WO2019164371A1 - Gasket for secondary battery and secondary battery comprising same - Google Patents

Abstract

The present invention relates to a gasket for a secondary battery comprising a base resin and a rust preventive, wherein the base resin comprises polybutylene terephthalate and the rust preventive comprises a rust preventing material and a polymer resin, the base resin and the polymer resin being different from each other, and the rust preventing material comprising at least one of the compounds of the following formulas 1-1 and 1-2. [formula 1-1] A₁-R₁ [formula 1-2] A₁-R₂-A₂, wherein R₁ is any one selected from the group consisting of a linear alkyl group of 8 to 20 carbon atoms, a branched alkyl goup of 8 to 20 carbon atoms, an alkenyl group of 8 to 20 carbon atoms, an akynyl group of 8 to 20 carbon atoms, and an aryl group of 8 to 18 carbon atoms, R₂ is any one selected from the group consisting of a linear alkylene group of 8 to 20 carbon atoms, a branched alkylene group of 8 to 20 carbon atoms, an alkenylene group of 8 to 20 carbon atoms, an alkynylenyl group of 8 to 20 carbon atoms, and an arylene group of 8 to 18 carbon atoms, and A₁ and A₂ are each independently any one selected from the group consisting of a carboxyl group, an amino group, a nitro group, a hydroxy group, and a fluorine group.

Description

Gasket for secondary battery and secondary battery comprising same

Citation with Related Applications

This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0022063, filed February 23, 2018, and all content disclosed in the documents of that Korean Patent Application is incorporated as part of this specification.

Technical Field

The present invention relates to a secondary battery gasket and a secondary battery comprising the same.

In general, a secondary battery means a battery that can be charged and discharged, unlike a primary battery that cannot be charged, and is widely used for a power source of an electronic device such as a mobile phone, a notebook computer, a camcorder, or an electric vehicle. In particular, the lithium secondary battery has an operating voltage of 3.6 V, and has a capacity of about three times that of a nickel-cadmium battery or a nickel-hydrogen battery, which is widely used as a power source for electronic equipment, and has a high energy density per unit weight. Is rapidly increasing.

Such lithium secondary batteries mainly use lithium-based oxides and carbon materials as positive electrode active materials and negative electrode active materials, respectively. In addition, the lithium secondary battery may be classified into a square battery, a cylindrical battery, and a pouch type battery.

The lithium ion secondary battery includes an electrode assembly in which an anode, a separator, and an anode are sequentially disposed, and an exterior member that seals and houses the electrode assembly together with the electrolyte solution. In particular, the packaging material has a can formed with an open end and a cap assembly sealingly coupled to the open end of the can.

In general, a gasket is interposed between the can and the cap assembly to seal the battery. As the gasket of the battery, polymer resin layers such as polypropylene have been used. However, there is a problem that rust occurs in a crimping part of a battery, for example, a trimming part in which Fe is exposed in a high temperature and high humidity atmosphere, and there is a need for improvement.

One problem to be solved by the present invention is to minimize the occurrence of rust in the crimping portion of the battery in a high temperature, high humidity atmosphere, and to provide a secondary battery gasket and secondary battery with improved sealing characteristics.

According to an embodiment of the present invention, a base resin and a rust inhibitor, wherein the base resin comprises polybutylene terephthalate, the rust preventive agent comprises a rust-preventing material and a polymer resin, the base resin and the polymer resin In addition, the rust preventing material is provided with a gasket for a secondary battery comprising at least one of the compounds of the following formula 1-1 and formula 1-2.

Equation 1-1

Formula 1-2

R ₁ is selected from the group consisting of a linear alkyl group having 8 to 20 carbon atoms, a branched alkyl group having 8 to 20 carbon atoms, an alkenyl group having 8 to 20 carbon atoms, alkynyl group having 8 to 20 carbon atoms, and an aryl group having 8 to 18 carbon atoms. Which one,

R ₂ is a linear alkylene group having 8 to 20 carbon atoms, a branched alkylene group having 8 to 20 carbon atoms, an alkenylene group having 8 to 20 carbon atoms, an alkenylene group having 8 to 20 carbon atoms, and an arylene group having 8 to 18 carbon atoms. Any one selected from the group consisting of,

A ₁ and A ₂ are each independently any one selected from the group consisting of a carboxyl group, an amino group, a nitro group, a hydroxyl group, and a fluorine group.

