Page 378 - Lindens Handbook of Batteries

LiTHiUM PriMAry BATTerieS 14.43

2. inherently greater safety because sulfur, which is a possible cause of thermal runaway in the Li/
SOCl battery, is not formed during the discharge of the Li/SO Cl battery.
2
2
2
3. A higher rate capability than the thionyl chloride battery as, during the discharge, more SO is
2
formed per mole of lithium, leading to a higher conductivity.
Nevertheless, the Li/SO Cl system is not as widely used as the Li/SOCl system because of several
2
2
2
drawbacks:
1. Cell voltage is sensitive to temperature variations.
2. it has a higher self-discharge rate.
3. it has lower rate capability at low temperatures.
Another type of lithium/oxychloride battery involves the use of halogen additives to both the
SOCl and SO Cl electrolytes. These additives give an increase in the cell voltage (3.9 V for the
2
2
2
Li/BrCl in the SOCl system; 3.95 V for the Li/Cl in the SO Cl system), energy density and spe-
2
2
2
2
cific energy up to 1070 Wh/L and 485 Wh/kg, and safer operation under abusive conditions.
14.7.1 Lithium/Sulfuryl Chloride (Li/SO Cl ) Batteries
2
2
The Li/SO Cl battery is similar to the thionyl chloride battery using a lithium anode, a carbon cath-
2
2
ode, and the electrolyte/depolarizer of LiAlCl in SO Cl . The discharge mechanism is
2
2
4
Li → Li + + e
Anode
-
Cathode SO Cl + 2 → e 2 2CCl + SO 2
2
Overall 2 Li SO Cl → 2 LiCl↓+ SO
+
2 2 2
The open-circuit voltage is 3.909 V.
Cylindrical, spirally wound Li/SO Cl cells were developed experimentally but were never com-
2
2
mercialized because of limitations with performance and storage. Bobbin-type cylindrical cells,
using a sulfuryl chloride/LiAlCl electrolyte and constructed similar to the design illustrated in Fig. 14.16,
4
also showed a variation of voltage with temperature and a decrease of the voltage during storage.
This may be attributed to reaction of chlorine, which is present in the electrolyte and formed by the
dissociation of sulfuryl chloride into Cl and SO . This condition can be ameliorated by including
2
2
additives in the electrolyte. Bobbin cells, made with the improved electrolyte, gave significantly
35
higher capacities at moderate discharge currents, compared to the thionyl chloride cells. This sys-
36
tem has been employed for reserve lithium/sulfuryl chloride batteries, as well (see Chap. 35).
14.7.2 Halogen-Additive Lithium/Oxychloride Cells
Another variation of the lithium/oxyhalide cell involves the use of halogen additives in both the
SOCl and the SO Cl electrolytes to enhance the battery performance. These additives result in:
2
2
2
(1) an increase in the cell voltage (3.9 V for BrCl in the SOCl system [BCX], 3.95 V for Cl
2
2
in the SO Cl system [CSC]), and (2) an increase in energy density and specific energy to about
2
2
1054 Wh/L and 486 Wh/kg for the CSC system.
The lithium/oxyhalide cells with halogen additives offer among the highest energy density of pri-
mary battery systems. They can operate over a wide temperature range, including high temperatures,
and have excellent shelf lives. They are used in a number of special applications—oceanographic and
space applications, memory backup, and other communication and electronic equipment.
These lithium/oxychloride batteries are available in hermetically sealed, spirally wound electrode
cylindrical configurations, ranging from AA to DD size in capacities up to 30 Ah. These batteries are