Anode carbon-lithium

The work presented in this chapter involves the study of high capacity carbonaceous materials as anodes for lithium-ion battery applications. There are hundreds and thousands of carbonaceous materials commercially available. Lithium can be inserted reversibly within most of these carbons. In order to prepare high capacity carbons for hthium-ion batteries, one has to understand the physics and chemistry of this insertion. Good understanding will ultimately lead to carbonaceous materials with higher capacity and better performance. 

J.R. Dahn, A.K. Sleigh, Hang Shi, B.W. Way, W.J. Weydanz, J.N. Reimers, Q. Zhong, and U. von Sacken, Carbons and Graphites as Substitutes for the Lithium Anode , in Lithium Batteries, G. Pistoia, Elsevier, North Holland (1993). 

In general, lithium-ion batteries are assembled in the discharged state. That is, the cathode, for example LqCoC, is filly intercalated by lithium, while the anode (carbon) is completely empty (not charged by lithium). In the first charge the anode is polarized in the negative direction (electrons are inserted into the carbon) and lithium cations leave the cathode, enter the solution, and are inserted into the carbon anode. This first charge process is very complex. On the basis of many reports it is presented schematically [6, 74, 76] in Fig. 5. The reactions presented in Fig. 5 are also discussed in Sec. 6.2.1, 6.2.2 and 6.3.5. 

Unfortunately, both lithium and the lithiated carbons used as the anode in lithium ion batteries (Li C, l>x>0) are thermodynamically unstable relative to solvent molecules containing polar bonds such as C-O, C-N, or C-S, and to many anions of lithium salts, solvent or salt impurities (such as water, carbon dioxide, or nitrogen), and intentionally added traces of reactive substances (additives). 

Commercial and non-commercial carbons were tested for their applicability as anode of lithium-ion battery. It was found that Superior Graphite Co s materials are characterized both by high reversible capacities and low irreversible capacities and thus can be regarded as good candidates for practical full cells. Cylindrical AA-size Li-ion cells manufactured using laboratory techniques on the basis of SL-20 anode had initial capacities over 500 mAh (volumetric energy density ca. 240 Wh/dm3). Boron-doped carbon... 

Zheng, L., Zhong Q., and Dahn J.R. High-Capacity Carbons Prepared from Phenolic Resin for Anodes of Lithium-Ion Batteries. J. Electrochem. Soc., 142, 211-214 (1995). 

In this paper, we presented new information, which should help in optimising disordered carbon materials for anodes of lithium-ion batteries. We clearly proved that the irreversible capacity is essentially due to the presence of active sites at the surface of carbon, which cause the electrolyte decomposition. A perfect linear relationship was shown between the irreversible capacity and the active surface area, i.e. the area corresponding to the sites located at the edge planes. It definitely proves that the BET specific surface area, which represents the surface area of the basal planes, is not a relevant parameter to explain the irreversible capacity, even if some papers showed some correlation with this parameter for rather low BET surface area carbons. The electrolyte may be decomposed by surface functional groups or by dangling bonds. Coating by a thin layer of pyrolytic carbon allows these sites to be efficiently blocked, without reducing the value of reversible capacity. 

H. Buqa, P. Golob, M. Winter, J. O. Besenhard. Modified carbons for improved anodes in lithium ion cells. J. Power Sources 2001 97-98 122-25. 

Application to the Study of Carbon Anodes for Lithium-Ion Batteries... 

Tao Zheng, W. Xing and J.R. Dahn, Carbons Prepared from Coals for Anodes of Lithium-Ion Cells, Carbon, 34(J2), pp. 1501-1507(1996). 

Carbonized sugar derivatives are used as solid acid catalysts for the production of biodiesel fuel,349 and carbonized sucrose treated with ethylene and then pyro-lyzed provides materials used as hard-carbon anodes for lithium-ion batteries.439... 

Imanishi N, Takeda Y, Yamamoto O. (Eds.). Development of the carbon anode in lithium ion batteries. In Wakihara M (Ed.), Lithium Ion Batteries Fundamentals and Performance. Wiley-VCH, New York, 1998 98. 

Zheng T, Zhong Q, Dahn JR. High-capacity carbons prepared from phenolic resin for anodes of lithium-ion batteries. J Electrochem Soc 1995 142 L211-L214. 

Zheng T, Xing W, Dahn JR. Carbons prepared from coals for anodes of lithium-ion cells. Carbon 1996 34 1501-1507. 

Ng SH, Wang J, Guo ZP, Chen J, Wang GX, Liu HK. Single wall carbon nanotube paper as anode for lithium-ion battery. Electrochim Acta 2005 51 23-28. 

Similar to the behavior of nonactive metal electrodes described above, when carbon electrodes are polarized to low potentials in nonaqueous systems, all solution components may be reduced (including solvent, cation, anion, and atmospheric contaminants). When the cations are tetraalkyl ammonium ions, these reduction processes may form products of considerable stability that dissolve in the solution. In the case of alkali cations, solution reduction processes may produce insoluble salts that precipitate on the carbon and form surface films. Surface film formation on both carbons and nonactive metal electrodes in nonaqueous solutions containing metal salts other than lithium has not been investigated yet. However, for the case of lithium salts in nonaqueous solvents, the surface chemistry developed on carbonaceous electrodes was rigorously investigated because of the implications for their use as anodes in lithium ion batteries. We speculate that similar surface chemistry may be developed on carbons (as well as on nonactive metals) in nonaqueous systems at low potentials in the presence of Na+, K+, or Mg2+, as in the case of Li salt solutions. The surface chemistry developed on graphite electrodes was extensively studied in the following systems ... 

A major part of the work with nonaqueous electrolyte solutions in modern electrochemistry relates to the field of batteries. Many important kinds of novel, high energy density batteries are based on highly reactive anodes, especially lithium, Li alloys, and lithiated carbons, in polar aprotic electrolyte systems. In fact, a great part of the literature related to nonaqueous electrolyte solutions which has appeared during the past two decades is connected to lithium batteries. These facts justify the dedication of a separate chapter in this book to the electrochemical behavior of active metal electrodes. 

A wide variety of carbonaceous materials can intercalate or insert lithium reversibly and thus may be candidates for anodes for lithium ion batteries. In recent years, many types of carbons have been tested as alternative anodes for rechargeable lithium batteries, part of which have found use as anodes in practical, commercial lithium ion batteries. The most straightforward way of classifying these electrodes is according to the type of the carbon, which determines their capacity and basic electrochemical behavior. The major types of carbons tested in recent years as anode materials for Li ion batteries are listed below ... 

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