CELL DESIGN: Mechanical Design Cell Components and Materials Chemical Reaction Mechanical Design Tadiran Lithium Thionyl Chloride Cells are either of the cylindrical BOBBIN type, or of the flat WAFER type. The typical internal construction of each type is shown below. Section Through the Tadiran Lithium 3.6V Cell Cell Components and Materials ¨ Anode: system, contribute to the outstanding The anode is made of battery grade voltage stability of lithium thionyl lithium foil, which is pressed on to the chloride cells. The low freezing point inner surface of the cell can to provide (-105ºC) and relatively high boiling a mechanically sound and reliable point (>79ºC) of the electrolyte result electrical connection. in a battery capable of operating over a wide temperature range. ¨ Separator: The separator, between the anode ¨ Current Collector: and the cathode, prevents internal A metal current collector provides the shorts while enabling ions to move electrical connection between the freely between the electrodes. It is porous carbon cathode and the made of non-woven glass, carefully positive terminal of the battery. selected for compatibility with the chemical system during prolonged ¨ Can and Cover: storage and subsequent operation. The cell can and cover are made of nickel-plated cold-rolled steel. The ¨ Cathode: can is designed to withstand the The cathode is made of highly porous mechanical stresses that would be Teflon-bonded carbon powder. encountered over the anticipated wide Thionyl Chloride cathodic reduction range of environmental service occurs on the cathode surface when conditions. a load is connected. The high porosity of the carbon results in a true surface ¨ Hermetic Seal: area compatible with the current The positive (+) cell termination of the capability of the cell. Tadiran lithium cell, is insulated from The cell cover, which is the negative ¨ Electrolyte: (-) termination, by a glass-to-metal The electrolyte is basically a solution seal that uses compression sealing of Lithium Aluminum Tetrachloride in technology. In addition, the cell cover Thionyl Chloride which is highly ionic conductive over the entire is welded to the cell can by a LASER temperature range. This outstanding seam welding process. The resultant feature and the negligible mass ultra-high hermeticity and mechanical transport loss in the electrochemical integrity are major contributors to the excellent shelf-life obtained. Chemical Reaction Overall: All Tadiran lithium cells are based on 4Li + 2SOCl → 4LiCl + S + SO 2 2 the same electrochemical system. The reactions during current flow are: Most of the SO formed during cell 2 discharge is dissolved in the At the Anode: electrolyte and cathode. This + - 4Li → 4Li 4e accounts for the low internal cell pressure before, during and after At the Cathode: normal discharge. - - 2SOCL → SO + S + 3Cl -4e 2 2 (on the carbon surface)