Electrode binders

The specification requirements for electrode binder pitch, eg, high C/H ratio, high coking value, and high P-resin content, effectively ruled out pitches from gasworks or low temperature tars. The cmde tar is distilled to a medium-soft pitch residue and then hardened by heating for several hours at 385—400°C. This treatment increases the toluene-insoluble content and produces only a slight increase in the quinoline-insoluble (Ql) material, the latter by the formation of mesophase. 

The demand for electrode binder pitch has grown as aluminium output has expanded and the requirement for aluminium smelting is now between 1.5 and 2 x 10 t /yr. In Japan pitch is used for mixing with coal for carbonization in coke ovens to make metallurgical coke. 

Nonmetal electrodes are most often fabricated by pressing or rolling of the solid in the form of fine powder. For mechanical integrity of the electrodes, binders are added to the active mass. For higher electronic conductivity of the electrode and a better current distribution, conducting fillers are added (carbon black, graphite, metal powders). Electrodes of this type are porous and have a relatively high specific surface area. The porosity facilitates access of dissolved reactants (H+ or OH ions and others) to the inner electrode layers. 

Production of Electrode Binder Pitch from Petroleum-Based Materials... 

A patented process has been developed for the production of electrode binder pitch from petroleum-based materials. Carbon anodes produced from the petroleum-based pitch and coke have been used successfully on a commercial scale by the aluminum industry. One stage of the process involves the pyrolysis of a highly aromatic petroleum feedstock. To study the pyrolysis stage of the process a small, sealed tube reactor was used to pyrolyze samples of feedstock. The progress of the reaction is discussed in terms of the formation of condensed aromatic structures, defined by selective solvent extraction of the reaction product. The pyrolysis of the feedstock exhibits a temperature-dependent induction period followed by reaction sequences that can be described by first-order kinetics. Rate constants and activation energies are derived for the formation of condensed aromatic structures and coke. 

Gulf Canada has been active in this area for sometime and recently has developed a process that produces a high quality electrode binder pitch from a petroleum-based feedstock (7). This pitch has been used on a commercial scale by the aluminum industry in both vertical stud Soderberg and prebaked electrodes. 

Recovery and Analysis of Pyrolysis Products. Frequently the quality of electrode binder pitches is assessed partially on the basis of how much material they contain that is insoluble in benzene (BI) and quinoline (QI) (8,9,10). In addition, the pyrolysis and coking of... 

The use of a perfluorinated ionomer as the SPE electrode binder results in better adhesive bonding with the membrane by virtue of the fact that the binder and the membrane are of identical composition. In addition, the solvent in the electrode paste promotes "solvent welding" by softening the membrane during the application process. 

Coke-oven tars contain only minor quantities of nonaromatic hydrocarbons, while the vertical retort tars may have up to 6% of paraffinic compounds. Low-temperature tars are more paraffinic and phenolic (as might be expected from relative lack of secondary reactions) than are the continu-ons vertical retort tars. Coke-oven tars are comparatively rich in naphthalene and anthracene, and distillation is often the means by which various chemicals can be recovered from these particular products. On the other hand, another objective of primary distillation is to obtain a pitch or refined-tar residue of the desired softening point If the main outlet for the jMtch is as a briquetting (Chapter 17) or electrode binder, primary distillation is aimed at achieving a medium-soft pitch as product or for the production of road tar/asphalt (Yan, 1986). 

An electrode binder for lithium-ion (Li-Ion) secondary batteries is used either to bind active material layers or between active material layers and collectors. The binder in general is preferably electrochemically inert. Although the binder is not essential for the battery, it has an important role in the facilitation of producing batteries and in their properties. Therefore, the binder is said to be one of the major elements of the battery. 

The electrochemical production of aluminum utilizes pre-baked or Soderberg anodes. Pre-baked anodes are manufactured by mixing petroleum or pitch coke with around 20% of electrode binder (see Chapter 13.1.2), followed by molding, as is also usual for the production of graphite electrodes. The green electrodes are baked in a ring furnace at a temperature of 1200 °C. 

Chen ZH, Christensen L, Dahn JR (2004) Mechanical and electrical properties of poly (vinylidene fluoride-tetrafiuoroethylene-propylene)/super-S carbon black swelled in liquid solvent as an electrode binder for lithium-ion batteries. J Appl Polym Sci 91 2958-2965... 

PEM EC and electrolysis PFSA Membrane Electrode binder Electrochemical resistance Proton conductivity Electrochemical resistance Adhesion properties... 

Homogeneous distribution of electrode binder and other additives... 

Spotnitz et al. DSC, ARC Cathode, electrolyte, SEI, Lithium salt These kinetic parametras can be used to simulate DSC and ARC experiments. The simulations indicate that the negative electrode binder plays a relatively unimportant role in thcamal runaway. [27] g OQ P... 

We would like to make one last but important comment. With aU the new membranes, the current MEA technology that uses a Nation ionomer as an electrode binder should be optimized for new electrolyte and DMFC systems. Novel MEA processes for new electrolytes will reduce the interfacial resistance of membranes and electrodes. Although conventional membranes, such as Nafion, have an elastomeric property and low glass transition temperature, methanol-impermeable membranes have some degree of rigidity. Thus, the adhesion process has to be optimized so that those efforts of membrane development can maximize MEA performance. 

The latest patent application comes from researchers representing Toyota and Case Western Reserve University [53]. The invention describes the use of multiaromatic ring-sulfonated polyphosphazenes as fuel-cell electrode binders. 

Various workers have studied electrol5des made by blending ionic liquids with solvents [3536,43,51,61-63], polymer electrolytes [26,48303538,64-68], polymers as electrode binders [21,4833,69] and ionomers whereby elements of the ionic liquids are incorporated into the pol)rmer backbone [70-75]. Such work has opened up new fields for these materials and simultaneously blurred the distinctions among ionic liquids, and rubber, glassy, gel, ionomer and polymer electrolytes. This is exemplified by a complex scheme in a review by AngeU [26]. hi this chapter, we have included such materials only when the salt forms the major component of the electrolyte, such as polymer-in-a-salt electrolytes or PISE [76,77]. 

For liquid-based systems, the present state-of-the-art for commercial Li-ion batteries almost universally employs either PVDF homopolymers or PVDF-HFP copolymers for electrode binders and, in some cases, for the electrolyte separator-matrix [52]. These polymers are most effective for commercial processing of composite electrodes on current collector metal foils such as Cu and Al, and... 

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