Sources of Pressure in Lithium Thionyl Chloride Batteries

The generation of pressure in batteries has been investigated. Hydrogen, sulfur dioxide, and nitrogen are the principal gases evolved. Reaction of lithium metal with protic species in the liquid electrolyte produces hydrogen gas on open circuit and more rapidly on discharge. Sulfur dioxide is a product of electrochemical discharge. Nitrogen, trapped in lithium metal as dissolved gas or as lithium nitride is released during discharge. In addition, smaller amounts of gas, trapped in cathode pores and adsorbed on the surface of carbon, are evolved when discharge products are deposited in the cathode. Hydrogen pressure is very sensitive to the care used in drying the electrolyte and cathodes. Alternate cycles of evacuation and backfill with eliminate much of the moisture and trapped gas from the cell prior to filling with electrolyte.