Lithium thermodynamic parameters

Polymers - The PS, PDMS, polyhexylisocyanate (PHIC), and polylso-prene (PI) samples had been extensively characterized to determine molecular weights, molecular sizes, and thermodynamic parameters (5, 6, 7 ). The samples were anionlcally polymerized using butyl lithium as the initiator. The pertinent data are shown in Table L Polylsobutylene/PIB polymers were obtained by fractionation of commercial polymers and their molecular weights were measured (8). 

The values of the thermodynamic parameters for the dissolution of lithium and sodium halides in water and in propylene carbonate (PC) are given in Table 2.1. 

The thermodynamic parameters characterizing the basicity of the tetrazole ring with respect to lithium cation in the gas phase have been obtained experimentally (ion cyclotron resonance) and by calculations G2, G2(MP2), B3LYP/6-31+G )) <2000PCA2824, 2004JCI1727, 2004PCA4812>. 

This compound, which is monomeric in the solid state, exists in toluene solution in equilibrium with its dimer (Scheme 2)18 as evident from analyses of variable temperature H, 7Li and 13C NMR. Whereas the monomer is favored at higher temperatures in terms of the entropy effect, the dimer is favored at lower temperatures in terms of electrostatic interactions through which electrons of the germanium negative centers are efficiently stabilized by the two lithium cations. The thermodynamic parameters for this equilibrium were estimated. 

Anani A, Crouch-Baker S, Huggins RA. Kinetic and thermodynamic parameters of several binary lithium alloy negative electrode materials at ambient temperature. J Electrochem Soc 1987 134 3098-3102. 

Barriers to rotation around the Cca —N bonds have been determined experimentally for diaminocarbenes (3) and (4) and their protonated and lithiated counterparts the possible involvement of lithium or a proton in the dimerization of these acyclic diaminocarbenes was also reported. A computational study of the dimerization of diaminocarbenes has been performed via rate constant calculations using general transition-state theory calculations. Such a dimerization has been shown to be a rapid equilibrium between the carbenes and the tetra-A-alkyl-substituted enetetramines (5), by characterization of metathesis products when two different tetramines were mixed. The thermodynamic parameters of this Wanzlick equilibrium have been determined for the A-ethyl-substituted compound the enthalpy of dissociation has been evaluated at 13.7kcalmol and the entropy at 30.4calmor K . Complex-ation of diaminocarbenes by alkali metals has been clearly established by a shift of the C NMR signal from the carbene carbon of more than 5 ppm. ... 

HF/6-31G calculations have been performed to determine thermodynamic parameters for the dissociation of dimeric associates of crotyllithium and 1-lithium-2,6-octadiene and for crotyllithium complexes of butadiene. An equilibrium constant within an order of magnitude of the experimentally determined value for the dissociation was obtained. 

Room-temperature ionic liquids (RTILs) are intrinsic ionic conductors which have been successfully employed as nonflammable/nonreactive electrolytes in a range of electrochemical devices, including dye-sensitized solar cells [1,2], lithium batteries [3], fuel cells [4], and supercapacitors [5]. The quantification of mass transport is of interest in any solvent, particularly those employed in electrochemical devices, as it affects the ultimate rate/speed at which the device can operate. The diffusivity or diffusion coefficient (D) of a redox active species, along with other thermodynamic parameters such as the bulk concentration (c) and the stoichiometric number of electrons (n) that are of fundamental significance in any study of an electrode reaction, can be determined experimentally using a range of electroanalytical techniques [6], As with any analytical method, the ideal electroanalytical technique for parameter characterization should be accurate, reproducible, selective, and robust. In many respects voltammetric methods meet these requirements, since they can be... 

