Elucidating the Origin of the Low Anion Intercalation Potential of Graphene-like Graphite: A DFT Study

Graphene-like graphite (GLG) exhibits significantly large capacity as a cathode material for dual-ion batteries (DIBs) because the anion intercalation reaction proceeds from a lower potential than that of graphite. In this study, the factors contributing to the characteristic low anion intercalation potential of GLG were investigated by density functional theory (DFT) calculations. Ketone-, lactone-, and ether-introduced graphites were used as models of GLG. The GLGs exhibited lower interlayer expansion energies than graphite, but their contribution to lowering the anion intercalation potential was quantitatively limited. On the other hand, the density of states (DOS) of the GLGs showed new bands at or below the Fermi level, indicating that the electron withdrawal from the host material can proceed from a lower potential. In addition, the energy and peak intensity of the bands correlated with the degree of lowering of the calculated anion intercalation potentials. Therefore, it was concluded that the change in the electronic state caused by the introduction of the oxygen-containing functional groups is the main cause of the characteristic low anion intercalation potential of GLG.