KR101754484B1 - Cap assembly and secondary battery including the same - Google Patents

Abstract

The present invention relates to a laminate comprising a top cap; And a gasket surrounding and sealing the outer circumferential surface of the laminate, wherein the gasket includes a coating film on a side of a gasket in contact with the laminate, and the coating film comprises a water-swelling polymer, and The present invention relates to a secondary battery.
The cap assembly according to the present invention significantly improves the hermeticity between the outer peripheral surface of the laminate including the top cap and the gasket and prevents electrolyte leakage from the inside of the battery to the outside in advance and ultimately greatly improves the safety of the battery There is an effect that can be made.

Description

[0001] CAP ASSEMBLY AND SECONDARY BATTERY INCLUDING THE SAME [0002]

The present invention relates to a cap assembly and a secondary battery including the cap assembly.

The secondary battery is classified into a circular battery having a circular shape, a square battery having a square shape, and a pouch-shaped battery having a laminated sheet having a thin case according to the shape of the battery case.

Meanwhile, the battery case has an electrode assembly as a power generating element capable of charging / 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 them, they are easy to manufacture and have a high energy density per weight, and are easily manufactured in a circular battery case, and a jelly-roll type electrode assembly is widely produced.

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 as described above, the cap assembly of the circular battery includes a safety vent for discharging high-pressure gas, a PTC element for shutting off current at a high temperature, An interrupter device (CID), and a top cap for forming a protruding terminal for protecting the elements are fixed by a gasket.

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

Referring to FIG. 1, a secondary battery 10 includes an electrode assembly 30 as a power generating element inserted in a can 20, an electrolyte is injected into the electrode assembly 30, a cap assembly 40 is mounted on an upper opening of the can 20, .

The cap assembly 40 includes a top cap 41 and a PTC element 42 for blocking the overcurrent inside the gasket 50 to be mounted on the upper beading portion 21 of the can 20, The safety bolt 43 is installed closely.

The top cap 41 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 lower end of the safety vent 43 is connected to the positive electrode of the electrode assembly 30 through the current interrupter safety element 44 and the positive electrode lead 31.

The safety vent 43 is a thin electrically conductive plate having a central downwardly directed indentation 43a and two notches 43b with depths different respectively at the upper and lower bend portions of the indentation 43a And 43c are formed.

The current cut-off safety device 44, 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 vest 43. The material of the current cut-off safety element 44 is preferably made of the same material as the safety vest 43 and the auxiliary gasket 51 prevents the current cut-off safety element 44 and the safety vest 43 from being energized It is made of polypropylene (PP) series material.

For example, when the temperature of the battery 10 rises due to an internal short circuit due to various causes, overcharging or the like, the amount of current to be energized is greatly reduced due to the increase in resistance of the PTC device 42. When the electrolytic solution is decomposed by the continuous rise of the temperature and gas is generated and accordingly the internal pressure is increased, the indentation portion 43a of the safety vent 43 is lifted and the current interruption safety element 44 is partially ruptured, Thereby securing safety. However, when the pressure is continuously increased, the notches 43b and 43c of the safety vent 43 are ruptured, and the high pressure gas is discharged to the outside of the battery 10 to secure safety.

Particularly, the structure of the cap assembly prevents the electrolyte in the battery from leaking to the outside by covering the outer 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 on the innermost side of the cell and the gasket surrounding the outer periphery of the safety vent, the interface between the safety vent and the PTC device, the interface between the PTC device and the top cap Electrolyte 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.

In addition, a method of joining a top cap assembly used in a conventional circular 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. In particular, there is a high likelihood that the path of the main leakage will be between the various attachments located in the middle of the top cap assembly.

Therefore, there is a high need for a technique capable of reducing the leakage of the electrolyte solution in the cap assembly and suppressing the inflow of water.

Korean Patent Publication No. 2007-0071235 (published on July 07, 2007)

SUMMARY OF THE INVENTION The first technical problem to be solved by the present invention is to provide a method for manufacturing a secondary battery which comprises a coating film containing a water swelling polymer on a gasket, And is capable of preventing leakage of electrolyte from the inside of the battery to the outside in advance.

A second technical problem to be solved by the present invention is to provide a secondary battery including the cap assembly.

According to an aspect of the present invention, there is provided a laminated body including a top cap; And a gasket surrounding and sealing the outer circumferential surface of the laminate, wherein the gasket includes a coating film on the side of the gasket in contact with the laminate, and the coating film comprises a water swelling polymer having a water swelling degree of 30% or more In cap assembly.

