KR100615160B1 - Cap assembly for a battery - Google Patents

Abstract

The present invention relates to a battery cap assembly capable of ensuring stability against pressure rise in a battery, the cap assembly comprising: a cap provided with a gas discharge hole; A cap cover forming an inner space with the cap and having a sealing hole; A lower metal plate forming an inner space with the cap cover and provided with a peripheral hole to allow internal gas to enter and apply internal pressure to the sealing hole; A PTC resistor attached between the cap cover and the lower metal plate to control a flow of current according to a change in temperature; A seal having a piston having a flange covering the sealing hole, a cylinder in which the piston can be guided and installed in the lower metal plate, and a shock absorbing spring in which the flange can be opened and closed according to a pressure applied to the sealing hole. An assembly;

Description

Cap assembly for a battery

1 is a partial cross-sectional view showing the structure of a secondary battery having one embodiment of a cap assembly according to the present invention.

2 is a cross-sectional view illustrating an embodiment of a cap assembly provided in the secondary battery of FIG. 1.

3 is an exploded perspective view of the cap assembly of FIG. 2.

4A illustrates a cross-sectional view of the PTC composite structure provided in the cap assemblies of FIGS. 2 and 3, and FIG. 4B illustrates a plan view thereof.

5 shows a cross-sectional view of another embodiment of a cap assembly according to the invention.

6 illustrates a cross-sectional view of a conventional secondary battery.

7 illustrates a cross-sectional view of the cap cap assembly of FIG. 6.

<Explanation of symbols for the main parts of the drawings>

10. Secondary Battery 13. Battery Case

13a. Neck 15. Electrode Assembly

17. Electrolyte 19. Gasket

21. Anode Tab

50,80. Cap assembly 53. Cap

55. Cap cover 57. PTC composite structure

60. Seal assembly 63. Cylinder

65. Piston 66. Tension spring

67. Sealing member

76.Compression spring 86.Reinforcement

The present invention relates to a secondary battery capable of ensuring stability against a pressure rise in the battery, and more particularly, a cap assembly having a PTC (positive temperature coeffiecient) resistor and an internal gas discharge mechanism for preventing a pressure increase. It relates to a secondary battery employing the same.

A secondary battery is basically manufactured by stacking a thin plate-shaped positive electrode plate and a negative electrode plate with a separator interposed therebetween, inserting it into a battery case, injecting and sealing an electrolyte solution therein.

Such a secondary battery may be manufactured in various shapes according to a device requiring a power source, but a battery such as a square mold or a polygonal mold, for example, a square mold or a rectangular mold, is commonly used. Hereinafter, the cylindrical, cylindrical or polygonal battery will be referred to as a template battery.

FIG. 6 is a sectional view of a conventional cylindrical secondary battery, and FIG. 7 is a sectional view of a cap assembly of the secondary battery of FIG.

Referring to FIG. 6, in the cylindrical secondary battery 100, the electrode assembly 110 having the positive electrode plate 111, the separator 112, and the negative electrode plate 113 stacked in this order is wound in a spiral shape in the form of a roll. It is manufactured by being inserted into the case 120 and the electrolyte solution 115 is injected and then sealed. In addition, a cap assembly 130 is disposed above the case 120. The cap cover 137 is connected to the positive electrode tab 139 formed on the positive electrode plate 111 of the electrode assembly, and the negative electrode tab 140 formed on the negative electrode plate 113 of the electrode assembly has an inner surface of the case 120. Contact. Therefore, the cylindrical secondary battery 100 supplies a current by connecting the case 120 and the cap 133 to a predetermined external electric circuit (not shown).

However, in such a secondary battery, the internal temperature of the battery increases due to an abnormal use state such as battery short circuit or overcharge, and gas is generated to increase the pressure inside the battery.

For example, in a nickel hydrogen battery, when overcharge occurs, OH ⁻ in the electrolyte is decomposed to generate oxygen gas, thereby increasing the internal pressure of the battery. In addition, even in a lithium secondary battery using metal lithium or carbon as a negative electrode active material, when discharge or short circuit occurs, decomposition of the organic electrolyte solution is promoted with heat generation, thereby generating gas and increasing the internal pressure of the battery.

In addition, when overcurrent or overvoltage is applied to the sealed battery in the battery formation process, the internal pressure of the battery rises above the initial pressure set in the battery due to gas generation, thereby further reducing the performance of the battery.

