Chemical Principle Of Li-SOCl2 Battery

The Li/SOCl2 battery consists of a lithium negative electrode, a carbon positive electrode, and a non-aqueous SOCl2:LiAlCl4 electrolyte. Thionyl chloride is both an electrolyte and a positive active material. Other electrolyte salts, such as LiAlCl4, have been used in specially designed batteries, but with different electrolyte formulations, resulting in different electrode performance. The composition of the negative electrode, positive electrode and SOCl2 is selected by the manufacturer according to the expected performance of the battery.

The generally accepted overall reaction mechanism is:

4Li+2SOCl2→4LiCl+S↓+SO2

Sulfur and sulfur dioxide are dissolved in the excess thionyl chloride electrolyte, and during discharge, a certain degree of stress is generated due to the production of sulfur dioxide. During storage, once the lithium negative electrode is in contact with the electrolyte, it reacts with the thionyl chloride electrolyte to form LiCl, and the lithium negative electrode is protected by the LiCl film formed on it. This passivation film is beneficial to prolong the storage life of the battery, but it will cause voltage hysteresis at the beginning of discharge. The battery after long-term storage at high temperature is discharged at low temperature, and the voltage hysteresis phenomenon is particularly obvious.

The low freezing point (-110°C) and high boiling point (78.8°C) of the electrolyte enable the battery to operate over a wide temperature range, and the conductivity of the electrolyte decreases only slightly as the temperature decreases. Li/SOCl2 batteries are toxic and flammable in some components, so avoid disassembling the battery or exposing the battery and battery components to the air with the vent valve open.