ABSTRACT

I. INTRODUCTION Graphite is intercalated either by good reducing agents, often called donors, or by good oxidizing agents, frequently referred to as acceptors. Graphite is not intercalated by neutral species acting alone if these species are incapable of reducing or oxidizing the graphite (although, as will be discussed for particular cases, it is a relatively common occurrence for neutral molecules to be incor­ porated into graphite along with oxidizing or reducing guests). These observa­ tions can be accounted for simply. The unfavorable enthalpy change associated with separation of the carbon sheets necessary for the incorporation of a guest species, and the loss of translational entropy that often accompanies the place­ ment of the guest in the graphite host, are compensated for by favorable Cou­ lomb energy derived from electron transfer between host and guest. In a qual­ itative way this is in harmony with observation: the donor species are strongly reducing metals (such as alkali metals) and the acceptors are most often halides or oxides capable of oxidation to generate cationic-graphite salts of high ther­ modynamic stability.