Refinement of the structure of Na0.74CoO2 using neutron powder diffraction

Balsys, R.J.

doi:10.1016/s0167-2738(96)00557-7

Cited by 111 publications

(85 citation statements)

References 7 publications

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“…The LiMO 2 layered oxides are O3-type structures, where the oxygen planes have an ABCABC stacking sequence, while the Na equivalents typically exist in several polytypes (e.g., Na x CoO 2 exists in three polytypes, O3, P2 and P3, depending on the amount of Na intercalated). 16,19,21,[33][34][35][36][37] These polytypes differ in the stacking of the oxygen layers (ABCABC for O3, ABBA for P2 and ABBCCA for P3), resulting in different intercalation sites for the alkali cation. After complete delithiation, the MO 2 layers are weakly bound by van der Waals forces.…”

Section: Structure Selectionmentioning

confidence: 99%

Voltage, stability and diffusion barrier differences between sodium-ion and lithium-ion intercalation materials

Ong

Chevrier

Hautier

et al. 2011

Energy Environ. Sci.

1,298

1,046

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To evaluate the potential of Na-ion batteries, we contrast in this work the difference between Na-ion and Li-ion based intercalation chemistries in terms of three key battery properties -voltage, phase stability and diffusion barriers. The compounds investigated comprise the layered AMO 2 and AMS 2 structures, the olivine and maricite AMPO 4 structures, and the NA-SICON A 3 V 2 (PO 4 ) 3 structures. The calculated Na voltages for the compounds investigated are 0.18-0.57 V lower than that of the corresponding Li voltages, in agreement with previous experimental data. We believe the observed lower voltages for Na compounds are predominantly a cathodic effect related to the much smaller energy gain from inserting Na into the host structure compared to inserting Li. We also found a relatively strong dependence of battery properties with structural features. In general, the difference between the Na and Li voltage of the same compound, ∆V Na-Li , is less negative for the maricite structures preferred by Na, and * To whom correspondence should be addressed 1 more negative for the olivine structures preferred by Li. The layered compounds have the most negative ∆V Na-Li . In terms of phase stability, we found that open structures, such as the layered and NASICON structures that are better able to accommodate the larger Na + ion generally have both Na and Li versions of the same compound. For the close-packed AMPO 4 structures, our results show that Na generally prefers the maricite structure, while Li prefers the olivine structure, in agreement with previous experimental work. We also found surprising evidence that the barriers for Na + migration can potentially be lower than that for Li + migration in the layered structures. Overall, our findings indicate that Na-ion systems can be competitive with Li-ion systems.

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Section: Structure Selectionmentioning

confidence: 99%

Voltage, stability and diffusion barrier differences between sodium-ion and lithium-ion intercalation materials

Ong

Chevrier

Hautier

et al. 2011

Energy Environ. Sci.

1,298

1,046

View full text Add to dashboard Cite

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“…[9,10,11,12,13,14,15,16,17,18] The Co ions are enclosed in edge sharing O-octahedra which in turn are separated by insulating Na layers. [19,20] The latter mainly act as a charge reservoir. Depending on x, the Na ions tend to order on particular sublattices at room temperature and below.…”

Section: Introductionmentioning

confidence: 99%

Localized versus itinerant magnetic moments inNa0.7CoO2

et al. 2006

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Based on experimental 59 Co-NMR data in the temperature range between 0.1 and 300 K, we address the problem of the character of the Co 3d-electron based magnetism in Na0.7CoO2. Temperature dependent 59 Co-NMR spectra reveal different Co environments below 300 K and their differentiation increases with decreasing temperature. We show that the 23 Na-and 59 Co-NMR data may consistently be interpreted by assuming that below room temperature the Co 3d-electrons are itinerant. Their magnetic interaction appears to favor an antiferromagnetic coupling, and we identify a substantial orbital contribution χ orb to the d−electron susceptibility. At low temperatures χ orb seems to acquire some temperature dependence, suggesting an increasing influence of spin-orbit coupling. The temperature dependence of the spin-lattice relaxation rate T −1 1 (T ) confirms significant variations in the dynamics of this electronic subsystem between 200 and 300K, as previously suggested. Below 200 K, Na0.7CoO2 may be viewed as a weak antiferromagnet with TN below 1 K but this scenario still leaves a number of open questions.

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“…7) 7 with a hexagonal layered structure (space group P6 3 /mmc), also denoted as P2-type by Delmas et al 8 Na 0.7 CoO 2 was able to sustain sodium insertion/extraction at a potential range of 2-3.8 V. 9 However, this material exhibited complex phase transformation in this window, possibly due to the interplay of Na + /vacancy ordering at Na sites and charge ordering at Co sites. 10,11 The application of two or more transition metals with different valences is likely to interfere with vacancy/charge ordering and lead a more solid-solution behavior.…”

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confidence: 99%