JPH10241652A - Safety structure of sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safety structure of a sealed battery which is capable of stopping battery actuation within a prescribed battery internal pressure range and rupturing a rupture plate, within a prescribed battery internal pressure range higher than the above a prescribed pressure. SOLUTION: This safety structure stops battery actuation by rupture of a primary rupture body R1 having a smaller pressure resistant rupture strength than a secondary rupture body R2 and permits the battery internal pressure to be received by the secondary rupture body R2 after the rupture of the primary rupture body R1. This structure is superior in discharge capacity characteristics and charge and discharge cycle characteristics and particularly effective as a lithium secondary battery of a non-aqueous liquid electrolytic with its a high level for danger of explosion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety structure of a sealed battery, and more particularly to a safety structure of various secondary batteries having a non-aqueous liquid electrolyte, in particular, a lithium secondary battery.

[0002]

2. Description of the Related Art FIG. 5 is a cross-sectional view of a conventional lithium secondary battery having a non-aqueous liquid electrolyte, and FIG. 6 is an enlarged cross-sectional view of a safety structure portion and its vicinity in FIG.
5 and 6, reference numeral 1 denotes a metal battery can, 2 denotes a negative electrode electric insulating plate, 3 denotes a battery element winding body, 31 denotes a negative electrode lead extending from the lower portion of the battery element winding body 3, and 32 denotes the same. The positive electrode lead extending from the upper part of the wound body 3, 4 is a donut-shaped positive electric insulating plate, 5 is a battery safety structure, 6 is a positive electrode cover, 7 is a safety structure 5 and a positive electrode cover 6 from the battery can 1. An electric insulating gasket 8 for insulation is provided on the outer wall of the battery can 1 and is a depression for fixing the battery contents below the positive electric insulating plate 4 without looseness. In FIG. 6, the safety structure 5
Comprises a conductive plate 51, a conductive rupture plate 52, and an electrical insulating plate 53 provided between the conductive plate 51 and the rupture plate 52. The conductive plate 51 and the rupture plate 5
2 is in electrical contact with point A in the figure.
The tip of the negative electrode lead 31 is welded to the bottom inner wall of the battery can 1 beyond the outside of the negative electrode electrical insulating plate 2, and the tip of the positive electrode lead 32 passes through the center hole of the donut-shaped positive electrical insulating plate 4. And is welded on the back surface of the conductive plate 51. Since the conductive rupture plate 52 is in direct contact with and electrically connected to the back surface of the positive electrode lid 6, the positive electrode lead 32 is connected to the positive electrode lid 6 via the conductive plate 51 and the rupture plate 52.
Is electrically conducted.

Before describing the operation mechanism of the safety structure 5, the operation principle of a general safety structure will be described. The rupture of a battery is caused by various causes, the main one being a short circuit accident in the battery. Due to the short circuit accident, the temperature inside the battery rises abnormally, which leads to the abnormal vaporization of the liquid electrolyte and the resulting increase in the internal pressure, leading to the rupture of the battery. Therefore, when the internal pressure of the battery rises abnormally, first, the short circuit of the battery is cut off to stop the operation of the battery, so as to suppress the abnormal rise of the internal pressure. Next, if the internal pressure continues to rise even after this suppression measure, the rupture plate is ruptured at the increased internal pressure and the inside of the battery is exposed to the atmospheric pressure to prevent the battery from bursting.

The conventional safety structure 5 shown in FIG. 6 also follows the above-mentioned mechanism. When the internal pressure of the battery rises abnormally, the conductive plate 51 and the rupture plate 52 at the point A are utilized by using the increased internal pressure. Then, the electrical conduction between the positive electrode lead 32 and the positive electrode cover 6 and thus the positive electrode lead 32 and the negative electrode lead 31 are interrupted to stop the operation of the battery. If the rising internal pressure is continued even after the operation of the battery is stopped, the internal pressure of the battery is received by the rupture plate 52 through a large number of through holes 511 provided in the conductive plate 51, and the rupture of the rupture plate 52 causes The internal pressure of the battery is released to the atmosphere through a large number of through holes 61 provided in the positive electrode lid 6 due to the rupture of the weak point portion 521 provided therein. In this case, the pressure rupture strength of the rupture plate 52 must be, of course, equal to or less than the pressure rupture strength of the battery can 1 to be practically used. Therefore, in consideration of the pressure rupture strength of the battery can 1 used in practice, the internal pressure range P1 of the battery for interrupting the electrical conduction between the conductive plate 51 and the rupture plate 52 at the point A is about 3 to ²⁰ kgf / cm ^2. And rupture board 5
The pressure rupture strength P2 of No. 2 is designed to be about 1.2P1 to 2.5P1.

