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15.2 Graphitic and Nongraphitic Carbons 441

by the pyrolysis of petroleum pitch, which is the residue from the distillation of
petroleum fractions. Cokes are also products from pyrolysis of coal tar pitch and
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aromatic hydrocarbons at 300–500 C. Carbon black, pyrocarbon, and carbon films
are examples of gas-phase pyrolysis products, that is, products of thermal cracking
of gaseous hydrocarbon compounds which are deposited as carbon on a substrate
[66, 71].
The ability to graphitize also depends on the pre-ordering and pre-texture of
the respective precursor. For example, the graphitization ability is higher (i) if the
precursor material comprises highly condensed aromatic hydrocarbons which can
be considered to have a graphene-like structure and (ii) if neighboring graphene
layers or graphitic crystallites are suitably orientated to each other.
Apart from manifold structures, carbons can have various shapes, forms, and tex-
tures, including powders with different particle size distributions, foams, whiskers,
foils, felts, papers, fibers [75, 76], spherical particles [75] such as mesocarbon
microbeads (MCMBs) (Nakagawa, Y. Osaka Gas Chemicals Co., Ltd., personal
communication), and so on. Comprehensive overviews are given, for example, in
Refs [66, 70, 71]. Further information on the synthesis and structures of carbona-
ceous materials can be found in Refs [66, 69, 71, 74, 77]. Details of the surface
composition and surface chemistry of carbons are reviewed in Part II, Chapter 11,
and in Part III, Chapter 17, of this handbook. Some aspects of surface chemistry of
lithiated carbons will also be discussed in Section 15.2.2.3.

15.2.2
Lithiated Graphitic Carbons (Li x C n )

15.2.2.1 In-Plane Structures
The first lithiated graphitic carbons were lithium–graphite intercalation com-
pounds, abbreviated as Li–GICs (Li x C n ), and were obtained by chemical synthesis
in the mid-1950s [78, 79]. At ambient pressure, a maximum lithium content of
one Li guest atom per six carbon host atoms can be reached for highly crystalline
graphite (n ≥ 6inLiC n or x ≤1inLi x C 6 ). The intercalation reaction proceeds via
the prismatic surfaces (armchair and zig-zag faces). Through the basal plane,
intercalation is possible at defect sites only. During intercalation the stacking order
of the graphene layers shifts to AA. Thus, two neighboring graphene layers in
LiC 6 directly face each other (Figure 15.5a). The energetically favored AA stacking
sequence of LiC 6 has been proved by ab initio studies [80]. Due to the hosted
lithium, the interlayer distance between the graphene layers increases moderately
(10.3% has been calculated for LiC 6 [35, 81]). The stacking order of the lithium
interlayers is αα (a Li-C 6 -Li-C 6 -Li chain exists along the c-axis) [82, 83]. In LiC 6
the lithium is distributed in-plane in such a manner that the occupation of the
nearest-neighbor sites is avoided (Figure 15.5b).
A higher lithium in-plane density by occupation of nearest-neighbor sites is
obtained in the phases LiC 2 –LiC 4 ,thatis, x = 2–3 in Li x C 6 ,which arepre-
pared chemically from graphitic carbon under high pressure (∼60 kbar) and high
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temperature (∼300 C) conditions [43, 84–87]. The close Li-Li distance in LiC 2