Donor intercalation compounds

As mentioned in Section 3, graphite reacts readily with molten alkali metals or their vapors to give donor intercalation compounds. The first alkali metal compounds were patented very early on [81,82]. A few years later Fredenhagen and co-workers [83,84] reported that graphite intercalation compounds of the formula MCg were prepared during the reaction between graphite and alkali metal vapour (K, Rb and... 

Raman spectra have also been reported on ropes of SWCNTs doped with the alkali metals K and Rb and with the halogen Br2 [30]. It is found that the doping of CNTs with alkali metals and halogens yield Raman spectra that show spectral shifts of the modes near 1580 cm" associated with charge transfer. Upshifts in the mode frequencies are observed and are associated with the donation of electrons from the CNTs to the halogens in the case of acceptors, and downshifts are observed for electron charge transfer to the CNT from the alkali metal donors. These frequency shifts of the CNT Raman-active modes can in principle be u.sed to characterise the CNT-based intercalation compound for the amount of intercalate uptake that has occurred on the CNT wall. 

Titanium disulfide has a Cdl2 structure (see Chapter 1). The solid is golden-yellow and has a high electrical conductivity along the titanium layers. Forming intercalation compounds with electron donors can increase the conductivity of titanium disulfide, the best example being with lithium, LLTiS2. This compound is synthesized in the cathode... 

Several insulating inorganic solids possessing sheet structures, for example, silicates belonging to the pyrophyllite family (Thomas, 1982), and acid phosphates (Alberti Constantino, 1982 Clearfield, 1981) of some tetravalent metals form intercalation compounds with a variety of donor molecules in these cases, intercalation does not involve a redox process, unlike in the cases of transition metal chalcogenides and... 

Alkali metals and bromine react with graphite to form solids known as intercalation compounds, where the foreign atoms are inserted between the intact graphite layers. Many other layered solids, for example dichalcogenides such as TaS2, which have structures similar to Cdl2 will also for intercalation compounds. The inserted species may be alkali metals, or electron donor molecules such as amines or organometallic compounds. 

Graphite intercalation compounds have received widespread interest for two main reasons. First, intercalation results in compounds that have metallic conductivity. The electrical conductivity can approach that of copper metal and is highly anisotropic ratios of the conductivity in-plane to that along the c axis can be six orders of magiutude at room temperature. Secondly, graphite is a unique host lattice in that intercalation compounds can be formed with either electron donors or electron acceptors as guest species. 

It forms both types of intercalation compounds, donor (D) and acceptor (A) type. This is quite in contrast to most of the other inorganic host lattice such as, for example, TiSa [31], VaOg, CrgOg, MnOa, C0O2, and many others [29], where D-type compounds, mostly with Li+, are absolutely preferred The reason for this is that graphite is a metal, with a Fermi potential of about —0.2 V vs. SHE (see... 

If GO is used as a host lattice for Li+ in aprotic electrolytes, reversibility is improved [577]. The potential level is distinctly more positive than with donor GIC, at about —1 V vs. SHE. An all-solid-state Li/GO battery with PE0/LiC104 as solid electrolyte was reported by Mermoux and Touzain [578], but rechargeability is poor. Recently, the structure of graphite oxide was studied by its fluorination at 50-2()0 °C [579]. C-OH bonds were transformed into C-F bonds. The examples, in conjunction with Section 2, show that the formation or cleavage of covalent C-O (C-F) bonds makes the whole electrochemical process irreversible. Application was attempted in lithium primary batteries, which have a voltage of 2-2.5 V. Really reversible electrodes are only possible, however, with graphite intercalation compounds, which are characterized by weak polar bonds. 

Hydrazine is bound more tightly than ammonia in intercalation compounds with layer disulphides such as TaS2. ° This supports the formulation of these compounds as electron donor-acceptor complexes, as both the dipole moment (1.75 D) and ionization energy (/ = 8.7 eV) of N2H4 indicate that it is a better electron donor than NH3 (dipole moment = 0.58 D, = 10.2 eV). 

Reduction yields lamellar cation intercalation compounds that can be solvated. Solvated cation compounds are formed in donor electrolytes, i.e., solutions of alkali- or NR4-salts in solvents such as NHj or DMSO some binary (= unsolvated) cation compounds can be obtained in molten salt or solid electrolytes. 

A considerable number of molecules have been intercalated in group IVA and VA transition-metal disulfides and diselenidesh No stable compounds have been isolated with the ditellurides. Only electron-donor base-type molecules form intercalation compounds, which is a major difference from graphite. 

Yb) were synthesized and under definite conditions, compounds with iron were obtained. Graphite acts as a donor of electrons when it interacts with halogens, and intercalation compounds with Br2, ICl, IBr molecules are easily formed, while the compound with CI2 is extremely unstable. At low temperatures (15-100°C), graphite interacts with fluorine with the help of catalysts (HF, AgF). This fluorination results in the formation of graphite... 

Intercalation compounds Alkali metals react with graphite in such a way that they get between the layers of graphite and cause the layers to expand. Intercalation compounds are commonly composed of the alkali metals, bromine, or some electron donor molecules such as amines or organometallic compounds. This is found in lithium ion batteries, for example. 

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