Basal plane of the carbon/graphite particles

The reaction at the anode in Li-Ion cells is given in Equation 1. During charge the lithium ions approach the surface of the carbon where they accept an electron and enter the lattice. On discharge, the opposite reaction occurs. The electrochemical reaction is thought to occur on the edge planes and not the basal plane of the carbon/graphite particles. 

Site of the. acidic surface oxides. The question whether the acidic surface oxides are bound to the periphery of the carbon layei-s or to the basal planes of the crystallites could be resolved by oxidation of a graphitized carbon black (46). The particles of carbon black are, at first approximation, spherical. The graphite-like crystallites show such preferential orientation that their c axis are aligned in a radial direction (64, 65). A schematic representation of this secondary structure is given in Fig. 1. On recrystallization between 2000 and 3000°, many small... 

Basically, the effect of the surface nanotexture on the strength of metal-carbon bonding may occur as a result of epitaxy or interdiffusion of atoms in the contact region of a metal crystallite and carbon support. However, information concerning these aspects of the metal-carbon interaction is scarce. Graphite-supported Pd and Pt crystallites are oriented their 202 for Pd [19] and 111 or 110 for Pt [20-22] planes parallel to the basal plane of graphite substrate, but this epitaxial interaction is relatively weak [19-21,23]. In contrast, Pd particles supported on amorphous carbons are in random orientation [19,25]. Hence, heterogeneous support surfaces comprise structurally different sites for metal-particle stabilization. 

Even a single carbon particle has a complex structure with several forms. For example, an active carbon particle (SPECTRACAB) contains randomly oriented single-layers, bilayers, and trilayers of small graphite sheets. These graphite sheets contain two orientations, the basal plane, and the edge plane [14]. Due to the different differential capacitances of the many forms of carbon, it is difficult to choose a differential capacitance value for the calculation. For carbon materials, the differential capacitance is between 0.05 and 1.0 F.cm and depends on the carbon form and electrolyte used. 

Usually it is difficult to separate the effect of ciystallite size on carbon reactivity from the effects of crystallite orientation and impurity content. However, Armington (62) attempted to do so by reacting a series of graphi-tized carbon blacks with oxygen and carbon dioxide, as discus.sed earlier in this article. Assuming that upon graphitization all the carbon blacks are converted to polyhedral particles with the surface composed almost completely of basal plane structure, it is possible to eliminate crystallite orientation as a variable. Spectroscopically, the total impurity content of all the graphitized carbon blacks is quite low and to a first approximation, the analyses of the individual constituents are similar. 

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