Li/SOCl2 batteries are manufactured in a wide variety of sizes and configurations. The capacity from 400mAh cylindrical charcoal and wound electrode structure batteries to Ah square batteries and many others to meet special requirements. The Li/SOCl2 system originally has safety and voltage delay problems. The safety problem was particularly likely to occur at high rate discharge and over discharge. And the voltage delay occurs when the battery continues to be discharged at low temperature after storage at high temperature.
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Low discharge rate batteries are mainly used for backup voltage of memory and other applications requiring long working life. Large square batteries have been used for military applications as an emergency application power source. And medium and high discharge rate batteries have also been developed for powering various electrical and electronic devices. In some of the batteries, thionyl chloride and other oxyhalide electrolytes are usually added with additives to improve the battery specific performance.
The Li/SOCl2 battery consists of lithium negative electrode, carbon positive electrode and a non-aqueous SOCl2:LiAlCl4 electrolyte. Thionyl chloride is both electrolyte and positive electrode active material. Other electrolyte salts like LiAlCl4 have been used in specially designed batteries.
The general reaction mechanism is:
4Li+2SOCl2→4LiCl↓+S+SO2
Sulfur and sulfur dioxide are dissolved in an excess of thionyl chloride electrolyte, and during discharging, a certain amount of pressure is generated due to the production of sulfur dioxide. During storage, the lithium negative electrode reacts with the thionyl chloride electrolyte to form LiCl upon contacting with the electrolyte. The lithium negative electrode is protected by the LiCl film formed thereon. This passivation film is beneficial for prolonging the storage life of the battery but causes a voltage delay at the beginning of discharge.After long-term storage at a high temperature and then discharged at a low temperature, the battery voltage hysteresis is particularly remarkable.
Li/SOCl2 batteries use lithium as the negative electrode and carbon as the positive electrode. SOLi2 used as the electrolyte and the positive electrode active material. Polypropylene felt or fiberglass paper is used as the separator. The open circuit voltage is 3.65V. The battery system can be expressed 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
Total battery response:
4Li + 2SOCl2→4LiCl + S + SO2 SO2
Dissolved in SOCl2, S is precipitated in a large amount and deposited in the positive carbon black, and LiCl is insoluble.
When Li contacted with SOCl2, the following reaction occurs:
8Li + 4SOCl2 →6LiCl + Li2S2O4 + S2Cl2 or 8Li + 3SOCl2 →6LiCl + Li2SO3 +2S
Due to this reaction, although the positive active material SOCl2 of the Li/SOCl2 battery closely surrounds the negative electrode, the short circuit phenomenon does not actually occur because a very thin dense LiCl protective film is formed on the surface of the negative electrode ( Primary film). This film is electronically insulating and can penetrate ions, thus preventing the external reaction of SOCl2 and lithium, making lithium become very stable in SOCl2 electrolyte. With the increase of ambient temperature and storage time of the battery is prolonged, the film will gradually enlarge and become thicker to form a so-called secondary film, so the battery has a good storage life.
As a result, the Li/SOCl2 battery has a relatively severe voltage hysteresis, which causes the voltage to recover to 95% of the peak voltage in a matter of minutes. The Li/SOCl2 battery stored at 25 °C for two years, due to the LiCl passivation layer formed on the surface of the lithium, the initial voltage is low, such as battery short circuit or multiple high-current brake discharge, the LiCl film can be broken, so that the working voltage restore. The products LiCl (white) and S (yellow) are deposited in the positive carbon black, partially blocking the micropores in the positive electrode. On the one hand, the positive electrode is somewhat expanded, on the other hand, the diffusion of the electrolyte is hindered, the concentration polarization is increased, and the battery is gradually failed.
Higher energy density and lower weight.
High and stable load voltage
Superior drain capacity.
Low self-dischage rate (less than 1% after 1 year of storage at 20 °C)
Stainless steel container.
Hermetic glass-to-metal sealing.
Non-flammable electrolyte.
Laser weilding.
Lithium thionyl chloride batteries (Li/SOCl₂) belong to the lithium primary cell family. Unlike lithium ion or lithium polymer batteries, these cells cannot be recharged once they have been discharged. However, due to their long lifetime, this characteristic is of little importance in everyday use. In fact, lithium thionyl chloride batteries supply power to applications for several months or even years before they need to be replaced.
Li/SOCl₂ batteries have been an integral part of Jauch’s battery portfolio for many years. This year, the portfolio expanded to include batteries from Jauch’s own brand. The most important properties of this cell chemistry are briefly presented below.
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Lithium primary cells, which also include lithium iron sulfide or lithium manganese dioxide batteries, usually have a cell voltage between 1.5 volts and 3 volts. However, the cell voltage of a lithium thionyl chloride battery is significantly higher than these values: with a voltage of 3.6 volts. At this value, the battery performs to the level of lithium ion batteries. This voltage level is kept constant by the battery over almost the entire discharge period – an absolute unique selling point of lithium thionyl chloride cell chemistry.
In terms of energy density, Li/SOCl₂ batteries are also superior to all other primary cells. Values up to 710 watt hours/kilogram are possible.
Lithium thionyl chloride batteries are used wherever low currents are required over a long period of time. Typical applications are for example locking cylinders, timers, toll systems or all kinds of metering applications. The high energy density of the thionyl chloride cells ensures that these applications can be operated for several months or even years without having to replace the battery.
Lithium thionyl chloride batteries are designed for use in a temperature range between -60 and +85 degrees Celsius. Particularly noteworthy is the performance of the cells at low temperatures. Even at double-digit minus temperatures, the cells deliver a constantly high voltage.
Lithium thionyl chloride batteries are very durable and have a very good shelf life. The self-discharge rate of only 1% per year speaks for itself.
The longevity of lithium thionyl chloride batteries is due to the chemistry of the cell. Unlike other lithium primary cells, the lithium thionyl chloride cell undergoes a chemical reaction between the lithium anode and the electrolyte. As a result, a protective film forms over the lithium anode, which impedes the ion flow between the anode and cathode. This is referred to as “passivation” of the battery cell.
This phenomenon has advantages and disadvantages. On the one hand, passivation is responsible for the low self-discharge rate of the battery. On the other hand, the resulting protective film initially impedes the current flow when the battery is put into operation. The protective film gradually fades away as the battery continues to operate. However, it forms again as soon as the battery stops drawing current. For this reason, lithium thionyl chloride batteries are particularly suitable for applications with low power consumption. The power requirement of the application can be constant or pulse-shaped.
Lithium thionyl chloride batteries are available in numerous sizes and designs. No matter what variation your application requires, the core properties: high voltage, high energy density and long life, stay the same.
The “Bobbin-type” construction has established itself as the most frequently used cell construction method. This design, which is also used in the cells of Jauch’s thionyl chloride batteries, is characterized by a high level of safety and a long service life. These batteries deliver currents of up to two Amperes.
Jauch’s battery portfolio includes various Li/SOCl₂ batteries. An overview of the entire Jauch portfolio of lithium thionyl chloride batteries can be found here.
Our battery experts will be happy to advise you on which of these cells is best suited for your application. Equipped with the expertise from countless successfully completed projects, our experts will also find the perfect solution for your requirement profile and will advise you on request directly at your site.
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