Science Advances

Supplementary Materials

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  • Fig. S1. TG and DSC curves of (A) precursor C6H4O4 and (B) Na2C6H2O4.
  • Fig. S2. Microstructure of as-prepared Na2C6H2O4.
  • Fig. S3. Different structure evolution processes between the first and the second cycle.
  • Structure solution and Rietveld refinement of Na3C6H2O4 and Na4C6H2O4
  • Fig. S4. XRD pattern and Rietveld refinement of Na3C6H2O4 structure.
  • Fig. S5. XRD pattern and Rietveld refinement of Na4C6H2O4 structure.
  • Fig. S6. The positions and coordination environment of sodium atoms in Na2C6H2O4, Na3C6H2O4, and Na4C6H2O4.
  • Fig. S7. Change of sodium atom local structure during sodium extraction.
  • Fig. S8. The atomic position illustration of C and O atoms.
  • Fig. S9. The molecular structure (A) and schematic illustration (B) of the orthorhombic Na2C8H4O4.
  • Model construction of DFT calculations
  • Fig. S10. Polarization between discharge and charge.
  • Fig. S11. UV-vis absorption spectra of Na2C6H2O4.
  • Fig. S12. The second discharge/charge curves of Na2C6H2O4 at a current rate of C/10.
  • Table S1. The sodium storage properties for different reported negative electrode materials for sodium-ion batteries.
  • Table S2. Structural parameters.
  • Table S3. Structural parameters.
  • Table S4. Structural parameters.
  • Table S5. Bond lengths for Na2C6H2O4, Na3C6H2O4, and Na4C6H2O4.
  • References (33–35)

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