Table 1 DFT calculation.

Total energies for Na2C6H2O4, Na3C6H2O4, and Na4C6H2O4 structures and comparison of DFT calculated and experimental reaction voltages.

StructureNa2C6H2O4Na3C6H2O4Na4C6H2O4Na
Energy (eV/U)−95.139−97.815−100.056−2.586
Reaction processNa2→Na4Na4→Na3Na3→Na2
Calculated voltage (V versus Na+/Na)1.170.951.38
Experimental voltage (V versus Na+/Na)1.211.311.49