JP2000164203A - Safety device and manufacture thereof, and secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safety battery having high reliability and capable of realizing instantaneous and perfect disconnection of a conductive passage when abnormal pressure is caused. SOLUTION: In this safety device, a conductive passage 10 is formed on a thin plate 5 formed of a ceramics, a glass and a glass ceramics, and the plate 5 is broken by a pressure difference between both surfaces of the thin plate 5. Curvature radius R of a boundary corner part A formed by a spacer plate 7 and the thin plate 5 is set at 0.1 mm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device that requires a current interruption as a safety device, and particularly to a device in which a rise in pressure inside the device is a problem. In particular, it is an effective safety device for devices requiring a small safety device, such as a rechargeable secondary battery such as a lithium ion battery.

[0002]

2. Description of the Related Art With the spread of electronic devices such as mobile phones, video cameras, and portable information terminals such as notebook computers, the use of high-performance rechargeable secondary batteries such as lithium-ion batteries has been rapidly spreading. ing. FIG. 1 schematically shows the configuration of a lithium ion battery. A positive electrode 3 and a negative electrode 4 are provided in an electrolytic solution 1 (organic solvent) with a separator 2 interposed therebetween, and have a simple configuration in which charging and discharging occur when Li ions move between the positive electrode 3 and the negative electrode 4. A lithium oxide is used for the positive electrode 3 and a carbon compound is used for the negative electrode 4.

[0003] These batteries are highly functional, but when overcharge or short circuit occurs, gas is generated by decomposition of the electrolytic solution 1, the pressure in the batteries rises, and in the worst case, an explosion occurs. There is. Therefore, these batteries are provided with various safety devices.

[0004] These safety devices include a safety valve mechanism current cutoff mechanism. In the safety valve mechanism, a safety valve arranged on the battery surface is opened by the pressure increase in the battery, and the gas in the battery is exhausted to stop the pressure increase. As a current cutoff mechanism, there has been proposed a mechanism that cuts off a conductive path using a rise in pressure of a gas, and a mechanism that cuts off a conductive path using a rise in temperature in a battery caused by a rise in pressure.

A current breaker utilizing a temperature rise has been put into practical use with a simple mechanism utilizing a PTC element. However, a time lag is inevitably caused between the temperature rise and the pressure rise, and the operation becomes unstable as a safety mechanism. There were drawbacks.

For example, as disclosed in Japanese Patent Application Laid-Open No. 9-55197, there is provided a conductive path, a pressure receiving part displaced by the pressure in the battery, and a mechanism for breaking the conductive path by the displacement of the pressure receiving part. Have been proposed.

[0007]

However, the one disclosed in Japanese Patent Application Laid-Open No. 9-55197 requires the above-mentioned mechanisms and components for arranging and connecting them, which complicates the mechanism, and reduces the size and cost. There was a problem in that.

[0008] Portable information terminals such as mobile phones, video cameras, and notebook personal computers are becoming more and more miniaturized in the future, and miniaturization of the battery itself is an urgent issue. Since it is difficult to take it inside, it is a major obstacle to miniaturization.

Further, since it is premised that the safety device operates completely, it is necessary to completely cut off the conductive path formed in the pressure receiving portion.

An object of the present invention is to provide a safety device which can be accommodated in a battery and can easily cope with miniaturization, and has a mechanism which operates instantaneously when the pressure rises. To provide a highly reliable safety device.

[0011]

In order to solve the above problems, according to the present invention, a conductive path is formed on a thin plate made of ceramics, glass, or glass ceramics, and the thin plate is broken by a pressure difference between both surfaces of the thin plate. This is a safety device in which the conductive path formed in the thin plate is broken and the current is cut off, and the spacer plate is integrally joined around the thin plate to reduce the radius of curvature of the boundary corner between the two. 0.1 mm or less.

That is, the above-mentioned thin plate is very thin and therefore difficult to handle as a single unit. Also, in order to form a reference pressure chamber described in detail later, a structure in which a thick spacer plate is integrally provided around the thin plate. At this time, the radius of curvature at the boundary corner between the two is reduced to 0.1 mm or less, so that when a pressure difference occurs, the wire can be reliably broken.

