KR101450918B1 - Cap assembly characterized by high quality of sealing - Google Patents

Abstract

The present invention relates to a cap assembly of a cylindrical battery. More particularly, the present invention relates to a laminated body in which a top cap, a PTC element, and a safety vant are sequentially stacked and formed; And a gasket which surrounds the outer circumferential surface of the laminate and seals the capper, the cap assembly being characterized in that an adhesive material layer is provided between the laminate and the gasket. The secondary battery according to the present invention is excellent in the bonding force between the gasket and the outer circumferential surface of the laminated body in which the top cap, the PTC element, and the safety vault are laminated in order, and the electrolyte leakage from the inside of the battery to the outside can be prevented in advance, The safety of the battery can be greatly improved.

A top cap, a PTC element, a safety vent, a gasket, a cap assembly, an adhesive material layer, an epoxy resin

Description

[0001] CAP ASSEMBLY CHARACTERIZED BY HIGH QUALITY OF SEALING [0002]

The present invention relates to a cap assembly for a cylindrical battery, and more particularly, to a cap assembly for a cylindrical battery which is coated with an adhesive material between a gasket and an outer circumferential surface of a laminated body formed by sequentially stacking a top cap, a PTC element, To a cap assembly of a battery.

The secondary battery is classified into a cylindrical battery in which the case is cylindrical, a prismatic battery in which the case is square, and a pouch-type battery in which the case is thin laminate sheet, depending on the shape of the battery case.

Meanwhile, an electrode assembly is embedded in a battery case as a power-generating device capable of charging and discharging, which is composed of a lamination structure of a positive electrode / separator / negative electrode. The electrode assembly is composed of a long- sheet type positive electrode coated with an active material and a jelly- Type structure in which a plurality of positive electrodes and negative electrodes of a predetermined size are sequentially stacked with a separator interposed therebetween.

Among these, the jelly-roll type electrode assembly has advantages such as easy manufacture and high energy density per weight, and jelly-roll type electrode assembly is easily manufactured especially in a cylindrical battery case.

However, when the battery is charged and discharged, the jelly-roll type electrode assembly tends to undergo repeated expansion and contraction, and in this process, the stress is concentrated at the central portion, and the electrode contacts the metal center pin through the separator, . The organic solvent is decomposed by the heat generated due to the internal short circuit, so that gas is generated, and the battery can be ruptured by an increase in gas pressure in the cell. Such gas pressure rise inside the battery can occur even when an internal short circuit occurs due to an external impact.

In order to solve the safety problem of the battery, the cap assembly of the cylindrical battery includes a safety vent for discharging high-pressure gas, a PTC element for shutting off current at a high temperature, a current cut- Interrupt Device (CID), and a top cap that forms a protruding terminal for protecting the devices are fixed by a gasket.

FIG. 1 is a partial cross-sectional view showing an upper structure of a conventional cylindrical secondary battery.

Referring to FIG. 1, a battery 100 includes an electrode assembly 300 as a power generating element, an electrolyte injected into the can 200, a cap assembly 400 at an upper opening of the can 200, .

The cap assembly 400 includes a top cap 410 and a PTC device 420 for shutting off an overcurrent inside the gasket 500 for airtightness to be mounted on the upper beading portion 210 of the can 200, The safety bolt 430 is closely attached.

The top cap 410 protrudes upward to serve as a positive terminal by connection with an external circuit, and a plurality of through holes (not shown) for discharging gas are perforated. The safety vault 430 has its lower end connected to the positive electrode of the electrode assembly 300 through the current cut-off safety element 440 and the positive electrode lead 310.

The safety vest 430 is a thin conductive plate having a center portion thereof forming a downward depression 432 and two notches 434 having depths different from each other at the upper and lower bending portions of the depression 432 , And 436 are formed.

The current cut-off safety element 440, which cuts off the current when the pressure rises above the threshold value in the battery, is provided as a conductive plate under the safety vent 430. The material of the current cut-off safety element 440 is preferably made of the same material as the safety vest 430 and the auxiliary gasket 510 prevents the current cut-off safety element 440 and the safety vest 430 from being energized It is made of polypropylene (PP) series material.

For example, when the temperature of the battery 100 rises due to an internal short circuit due to various causes, overcharge, or the like, the amount of current to be energized is greatly reduced due to the increase in resistance of the PTC device 420. When the electrolytic solution is decomposed by the continuous rise of the temperature and the gas is generated and accordingly the internal pressure is increased, the indent portion 432 of the safety vent 430 is lifted to partially rupture the current cut-off safety element 440, Thereby securing safety. However, when the pressure is continuously increased, the notch 436 of the safety vent 430 is ruptured and the high-pressure gas is discharged to the outside through the battery 100 to secure safety.

