JP2002124236A - Sealed battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealed battery equipped with a safety mechanism for cutting off a current in increasing internal pressure conditions and usable as a large-current battery, and to provide a sealed battery having an internal gas discharging function. SOLUTION: This sealed battery 1 is equipped with a first terminal 11 fixed to an electrode body 10, a second terminal 12 normally surface-contacting with the terminal 11, and a coil spring 13 for pressing the terminal 12 toward the terminal 11 side. The terminal 12 is equipped with an internal pressure receiving surface 121a with an internal pressure P1 acting thereon and an external pressure receiving surface 121b with the atmospheric pressure P0 acting thereon. When the pressure P1 reaches or exceeds a prescribed value due to heat generated by overcharge, etc., the terminal 12 moves up and parts from the terminal 11, thus cutting off continuity between the electrode body 10 and the exterior. When the pressure P1 rises further and an under surface of the terminal 12 is pushed up higher than the lower end of a groove part 211, the groove part 211 forms an internal gas discharge path causing an internal space K to communicate with the external space L, thus releasing the pressure P1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery provided with a safety mechanism for interrupting conduction between an electrode body and the outside when an internal pressure rises due to overcharge or the like.

[0002]

2. Description of the Related Art In a sealed battery, if an overcurrent, an overvoltage, or an external short circuit occurs due to an abnormality in an external circuit in charging and discharging or an erroneous handling due to its structure, the temperature inside the battery abnormally rises. Also, especially for sealed secondary batteries, excessive charging, excessive charging current and reverse connection voltage may be applied to the batteries due to improper charging such as failure of the charging device at the time of charging or mixing of the positive and negative electrodes. This may cause the temperature inside the battery to rise abnormally.

[0003] When such a temperature rise occurs, the pressure inside the battery also increases due to the thermal expansion of the gas inside the battery, the evaporation of the electrolytic solution, and the like. A safety mechanism is provided to prevent this. For example, Japanese Patent Application Laid-Open No. Hei 10-188945 discloses a metal plate 9 having a spring property when the internal pressure of a battery rises, as shown in FIG.
Due to the bending of 1, the contact A between the internal terminal 92 connected to the electrode body via the lead wire 93 and the metal plate 91 is instantaneously separated to cut off the current, and when the battery returns to the normal state, the coil spring 94. A structure in which the contact A is formed again by the stretching force of the contact is disclosed. Reference numeral 95 in FIG. 6 denotes a pressure release hole for keeping the space below and above the metal plate 91 equal to the battery internal pressure and the atmospheric pressure, respectively.

[0004]

However, Japanese Patent Application Laid-Open No.
In the configuration disclosed in JP-A-188945, the internal terminal 9
Since the contact point A between the metal plate 91 and the metal plate 91 has a small area, it is not suitable for a battery in which a large current (for example, 100 A or more) flows, such as for an electric vehicle or a hybrid vehicle. Further, since the metal plate 91 is a plate spring, the spring force greatly varies depending on the plate thickness. Therefore, if the plate thickness accuracy is low, the variation in the pressure (the pressure at which the safety mechanism operates) leading to the current interruption increases. In particular, the operating pressure is reduced (for example,
(atm or less), it is difficult to obtain the required accuracy because the plate thickness becomes small. further,
Since the current interrupting mechanism is constituted by a member different from the electrode terminal, there are problems such as an increase in the number of parts and a decrease in assemblability.

When the internal pressure of the battery rises significantly despite the interruption of the current, the structure shown in FIG.
Is broken to release the internal pressure to the atmospheric pressure, thereby preventing the battery from bursting. However, in this case, the battery cannot be reused. In addition, if the cause of the increase in the internal pressure is thermal expansion of the internal gas, the internal pressure also decreases due to the temperature decrease after the current is cut off. The internal pressure does not decrease unless this internal gas is released. In such a case, in order to enable the reuse of the battery, it is necessary to separately provide a safety valve for releasing the internal pressure in addition to the rupture hole 96, and the configuration of the battery is further complicated.

An object of the present invention is to provide a sealed battery having a safety mechanism which can be applied to a battery in which a large current flows and which interrupts conduction between an electrode body and the outside when the internal pressure rises. Another object of the present invention is that the configuration is simple,
An object of the present invention is to provide a sealed battery provided with a safety mechanism having a function of interrupting conduction between an electrode body and the outside when an internal pressure rises and a function of releasing internal gas.

