Intercalation-deintercalation reaction

Electrons participating in the intercalation/deintercalation reaction (Equation (5.1)) can be represented by a current-producing system. Second, it is characteristic that the current-producing system reversibly operated by a self-driven (galvanic) cell (discharging the battery) performs the electrical useful work AG = —zFE (where E is the EMF of the cell), because electrical potential difference is spontaneously developed between two electrodes. By contrast, when the cell is short-circuited - that is, when the two electrodes are not separated from each other but are directly in electrical contact - electrons do not appear explicitly but rather participate in corrosion (or permeation in the case of solid electrolyte cells). They perform no electrical useful work because the two electrodes have the same electrical potential. 

Actnally, these redox couples have been used as central metals of the polyanionic cathodes in recent years, as shown in Table 9.2. It can be expected that the three-dimensional framework of the oxygen-closed pack framework is sufficiently stable to tolerate repeated lithium intercalation/deintercalation reaction, because it does not inclnded weak van der Waals bonding in the matrix. 

Lithium ion can be intercalated, more or less, into most kinds of carbon, and the resulting lithiated carbons show extremely negative electrochemical potentials close to that of the metallic lithium electrode. The reversible intercalation/deintercalation reactions overcome the problem of dendrite formation of lithium and provide dramatic improvements in safety and cycleability. The carbon anodes are combined with non-aqueous electrolyte solutions and lithium-transition metal oxides such as LiCoOg as cathodes to fabricate 4 V-class LIBs. Only lithium ion moves back and forth between the cathode and the anode upon charging and discharging, which give rise to a potential difference of about 4 V between the two electrodes. The name, "lithium-ion" batteries came from this simple mechanism. 

The striking example is the reactivity of lithium with IE-VI layered compounds such as the decomposition of Li intercalated InSe with the formation of lithium selenide, Li2Se, observed by Raman spectroscopy on specimens prepared by various intercalation methods. The insertion of Li into M0S2 appears more stable with the occurrence of a superlattice formation at x(Li) 0.25 but a structural transformation from 2H-M0S2 (P-phase) to IT-M0S2 (a-phase) occurs for x l. This process is irreversible but the intercalation-deintercalation reaction is possible with the IT-M0S2, which could act as a positive electrode in rechargeable lithium batteries after formation of the cells. 

This may lead to the irreversible changes in the material, caused by partial oxidation of graphite, loss of reversibility of the system along with the efficiency of reaction for intercalation-deintercalation (1). 

Chemical relaxation methods can be used to determine mechanisms of reactions of ions at the mineral/water interface. In this paper, a review of chemical relaxation studies of adsorption/desorption kinetics of inorganic ions at the metal oxide/aqueous interface is presented. Plausible mechanisms based on the triple layer surface complexation model are discussed. Relaxation kinetic studies of the intercalation/ deintercalation of organic and inorganic ions in layered, cage-structured, and channel-structured minerals are also reviewed. In the intercalation studies, plausible mechanisms based on ion-exchange and adsorption/desorption reactions are presented steric and chemical properties of the solute and interlayered compounds are shown to influence the reaction rates. We also discuss the elementary reaction steps which are important in the stereoselective and reactive properties of interlayered compounds. 

The fast reactions of ions between aqueous and mineral phases have been studied extensively in a variety of fields including colloidal chemistry, geochemistry, environmental engineering, soil science, and catalysis (1-6). Various experimental approaches and techniques have been utilized to address the questions of interest in any given field as this volume exemplifies. Recently, chemical relaxation techniques have been applied to study the kinetics of interaction of ions with minerals in aqueous suspension (2). These methods allow mechanistic information to be obtained for elementary processes which occur rapidly, e.g., for processes which occur within seconds to as fast as nanoseconds (j0. Many important phenomena can be studied including adsorption/desorption reactions of ions at electri fied interfaces and intercalation/deintercalation of ions with minerals having unique interlayer structure. 

Experiments were performed with various LiAl-X LDHs, with X = Br, NO3 and ISO4. As with the intercalation process, the nature of the anion exerts a powerful influence on the reaction. In the case of sulfate, the deintercalation reaction does not go to completion - only 40% of the available lithium sulfate was released. The deintercalation reaction initially proceeds very quickly, but the process is then halted. The rate of deintercalation is NOs" > Cl > Br . This series does not correspond with data on the anion selectivity for intercalation into Al(OH)3, which is S04 > Cl" > Br" > NO3". Neither is there a correlation of the release data with the heats of hydration of the anions. The series observed arises because the intercalation and deintercalation processes are a balance of a number of factors, including interactions between the guest ions and the host matrix. 

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 particle size of the cathode material plays a very important role in their electrochemical behavior [113]. Smaller particles provide the performance of the heterogeneous reaction of intercalation/deintercalation in the kinetic regime. One of the problem is to enhance electronic conductivity of cathode materials. In this case, electronic additives (e.g., carbon) could be excluded. 

When cationic guest atoms such as lithium, hydrogen, and sodium reversibly enter or leave the host oxide crystal, along with an accompanying electron flow but without any change in crystal structure, the reaction is referred to as intercalation/ deintercalation as follows [1, 2] ... 

The change of guest atom composition in the matrix atom is accompanied by an intercalation reaction within the same crystal structure of the matrix atom. The characteristic feature of intercalation/deintercalation is, first, that the reaction proceeds not only at the interface between electrolyte and host intercalation compound electrode but also even in the interior of the electrode. 

Consider an electrochemical cell with a solid host MO2 as one electrode, an alkali metal A as the other electrode, and an electrolyte in which the monovalent cation A + is dissolved. The intercalation/deintercalation between the host MO2 and the guest ion A is given by Equation (5.1). On the other hand, the redox reaction between A and A may be written as... 

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