JPH0337956A - Organic electrolyte battery - Google Patents

Abstract

PURPOSE:To steadily operate a gas vent valve at a specified pressure over a wide temperature range by forming the vent valve in the form of projection so as not to be in contact with the periphery of a vent hole. CONSTITUTION:A vent hole 11 is installed in the flange of a sealing plate 8 formed in the shape of a cap, and a vent valve 12 is heat-bonded in the periphery of the vent hole 11. The vent valve 12 is formed in the form of projection so as not to be in contact with the periphery of the vent hole 11. Standing resin in the vent hole caused by resin flow produced by melt bonding of the vent valve 12 to the sealing plate 8 is avoided and valve operation pressure is stabilized. By forming the projection in the vent valve, a pressure receiving area is widened over the whole area of the projection inner surface, and valve operation pressure is lowered in spite of the same vent hole shape. The vent valve is steadily operated over the wide temperature range and internal pressure can be released to avoid the breakage of a can.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a valve body for an organic electrolyte battery having an explosion-proof mechanism.

[Conventional technology]

Organic electrolyte batteries that use light metals such as lithium and sodium as negative electrode active materials are excellent in high voltage, high energy density, and long-term reliability, and the demand for them is on the rise.

Such organic electrolyte batteries are required to have a stable seal over a long period of time, especially airtightness, in view of their performance, so they are sealed with extremely high airtightness. Due to such an airtight structure, if gas is generated inside the battery during charging due to internal short circuit, external short circuit, leakage current, etc., the internal pressure of the battery increases and there is a problem that the outer can may burst.

For this reason, organic electrolyte batteries have conventionally been provided with the following explosion-proof mechanism.

(2) An explosion-proof mechanism in which a part of the outer can is made thin, and when the internal pressure of the battery rises, the thin wall part ruptures and gas escapes to the outside before the entire outer can ruptures.

(2) An upper plate material which is curved upward near the center, has a sharp protrusion formed on the inner surface of the curved top, and has a gas vent hole formed near the center, and is placed opposite to this upper plate material. a lower plate material whose central portion is curved downward and has a gas vent hole formed near the center; and a thin metal plate, synthetic resin, or synthetic rubber placed between the upper and lower plate materials in a valve chamber between the upper and lower plate materials. There is an assembly sealing plate that has an explosion-proof mechanism and is composed of a thin plate of 1, or a composite thin plate made by laminating both of them. When the battery is assembled by airtightly attaching the sealing plate (2) to the upper opening of the outer can, and the internal pressure of the battery increases, the thin plate disposed in the valve chamber between the upper and lower plates bulges upward.
Since it contacts the sharp protrusion attached to the inner surface of the upper plate and ruptures, the gas inside the outer can escapes through the gas vent hole in the lower plate, the damaged area of the thin film, and the gas vent hole in the upper plate.

However, in the above explosion-proof mechanism (①), for example, when forming a thin wall part on an iron exterior can, the wall thickness is reduced to zero due to processing accuracy.
．． At present, it is only possible to process the thickness to about 0.08 to 0.15 mm. Therefore, the internal pressure of the battery is 50 to 70 kgf.
There was a problem that the explosion-proof mechanism would not operate unless the high pressure of /cJ was reached.

The assembly sealing plate with the above-mentioned explosion-proof mechanism (■) requires attaching a sharp protrusion to the curved inner surface of the upper plate material and sandwiching a thin plate between the upper and lower plate materials, making it extremely complicated to manufacture. Not only that, but the cost increases due to an increase in the number of parts. Furthermore, fix the current collector rod to either the positive or negative electrode,
When creating an electrode group (power generation element) by spirally winding positive and negative electrodes and a separator around this current collector rod as a winding axis, it becomes very difficult to electrically connect the current collector rod and the assembled sealing body. There was a problem that it was difficult to manufacture batteries.

Therefore, the present inventors previously applied for patent application No. 63-044188.
, patent application 1983-160942, patent application 1983-139
517, which has a valve body that constantly closes the gas vent hole formed in the sealing plate, and the valve body is made of a composite coating made by laminating a polyethylene or polypropylene film that has adhesive properties to metal and a thin metal plate. The present invention has proposed an organic electrolyte battery having an explosion-proof mechanism fused around the gas vent hole.

