JPH04245168A - Thionyl chloride-lithium battery - Google Patents

Abstract

PURPOSE:To prevent rupture or explosion, etc., due to an abrupt external heating by constituting a positive pole layer inside a battery case, and providing lithium at a negative pole in the center portion so as to separate the surface of the negative pole from the inside of the battery case by a predetermined distance. CONSTITUTION:A positive pole layer 3 is constituted inside a battery case 5; a lithium of a negative pole 1 is provided in the center portion; the surface of the negative pole 1 is separated from the inside of the battery case 5 more than 1.5mm apart; and a glass seal 9 serving as an explosion-protecting mechanism which operates in the range of 20 to 80kg/cm<2> of a battery internal pressure. When this battery is externally heated, since the lithium in the center portion of the battery is heated through an electrolyte, its temperature does not become higher than that of the electrolyte, so that the electrolyte is discharged outside the battery at temperature equal to or lower than the melting temperature of lithium to efficiently prevent a direct reaction between molten lithium and a thionyl chloride by operating the explosion-protecting mechanism 9 within the range of 20 to 80kg/cm<2> of the battery internal pressure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thionyl chloride/lithium battery using thionyl chloride as a solvent for an electrolyte and a positive electrode active material and lithium as a negative electrode active material.

0002

BACKGROUND OF THE INVENTION A thionyl chloride-lithium battery, which uses thionyl chloride as the electrolyte solvent and positive electrode active material and lithium as the negative electrode active material, has high energy density and excellent low-temperature characteristics. The electromotive reaction of the battery is 2SOCl2 +
It is shown as 4Li→ 4LiCl +SO2 + S, where lithium and thionyl chloride react electrochemically to produce lithium chloride, sulfur dioxide, and sulfur.

[0003] Lithium as a negative electrode has strong hygroscopicity, and thionyl chloride as a positive electrode active material and sulfur dioxide as a discharge product are highly irritating, so batteries have adopted a completely sealed structure using a hermetic seal. Although the hermetic seal has the advantage of excellent storage properties due to its high airtightness, there is a risk of rupture or explosion if the internal pressure of the battery becomes abnormally high due to incorrect use.

Conventionally, in order to avoid such dangers, battery cases have been provided with an explosion-proof mechanism. If the internal pressure of the battery becomes abnormally high, the explosion-proof mechanism is activated to release some of the battery contents to prevent the battery from bursting or exploding. Such explosion-proof mechanisms include the use of pressure reducing valves,
Some battery cases have grooves or thin-walled parts in a part of the battery case so that tearing and failure occur when the internal pressure rises abnormally. Additionally, the hermetic seal is destroyed by utilizing stress caused by increased internal pressure.

FIG. 2 is a cross-sectional view of a conventional cylindrical lithium thionyl chloride battery having an explosion-proof groove provided on the bottom of the battery case. 1 is a negative electrode made of lithium, 2 is a side separator made of glass fiber nonwoven fabric, and 3 is a positive electrode made of porous carbon. 14 is a positive electrode current collector made of nickel. 5 is a battery case made of stainless steel, and the negative electrode 1 is configured in contact with the inner surface of the battery case. Reference numeral 6 denotes a lid body made of stainless steel, and the outer periphery of this lid body 6 is welded to the opening of the battery case 5. A small hole 7 is bored in the center of the lid 6, and a rod-shaped positive electrode terminal 15 made of stainless steel is bonded to the small hole 7 via an electrically insulating glass sealing material 9 to form a hermetic seal. ing. 10 is a liquid injection port, which is sealed by welding after the electrolyte is injected. As the electrolytic solution 13 of this battery, a solution prepared by dissolving lithium aluminate tetrachloride in thionyl chloride is used, and the thionyl chloride also functions as a positive electrode active material. Reference numeral 16 denotes an explosion-proof groove, which is formed in the shape of a cross at the bottom of the container, and is ruptured when the battery internal pressure rises abnormally to prevent the container from bursting.

[0006]

[Problem to be solved by the invention] In conventional batteries, when the internal pressure of the battery rises abnormally due to incorrect use such as overcharging, overdischarging, or short circuiting, the explosion-proof mechanism is activated and some of the contents are released. We were able to prevent the battery from exploding. however,
The drawback was that the explosion-proof mechanism did not operate properly under conditions of rapid temperature rise, such as when directly exposed to fire, resulting in rupture or explosion.

When a lithium thionyl chloride battery is heated due to an internal short circuit or external heating, the vapor pressure of thionyl chloride and the discharge product sulfur dioxide increases as the temperature rises, causing the internal pressure to rise. , there is a risk of rupture. Furthermore, when the temperature reaches the melting point of lithium in the negative electrode, 180° C., a direct reaction between the molten lithium and thionyl chloride occurs, resulting in an instantaneous explosion. Conventional batteries detect an increase in internal pressure and activate an explosion-proof mechanism to release thionyl chloride before the lithium temperature reaches 180°C. This is because without thionyl chloride, no explosion will occur even if lithium melts.

