Page 81 - Handbook of Battery Materials

2.5 Lithium Primary Batteries 47

6) A high degree of stability and safety. Since Li–MnO 2 batteries do not contain
toxic liquids or gases, they pose no major pollution problems.
Li–MnO 2 batteries are classified according to their shape and construction,
which are shown in Figure 2.29.
The cathode of coin-type batteries consists of MnO 2 with the addition of a
conductive material and binder. The anode is a disk made of lithium metal, which
is pressed onto the stainless steel anode can. The separator is nonwoven cloth
made of polypropylene, which is placed between the cathode and the anode.
Cylindrical batteries can be classified into two basic types: one with a spiral
structure, and one with an inside-out structure. The former consists of a thin,
wound cathode, and the lithium anode with a separator between them. The latter
is constructed by pressing the cathode mixture into a high-density cylindrical form.
Batteries with the spiral construction are suitable for high-rate drain, and those
with the inside-out construction are suitable for high energy density.
The sealing system can also be classified into two types: crimp sealing and laser
sealing. A comparison of these sealing methods is shown in Figure 2.30, the degree
of airtightness with laser sealing being equivalent to a ceramic-based hermetic seal.
Figure 2.31 shows the construction of the 2CRS Li–MnO 2 battery, which is used
as the central power source for fully automatic cameras. The 2CR5 is composed of
two CR15400 batteries connected in series. It is encapsulated in a plastic material
and designed in shapes that will prevent misuse. The nominal voltage of the 2CR5
is 6 V.
When the 2CR5 is short-circuited, a thermal protector prevents the battery from
overheating by substantially increasing the protector resistance. When the short
circuit is removed, the 2CR5 operates normally. The thermal protector does not
impede the ability of the 2CR5 to deliver high current. When the discharge current
is depleted, the user can easily remove the 2CR5 from the camera and replace it
with a new one.
Li–MnO 2 batteries are available in a variety of shapes and construction [29] in
accordance with their particular use. Figure 2.32 shows various applications of
lithium batteries based on their drain current. Coin-type batteries are generally

Name Crimp-sealing Laser-sealing
laser welding
gasket
gasket positive cap negative cap
Structure

washer
Helium gas leakage −7 −9
(atm. cc/sec.) 10 10

Figure 2.30 The relationship of the seal type to the leak
rate of helium for cylindrical lithium–manganese dioxide
batteries.