[0007]

According to a first aspect of the present invention, there is provided a sealed battery having a safety mechanism for interrupting conduction between an electrode body and the outside when an internal pressure rises, and fixing the battery to the electrode body. A first terminal, a battery container that houses the electrode body and the first terminal, and a second that normally comes into surface contact with the first terminal and seals the internal space of the battery container. And a resilient member that applies a pressing force to the first terminal side to the second terminal, wherein the second terminal has a direction in which the second terminal contacts the first terminal and the first terminal. An internal pressure receiving surface on which the internal pressure of the battery container is applied and which is on the side in contact with the first terminal, and an external pressure receiving surface on which the pressure of the external space is applied. It is possible to move in the direction away from the first terminal by increasing the internal pressure Characterized in that there.

Further, the sealed battery according to the second aspect of the present invention includes a safety mechanism for interrupting conduction between the electrode body and the outside when the internal pressure increases, a first terminal fixed to the electrode body, A battery container that houses the first terminal, a second terminal that normally contacts the first terminal and seals the internal space of the battery container, and And a resilient member that applies a pressing force to the terminal side of the second terminal, and the second terminal is held so as to be able to reciprocate in a direction in contact with the first terminal and in a direction away from the first terminal. And an inner pressure receiving surface on the side in contact with the first terminal and on which the internal pressure of the battery container is applied, and an external pressure receiving surface on which the pressure of the external space is applied, and the first terminal is increased by increasing the internal pressure. And the second terminal is movable in a direction away from the first terminal. By moving in the direction away from, characterized in that the inner gas discharge path for communicating the said internal space and the external space is formed.

The sealed battery according to claim 3 is the battery according to claim 1 or 2, wherein a contact surface between the first terminal and the second terminal in the normal state is mirror-finished. It is characterized by being.

(Operation and Effect) In the sealed battery of the present invention, the electrode terminal itself is divided into a first terminal and a second terminal, and the pressure difference between the external pressure and the internal pressure is equal to or more than a predetermined set value. , The second terminal moves in a direction away from the first terminal. As a result, conduction between the first terminal and the second terminal is cut off, and further overcharging or the like is prevented. Since the current is interrupted by the direct movement of the second terminal, there is no need to provide a separate safety mechanism. For example, the configuration is simpler than that of a battery provided with the safety mechanism shown in FIG.

A coil spring is preferably used as the elastic member. In the sealed battery of the present invention, a leaf spring is not required either as a material for the second terminal or as a means for bringing the first terminal into contact with the second terminal. The pressure at which the terminals are separated from each other (pressure at which the current is interrupted) and the pressure at which the internal pressure is released to the atmospheric pressure (valve opening pressure) can be set with a high degree of freedom and with high accuracy. According to the sealed battery of the present invention, the pressure leading to current interruption or the valve opening pressure can be arbitrarily set in the range of 2 to 15 atm (more preferably, 5 to 10 atm). In addition, these set pressures, the area of the internal pressure receiving surface, the external pressure receiving surface,
It can also be adjusted by the contact area with the first terminal.

In the sealed battery according to the present invention, the first terminal and the second terminal are in "surface contact" with each other in a normal state, and are compared with a battery provided with a mechanism shown in FIG. The contact area of both terminals is clearly large. Therefore, this battery is suitable for a large current (for example, 100 A or more).

According to the second aspect of the present invention, the current is cut off and the internal gas discharge path is formed by the direct movement of the second terminal due to the increase of the internal pressure. Since the internal pressure is released to the atmospheric pressure from this internal gas discharge path, a current interrupting function and an internal pressure releasing function when the internal pressure increases can be realized without providing a separate safety valve or the like. In the sealed battery according to the second aspect, it is preferable that the first terminal and the second terminal are normally in surface contact with each other.

According to the third aspect of the present invention, since the contact surface is mirror-finished, the adhesion between the first terminal and the second terminal is good, so that the internal resistance of the battery can be reduced. it can. Also, in normal times, the first terminal and the second terminal can be airtightly adhered to each other, and when the internal pressure rises, the area of the internal pressure receiving surface increases due to the second terminal being lifted up from the first terminal. Since the movement of the second terminal is assisted, the current can be cut off instantaneously. The degree of the mirror finishing is preferably, for example, 0.8Z or less.

The sealed battery of the present invention is suitable for a secondary battery because it can prevent overcharge, and is preferably used as a lithium secondary battery, for example.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically by way of examples. (1) Battery Configuration FIG. 1 shows a normal state of the battery 1 of the present invention. The battery 1 is a lithium secondary battery, and includes an electrode body 10, a first terminal 11 fixed to the electrode body 10, a battery container 2 accommodating the electrode body 10 and the first terminal 11, Body 1
End face (contact end face) 11 of first terminal 11 protruding from zero
a, and a coil spring 13 for pressing the second terminal 12 toward the first terminal 11.