[0013] Further, the present invention provides a method of manufacturing a reference pressure chamber formed by the above-mentioned spacer plate.
By setting the ratio of the minor axis to 1.0 to 1.2, the conduction path can be instantaneously and completely cut off, and a highly reliable safety device can be provided.

Further, the present invention relates to ceramics, glass,
Laminate green sheets made of glass ceramics,
By manufacturing the safety device by integrally firing, the radius of curvature at the boundary between the thin plate and the spacer plate is reduced to 0.1 mm or less, and the device can be manufactured easily and inexpensively.

Further, the present invention is characterized in that a secondary battery is provided with the above-mentioned safety device.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2A is a partially cutaway perspective view of the safety device of the present invention. A spacer plate 7 is integrally provided around a thin plate 5 made of ceramics, glass, or glass-ceramics. A central space of the spacer plate 7 is formed as a reference pressure chamber 6 so as to cover the reference pressure chamber 6. The cover plate 9 is integrally provided. The cover plate 9 has a through hole 9a, in which a closing material 8 such as resin is provided.
Is filled and closed. Further, a conductive path 10 formed by a vapor deposition method or the like is provided on the thin plate 5.

When this safety device is used, for example, a main power supply of a secondary battery is connected to the conductive path 10 and the pressure on the surface of the thin plate 5 opposite to the reference pressure chamber 6 is increased due to overcharging or the like. When the pressure rises and the pressure difference between the reference pressure chamber 6 and the reference pressure chamber 6 exceeds a specified value (hereinafter, referred to as abnormal pressure occurrence),
When the thin plate 5 is broken and the conductive path 10 is broken, the main power supply of the secondary battery can be cut off.

At this time, the thin plate 5 is made of ceramics,
Since it is made of a brittle material such as glass or glass ceramic, it can be reliably broken without plastic deformation to break the conductive path 10.

Here, in the safety device of the present invention, FIG.
As shown in (b), the radius of curvature R of the boundary corner A between the spacer plate 7 and the thin plate 5 is set to 0.1 mm or less, so that the thin plate 5 can be reliably broken. This is because, by setting the radius of curvature R to 0.1 mm or less, a crack is generated from the boundary corner A at the time of occurrence of abnormal pressure, and it can be reliably broken.

Note that, as shown in FIG.
Is not a curved surface, but a C surface, the width C of the C surface is regarded as a radius of curvature, and the same applies to other shapes.

In the case of manufacturing such a safety device, if the reference pressure chamber 6 is formed by press molding or cutting, the radius of curvature R of the boundary corner A is set to 0.1 m.
m or less, and the thin plate 5 cannot be reliably broken. On the other hand, according to the present invention, the curvature radius R of the boundary corner A can be set to 0.1 mm or less by manufacturing the green sheets by lamination as described in detail later.

Further, according to the present invention, the shape of the reference pressure chamber 6 when viewed in a plan view is such that the ratio of the major axis / minor axis is in the range of 1.0 to 1.2, so that the instantaneous conductivity at the occurrence of abnormal pressure is obtained. The road 10 can be cut off and completely cut off. Here, the long diameter is the longest diameter when the reference pressure chamber 6 is viewed in plan, and the short diameter is the shortest diameter. For example, if the reference pressure chamber 6 is square, the major axis is the length of the diagonal,
The minor axis is the length of one side. In this case, the ratio of the major axis / minor axis is about 1.4, which is outside the scope of the present invention.

In the present invention, the thin plate 5 to be broken has a Young's modulus of 60 GPa or more,
By using a material having a bending strength of 000 MPa and adjusting the thickness of the thin plate 5 to 10 to 100 μm, the operating pressure of the safety device is appropriately adjusted, and an instantaneous and complete conduction path when abnormal pressure is generated. 10 cutoffs can be realized.

As a specific material of the thin plate 5, a ceramic such as alumina or zirconia, a glass such as crystallized glass, or a glass ceramic is used. It is preferable to use the same material as the thin plate 5 for the spacer plate 7 and the covering plate 9.

Here, a method of manufacturing the safety device of the present invention will be described.

A slurry is prepared by mixing a ceramic powder such as alumina or zirconia, or a glass or glass ceramic powder with an organic binder, a plasticizer and a solvent. As shown in FIG. 3, this slurry is thinned by a general doctor blade method, a calendar roll method, a rolling method, or a press forming method to form a thin green sheet 5 ′ forming a thin plate and a thick green sheet 5 ′ forming a spacer plate. A green sheet 7 'and a green sheet 9' forming the cover plate 9 are produced.