However, in conventional batteries, the negative electrode is formed on the inside of the battery case, so if the battery is suddenly heated from the outside, the temperature of the lithium will rise before the temperature inside the battery reaches the operating pressure of the explosion-proof mechanism. Temperatures could exceed 180 degrees Celsius, and explosions could not be prevented.

[0009]

[Means for Solving the Problems] The present invention provides a cylindrical thionyl chloride/lithium battery using thionyl chloride as the solvent of the electrolytic solution and the positive electrode active material, and lithium as the negative electrode active material. a positive electrode layer configured in contact with the battery, a separator, a negative electrode configured in the center via the separator, and an explosion-proof mechanism that operates within a battery internal pressure range of 20 kg/cm2 to 80 kg/cm2, and the negative electrode The surface of is 1.5mm from the inside of the battery case.
It is characterized by being far apart.

0010

[Operation] Contrary to the conventional battery structure, the battery of the present invention has a positive electrode layer on the inner surface of the battery case, and the negative electrode lithium is provided in the center of the battery, so that the surface of the negative electrode is 1.5 mm higher than the inner surface of the battery case.
By using an explosion-proof mechanism that operates at an appropriate battery internal pressure with a separation of at least 2 mm, the occurrence of abnormalities such as rupture and explosion can be prevented even in the event of sudden external heating.

That is, when the battery of the present invention is heated from the outside, the electrolyte in the positive electrode or the separator is heated through the positive electrode layer, and as the battery temperature rises, the internal pressure of the battery increases. Battery internal pressure from 20kg/cm2 to 80kg
By operating the explosion-proof mechanism within the range of /cm2, the electrolytic solution is discharged to the outside of the battery at a temperature below the melting temperature of lithium, and direct reaction between molten lithium and thionyl chloride is effectively prevented. Because the lithium in the center of the battery is heated through the electrolyte, it does not reach a temperature higher than that of the electrolyte, unlike in conventional batteries. However, if the positive electrode layer or separator layer is thin and the distance between the negative electrode surface and the battery case is too close,
The temperature of lithium may increase due to local overheating, and the distance between the surface of the negative electrode and the inner surface of the battery case is 1
．． It is desirable to set it to 5 mm or more.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cross-sectional view of a lithium thionyl chloride battery according to the present invention. 5 is the battery case, which has a diameter of 1
4mm, height 48mm cylindrical shape with a bottom, thickness 0.5mm
Made of stainless steel. 3 is a positive electrode provided on the inner peripheral surface of the battery case 5. This positive electrode 3 is a cylindrical porous carbon body made of acetylene black with 10% by weight of polytetrafluoroethylene as a binder, and has a thickness of 1.4 mm. The inside of this positive electrode 3 has a thickness of 0.
A side separator 2 made of a non-woven glass fiber fabric of 4 mm is disposed, and a protective separator 11 of 1.2 mm thick and a bottom separator 12 of 0.6 mm thick are disposed on the bottom surface. A cylindrical negative electrode 1 is housed through these cell plates. This negative electrode 1 is made of metallic lithium, and a negative electrode current collector 4 made of expanded metal made of nickel is crimped inside thereof. 6 is thickness 0.
The lid 6 is made of a 5 mm stainless steel plate, and the outer periphery of the lid 6 is laser welded to the opening of the battery case 5. A small hole 7 with a diameter of 4 mm is bored in the center of the lid body 6.
A rod-shaped negative electrode terminal 8 made of stainless steel and having a diameter of 2.3 mm is joined to this small hole 7 via an electrically insulating glass sealing material 9, thereby forming a hermetic seal. Further, this small hole 7 acts as an explosion-proof mechanism when the glass seal 9 is broken due to an increase in the internal pressure of the battery. The thickness of the lid body 6 and the diameter of the small hole 7,
By changing the thickness and material of the glass sealing material 9,
The operating pressure at which the glass seal material breaks can be changed as appropriate. The negative electrode terminal 8 and the negative electrode current collector 4 are spot welded. As the electrolytic solution 13, a solution in which lithium aluminate tetrachloride was dissolved in thionyl chloride at a rate of 1.5 mol/liter was used. Thionyl chloride functions both as an electrolyte and as a positive electrode active material. 10 is a liquid injection port, which is sealed by welding after the electrolyte is injected.

[0013] The operating pressure of the glass sealing material that acts as an explosion-proof mechanism is 20 kg/cm2 and 30 kg/cm, respectively.
2, 40kg/cm2, 60kg/cm2,
Ten batteries each having the above configurations with a weight of 80 kg/cm 2 and 100 kg/cm 2 were assembled, and a heating test was conducted.

FIG. 3 shows the heating test method. 17 is a test battery, 18 is a gas burner, and the distance between the test battery and the gas burner was 10 cm.

