Carbon-lithium intercalation

Because of the large area of electrodes so obtained, it is possible to achieve the current density necessary to produce a useful battery. The cathode is usually constructed by impregnation of carbon films with LiCo02 LiMn04 and the anode is a carbon-lithium intercalation compound. 

Further improvements in anode performance have been achieved through the inclusion of certain metal salts in the electrolyte, and more recently by dkect incorporation into the anode (92,96,97). Good anode performance has been shown to depend on the formation of carbon—fluorine intercalation compounds at the electrode surface (98). These intercalation compounds resist further oxidation by fluorine to form (CF ), have good electrical conductivity, and are wet by the electrolyte. The presence of certain metals enhance the formation of the intercalation compounds. Lithium, aluminum, or nickel fluoride appear to be the best salts for this purpose (92,98). 

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). 

The first lithiated graphitic carbons (lithium-graphite intercalation compounds, abbreviated as Li-GIC s),... 

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). 

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

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... 

Electrochemical Properties of Modified Carbons in the Reaction of Lithium Intercalation... 

In some cases, the kinetics of the redox charge— discharge reactions can proceed almost as quickly and reversibly as EDL charging. Thin film redox electrodes, based on the lithium intercalation/inser-tion principle such as Li4Ti50i2, exhibit high reversibility and fast kinetics. The Ru02 materials deposited on carbon show pseudo-capacitive charge—... 

Figure 11. (a) Initial IV2 cycles of a Li/petroleum coke cell. The cell was cycled at a rate of 12.5 h for Ax = 0.5 in Li sG6. (b) Initial IV2 cycles of a Li/graphite cell. The cell was cycled at a rate of 40 h for Ax= 0.5 in Li sG6. F denotes the irreversible capacity associated with SEI formation, E the irreversible capacity due to exfoliation, and I the reversible capacity due to lithium intercalation into carbon. 1.0 M LiAsEe in EC/PC was used as electrolyte. (Reproduced with permission from ref 36 (Eigure 2). Copyright 1990 The Electrochemical Society.)... 

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