The thin and thick green sheets are not limited to the above-mentioned solvent-based slurry, but may be made of a ceramic powder using an organic binder, a plasticizer, a dispersant, or the like.
A water-soluble slurry mixed with ion-exchanged water may be used. Further, a thick sheet-shaped molded product may be used by laminating thin green sheets.

The thick green sheet 7 'thus obtained is formed by punching a through hole 6' serving as the reference pressure chamber 6 and the green sheet 9 'is formed by punching a through hole 9a' using a mold. Then, a thin green sheet 5 ', a thick green sheet 7' having a through hole 6 ', and a thick green sheet 9' having a fine through hole 9a 'are laminated and integrated as shown in FIG. 800 ° C
The firing is performed integrally in the above air atmosphere.

After the thin plate 5, the spacer plate 7, and the covering plate 9 are integrally sintered in this manner, a conductive path 10 is formed on the thin plate 5, and a through hole 9a penetrating to the reference pressure chamber 6 is formed by a resin. The safety device of the present invention can be obtained by closing with the closing member 8 such as.

Note that the through holes 9a are formed beforehand.
Finally, by closing this with the closing material 8, breakage during the manufacturing process can be prevented, and the pressure in the reference pressure chamber 6 can be set to the atmospheric pressure.

As another manufacturing method, a ceramic sheet such as alumina or zirconia, or glass or glass ceramic powder is added, and after adding a binder, a green sheet forming a spacer plate 7 and a thin plate 5 is formed by a press method. And fired integrally in an air atmosphere of 800 ° C. or higher. After that, the reference pressure chamber 6 may be covered with the cover plate 9, the thin plate 5 may be processed to a desired thickness, and then the conductive path 10 may be formed on the thin plate 5.

The conductive path 10 is made of, for example, Cu, Ni,
It is formed from a metal such as Al, Au, Ag, Pd or an alloy thereof, and is formed by a known plating method, sputtering method, vapor deposition method,
It is formed by a printing method.

Further, since the above-mentioned safety device is very small, a large number of devices can be manufactured simultaneously by a multi-cavity method. As shown in FIG. 4, one green sheet 7 'is provided with a large number of through holes 6', and similarly, a green sheet 9 having a large number of through holes 9a 'and a thin green sheet 5' are laminated. Then, after the conductive paths 10 are formed by integrally firing, a large number of pieces can be manufactured at the same time by cutting.

As described above, in the manufacturing method of the present invention, at least the thin plate 5 and the spacer plate 7 are laminated and then integrally fired after the green sheet is laminated, so that the radius of curvature R of the boundary corner A between them is 0.1 mm. The thickness can be reduced to the following, whereby the thin plate 5 can be reliably broken.

In the above embodiment, the structure in which the cover plate 9 is provided and the thin pressure plate 6 is provided with the reference pressure chamber 6 in one side is shown. However, in another embodiment, only the thin plate 5 and the spacer plate 7 are provided. To form a safety device, and the thin plate 5 can be broken by a pressure difference between both surfaces.

Next, an embodiment of a secondary battery using the safety device of the present invention will be described.

FIG. 3 shows a secondary battery incorporating the safety device of FIG. 2 (a). The positive electrode 3 serving as an internal electrode is connected to an output unit 12 serving as an external electrode that is electrically insulated from the exterior unit 11.
The negative electrode 4, which is the other internal electrode, is electrically connected to the exterior unit 11 (not shown). In an actual battery, the positive electrode 3 and the negative electrode 4 are stacked in multiple layers with the separator 2 interposed therebetween, but are not shown in the figure.

The safety device 13 according to the present invention is installed so as to be electrically connected between the output section 12 and the positive electrode 3. Note that there is no problem even if the safety device 13 is installed on the negative electrode 4 side.

The operation of the safety device 13 of the present invention is roughly as follows. When the battery is overcharged for some reason, gas is generated as described above, and the pressure in the battery starts to increase. When the internal pressure of the battery becomes a certain value or more, the thin plate 5 of the safety device 13 is broken, the conductive path 10 formed on the thin plate 5 is broken, and the gas stops because charging stops. The above pressure rise can be prevented. The thickness and material of the thin plate 5 may be appropriately selected from the pressure to be broken and the allowable size of the safety device 13.

