JP2001176496A - Safeguard device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable safeguard device, ensuring instantaneous disconnection of a conductive passage at a stable pressure value during the generation of abnormal pressure. SOLUTION: The safeguard comprises a cylindrical spacer member 1, on the upper and lower faces of which an upper plate 3, having a conductive passage 4 on the surface and a lower plate are respectively mounted for sealing an internal space of the cylindrical spacer member 1, the conductive passage 4 being adapted to be disconnected by the destruction of the upper plate 3 with a pressure difference between both sides of the upper plate 3. The upper plate 3 is formed of an electrically insulating material, which has a Young's modulus of 60 GPa or larger, bending strength of 80-1,000 MPa and a thickness of 10-100 μm. The degree of planarity of the upper plate 3 is 1.5% or smaller to the minimum diameter of the internal space of the spacer member 1.

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 rechargeable lithium-ion batteries, aluminum electrolytic capacitors, electric double-layer capacitors, and other devices that require miniaturization.

[0002]

2. Description of the Related Art In recent years, with the spread of electronic devices such as portable information terminals such as mobile phones, video cameras, and notebook computers, lithium ion batteries, aluminum electrolytic capacitors, electric double layer capacitors, etc. have been used as backup power supplies. It has become widely used.

In a conventional lithium ion battery, for example, as shown in FIG. 5, an organic solvent solution composed of an alkali metal salt such as propylene carbonate is filled as an electrolytic solution 22 in a metal casing 21 and the electrolytic solution 22 is Has a structure in which a positive electrode 23 made of lithium oxide and a negative electrode 24 made of a carbon compound such as fluorocarbon are arranged to face each other with a separator 25 interposed therebetween.
Is charged or discharged by moving lithium (Li) ions between the two.

However, when this lithium ion battery is overcharged or short-circuited, the temperature of the battery rises and decomposition of the electrolyte solution 22 occurs, generating gas and increasing the pressure inside the battery housing 21 greatly. In the worst case, there is a risk of explosion. Therefore, the lithium ion battery is provided with various safety devices.

[0005] These safety devices include a safety valve mechanism and a current cutoff mechanism. In the safety valve mechanism, a safety valve arranged on the surface of the housing is opened by an increase in the pressure in the battery housing, and the gas in the housing is exhausted to stop the pressure increase. The current interrupting mechanism is one that interrupts the conductive path by using an increase in the pressure of the gas, and that interrupts the conductive path by using an increase in the temperature inside the housing caused by the increase in the pressure.

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

As an apparatus utilizing the pressure increase, for example, as shown in Japanese Patent Application Laid-Open No. 9-55197, a conductive path and a pressure receiving portion displaced by the pressure in the battery and a mechanism for breaking the conductive path by the displacement of the pressure receiving portion are disclosed. Provisions have been made.

[0008]

However, the structure disclosed in Japanese Patent Application Laid-Open No. 9-55197 requires the above-mentioned mechanisms and a portion for arranging and connecting them, which makes the mechanism complicated, miniaturized, and low in size. There was a problem in terms of cost.

[0009] Further, portable information terminals such as mobile phones, video cameras, and notebook personal computers are increasingly being miniaturized in the future, and miniaturization of the battery itself is an urgent issue. The device is complicated and difficult to incorporate into the battery, which is a major obstacle to miniaturization.

The present invention has been devised in view of the above-mentioned drawbacks, and has as its object to provide a safety device that can be housed inside a housing of a battery or the like and that can easily cope with miniaturization. Another object of the present invention is to provide a highly reliable safety device having a mechanism that operates instantaneously when the pressure rises.

[0011]

According to the present invention, an upper plate and a lower plate having conductive paths on their surfaces are mounted on both upper and lower surfaces of a cylindrical spacer member so as to seal the internal space of the cylindrical spacer member. The safety device is configured such that the conductive path is broken by breaking the upper plate due to a pressure difference between both surfaces of the upper plate, wherein the upper plate has a Young's modulus of 60 GPa or more and a bending strength of 80 to It is formed of an electric insulating material having a thickness of 1000 MPa and a thickness of 10 to 100 μm, and the flatness of the upper plate is 1.5% or less of the minimum diameter of the internal space of the spacer member. Is what you do.

According to the safety device of the present invention, the upper plate has a Young's modulus of 60 GPa or more and a bending strength of 80 to 1000 MPa.
a, The flatness of the upper plate is set to a value of 1.5% or less with respect to the minimum diameter of the internal space of the spacer member. The stress applied to the upper plate is concentrated at a position facing the inner periphery of the spacer member, and as a result, the upper plate can be reliably destroyed with a stable pressure value, and the pressure is instantaneously and surely increased. An extremely reliable safety device that can cut off the road.

