Page 383 - Lindens Handbook of Batteries

14.48 PriMAry BATTerieS

The capacity of batteries available commercially ranges up to 11.1 Ah. Larger sized batteries are
available for special applications and have been introduced commercially. its attractive properties
include a high cell voltage (nominal voltage 3 V), specific energy about 280 Wh/kg and an energy
density above 588 Wh/L, depending on design and application, good performance over a wide tem-
perature range, long shelf life, storability even at elevated temperatures, and low cost.
The Li/MnO battery is used in a wide variety of applications such as long-term memory backup,
2
safety and security devices, cameras, many consumer devices, and in military electronics. it has
gained an excellent safety record during the period since it was introduced.
The performance of a Li/MnO battery is compared with comparable mercury, silver oxide, and
2
zinc batteries in Sec. 8.3, illustrating the higher energy output of the Li/MnO battery.
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14.8.1 Chemistry
The Li/MnO cell uses lithium for the anode, and an electrolyte containing lithium salts in a mixed
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organic solvent, such as propylene carbonate and 1,2-dimethoxyethane, and a specially prepared
heat-treated form of MnO for the active cathode material.
2
The cell reactions for this system are
→
Anode x Li → Li + + e
iii
Cathode Mn iV 2 + O x + + Li e → LiMnO 2
x
Overall x Li + iV → Mn O Mn O
iii
i
2 2
Manganese dioxide, an intercalation compound, is reduced from the tetravalent to the trivalent state,
+
producing Li MnO as the Li ion enters into the MnO crystal lattice. 1,39
2
2
x
The theoretical voltage of the total cell reaction is about 3.5 V, but an open-circuit voltage of
a new cell is typically 3.3 V. Cells are typically predischarged to lower the open-circuit voltage to
reduce corrosion.
14.8.2 Construction
The Li/MnO electrochemical system is manufactured in several different designs and configurations
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to meet the range of requirements for small, lightweight, portable power sources.
Coin Cells. Figure 14.37 shows a cutaway illustration of a typical coin cell. The manganese
dioxide pellet faces the lithium anode disk and is separated by a nonwoven polypropylene separator
impregnated with the electrolyte. The cell is crimped-sealed, with the can serving as the positive
terminal and the cap as the negative terminal.

Collector
Anode cap Negative electrode (Li)
Insulation
packing
Positive
Cathode can
electrode (MnO )
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Organic electrolyte
and separator
FIGURE 14.37 Cross-sectional view of Li/MnO coin-type
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battery. (Courtesy of Duracell, Inc.)