Particularly, the structure of the cap assembly prevents the electrolyte in the battery from leaking to the outside by covering the peripheral surface of the safety vent, the PTC device, the CID, the top cap and the like. That is, if the electrolyte does not leak through the interface between the safety vest located at the innermost side of the battery and the gasket surrounding the outer periphery of the safety vent, even at the interface between the safety vest and the PTC device and the interface between the PTC device and the top cap, Leakage does not occur.

However, some electrolytic solution leaks through the interface between the gasket and the safety vent, due to the charging / discharging operation of the battery, dropping, external impact, etc., and the leaked electrolyte easily leaks out through the interface between the metal materials have. That is, the interfacial region between the metal materials is relatively inferior in adhesion, so that the electrolyte introduced into the interface of the metal materials can easily leak to the outside as compared with the interface portion of the gasket and the related elements.

Also, a method of joining a top cap assembly used in a conventional cylindrical battery is a method in which the interior of the battery is sealed by simply pressing the assembly and the can by mechanical pressing. However, in this case, not only is it not constantly sealed according to the degree of mechanical pressing, but leakage is generated due to not being sealed when the binding force is weak. Particularly, there is a high possibility that the path of the main leak is among the various attachments located in the middle part of the top cap assembly.

Therefore, there is a high need for a technique capable of reducing the leakage of electrolyte from the cap assembly.

In this connection, Japanese Patent Application Laid-Open No. 2006-286561, Japanese Patent Application Laid-Open No. 2005-100927, Japanese Patent Application Laid-Open No. 2002-373711 and the like discloses a cap assembly provided with a gasket under the top cap. However, the cap assembly disclosed in these applications is not easy to manufacture because of the complicated shape of the gasket sealing the outer circumferential surface of the safety elements, So that the above problems are not solved fundamentally.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive studies and various experiments and have found that by applying an adhesive material between the outer circumferential surface of a laminate formed by sequentially laminating a top cap, a PTC device, and a safety band, and a gasket, In addition, it has been confirmed that leakage can be prevented in advance by completely blocking the path from the inside of the battery to the outside through the adhesive material, and the present invention has been accomplished.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art,

A laminated body in which a top cap, a PTC element, and a safety vant are sequentially stacked; And

The cap assembly includes a gasket which surrounds the outer circumferential surface of the laminate and seals the capper. The cap assembly includes an adhesive material layer between the laminate and the gasket.

Further, in the present invention, there is provided a top cap assembly characterized in that the adhesive material is an epoxy resin.

Also, in the present invention, the adhesive material layer has a thickness within a range of 1 to 100 mu m.

Also, there is provided a cylindrical secondary battery including the top cap assembly of the present invention.

The secondary battery according to the present invention is excellent in the bonding force between the gasket and the outer circumferential surface of the laminate formed by sequentially stacking the top cap, the PTC device, and the safety vents, Ultimately, the safety of the battery can be greatly improved.

Hereinafter, the present invention will be described in detail.

According to the present invention,

A laminated body in which a top cap, a PTC element, and a safety vant are sequentially stacked; And

And a gasket which surrounds the outer circumferential surface of the laminate and seals the gasket, characterized in that an adhesive material layer is provided between the laminate and the gasket.

The interfacial region between the stacked body and the gasket in which the top cap, the PTC element, and the safety vent are stacked in this order has a high possibility of electrolyte leakage as described above, and an adhesive material layer is formed between the stack and the gasket The safety of the battery can be greatly improved by preventing the electrolyte from leaking from the interface between the metal materials until the safety vent is short-circuited.

That is, even though the electrolytic solution passes through the interface between the safety vent located inside the battery and the gasket surrounding the outer periphery of the battery, the electrolyte can not directly flow into the interface between the safety vent and the PTC device and the interface between the PTC device and the top cap, It is necessary to pass through the interface of the material layer, so that leakage of the electrolyte substantially can be prevented.

The adhesive material is not particularly limited as long as it is a material having excellent sealing property and electrical insulation property. An example of such an adhesive material is an epoxy resin.

The thickness of the adhesive material layer interposed between the laminate and the gasket may be preferably 1 to 100 占 퐉 so as to prevent leakage of the electrolyte at the mutual interface at which the members are in contact. Here, the thickness of the adhesive material layer refers to the width between the laminate and the gasket.

If the thickness of the adhesive material layer is too small, it may not be difficult to provide a predetermined electrical insulation and sealing property. Conversely, if it is too thick, it may lead to an increase in size of the battery.