According to another embodiment of the present invention, there is provided a secondary battery, a battery module, and a battery pack including the cap assembly.

Other details of the embodiments of the present invention are included in the following detailed description.

The cap assembly according to the present invention is excellent in bonding force by forming a coating film of a water-swellable polymer between the outer circumferential surface of the laminate including the top cap and the gasket and further between the gasket and the can, Electrolyte leakage can be prevented in advance, and the safety of the battery can ultimately be greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
1 is a schematic cross-sectional view showing an upper structure of a conventional circular secondary battery.
2 is a schematic cross-sectional view illustrating an upper structure of a circular secondary battery according to an embodiment of the present invention.
3 is a schematic cross-sectional view schematically showing the structure of a cap assembly according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

In the conventional cap assembly, the mutual interfacial region between the laminate and the gasket in which the top cap, the PTC device, and the safety vault are laminated in order is highly likely to leak electrolytic solution and easily inflow water, The safety and performance of the apparatus may be deteriorated.

In contrast, in the present invention, a coating film containing a water-swellable polymer is formed on the side of the gasket in contact with the laminate. Thus, when the secondary battery is used for a long period of time, the gap between the outer periphery of the laminate including the top cap and the gasket, The leakage of the electrolyte from the inside of the battery to the outside can be prevented in advance, and as a result, the safety and performance characteristics of the secondary battery can be greatly improved.

That is, a cap assembly according to an embodiment of the present invention includes: a laminate including a top cap; And a gasket surrounding and sealing the outer circumferential surface of the laminate, wherein the gasket includes a coating film on a side of a gasket in contact with the laminate, and the coating film includes a water swelling polymer having a water swelling degree of 30% or more.

Further, in the cap assembly according to an embodiment of the present invention, the gasket may include a water swelling polymer on the outer surface of the gasket not contacting the laminate, specifically, the gasket contacting the can of the secondary battery And may further include a coating film. Furthermore, the coating film may be formed to surround all the outer circumferential surface of the gasket.

In the cap assembly according to an embodiment of the present invention, the water swelling polymer contained in the coating film formed on the gasket is a polymer that is swellable by moisture present in the air. When the coating film containing the water swelling polymer is formed, the gap between the outer circumferential surface of the layered product including the top cap and the gasket, and the gap between the gasket and the can are more closely adhered to each other as compared with the case where the coating film is formed with the usual polymer material The gap between them can be minimized. In addition, the water swelling polymer can maintain the expanded state for a long period of time, and the adhesion can be stably maintained for a long time.

Specifically, the water swelling polymer may have a water swelling degree of 30% or more, more specifically 50% or more, more specifically 60% to 90%. If the water swelling degree is less than 30%, the effect of improving water swelling is not sufficient.

In the present invention, the water swelling degree of the water swelling polymer is measured by measuring the film thickness after immersing the polymer in pure water for 10 minutes, using a film thickness measuring instrument such as ellipsometry (VASE, manufactured by JA Woollam) The ratio of the film thickness after immersion to the film thickness before immersion is expressed as a percentage.

In addition, the water swelling polymer may be a polymer in the form of a hydrogel. When the water swelling polymer has a hydrogel shape, it can exhibit a high water absorption, so that it can be blocked with higher efficiency even if leakage or water inflow of the electrolyte occurs. Since the hydrogel having the moisture again has a high water holding capacity, there is no fear of moisture release into the interior of the secondary battery, and the water can be swollen to increase the adhesion, so that the moisture can be blocked further.

The water-swellable polymer may have an excellent absorbency and a strength enough to withstand the pressure at the time of clamping, specifically a strength of 0.6 to 3.0 MPa.

The water swelling polymer may be polyolefins such as polyhydroxyethylmethylacrylate (polyHEMA or PHEMA), polyethyleneglycol (PEG), polyvinylpyrrolidone, and the like. Polyoxyethylene, polyethylene oxide (PEO), polyethylene glycol methacrylate (PEGMA), polyethylene glycol dimethacrylate (PEGDMA), polyethyleneglycol diacrylate (PEGDA), polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), polyimide, polyacrylate or polyurethane. Any one or a mixture of two or more of them may be used.

Among these, polyhydroxyethylmethyl acrylate, polyethylene glycol, polyoxyethylene, polyethylene oxide, polyethylene glycol methacrylate, polyethyleneglycol dimethacrylate, polyacrylic acid dimethacrylate, , Polyethyleneglycol diacrylate, polyvinylpyrrolidone, and polyacrylate have excellent water swellability and strength properties, and have excellent film-forming properties in forming a coating film, so that uniform thickness The coating film can be formed and the adhesion with the gasket is more excellent.

