Fig. 1 Structure of P2-NaNM and P2-NaNMT materials. (A and B) XRD and Rietveld plots of (A) P2-NaNM and (B) P2-NaNMT samples. a.u., arbitrary units. (C) P2-type crystal structure viewed along the a axis (left) and c axis (right). (D and E) (D) ABF and (E) HAADF-STEM image of P2-NaNMT at the [010] zone axis. (F and G) (F) ABF and (G) HAADF-STEM image of P2-NaNMT at the [001] zone axis. (H) Transmission electron microscopy (TEM) image and EDS maps of P2-NaNMT samples.
Fig. 2 Electrochemical performance of P2-NaNM and P2-NaNMT compounds in Na cells. (A and B) Typical charge/discharge profiles of (A) P2-NaNM and (B) P2-NaNMT between 2.5 and 4.15 V at a rate of 0.1 C. (C) Charge/discharge profiles of P2-NaNMT during the 2nd, 5th, 10th, 20th, 50th, and 100th cycles at 0.1 C, demonstrating no obvious decay in the voltage and capacity. (D) Rate performance comparison of P2-NaNM and P2-NaNMT samples at different rates. (E) Capacity retention with Coulombic efficiency of P2-NaNM and P2-NaNMT over 500 cycles cycled at 1 C.
Fig. 3 Charge compensation mechanism of P2-Na2/3−xNMT upon Na+ extraction/insertion. (A and B) Ex situ XANES spectra at the (A) Ni K-edge and (B) Mn K-edge of Na2/3−xNMT electrodes collected at different charge/discharge states. (C and D) Corresponding ex situ EXAFS spectra at the (C) Ni K-edge and (D) Mn K-edge of Na2/3−xNMT electrodes collected at different charge/discharge states. FT, Fourier transform.
Fig. 5 2D Na+/vacancy ordering-disordering transition mechanism. (A) Typical charge/discharge profiles of P2-NaNM. The two voltage plateaus indicates the rearrangement of Na+/vacancy ordering. (B) In-plane Na+/vacancy orderings of NaδNi1/3Mn2/3O2 in the triangular lattice at δ = 2/3, δ = 1/2, and δ = 1/3, respectively (empty red circles, Na+ on Nae sites; solid blue circles, Na+ on Naf sites; thick green lines, unit cell). (C) Calculated energy difference between the Nae and Naf site for P2-NaNM (purple background) and P2-NaNMT (blue background).
Supplementary Materials
Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/3/eaar6018/DC1
fig. S1. Powder XRD patterns of as-synthesized P2-NaNM and P2-NaNMT samples.
fig. S2. In situ XRD patterns of P2-NaNM and P2-NaNMT powders at different temperatures.
fig. S3. SEM images of P2-NaNM and P2-NaNMT sample.
fig. S4. TEM and HRTEM images of P2-NaNMT sample.
fig. S5. Cycling performance comparison of P2-NaNM and P2-NaNMT electrodes at 0.1 C in the voltage range of 2.5 to 4.15 V during 100 cycles.
fig. S6. SEM images of P2-NaNM and P2-NaNMT electrodes after long cycles.
fig. S7. Charge/discharge profiles of P2-NaNM and P2-NaNMT electrodes between 2.5 and 4.3 V.
fig. S8. Cycling performance comparison of P2-NaNM and P2-NaNMT electrodes at 0.1 C in the voltage range of 2.5 to 4.3 V during 100 cycles.
fig. S9. CVs of P2-NaNM and P2-NaNMT electrodes.
fig. S10. XPS spectra of P2-NaNM and P2-NaNMT powders.
fig. S11. Variation of lattice constants and unit cell volume during cycling.
fig. S12. Schematic illustration for P2-O2 phase transition.
fig. S13. In situ XRD patterns of P2-NaNM and P2-NaNMT electrodes between 2.5 and 4.3 V.
fig. S14. GITT curves and the quasi-equilibrium potential as a function of the stoichiometry.
fig. S15. Calculated Na chemical diffusion coefficients from GITT.
fig. S16. OCV decay of P2-NaNM and P2-NaNMT electrodes.
fig. S17. Nyquist plots of EIS and the fit for P2-NaNM and P2-NaNMT electrodes.
fig. S18. MSD curves for each kind of ions in P2-Na0.58NMT.
table S1. Crystallographic parameters of P2-NaNM refined by the Rietveld method.
table S2. Crystallographic parameters of P2-NaNMT refined by the Rietveld method.
table S3. Atomic distances, slab thickness, and d-spacing of the Na layer and interslab distance for as-prepared materials.
table S4. Summary of Na+ diffusion coefficients and activation energies in layered oxides.
Additional Files
Supplementary Materials
This PDF file includes:
- fig. S1. Powder XRD patterns of as-synthesized P2-NaNM and P2-NaNMT samples.
- fig. S2. In situ XRD patterns of P2-NaNM and P2-NaNMT powders at different
temperatures.
- fig. S3. SEM images of P2-NaNM and P2-NaNMT sample.
- fig. S4. TEM and HRTEM images of P2-NaNMT sample.
- fig. S5. Cycling performance comparison of P2-NaNM and P2-NaNMT
electrodes at 0.1 C in the voltage range of 2.5 to 4.15 V during 100 cycles.
- fig. S6. SEM images of P2-NaNM and P2-NaNMT electrodes after long cycles.
- fig. S7. Charge/discharge profiles of P2-NaNM and P2-NaNMT electrodes between
2.5 and 4.3 V.
- fig. S8. Cycling performance comparison of P2-NaNM and P2-NaNMT electrodes
at 0.1 C in the voltage range of 2.5 to 4.3 V during 100 cycles.
- fig. S9. CVs of P2-NaNM and P2-NaNMT electrodes.
- fig. S10. XPS spectra of P2-NaNM and P2-NaNMT powders.
- fig. S11. Variation of lattice constants and unit cell volume during cycling.
- fig. S12. Schematic illustration for P2-O2 phase transition.
- fig. S13. In situ XRD patterns of P2-NaNM and P2-NaNMT electrodes between 2.5
and 4.3 V.
- fig. S14. GITT curves and the quasi-equilibrium potential as a function of the
stoichiometry.
- fig. S15. Calculated Na chemical diffusion coefficients from GITT.
- fig. S16. OCV decay of P2-NaNM and P2-NaNMT electrodes.
- fig. S17. Nyquist plots of EIS and the fit for P2-NaNM and P2-NaNMT electrodes.
- fig. S18. MSD curves for each kind of ions in P2-Na0.58NMT.
- table S1. Crystallographic parameters of P2-NaNM refined by the Rietveld method.
- table S2. Crystallographic parameters of P2-NaNMT refined by the Rietveld method.
- table S3. Atomic distances, slab thickness, and d-spacing of the Na layer and interslab distance for as-prepared materials.
- table S4. Summary of Na+ diffusion coefficients and activation energies in layered oxides.
Files in this Data Supplement:
- fig. S1. Powder XRD patterns of as-synthesized P2-NaNM and P2-NaNMT samples.
