Diverse Phenomena in Stage-n Graphite Alkali-Intercalation Compounds

The rich and unique properties of the stage-n graphite alkali-intercalation compounds are fully investigated by the first-principles calculations. According to the main features, the lithium and non-lithium systems are quite different from each other in stacking configurations, intercalant alkali-atom concentrations, the free conduction electron densities, atom-dominated and (carbon, alkali)-co-dominated energy bands, and interlayer charge density distributions. The close relations between the alkali-doped metallic behaviors and the geometric symmetries are clarified through the interlayer atomic interactions. The significant alkali-carbon chemical bondings are thoroughly examined from the atom- and orbital-decomposed van Hove singularities. Moreover, the blueshift of the Fermi level, the n-type doping, is clearly identified from the low-energy density of states. This study provides partial information about the anode of Li⁺-based battery, such as certain important differences between AC₆ and Li₈Si₄O₁₂.