[Problem to be solved by the invention]

FIG. 3 shows an enlarged sectional view of the main parts of a battery according to the prior art.

In this case, the valve operating pressure is determined by the area of the gas vent hole 11 and the valve body 2.
It is determined by the balance between the strength of the fusion bond between 2 and the sealing plate 8.

In order to operate at low pressure, the diameter of the gas vent hole 11 may be increased and the fused area between the valve body 22 and the sealing plate 8 may be reduced, but due to the structure of the battery, the outer diameter of the gas vent hole 11 is 2 mm.
The extent is the limit, and the fused area is also limited to the valve body 22 and gas vent hole 1.
From the viewpoints of alignment accuracy in step 1, dissipation of electrolyte from inside the battery through the fused portion, and prevention of intrusion of moisture etc. from outside the battery, the distance from the periphery of the gas vent hole to the outer periphery of the valve body is set at 1.
I couldn't make it smaller than that. Therefore, in order to obtain a low valve operating pressure at a relatively low temperature with this structure, a highly accurate technique is required, which is not industrially practical. - The variation in the valve operating pressure is thought to be caused by the cast resin 24 flowing into the periphery of the gas vent hole 11 when the valve body 22 is fused to the sealing plate 8. Valve operation begins when the valve body 22 begins to peel off at the periphery of the gas vent hole 11. If a large amount of the cast resin 24 flows into this portion, the adhesive strength will increase and the valve operating pressure will increase.

If it is less, the opposite is true. For the resin of the valve body, a material with low flowability when melted is selected from the viewpoint of preventing contamination of the manufacturing environment and deterioration of the appearance of the battery. It flows into the hole. It is thought that this difference in amount causes variations in valve operating pressure, but controlling this also requires highly accurate technology and is not industrially practical.

According to the above-mentioned explosion-proof mechanism, when heat is generated due to an increase in battery internal pressure due to an internal short circuit or an external short circuit, the resin film of the valve element melts and stable valve operation is performed at low pressure. If the battery internal pressure rises due to heat generation that does not reach the melting point of the resin film of the valve body, that is, valve operation at a relatively low temperature, the pressure is high and the variation is large, and the battery may burst or catch fire before the valve operates. There was a risk of causing

The present invention has been made to solve the above-mentioned conventional problems, and aims to provide an organic electrolyte battery having an explosion-proof mechanism that operates stably at a desired pressure over a wide temperature range from low to high temperatures.

[Means to solve the problem]

The present invention comprises a sealing plate having a gas vent hole, and a valve body made of a composite coating made by bonding a polyethylene or polypropylene film with adhesive properties to metal and a thin metal plate, and the valve body has a gas vent hole. An organic electrolyte battery having an explosion-proof mechanism that is fused around the gas vent hole so as to always close the valve body, the valve body having a convex portion formed so as not to come into contact with the periphery of the gas vent hole. This is an organic electrolyte battery characterized by the following.

[For production]

According to the present invention, since the valve body does not come into contact with the periphery of the gas vent hole, even if the resin is flowed when the valve body and the sealing plate are fused together, it does not accumulate on the periphery of the gas vent hole, thereby stabilizing the valve operating pressure. can be converted into On the other hand, by forming the convex part, the pressure receiving part of the battery internal pressure, which in the conventional structure had the same area as the gas vent hole, is expanded to cover the entire inner surface of the convex part, so even with the same gas vent hole shape, the valve operating pressure can be lowered.

〔Example〕

Hereinafter, an example in which the present invention is applied to a cylindrical lithium battery having a diameter of 17.0+u and a total height of 33.5 mm will be described with reference to FIGS. 1 and 2.

1 in the figure is a bottomed cylindrical iron outer can that also serves as a negative electrode terminal, and an insulating paper 2 is arranged at the bottom of this outer can 1. Inside the outer can 1 are a lithium negative electrode 3 and a separator 4 made of a polypropylene nonwoven fabric impregnated with an electrolyte.
An electrode group 6 as a power generation element is housed in which a manganese dioxide positive electrode 5 is spirally wound, and a positive current collector rod 7 is placed in the center of the electrode group 6 so as to be in contact with the positive electrode 5 of the electrode group 6. is inserted into. Note that the negative electrode 3 of the electrode group 6 is connected to the outer can 1 via a lead wire (not shown). Further, a sealing plate 8 made of SUS 304 with a thickness of 0.5 mm, for example, which also serves as a positive electrode terminal, is airtightly attached to the upper opening of the outer can 1 via an insulating packing 9 made of polypropylene.