[0015] The test battery had an explosion-proof mechanism operating pressure of 100k.
Although two explosions were observed in batteries with a working pressure of 80 kg/cm2 or less, the explosion-proof mechanism was activated during heating for all batteries with an operating pressure of 80 kg/cm2 or less. In batteries where the explosion-proof mechanism was activated, the electrolyte was released or evaporated from the glass seal, and no rupture or explosion occurred even if heating continued. In a battery with an explosion-proof mechanism activated, as long as there is an electrolyte, the temperature will not rise above the boiling point of the electrolyte, and by the time the lithium in the negative electrode melts, there is no longer any thionyl chloride in the battery, and an explosive reaction will occur. That's because you don't get it. However, the working pressure is 100kg/
It is thought that some of the lithium batteries had heated up to near their melting point by the time the explosion-proof mechanism was activated, leading to explosions. Therefore, it is desirable that the operating pressure of the explosion-proof mechanism be 80 kg/cm2 or less. Note that if the operating pressure is too low, it may operate even during normal high-temperature use, so it is desirable to set it to 20 kg/cm2 or more.

The negative electrode surface of the test battery used in the above heating test was separated from the inner surface of the battery case by 1.8 mm. Similar heating tests were conducted on batteries in which the thickness of the positive electrode was reduced from 1.4 mm to 1.1 mm, and it was confirmed that they would not explode. The thickness of the separator used was 0.4 mm, and the negative electrode surface of the test battery was 1 inch from the inner surface of the battery case.
．． They were 5mm apart.

However, if the thickness of the positive electrode is 0.8 mm
However, some batteries exploded even though the explosion-proof function was activated. In addition, the thickness of the positive electrode is 1.1 mm
However, when the separator thickness was 0.2 mm, a similar explosion phenomenon was observed. This is thought to be because the distance between the battery case and the lithium surface was too close, and the lithium was locally heated and melted.

[0018] In order to prevent the battery from exploding, the distance between the inner surface of the battery case and the lithium must be 1.5 mm or more. If the distance from the battery case is 1.5 mm or more, the lithium surface is protected by the positive electrode layer and separator layer, so local heating is unlikely to occur, and as long as there is an electrolyte between them, the lithium surface will be heated up to the melting temperature of lithium. This is because it is never heated.

Regarding conventional batteries with a lithium negative electrode provided on the inner surface of the battery case, the operating pressure of the explosion-proof mechanism was set at 20%.
kg/cm2, 30kg/cm2, 40kg/
cm2, 60kg/cm2, 80kg/cm2
, 100 kg/cm2, and a similar heating test was conducted. Conventional batteries had no explosion-proof mechanism against sudden external heating, and all of them exploded. Working pressure 40k
Although the explosion-proof mechanism of the batteries below g/cm2 was activated and the electrolyte began to be released before the explosion, it was not possible to prevent the explosion phenomenon.

[0020] In conventional batteries, the lithium negative electrode was crimped onto the inner surface of the battery case, and heat from the outside was directly transmitted to the lithium, reaching the melting temperature of the lithium in a short period of time, leading to the battery exploding. be. When the operating pressure of the explosion-proof mechanism is low, the explosion-proof mechanism is activated and the electrolyte has begun to be released, but since heat from the outside is transmitted through the lithium of the negative electrode, the temperature of the lithium is always higher than the electrolyte. Lithium melted and exploded when thionyl chloride remained inside the battery case.

[0021]

As described above, the present invention makes it possible to provide a lithium thionyl chloride battery that does not burst or explode even when exposed to rapid external heating. In other words, the thionyl chloride lithium battery according to the present invention is not only resistant to increases in internal pressure due to charging, over-discharging, and short circuits, but also to misuse such as throwing the battery into a fire, and preventing it from being placed in a soldering bath for printed circuit boards. It is safe even in the event of an accident such as a fall, and is of great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a thionyl chloride lithium battery in one embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional thionyl chloride lithium battery.

FIG. 3 is a diagram showing a method of battery heating test using a gas burner.

[Explanation of symbols]

1 Negative electrode 2 Side separator 3 Positive electrode 4 Negative electrode current collector 5 Battery case 6 Lid body 7 Small hole 8 Negative terminal 9 Glass seal 10 Liquid injection port 11 Protective separator 12 Bottom separator 13 Electrolyte 14 Positive electrode current collector 15 Positive terminal 16 Explosion-proof groove 17 Test battery 18 Gas burner

Claims (1)

[Claims] Claim 1: A cylindrical thionyl chloride-lithium battery using thionyl chloride as a solvent of an electrolytic solution and a positive electrode active material and lithium as a negative electrode active material, the positive electrode being in contact with the inner surface of a battery case. layer, a separator, a negative electrode configured in the center through the separator, and an explosion-proof mechanism that operates within a battery internal pressure range of 20 kg/cm2 to 80 kg/cm2, and the surface of the negative electrode is located closer to the inner surface of the battery case. A thionyl chloride lithium battery characterized by being separated by 1.5 mm or more.