Lithium ions, intercalation graphite

These morphological changes (hill and blister formation) were attributed to the intercalation of solvated lithium ion into graphite interlayers and to the accumulation of its decomposition products (some of them gases), respectively. On the other hand, rapid exfoliation and rupturing of graphite layers were observed in ImolL-1... 

Hence, a dilemma was encountered between energy density and stability for these various forms of carbonaceous materials that is, as the carbonaceous anode is more graphitic in structure, the degree of lithium ion intercalation may be closer to the ideal x = 1.0), and its potential profile may be closer to that of Li+/Li and remain relatively flat (therefore... 

Figure 13. Correlation of gas evolution on a graphite electrode in 1.0 M LiC104/PC/EC (50 50) with the irreversible process at 0.80 V during the first discharge. Note the level off of gas volume as soon as reversible lithium ion intercalation starts. (Reproduced with permission from ref 261 (Figure 2). Copyright 1993 The Electrochemical Soci-ety).

Limiting Factors for Low-Temperature Operation. One controversial topic that has raised wide attention relates to the limiting factors of the low temperature of lithium ion cells. The researchers not only debated about whether the anode or cathode controls the overall low-temperature performance of a full lithium ion cell but also disagree upon the rate-determining steps that govern the low-temperature kinetics of lithium ion intercalation at the graphitic anode. 

At the end of Section 11.4, we described the different conditions under which Li, Na, K, Rb or Cs may be intercalated into graphite, and the application of lithium ion intercalation in lithium-ion batteries. We now look in more detail at the intercalation of potassium. 

The reversibility of this so-called intercalation reaction can be demonstrated by a subsequent electrochemical oxidation (discharge) of IixC , that is, the de-intercalation of Ii+. This is considered to be a special type of intercalation in that, unusually, a layer of guest ions slides between the sheets of a layered host matrix, while the host broadly retains its structural integrity. This occurs in the case of the insertion of lithium ions into graphite. In most cases, however, a strict differentiation between insertion and intercalation is a formal question and both terms are used inter-changeably. Following historical conventions, the terms intercalation and lithium/carbon intercalation compounds will be used in this review, even though only a small fraction of layered structure units may be present in a specific carbon material (see also Refs [2, 6]). 

Figure 26.15 Measured load changes as lithium ions intercalate into graphite as shown by the charge and current curves.

Y.-C. Chung, H.-J. Sohn, Electrochemical impedance analysis for lithium ion intercalation into graphitized carbons, J. Electrochem. Soc., 2000,147,1, pp. 50-58. 

C.S. Wang, A.J. Appleby and RE. Little, Electrochemical impedance study of initial lithium ion intercalation into graphite powders, Electrochim. Acta 46,2001, 1793-1813. 

Graphitic carbon is now used as the anode material in lithium-ion batteries produced by Moli Energy (1990) Ltd., Matsushita, Sanyo and A+T battery. It is important to understand how the structures and properties of graphitic carbons affect the intercalation of lithium within them. 

Carbon materials which have the closest-packed hexagonal structures are used as the negative electrode for lithium-ion batteries carbon atoms on the (0 0 2) plane are linked by conjugated bonds, and these planes (graphite planes) are layered. The layer interdistance is more than 3.35 A and lithium ions can be intercalated and dein-tercalated. As the potential of carbon materials with intercalated lithium ions is low,... 

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

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