According to another embodiment of the present invention, an electrode assembly including an anode and a cathode; A can including a top opening; A cap assembly formed on an upper circumferential surface of the can and coupled to the can by a crimping portion formed by bending a portion of the upper opening inwardly; And a secondary battery gasket, wherein the secondary battery gasket is provided with a secondary battery interposed between the can and the cap assembly.

The gasket for a secondary battery according to an embodiment of the present invention includes a specific anti-rust material, and the anti-rust material is vaporized and adsorbed to an exposed portion of Fe at a crimping portion, particularly at an upper opening of a can, so that Fe is in direct contact with water and oxygen. Can be prevented. Accordingly, it is possible to minimize the occurrence of rust in the crimping portion of the battery in a high temperature, high humidity atmosphere. In addition, the present invention can improve the heat resistance and sealing properties of the gasket using a polybutylene terephthalate (PBT) as the base resin. In addition, the specific rust preventive material is injected together with polybutylene terephthalate having a high injection temperature, wherein the specific rust preventive material does not collapse the structure even at the high injection temperature, so that the rust preventive material of the rust preventive material in the final manufactured gasket Properties can be maintained.

In addition, since the specific rust-preventing material is dispersed in a small size at the level of omstrong and is present in the gasket, the voids generated in the gasket during vaporization are formed to a negligible level. Thus, the gasket of the present invention can be maintained in sealing properties as compared with the case of using conventional antirust materials dispersed in a large size of micro (μm) level and present in the gasket.

1 is a cross-sectional view illustrating one surface of a secondary battery in which a gasket for a secondary battery according to an embodiment of the present invention is introduced.

2 is a cross-sectional view illustrating a secondary battery in which a gasket for a secondary battery is introduced in an embodiment of the present invention.

3 is a cross-sectional view illustrating a secondary battery in which a gasket for a secondary battery according to another embodiment of the present invention is introduced.

Hereinafter, the present invention will be described in more detail to aid in understanding the present invention.

The terms or words used in this specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best describe their invention. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

As used herein, the terms "comprise", "comprise" or "have" are intended to indicate that there is a feature, number, step, component, or combination thereof, that is, one or more other features, It should be understood that it does not exclude in advance the possibility of the presence or addition of numbers, steps, components, or combinations thereof.

A gasket for a secondary battery according to an embodiment of the present invention includes a base resin and a rust preventive agent, the base resin includes a polybutylene terephthalate, the rust preventive agent includes a rust preventive substance and a polymer resin, and the base resin and the The polymer resin is different, and the rust preventive substance includes at least one of the compounds of the following Formulas 1-1 and 1-2.

Equation 1-1

Formula 1-2

R ₁ is selected from the group consisting of a linear alkyl group having 8 to 20 carbon atoms, a branched alkyl group having 8 to 20 carbon atoms, an alkenyl group having 8 to 20 carbon atoms, alkynyl group having 8 to 20 carbon atoms, and an aryl group having 8 to 18 carbon atoms. Which one,

R ₂ is a linear alkylene group having 8 to 20 carbon atoms, a branched alkylene group having 8 to 20 carbon atoms, an alkenylene group having 8 to 20 carbon atoms, an alkenylene group having 8 to 20 carbon atoms, and an arylene group having 8 to 18 carbon atoms. Any one selected from the group consisting of,

A ₁ and A ₂ are each independently any one selected from the group consisting of a carboxyl group, an amino group, a nitro group, a hydroxyl group, and a fluorine group.

