Intercalation lithium

In the lithium-ion approach, the metallic lithium anode is replaced by a lithium intercalation material. Then, tw O intercalation compound hosts, with high reversibility, are used as electrodes. The structures of the two electrode hosts are not significantly altered as the cell is cycled. Therefore the surface area of both elecftodes can be kept small and constant. In a practical cell, the surface area of the powders used to make up the elecftodes is nomrally in the 1 m /g range and does not increase with cycle number [4]. This means the safety problems of AA and larger size cells can be solved. 

It is not surprising that it is difficult to insert lithium between parallel layers which are randomly stacked. When lithium intercalates between AB stacked layers, a shift to AA stacking occurs [26]. It is likely that the turbostratically stacked layers are pinned by defects (which can only be removed near 2300°C ) preventing the rotation or translation to AA stacking. Thus, we can understand why varies as 372(1-P), the fraction of layers with AB registered stacking. More studies of the details of the voltage profiles in Fig. 7 can be found elsewhere [6,7,27]. 

The electrochemical performance of lithiated carbons depends basically on the electrolyte, the parent carbonaceous material, and the interaction between the two (see also Chapter III, Sec.6). As far as the lithium intercalation process is concerned, interactions with the electrolyte, which limit the suitability of an electrolyte system, will be discussed in Secs. 5.2.2.3,... 

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. 

Because of the variety of available carbons, a classification is inevitable. Most carbonaceous materials which are capable of reversible lithium intercalation can be classified roughly as graphitic and non-graphitic (disordered). 

Today we have some understanding of the first lithium intercalation step into carbon and of the processes taking place on the lithium metal anode. A combination of a variety of analytical tools including di-latometry, STM, AFM, XPS, EDS, SEM, XRD, QCMB, FTIR, NMR, EPR, Raman spectroscopy, and DSC is needed in order to understand better the processes occurring at the anode/electrolyte interphase. This understanding is crucial for the development of safer and better lithium-based batteries. 

Because of the reactivity of lithium or lithium intercalated in carbon, protic solvents cannot be used in lithium batteries because hydrogen would be formed according to Eq. (1). 

Balkanski M, Kambas K, Julien C, Hammerberg J, Schleich D (1981) Optical and transport measmements on Lithium intercalated a-ln2Se3 layered compounds. Sohd State Ionics 5 387-390... 

Kanehori K, Matsumoto K, Miyauchi K, Kudo T (1983) Thin film solid electrolyte and its application to secondary Lithium cell. Solid State Ionics 9-10 1445-1448 Py MA, Haering RR (1983) Structural destabilization induced by lithium intercalation in M0S2 and related compounds. Can J Phys 61 76-84... 

The properties of lithium intercalation compounds depend in a decisive manner on the nature of the host material. If oxides of metals with varying valency are used instead of TiSj, the potential of the electrode (consequently also, the battery voltage) will increase to 3 V. Even higher values (up to 4 V) are obtained when as host material... 

Intercalation compounds of lithium and other species into the layered structure of graphite, synthesized by chemical methods, have been known for a long time. In the mid-1980s, the possibility of a reversible lithium intercalation from apro-tic solutions containing lithium salts into certain carbonaceous materials was discovered ... 

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. 

Figure 4. Depiction of lithium intercalated into the carbon/graphite lattice.

Figure 17. The basal plane and prismatic surfaces of graphite have different functions with respect to lithium intercalation and de-intercalation (= charge, discharge, self-discharge, etc.). As a consequence, only the electrolyte decomposition product layers at the prismatic surfaces have SEIfunction. Any processes related with electrolyte decomposition product layers at the basal plane surfaces (= non-SEI layers) therefore can not be directly related to electrochemical data such as charge, discharge, self-discharge, etc. The situation is even more complex as the SEI composition and morphology at the basal and prismatic surface...

Due to its high energy density (3,860 mAh/g) and low voltage, lithium is the most attractive metal of the periodic table for battery application. Unfortunately lithium metal, and most of its alloys cannot be used in rechargeable batteries because of their poor cyclability. Therefore, lithium intercalation compounds and reversible alloys are among today s materials of choice for subject application. The most common active materials for the negative electrodes in lithium-ion battery applications are carbonaceous materials. The ability of graphitized carbonaceous materials to... 

Billaud D., Henry F.X. and Willmann P. Electrochemical Synthesis of Binary Graphite-Lithium Intercalation Compounds. Mat. Res. Bull., 28, 477-483 (1993). 

According to equation 2, the amounts of each phase should vary linearly with intercalated lithium intercalated beyond LiCi2. 

Figure 5. Composition dependence of the average graphene interlayer spacing during the lithium intercalation and de-intercalation.

Figure 6. The entropy of lithium intercalation into natural graphite, after [22],...

Composite electrodes made of two carbon components were evaluated experimentally as anodes for Li-ion batteries. The electrochemical activity of these electrodes in the reaction of reversible lithium intercalation ffom/to a solution of LiPF6 in ethyl carbonate and diethyl carbonate was studied. Compositions of the electrode material promising for the usage in Li-ion batteries were found. 

The source carbon materials show a significant electrochemical activity for lithium intercalation though the reversible capacity is relatively low and tends to reduce with cycling. For the thermally expanded graphite... 

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