Nongraphitizable carbons

Lithium Insertion into Low-Temperature and Nongraphitizable Carbons... 

FIGURE 26.6 Schematic structural models of (a) graphitizable and (b) nongraphitizable carbons. 

In large scale production only solid and liquid, preferably meltable, starting materials are important. The raw materials used are almost all more or less graphitizable. Nongraphitizable carbon is, as special carbon, of minor industrial importance. It is also produced by gas phase pyrolysis of special carbon and graphite types and is dealt with in Section 5.7.5. Carbon fibers have already been dealt with in Section 5.2.3.3. 

Figure 2.18 Harris model for the structure of nongraphitizable carbons based on fuUerene-like elements. (Reproduced from Ref. [88]. Copyr ht Maney PubUshing.)...

Figure 1.13 Comparison of crystallite growth as a consequence of heat treatment of graphitizable and nongraphitizable carbons. (From ref. 273.)...

Kureha Corporation has developed nongraphitizable carbons (so-called hard carbon) prepared from the cross-linked petroleum pitch for almost 20 years as an anode of the lithium-ion battery (LIB). However, in these years graphite is more popularly used as an anode of LIB of small portable equipment, such as cellular phones, digital cameras, and portable personal computers, because high-energy density is much more important in this type of application than long-life durability is. Hard carbon has been used only in the field of professional camcorders, satellites, and electric bikes because it seemed to be difficult to change a new battery at the end of its life. 

Three types of carbonaceous materials can be used as anode active materials, i.e. graphite, graphitizable carbon and nongraphitizable carbon (the so-called hard carbon) (Figure 2.1). 

It is recognized that nongraphitizable carbon (hard carbon) consists of small crystallites with several layers that are oriented randomly and that its crystallites have a doo2 spacing greater than 0.372 nm. 

It is hardly credible that a process (carbonization) involving a low HTT leads to pure carbon. In fact, this notion is well known not to be true abundant hetero-atoms are still present after carbonization, regardless of the sample studied (e.g., chlorine in polyvinyl and polyvinylidene chloride H,0,N,S in coals, chars, cokes, or nongraphitizable carbons). Even the hydrogen inherent to aromatic molecules is too often not taken into account, a notable exception being the pioneering studies by Biscoe and Warren [71] and Warren [72]. 

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