Although water is used preferentially as a medium for electrode reactions, there is growing interest in the use of nonaqueous solvents. This is for several reasons first, there are compounds which exhibit very limited solubility in water. Second, some species may not be stable in aqueous media. Third, the range of available potentials, relatively narrow in water, may be wider on both the cathodic and the anodic side in an aptly chosen solvent. Also, some processes of industrial or technical importance are sometimes carried out in nonaqueous or mixed solvents. For instance, in recent years different types of batteries, especially those with lithium electrodes, have been developed and further improved. They are based on the application of nonaqueous solvents. These applications frequently result from the fact that thermodynamic and kinetic parameters of various electrode reactions are greatly affected by the reaction medium. 

The basic thermodynamic and electrochemical kinetic concepts involved in batteries and the parameters used to evaluate their performance are summarized in Section 2.2. The most widespread primary and rechargeable systems are described by highlighting the most recent advances in Section 2.3. Supercapacitors and fuel cells, whose importance in the field of energy conversion is growing, are also briefly treated in this section. The lithium-based rechargeable systems, the most advanced batteries with the highest performance, are discussed in detail in Section 2.4, with particular emphasis on the new materials on which these batteries are based. 

The GITT is one of frequent methods to investigate steady-state or equilibrium electrode potentials and diffusion coefficients as function of lithium content in a lithium intercalation electrode. The detailed experimental procedures to determine these thermodynamic and kinetic parameters have been well documented in previous studies [45]. From repeated coulombic titration processes of lithium in the electrode, by application of a constant current with a low value and sufficient time interval to reach equilibrium (i.e., to obtain uniform distribution of the lithium ions throughout the electrode), it is possible to obtain the electrode potentials at various lithium contents, as depicted in Figure 5.2. 

Finally, a brief overview was presented of important experimental approaches, including GITT, EMF-temperature measurement, EIS and PCT, for investigating lithium intercalation/deintercalation. In this way, it is possible to determine - on an experimental basis - thermodynamic properties such as electrode potential, chemical potential, enthalpy and entropy, as well as kinetic parameters such as the diffusion coefficients of lithium ion in the solid electrode. The PCT technique, when aided by computational methods, represents the most powerful tool for determining the kinetics of lithium intercalation/deintercalation when lithium transport cannot be simply explained based on a conventional, diffusion-controlled model. 

As many parameters influence the ( /Zj-ratio, it is difficult to predict the stereochemical course of a Wittig reaction. Nevertheless, some basic rules have been worked out [6,19,20]. Reactive ylides in apolar solvents such as benzene or ether preferentially form the thermodynamically less stable (Zj-isomer, in particular under so-called salt-free conditions, i.e. when no soluble lithium salts are present in the reaction mixture. In the presence of LiX, the proportion of (Fj-isomer increases in the order X = Cl>Br>I>BPh4 [20]. In polar aprotic... 

The practical electrochemical parameters (actual cell capacity, cell voltage, etc.) are strongly related to the theoretical thermodynamic calcnlalions and are usually diminished by a certain factor because of the occurrence of various real-life usage losses. The most important theoretical properties of battery materials (electrochemical potential of the cell, cell s theoretical capacity, and energy) are derived from thermodynamics of the electrode reactions in lithium-ion cell (Table 1.1). A comprehensive, in-depth discussion of thermodynamics of the processes occurring in a lithium-ion cell can be found elsewhere [4]. Some of the most crucial formulas are Usted below. 

The interest in the analysis of the dependencies of equilibrium potential on composition of cathode materials for lithium-metal cells appeared in the late-1970s [2-8] where phase composition and phase transitions of oxides and hal-cogenides of transient metals upon lithiation were discussed. The usefulness of the simultaneous scrutiny of the equilibrium potential together with its tanpera-ture coefficient was first proved in several works [9-13] published soon after. The approach to the calculation of kinetic parameters using the thermodynamic data, which is the subject of this chapter, has been proposed [14-16] later. In early 2000, new interest in the method has arisen, both in the thermodynamics of the processes within the electrodes for lithium-ion cells [17-22] and in the connection between thermodynamic functions and kinetic parameters [23]. In the series of recent works, M. Bazant [24] described the development of the fundamental theory of electrochemical kinetics and charge transfer applied to lithium iron phosphate (LFP). 

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