Metal-air batteries and

Oxygen reduction electrodes, where molecular oxygen is electrocatalytically reduced, are vital to metal/air batteries and fuel cells. Recently, noble metals such as platinum have played a dominating role as... 

Problems of the metal-air batteries and air electrode are considered. Results of research, design work and development of the air - Zn primary and air-Al mechanically rechargeable batteries, as well as electrically rechargeable electrodes are presented. 

Some theoretical prerequisites for application of modified and expanded graphites, Si- and Sn-based composites and alloys, electroconducting polymers as active materials, catalysts and electro-conductive additives for lithium - ion batteries, metal-air batteries and electrochemical capacitors are considered. The models and the main concepts of battery-related use for such materials are proposed. 

In this chapter we present an overview of the state of the art and short-term perspectives of fuel cells and metal/air batteries and analyse their environmental benefits emd drawbacks. 

Shortly after Grove s work on fuel cells in 1839, Smee in 1840 introduced the original concept of the metal air batteries and the last 150 years have seen discontinuous developments in the metal air batteries. The zinc/air battery had been prominent but generally unsuccessful due to both problems in the rechargeability of the zinc electrode as well as problems with the gas electrodes. 

Such systems are called metal-air batteries and are mechanically rechargeable (anode metal is replaced). Such batteries have only recently become practicable due to the developments of the O2 - electrode in fuel cells. Some characteristics of selected metal-air batteries are given in Table 9.6. 

The manufacturing process can be done using modified paper-making machines, at quite low cost. Such electrodes are not just used in fuel cells but are also used in metal/air batteries, for which the cathode reaction is much the same as for an alkali fuel cell. For example, the same electrode can be used as the cathode in a zinc air battery (e.g. for hearing aids), an aluminium/air battery (e.g. for telecommunications reserve power), and an alkaline electrolyte fuel cell. The carbon-supported catalyst is of the same structure as that shown in Figure 4.6 in the previous chapter. However, the catalyst will not always be platinum. For example, manganese can be used for the cathode in metal air batteries and fuel cells. 

The future of catalysts in metal-air batteries is very exciting and interesting. As the world increases its demand for energy storage, metal-air batteries and the catalysts, they depend upon, will gain interest. Metal-air batteries that use oxygen from the air to produce electricity are interesting in themselves. Hopefully new catalysts will be developed to improve these batteries. 

There are several types of catalytic batteries that include (but are not limited by) metal/air, nickel/hydrogen, and lithium/thionyl chloride batteries. Air cathode in metal/air batteries and hydrogen anode in nickel/hydrogen batteries are similar to those in PEMFCs, excluding complexity of air and water management at the PEMFC cathodes. Unlike traditional batteries. 

FIGURE 4.14 Models of the reaction zones for the ORR. (a) a "triple phase boundary" for aqueous electrolyte metal-air battery and PEMFC and (b) a "two-phase boimdary" for non-aqueous electrolyte Li-air battery. Reprinted from Ref. [170], with permission from Elsevier. 

Catalysts are an important part of metal-air batteries and have been investigated for use in lithium-thionyl chloride cells also. Metal-air batteries are very similar to fuel cells and have been called fuel cell-battery hybrids because one of the electroactive materials, oxygen, does not require storage. 

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