 In this case, when the internal pressure of the battery increases, not only the depletion of the electrolyte may occur due to the swelling of the electrode plate, but also the electrolyte may leak to the periphery of the cap assembly, resulting in overall deterioration in performance and life characteristics of the battery.

Therefore, in view of the safety of the battery, the conventional secondary battery has a cap assembly 130 as shown in FIG. 7 in order to adjust the battery internal pressure within a predetermined range. The cap assembly 130 includes a cap 133, a cap cover 137, and a vent rubber 135, and discharge holes 133a for discharging gas to the outside of the battery in the cap 133. A through hole 137a is formed in a cap cover 137 attached to the cap 133, and a vent rubber 135 is inserted between the cap 133 and the cap cover 137. It was.

Looking at the gas discharge process of the cylindrical secondary battery having such a structure as follows.

When the internal pressure of the battery increases due to the formation process of the secondary battery or the overcharge, etc., the pressure elastic force of the vent rubber 135 sealing the through hole 137a formed in the cap cover 137 increases the pressure of the gas inside the battery. If not overcome, gas inside the battery is discharged to the outside of the battery through the through hole 137a and the discharge hole 133a, thereby reducing the battery internal pressure.

However, in such a secondary battery, when the compression ratio of the vent rubber 135 is 20% or more, the characteristics as an elastic body, for example, permanent compression ratio, rebound elastic modulus, etc., change, so that a predetermined battery is considered at the same time. The height of the vent rubber 135 is made larger than the diameter to withstand the internal pressure. In addition, the diameter and height of the cap 133, which also serves as an electrode terminal, are determined for compatibility with batteries. Therefore, increasing the height of the vent rubber 135 relatively increases the cap assembly height, resulting in a loss of the effective space in the battery.

In addition, when the height of the vent rubber 135 is relatively large, the vent rubber 135 is inserted in the process of inserting the vent rubber 135 or in the process of opening or closing the through hole 137a for the gas discharge. ) Bias will occur. When the bias occurs, the pressure applied to the bottom surface of the vent rubber 135 is generated, so that the vent rubber 135 is partially cured and the life of the battery is shortened.

In addition, the main cause of the internal pressure rise of the battery is related to the temperature rise inside the battery. In the case of the conventional cap assembly, charge and discharge are performed regardless of the temperature rise inside the battery. Therefore, since there is no control means for the temperature rise inside the battery, the deterioration of the battery continues with the temperature rise, and when the gas discharge by the vent rubber is not smooth, the battery may explode due to the continuous internal pressure rise of the battery. The stability of the battery, such as causing a flame or the like, is not guaranteed, and there is a problem in that the performance of the battery decreases due to an increase in leakage of the electrolyte when releasing the gas due to an increase in internal pressure.

The present invention is designed to solve the above problems, and prevents the increase of heat generation and internal pressure inside the battery and maintains the battery internal pressure within a certain range to enable the continuous use of the battery cap improved battery life and performance An object of the present invention is to provide an assembly and a secondary battery having the same.

Cap assembly according to one aspect of the present invention to achieve the above object: a cap provided with a gas discharge hole; A cap cover forming an inner space with the cap and having a sealing hole; A lower metal plate forming an inner space with the cap cover and provided with a peripheral hole to allow internal gas to enter and apply internal pressure to the sealing hole; And a piston having a flange covering the sealing hole, a cylinder in which the piston can be guided and installed in the lower metal plate, and a shock absorbing spring in which the flange can be opened and closed according to the pressure applied to the sealing hole. It includes a sealing assembly. In addition, the flange of the piston is provided with a cap assembly including a sealing member made of alkali-resistant rubber to suppress the chemical reaction with the electrolyte. Further, the cap assembly is attached between the cap cover and the lower metal plate, it may further include a PTC resistor for controlling the flow of current in accordance with the change in temperature.

And, the electrode assembly having a positive electrode plate and a negative electrode plate; A case into which the electrode assembly is inserted; An electrolyte solution injected into the case; A cap assembly according to one aspect of the present invention; And a gasket for inserting the cap assembly to seal the inside of the case.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a secondary battery as an embodiment of the present invention.

1 is a cross-sectional view of a secondary battery employing an embodiment of a cap assembly according to the present invention.

Referring to FIG. 1, the electrode assembly 15 is inserted into the case 13 by winding a separator 15c between a thin plate-shaped positive plate 15a and a negative plate 15b. After the electrolyte 17 is injected, the gasket 19 having the cap assembly 50 inserted therein is inserted into the upper part of the case 13 in which the neck 13a is formed, and then crimped. According to the cylindrical secondary battery 10 is manufactured.