The thickness of the safety vent may vary depending on the material, structure, etc., and is not particularly limited as long as it can be discharged while being ruptured when a predetermined high pressure is generated, preferably 0.2 to 0.6 mm.

The thickness of the PTC device may also vary depending on material, structure, etc., and may preferably be 0.2 to 0.4 mm. However, if the thickness of the PTC device is too large, the internal resistance increases, and the size of the battery increases, thereby reducing the capacity of the battery compared to the same standard. On the contrary, the thickness of the PTC element is too thin, it is difficult to exhibit a desired current blocking effect at a high temperature, and it may be destroyed by a weak external impact. Therefore, the thickness of the PTC device can be appropriately determined within the above range in consideration of these points in combination.

The thickness of the top cap portion in contact with the top surface of the PTC device is not particularly limited as long as it can protect the elements of the cap assembly from external pressure, preferably 0.3 to 0.5 mm. If the thickness of the top cap portion is too thin, it is difficult to exhibit a predetermined mechanical rigidity. Conversely, if it is too thick, the battery capacity may be reduced to the same standard due to increase in size and weight.

The gasket is made of a resilient material that is electrically insulative. Such a material is not particularly limited as long as it is a material exhibiting electrical insulation, predetermined elasticity, and durability. For example, polypropylene (PP) can be used.

The present invention also provides a secondary battery in which a wound type electrode assembly ('jelly-roll') is embedded in a cylindrical can with an electrolyte impregnated therein, and a cap assembly of the above structure is mounted on the upper end of the cylindrical can do.

In general, in the structure of a cylindrical secondary battery, a positive electrode tab welded to a positive electrode foil of a jelly-roll type electrode assembly is welded to a cap assembly and connected to a protruding terminal at an upper end of the battery, Cylindrical can), so that the can itself constitutes a negative terminal. The electrolyte is injected in the state where the mounting is performed, and the cap assembly is mounted on the open upper end of the can to seal the can, thereby completing the cylindrical battery. The material of the cylindrical can is not particularly limited, and preferably, it may be formed of any one of stainless steel, steel, aluminum or its equivalent.

The battery according to the present invention may preferably be a lithium secondary battery having high energy density, discharge voltage, and output stability. Such a lithium secondary battery is composed of a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte containing a lithium salt, and the like.

The positive electrode is prepared, for example, by applying a mixture of a positive electrode active material, a conductive material and a binder on a positive electrode current collector, and then drying the resultant. Optionally, a filler may be further added. The negative electrode is also manufactured by applying a negative electrode material onto the negative electrode collector and drying the same, and if necessary, the above-described components may further be included.

The separation membrane is interposed between the cathode and the anode, and an insulating thin film having high ion permeability and mechanical strength is used.

The lithium salt-containing nonaqueous electrolyte solution is composed of a nonaqueous electrolyte and a lithium salt. As the nonaqueous electrolyte solution, a liquid nonaqueous electrolyte, a solid electrolyte, and an inorganic solid electrolyte are used.

The collector, the electrode active material, the conductive material, the binder, the filler, the separator, the electrolyte, and the lithium salt are well known in the art, and a detailed description thereof will be omitted herein.

The lithium secondary battery according to the present invention can be manufactured by a conventional method known in the art. That is, a porous separator may be inserted between the anode and the cathode, and an electrolyte may be injected into the separator.

The anode can be produced, for example, by applying a slurry containing a lithium transition metal oxide active material, a conductive material and a binder as a cathode active material on a collector, followed by drying and rolling, as described above. Similarly, the negative electrode can be produced, for example, by applying a slurry containing a carbon active material, a conductive material and a binder as a negative electrode active material on a thin current collector and then drying the negative current collector as described above.

Hereinafter, the contents of the present invention will be described in detail with reference to the drawings according to one embodiment of the present invention, but the scope of the present invention is not limited thereto.

2 is a schematic cross-sectional view illustrating an upper structure of a cylindrical rechargeable battery according to an embodiment of the present invention.

2, in a cap assembly 400a of a secondary battery 100a according to the present invention, a current cutoff safety element 440 for cutting off a current when a high voltage is generated in a battery is connected to a lower portion of a safety vest 430, The PTC device 420 for blocking the current at the time of high temperature is mounted in an annular shape on the upper part of the safety vents 430 and has a through hole for discharging gas and a top cap 410 for forming a protruding terminal, 420, and the gasket 500 is the same as the conventional battery 100 of FIG. 1 in that the gasket 500 is formed so as to surround and seal the outer circumferential surface 610 of the elements.

