Direct Energy, 2018a

224 9.5 Battery Types
specic energies. As another example, tiny batteries are used to power
microelectromechanical systems such as micropumps [142] [143]. These
batteries must have high specic energy and be able to be produced in
small packages. Some are even built into integrated circuits [144] [145].
One way to classify batteries is as primary or secondary. A primary
battery is used once, then disposed. A secondary battery is a rechargeable
battery. Primary batteries have the advantage of simplicity [128, ch. 8].
They do not require maintenance, so they are simple to use. Also, their
construction may be simpler than secondary batteries because they do not
need additional circuitry built in to monitor or control the recharging process.
They often have high specic energy too [128, ch. 8]. They come
in a variety of sizes and shapes, and they are made with a variety of electrode
and electrolyte materials. Many alkaline and lithium ion batteries
are designed to be primary batteries. Secondary batteries have the obvious
advantage of not producing as much waste that ends up in a landll.
Also, the user does not need to continually purchase replacements. While
secondary batteries may cost more initially, they can be cheaper in long
run. They are often designed to be recharged thousands of times [128, ch.
15]. Many secondary batteries have a very at discharge curve, so they
produce a constant voltage throughout use, even upon multiple charging
cycles [128, ch. 15]. Two of the most common types of secondary batteries
are lead acid batteries and lithium batteries.
There are many battery types, distinguished by choice of electrolyte
and electrodes. Four common battery types are discussed in this section:
lead acid, alkaline, nickel metal hydride, and lithium. Not all batteries
t into one of these families. Some devices, like zinc air batteries, are
even harder to categorize. Zinc air batteries are actually battery fuel cell
hybrids because the zinc of the anode is consumed as in battery operation
while oxygen from air is consumed as in fuel cell operation. However, by
considering these four classes, we will see some of the variety available. For
a more thorough and encyclopedic discussion of battery types, see reference
[128].
Table 9.2 summarizes example batteries of each of these four types. The
rst three rows list example materials used to make the anode, cathode,
and electrolyte for batteries. Materials listed in the table are just examples,
so batteries of each type can be made with a variety of other materials too.
The next two rows give approximate values for the specic energy in units of
W·h
kg
. All values are approximate values for representative devices provided
to give an approximate value for comparison, not necessarily values for a
particular device. The fth row lists example values for the theoretical