Conventionally, the electrical conduction between the conductive plate 51 and the rupture plate 52 at the point A in FIG. 6 has been achieved by two methods, a method of welding the two or a method of simply contacting the two. However, both methods have the following disadvantages. That is, the points connected by the welding method (point A)
In order to surely cause connection destruction due to peeling off of the inner pressure range P1 in the above-mentioned internal pressure range P1, extremely high welding technology is required.
Moreover, it is necessary to control the welding force. However, in practice, the welding force is greatly affected by the processing accuracy of the conductive plate 51 and the rupture plate 52 and the constituent materials thereof, so that it is practically very difficult to realize the welding force. On the other hand, in the simple contact method, the springs of the conductive plate 51 and the rupture plate 52 are used to apply a pressing force to each other at a point A by using the respective spring elasticity.
In this case, it is necessary to control the magnitude of the pressing force to be in the range of the above P1, but this control is not only difficult, but the pressing force fluctuates even during normal operation of the battery. There's a problem. That is, the pressing force fluctuates due to the pressure difference in the battery due to the temperature difference between the time of charging and the time of discharging of the battery and the fluctuation of the outside air temperature.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a sealed battery capable of stopping battery operation in a predetermined battery internal pressure range and bursting a rupture plate in a predetermined battery internal pressure range higher than the predetermined pressure. The purpose is to provide a safety structure.

[0007]

The present invention has the following features. (1) Partial contact between the primary rupture body that directly receives the pressure in the battery and the secondary rupture body that is installed above the primary rupture body through a space and has a higher pressure rupture strength than the primary rupture body That the internal pressure of the battery capable of bursting the primary rupture body acts on the secondary rupture body due to the rupture of the primary rupture body, and the above-mentioned electrical conduction is interrupted based on the rupture of the primary rupture body. Safety structure of sealed battery. (2) Electrical continuity between the primary rupture body and the secondary rupture body is established by partial contact with each other, and the secondary rupture is caused by a sudden increase in pressure in the space between the two rupture bodies due to the rupture of the primary rupture body. The safety structure of the sealed battery according to the above (1), wherein the body is deformed to release the contact. (3) Electrical continuity between the primary rupture body and the secondary rupture body is achieved by contact between the side wall of the protrusion provided on the surface of the primary rupture body and the side wall of the protrusion provided on the back surface of the secondary rupture body. The safety structure of the sealed battery according to the above (2). (4) The electrical conduction between the primary rupture body and the secondary rupture body is caused by the contact between the side wall slope of the projection provided on the surface of the primary rupture body and the side wall slope of the projection provided on the back surface of the secondary rupture body. (3) The safety structure of a sealed battery according to the above (3).

[0008]