However, a layer formed of an epoxy resin, which is an elastic material of electrical insulation, is provided between the stacked body and the gasket, so that the electrolytic solution is supplied to the cap assembly (not shown) until the safety vent 430 ruptures 400 to prevent the liquid from leaking to the upper portion of the apparatus.

FIG. 3 is a partial cross-sectional schematic view of an upper structure of a cap assembly in a cylindrical secondary battery according to an embodiment of the present invention.

3, the height of the adhesive material layer 600 is equal to the sum of the thickness of the PTC device 420, the top cap 410, and the safety vault 430, so that the cap assembly 400 And minimizes the spacing space between the lower end of the gasket 500 and the adhesive material layer 600 and maximizes the mutual sealing force.

The interface S2 between the safety vent 430 and the PTC device 420 and the interface S3 between the PTC device 420 and the top cap 410 are separated from each other by the adhesive material layer 600, The interface S2 and the interface S3 can be formed only through the adhesive material layer 600 even if the electrolyte inside the battery flows into the interface S1 between the lower end surface of the safety vent 430 and the gasket 500. [ So that it is practically impossible to discharge the electrolyte from the outside.

Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example

A first notch having a diameter of 9.6 mm and a thickness of 0.10 mm was formed on an aluminum plate having an outer diameter of 16 mm and a thickness of 0.3 mm and a second notch having a diameter of 4 mm and a thickness of 0.06 mm was formed, A safety vent was made to have a protruding indent.

Further, six through-holes each having a diameter of 1.5 mm were drilled radially into an aluminum plate having an outer diameter of 11 mm and a thickness of 0.5 mm, and a protrusion having a diameter of 1.53 mm and a protrusion height of 0.20 mm was formed at the center. Then, three through-holes each having a width of 0.6 mm and a circumferential length of 2.61 mm were drilled at a distance of 1.5 mm from the center of the central projection, and a notch having a thickness of about 70 탆 was formed on each of the bridges connecting the through- .

The CID was inserted into an auxiliary gasket made of polypropylene along the outer circumferential surface thereof and the bottom surface of the recess of the safety vent was laser welded to the upper surface of the projection.

After forming a laminate through an annular PTC element between the top cap and the safety vant produced above, the epoxy resin was melted and applied on the outer circumferential surface of the laminate. Before the epoxy resin was hardened, a safety vent, a PTC element and a top cap were wrapped with a gasket to prepare a cap assembly.

Further, a jelly-roll type electrode assembly in which a porous separator of polyethylene is interposed between a positive electrode made of lithium cobalt oxide and a negative electrode made of graphite is inserted into a cylindrical can, and the upper surface of the can is fixed by beading. The cap assembly was sandwiched and the top of the can was pressed inward to crimp the gasket to finally produce a cylindrical secondary battery.

Comparative Example

A cylindrical secondary battery was manufactured in the same manner as in Example except that no epoxy resin was applied to the outer surface of the laminate.

Experimental Example  - Leakage pressure and Banting  Pressure measurement experiment

CID short circuit pressure, electrolyte leakage pressure, and bending pressure were measured while applying pressure to the cell up to 20 kgf with the cell prepared in the example and the cell prepared in the comparative example being inverted.

The results are shown in Table 1 below.

CID short-circuit pressure
(kgf / cm2) Leakage pressure
(kgf / cm2) Venting pressure
(kgf / cm2) Example 10.3 18.5 18.5 Comparative Example 10.1 15.1 18.7

As shown in Table 1, the leakage current of the electrolyte did not occur in the battery of the example of the present invention until the venting of the safety vent by the short circuit. On the other hand, in the battery of the comparative example, leakage of the electrolyte occurred before venting of the safety vent by short circuit. This is presumably because the epoxy resin applied between the laminate and the gasket enhances the adhesive strength and forms a waterproof layer so that the electrolyte does not leak.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

1 is a schematic cross-sectional view showing an upper structure of a conventional cylindrical secondary battery.

2 and 3 are cross-sectional schematic views illustrating an upper structure of a cylindrical rechargeable battery according to an embodiment of the present invention.

Claims (4)

A laminated body in which a top cap, a PTC element, and a safety vant are sequentially stacked; And The cap assembly includes a gasket which surrounds the outer circumferential surface of the laminate, and is sealed, wherein an adhesive material layer having a thickness within a range of 1 to 100 mu m is applied between the gaskets, Wherein the height of the adhesive material layer is equal to the sum of the thicknesses of the laminate. The cap assembly of claim 1, wherein the adhesive material is an epoxy resin . delete A cylindrical secondary battery comprising the cap assembly of claim 1 or claim 2.

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