JPH0650940Y2 - Explosion-proof lithium battery - Google Patents

Description

[Detailed Description of the Invention] << Industrial Application Field >> This invention relates to an explosion-proof structure of a lithium battery, and in particular, extends the practical temperature range of the explosion-proof mechanism so that reliable breaking characteristics can be obtained and at the time of high temperature storage. The present invention relates to a structure capable of improving liquid leakage resistance.

<< Prior Art >> Generally, a lithium battery has a high risk of explosion due to an internal short circuit due to misuse or the like due to its high electric energy density.

Therefore, this type of battery has an explosion-proof structure,
For example, as shown in Japanese Utility Model Laid-Open No. 56-26863, a diaphragm is sandwiched between a sealing plate having a valve hole and a terminal plate having a gas vent hole, and the peripheral edge of the sealing plate is caulked to the peripheral edge of the terminal plate, and A structure is adopted in which a cutting edge protruding by cutting and raising from the gas vent hole is made to face the diaphragm, and this assembly is airtightly crimped to the opening of the battery case via a sealing gasket. .

According to this structure, gas is generated inside the power generation element inside the case due to an internal short circuit and the like, and when the internal pressure rises rapidly, the diaphragm expands, and the cutting edge pierces it to cause internal The gas is released to the outside through the gas vent hole so that safety is maintained.

However, the explosion-proof structure having this structure has the following problems.

<< Problems to be Solved by the Invention >> That is, the diaphragm is a composite member of a metal thin plate and a synthetic resin thin plate, and is sandwiched between the lower surface of the peripheral edge of the terminal plate and the upper surface of the peripheral edge of the sealing plate. Although the sealability between the peripheral edge of the terminal plate and the sealing plate is ensured, polyethylene and polypropylene are used as the material of the synthetic resin thin plate, which is insufficient in terms of heat resistance and durability. .

In other words, due to the softening point of polyethylene and polypropylene, 60 ° C is a practical range in the high temperature range, and the thickness of the synthetic resin thin plate used as the diaphragm is thin, so at temperatures above the upper limit of this range. When it is used, it is strongly affected by the softening, and it does not operate even if it reaches a predetermined pressure due to softening, or conversely, it causes an operation failure such as operating before reaching the predetermined pressure.

Further, in the diaphragm using the composite member of the above metal thin plate and synthetic resin material, if the tightening pressure at the time of caulking is high, deformation may occur, so if the caulking pressure is reduced, the liquid leakage resistance decreases, Internal resistance increases,
The storage performance of the battery was also adversely affected.

That is, when this type of diaphragm is crimped to the sealing plate with a sufficient clamping pressure to secure liquid leakage resistance, as shown in FIGS. 5 (a) and 5 (b), the peripheral edge of the diaphragm D is More wrinkles are generated on the inner side b than the crimped part a, and the extension occurs. As a result, the positional relationship with the cutting edge facing the diaphragm is different from that at the time of designing, and there is a drawback that the explosion-proof mechanism does not operate at a predetermined pressure due to the expansion of the entire diaphragm.

The present invention solves the above problems, and by adopting a combination of cellophane and a thin metal plate as the diaphragm, the storage performance of the battery is improved and the breaking operation is reliably performed when the internal pressure reaches a predetermined pressure. It is an object of the present invention to provide an explosion-proof lithium battery having a wide operating temperature range on the high temperature side.

<Means for Solving the Problem> In order to achieve the above-mentioned object, the present invention provides a valve chamber formed by a sealing plate having a valve hole in the center and a terminal plate having a gas vent hole, and While always closing the valve hole,
Explosion proof provided with a diaphragm facing a cutting blade protruding from the gas vent hole, and a sealing gasket that is crimped to the inner circumference of the opening of the battery case and hermetically holds the peripheral edges of the sealing plate and the terminal plate. The lithium battery is characterized in that the diaphragm is composed of a composite member composed of a thin metal plate and cellophane.

<Operation> When the gas pressure inside the battery rises, the diaphragm expands, breaks through the cutting edge, and releases the gas inside, which is the same as before, but the cellophane in the composite member forming the diaphragm is at a high temperature. It has excellent thermal stability and improves reliability when operating at high temperatures. Further, the rupture property of cellophane is better than that of the conventional synthetic resin regardless of the temperature condition, and the operation stability is excellent.