According to the present invention, two rupture bodies, a primary rupture body and a secondary rupture body, are employed, and a space is provided between the two rupture bodies. The primary rupture body continuously receives the pressure in the battery directly, and when the pressure in the battery rises and reaches a high pressure that ruptures the primary rupture body, the high pressure ruptures the primary rupture body. It is transmitted to the above space and acts on the secondary rupture body. Accordingly, the pressure rupture strengths of the primary rupture body and the secondary rupture body can be set independently of each other, so that both rupture bodies can be ruptured independently of each other at a predetermined pressure. Further, both rupture bodies are electrically connected to each other in a normal state due to partial contact with each other, but in the present invention, the electrical continuity is configured to be cut off based on the rupture of the primary rupture body. Therefore, if the pressure rupture strength is set in advance so that the primary rupture body ruptures when the pressure in the battery rises to such an extent that the operation of the battery needs to be stopped, it is ensured that the battery operates at the time of the pressure rise. Can be stopped. On the other hand, if the pressure rupture strength of the secondary rupture body is set to an intermediate value between the pressure rupture strengths of the primary rupture body and the battery can, the battery internal pressure is stably released to the atmosphere without bursting the battery can. be able to. The sudden pressure rise in the above space due to the rupture of the primary rupture body,
An impact force is applied to the secondary rupture body to mechanically deform it to a greater or lesser extent. By utilizing this deformation, the electrical conduction between the primary rupture body and the secondary rupture body can be cut off. Alternatively, the same purpose as described above can be achieved by utilizing the collapse of the primary rupture body due to its rupture.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a cross-sectional view of an embodiment of the present invention in a normal state, and FIG. 2 is a cross-sectional view of the embodiment of FIG. 1 in which a primary rupture body has ruptured. 3 and 4 are partially enlarged sectional views of another embodiment of the present invention.

In FIG. 1, R1 is a primary rupture body,
R2 is a secondary rupture body having a higher pressure rupture strength than the primary rupture body R1, and S is a primary rupture body R
A space 53 between the primary rupture body R2 and the secondary rupture body R2 is a donut-shaped electric insulating plate provided between the two rupture bodies R1 and R2 to keep them insulated. A dome-shaped positive lid 6 having a through hole 61 is placed on the secondary rupture body R2 as in the conventional case, and the positive lid 6 is electrically connected to the secondary rupture body R2 at a flat portion of the dome. ing. Both rupture bodies R1 and R2, electrical insulating plate 5
3 and the entirety of the positive electrode lid 6 are installed via an electrically insulating gasket 7 on the upper part of the battery can 1 as shown in FIG.

The primary rupture body R1 has a disk shape and comprises an outer thick portion R11 as an embodiment of a projection and a thin flat plate portion R12 located inside, and a positive electrode lead 32 is provided on the back surface of the thick portion R11. Are welded. The secondary rupture body R2 also has a disk shape, and has a projection R22 on the back surface. R21 is a weak point of the secondary rupture body R2.
Both rupture bodies R1 and R2 are both formed of a conductive material, and are electrically connected by simple contact between the side surface R111 of the thick portion R11 of the primary rupture body R1 and the side surface R221 of the protrusion R22 of the secondary rupture body R2. Is electrically conductive.

Although the primary rupture member R1 corresponds to the conductive plate 51 in the conventional example shown in FIG. 6 from the viewpoint of the installation position, the primary rupture member R1 is fundamentally different from the conductive plate 51 and has a penetration No holes. Therefore, the space S between the two rupture bodies R1 and R2 is kept in a state where the primary rupture body R1 is isolated from the internal pressure in the battery in the normal state of the battery. In the present invention, a special sealing mechanism may be provided to sufficiently protect the pressure in the space S from the pressure in the battery. However, such a mechanism is not actually required, and both rupture members R1 and R2, electric The insulating plate 53 and the entirety of the positive electrode lid 6 need only be placed on the upper part of the battery can through the electric insulating gasket 7 as in the conventional example shown in FIG. When the battery becomes abnormal,
Generally, the pressure in the battery rises sharply. However, even if the space S communicates with the inside of the battery through a number of small gaps, the transmission of the rapidly rising pressure is delayed due to passing through the small gaps, and this delay has a substantial pressure isolating effect. .

However, when an abnormal condition occurs in the battery and the pressure inside the battery rises and the pressure exceeds the pressure rupture strength of the primary rupture member R1, the primary rupture member R1 bursts, and the pressure in the space S becomes instantaneous. The pressure reaches the pressure inside the battery and the pressure is transmitted to the secondary rupture body R2. As shown in FIG. 2, the secondary rupture body R2 which has received the pressure in the battery as a shock is deformed so as to expand toward the positive electrode lid 6, and at the same time as this deformation, the projection R22 of the secondary rupture body R2 is primarily deformed. The rupture member R1 is separated from the side surface R111 of the thick portion R11, and the electrical conduction between the rupture members R1 and R2 is interrupted. As a result, the battery operation also stops. Although it depends on the cause of the abnormal situation of the battery or the degree of the magnitude of the abnormal situation, in many cases, the stop of the battery action stops the increase of the pressure in the battery, and the secondary rupture body R2 stops deforming. In some cases, the pressure in the battery continues to rise even after the battery operation is stopped, but the rising pressure is reduced by the secondary rupture member R2.
When the pressure exceeds the pressure rupture strength of the positive electrode, the pressure rupture also occurs, and the internal pressure of the battery is released to the atmosphere via the through hole 61 of the positive electrode lid 6.

