Electrode metal: graphite

The following chapter contains a collection of six papers specifically dedicated to the topic of metal/graphite composites as candidate active materials for the negative electrodes of the lithium-ion batteries of the near future. Editors believe this chapter to be a very first attempt made in the worldwide electrochemical literature to group metal/graphite composite lithium-ion battery developers into a stand-alone section of a book. 

METAL-GRAPHITE COMPOSITS AS MATERIALS FOR ELECTRODES OF LITHIUM-ION BATTERIES... 

A uniform monolayer surface depends upon it having been deposited on a flat electrode substrate. Impressive flatness can be achieved with the semi-metal graphite, a lamellar structure with weak van der Waals forces between the layers. A clean... 

The rotated disc electrode (RDE) is one of the most commonly employed hydro-dynamic electrodes. Figure 7.1 shows a schematic representation of a typical RDE. The electrode itself is a flat, circular disc of metal, graphite or an other conductor, and has a radius of r its area A, therefore, is straightforwardly nr. The disc is embedded centrally into one flat end of a cylinder of an insulatory material such as Teflon or epoxy resin. Behind the face of the electrode is an... 

Application of composite electrodes in the arc discharge process is a well-known route to metallofullerenes [1], To prepare electrodes, a graphite rod is used to be coaxially drilled, stuffed with mixture of metal oxide, graphite powder and thermosetting resin then annealed under vacuum at ca. 2000°C. Such procedure seems to be laborious whereas the yield of metallofullerenes is low [2]. To increase the yield, composite electrodes structure was varied [2] and new equipment was... 

These compounds resemble alkali metal-graphite compounds both in their structure and in their properties. The method used in their preparation was the result of a chance observation in the author s laboratory (80). During an investigation of electrolytic reactions in liquid ammonia a solution of sodium amide in liquid ammonia was electrolyzed with graphite electrodes, and it was found that the cathode swelled and disintegrated. Since the electrodes were not attacked in the solution when there was no electrolysis it was clear that the change could only have... 

The application of A-type GIC materials in rechargeable batteries has frequently been investigated, namely in metal/graphite cells in concentrated sulfuric acid by Fujii (Me = Pd) [153,154] and in acids of medium concentration by Beck and Krohn (Me = Pb or Zn) [155-157]. The latter electrolytes have an improved compatibility with the negative metal electrode. Metal-free accumulators with GIC as a positive electrode were built with anthraquinone in aqueous acids [80] and with polypyrrole in aprotic electrolytes [58,158,159]. General discussions of the potentialities of graphite-type active materials in rechargeable batteries have been published by Besenhard and Fritz [160] and Beck et al. [5-10]. At the end of this review (Section 9) the discussion relevant to batteries will be summarized. 

Currently, work is being conducted on an in situ electrodeposition sampling device 20, 21, 22), It consists of a submersible, self-contained potentiostat, power supply, reference electrode, and working electrode. Metals are deposited on the 1-in. diameter, wax-impregnated, pyrolytic graphite working electrode 21, 22, 23) which can then be removed from the sampler at the surface and stored. The metal film can be either... 

Carbon activities in alkali metals are also estimated by electrochemical meters. These are based on the activity differences between two carbon bearing electrodes separated by a carbon ions conducting electrolyte. The electrolyte is a molten salt mixture, consisting of the eutectic of lithium and sodium carbonate, melting at approximately 500 °C. The molten salt mixture has to be kept free from any impurities or humidity. The mixture, acting as liquid electrolyte is kept in an iron cup. The iron wall is in contact with both the liquid electrolyte and the liquid metal. Thus, it exchanges carbon with both up to the equilibrium. Iron, with the same carbon potential as the liquid metal, acts as one electrode. The reference electrode of graphite or any other material with a well defined and stable carbon activity is immersed in the molten electrolyte. The Nernst equation defines the potential of the electrochemical chain ... 

Since a wide variety of sample types is likely, it follows that sample preparation will differ markedly from one type of sample to another. Metals can be formed into self-electrodes, as previously mentioned, or into flat disks. Metal alloys may need to be remelted to obtain homogeneity and also to be formed into a suitable shape. Metal powders can be pressed into pellets and placed in cupped graphite or carbon electrodes. Metals also may be converted into ionic solutions by proper treatment with acids or other chemical agents. 

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