The electrode assembly 10 comprises a positive electrode sheet made of aluminum foil and having a positive electrode active material layer, a negative electrode sheet made of copper foil and the like having a negative electrode active material layer, and a separator made of porous polyethylene and interposed between both electrodes. (Both not shown) are laminated and wound around the first terminal 11 having a rod shape. Current collecting tabs (not shown) are attached at predetermined intervals to the side surface of the positive electrode sheet corresponding to the upper side of FIG. 1, and the current collecting tabs are connected to the first terminals 1 by welding or the like.
1 connected. Similarly, the negative electrode sheet is connected to a negative electrode terminal (not shown) in the lower part of FIG.

The overall shape of the battery case 2 is substantially a hollow cylindrical shape, and the wall surface at the center of the upper surface extends into the inside of the battery case 2 to form a cylinder portion 21. The second terminal 12
A disk portion 121 having an outer diameter equal to the inner diameter of the cylinder portion 21 and a cylindrical portion 122 extending from the center of the disk portion 121
And inserted into the cylinder 21 with the disk 121 facing downward. In addition, the coil spring 1 is
3 is inserted and further penetrated by a donut-shaped fixing member 15 via a sealing material 14.

By screwing the fixing member 15 to the upper end of the cylinder portion 21, the second terminal 12 is held so as to be able to reciprocate along the inner surface of the cylinder portion 21. Further, the coil spring 13 is housed in a spring chamber M defined by the cylinder portion 21, the disk portion 121 and the fixing member 15. The spring chamber M has an external space L formed by a groove 211 provided at one location in the circumferential direction of the cylinder 21 and a groove 151 provided at a corresponding location of the fixing member 15.
And is maintained at atmospheric pressure. Groove 211
Extends from the upper end of the cylinder portion 21 to a position away from the contact end surface 11a by a predetermined distance. The groove 21
1 and the groove 151 may be formed at a plurality of positions in the circumferential direction of the cylinder 21.

(2) Operation of Safety Mechanism In the normal state shown in FIG.
And the external space L are communicated with the disk 121 of the second terminal 12.
The airtight inside of the battery is maintained. Both the inner pressure receiving surface 121a and the contact end surface 11a, which are the lower surfaces of the disk portion 121, are mirror-finished (0.8Z or less), and are airtightly adhered in the normal state. Therefore, the internal pressure of the battery 1 is set to P ₁ , and the internal pressure receiving surface 121 is set.
The area of a Sa, when the area Sb of the contact end face 11a (Sa> Sb), the force F _in according to the internal pressure receiving surface 121a is represented by the following formula (1). F _in = P ₁ × (Sa−Sb) (1) On the other hand, F _out acting on the external pressure receiving surface 121b, which is the upper surface of the disk part 121, is as follows, assuming that the atmospheric pressure is P ₀ , and the spring force of the coil spring 13 is F ₀ . It is represented by equation (2). F _out = Sa × P ₀ + F ₀ (2)

[0021] The internal pressure P ₁ by overcharging or the like is increased, F _in>
When _Fout is reached, the second terminal 12 moves upward as shown in FIG. When the second terminal 12 starts rising from the first terminal 11, since as such the internal pressure P ₁ also to the portion in contact with the contact end face 11a, the internal pressure receiving surface 1
Force F _in according to 21a is as represented by the following formula (3), the movement of the second terminal 12 is facilitated. As a result, the second terminal 12 can be quickly separated from the first terminal 11 and the conduction between the two terminals can be instantaneously interrupted to prevent further overcharging or the like. _{F in = P 1 × Sa (} 3)

[0022] such as when the gas by decomposition of the electrolyte occurs, if the internal pressure P ₁ of the battery 1 increases greatly, the second terminal 12 moves further upwards. Then, as shown in FIG. 3, when the internal pressure receiving surface 121a is pushed up above the lower end of the groove 211, an internal gas discharge path G that connects the internal space K and the external space L is formed, and the internal gas is discharged. It can escape to the external space L. This makes the internal pressure P
When ₁ is lowered, as shown in FIG. 4, the second terminal 12 to a position where the F _in the F _out balance is lowered, it is blocked from the internal space K and the external space L. In the case where the gas generation does not stop even after the interruption of the current, the state shown in FIG. 3 and the state shown in FIG. 4 are repeated, and the internal pressure P ₁ is maintained at a predetermined valve opening pressure or less. .

(3) Reuse of Battery When the battery 1 returns to the normal state after the operation of the safety mechanism, the battery 1 is in the state shown in FIG. 2 or FIG. Is disconnected from the terminal 12. To re-use the battery 1 is fully (and P ₁ = P ₀₎ Remove the internal pressure P ₁ by pulling the second terminal 12 by an external force to the position of FIG. 3, then a second terminal by an external force 12 may be pushed into contact with the first terminal 11.
Note that when the pressure rise was temporary thermal expansion of internal gases, omit the process of removing the internal pressure P _1, be re form contacts simply pushes the second terminal 12 Good. When the spring force is large, the contact is re-formed by the spring force without applying an external force.

