Lithium storage

The quality and quantity of sites which are capable of reversible lithium accommodation depend in a complex manner on the crystallinity, the texture, the (mi-cro)structure, and the (micro)morphology of the carbonaceous host material [7, 19, 22, 40-57]. The type of carbon determines the current/potential characteristics of the electrochemical intercalation reaction and also potential side-reactions. Carbonaceous materials suitable for lithium intercalation are commercially available in many types and qualities [19, 43, 58-61], Many exotic carbons have been specially synthesized on a laboratory scale by pyrolysis of various precursors, e.g., carbons with a remarkably high lithium storage capacity (see Secs. 

In comparison with graphite, non-graphitic carbons can provide additional sites for lithium accommodation. As a result, they show a higher capability of reversible lithium storage than graphites, i.e., stoichiometries of x> in Li C6 are possible. 

Figure 11. Schematic drawing of some mechanisms for reversible lithium storage in "high-specific-charge" lithiated carbons as proposed in Refs, (a) [216], (b) [218, (c) [224], (d) [230], (e) [41], and (f) [238]. The latter figure has been reproduced with kind permission of Kureha Chemical Industry Co., Ltd.

Figure 12. Top Schematic model showing the mechanism of lithium storage in hydrogen containing carbons as proposed in Ref. [2471. Below Schematic charge/discharge curve of a hydrogen containing carbon.

An overview about more than 10 years of R D activities on solid electrolyte interphase (SEI) film forming electrolyte additives and solvents at Graz University of Technology is presented. The different requirements on the electrolyte and on the SEI formation process in the presence of various anode materials (metallic lithium, graphitic carbons, and lithium storage metals/alloys are particularly highlighted. 

SEI FORMATION AND SEI STABILITY ON LITHIUM STORAGE METALS AND ALLOYS... 

Electrolyte effects on the cycling stability of lithium storage metals and alloys indicate the importance of SEI formation in this case, too. Very early measurements suggest that additives such as CO2 do not only improve the cycling stability of metallic lithium [41] and graphitic carbons (see above), but also that of lithium storage metals (Fig. 18), which may be related with the electrical properties of the SEI (Fig. 19) [13]. 

Zhou, W., et al., A general strategy toward graphene metal oxide core-shell nanostructures for high-performance lithium storage. Energy Environmental Science, 2011. 4(12) p. 4954-4961. 

Chen, S., et al., Chemical-free synthesis of graphene-carbon nanotube hybrid materials for reversible lithium storage in lithium-ion batteries. Carbon, 2012. 50(12) p. 4557-4565. 

Su, Y., et al., Two-dimensional carbon-coated graphene/metal oxide hybrids for enhanced lithium storage. ACS Nano, 2012. 6(9) p. 8349-8356. 

The lithium-storage properties of these Si SiOx/C nanocomposite electrodes were investigated in different electrolyte systems and compared to pure Si nanoparticles. From all the analyzed systems, the Si SiOx-C nanocomposite in conjunction with the solvent vinylene carbonate (VC) to form the solid-electrolyte interface showed the best lithium storage performance in terms of a highly reversible lithium-storage capacity (1100 mAh g-1), excellent cycling performance, and high rate capability (Fig. 7.9). 

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