Page 334 - Lindens Handbook of Batteries

14.2 PriMAry BATTerieS

4. Good power density. Some of the lithium batteries are designed with the capability to deliver
their energy at high current and power levels.
5. Flat discharge characteristics. A flat discharge curve (constant voltage and resistance through
most of the discharge) is typical for many lithium batteries.
6. Superior shelf life. Lithium batteries can be stored for long periods, even at elevated tempera-
tures. Storage of up to 10 years at room temperature has been achieved and storage of 1 year at
70°C has also been demonstrated. Shelf lives over 20 years have been projected from reliability
studies.

The performance advantages of several types of lithium batteries compared with conventional
primary and secondary batteries, are shown in Section 8.3. The advantage of the lithium cell is shown
graphically in Figs. 8.2 to 8.10 which compare the performance of the various primary cells. Only
the zinc/air, zinc/mercuric oxide, and zinc/silver oxide cells, which are noted for their high energy
density, approach the capability of the lithium systems at 20°C. The zinc/air cell, however, is very
sensitive to atmospheric conditions; the others do not compare as favorably on a specific energy basis
nor at lower temperatures.

14.1.2 Classification of Lithium Primary Cells
Lithium batteries use nonaqueous solvents for the electrolyte because of the reactivity of lithium in
aqueous solutions. Organic solvents such as acetonitrile, propylene carbonate, and dimethoxyethane
and inorganic solvents such as thionyl chloride are typically employed. A compatible solute is added
to provide the necessary electrolyte conductivity. (Solid-state and molten-salt electrolytes are also
used in some other primary and reserve lithium cells; see Chaps. 27, 31, 33, and 36.) Many different
materials were considered for the active cathode material; sulfur dioxide, thionyl chloride, manga-
nese dioxide, iron disulfide, and carbon monofluoride are now in common use. The term “lithium
battery,” therefore, applies to many different types of chemistries, each using lithium as the anode
but differing in cathode material, electrolyte, and chemistry as well as in design and other physical
and mechanical features.
Lithium primary batteries can be classified into several categories, based on the type of electro-
lyte (or solvent) and cathode material used. These classifications, examples of materials that were
considered or used, and the major characteristics of each are listed in Table 14.1.

Soluble-Cathode Cells. These use liquid or gaseous cathode materials, such as sulfur dioxide
(SO ) or thionyl chloride (SOCl ), that dissolve in the electrolyte or are the electrolyte solvent.
2
2
Their operation depends on the formation of a passive layer on the lithium anode resulting from a
reaction between the lithium and the cathode material. This prevents further chemical reaction (self-
discharge) between anode and cathode or reduces it to a very low rate. These cells are manufactured
in many different configurations and designs (such as high and low rate) and with a very wide range
of capacities. They are generally fabricated in a cylindrical configuration in the smaller sizes, up
to about 35 Ah, using a bobbin construction for the low-rate cells and a spirally wound (jelly-roll)
structure for the high-rate designs. Prismatic containers, having flat parallel plates, are generally
used for the larger cells up to 10,000 Ah in size. Flat or “pancake-shaped” configurations have also
been designed. These soluble cathode lithium cells are used for low to high discharge rates. The
high-rate designs, using large electrode surface areas, are noted for their high power density and are
capable of delivering the highest current densities of any active primary cell.
Solid-Cathode Cells. The second type of lithium anode primary cell uses solid rather than soluble
gaseous or liquid materials for the cathode. With these solid cathode materials, the cells have the
advantage of not being pressurized or necessarily requiring a hermetic-type seal, but they do not have
the high-rate capability of the soluble-cathode systems. They are designed, generally, for low- to
medium-rate applications such as memory backup, security devices, portable electronic equipment,
digital cameras, watches, calculators, and small lights. Button, flat, and cylindrical-shape cells are