[0013]

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

FIG. 1A is a sectional perspective view of the safety device of the present invention. An on-cylinder spacer member 1 is integrally provided around an upper plate 3 made of ceramics, glass, or glass ceramics. An internal space at the center of the spacer member 1 is formed as a reference pressure chamber 2, and covers the reference pressure chamber 2. So that the lower plate 5 is integrally provided. The lower plate 5 has a through hole 5a,
Here, a closing material such as resin is filled and closed. Also,
On the upper plate 3, a conductive path 4 formed by a vapor deposition method or the like is provided.

When this safety device is used, for example, a main power supply of a secondary battery is connected to the conductive path 4 and the upper plate 3
When the pressure on the surface opposite to the reference pressure chamber 2 rises due to overcharging or the like and the pressure difference between the reference pressure chamber 2 and the inside of the reference pressure chamber 2 exceeds a specified value (hereinafter referred to as abnormal pressure occurrence), By breaking the plate 3 and breaking the conductive path 4, the main power supply of the secondary battery or the like can be cut off.

At this time, the upper plate 3 has a Young's modulus of 60 GPa.
As described above, the bending strength is formed from a brittle material having a bending strength of 80 to 1000 MPa, the thickness is adjusted to 10 to 100 μm, and the flatness is adjusted to a value of 1.5% or less with respect to the minimum diameter of the internal space of the spacer member 1. Thus, the instantaneous and complete interruption of the conductive path 4 is realized when an abnormal pressure is generated.

As shown in FIG. 1B, only the upper plate 3 having a warp inside the inner space of the spacer member 1 is used, and the upper plate 3 having no warp outside is used.

When the warpage of the upper plate 3 toward the inside is expressed as the flatness of the upper plate 3, the minimum diameter of the inner space (reference pressure chamber 2) of the spacer member 1 is D, and When the flatness is A, the range is limited to A0.015D.

Further, as a specific material of the upper plate 3, ceramics such as alumina and zirconia, glass such as crystallized glass, and glass ceramics can be used. It is preferable to use the same material as the upper plate 3 for the spacer member 1 and the lower plate 5.

Further, according to the present invention, if the shape of the reference pressure chamber 2 in plan view is set so that the ratio of the major axis / minor axis is within the range of 1.0 to 1.2, the instantaneous Complete interruption of the conductive path 4 can be further ensured. Therefore, when the reference pressure chamber 2 is viewed in plan, it is preferable that the ratio of the major axis / minor axis is in the range of 1.0 to 1.2.
Here, the long diameter is the longest diameter when the reference pressure chamber 2 is viewed in plan, and the short diameter is the shortest diameter.

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. 2, a thin green sheet 3 ′ for forming the upper plate 3 and a thick wall for forming the spacer member 1 are formed by a general doctor blade method, a calender roll method, a rolling method, or a press molding method. Green sheet 1 'and green sheet 5' forming lower plate 5
Are prepared respectively.

The thin and thick green sheets are not limited to the above-mentioned solvent-based slurry, but may be obtained by mixing an organic binder, a plasticizer, a dispersant, and ion-exchanged water with ceramic powder. May be used. Further, a thick sheet-shaped molded product may be used by laminating thin green sheets.

The thick green sheet 1 'thus obtained is formed by punching a through hole 2' serving as the reference pressure chamber 2 and the green sheet 5 'is formed by punching a through hole 5a' using a mold. Then, a thin green sheet 3 ', a thick green sheet 1' having a through hole 2 ', and a thick green sheet 5' having a fine through hole 5a 'are laminated and integrated as shown in FIG. Thereafter, firing is performed integrally in an air atmosphere at 800 ° C. or higher.

After the upper plate 3, the spacer member 1, and the lower plate 5 are integrally fired in this manner, a conductive path 4 is formed on the upper plate 3, and a through-hole 5a penetrating into the reference pressure chamber 2 is made of resin or the like. And the safety device of the present invention can be obtained.

It should be noted that the through-hole 5a is formed beforehand.
Finally, by closing this with a closing material, breakage during the manufacturing process can be prevented, and the pressure in the reference pressure chamber 2 can be set to the atmospheric pressure.

As another manufacturing method, a ceramic sheet such as alumina or zirconia or a glass or glass ceramic powder is added, and after adding a binder, a green sheet forming the spacer member 1 and the upper plate 3 is produced by a press method. Both are laminated and integrally fired in an air atmosphere at 800 ° C. or higher. After that, the reference pressure chamber 2 may be covered with the lower plate 5, the upper plate 3 may be processed to a desired thickness, and then the conductive path 4 may be formed on the upper plate 3.

