When Li contacts SOCl2, the following chemical reactions will occur:
8Li + 4SOCl2 →6LiCl + Li2S2O4 +
S2Cl2 or 8Li + 3SOCl2 →6LiCl + Li2SO3 +2S
Because of this reaction, although the positive electrode active material SOCl2 of the Li/SOCl2 battery tightly surrounds the negative electrode, there is actually no short circuit phenomenon. This is 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, thereby preventing the further reaction of external SOCl2 with lithium, making lithium very stable in the SOCl2 electrolyte.
With the increase of ambient temperature and the extension of battery storage time, the primary film will gradually expand and thicken to form the so-called secondary film.
The battery also has a good storage life. Therefore, the Li/SOCl2 battery has a relatively serious voltage hysteresis. This hysteresis makes the voltage return to 95% of the peak voltage within a few minutes. The Li/SOCl2 battery stored at 25℃ for two years is due to The LiCl passivation layer formed on the surface of lithium has a low initial voltage. If the battery is short-circuited or repeatedly discharged with high current, the LiCl film can be broken and the working voltage can be restored.
The products LiCl (white) and S (yellow) are deposited in the positive electrode carbon black, partially blocking the micropores in the positive electrode. On the one hand, the positive electrode is somewhat expanded, and on the other hand, it hinders the diffusion of the electrolyte, increases the concentration polarization, and makes the battery gradually fail.
The "lag" problem of lithium-ion batteries is specifically embodied in: 1. When the battery design life is not reached, the alarm is considered that the battery is dead; 2. After a period of use, when it is necessary to provide a pulse current that is much larger than the normal power supply state ,Can not work normally. Voltage hysteresis is a rather contradictory problem. In fact, the voltage hysteresis is the dense protective film formed on the negative electrode by the chemical reaction product of lithium chloride, which prevents the reaction from proceeding, but it is also a prerequisite for the existence of lithium sub-batteries and causes Very low self-discharge rate and long storage life, so the hysteresis problem of lithium sub-battery cannot be completely eliminated. Now there are related methods to eliminate the influence of voltage hysteresis: First, change the electrolyte content in the chemical system, and add inhibitors to the electrolyte to control the formation speed and thickness of the protective film, so that it is in the most reasonable state. At present, we have made a lot of efforts in this area and have achieved remarkable results; secondly, we have strengthened process control in the production process to create the best production environment;
Also, give customers the greatest support, let them understand the battery, and guide them to use the battery rationally.
There are two methods for optimizing and reasonable power use: energy storage method and delay method. Finally, it is the initiative to eliminate the hysteresis effect caused by the battery,Realize through software or hardware at regular intervals to allow the battery to provide large Load the current once to destroy the protective film formed on the negative electrode. Take the ER14505M battery as an example. The battery is discharged at 100mA for 5 seconds every 10 days, so that the battery does not see the hysteresis. At this time, the battery only consumes 5mAh in a year. The capacity is negligible relative to the total capacity of 2000mAh.
Post time: 2021-06-11 12:01:24