The pressure rupture strength of the primary rupture body is set based on an empirical rule from the viewpoint of preventing an excessive rapid rise in the pressure in the battery, while that of the secondary rupture body is the same as that of a normal metal battery can. It may be determined in consideration of the pressure rupture strength. Generally, the pressure rupture strength of the primary rupture body is about ² to 30 kgf / cm ² , especially 3 to ²⁰ kgf / cm ^2.
/ Cm ² , while that of the secondary rupture body R2 is preferably about 1.2 to 3 times, especially about 1.2 to 2.5 times that of the primary rupture body R1. . By adopting various aspects for the material and structure of each rupture body, especially the structure of the weak point,
Each having the above-mentioned pressure rupture strength can be produced.

Examples of the conductive material for forming the primary rupture body R1 and the secondary rupture body R2 include a conductive metal such as aluminum, nickel, copper, iron, stainless steel or an alloy thereof, and a conductivity-imparting agent. Conductive metal powder, conductive carbon black, conductive carbon fiber, graphite fiber, conductive organic polymer composition comprising a mixture of graphite particles and an organic polymer, and the above conductive material on the surface of various organic polymer sheets. A conductive plated sheet having a plated layer of a conductive metal or alloy is exemplified.
Each of the conductive materials described above can be used alone or in combination with other materials as a single plate or a composite plate.

The primary rupture body R1 comprises a thick portion R11 and a thin flat plate portion R12. The whole may be formed of a single conductive material, and may be formed on a single disc-shaped thin plate. A thick-walled portion R11 may be formed by electrically bonding a donut-shaped conductive material plate by bonding or welding. In this case, the remaining portion to which the donut-shaped conductive material plate is not bound functions as the flat plate portion R12. Since the flat plate portion R12 has a relatively small pressure rupture strength as described above, when this portion is formed of one sheet of conductive material, the mechanical strength of the portion is small, but This can cause difficulties in production and handling. In such a case, the flat plate portion R12 (or even the bottom portion of the thick portion R11 from the viewpoint of ease of manufacture) is provided on one surface of a relatively thick perforated plate having high mechanical strength with the above-mentioned pressure rupture strength. It is good to form with the composite board which stuck the thin board of the conductive material which has this. At this time, the thick perforated plate may be a conductive material or an electrically insulating material. In the case of an electrically insulating material, the positive electrode lead 32 is welded to a thin plate of a conductive material. When employing the primary rupture body R1 made of such a composite plate, the thin plate is used so as to come to the back side (the positive electrode lead 32 side). Thus, when the pressure in the battery exceeds the pressure rupture strength of the primary rupture body R1. At the perforated portion of the thick perforated plate, the thin plate on the back side ruptures and transmits the internal pressure of the battery to the secondary rupture body R2.

The secondary rupture body R2 has no particular difference in structure or function from the conventional rupture plate except that it has a projection R22 on the back side thereof. , Cutting,
Alternatively, it can be manufactured by a combination processing thereof.

The primary rupture member R1 and the secondary rupture member R2 are in contact with each other in a normal state so that the two rupture members are in a reliable electrical conduction state. It is important that the electrical conduction be cut off. In the case of the embodiment shown in FIG. 1, the conduction-interruption is performed by the thick portion side surface R111 of the primary rupture member R1 and the secondary rupture member R2.
This is achieved by simply making surface contact with the protrusion side surface R221 with an appropriate contact area with an appropriate mutual pressing.
The contact area is approximately 0.05 to 0.5 mm, particularly approximately 0.1 to 0.3 mm, as a vertical contact distance in the cross-sectional view of FIG. It is preferable that both rupture bodies be fitted together. In this case, the height of the thick portion R11 is 0.05 to 0.5 mm.
About 0.1 to 0.3 mm is appropriate.

