What is cathode freeze?

The Cathode of a lithium thionyl chloride battery is constructed of a high surface area micropore, sponge like, carbon structure. Cathode freeze over is a chemical phenomenon that should be considered during the battery design phase.

How will it affect me?

As a product of the discharge reaction, insoluble lithium chloride is deposited on the carbon cathode at the electrolyte-cathode interface. At low rate discharge reactions lithium chloride is deposited equally within the carbon structure and the maximum rated capacity of the battery or cell is achieved.

At discharge rates exceeding the rate at which the discharge products can diffuse into the carbon micropores, lithium chloride will form only on the outer surface of the carbon cathode, leaving many of the carbon Cathode micropores towards the inner of the carbon structure incapable of catalysing further discharge reactions. Unlike anode passivation, cells suffering cathode freeze cannot be recovered and hence only a small percentage of the available cell capacity is used.