Additives for Cathodes

In this section, additives for cathodes are reported by categorizing them into (1) sulfur-containing compounds with active site poisoning function [105-107] and (2) aromatic compounds forming an electro-conducting membrane (ECM) [2,109,110]. 

1 Sulfur-Containing Compounds with Active Site Poisoning Function 

In 1998, Ube Industries, Ltd. discovered that compounds such as methyl oxo(phenylthio)acetate (83), S,S -diphenyl dithiooxalate (84), S-phenyl 0-methyl thiocarbonate (85), and 5,S -diphenyl dithiocarbonate (86) can be used as additives in small quantities [106], 

In 1998, that company found that disulhdes such as diphenyl disulfide (87) and di-p-tolyl disnlfide (88) can be nsed as additives in small qnantities [107]. 

Moreover, in 1999, the same company fonnd that bis(4-methoxyphenyl) disulfide (89) can be nsed as an additive in small qnantities [108]. 

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New York and by Amine from Argonne National Laboratory [30]. Consequently, the concept of controlling the cathode surface with additives for cathodes which further improve the life-span and increase the voltage of the battery [1, 31-33] is presented later in Sect. 3.3. 

Abe, K. Ushigoe, Y. Yoshitake H. Yoshio, M., Functional electrolytes Novel type additives for cathode materials, providing high cycleability performance, J. Power Sources, 2006,153 (2), 328-335. 

Chitosan with abundant hydroxyl and amine groups as an additive for cathodes and separators has been proven to be an effective polysulfide trapping agent in lithium-sulfur batteries (101). 

Corrosion. Anticorrosion measures have become standard ia pipeline desiga, coastmctioa, and maintenance ia the oil and gas iadustries the principal measures are appHcation of corrosion-preventive coatings and cathodic protection for exterior protection and chemical additives for iaterior protectioa. Pipe for pipelines may be bought with a variety of coatiags, such as tar, fiber glass, felt and heavy paper, epoxy, polyethylene, etc, either pre-apphed or coated and wrapped on the job with special machines as the pipe is lowered iato the treach. An electric detector is used to determine if a coatiag gap (hoHday) exists bare spots are coated before the pipe is laid (see Corrosion and corrosion control). 

The conductivity of the soil i important as it is evident from the electrochemical mechanism of corrosion that this can be rate-controlling a high conductivity will be conducive of a high corrosion rate. In addition the conductivity of the soil is. important for stray-currenit corrosion (see Section 10.5), and for cathodic protection (Chapter 10). 

The potentiostat has supplied an experimental tool for the study of anodic protection. The elucidation of passive behaviour made possible by poten-tiostatic anode polarisation curves allowed investigators to determine the conditions necessary for maintaining a metal in a stable passive condition by provision of a suitable environment, addition of cathodic alloying elementsand/or maintenance of the required potential by means of external anodic polarisation - . ... 

When the current is anodic, component Red is consumed and the equilibrium in the electrolyte close to the surface is disturbed reaction (13.37) will start to proceed from left to right, producing additional amounts of species Red. In this case the chemical precedes the electrochemical reaction. However, when the current is cathodic, substance Red is produced and the chemical reaction (13.37), now as a subsequent reaction, will occur from right to left. When component Ox rather than component Red is involved in the chemical reaction, this reaction will be the preceding reaction for cathodic currents, but otherwise all the results to be reported below remain valid. 

Just a trace of such a metallic impurity may make the CNTs not useful as additive for campsite/hybrid cathodes of LIBs. 

A typical counter electrode reaction is the electrolysis of water. Here the cathodic evolution of hydrogen is coupled with the formation of base, the anodic development of oxygen produces acid additionally. Frequently, acid and base formation at both electrodes will be balanced. Otherwise, a buffer solution or a (continuous) base/acid addition, for example, by a pH-controlling system, can enable the application of an undivided cell. 

Hence, the presence of trace impurities, which either pre-exist in pristine electrode and bulk electrolyte or are introduced during the handling of the sample, could profoundly affect the spectroscopic images obtained after or during certain electrochemical experiments. This complication due to the impurities is especially serious when ex situ analytic means were employed, with moisture as the main perpetrator. For cathode/electrolyte interfaces, an additional complication comes from the structural degradation of the active mass, especially when over-delithiation occurs, wherein the decomposition of electrolyte components is so closely entangled with the phase transition of the active mass that differentiation is impossible. In such cases, caution should always be exercised when interpreting the conclusions presented. 

Unlike the anode-targeted additives discussed in the preceding part, the additives intended for cathode protection have a much longer history than lithium ion technology itself and were originally developed for rechargeable cells based on lithium metal anodes and various 3.0 V class cathode materials. 

The cathode materials used have to conduct both oxide ions and electrons satisfactorily, but, in addition, for compatibility, they must have similar thermal expansion coefficients as the electrolyte. The strontium-doped perovskite, LSM (see Section 5.4.2), is one of the materials of choice. 

The chemistry of electrochemical reaction mechanisms is the most hampered and therefore most in need of catalytic acceleration. Therefore, we understand that electrochemical catalysis does not, in principle, differ much fundamentally and mechanistically from chemical catalysis. In addition, apart from the fact that charge-transfer rates and electrosorption equilibria do depend exponentially on electrode potential—a fact that has no comparable counterpart in chemical heterogeneous catalysis—in many cases electrocatalysis and catalysis of electrochemical and chemical oxidation or reduction processes follow very similar if not the same pathways. For instance as electrochemical hydrogen oxidation and generation is coupled to the chemical splitting of the H2 molecule or its formation from adsorbed hydrogen atoms, respectively, electrocatalysts for cathodic hydrogen evolution—... 

Industrial silver-activated zinc sulfide phosphors use the intense blue emission exclusively. The ZnS Ag phosphor for cathode ray tubes is obtained by firing zinc sulfide and silver nitrate at ca. 1000 °C in the presence of sodium chloride (coactivator Cl-) [5.318]. The afterglow can be further reduced by addition of 10-3-10-4% of nickel ions. 

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