This sealing plate 8 has a cap shape, and a connection lead plate 10 having a cylindrical portion in the center is attached to the lower surface around the protrusion by welding or the like. The upper end of the current collector rod 7 is fitted into the cylindrical portion of the connection lead plate 1O.
0 to the sealing plate 8. The flange of the cap-shaped sealing plate 8 has a diameter of, for example, 1.5 mm.
A gas vent hole 11 is opened in the door. A valve body 12 is thermally bonded to the sealing plate 8 around the gas vent hole 11. This valve body 12 is connected to the sealing plate 8 as shown in FIG.
Modified high-density polyethylene in which 5% by weight of maleic anhydride is graft-polymerized onto polyethylene that is placed on the side and thermally bonded (melt flow lay according to JIS K6760)1.
The valve body 12 is composed of a composite thin film of a 75 μm thick thermal adhesive film 12a made of 2 g/cj, Vicat softening point 128° C. according to J I SK6760, and a 40 μm thick metal thin film 12b made of SUS 304. ing. Further, the valve body 12 is formed with a convex portion so as not to come into contact with the periphery of the gas vent hole 11.

Here, regarding the lithium battery of this example, the rated output is 12
The battery was charged with a constant current of 300+aA using a V power source, and the voltage value and the change in battery outer wall temperature over time were investigated when forced overdischarge was performed. As a result, characteristic diagrams shown in FIGS. 4 and 5 were obtained. Note that FIG. 4 shows the results of charging, and FIG. 5 shows the results of forced overdischarge. A in the figure shows a voltage change curve, and B shows a battery outer wall temperature change curve.

When the valve operates during charging, electrolyte leaks out, so
Battery resistance increases rapidly. During that time, the temperature of the outer wall rises and the voltage rises, but the battery resistance exceeds 40 Ω and exceeds 6□EEi[[(7
) fllGl: tlka, ah, □27□, 4 system! In this range, a few mAL will not flow.

Therefore, the outer wall temperature decreases. Although FIG. 4 only shows the charging time up to 5 hours, there was no change for the next 15 hours.

Similarly, in the case of forced overdischarge, the battery resistance increases rapidly after the valve is activated, and the current is regulated to 12V, which is the rated output of the power supply, and the current only flows by a few mAL. Although FIG. 5 only shows the discharge time up to 10 hours, there was no change for the next 20 hours.

While the softening point of the resin of the valve body used in the battery of the present invention is 126°C, the temperature of the outer wall of the battery when the valve is activated is approximately 30°C during charging.
℃, and about 85 ℃ during forced overdischarge, indicating that valve operation occurs even at relatively low temperatures, and battery safety can be ensured.

〔Effect of the invention〕

As detailed above, according to the present invention, it is easy to manufacture and has excellent airtightness, and furthermore, stable valve operation occurs when internal pressure rises in a wide temperature range from low to high temperatures, causing damage to external cans etc. Therefore, it is possible to provide an organic electrolyte battery that is inexpensive, safe, and has high long-term reliability.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a cylindrical lithium battery showing an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view of the main part of the battery of the above embodiment, and FIG. Figures 4 and 5 show the length of 300 m in a cylindrical lithium battery according to an embodiment of the present invention.
FIG. 3 is a characteristic diagram showing the elapsed time during charging and forced overdischarge of battery A, and changes in battery voltage A and battery outer wall temperature B. 1... Exterior can 6... Electrode group 7... Current collector rod 8... Sealing plate 11... Gas vent hole 12... Valve body 12a... Adhesive filler 12b... Metal thin plate 22... Valve body 24... Casting resin lume

Claims (1)

[Claims] It consists of a sealing plate having a gas vent hole, and a valve body made of a composite coating made of a thin metal plate and a polyethylene or polypropylene film that has adhesive properties to metal, and the valve body is arranged around the gas vent hole. An organic electrolyte battery having an explosion-proof mechanism in which the gas vent hole is fused so as to be always closed, characterized in that a convex portion is formed so that the valve body does not come into contact with the periphery of the gas vent hole. organic electrolyte battery.