Graphite, as negative electrode

Wang, H. Y, and M. Yoshio. 2012. Feasibility of quaternary alkyl ammonium-intercalated graphite as negative electrode materials in electrochemical capacitors. Journal of Power Sources 200 108-112. 

R. Yazami, K. Zaghib, and M. Deschamps, Carbon fibres and natural graphite as negative electrodes for lithium ion-type batteries, J. Power Sources, 52,52-59 (1994). 

PC is also a very useful solvent of LIBs because of its superior ionic conductivity over a wide temperature range. However, despite the close structural similarity between EC and PC, PC cannot form as effective SEI films as EC does, for LIBs that employ graphite as negative electrodes. " To enable to use PC in these batteries, there have been a lot of efforts focusing on the identification of proper additives and/or co-solvents for PC-based electrolytes, which would help to generate an efficient SEI layer. The typical liquid additives include chloroethylene carbonate (CEC), other halogen-substituted carbonates, a variety of unsaturated carbonates such as vinylpropylene carbonate and vinylene carbonate, and ethylene/propylene sulfite (ES/PS). The most common co-solvents are DMC, DEC, EMC, y-butyrolactone (y-BL), dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), dimethyl amide (DMA), 1,2-dimethoxy-ethane (DME) and 1,2-dimethoxy-methane (DMM). To explore the role of these additives and co-solvents, it is necessary to understand their structures and some properties that may affect the SEI formation on graphite anodes. 

Electrochemical Performance of Graphite as Negative Electrode Material... 

The intercalation compounds of lithium with graphite are very different in their behavior from intercalation compounds with oxides or halcogenides. Intercalation processes in the former compounds occur in the potential region from 0 to 0.4 V vs. the potential of the lithium electrode. Thus, the thermodynamic activity of lithium in these compounds is close to that for metallic lithium. For this reason, lithium intercalation compounds of graphite can be used as negative electrodes in batteries rather than the difficultly of handling metallic lithium, which is difficult to handle. 

At the end of the 1990s in Japan, large-scale production of rechargeable lithium ion batteries was initiated. These contained lithium compounds intercalated into oxide materials (positive electrodes) as well as into graphitic materials (negative electrode). The development of these batteries initiated a further increase in investigations of the properties of different intercalation compounds and of the mechanism of intercalation and deintercalation processes. 

From the Li-ion battery technology, it is known that carbons can be intercalated at more negative potentials than any other Li-intercalation material (see Figure 8.30). In commercial Li-ion batteries, two kinds of carbon materials are mainly used as negative electrode (1) nongraphitizable or hard carbons (HCs) and (2) graphite. 

Holzapfel M, Buqa H, Krumeich F, Novak P, Petrat FM, Veit C. Chemical vapor deposited silicon/ graphite compound materials as negative electrode for lithium-ion batteries. Electrochem Solid-State Lett 2005 8 A516-A520. 

To avoid the problems associated with lithium metal, lithium insertion materials (e.g., graphitic carbons) are being investigated as negative electrodes. With respect to lithium metal, the use of negative insertion materials improves the cycle life and safety of the battery but lowers the cell voltage, the theoretical specific capacity, and the charge transfer rate [104]. 

A hybrid cell can be defined as a system in which only one electrode of the secondary cell is graphitic, carbonaceous, or organic, but the other is inorganic. The most important cells have metals as negative electrodes. Lithium cells of this kind have already been discussed in detail in Section 9.1 (cf. Table 10(a)). In this section, systems with other metals as the negative are considered see Table 11(a). They are organized in the same order as in this review. 

The electrochemical window determination shows that all the studied pyrrolidinium imides can be incorporated in the electrolyte for Li-ion battery except the P13-TFSI RTIL if a graphite electrode is used as negative electrode. These results are confirmed by the galvanostatic chronopotentiometric measurements to test the cycling ability with the electrolyte imder consideration. The best electrochemical performances are achieved in the presence of the 20%or 30% P14-TFSI RTIL mixtures... 

Change of potential during lithium intercalation and deintercalation when graphite is used as negative electrode in 1M LiPFj solution in EC/DEC/DMC (a) in the first cycle, (b) in the second cycle, and (c) enlarged part at low potential for the second cycle. Qi ev- irreversible capacity. (Adapted from Kanno, R. et al., /. Electrochem. Soc. 139,3397-3404,1992.)... 

From the previous discussion of graphitic carbons, it can be seen that they display some common characteristics when they are used as negative electrode materials, which are summarized here. 

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