[0041]

EXAMPLE 1 Here, an example of manufacturing a safety device using alumina powder will be described.

A water-soluble slurry is prepared by mixing an alumina powder with an acrylate-based binder as a binder and hexylene glycol as a plasticizer, a dispersant, and ion-exchanged water. A thick alumina green sheet was produced. This thick green sheet has a reference pressure chamber 6
The through-hole 6 'and the fine through-hole 9a' for forming the above are punched and formed by a mold. Here, a mold having a desired shape after firing is used.
A 3 mm mold was used.

Thereafter, a thin green sheet 5 ', a green sheet 7' having a through hole 6 ', and a fine through hole 9a'
Respectively, as shown in FIG. 3 stacking the green sheet 9 'having, formed integrally, 60 ℃, 50kgf / cm ²
And then calcined in an air atmosphere at 1570 ° C. Thus, the structure of the safety device of the present invention was obtained.

As a comparative example, the spacer plate portion and the thin plate portion of the safety device were simultaneously molded by using a well-known press molding method using a mold whose C surface was adjusted, and then the thickness processing of the thin plate portion was performed. went.

As described above, the spacer plate 7
The radius of curvature R at the corner A of the boundary between
A safety device adjusted from 1 to 0.20 mm was manufactured, and the relationship with the probability of destruction was examined. In addition, all are thin plates 5
Was 50 μm in thickness.

The probability of breakage was calculated by putting the prepared safety device into a pressure vessel, gradually applying pressure, and calculating the probability that the thin plate 5 would break when a pressure of up to 7 kg / cm ² was applied. The pressure was set to a pressure rise value expected as an abnormal pressure in the secondary battery.

In a similar manner, the shape of the reference pressure chamber 6 formed by the spacer plate 7 when viewed in plan is a circle (major axis / minor axis = 1.0) and an ellipse (major axis / minor axis = 1.1). ,
1.2, 1.3, 1.4), square (major axis / minor axis = 1.
4), hexagon (major axis / minor axis = 1.1, 1.2, 1.3,
1.4), and the relationship with the failure probability was examined.

As shown in Table 1, the radius of curvature R at the boundary corner between the spacer plate 7 and the thin plate 5 was set at 0.
Samples (A-4, 5) exceeding 1 mm were produced by press molding and had a low probability of breaking of 60% or less.
On the other hand, the other samples were manufactured by laminating green sheets and had a radius of curvature R of 0.1 mm or less, so that the probability of destruction could be increased to 70% or more.

From this, it can be said that the radius of curvature R needs to be 0.1 mm or less, and it is more desirable that the radius is smaller. Advantageously, the manufacturing method of the safety device is based on lamination of green sheets.

The shape of the reference pressure chamber 6 when viewed in a plan view is as follows when the ratio of the major axis / minor axis is 1.2 or less (Sample A-
1-3, B-1 and D-1 and 2) have a 100% failure probability. In addition, even if it was other shapes, if it was within the above-mentioned ratio, it would not affect the fracture probability no matter what square shape it was.

[0051]

[Table 1]

Embodiment 2 Next, the relationship between the material properties and the breakage probability will be described.

In the same manner as in Example 1, A to F in Table 2 were used.
A safety device was manufactured by laminating green sheets using ceramic powders such as alumina and zirconia or glass and glass ceramic powders shown in FIG. The firing temperature was set to an appropriate temperature for each material.

The thickness of the thin plate 5 was adjusted to 8 to 150 μm, the shape of the reference pressure chamber 6 was a circle having a diameter of 3 mm, and the major axis / minor axis was 1.0. The diameter of the through hole 9a communicating with the reference pressure chamber 6 was set to 0.3 mm, and the through hole 9a was shielded with resin.

The safety device thus manufactured is put into a pressure vessel, and a pressure up to 7 kg / cm ² is gradually applied.
The probability of failure was calculated. The pressure was set to a pressure rise value expected as an abnormal pressure in the secondary battery.

As shown in Table 3, the materials E-1 to E-9 in which the Young's modulus of the material is 60 GPa or less and the bending strength is 80 MPa or less are stable due to breakage during handling if the thickness is small. Although it could not be manufactured, it was broken even if the thickness was large, but the failure probability was low and stable breakdown could not be obtained. This is because if the Young's modulus is low, stable destruction cannot be obtained due to bending when pressure is applied.

