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The working principle of thionyl chloride lithium battery

From:CTECHI GROUP Limited     Release time:2021-03-22

Overview:SOCl2 is a liquid covalent inorganic compound, which acts as both a positive electrode reactant and a solvent in the electrolyte solution in the battery. SOCl2 is a light yellow to red liquid with a density of 1.638, a boiling point of 78.8°C, and a melting point of -105°C. It can be miscible with benzene, chloroform, carbon tetrachloride, etc., decomposes in water to form sulfurous acid and hydrochloric acid, and decomposes into sulfur dioxide, chlorine and sulfur monochloride when heated. It can be formed by the action of sulfur dichloride and sulfur trioxide. , It is liquid at room temperature.

SOCl2 is a liquid covalent inorganic compound, which acts as both a positive electrode reactant and a solvent in the electrolyte solution in the battery. SOCl2 is a light yellow to red liquid with a density of 1.638, a boiling point of 78.8°C, and a melting point of -105°C. It can be miscible with benzene, chloroform, carbon tetrachloride, etc., decomposes in water to form sulfurous acid and hydrochloric acid, and decomposes into sulfur dioxide, chlorine and sulfur monochloride when heated. It can be formed by the action of sulfur dichloride and sulfur trioxide. , It is liquid at room temperature.


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 electrode active material. Other electrolyte salts, such as LiAlCl4, have been used in specially designed batteries, but the electrolyte formulation is different, the electrode performance is different. The composition of the negative electrode, positive electrode and SOCl2 should be selected by the manufacturer according to the expected performance of the battery.


The generally recognized overall reaction mechanism is: 4Li+2SOCl2→4LiCl↓+S+SO2


Sulfur and sulfur dioxide are dissolved in the excess thionyl chloride electrolyte, and during discharge, due to the generation of sulfur dioxide, a certain degree of pressure is generated. During storage, as soon as the lithium negative electrode comes into contact with the electrolyte, it reacts with the thionyl chloride electrolyte to produce 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 a voltage lag at the beginning of the discharge. The battery that has been stored for a long time at a high temperature will discharge at a low temperature, and the voltage lag is particularly obvious.


The electrolyte's low freezing point (-110°C) and high boiling point (78.8°C) enable the battery to work in a wide temperature range. As the temperature drops, the electrolyte's conductivity only slightly decreases. Li/SOCl2 batteries are toxic and flammable in some components, so avoid disassembling the battery or exposing the battery and battery components with the exhaust valve to the air.


Advantages of Li/SOCl2 battery:

1. The specific energy is very large: Because it is both a solvent and a positive electrode active material, its specific energy generally can reach 420Wh/Kg, and it can be as high as 650Wh/Kg during low-rate discharge;

2. The voltage is very high: the open circuit voltage of the battery is 3.65V, at 1mA/cm2, the voltage can be maintained at 3.3V when discharging, and the voltage remains unchanged within 90% of the capacity range;

3. Large specific power: the battery can discharge at a current density of 10mA/cm2 or higher;

4. High voltage accuracy: the discharge curve is extremely flat when discharging at room temperature and medium current density;

5. Good high and low temperature performance: Generally, it can work normally at -40-50℃, even at -50-150℃; the capacity at -40℃ is about 50% of the normal temperature capacity;

6. Good storage performance: Generally, it can be stored wet for 5 years or longer;

7. Fully sealed design;

8. The battery has no internal pressure: there is no internal pressure at the beginning, and a certain pressure does not appear until the end of the discharge.


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