Lithiated electrochemical reactions

The variety of nature, composition and structure of the compounds available as active materials causes a diversity of lithiation/de-lithiation electrochemical reactions. A classification can be established on the basis of the nature of the redox reaction that occurs in the active material to accommodate the lithium. This is what is done below. 

Figure 1.14. Diagram of electrochemical reactions during Sn lithiation/delithiation. Reprinted from [U 14c] with permission. Copyright 2014 American Chemical Society)...

Many partially lithiated (i.e., when x < 1) active materials in lithium-ion cells can be considered as solid solutions of mobile lithium (guest) in the host material—Z. Such host-guest material can be described by the similar set of thermodynamic equations as these used to characterize an amalgam. However, the mechanism of electrochemical reactions proceeding in a real ceU is much more complex than in the case of the reaction of silver amalgam formation. There are many factors complicating the overall process ... 

In addition to carbon, the attention has been focused on alloys and lithiated metal oxides as new materials for anodes in Li-ion cells. The reversible insertion of Li in metal/alloys has been studied for maity years because of their application in high-temperature molten salts Li cells. The electrochemical reactions that occur during discharge of a Li alloy electrode is ... 

In the Bacon ceU, the first successful modem fuel cell, porous nickel was used as a material for the electrodes, doing double duty as conductor and catalyst for the current-producing electrochemical reactions (in the cathode the nickel was lithiated). A little later, Justi introduced Raney nickel and Raney silver as the catalytic electrodes nickel for the hydrogen anode and silver for the oxygen... 

There have been a large number of studies on the electrochemical reaction of Li with Si and subsequent cycling behavior. While at high temperatures (415"C) the equilibrium crystalline Li-Si phases are formed during lithiation of ciystalline Si, at room temperature a solid-state amorphization occurs to form amorphous lithium silicide (a-Li [Pg.2]

In the case of the Sng2Ni3g electrode, the potential profile shows a slope that starts from 0.80 V vs. Li/Li and a plateau from 0.24 V vs. Li/Li. From the potential profile of the Sn electrode, the latter plateau can be assumed to be the formation of Li-rich Sn-Li alloy phases. 0.24 V vs. L /L is lower than the corresponding lithiation potential of the Sn electrode, which could indicate the higher overpotential associated with the electrochemical reaction to form Li-rich Sn-Li alloy phases in the Sn62Ni3g electrodes. The deflection profile shows only one flexion point of tensile stress increase which starts at 0.24 V vs. Unlike Sn, flexion points of the... 

Whereas the electrochemical decomposition of propylene carbonate (PC) on graphite electrodes at potentials between 1 and 0.8 V vs. Li/Li was already reported in 1970 [140], it took about four years to find out that this reaction is accompanied by a partially reversible electrochemical intercalation of solvated lithium ions, Li (solv)y, into the graphite host [64], In general, the intercalation of Li (and other alkali-metal) ions from electrolytes with organic donor solvents into fairly crystalline graphitic carbons quite often yields solvated (ternary) lithiated graphites, Li r(solv)yC 1 (Fig. 8) [7,24,26,65,66,141-146],... 

In the ideal situation of 100% utilization x = 1.0), the capacity corresponding to the above anode half reaction is 372 mA h g However, due to the low ion conductivity of the polymer electrolyte and the high interfacial impedance between it and the graphite electrode, this elegant example of electrochemical preparation of lithiated graphite is of limited practical significance. 

Figure 28. DSC trace of the reactions occurring between a fully lithiated graphitic anode and electrolyte. Anode surfaces both rinsed with DMC and unrinsed were studied. (Reproduced with permission from ref 338 (Figure i). Copyright 1998 The Electrochemical Society.)...

As discussed in the next section, lithiated carbon electrodes are covered with surface films that influence and, in some cases, determine their electrochemical behavior (in terms of stability and reversibility). They are formed during the first intercalation process of the pristine materials, and their formation involves an irreversible consumption of charge that depends on the surface area of the carbons. This irreversible loss of capacity during the first intercalation/deintercalation cycle is common to all carbonaceous materials. However, several hard, disordered carbons exhibit additional irreversibility during the first cycle, in addition to that related to surface reactions with solution species and film formation. This additional irreversibility relates to consumption of lithium at sites of the disordered carbon, from which it cannot be electrochemically removed [346-351],... 

The lithiated transition metal oxide LiVMoOe has been synthesized by solid state reaction. This is the first report of this compound to be studied as an anode material. The synthesized LiVMo06 powder has been studied by means of X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) spectroscopy. The electrochemical characteristics of the prepared electrodes assembled in coin cells were also investigated in terms of half-cell performance. It is observed that the cell exhibits three stages of discharge plateaus in the ranges 2.1-2.0 V, 0.6-0.5 V and 0.2-0.01 V, respectively. 

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