Further, since cellophane does not deform even if it is crimped with a sufficient clamping pressure to secure liquid leakage resistance, the positional relationship with the cutting blade after crimping work is the same as the initial design.

<< Embodiment >> An embodiment of the present invention will be described below in detail with reference to the drawings.

1 and 2 are cross-sectional views showing the essential parts of an explosion-proof lithium battery according to the present invention.

In the figure, reference numeral 1 denotes a cylindrical metal outer can with an upper opening filled with a power generating element (not shown), and 2 is fixed to an inner peripheral portion of the opening of the metal outer can 1 through a sealing gasket 3. It is a dish-shaped terminal plate.

A sealing plate 4 made of a metal plate having a valve hole 4a formed in the center thereof is arranged below the terminal plate 2 to form a valve chamber B having a predetermined space therebetween, and the valve hole 4a is It is hermetically closed by a diaphragm 5 stacked on the upper surface of the sealing slope 4.

The terminal board 2 is composed of a convex portion 2a and a flange portion 2b formed in a flat plate shape on the peripheral edge of the convex portion 2a, and has gas vent holes 2c at a plurality of positions on the peripheral edge of the convex portion 2a. The cutting edges 2d are cut and raised inside the gas vent hole 2c, and the tips of the cutting edges 2d face the peripheral edge of the central portion of the diaphragm 5.

The sealing gasket 3 is made of polypropylene, polyethylene or the like, and has a ring-shaped caulking portion 3a, an instruction plate portion 3b at the lower part of the caulking portion 3a, which supports the sealing plate 4, and an instruction plate portion 3b having an open center. The partition wall 3c extending in a ring shape is provided on the lower peripheral edge of the plate portion 3b,
The sealing plate 4 and the terminal plate 2 are stacked on the support plate portion 3b, fitted into the outer can 1, and the outer can of the outer can 1 is caulked to hermetically seal the outer and inner peripheries. It is like this.

The sealing plate 4 is bent at the upper peripheral edge of the valve hole 4a and the outer peripheral portion 4b so as to be raised by one step. With this structure, the peripheral edge of the diaphragm 5 is fixed while being caulked and fixed.

The diaphragm 5 is a cellophane 6 arranged in direct contact with the peripheral edge of the valve hole 4a of the sealing plate 4 and the outer peripheral portion 4b.
And a metal thin plate 7 made of aluminum or the like laminated in close contact with the upper surface of cellophane 6, or a composite member further laminated with cellophane in close contact with the upper surface thereof, the periphery of which is ring-shaped. It is fixed by caulking inside the peripheral portion of the sealing plate 4 via a gasket 8.

As cellophane 6 in the composite member, of course, a moisture-proof cellophane that is impermeable to water vapor is used.

The cellophane 6 has no melting point and carbonizes at about 190 ° C., whereas the synthetic resin used as a conventional diaphragm, that is, polyethylene has a melting point of 105 to 1
The melting point of polypropylene is slightly higher than this, 160-170 ° C, but the softening point is slightly lower, 150 ° C.
Before and after.

Further, the metal thin plate 7 has a function of backing up the back surface of the cellophane 6 and holding it at a predetermined strength.

Therefore, as the resin material in the composite member, cellophane 6
By using, it is possible to raise the upper limit of the operating temperature, and since there is no softening accompanying the temperature rise, the fracture state in the high temperature range becomes stable.

Further, cellophane 6 is stable against the breaking pressure and has a characteristic that it is surely broken within a predetermined pressure range, and the breaking pressure distribution becomes smaller than that in the conventional case as shown in the graph of FIG. 4 described later. .

In addition, conventional polyethylene and polypropylene increase the compression strength in order to increase the tightening strength during crimping,
When the molded product shape was changed significantly and compressed, deformation such as elongation was likely to occur, whereas cellophane 6 did not deform due to this type of tightening, so even if the tightening strength was increased, The positional relationship of will not be distorted and the original design state can be maintained.

Further, as a result, liquid leakage resistance is improved and storage performance is improved.

In the lithium battery having the above structure, when the internal gas pressure increases, the pressure directly acts on the diaphragm 5 through the valve hole 4a, and as a result, the diaphragm 5 expands upward with the peripheral edge as a base point. Due to this expansion, the cutting edges 2d pierce the diaphragm 5 and, as shown in FIG.
A plurality of breaks corresponding to the number of 2d are formed, and the gas is discharged from the break through the gas vent hole 2c to the outside.

