Plastic-bonded plate electrodes

Industrial Ni-Cd batteries are rugged, long-life, cheap batteries capable of operating at high rates. The so-called pocket-plate battery can stand overcharge, polarity reversal and short-circuits. To better utilize the electrode materials, two other structures have been developed the fiber plate and the plastic-bonded plate. The latter has afforded improved performance characteristics (e.g. an energy density of 110 Wh/1). 

Union Carbide Corp. (UCC) developed AFCs for terrestrial mobile applications starting in the late 1950s, lasting until the early 1970s. UCC systems used liquid caustic electrolytes the electrodes were either pitch-bonded carbon plates or plastic-bonded carbon electrodes with a nickel current collector. UCC also built fuel cell systems for the U.S. Army and the U.S. Navy, an alkaline direct hydrazine powered motorcycle, and the Electrovan of General Motors. Finally, Professor Karl V. Kordesch built his Austin A-40 car, fitted with UCC fuel cells with lead acid batteries as hybrid. It was demonstrated on public roads for three years. The years of research and development are very well summarized in reference (5) Brennstofflyatterien. 

A more recent design that has shown significantly improved performance characteristics is the plastic-bonded or pressed-plate electrode. This new development of electrode materials in industrial batteries is a spin-off from the development of electrode materials for use in aircraft and sealed portable consumer batteries. In the plastic-bonded plate, which is mainly used in the cadmium electrode, the active material cadmium oxide is mixed with a plastic powder, normally PTFE, and a solvent to produce a paste. The paste is isotropic and the materials are manufactured at the final density for the active material. As a result, dust problems are eliminated during manufacturing. The paste is extruded, rolled, or pasted onto a center current collector normally made of nickel-plated perforated steel. The plate stmcture is welded to nickel-plated steel tabs. 

Pocket and tubular electrodes have been described in detail by Falk and Salkind [1]. McBreen has reviewed work on both sintered plate and plastic-bonded electrode technology [9], More recent work is on the use of nickel foams and nickel mats. 

During the past 10 years the nickel film plate based on polypropylene felt has been introduced and has led to an improvement in performance. Plastic or rubber bonded plates have also been introduced. The use of Teflon bonded plates as a replacement for pocket electrodes has not fulfilled its earlier promise due to problems associated with swelling of the positive electrode. 

Yusaza, Japan, have been developing prototype batteries for electric vehicle applications, claiming 200 maintenance-free cycles at 100% depth of diseharge. The more successful, but still unsatisfactory, batteries such as these are based on the use of PTFE bonded pressed plate zinc electrodes and sintered, plastic bonded pressed plate or fibre or expanded foam nickel electrodes to improve conductance. 

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