Graphite insertion compounds

Fig. 6. Structural and stoichiometric aspects of graphitic and organic intercalation (insertion) compounds.

The next group of materials comprises conducting polymers (ICP). Systems with identical polymers have often been reported for polyacetylene. It is known that this ICP forms insertion compounds of the A and D types (see Section 6.4, and No. 5 in Table 12). Cells of this Idnd were successfully cycled [277, 281-283]. However, the current efficiency was only 35% heavy losses were observed due to an overoxidation of the PA [284]. In other cases as for polypyrrole (PPy), the formation of D-PPy was anticipated but did not occur [557, 558]. Entry (6) in Table 12 represents some kind of ideal model. A PPy/PPy cell with alkyl or aryl sulfates or sulfonates rather than perchlorates is claimed in [559]. Similar results were obtained with symmetric polyaniline (PANI) cells [560, 561]. Symmetric PPy and RANI cells yield about 60% current efficiency, much more than with PA. An undoped PPy/A-doped PPy combination yields an anion-concentration cell [562, 563], in analogy to graphite [47], (cf. No. 7). The same principle can be applied with the PPy/PT combination [562, 563] (cf. No. 8). Kaneto et al. [564] have reported in an early paper the combination of two pol54hiophene (PT) thin layers (< 1 pm), but the chargeability was relatively poor (Fig. 40, and No. 9 in Table 12). A pronounced improvement was due to Gottesfeld et al. [342, 343, 562, 563], who employed poly[3-(4-fluoro-phenyl)thiophene], P-3-FPT, in combination with a stable salt electrolyte (but in acetonitrile cf. Fig. 40 and No. 10 in Table 12). In all practical cases, however, Es.th was below 100 Wh/kg. 

Group 1. - 7Li NMR spectroscopy was used to characterise a lithium/ graphite intercalation compound with a formula close to LiC 1 In situ solid-state 7Li NMR data were reported for lithium inserted into disordered carbon. There was evidence for both Lis+ and metallic lithium species.2 7Li and 13C solid-state NMR spectra were used to characterise a mesoporous tantalum oxide lithium fulleride (Ceo) composite material.3... 

As explained in Topic B6 the synthesis of solids often requires high temperatures, because of the slow diffusion of atoms. In intercalation compounds and some insertion compounds however, diffusion of guest species is more facile, and such compounds can often be made prepared under fairly mild conditions, sometimes known as chimie douce ( gentle chemistry ). Intercalation compounds of graphite can be made directly by exposure of the solid to Br2 or to alkali metal vapors. 

The reaction of barium with graphite is reported to form a mixture of insertion phases and BaCj. The insertion compound BaCe crystallized in the space group Pba/mmc, with a =4.302 and c = 10.51 A. The compound is less reactive than alkali-metal graphite compounds. ... 

Graphite Intercalation Compounds.— The reactions of graphitizable carbons leading to the formation of graphite intercalation compounds have been reviewed. Emphasis was placed on the insertion of alkali metals (Na), halogens (Brg), and acids (H2SO4). The effects of electronic structure and electron exchange on intercalation reactions were also considered. 

Cyclohexyl and cyclopentyl bromides underwent rapid reaction with SbCl, in CCl to give vicinal trans- bromochlorides in high yield. The insertion compound of SbClj in graphite, Cj SbClj, was also employed with the above substrates, where the major products were cyclohexyl and cyclopentyl chlorides ca. 60 %) and smaller amounts (18—35%) of vicinal trans-bromochlorides. Cyclohexyl chloride was obtained in 86% and 22% yield from the iodide and tosylate. 

Herold A., Insertion compounds of graphite with bromine and the alkali metals. Bull. Soc. Chim. Fr. 187 (1955), 999-1012. 

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