The electrode-electrolyte interphase

This imbalance of electroneutrality and creation of field should not be confused with that arising from the presence of the electrode, which causes an anisotropy in the forces on the particles in the electrode-electrolyte interphase region. That anisotropy also produces an unbalance of electroneutrahty and an electric double layer (Chapter 6) with a field across the interface, but it occurs only within the first few tens of nanometers of the surface. 

THE ELECTRODE/ELECTROLYTE INTERPHASE OF ELECTRONICALLY CONDUCTING POLYPYRROLE... 

As part of an overall study of the electrode/electrolyte interphase of the electronically conducting polymer, polypyrrole, the surface structure and electronic properties have been investigated. 

Techniques are described which obtain the IR absorption spectra of species, either adsorbed or free In the electrode/electrolyte solution Interphase. Applications slanted towards topics relevant to electrocatalytic processes are discussed to Illustrate the capabilities of the methods In probing molecular structure, orientation and Interactions. 

In principle, therefore, these valuable techniques can provide all of the information needed to specify the molecular structure of the electrode/electrolyte solution interphase, the dynamics of adsorption/... 

No "Jilt has so far been assumed that the semiconductor-electrolyte interphase does not contain either ions adsorbed specifically from the electrolyte or electrons corresponding to an additional system of electron levels. These surface states of electrons are formed either through adsorption (the Shockley levels) or through defects in the crystal lattice of the semiconductor (the Tamm levels). In this case—analogously as for specific adsorption on metal electrodes—three capacitors in series cannot be used to characterize the semiconductor-electrolyte interphase system and Eq. (4.5.6) must include a term describing the potential difference for surface states. 

Besides staging, the other important characteristic of the graphite negative electrode is the formation of the solid electrolyte interphase (SEI) during the first cycles [7, 8], The SEI comes mainly from surface reactions... 

We have seen in Section 5.2 that one can determine the relative electrode potential by measuring cell voltage. To form a series of relative electrode potentials, one has to select a reference electrode and standard conditions of components of an electrode/ electrolyte interphase. 

When charges are separated, a potential difference develops across the interface. The electrical forces that operate between the metal and the solution constitute the electrical field across the electrode/electrolyte phase boundary. It will be seen that although the potential differences across the interface are not large ( 1 V), the dimensions of the interphase region are very small (—0.1) and thus the field strength (gradient of potential) is enormous—it is on the order of 10 V cm. The effect of this enormous field at the electrode/electrolyte interface is, in a sense, the essence of electrochemistry. 

The surface tension was stated (Section 6.4.5), on general grounds, to be related to the surface excess of species in the interphase. The surface excess in turn represents in some way the structure of the interface. It follows therefore that electrocapillaiy curves must contain many interesting messages about the double layer at the electrode/ electrolyte interface. To understand such messages, one must learn to decode the electrocapillary data. It is necessary to derive quantitative relations among surface tension, excess charge on the metal, cell potential, surface excess, and solution composition. 

When the anode is first charged, it slowly approaches the lithium potential and begins to react with the electrolyte to form a film on the surface of the electrode. This film is composed of products resulting from the reduction reactions of the anode with the electrolyte. This film is called the solid electrolyte interphase (SEI) layer [30], Proper formation of the SEI layer is essential to good performance [31-34], A low surface area is desirable for all anode materials to minimize the first charge related to the formation of SEI layer. Since the lithium in the cell comes from the lithium in the active cathode materials, any loss by formation of the SEI layer lowers the cell capacity. As a result, preferred anode materials are those with a low Brunauer, Emmett, and Teller (BET) surface area... 

Porous and nanocrystalline semiconductor electrodes have unusual properties because the semiconductor/electrolyte interphase is three-dimensional. The Helmholtz electrical double layer can extend throughout the... 

The thermodynamics of 2D Meads overlayers on ideally polarizable foreign substrates can be relatively simply described following the interphase concept proposed by Guggenheim [3.212, 3.213] and later applied on Me UPD systems by Schmidt [3.54] as shown in Section 8.2. A phase scheme of the electrode-electrolyte interface is given in Fig. 8.1. Thermodynamically, the chemical potential of Meads is given by eq. (8.14) as a result of a formal equilibrium between Meads and its ionized form Me in the interphase (IP). The interphase equilibrium is quantitatively described by the Gibbs adsorption isotherm, eq. (8.18). In the presence of an excess of supporting electrolyte KX, i.e., c , the chemical potential is constant and... 

Bewick, A. (1983) In sim infrared-spectroscopy of the electrode electrolyte solution interphase. Journal of Electroanalytical Chemistry, 150, 481-493. 

These surface films passivate the electrode, and thus further reduction of most of the solution species is inhibited. Therefore, in contrast to TAA-based solutions, there is no bulk solution reduction. At this stage, the cathodic potential limit becomes Li deposition at 0. V lAllA. This process is not inhibited by the surface films because most of these surface films are good Li ion conductors (as described by the solid electrolyte interphase model for Li electrodes in these solutions [27]). 

Thus the conformational behavior of proteins at the electrode-electrolyte interface is presumably determined by the properties of this boundary surface tension, charge, hydrophobicity, and chemidal structure. It is to be remembered, however, that the above picture presents only a qualitative character, because results of direct structural (for instance, spectral) investigations into protein conformation at the interphase boundary are not available. 

The absolute value of the potential difference across an electrode-electrolyte interphase cannot be measured since each attempt to do that will introduce a new electrode-electrolyte interphase. A reference electrode - by convention the normal hydrogen electrode (NHE) - is used to make relative measurements possible. 

McAdams, E.T., Jossinet, J., 1994. The detection of the onset of electrode-electrolyte interphase impedance nonlinearity a theoretical study. IEEE Trans. Biomed. Eng. 41 (5), 498—500. 

A. Xiao, L. Yang, B. L. Lucht, S.-H. Kang, D. P. Abraham, J. Electrochem. Soc. 2009, 156, A318-A327. Examining the solid electrolyte interphase on binder-free graphite electrodes. 

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