The gasket 19 has a stepped cylindrical shape made of a flexible synthetic resin material, for example, polypropylene or polytetrafluoroethylene, and the cap assembly 50 is described below. Burs (not shown) are formed in a direction opposite to the direction in which the gasket 19 is fitted to the outer circumferential portion so that they are not easily separated once the gasket 19 is fitted. The lower part of the cap assembly 50 is connected to the positive electrode tab 21 of the positive electrode plate 15a.

FIG. 2 is a cross-sectional view illustrating an embodiment of a cap assembly inserted into a gasket of the cylindrical secondary battery of FIG. 1, and FIG. 3 is an exploded perspective view of the cap assembly of FIG. 2. 4A shows a cross-sectional view of the PTC composite structure of the cap assembly of FIG. 3, and FIG. 4B shows a plan view thereof. In the drawings, like reference numerals denote like members having the same function.

2 and 3, the cap assembly 50 includes a cap 53, a cap cover 55, a cylinder 63, a tension spring 66, and a piston 65 having a flange 65a, and A PTC composite structure 57 is provided.

Here, when the cylinder (63), the tension spring (66) and the piston (65a) with the flange (65a) as described later, the gas inside the battery inside the cap cover 55 and the case 13 When sealed, however, when the internal pressure of the battery becomes higher than the set value, the gas is controlled to enter and exit as an example of the sealing and pressure resistance control means. Hereinafter, this will be referred to simply as a sealing assembly 60 in order to avoid duplication of description.

4A and 4B, the PTC composite structure 57 is a ring-shaped PTC that exhibits a positive temperature coefficient resistance characteristic between a ring-shaped upper metal plate 57a and a flanged cylindrical lower metal plate 57c. The resistor 57b is attached and formed. In addition, since a PTC resistor is immediately attached to the cap cover 55 of FIGS. 2 and 3, a PTC composite structure without an upper metal plate is also possible. Here, the lower metal plate 57c is formed with a peripheral hole 57e through which gas inside the battery passes and a central hole 57d into which the cylinder 63 of FIGS. 2 and 3 is inserted and attached.

The metal plates 57a and 57c are made of a conductor having good conductivity, for example, nickel or copper, or a metal plated with nickel or copper. In addition, the PTC resistor 57b is made of a resin composition including a resin material in which carbon black or a similar material is dispersed therein, but may be used without limitation as long as it is commonly used in the technical field of the present invention. .

2 and 3, the PTC composite structure 57 is provided with a sealing assembly 60, a cap cover 55, and a cap 53, which will be described in detail as follows.

The cylinder 63 is inserted into and attached to the center hole 57d of the lower metal plate 57c, and the lower spring plate 57c or the cylinder is disposed on the outer circumference of the cylinder 63, for example, after the tension spring 66 is disposed. One end of the tension spring 66 is attached to a spring seat (not shown) provided at 63. In addition, between the cap cover 55 and the lower metal plate 57c, as shown in FIG. 5, a reinforcement having a hole through which gas can pass may be installed. In this case, the cap cover 55 and the lower part may be installed. It serves to reinforce the rigidity of the metal plate 57c.

A cap cover 55 having a sealing hole 55a is attached to the flange portion 58 of the PTC composite structure 57.

A piston 65 having a sealing member 67 is inserted into a lower surface of the sealing hole 55a and the cylinder 63 and inserted into a spring seat (not shown) provided in the piston 65 or the flange portion 65a. The other end of the tension spring 66 is attached. In this case, the tension spring 66 has an internal force, for example, an elastic force corresponding to 10 bar (bar). In addition, the radius of the flange portion 65a is larger than the radius of the sealing hole 55a so that the sealing hole 55a can be sealed by the flange portion 65a, and preferably, 1.3 to 1.5 times or more. . In addition, the sealing material 67 attached to the flange portion 65a of the piston 65 is a material that suppresses chemical reactions, effectively seals, and has excellent heat and electrical insulation, even in contact with an alkaline electrolyte, for example, ethylene propylene. Alkali-resistant rubber, such as rubber, fluororubber, and silicone rubber, is selected.

