Cell voltage lithium thionyl chloride

Both the lithium sulfur dioxide (Li-SO and lithium thionyl chloride (Li-SOCy cells may be classified as liquid cathode systems. In these systems, S02 and SOCl2 function as solvents for the electrolyte, and as the active materials at the cathode to provide voltage and ampere capacity. As liquids, these solvents permeate the porous carbon cathode material. Lithium metal serves as the anode, and a polymer-bonded porous carbon is the cathode current collector in both systems. Both cells use a Teflon-bonded acetylene black cathode structure with metallic lithium as the anode. The Li-S02 is used in a spirally wound, jelly-roll construction to increase the surface area and improve... 

Three principal types of lithium organic electrolyte battery are currently available the lithium-thionyl chloride system, the lithium-vanadium pentoxide system and the lithium-sulphur dioxide system. These batteries all have high-rate capabilities. The approximate open-circuit equilibrium cell voltages for these various cathode systems and for some other systems that have been considered are shown in Table 9.2. 

After extended storage, a reactivation time of the order of a few seconds is required for the system to achieve operating voltage. This is not a feature exclusive to lithium-sulphur dioxide cells, but one which is also exhibited by lithium-vanadium pentoxidc and lithium-thionyl chloride cells. 

SAFT lithium-thionyl chloride cells exhibit a highly stable service voltage and a far greater capacity than conventional zinc-manganese dioxide and carbon-zinc cells of the same size and configuration. 

Figure9.5 Voltage discharge profile of llthlum-vanadlum pen-toxide (VzOa), lithlum-thionyl chloride (SOCIj), lithium-sulphur dioxide (SO2) lithium-molytxfenum trioxide (M0O3) cells (Courtesy of Honeywell)...

Hazardous incidents have been experienced with some lithium systems, particularly those using sulphur dioxide and thionyl chloride cathodes. These incidents generally occur at later stages in battery life under reverse current conditions, during voltage reversal and while operating at high temperatures. Safety incidents have not been experienced with lithium-iodine cells, which is why they power 90% of the cardiac pacemakers presently in use. 

For about a century after the invention of the Ledanche cell (and the lead-acid rechargeable battery) the highest voltage attained in any battery was 2.1V, and primary cells delivered a maximum voltage of about 1.5 V. This changed in the mid 1960s, when the Li-thionyl chloride (LiSOCb) battery was introduced. In this and other nonaqueous lithium batteries, a potential of about 3.0 V was achieved. 

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