Page 384 - Lindens Handbook of Batteries

LiTHiUM PriMAry BATTerieS 14.49

Bobbin-Type Cylindrical Cells. The bobbin-type cell is one of the two Li/MnO cylindrical cells.
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The bobbin design maximizes the energy density due to the use of thick electrodes and the maximum
amount of active materials, but at the expense of electrode surface area. This limits the rate capability
of the cell and restricts its use to low-drain applications.
A cross section of a typical cell is shown in Fig. 14.38. The cells contain a central lithium anode
core surrounded by the manganese dioxide cathode, separated by a polypropylene separator impregnat-
ed with the electrolyte. The cell top contains a safety vent to relieve pressure in the event of mechanical
or electrical abuse. Welded-sealed cells are manufactured in addition to the crimped-seal design. These
cells, which have a 10-year life, are used for memory backup and other low-rate applications.

FIGURE 14.38 Cross-sectional view of Li/MnO FIGURE 14.39 Cross-sectional view of Li/MnO spi-
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bobbin battery. (Courtesy of Duracell, Inc.) rally wound electrode battery. (Courtesy of Duracell, Inc.)
Spirally Wound Cylindrical Cells. The spirally wound cell, illustrated in Fig. 14.39, is designed
for high-current pulse applications as well as continuous moderate-rate operation. The lithium anode
and the cathode (a thin, pasted electrode on a supporting grid structure) are wound together with a
microporous separator interspaced between the two thin electrodes to form the jelly-roll construc-
tion. With this design a high electrode surface area is achieved and the rate capability increased.
High-rate spirally wound cells contain a safety vent to relieve internal pressure in the event the cell
is abused. Many of these cells also contain a resettable positive temperature coefficient (PTC) device
which limits the current and prevents the cell from overheating if short-circuited accidentally (see also
Sec. 14.8.5). Some manufacturers produce these cells with a peripheral laser-welded seal.
Multicell 9 V Battery. The Li/MnO system has also been designed in a 9 V battery with 1200 mAh
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capacity in the ANSi 1604 configuration as a replacement for the conventional alkaline zinc battery.
The battery contains three prismatic cells, using an electrode design that utilizes the entire interior
volume, as shown in Fig. 14.40. An ultrasonically sealed plastic housing is used for the battery case.
Foil Cell Designs. Other cell design concepts are being used to reduce the weight and cost of bat-
teries by using lightweight cell packaging. One of these approaches is the use of heat-sealable thin