Further, C having a bending strength exceeding 1000 MPa
In -1 to C-6, no breakage occurred because the strength was too high.

Therefore, the material used for the thin plate 5 has a Young's modulus of 60 GPa or more and a bending strength of 80 to
1000 MPa is desirable.

Regarding the thickness of the thin plate, A-1, B-1, C-1, D-
1, E-1 and F-1 were susceptible to minute defects due to their small thickness, and could not be crushed or had a low probability of breaking because the pressure was leaking into the space.

Conversely, as the thickness increases, the required breaking pressure increases and the breaking probability decreases. Here, the thickness of the thin plate 5 is preferably 10 to 100 μm in consideration of the probability of breakage and destruction during handling, and more preferably 25 to 75 μm in consideration of use as a safety device.

[0061]

[Table 2]

[0062]

[Table 3]

When the safety device of the present invention was evaluated for operation using a rechargeable secondary battery as a safety device, a 100% break at 7 kg / cm ² was confirmed. It was something to satisfy. In addition, even in the damaged state, the conductive portion 10 was surely shut off.

Although an example has been described in which the safety device of the present invention is used as a safety device for a rechargeable secondary battery, the present invention is not limited to this, and the safety device of the present invention can be used for various pressure sensing type safety devices. By adjusting the thickness of the thin plate, a safety device that operates at a desired pressure can be obtained.

[0065]

According to the present invention, there is provided a safety device in which a conductive path is formed on a thin plate made of ceramics, glass, and glass ceramics, and the thin plate is broken by a pressure difference between both surfaces of the thin plate. By setting the radius of curvature at the boundary between the spacer plate and the thin plate to be 0.1 mm or less, it is possible to instantaneously and completely cut off the conductive path when abnormal pressure occurs, and to provide a highly reliable safety device. be able to.

The present invention also provides a safety device by laminating green sheets made of ceramics, glass, and glass ceramics and then integrally sintering them to reduce the radius of curvature at the boundary corners and to manufacture the safety device at low cost. It becomes possible.

Further, in the secondary battery incorporating the safety device of the present invention, the size can be easily reduced, and the variation in operation over a long period can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a general secondary battery.

2A is a partially cutaway perspective view showing a safety device of the present invention, and FIGS. 2B and 2C are enlarged sectional views of a portion A in FIG. 2A.

FIG. 3 is a perspective view showing a manufacturing method of the safety device of the present invention.

FIG. 4 is a plan view of a green sheet showing a manufacturing method of the safety device of the present invention.

FIG. 5 is a partially broken sectional view of a secondary battery using the safety device of the present invention.

[Explanation of symbols]

 1: Electrolyte 2: Separator 3: Positive electrode 4: Negative electrode 5: Thin plate 6: Reference pressure chamber 7: Spacer plate 8: Closure material 9: Covering plate 9a: Through hole

Claims (6)

[Claims] 1. A safety device in which a conductive path is formed on a thin plate made of ceramics, glass, and glass ceramics, and the conductive path is broken by breaking the thin plate by a pressure difference between both surfaces of the thin plate. A safety device, wherein a spacer plate is integrally provided around the thin plate, and a radius of curvature at a boundary corner between the spacer plate and the thin plate is set to 0.1 mm or less. 2. The safety device according to claim 1, wherein a side opposite to the thin plate of the spacer plate is covered with a covering plate, and a reference pressure chamber is provided. 3. The safety device according to claim 2, wherein the ratio of the major axis / minor axis in the plan view of the reference pressure chamber is 1.0 to 1.2. 4. A thin plate, a spacer plate having a reference pressure chamber, and a coating plate are each made of ceramics.
A method for manufacturing a safety device, comprising a process of forming green sheets of glass and glass ceramics, laminating each other, and integrally firing. 5. The method for manufacturing a safety device according to claim 4, wherein a through hole is formed in a portion of said cover plate corresponding to the reference pressure chamber, and said through hole is closed after integral firing. 6. A secondary battery in which a case is provided with an electrolyte and a plurality of internal electrodes immersed in the case, wherein the internal electrode and the external electrode are connected to each other. A secondary battery to which the safety device according to any one of Items 1 to 3 is connected.