Page 172 - Battery Reference Book

9/12 Lithium batteries
of 100mAh, both under the rated load. The energy extensive storage beyond 55°C is discouraged. Crimp
density is 180-300 W Wdm3 and 132 Whkg. The cells sealed batteries can be operated between -20 and
are 29.08 mm in diameter, 25-50 mm thick and weigh 70"C, whilst more recently produced laser sealed bat-
6-8g. The operational temperature range is -29 to teries can be operated between -40 and 85°C. The
+49T and they have a projected storage capability at system will work between 50 and -2O"C, subject to
23°C of more than 20 years. derating at low temperature. In some designs, up to
Development work carried out by Honeywell has 70% of the rated capacity is delivered at -20°C. Prop-
shown that although a solution of lithium hexaflu- erties include good storage life and the ability to supply
oroarsenate dissolved in methyl formate at a concen- both pulse loads and very low currents. This combina-
tration of 2 movl is one of the most conductive organic tion matches the requirements for many applications
electrolyte solutions known, at high temperatures it incorporating microprocessors,
decomposes to produce gases including carbon monox- Table 9.8 compares the energy density of Dura-
ide and dimethyl ether. This instability becomes appar- cell lithium-manganese dioxide button and cylindrical
ent in active cells through case swelling caused by a cells with those of conventional mercury-zinc, sil-
rise in internal pressure, which is often accompanied ver-zinc and zinc-alkaline manganese dioxide and
by self-discharge due to cell distortion. In reserve cells carbon-zinc cells.
instability becomes evident by premature cell activa-
tion caused by rupture of the glass electrolyte ampoule. Table 9.8 Comparison of energy density of lithium-manganese
As a result of their investigation work, Honeywell dioxide cells with conventional types
concluded that electrolyte decomposition at elevated
operating temperatures in lithium-vanadium pentox- Cell type Energy density
ide cells could be considerably reduced if the elec- Wh/dm3 Whkg
trolyte were made basic. Thus an electrolyte with the
composition 2 M lithium hexafluoroarsenate (LiAsF6) Button cells (low-rate, C1200 rate)
plus 0.4 M lithium borofluoride (LiBF4) is now used in
these cells. LiMnOz 610 225
ZnHgO 425 92
ZnAgO 535 135
9.5 Lithium-manganese dioxide Cylindrical cells, N size (moderate-rate, 100 mA discharge)
primary batteries LiMnOz 400 215

More than 80% of all lithium batteries produced are Zinc-alkaline manganese dioxide 180 63
32
60
Carbon-zinc
of the lithium-manganese dioxide type.
This is claimed to be a reliable high-energy
miniature power source with a long shelf life and
good low-temperature performance, which is safe, Lithium-manganese dioxide cells are manufactured
leakproof and non-corrosive. The lithium-manganese in a variety of button cell and cylindrical cell forms
dioxide battery is a 3V system combining a lithium ranging in capacity from 30 to 1400 mA. Larger capac-
anode and a manganese dioxide cathode in a lithium ities are under development by Duracell. Ratings are
perchlorate electrolyte. The electrolyte is dissolved C/200h rate for low-rate cells, and C/30h rate for
in an organic solvent (a mixture of propylene high-rate and cylindrical cells. In some instances, inter-
carbonate and dimethoxyethane), and the system is changeability with other battery systems is provided
completely non-aqueous. The problem of gas evolution by doubling the size of the cell to accommodate the
due to dissociation of water has now been solved 3V output of the lithium-manganese dioxide cell
and lithium-manganese dioxide cells will not bulge compared to the 1.5 V of the conventional primary
during storage or under normal operating conditions. cell. Performance Characteristics are summarized in
The system offers a stable voltage, starting at Table 9.9. These cells exhibit no gassing or pres-
approximately 3.3 V, and may be considered fully sure development in service and are therefore intrinsi-
discharged at a cut-off voltage of 2 V. The high voltage cally safe.
is supported by the high energy density associated with
lithium, making the system attractive as a substitute for 9.6 Lithium-copper oxide primary
high-energy silver oxide in 3 V and 6 V photographic batteries
applications. The energy output of the lithium cell is
up to ten times that of a zinc alkaline cell. SAFT supply this type of battery. The particular advan-
Lithium-manganese dioxide batteries are suitable tages claimed for lithium-copper oxide batteries are
for loads ranging from a few microamps to a few tens long operating life, long shelf life (up to 10 years pro-
of milliamps, with potential for upward extension. The jected) and high operating temperature (tested between
cells may be stored for up to 6 years at room tempera- -20 and +5OoC). Volumetric capacity (Ah/dm3) is
ture and still retain 85% of the original capacity. Tem- 750 compared with 300 for alkaline manganese diox-
perature excursions to 70°C are permissible, although ide, 400 for mercury-zinc and 500 for lithium-sulphur