(4) Other Embodiments The shape of the contact surface between the first terminal 11 and the second terminal 12 is as follows.
For example, as shown in FIG. 5A, the contact end surface 11a may be formed in a conical shape, and a concave portion having a corresponding shape may be provided on the internal pressure receiving surface 121a. Further, as shown in FIG.
1a may be spherical, and a concave portion having a corresponding curvature may be provided on the internal pressure receiving surface 121a. Further, as shown in FIG. 5 (c), the contact end face 11a is flat, and the internal pressure receiving face 121 is formed.
A concave portion having a taper may be provided at a. In these cases, even when the first terminal 11 is tilted and accommodated in the battery container 2 due to an assembling error or the like, the first terminal 11 is fitted by fitting the contact surfaces of both terminals. Is positioned, and the contact end face 11a and the internal pressure receiving face 121a can be brought into close contact with each other.

Further, as shown in FIG. 5D, a conductive cushioning member 123 is fixed to the internal pressure receiving surface 121a and pressed against the first terminal 11 to match the shape of the contact end surface 11a. May be configured to be compressed. As the material of the cushioning member 123, a metal foam, steel wool, or the like can be used. In addition, it is preferable that the shape of the contact surface is flat as in the above-described embodiment, because the forming of the member and the mirror finishing of the contact surface are easy.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a normal state of a safety mechanism in a sealed battery according to an embodiment.

FIG. 2 is a cross-sectional view illustrating a state of the safety mechanism in the sealed battery according to the embodiment when current is interrupted.

FIG. 3 is a cross-sectional view showing a state of the safety mechanism in the sealed battery according to the embodiment when an internal gas release path is formed.

FIG. 4 is a partial cross-sectional view showing a state in which the internal pressure and the external pressure are balanced after the formation of the internal gas discharge passage in the safety mechanism in the sealed battery according to the embodiment.

FIGS. 5A to 5D are cross-sectional views showing various shapes of a contact portion between a first terminal and a second terminal in the sealed battery of the present invention.

FIG. 6 is a cross-sectional view showing a normal state of a safety mechanism in a conventional sealed battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1; Battery (closed type battery), 10; Electrode body, 11; 1st terminal, 11a; Contact end surface, 12; 2nd terminal, 121;
Disk portion, 121a; internal pressure receiving surface, 121b; external pressure receiving surface, 1
3; coil spring (elastic member), 15; fixing member, 15
1; groove portion; 2; battery container; 21; cylinder portion; 211;
Groove, K: Internal space, L: External space, M: Spring chamber, G;
Internal gas discharge path, P ₀ : atmospheric pressure, P ₁ : internal pressure, F ₀ : spring force.

Claims (3)

[Claims] 1. A sealed battery provided with a safety mechanism for interrupting conduction between an electrode body and the outside when an internal pressure rises, comprising: a first terminal fixed to the electrode body; A battery container that accommodates the first terminal, a second terminal that is normally in surface contact with the first terminal and seals the internal space of the battery container, and a first terminal that is connected to the second terminal. An elastic member that applies a pressing force to the side, the second terminal is held so as to be able to reciprocate in a direction in contact with the first terminal and in a direction away from the first terminal. An inner pressure receiving surface on the side in contact with the first terminal, on which the internal pressure of the battery container is applied, and an external pressure receiving surface, on which the pressure of the external space is applied, separated from the first terminal by the increase of the internal pressure A sealed battery characterized by being movable in the direction in which the battery pack is mounted. 2. A sealed battery provided with a safety mechanism for interrupting conduction between an electrode body and the outside when an internal pressure rises, comprising: a first terminal fixed to the electrode body; A battery container for accommodating the first terminal, a second terminal which is normally in contact with the first terminal, and seals the internal space of the battery container, and the second terminal is connected to the first terminal. An elastic member that applies a pressing force to the first terminal, and the second terminal is held so as to be able to reciprocate in a direction in contact with the first terminal and in a direction away from the first terminal, An inner pressure receiving surface on which the internal pressure of the battery container is applied and which is on the side in contact with the first terminal, and an external pressure receiving surface on which the pressure of the external space is applied, are separated from the first terminal by an increase in the internal pressure. The second terminal is spaced apart from the first terminal. By moving in the direction, sealed battery, wherein the inner gas discharge path for communicating the said internal space and the external space is formed. 3. The sealed battery according to claim 1, wherein the contact surface between the first terminal and the second terminal in the normal state is mirror-finished.