Electrode materials, thermal stabilizing properties

The thermal stabilizing properties of the electrode materials were foimd to be the result of reactions of the electrolyte or electrolyte decomposition products with the surface of the electrodes. Two primary mechanisms were proposed to be responsible for this stabilization. First, the electrode materials could react with the auto-catalytic species rapidly, preventing the exponential decomposition. Second, the surface species could Lewis basic species and reversibly bind the free PF5, preventing the electrolyte decomposition [32,34],... 

The early patent disclosures have claimed the application of a wide spectrum of gas-evolving ingredients and phosphorus-based organic molecules as flame retarding additives in the electrolytes. Pyrocarbonates and phosphate esters were typical examples of such compounds. The former have a strong tendency to release CO2, which hopefully could serve as both flame suppressant and SEI formation additive, while the latter represent the major candidates that have been well-known to the polymer material and fireproofing industries.The electrochemical properties of these flame retardants in lithium ion environments were not described in these disclosures, but a close correlation was established between the low flammability and low reactivity toward metallic lithium electrodes for some of these compounds. Further research published later confirmed that any reduction of flammability almost always leads to an improvement in thermal stability on a graphitic anode or metal oxide cathode. 

Metal ion modified polyimide films have been prepared to obtain materials having mechanical, electrical, optical, adhesive, and surface chemical properties different from nonmodified polyimide films. For example, the tensile modulus of metal ion modified polyimide films was increased (both at room temperature and 200 0 whereas elongation was reduced compared with the nonmodif ied polyimide (i). Although certain polyimides are )cnown to be excellent adhesives 2) lap shear strength (between titanium adherends) at elevated temperature (275 0 was increased by incorporation of tris(acetylacetonato)aluminum(III) (2). Highly conductive, reflective polyimide films containing a palladium metal surface were prepared and characterized ( ). The thermal stability of these films was reduced about 200 C, but they were useful as novel metal-filled electrodes ( ). 

Historically ceramics were exploited for their electric insulation properties, which together with their chemical and thermal stability rendered them ideal insulating materials in applications ranging from power lines to cores bearing wire-wound resistors. Today their use is much more ubiquitous — in addition to their traditional role as insulators, they are used as electrodes, catalysts, fuel cells, photoelectrodes, varistors, sensors, and substrates, among many other applications. 

There are two kinds of polymer material that used in quasi-solid/solid state DSSCs. For quasi-solid electrolytes, polyionic liquids have been proposed as solvent and redox couple as solute. They appear in molten salts and present many promising properties, such as, high chemical and thermal stability and high ionic conductivity Their main drawback is related to its high viscosity, which makes the ions diffusion rather slow. As the transport of ions to the counter electrode in an ionic liquid matrix represents a rate-limiting step in DSSC (Bella, 2015), the performance of quasi-solid electrolytes based solar cell is imsatisfled. 

The poor cycle stability and relative poor electrical conductivity of bare CPs have partially restricted their practical applications in electrode materials. On the other hand, carbon materials share the merits of low cost, high chemical and thermal stability, and high electrical and mechanical properties (Zhang and Zhao, 2009 Yan et al., 2014). Therefore, a combination of CPs with carbon materials at the molecular scale seems to be an effective strategy to improve the electrical conductivity and mechanical property of CPs. 

Liu et at fabricated the well-defined carboxylated CNTs/PPy composite hollow microspheres with near xmiform particle size of 1.4 pm via chemical oxidative interfacial polymerization of Py in the presence of the carboxylated carbon nanotubes (CNT-COOH) for the first time (Figure 8.1) [33]. It was found that the presence of the carboxylated CNTs greatly improved their morphological, thermal, and electrical conductive properties. The cycling stability as electrode materials for supercapacitors had been evidently improved by introducing the CNT-COOH, although the presence of the CNT-COOH had slightly enhanced their SC. 

Castor oil-based polyurethane resin is used to obtain graphite composite as an electrode material. The 60% graphite (w/w) composite exhibits good mechanical and appropriate electric resistance and offers ease of preparation and surface renovation. The polyurethanes of soybean oil-based polyol with glass reinforced composites exhibit mechanical properties comparable with those based on petrochemical polyol. The oxidative, thermal and hydrolytic stability of soybean oil-based composites are superior to those of petrochemical polyol. All the results indicated that a polyurethane matrix based on soybean oil is a preferable alternative to petrochemical polyurethanes in glass reinforced composites. 

Most commonly, the battery will be configured with a stack of bipolar cells (10 -100 cells per stack) to give a useful output voltage and with parallel flows for the electrolytes to each of the cells in the stack. Hence, the electrodes will be bipolar with a solid core from carbon, graphite, or a carbon/polymer composite and the three-dimensional elements bonded or pressed onto either side of the solid core. The composites are a blend of a chemically stable polymer and a micron-scaled carbon powder, most commonly an activated carbon Radford et al. [127] have considered the influence of the source of the carbon and the chemical and thermal treatments on the properties of such activated carbons, especially the pore size and distribution [126]. Even though reticulated vitreous carbon has been used for the three-dimensional elements [117], the predominant materials are graphite cloths or felts with a thickness of up to 5 mm, and it is clear that such layers are essential to scale the current density and thereby achieve an acceptable power density. Details of electrode performance in the more developed flow batteries are not available but, for example, Skyllas-Kazacos et al. [124] have tabulated an overview of the development of the all vanadium redox flow battery that includes the electrode materials and the chemical and thermal treatments used to enhance activity and stability. 

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