Specific Energy of Batteries

System Voltage (V) Specific Energy (Wh 1 - ) Energy Density (Wh L ) Power Density Specific Energy of Cell (Wh kg- ) Specific Energy of Battery (100% SOC) (Wh kg- )... 

FIGURE 1.4 Theoretical and actual specific energy of battery systems. 

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. 

This distribution causes a problem the best-described conducting polymers interchange anions with the electrolyte, and the Li electrode liberates Li+during discharge. The salt accumulates in the electrolyte [Fig. 32(a)], requiring a great volume and mass in order to avoid the precipitation of the salt. This fact reduces the specific energy of the battery to impractical values. 

New materials can improve the specific energy of the automobile battery, which is attracting most of the scientific effort. Nevertheless, an increase in specific power can only be obtained by a good understanding of the structural and molecular aspects that affect the electrochemistry of these materials. 

A specific energy of 30 Wh/kg literally means that 1 kg of a lead acid battery is able to power a 60 W lamp for only 0.5 h. 

Zn and Cd find application as fuels in primary and secondary electrochemical energy sources. Primary batteries provide power for short periods and can serve as reserve sources of energy. Typical is the Ag oxide—Zn battery which has a specific energy of 350Wh/kg. A special form is the Ag peroxide-Zn system ... 

The obvious drawback to the use of Li alloys instead of Li metal in batteries is the lower potential, specific charge, and specific energy of Li-alloy-based battery systems, compared with Li metal batteries. The work with Li alloys as alternatives for Li metal batteries began in the early 1970s [293], Table 8, taken from Ref. 294, presents some data on Li alloys tested as anodes in rechargeable Li battery systems. The various examples of Li alloys shown in Table 8 can be divided into three groups ... 

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.

In a typical electric car a specific power of 400 W kg and a specific energy of 200 Wh kg would mean that it is possible to achieve 0-60 mph (0-96 km h ) acceleration in 9 s with a range of 200 miles (320 km) in standard driving conditions. A lifetime of 10 years at a cost of 100 per kWh would mean that a 4000 battery could be amortized over 10 years. 

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