Page 194 - Lindens Handbook of Batteries

AN INTRODUCTION TO PRIMARY BATTERIES 8.7

improved and small button-type batteries are now used widely in hearing aids, electronics, and
similar applications. These batteries have a very high energy density as no active cathode material
is needed. Wider use of this system and the development of larger batteries have been slow because
of some of their performance limitations (sensitivity to extreme temperatures, humidity, and other
environmental factors, such as carbonation, as well as poor activated shelf life and low power den-
sity). Nevertheless, because of their attractive energy density, zinc/air batteries are now being used
for military applications (see Chap. 33).

Magnesium Batteries. While magnesium has attractive electrochemical properties, there has been
relatively little commercial interest in magnesium primary batteries because of the generation of
hydrogen gas during discharge and the relatively poor storageability of a partially discharged cell.
Magnesium dry cell batteries have been used successfully in military communications equipment
in the past, taking advantage of the long shelf life of a battery in an undischarged condition, even at
high temperatures, and its higher energy density. Magnesium is still employed as an anode material
for reserve type and metal/air batteries (see Chaps. 33 and 34).
Aluminum Batteries. Aluminum is another attractive anode material with a high theoretical energy
density, but problems such as polarization and parasitic corrosion have inhibited the development
of a commercial product. The best promise for its use is as a reserve or mechanically rechargeable
battery (see Chaps. 10 and 34).

Lithium Batteries. The lithium anode batteries are a relatively recent development (since 1970).
They have the advantage of high energy density and specific energy, as well as operation over a very
wide temperature range with long shelf life, and are gradually replacing some conventional battery
systems. However, except for camera, medical, watch, memory backup, military, and other niche
applications, they have not yet captured the general purpose markets as was anticipated because of
their higher cost.
As with the zinc systems, there are a large number of lithium batteries which have been used
ranging in capacity from less than 5 mAh to 10,000 Ah, using various designs and chemistries, but
having in common the use of lithium metal as the anode.
The lithium primary batteries can be classified into three categories (see Chap. 14). The smallest
are the low-power solid-state batteries (see Chap. 31) with excellent shelf life, and are used in appli-
cations such as cardiac pacemakers. In the second category are the solid-cathode batteries, which are
designed in coin or small cylindrical configurations. These batteries have replaced the conventional
primary batteries in watches, calculators, memory circuits, photographic equipment, communication
devices, and other such applications where its high energy density and long shelf life are critical.
The soluble-cathode batteries (using liquid cathode materials) constitute the third category. These
batteries are typically constructed in a cylindrical configuration, as flat disks, or in prismatic contain-
ers using flat plates. These batteries, up to about 35 Ah in size, are used in military and industrial
applications, lighting products, and other devices where small size, low weight, and operation over
a wide temperature range are important. The larger batteries have been used for special military
applications or as standby emergency power sources.

Solid Electrolyte Batteries. The solid-electrolyte batteries are different from other battery systems
in that they depend on the ionic conductivity, in the solid state, of an electronically nonconductive
compound rather than the ionic conductivity of a liquid electrolyte. Batteries using these solid elec-
trolytes are low-power (microwatt) devices, but have extremely long shelf lives and the capability of
operating over a wide temperature range, particularly at high temperatures. These batteries have been
used in medical electronics, for memory circuits, and for other such applications requiring a long-
life, low-power battery. The first solid-electrolyte batteries used a silver anode and silver iodide for
the electrolyte, but lithium is now the anode of choice for most of these batteries, offering a higher
voltage and energy density. Current use is limited except in pacemakers where the LiI electrolyte
forms “in situ”.