Graphite, intercalation compounds bonding

GO does not seem to be suitable as a reversible battery electrode. The reason is the irreversible formation of covalent C-O(H) bonds in the course of anodic formation. According to Boehm and to Ubbelohde, graphite intercalation compounds do play the role of a precursor ... 

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. 

M. Winter, K.-C. Moeller, J.O. Besenhard, Chapters Carbonaceous and graphitic anodes , section 5.3.2.3 Nature of the bond in Li-graphite intercalation compounds , in G.-A. Nazri, G. Pistoia (Eds) Lithium-ion Battery, Science technology, 2009. 

Group 14. - 3.14.1 Carbon. The bonding structure in amorphous carbon nitride has been studied by H, and NMR spectroscopy. A F NMR study of paramagnetism in fluorinated graphite has been reported. Carbon-fluorine bonding has been detected in fluorine-graphite intercalation compounds by and F NMR spectroscopy. ... 

The properties of the intercalation compound, potassium graphite, KCg, have been detailed in several review articles.34/35 The bonding in potassium graphite is described in terms of the limiting structure, K+Cg", and it is believed that the anion forms as a result of the transfer of an electron from the alkali metal to the conduction band of graphite. Novikov and Volpin35 have noted a similarity between aromatic radical-anions and alkali metal-graphite intercalation compounds. Their observation was based on inspection of reduction potentials of aromatic hydrocarbons relative to biphenyl, Table 9.2 ... 

Many layered solids form intercalation compounds, where a neutral molecule is inserted between weakly bonded layers. For example when potassium vapour reacts with graphite above the melting temperature of potassium (337 K), it forms a golden compound KCs in which the potassium ions sit between the graphite layers, and the inter-layer spacing is increased by 200 pm (Figure 3.16). Addition of a small amount of KO2 to the molten potassium results in the formation of a double layer of potassium atoms between the graphite layers and a formula close to KC4. 

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