Practical batteries, specific energy

Li—Al/FeS cells have demonstrated good performance under EV driving profiles and have deUvered a specific energy of 115 Wh/kg for advanced cell designs. Cycle life expectancy for these cells is projected to be about 400 deep discharge cycles (63). This system shows considerable promise for use as a practical EV battery. 

Specific energy, which could be attained as primary battery is of about 140 W-h/kg for Air/PANI-Zn and 200 W-h/kg for Air/PANI-Mg batteries. The discharge curves of such batteries is practically horizontal since there are determined by the oxygen reduction potential. 

The first practical silver—zinc battery was developed more then 60 years ago. Since then, primary and secondary silver—zinc batteries have attracted a variety of applications due to their high specific energy, proven reliability and safety, and the highest power output per unit weight and volume of all commercially available batteries. However, they find very limited use in commercial applications, because of their high price and limited cycle life. Development of a battery separator which will improve the performance and life of zinc based alkaline cells has been... 

Figure 4 shows a comparison of practical energy density and specific energy of primary batteries. Two groups can be distinguished the zinc-based and lithium-based systems. 

Figure 6. Practical energy density and specific energy of various rechargeable batteries.

The lead—acid battery could be adequately evaluated only if compared to the other types of secondary power sources. A theoretical assessment can be made by comparing the electrical, energetic, power and economic parameters of the different sources of electricity, but the relative share of each battery chemistry in practical applications is the most objective evaluation criterion. Table 1.1 summarises the basic energy and power characteristics of six types of secondary power sources which are currently used most widely. Data from the studies of Wentzl [78] and Kohler [79] have been used. It can be seen that the lead—acid battery has inferior specific energy and power characteristics as compared to the other types of batteries. 

The theoretical specific energy is never delivered in practical cells. To transform the lead—acid cell into a practical power source, several design requirements must he met. Figure 2.51 shows the construction of a conventional SLI battery [123]. 

This type of calculation can be useful as a means of comparing the theoretical specific energies of different batteries. Practical energy densities are design dependent and typically deliver no more than 20-40% of the theoretical specific energy. 

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