In the cap assembly according to an embodiment of the present invention, the method of forming the coating film including the water swelling polymer is not particularly limited, but a conventional polymer coating method such as spray coating or electrostatic coating is used .

In the cap assembly according to an embodiment of the present invention, the water swelling degree of the coating film including the water swelling polymer may be 0.5% to 2%, and considering the water swelling degree of the coating film, It may be contained in an amount ranging from 0.5% by weight to 4% by weight based on the total weight of the cap assembly when the degree of swelling of the self is 50%. If the water swelling degree of the coating film is less than 0.5% by weight, the improvement effect of the use of the water-swellable polymer such as deterioration of the pilling property between the gasket and the laminate is insignificant. If the water swelling degree of the coating film exceeds 4% by weight, Resulting in deterioration of battery performance.

In addition, in the cap assembly according to an embodiment of the present invention, the coating film may vary depending on the size or width of the secondary battery, or the size or width of the cap assembly. Specifically, the coating film may be formed in a thickness range of 1 占 퐉 to 100 占 퐉. Here, the thickness of the coating film means, for example, the distance between the gasket and the laminate, that is, the width.

If the thickness of the coating film is too small, the water swelling degree may be too small. Therefore, the effect of blocking the leakage of water from the outside of the battery may be insufficient, Is more than 100 mu m and is too thick, there is a possibility that the size of the secondary battery will increase.

Meanwhile, in the cap assembly according to an embodiment of the present invention, the stacked body may be a stacked body in which a top cap, a PTC element, and a safety vault are sequentially stacked.

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

Further, the thickness of the PTC device may also vary depending on material, structure, etc., and may be 0.2 mm 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, have. If the thickness of the top cap portion is too thin, it is difficult to exhibit a predetermined mechanical rigidity. On the contrary, if it is too thick, battery capacity can be reduced to the same standard due to increase in size and weight.

On the other hand, the gasket may be a material that is commonly used, and specifically, a polymer material having electrical insulation, elasticity, and durability may be used. The polymer material may be a polyolefin-based polymer such as polypropylene.

According to another embodiment of the present invention, there is provided an electrochemical device including the cap assembly. The electrochemical device may be specifically a battery or a capacitor, and more specifically, may be a secondary battery having a high energy density, a discharge voltage, and an output stability.

Specifically, the rechargeable battery includes a circular can loaded with a wound electrode assembly (jelly-roll) in an electrolyte-impregnated state, and the cap assembly of the structure may be mounted on the upper end of the circular can.

In general, in a structure of a circular 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. When the electrolyte is injected in such a state that the battery is mounted, the cap assembly is mounted on the open upper end of the can to seal the battery, thereby completing the circular battery.

In the secondary battery according to an embodiment of the present invention, the material of the circular can is not particularly limited, and specifically, it may be formed of any one of stainless steel, steel, aluminum or its equivalent.

Further, in the secondary battery according to an embodiment of the present invention, the electrode assembly includes a positive electrode, a negative electrode facing the positive electrode, and a separator interposed between the positive electrode and the negative electrode.

The positive electrode is prepared, for example, by coating a positive electrode current collector with a mixture of a positive electrode active material such as a lithium transition metal oxide, a conductive material and a binder, and then drying the resultant. Optionally, a filler may be further included. The negative electrode is also manufactured by applying a negative electrode active material such as a carbon active material onto the negative electrode collector and drying the same, and if necessary, the above-described components may further be included. In addition, 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.

Also, in the secondary battery according to an embodiment of the present invention, the electrolyte used in the present invention may be an organic-based liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, A solid inorganic electrolyte, a molten inorganic electrolyte, and the like, but are not limited thereto. Specifically, the nonaqueous electrolyte solution containing a lithium salt may include a nonaqueous electrolyte and a lithium salt.

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 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.

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

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

2, a cap assembly 600 of a secondary battery 100 according to an embodiment of the present invention includes a laminate 400 including a top cap, and a cap 400 surrounding and sealing the outer periphery of the laminate 400 And a gasket (500). The gasket 500 includes a coating film 700 including a water swelling polymer having a water swelling degree of 30% or more on the surface side of the gasket 500 contacting the laminate body 400.

The stack 400 may include a top cap 410 and may optionally further include a PTC device 420 and a safety vault 430. In the stacked body 400, a current cutoff safety element 440 for cutting off a current when a high voltage is generated in the battery is connected to a lower portion of the safety vent 430, and a PTC device 420, A top cap 410 is mounted on the PTC device 420 and a gasket 500 is mounted on the PTC device 420. The gasket 500 is mounted on the PTC device 420, And is formed so as to enclose and seal the outer circumferential surfaces of the elements.

