Graphite intercalation compound

In particular, the sheets of carbon that comprise graphite can be pried apart by the insertion (intercalation) of ions.

Intercalation is often reversible: the inserted ions can be removed and the sheets of carbon collapse to a graphite-like structure.

[4][5] KC8 is a superconductor with a very low critical temperature Tc = 0.14 K.[6] Heating KC8 leads to the formation of a series of decomposition products as the K atoms are eliminated:[citation needed] Via the intermediates KC24 (blue in color),[3] KC36, KC48, ultimately the compound KC60 results.

Quantum-mechanical calculations show that this originates from a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same group of the periodic table.

[8] The phenomenon arises from the competition between trends in the ionization energy and the ion–substrate coupling, down the columns of the periodic table.

[8] However, considerable Na intercalation into graphite can occur in cases when the ion is wrapped in a solvent shell through the process of co-intercalation.

Cathodic reduction of graphite perchlorate is analogous to heating KC8, which leads to a sequential elimination of HClO4.

Examples include MCl2 (M = Zn, Ni, Cu, Mn), MCl3 (M = Al, Fe, Ga), MCl4 (M = Zr, Pt), etc.

Tetracarbon monofluoride (C4F) is prepared by treating graphite with a mixture of fluorine and hydrogen fluoride at room temperature.

It has been studied as a cathode material in one type of primary (non-rechargeable) lithium batteries.

Graphite intercalation compounds have fascinated materials scientists for many years owing to their diverse electronic and electrical properties.

Among the superconducting graphite intercalation compounds, CaC6 exhibits the highest critical temperature Tc = 11.5 K, which further increases under applied pressure (15.1 K at 8 GPa).

[6] Superconductivity in these compounds is thought to be related to the role of an interlayer state, a free electron like band lying roughly 2 eV (0.32 aJ) above the Fermi level; superconductivity only occurs if the interlayer state is occupied.

[11] Analysis of pure CaC6 using a high quality ultraviolet light revealed to conduct angle-resolved photoemission spectroscopy measurements.

A new essential application for potassium graphite was introduced by the invention of the potassium-ion battery.