The rust inhibitor may be a vaporizable rust inhibitor (VCI; Volatile Corrosion Inbibitor). The rust preventive agent may be vaporized and adsorbed to a trimming part in which Fe is exposed at a crimping part, particularly at the top opening of the can, thereby preventing Fe from directly contacting water and oxygen.

The rust inhibitor may be present dispersed in a molecular unit in the base resin of the gasket.

The rust preventive material may include at least one of the compounds of Formulas 1-1 and 1-2.

Equation 1-1

Formula 1-2

R ₁ is selected from the group consisting of a linear alkyl group having 8 to 20 carbon atoms, a branched alkyl group having 8 to 20 carbon atoms, an alkenyl group having 8 to 20 carbon atoms, alkynyl group having 8 to 20 carbon atoms, and an aryl group having 8 to 18 carbon atoms. Which one,

R ₂ is a linear alkylene group having 8 to 20 carbon atoms, a branched alkylene group having 8 to 20 carbon atoms, an alkenylene group having 8 to 20 carbon atoms, an alkenylene group having 8 to 20 carbon atoms, and an arylene group having 8 to 18 carbon atoms. Any one selected from the group consisting of,

A ₁ and A ₂ are each independently any one selected from the group consisting of a carboxyl group, an amino group, a nitro group, a hydroxyl group, and a fluorine group.

When using the compounds according to Equations 1-1 and 1-2 above, A ₁ and / or A ₂ are electrically and / or chemically adsorbed to the crimped portion, in particular the Fe exposed portion at the top opening of the can, R ₁ and / or R ₂ may form a hydrophobic layer to prevent Fe from coming in direct contact with water and oxygen. Through this, it is possible to minimize the occurrence of rust in the crimping portion of the battery even under high temperature, high humidity conditions.

On the other hand, the gasket for a secondary battery of the present invention is manufactured through the method of injecting the base resin and the rust preventive agent containing polybutylene terephthalate at high temperature. The injection temperature of the polybutylene terephthalate is a high temperature of 280 ℃ level, the anti-rust material used in the present invention does not collapse the structure even at the injection temperature. Therefore, the antirust effect by the antirust material can be maintained even in the finally manufactured gasket.

More specifically, the rust preventive material may include at least one of the following Formulas 1-3 and 1-4.

[Equation 1-3]

[Equation 1-4]

In Equation 1-3 and Equation 1-4,

A ₁ is the same as A ₁ of Formulas 1-1 and 1-2,

P is 4 to 10,

Q may be 3 to 6.

The rust preventive materials of Equation 1-3 and Equation 1-4 may exhibit the rust preventive effect described above, and do not deform the structure at the injection temperature of the base resin including polybutylene terephthalate. In addition, it is possible to minimize the deterioration of the sealing properties of the gasket for the following reasons.

Conventionally, materials such as NaNO ₂ and NaNO ₃ , which are used as rust preventive materials, are dispersed and present in a large unit at a micro (μm) level in the resin, so that when the materials are vaporized, large voids are generated in the resin constituting the gasket. . As a result, external moisture and oxygen can penetrate into the battery through the pores, and thus the sealing property of the gasket may be degraded, thereby degrading battery performance. On the other hand, since the rust preventive materials of Equation 1-3 and Equation 1-4 are dispersed in a small size at the Omstrong level and present in the gasket, the voids generated in the gasket during vaporization are formed to a negligible level. . Therefore, the fall of the sealing characteristic which a gasket has can be minimized.

More specifically, the rust preventing material may include at least one selected from the group consisting of decanoic acid, lauric acid, and myristic acid. When using the rust-preventing material, the above-described rust-preventing effect can be exhibited, and the structure is not deformed at the injection temperature of the base resin including polybutylene terephthalate. In addition, the deterioration of the sealing property of the gasket can be minimized.

The polymer resin may be mixed with the rust preventive material to serve to disperse the rust preventive material in the base resin. The polymer resin may be different from the base resin for smooth dispersion of the rust preventing material in the base resin.