As such, when the cap cover 55 is attached to the flange portion 53b of the cap in which the gas discharge hole 53a is formed, the cap assembly 50 is provided as an embodiment of the present invention. Here, a burr may be formed at the outer circumference of the cap 53, the cap cover 55, the lower metal plate 57c or the upper metal plate 57a. In this case, the burr may be easily inserted into the gasket 19 of FIG. By not relaxing, the internal gas of the battery may be prevented from leaking between the gasket 19 and the cap assembly 50.

In the lower metal plate 57c of the PTC composite structure 57 of the cap assembly 50, as shown in FIG. 1, the positive electrode tab 21 formed on the positive electrode plate 15a of the electrode structure is formed by resistance welding, soldering, or the like. Attached.

The lower metal plate 57c, the PTC resistor 57b, the upper metal plate 57a, the cap cover 55, and the cap 53 are attached to the method as long as the conductivity is sufficiently maintained during charging and discharging of the battery. There is no limitation, and the above methods include soldering, resistance welding, ultrasonic welding, laser welding, electron beam welding, and bonding with a conductive adhesive. However, since it is important to protect the PTC resistor 57b and the sealing member 67 from heat, the attachment of the PTC resistor 57b and the attachment between the cap cover 55 and the cap 53 are bonded using a conductive adhesive. It is desirable to. The cap 53 and the cap cover 55 may be attached by bending the edge of the cap cover 55 by a crimping method.

Looking at the operation of the secondary battery employing the cap assembly according to an embodiment of the present invention as follows.

The positive electrode tab 21 of the positive electrode plate 15a is attached to the lower metal plate 57C of the PTC composite structure so that the cap assembly 50 becomes the positive electrode, and the negative electrode tab of the negative electrode plate 15b is attached to the inner surface of the battery case 13. The battery case 13 becomes a negative electrode.

When the secondary battery 10 is in a normal use state, the cap 53 and the battery case 13 of the cap assembly are connected to an external electric circuit to supply current.

However, when the secondary battery 10 is in an abnormal use state such as a battery short circuit or overcharge, the internal temperature of the battery rises, thereby increasing the resistance of the PTC resistor, and the set threshold value, for example, the battery pressure is approximately. When reaching a temperature exceeding 10 bar (bar), the resistance of the PTC resistor is rapidly increased to interrupt the flow of current. Therefore, overheating and pressure rise due to overcurrent are prevented by the action of the PTC resistor.

In the case where the PTC resistor is not functioning or the battery internal pressure due to gas generation is excessively increased, the sealing assembly 60 is operated to ensure the safety of the battery.

That is, the internal pressure is a predetermined elastic force of the tension spring 66 in the flange portion 65a of the piston 65 which seals the sealing hole 55a of the cap cover 55, for example, an elastic force corresponding to 10 bar (bar). When exceeding, the flange portion 65a of the piston 65 is spaced upwardly to release the sealing function of the sealing assembly 60, and the gas inside the battery is sealed with the sealing hole 55a of the cap cover 55 and the cap. It is discharged to the outside through the gas discharge hole 53a of 53.

In addition, when the internal gas of the battery is discharged to the outside and the internal pressure of the battery is reduced, the piston 65 is lowered under the elastic force of the tension spring 66, and the flange 65a of the piston 65 is lowered. The sealing hole 55a of the cap cover 55 is sealed by the sealing member 67 provided.

Further, when the internal temperature of the battery falls below the set threshold value, the resistance of the PTC resistor decreases, so that the function of the battery returns to normal.

5 shows a cross-sectional view of another embodiment of a cap assembly according to the invention. Here, the same reference numerals as the drawings shown above indicate the same member having the same function.

Referring to FIG. 5, as another embodiment according to the present invention, the cap assembly 80 includes a compression spring 76 between the cap 53 and the flange portion 65a. Here, in order to reinforce the rigidity of the cap cover 55 and the lower metal plate 57c, a reinforcement 86 having a hole 86a through which gas can pass may be provided.

According to such a structure, internal pressure acts on the flange part 65a of the piston 65 which seals the sealing hole 55a of the cap cover 55, and the pressure inside a battery is set value, for example, 10 atmospheres ( bar), the internal pressure of the battery overcomes the elastic force of the compression spring 76 to space the flange portion 65a of the piston 65 upward. Therefore, the gas inside the battery is discharged to the outside through the sealing hole 55a and the gas discharge hole 53a.