The conductive path 4 is made of Cu, Ni, Cr, A
metal, such as l, Au, Ag, Pd, W or alloys thereof, or a conductive material such as carbon;
It is formed by a sputtering method, an evaporation method, or a printing method.

Further, since the above-mentioned safety device is very small, a large number can be manufactured at the same time by a multi-cavity method. As shown in FIG. 3, one green sheet 1 'is provided with a large number of through-holes 2' serving as reference pressure chambers 2, and similarly, a green sheet 5 'having a large number of through-holes 5a' and a thin green After laminating the sheets 3 ′ and integrally firing to form the conductive paths 4, cutting is performed, so that a large number of safety devices can be manufactured at the same time.

In the case where the upper plate 3, the spacer member 1, and the lower plate 5 are integrally manufactured as described above, the firing shrinkage of the thin green sheet 3 'is calculated from the sintering shrinkage of the green sheet 1'. The green density of the green sheet is adjusted so as to increase by 1.0% to 3.0%.

This is because the flatness of the upper plate 3 is made smaller than the minimum diameter of the reference pressure chamber 2 without deforming or cracking the upper plate 3 when each sheet is laminated and integrally sintered. To 1.5% or less.

If the difference in the firing shrinkage between the thin green sheet 3 ′ and the green sheet 1 ′ is less than 1.0%, or the thin green sheet 3 ′ is smaller than the firing shrinkage of the green sheet 1 ′. If it is small, when the respective sheets are stacked and integrally sintered, the upper plate 3 is deformed, and the flatness exceeds 1.5% with respect to the minimum diameter of the reference pressure chamber 2.

When the firing shrinkage of the thin green sheet 3 ′ is larger than the firing shrinkage of the green sheet 1 ′ by 3.0%, when the respective sheets are integrally sintered, the thin green sheet 3 ′ is sintered. The green sheet 3 ′ is pulled from the other green sheets 1 ′ and 5 ′, and a crack is generated in a part of the upper plate 3.

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

FIG. 4 shows a secondary battery incorporating the safety device of FIG. 1 (a).

The positive electrode 8 serving as an internal electrode is connected to a housing 11 and an output unit 12 serving as an electrically insulated external electrode.
The negative electrode 9 as the other internal electrode is electrically connected to the housing 11 (not shown). In an actual battery, the positive electrode 8 and the negative electrode 9 are stacked in multiple layers with the separator 7 interposed therebetween, but they are omitted in this figure.

The safety device 10 according to the present invention includes the output unit 1
It is installed in a form electrically connected between 2 and the positive electrode 8 by an ultrasonic welding method or the like. There is no problem even if the safety device 10 is installed on the negative electrode 9 side.

The operation of the safety device 10 of the present invention is roughly as follows. When the battery is overcharged for some reason, the electrolytic solution 6 evaporates and gas is generated in the battery case as described above, and the pressure in the battery case starts to increase. When the internal pressure of the battery becomes a certain value or more, the upper plate 3 of the safety device 10 is broken, the conductive path 4 formed on the upper plate 3 is broken, and charging stops, thereby stopping gas generation. Further pressure rise can be prevented. The thickness and material of the upper plate 3 are appropriately selected from the pressure to be broken and the allowable size of the safety device 10.

[0039]

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

Using polyvinyl butyral as a binder, dibutyl phthalate as a plasticizer, and toluene as a solvent, a dispersant was added to the alumina powder to prepare a solvent-based slurry, and the upper plate 3 made of alumina ceramic was formed by a doctor blade method. A green sheet 3 ', a green sheet 1' of the spacer member 1 made of alumina ceramics, and a green sheet 5 'of the lower plate 5 were prepared.

The thickness of the green sheet 3 ′ of the upper plate 3 is set to 46
The thickness of the green sheet 1 'of the spacer member 1 was 0.75 mm, and the thickness of the green sheet 5' of the lower plate 5 was 0.35 mm.

The green sheet 1 ′ of the spacer member 1
, A hole 6 'forming the reference pressure chamber 2 was punched out by a mold.

Thereafter, the green sheet 3 'of the upper plate 3, the green sheet 1' of the spacer member 1, and the green sheet 5 'of the lower plate 5 are laminated, formed and integrated as shown in FIG. Thermocompression bonding was performed at .47 MPa. An adhesive liquid composed of a plasticizer, a solvent, a thickener, and a surfactant is applied between the sheets with a screen to give an adhesive property. Thereafter, a break groove having a predetermined size is formed by the above-described multi-cavity method, which is baked in an air atmosphere at 1620 ° C., then divided, and a conductive path 4 of aluminum is formed by a vacuum deposition method. Safety device 10
I got

The minimum diameter of the reference pressure chamber 2 of the safety device 10 was 3 mm or 5 mm.

