Working Principle Of Li-SOCl2 Battery

Li-SOCl2 batteries use lithium as the negative electrode, carbon as the positive electrode, an SOCl2 solution of anhydrous lithium tetrachloroaluminate (LiAlCl4) as the electrolyte, and SOCl2 as the positive electrode active material. Using polypropylene felt or glass fiber paper as the separator, its open circuit voltage is 3.65V, and the battery system can be represented by the following formula:

Li/LiACl4-SOCl2/C

Negative electrode: 4Li=4Li++4e

Positive electrode: 2SOCL2+4e=2SO2+4Cl-2SO→←(SO)2(SO)2→←S+SO2

Overall battery response:

4Li+2SOCl2→ 4LiCl+S+SO2SO2 is all dissolved in SOCl2, S is precipitated in large quantities and deposited in the positive carbon black, LiCl is insoluble.

In this kind of battery, when Li contacts SOCl2, the following reactions will occur:

8Li+4SOCl2→6LiCl+Li2S2O4+S2Cl2 or 8Li+3SOCl2→6LiCl+Li2SO3+2S

Because of this reaction, although the positive active material SOCl2 of the Li/SOCl2 battery tightly surrounds the negative electrode, there is actually no short circuit phenomenon, because a very thin and dense LiCl protective film is formed on the surface of the negative electrode ( Primary film), this film has electronic insulation and can penetrate ions, thus preventing the further reaction of external SOCl2 and lithium, making lithium very stable in SOCl2 electrolyte, with the increase of ambient temperature and With the prolongation of battery storage time, the primary film will gradually expand and thicken to form the so-called secondary film, and the battery will have a good storage life.

Therefore, the Li/SOCl2 battery has a relatively serious voltage hysteresis phenomenon, which makes the voltage generally return to 95% of the peak voltage within a few minutes. Li/SOCl2 batteries stored at 25°C for two years have a low initial voltage due to the LiCl passivation layer formed on the lithium surface. If the battery is short-circuited or repeatedly discharged with a large current, the LiCl film can be broken and the working voltage can be reduced. recover. The products LiCl (white) and S (yellow) were deposited in the carbon black of the positive electrode, which partially blocked the micropores in the positive electrode. On the one hand, the positive electrode swells a little, and on the other hand, it hinders the diffusion of the electrolyte, increases the concentration polarization, and makes the battery gradually fail.