The coating film 700 including the water swelling polymer may be coated on the inner side of the gasket 500.

That is, the cap assembly 600 includes a coating film 700 including the water swelling polymer between the gasket 500 and the laminate including the top cap 410, the PTC device 420 and the safety vents 430 A gasket may be provided.

The gasket 500 having the coating film 700 including the water swelling polymer prevents the electrolyte from leaking to the upper portion of the cap assembly 600 until the safety vent 430 ruptures due to the generation of a high pressure in the secondary battery, can do.

3, the gasket 500 includes the outer surface of the gasket 500 and the top cap 410, the PTC device 420, and the safety vents 430 (700a, 700b) including a water swelling polymer are formed between the layered product (400) and the layered product (400).

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 included in the coating film 700b Even if the electrolyte inside the battery flows into the interface S1 between the lower end surface of the safety can 430 and the gasket 500 when the water swelling polymer swells due to moisture present in the air, it must pass through the swelled coating film 700b It is possible to substantially reach the interface S2 and the interface S3 so that the electrolyte can not flow out to the outside and the can of the secondary battery and the cap assembly can be more closely contacted to prevent leakage of the electrolytic solution.

Therefore, the cap assembly according to an embodiment of the present invention is excellent in the bonding force between the outer surface of the layered product including the top cap and the gasket and between the gasket and the can, and prevents electrolyte leakage from the inside of the battery to the outside And ultimately, the safety of the battery can be greatly improved.

As described above, since the secondary battery including the cap assembly according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention ratio, it can be applied to portable devices such as mobile phones, notebook computers, digital cameras, and hybrid electric vehicles electric vehicle (HEV), and the like.

According to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell and a battery pack including the same.

The battery module or the battery pack may include a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); Or a power storage system, as shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

[ Example  One]

Polyvinyl alcohol (water swelling degree: 60%) was coated on the surface side of the polypropylene type gasket to be in contact with the laminate during the manufacture of the cap assembly by using a spray coating method to form a coating film (thickness range: 30 to 50 탆, Average thickness: 40 占 퐉). The polyvinyl alcohol was contained in the form of a hydrogel in the coating film formed at this time.

3, the top cap 410, the PTC device 420, and the safety vents 430 are successively stacked and assembled to form a laminate. Then, both ends of the top cap 410, the PTC device 420, Sealed with a manufactured gasket, and clamped and pressed to fabricate a cap assembly.

[ Example  2]

Polyhydroxyethylmethylacrylate (water swelling degree: 90%) was used as the water swelling polymer, and the surface side of the polypropylene-based gasket to be in contact with the laminate at the time of manufacturing the cap assembly and the contact with the can The cap assembly was manufactured in the same manner as in Example 1 except that a coating film was formed on the side of the gasket to have a thickness range of 30 to 50 占 퐉 and an average thickness of 40 占 퐉.

[ Comparative Example  One]

A cap assembly was produced in the same manner as in Example 1 except that no coating film was formed on the outer circumferential surface of the gasket.

[ Comparative Example  2]

Except that a coating film (thickness range: 30 to 50 탆, average thickness: 40 탆) of polyacrylic acid (water swelling degree: 10%) was formed on the outer peripheral face of the gasket by the same method as in Example 1 Cap assembly.

[ Manufacturing example  1 and 2]

LiNi _{0 . 6} Co _{0 . 2} Mn _{0 . 2} O ₂ cathode active material, a carbon black conductive material and a PVdF binder in a N-methylpyrrolidone solvent in a weight ratio of 90: 5: 5 to prepare a composition for forming an anode (viscosity: 5000 mPa · s) Coated on an aluminum current collector, dried and rolled to prepare a positive electrode.

In addition, as a negative electrode active material, artificial graphite, MCMB (mesocarbon microbead), carbon black conductive material and PVdF binder were mixed in a N-methylpyrrolidone solvent in a weight ratio of 85: 10: 5 to prepare a composition for forming an anode, This was applied to the entire copper collector to prepare a negative electrode.

After the electrode assembly was manufactured through the porous polyethylene separator between the anode and the cathode thus prepared, the electrode assembly was positioned inside the battery case, and the electrolyte solution was injected into the case. At this time, the electrolyte solution was added to an organic solvent composed of ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) (mixing ratio of EC / DMC / EMC = 3/4/3) to lithium hexafluoro Phosphate (LiPF ₆ ).

