Electronic conductive material

Most battery electrodes are porous stmctures in which an interconnected matrix of soHd particles, consisting of both nonconductive and electronically conductive materials, is filled with electrolyte. When the active mass is nonconducting, conductive materials, usually carbon or metallic powders, are added to provide electronic contact to the active mass. The soHds occupy 50% to 70% of the volume of a typical porous battery electrode. Most battery electrode stmctures do not have a well defined planar surface but have a complex surface extending throughout the volume of the porous electrode. MacroscopicaHy, the porous electrode behaves as a homogeneous unit. 

This problem can in many cases be overcome by dispersing the active phase on an electronically conductive material (Fig. 12.1). There have been already at least three experimental studies,7 1215 surveyed here and demonstrating this concept. 

Figure 12.1, Principle of electrochemical promotion of a finely dispersed catalyst deposited on an electronically conductive material.7,li 15...

The second type of solar cell is based on a /m-heterojunction in analogy to semiconductor devices [274]. Excitons generated by light, diffuse and dissociate at the interface between a hole and an electron-conducting material. The optimum layer thickness was calculated to be 1.5 times the exciton diffusion length [275]. 

Liquid-solid contact Liquid-liquid contact Statistical distribution due to ion concentration fluctuations Double layer (zeta potential) disruption Volta potential (for electron conducting materials) Electrolytic (galvanic) potential (for ionic systems)... 

Fig. 8.4 Chemical diffusion coefficient as a function of temperature for various predominantly electronically conducting materials. For comparison the diffusion coefficients of Cu in liquid Cu and of O2 in air are shown.

As noted above, the lithium ions flow through the electrolyte whereas the electrons generated from the reaction, Li = Li+ + e, go through the external circuit to do work. Thus, the electrode system must allow for the flow of both lithium ions and electrons. That is, it must be both a good ionic conductor and an electronic conductor. As discussed below, many electrochemically active materials are not good electronic conductors, so it is necessary to add an electronically conductive material such as carbon... 

The many varieties of practical nickel electrodes can be divided into two main categories. In the first, the active nickelous hydroxide is prepared in a separate chemical reactor and is subsequently blended, admixed, or layered with an electronically conductive material. This active material mixture is... 

Organic and polymeric semiconductive materials also show a strong ER effect. They are generally electronic conductive materials with a rr-conjugated bond structure. It is believed that they have better dispersing ability compared to inorganic materials. However, the ER effect of organic and polymeric ER fluids is relatively weak compared to that of aluminosilicate materials. 

To get relevant information about active materials, the working electrode is made as similar as possible to the electrode of an operational device. However, current collectors are usually made with corrosion resistant materials, with good electronic conductivity, and no concern is taken about its relative mass. Materials such as gold, platinum, and vitreous carbon are commonly used. The active mass is usually tested in small amounts, mixed with electronically conducting materials, such as acetylene black, and a binder, such as poly vinylidene fluoride PVDF or polytetrafluoroethylene. The working electrode may be flat, with a 1 cm2 surface, for example, a rotating disk electrode (RDE), or a microcavity electrode, or any geometrical convenient electrode. 

The Fermi energy or Fermi level, Ef, of a solid is that energy at which the probability of electronic energy level occupancy is exactly 0.5. Chemically, the Fermi energy corresponds to the electrochemical potential of electrons in the solid. At equilibrium, all electronically conducting materials in contact have the same Fermi energy. 

Electrocatalytic electrode — An electrode at which an electrochemical process is subject to catalysis, i.e., in most cases its rate is increased [i, ii]. Strictly speaking the electron-conducting material (or hole-... 

The largest series of electronically conducting materials are the phosphate tungsten bronzes. These have similar properties to oxides bronzes such as Na WOs (see Oxides Solid-state Chemistry) and are strongly colored metals or semiconductors. They are formed by inserting planes of... 

Along the Y direction, i.e., the surface of the electronic conducting material, the reaction limiting step is mobile ionic reactant (A" ") transport in the product phase (D). No perceptible open circuit emf will be expected over the growth distance, and charged species are driven by the concentration gradient. The growth distance, y, can be expressed as ... 

Abstract Liquid-crystalline (LC) polymers that exhibit ionic or electronic conduction are described. Anisotropic and efficient transportation of electrons and ions is expected for these materials. The ordered LC nanostructures of LC polymers having ion- or electron-active moieties are important for efficient anisotropic transport. For electron-conductive materials, we focus on side-chain LC polymers. 

Liquid-crystalline nanostructures formed by polymeric materials have great potential to be applied for ion- and electron-conducting materials because efficient and low-dimensional conduction can be achieved in nano-segregated LC phases. Recent progress in supramolecular chemistry and nanotechnology enables the design of new materials for ion conductors. Nematic LC poly-... 

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