The polymer resin is polyethylene (PE); And ethylene derived units, propylene derived units, butylene terephthalate derived units, ethylene terephthalate derived units, and methyl acrylate derived units. Copolymers comprising two or more derived units; It may include at least one of. Specifically, the above materials may be mixed and used. The polymer resin is preferable in that it is easy to mix with the rust-preventing material and easy to mix with polybutylene terephthalate. In addition, the antirust property of the gasket can be further improved. Specifically, the polymer resin may be a copolymer including an ethylene-derived unit and a methyl acrylate-derived unit in consideration of a manufacturing process and mixing with the base resin.

The weight ratio of the polymer resin and the rust preventing material may be 99: 1 to 80:20, specifically 99: 1 to 85:15, and more specifically 99: 1 to 90:10. If the above range is satisfied, the rust preventive effect may be more effective.

The rust preventive agent may be in the form of pellets. Specifically, the rust preventive agent may be in the form of pellets formed through the pelletization process after mixing the polymer resin and the rust preventive material. Through this, the rust preventive agent can be smoothly dispersed in the base resin. If only the rust preventing material is mixed with the base resin in a non-pellet form (i.e., without a polymer resin), the rust preventing function is sharply degraded because the rust preventing material is not smoothly dispersed in the base resin.

The base resin may include polybutylene terephthalate (PBT), and specifically, may be polybutylene terephthalate. Since the polybutylene terephthalate has high heat resistance and low oxygen and moisture permeability, it is more preferable as the base resin of the gasket. Specifically, when polypropylene having a low melting point of about 160 ° C. is used as the base resin, the polypropylene melts when a short circuit between the positive electrode and the negative electrode occurs, thereby causing a problem of deterioration of battery stability. On the other hand, in the case of polybutylene terephthalate has a high melting point of about 230 ℃ level, the gasket is maintained to ensure the stability of the battery.

Furthermore, in the case where the base resin is polybutylene terephthalate, when the antirust material included in the anticorrosive for the gasket is used, there are advantages as follows. In the case of conventionally used rust-preventing materials such as NaNO ₂ and NaNO ₃ , the polybutylene terephthalate is degraded by weakening the C═O bonds contained in the polybutylene terephthalate, thereby deteriorating the physical properties of the gasket. Specifically, the ductility of the polybutylene terephthalate is lowered, and cracks are likely to occur in the gasket due to external force. On the other hand, the rust preventive material of the present invention can minimize the weakening of the C═O bonds contained in the polybutylene terephthalate or have no influence on the bonds, so that the physical properties of the gasket can be maintained. In addition, the polybutylene terephthalate has a high injection temperature of 280 ℃, the anti-rust material of the present invention injected with the polybutylene terephthalate does not collapse the structure even at the high temperature, so that the final gasket Antirust properties can be maintained.

The weight ratio of the polybutylene terephthalate and the rust preventive agent may be 98: 2 to 85:15, specifically 98: 2 to 90:10, and more specifically 93: 7 to 90:10. When the above range is satisfied, the above-described antirust effect can be further improved.

According to another embodiment of the present invention, a secondary battery includes an electrode assembly including a positive electrode and a negative electrode; A can including a top opening; A cap assembly formed on an upper circumferential surface of the can and coupled to the can by a crimping portion formed by bending a portion of the upper opening inwardly; A secondary battery gasket may be included, and the secondary battery gasket may be interposed between the can and the cap assembly. Here, since the gasket for secondary batteries is the same as the gasket for secondary batteries of the above-mentioned embodiment, description is abbreviate | omitted.

The secondary battery may have a cylindrical shape, a square shape, or the like, and specifically, may have a cylindrical shape. When the secondary battery is cylindrical, the top opening of the can may also be circular.

1 and 2, the secondary battery 100 includes a can 20 for accommodating the electrode assembly 10 together with an electrolyte, a cap assembly 30 sealingly coupled to an open end of the can 20, A gasket 40 interposed between the cylindrical can 20 and the cap assembly 30. The gasket 40 is the same as the gasket for the secondary battery of the above-described embodiment.