Explosion-proof lithium battery with the above configuration and conventional structure (using polypropylene and aluminum plate for diaphragm)
When the number of leaked liquid and the internal resistance of the lithium battery of Example 1 were stored at a high temperature of 60 ° C., the results shown in Table 1 and the graph of FIG. 3 were obtained. The batteries used in the test were CR
6 · H.

Further, as a result of comparing the temperature dependence of the number of malfunctions for 50 batteries, the results shown in Table 2 below were obtained.

From this result, it can be easily understood that cellophane has good high-temperature characteristics and can reduce the number of malfunctions compared to the conventional case.

Furthermore, from the graph of FIG. 3, it can be seen that the increase rate of the internal resistance of the battery using the diaphragm of the present invention is extremely small, whereas the increase rate of the conventional product is high, and the sealing performance of the diaphragm of the present invention is high. Shows.

Similarly, as a result of examining the number of leaked liquids after storage for 50 days and 100 days when caulking pressure was applied to operate the explosion-proof mechanism reliably, the results shown in Table 3 below were obtained.

The above results indicate that when cellophane is used, the diaphragm itself does not deform even if it is crimped with a clamping pressure sufficient to maintain the leakage resistance. This is because it can be fixed with. And this suggests that the diaphragm of the present invention has a sufficient sealing effect.

Next, FIG. 4 shows the case where the diaphragm of the present invention is used,
It shows the relationship between the operating pressure and the number of fractures at a temperature of 20 ° C when a diaphragm made of a conventional synthetic resin material (polypropylene) is used, and shows the variation with the maximum number of fractures at an operating pressure of 30kg / cm ² . While the conventional type has a wide spread of ²⁰ to 40 kg / cm ² , the present invention has a small variation in operation, which is 25 to 35 kg / cm ² .

The above results suggest that the breakability of celloan, which is the material forming the diaphragm of the present invention, is good.

<< Effect of Device >> As described in detail in the above embodiments, the explosion-proof lithium battery according to the present invention has the following effects.

By combining the metal thin plate and cellophane, it is possible to reduce the rate of occurrence of liquid leakage and the rate of increase in internal resistance, as is apparent from the results shown in the tables and graphs, and improve the storage performance of the battery. Variation in breaking pressure is small,
Stable breaking performance can be obtained.

Further, according to this invention, the practical temperature range of the explosion-proof mechanism at high temperature can be expanded as compared with the conventional case.

Furthermore, cellophane does not deform even if it is crimped with a sufficient clamping pressure to secure liquid leakage resistance, so the positional relationship with the cutting blade after crimping work is the same as when the design was originally made, and accuracy is improved. To do.

[Brief description of drawings]

FIG. 1 is a sectional view showing an essential part of an explosion-proof lithium battery according to the present invention, FIG. 2 is a sectional view showing an essential part of the lithium battery showing a degassing state, and FIG. 3 is a lithium battery having a conventional explosion-proof structure. Fig. 4 is a graph comparing the relationship between the number of days of storage and the internal resistance of the lithium battery of the present invention, and Fig. 4 compares the relationship between the breaking pressure and the number of breaking of the lithium battery having the conventional explosion-proof structure and the lithium battery of the present invention. A graph and FIG. 5 are explanatory views showing deformations when a diaphragm made of a conventional synthetic resin material is crimped with a predetermined clamping pressure. 1 ... Exterior can (case), 2 ... Plate-shaped terminal plate 2c ... Gas vent hole, 2d ... Cutting edge 3 ... Sealing gasket, 4 ... Sealing plate 5 ... Diaphragm, 6 ... Cellophane 7 ... … Metal sheet

Claims (1)

[Scope of utility model registration request] 1. A valve chamber formed by a sealing plate having a valve hole formed in the center and a terminal plate having a gas vent hole, which constantly closes the valve hole and protrudes from the gas vent hole. In an explosion-proof lithium battery comprising a diaphragm facing the cutting edge and a sealing gasket that is crimped to the inner circumference of the opening of the battery case and airtightly holds the peripheral edges of the sealing plate and the terminal plate: An explosion-proof lithium battery comprising a composite member composed of a thin metal plate and cellophane.