The upper plate 3 has a Young's modulus of 325 GP.
a, The bending strength is 300 MPa.

When 40 safety devices 10 were put into a pressure vessel, and the pressure was gradually increased to 0.7 MPa, the probability that the upper plate 3 was broken and the conductive path 4 was broken was obtained. Was calculated as the breaking probability.

Table 1 shows the results.

[0048]

[Table 1]

As can be seen from Table 1, the flatness of the upper plate 3 is 1.5% or less of the minimum diameter of the reference pressure chamber 2 (samples No. 1 to No. 3, sample No. 7). ~ No.9)
Indicate that all of them have a fracture probability of 100%
When the flatness is 1.5% or more (samples No. 5 and No. 11) with respect to the minimum diameter of the reference pressure chamber 2, the fracture probability becomes low.

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

In the same manner as in Example 1, A to F in Table 2 were used.
The safety device 10 was manufactured by laminating green sheets using ceramic powder such as alumina, zirconia, or glass or glass ceramic powder shown in FIG. The firing temperature was set to an appropriate temperature for each material.

The thickness of the upper plate 3 is adjusted to 8 to 150 μm,
The shape of the reference pressure chamber 2 was a circle having a diameter of 3 mm, and the long diameter / short diameter was 1.0. Also, a through hole 5 communicating with the reference pressure chamber 2
The diameter of a was set to 0.3 mm and shielded with resin.

The safety device thus manufactured was charged into a pressure vessel, and a pressure up to 0.7 MPa was gradually applied to calculate a probability of breakage.

As shown in Table 3, the materials E-1 to E-9 in which the Young's modulus of the material is 60 MPa 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 upper plate 3 has a Young's modulus of 60 GPa or more and a bending strength of 80 to 1000.
MPa.

The thickness of the upper plate 3 is 1
A-1, B-1, C-1, D-1, E which are 0 μm or less
-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 also increases and the breaking probability decreases. Here, considering the probability of breakage and destruction during handling, the thickness of the upper plate 3 is specified to be 10 to 100 μm, and more preferably 25 to 75 μm in consideration of use as a safety device.

[0059]

[Table 2]

[0060]

[Table 3]

In addition, as a result of an operation evaluation using the safety device of the present invention as a safety device for a rechargeable secondary battery, 100% breakage at 0.7 MPa was confirmed, and the required breaking pressure was satisfied. Was something. In addition, the conductive path 4 was surely shut off even in the damaged state.

Here, an example in which the safety device of the present invention is used as a safety device for a rechargeable secondary battery has been described. However, the present invention is not limited to this, and a safety device such as an aluminum electrolytic capacitor or an electric double layer capacitor is used. It can also be used as a device.

[0063]

According to the safety device of the present invention, the upper plate has a Young's modulus of 60 GPa or more and a bending strength of 80 to 1000 MPa.
a, the flatness of the upper plate is set to a value of 1.5% or less with respect to the minimum diameter of the internal space of the spacer member. The stress applied to the upper plate is concentrated at a position facing the inner periphery of the spacer member. As a result, the upper plate can be reliably destroyed with a stable pressure value, and instantly and surely when the pressure rises. An extremely reliable safety device that can cut off the conductive path.

[Brief description of the drawings]

FIG. 1 (a) is a sectional perspective view showing a safety device of the present invention,
FIG. 2B is an enlarged sectional view of FIG.

FIG. 2 is an exploded perspective view showing a manufacturing method of the safety device of the present invention.

FIG. 3 is a plan view of a green sheet showing a manufacturing method of the safety device of the present invention.

FIG. 4 is a partially broken sectional view of a lithium ion battery using the safety device of the present invention.

FIG. 5 is a partially broken sectional view of a conventional lithium ion battery.

[Explanation of symbols]

 1: Spacer member 2: Reference pressure chamber 3: Upper plate 4: Conductive path 5: Lower plate 5a: Through hole 6: Electrolyte solution 7: Separator 8: Positive electrode 9: Negative electrode 10: Safety device 11: Housing 12: Output unit

Claims (1)

[Claims] An upper plate and a lower plate having conductive paths on their surfaces are attached to upper and lower surfaces of a cylindrical spacer member so as to seal an internal space of the cylindrical spacer member. A safety device wherein the conductive path is disconnected by breaking the upper plate due to a pressure difference, wherein the upper plate has a Young's modulus of 60.
It is formed of an electrical insulating material having a GPa or more, a bending strength of 80 to 1000 MPa and a thickness of 10 to 100 μm, and the flatness of the upper plate is 1.5% or less with respect to the minimum diameter of the internal space of the spacer member. A safety device characterized by the value of