Thick portion side face R111 and protrusion side face R221
1 means that both may extend in the vertical direction as shown in FIG. 1, but if they are inclined with respect to each other as in the embodiment shown in FIG. ,
In addition, when the primary rupture member R1 ruptures due to a large contact area, the secondary rupture member R2 smoothly separates from the primary rupture member R1.

In FIG. 4, a primary rupture body R1
Has an intermediate portion R13 having a height intermediate between the flat portion R12 and the thick portion R11, and the intermediate portion R13 is located immediately below the protrusion R22 of the secondary rupture body R2. As a result, the flat plate portion R12 of the primary rupture member R1 does not directly contact the lower end of the protrusion R22 of the secondary rupture member R2. When deforming in the direction,
The projection R22 is easily deformed without being hindered by the lower end thereof, so that the primary rupture member R1 is ruptured and the electrical interruption between the two rupture members proceeds smoothly.

The present invention is not limited to the above embodiment, but includes various modified embodiments. For example, the weak point portion (scheduled rupture point) of the primary rupture body is electrically connected to the secondary rupture body, and when the primary rupture body ruptures, the weak points are scattered and the electrical rupture of the both rupture bodies is caused. May be blocked. Further, a structure may be employed in which a positive electrode lead is welded to the back surface of the weak point portion of the primary rupture body, and the welding is cut together with the rupture of the weak point portion.

[0022]

According to the present invention, the battery operation can be reliably stopped by the pressure rupture strength of the primary rupture body, and the pressure inside the battery can be reliably reduced by the pressure rupture strength of the secondary rupture body. Can be open to the atmosphere. Therefore, it has excellent discharge capacity characteristics and charge / discharge cycle characteristics, but is particularly useful as a safety structure for a non-aqueous liquid electrolyte-based lithium secondary battery having a high risk of explosion.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the present invention in a normal state.

FIG. 2 is a cross-sectional view of the embodiment of FIG. 1 in which a primary rupture body has ruptured.

FIG. 3 is a partially enlarged cross-sectional view of another embodiment of the present invention.

FIG. 4 is a partially enlarged sectional view of still another embodiment of the present invention.

FIG. 5 is a cross-sectional view of a conventional battery.

FIG. 6 is a sectional view of a conventional safety structure.

[Explanation of symbols]

R1 Primary rupture member R11 Thick portion R12 Thin plate portion R2 Secondary rupture member R22 Projection S Space between primary rupture member and secondary rupture member 6 Positive electrode cover

Claims (4)

[Claims] 1. A primary rupture body for directly receiving pressure in a battery and a secondary rupture body disposed above the primary rupture body through a space and having a pressure rupture strength greater than that of the primary rupture body by partial contact, and So that the internal pressure of the battery that can be ruptured and that can rupture the primary rupture body acts on the secondary rupture body due to the rupture of the primary rupture body, and the above-described electrical conduction is interrupted based on the rupture of the primary rupture body. A safety structure for a sealed battery. 2. The electrical conduction between the primary rupture body and the secondary rupture body is established by partial contact with each other, and the primary rupture body ruptures due to a sudden increase in pressure in the space between the two rupture bodies. 2. The safety structure for a sealed battery according to claim 1, wherein the secondary rupture body is deformed so that the contact is released. 3. The electrical connection between the primary rupture body and the secondary rupture body is caused by the contact between the side wall of the protrusion provided on the surface of the primary rupture body and the side wall of the protrusion provided on the back surface of the secondary rupture body. The safety structure for a sealed battery according to claim 2, wherein the safety structure comprises: 4. The electrical conduction between the primary rupture body and the secondary rupture body is determined by a sidewall slope of a projection provided on a surface of the primary rupture body and a sidewall slope of a projection provided on a back surface of the secondary rupture body. The safety structure for a sealed battery according to claim 3, wherein the safety structure is made by contact of the battery.