Lithium/sulfur dioxide batteries types

Batteries for implantable medical devices are hermetically sealed. Hermetic seals have long been used for certain cell types, like lithium-sulfur dioxide and lithium-thionyl chloride, where long shelf life is important, or exposure to corrosive and toxic materials could result if the cell leaks. 

The Jet Propulsion Laboratory (Pasadena, CA) has evaluated several types of lithium primary batteries to determine their ability to operate planetary probes at temperatures of -80°C and below. Individual cells were evaluated by discharge tests and Electrochemical Impedance Spectroscopy. Of the five types considered (Li/SOCl2, Li/S02, Li/Mn02, Li-BCX and Li-CFn), lithium-thionyl chloride and lithium-sulfur dioxide were found to provide the best performance at -SOT. Lowering the electrolyte salt to ca. 0.5 molar was found to improve performance with these systems at very low temperatures. In the case of D-size Li/ SOCI2 batteries, lowering the LiAlCl4 concentration from 1.5 to 0.5 molar led to a 60% increase in capacity on a baseline load of 118 ohms with periodic one-minute pulses at 5.1 ohms at -85 C. 

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. 15, 20, and 21.) Many different materials were considered for the active cathode material sulfur dioxide, manganese 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. 

---