The cap assemblies prepared in Preparation Examples 1 and 2 were placed on the upper part of the battery case, respectively, and then clamped to produce a lithium secondary battery.

[Experimental Example 1]

The lithium secondary batteries of Example 1 and Comparative Examples 1 and 2 were fully charged at 0.2 C (Cut Off voltage = 4.35 V) and stored in a chamber at a relative humidity of 90% and a temperature of 60 캜 for 48 hours. Thereafter, it was kept at room temperature for 2 hours.

The capacity of the battery immediately after the full charge and the capacity of the battery after storage at the high temperature and high humidity conditions were respectively measured, and the capacity retention rate was evaluated therefrom. The experiment was carried out four times under the same conditions, and the results are shown in Table 1 below.

Initial capacity (unit) Capacity after storage at high temperature and high humidity (unit) Capacity retention rate (%) Example 1 One 2757 2156 78 2 2784 2241 81 3 2749 2172 79 4 2775 2228 80 Average 80 Comparative Example 1 One 2682 2041 76 2 2758 1999 73 3 2757 2090 76 4 2760 2067 75 Average 75 Comparative Example 2 One 2773 2052 74 2 2747 2115 77 3 2786 2117 76 4 2751 2091 76 Average 76

As a result of the test, the battery of Example 1 in which the water swelling polymer was coated showed a capacity retention rate of about 80% after storage at high temperature and high humidity. In contrast, Comparative Example 1 in which a coating film was not formed showed a capacity retention rate of about 75%. In Comparative Example 2 in which a coating film of a general polymer having no water swellability was formed, the capacity retention ratio was minutely increased to 76% , The capacity retention rate was significantly lower than that of Example 1.

The decrease in the capacity retention rate in Comparative Examples 1 and 2 was due to the fact that the water penetrated into the battery and reacted with the positive electrode, the negative electrode, and the electrolyte to generate various side reactions, thereby reducing the amount of lithium supplied to the battery reaction.

From these results, it can be seen that when the coating film of the water swellable polymer is formed on the gasket as in the present invention, water penetration is more effectively blocked, thereby improving battery performance.

10, 100: secondary battery
20, 200: cans
21, 210:
30, 300: electrode assembly
31, 310: Positive electrode lead
40, 400: laminate
41, 410: Top cap
42, 420: PTC element
43, 430: Safety vans
43a, 430a:
43b, 43c, 430b, 430c:
44, 440: Safety element
50, 500: Gasket
51, 510: Secondary gasket
60, 600: cap assembly
700, 700a, 700b: coating film

Claims (15)

A laminate including a top cap; And
And a gasket surrounding and sealing the outer circumferential surface of the laminate,
Wherein the gasket includes a coating film on a side of a gasket that contacts the laminate,
Wherein the coating film comprises a water swelling polymer having a water swelling degree of 30% or more,
Wherein the water swelling polymer is provided with a polymer that is swellable by moisture.
Claim 1:
Wherein the gasket further comprises a coating film comprising a water swelling polymer on an outer surface of a gasket not in contact with the laminate.
Claim 1:
Wherein the coating film has a water swell degree of 0.5% to 2%.
Claim 1:
Wherein the coating film comprises a hydrogel of a water-swellable polymer.
Claim 1:
Wherein the water swellable polymer has a water swell degree of 60% to 90%.
The method according to claim 1,
Wherein the water swelling polymer is selected from the group consisting of polyhydroxyethylmethyl acrylate, polyethyleneglycol, polyoxyethylene, polyethylene oxide, polyethylene glycol methacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyvinyl alcohol , Polyvinyl pyrrolidone, polyimide, and a mixture of one or more selected from the group consisting of polyacrylates and polyurethanes.
The method according to claim 1,
Wherein the water swelling polymer is contained in an amount of 0.5 wt% to 4 wt% based on the total weight of the cap assembly when the swelling degree of the water swelling polymer is 50%.
The method according to claim 1,
Wherein the coating film has a thickness of 1 占 퐉 to 100 占 퐉.
The method according to claim 1,
Wherein the gasket comprises a polyolefin-based polymer.
A secondary battery comprising a cap assembly according to any one of claims 1 to 9.
The method of claim 10,
Wherein the secondary battery is a circular secondary battery.
A battery module comprising the lithium secondary battery according to claim 11 as a unit cell.
A battery pack comprising the battery module according to claim 12.
14. The method of claim 13,
A battery pack that is used as a power source for mid- to large-sized devices.
15. The method of claim 14,
Wherein the middle- or large-sized device is selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle and a system for power storage.

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