Plates and Compact Anodes

The individual weights range from less than 1 kg to several 100 kg the latter is particularly used in steel-water structures. Anodes for the external protection of ships are heavier than 40 kg only in exceptional cases. According to need, anodes are combined into groups whose total weight amounts to several hundred kilograms. 

Finally there are large plate anodes up to 1 m square with cable connections as hangers. Such anodes serve to drain stray currents in ships in fitting out or repairs (see Section 15.6). 

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A large number of commercial cells put the anode and cathode comparatively close together, but, in order to obtain reasonably high purity in the gaseous products, a porous partition is placed between the electrodes this, like inaeasing the distance between the plates, aeates a certain amount of resistance, but it has one advantage of the latter procedure in that it makes for compactness, which is very desirable in any plant and particularly so in the case of electrolytic ones, as one of the greatest objections to their use is the floor space which they occupy. 

Selection of the most perfect and reliable electrolyte-anode adjoining method based on CIP techniques was performed as follows. Anode and electrolyte layers in various conditions (press-powder, green compact, partially sintered compact, or sintered ceramics) were jointly isostatically pressed at pressure values from 0.05 to 0.8 GPa. Since the electrolyte layer should be much thinner than the anode one, such joint isostatical pressing, as a rule, had a nature of adpressing the electrolyte powder onto a pre-formed anode compact. The two-layered plate produced by such a way was sintered at 1500°C. Thereafter a cathode layer was build up in a similar manner. Alternatively the cathode layer was applied by molding a slip prepared from a mixture of the powder and alcohol. A green cathode layer on the plate was sintered at 1200°C. 

The electrolyte for the battery is a LiCl/KCl mixture with a temperature of 430—490°C. Batteries are constructed on the parallel-plate principle with alternate anodes and cathodes, and in each inter-electrode space there is a boron nitride cloth or felt separator. Commonly there is one extra negative plate because some lithium is lost during cycling. The plates, typically 5 mm thick, were initially prepared by cold compaction techniques, the active material being compressed into a fine metal lioneycomb material which also acts as the current collector. The negative electrode was just the li/Al alloy in an Fe lattice while the positive electrode was a mixture... 

From these results, we have designed chromium plating procedures which yield compact and adherent deposits. Next step is to scale up the process, and to test the use of a soluble chromium anode. 

A rotating cylinder electrode (RCE) with a cylindrical or pseudo-cylindrical counterelectrode around it essentially has the geometry of a parallel plate cell. The RCE was developed as a specialty tool for uniform fast electrodeposition in turbulent flow, and for the removal of metal ions from effluents with recovery of the metal in the form of a foil, flake, or powder [61-63]. In the first application, RCE cathodes became the major tool for silver removal from photographic fixer solutions in compact, high-rate units [64], and enabled the recycling of fixer and resale of more than 98 wt% of the silver. Typically, such cells had a stainless steel RCE cathodes of 10-20 cm diameter rotating at speeds up to 1400 rpm, stationary graphite anodes, and were operated at 50 A. 

The requirements of the small fuel cell system translate into a fuel cell stack that is compact, externally air-cooled and utilizes unconditioned ambient air as a reactant. For hydrogen-fueled systems (which are the majority to date) the anode compartments of the stack are virtually dead-ended. The need for compactness calls for internal reactant manifolding and bolting as well as thin end-plates. A representative stack for a small fuel cell system is shown in Fig. 43.3. The cell components, of course, should also be as thin as possible. 

Anode Metal anodes consisting of noncorrosive stainless steel mesh can be utilized [76], but copper is not useful due to the toxicity of even trace copper ions to bacteria. The most versatile electrode material is carbon, available as compact graphite plates, rods, or granules, as fibrous material (felt, cloth, paper, fibers, and... 

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