In such a cap assembly according to an aspect of the present invention, the tension spring 65 of Figure 2, and the compression spring 76 of Figure 5 are each merely exemplary as an example of the shock absorbing spring, the shock absorbing spring is an air pressure Alternatively, it is possible to maintain the pressure inside the battery below a predetermined value by interposing the hydraulic pressure between the piston 65 and the cylinder 63. Also, a rubber bellows or an air bellows may be used as the shock absorbing spring. Such a shock absorbing spring may be used without limitation as long as it can be used equally in the art as a means for controlling the breakdown voltage of the battery.

In addition, the present invention is not limited to the cylindrical secondary battery, and may be provided in a mold battery such as a polygonal mold battery by changing the shape of the cap assembly to match the shape of the battery case.

Accordingly, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Could be. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the cap assembly and the secondary battery having the same according to the present invention can obtain the following effects.

When the temperature inside the battery is above a certain value, the current flow is interrupted by the PTC resistor so that the internal pressure of the battery can be maintained within a certain range, and when the PTC resistor is not operated or the gas in the battery continues. When there is an increase in the internal pressure due to the generation, the sealing of the sealing assembly is secondarily released, thereby preventing the explosion of the battery and improving the stability of the battery. In addition, by using a cap assembly with PTC resistors and an open / close seal assembly, continuous use of the battery is ensured without the partial hardening, such as a bent rubber with a bias phenomenon, thereby improving battery life and improving its performance. .

Claims (14)

A cap provided with a gas discharge hole; A cap cover forming an inner space with the cap and having a sealing hole; A lower metal plate forming an inner space with the cap cover and provided with a peripheral hole to allow internal gas to enter and apply internal pressure to the sealing hole; And A piston having a flange covering the sealing hole, and the piston is inserted and coupled to guide the piston, and is installed between the cylinder installed on the lower metal plate, between the piston and the lower metal plate, or between the piston and the cap. And a sealing assembly having a buffer spring that can open and close the flange portion according to a pressure acting on the sealing hole. The method of claim 1, The shock absorbing spring is cap assembly, characterized in that the one end is attached to the inner surface of the piston, the other end is a tension spring attached to the inner surface of the lower metal plate. The method of claim 1, The shock absorbing spring cap assembly, characterized in that the one end is attached to the outer surface of the piston, the other end is a compression spring attached to the inner surface of the cap. The method according to claim 1, wherein Cap assembly, characterized in that the flange portion of the piston further comprises a sealing member made of alkali-resistant rubber to suppress the chemical reaction with the electrolyte. The method of claim 4, wherein Cap assembly further comprising a reinforcing material for reinforcing the rigidity between the cap cover and the lower metal plate. The method of claim 4, wherein And a PTC resistor attached between the cap cover and the lower metal plate to control a flow of current according to a change in temperature, wherein the sealing member is an electrical insulation. The method of claim 6, A cap assembly further comprising an upper metal plate between the cap cover and the PTC resistor. An electrode assembly having a positive electrode plate and a negative electrode plate; A case into which the electrode assembly is inserted; An electrolyte solution injected into the case; A cap provided with a gas discharge hole, A cap cover forming an inner space with the cap and having a sealing hole; A lower metal plate forming an inner space with the cap cover and provided with a periphery hole to allow internal gas to enter and apply internal pressure to the sealing hole; A piston having a flange covering the sealing hole, and the piston is inserted and coupled to guide the piston, and is installed between the cylinder installed on the lower metal plate, between the piston and the lower metal plate, or between the piston and the cap. A cap assembly having a sealing assembly having a buffer spring which can be opened and closed according to a pressure acting on the sealing hole; And And a gasket for inserting the cap assembly to seal the inside of the case. The method of claim 8, The buffer spring is a secondary battery, characterized in that one end is attached to the inner surface of the piston, the other end is a tension spring on the inner surface of the lower metal plate. The method of claim 8, The buffer spring is a secondary battery characterized in that one end is attached to the outer surface of the piston, the other end is a compression spring attached to the inner surface of the cap. The method according to claim 8, wherein The flange of the piston is a secondary battery, characterized in that the sealing member of the alkali-resistant rubber is attached to suppress the chemical reaction with the electrolyte. The method of claim 11, The secondary battery further comprises a reinforcing material for reinforcing rigidity between the cap cover and the lower metal plate. The method of claim 11, And a PTC resistor attached between the cap cover and the lower metal plate and controlling a flow of current according to a change in temperature, wherein the sealing member is an electrical insulation. The method of claim 13, The secondary battery further comprises an upper metal plate between the cap cover and the PTC resistor.

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