Lattice stability and limits to charge transfer in intercalated graphite

It is shown that anodic oxidation of graphite in ${\mathrm{H}}_2$S${\mathrm{O}}_4$ ultimately leads to creation of C-O covalent bonds which act as carrier scattering centers, degrading the metallic behavior of the intercalation compound. This effect sets in at a carrier density corresponding to 0.03-0.05 free holes per carbon atom, thus implying a fundamental limitation to the basal plane conductivity of acceptor compounds. It is argued that a covalent component to the interlayer interaction is, in fact, necessary to stabilize the structure when the density of charged intercalant exceeds a certain limit.