The material of the can 20 is not particularly limited, and may be formed of at least one of stainless steel, steel, aluminum, or an equivalent thereof. The can 20 uses a metal component because it has to be conductive, and this metal component may be vulnerable to corrosion due to moisture contact from the outside. In this regard, the can 20 may include a layer made of Fe and a layer made of Ni which prevents the layer made of Fe from corrosion.

The can 20 may be cylindrical, rectangular, or the like, and specifically, may be cylindrical. The open end of the can 20 may include a trimming portion 21a, and the trimming portion 21a may expose the Fe component of the can. Specifically, in the final product state, the trimming portion 21a can be seen to be included in the crimping portion 21.

The cap assembly 30 may include a top cap that seals the open end of the can 20, and a safety vent 36. One surface of the safety vent 36 may be in contact with all of the side surface, the upper surface and the lower surface of the top cap, and the other surface may be bent and disposed to contact the inner surface of the gasket 40. The safety vent 36 may be electrically connected to the electrode assembly 10. When the battery having the cap assembly 30 is used as a power source of a power tool such as a power drill, the battery may provide a high output instantaneously and may be stable against external physical shocks such as vibration and dropping.

In particular, the cap assembly 30 having a shape in which the safety vent 36 is bent to surround the top cap may have a contact surface between the safety vent 36 and the top cap to form at least one connection part. Is formed. The term "welding" used in the present invention is used as a concept that includes not only welding in a literal sense such as laser welding, ultrasonic welding, resistance welding, but also a fastening method such as soldering. Welding may be performed in the process of assembling the cap assembly 30 itself, or may be performed even when the cap assembly 30 is installed in the can 20.

The safety vent 36 serves to cut off a current or exhaust gas when the pressure inside the battery rises, and is preferably made of metal. The thickness of the safety vent 36 may vary depending on the material, structure, and the like, and the thickness of the safety vent 36 is not particularly limited as long as the safety vent 36 may burst while generating a high pressure inside the battery, and may be, for example, 0.2 to 0.6 mm. .

The thickness of the top cap portion in contact with the safety vent 36 is not particularly limited as long as it can protect various components of the cap assembly 30 from pressure applied from the outside, for example, 0.3 To 0.5 mm. If the thickness of the top cap is too thin, it is difficult to exert mechanical rigidity. On the contrary, if the thickness of the top cap is too thick, the capacity of the battery may be reduced by increasing the size and weight.

The gasket 40 may be formed in a cylindrical shape, each end of which is open at both ends as a whole, may vary depending on the shape of the top opening of the can, specifically, may be a cylindrical shape. One side end facing the inner surface of the can 20 is preferably a structure bent at an angle, specifically at a right angle toward the center so as to be placed in the opening of the can 20, that is, the crimping portion 21. The other end of the gasket 40 is first straight and is oriented in the axial direction of the gasket 40, and is bent at an angle toward the center during the pressing process with the can 20 so that the inner and outer circumferential surfaces of the gasket 40 are cap assemblies ( The top cap of 30 and the inner side of the can 20 are folded in close contact.

The crimping portion 21 is formed at the top of the can so that the cap assembly 30 can be mounted at the open end of the can. More specifically, the crimping portion 21 forms an indentation inward by beading the upper end of the can 20, mounts the gasket 40 at the open end, and top cap, PTC element, safety vent 36. It is formed by inserting the outer circumferential surface of and then bending the upper end of the can inward. As a result, the gasket 40 positioned on the inner side of the crimping portion 21 is enclosed, and the cap assembly 30 is mounted by performing a crimping and pressing process.

The crimping portion 21 has a structure in which an end portion is bent inward so that the cap assembly 30 can be stably mounted on an open upper end of the can 20 in a state where the gasket 40 is interposed therebetween. The side wall of the crimping portion 21 is formed perpendicular to the side of the battery.

