered Na2RuO3 upon charge.Calculated density of states (DOS) for ordered (a) O3-Na2RuO3 and (b) ilmenite-type Na1RuO3.
Mentions: The O K-edge spectrum of pristine O-Na2RuO3 (t2g4eg0) shows a large peak at 534 eV, which is ascribed to the unoccupied hybridized orbital of O 2p–Na 3p, and its peak intensity simply reflects the amount of Na in the lattice30. The calculated density of states for O-Na2RuO3 (Fig. 7a) also indicates that the O 2p–Na 3p hybridized orbital exists in this energy range. For the lower energy region that represents the redox reaction, the calculated oxygen K-edge spectrum agrees well with the spectra from 528 to 533 eV. Thus, the peaks around 529 eV and 532 eV can be ascribed to the unoccupied hybridized orbitals of O 2p–Ru t2g and O 2p–Ru eg, respectively3132. At the voltage plateau of 2.5 V, desodiation diminishes the O 2p–Na 3p signal, whereas the peak intensity of O 2p–Ru t2g (around 529 eV) increases on charging, indicating hole generation on the O 2p–Ru t2g orbital. The increase in the peak intensity around 529 eV is also in good agreement with the calculated oxygen K-edge spectrum for ilmenite-type Na1RuO3.

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