The electrode assembly 10 may include a positive electrode and a negative electrode. Referring to FIG. 2, the electrode assembly 10 is interposed between two electrode plates 11 having different polarities and having a wide plate shape in a roll form, and the electrode plates 11 to mutually insulate the electrode plates 11. Or a separator 12 disposed on the left side or the right side of any one electrode plate 11. In this case, the electrode plates 11 spaced apart from each other by the separator 12 may be a cathode and an anode. The electrode assembly 10 is preferably a structure wound in a so-called 'Jelly Roll' shape. Of course, a positive electrode plate and a negative electrode plate of a predetermined standard may be stacked in the separator 12.

An electrode assembly 10 and an electrolyte (not shown) are accommodated in the inner space of the can 20. The electrolyte is to move lithium ions generated by the electrochemical reaction of the electrode plate 11 during charging and discharging of the secondary battery 100. The electrolyte may be a polymer using a non-aqueous organic electrolyte or a polymer electrolyte which is a mixture of lithium salts and high purity organic solvents, but the type of electrolyte is not a problem.

Meanwhile, a center pin (not shown) may be inserted into the center of the can 20 to prevent the electrode assembly 10 wound in a jelly roll form from being loosened and to serve as a gas passageway inside the secondary battery 100. It may be. An upper portion of the can 20, that is, an upper portion of the upper portion of the electrode assembly 10 may be provided with a beading portion 24 which is bent from outside to the inside to prevent the up and down flow of the electrode assembly 10.

Cylindrical battery 100 according to an embodiment of the present invention may further include an auxiliary gasket 42. The auxiliary gasket 42 is configured to surround the outer circumferential surface of the current blocking device 38 as a gasket for the current blocking device 38. In particular, the auxiliary gasket 42 contacts the upper and side portions at the outer circumferential surface of the current blocking element 38 to support the upper and side portions of the current blocking element 38. The auxiliary gasket 42 serves to electrically insulate the current blocking device 38 and the safety vent 36 from each other, except for a portion where the protruding portion of the safety vent 36 contacts with the current blocking element 38. Do it.

3 illustrates a battery 100 according to another embodiment of the present invention. The same components as those described in FIG. 2 are the same members having the same functions. Referring to FIG. 3, the cap assembly 30 may include a top cap disposed to seal the open end of the can 20 and contact the protrusion of the gasket 40, and a PTC element disposed to contact the top cap. Positive temperature coefficient 34 and one surface may include a safety vent 36 disposed in contact with the PTC element 34 and with a portion of the other surface in contact with the gasket 40.

The PTC element 34 serves to block the current by greatly increasing the battery resistance when the temperature inside the battery increases, and the thickness of the PTC element 34 may also vary depending on the material and structure, for example, 0.2 mm. To 0.4 mm. When the thickness of the PTC element 34 is greater than 0.4 mm, the internal resistance may increase, and the size of the battery may be increased to reduce the capacity of the battery compared to the same standard. On the contrary, when the thickness of the PTC element 34 is thinner than 0.2 mm, it is difficult to exert a desired current interruption effect at a high temperature and can be destroyed even by a weak external impact. Accordingly, the thickness of the PTC element 34 may be appropriately determined within the above thickness range in consideration of these points in combination.

The thickness of the top cap portion in contact with the PTC element 34 is not particularly limited as long as it can protect various components of the cap assembly 30 from the pressure applied from the outside, for example, 0.3 to 0.5 May be mm. If the thickness of the top cap is too thin, it is difficult to exert mechanical rigidity. On the contrary, if the thickness of the top cap is too thick, the capacity of the battery may be reduced by increasing the size and weight.

The secondary battery including the top cap, the PTC element 34, and the cap assembly 30 having the safety vent may be used as a power source for a mobile phone or a notebook, which stably provides a constant output.

The present invention can provide a battery pack comprising a plurality of lithium secondary batteries prepared by the above embodiment by electrically connecting, the battery pack is a power tool (Electric Tool, Electric Vehicle, EV), hybrid Medium to large in one or more devices selected from the group consisting of electric vehicles, electric trucks, electric commercial vehicles, or power storage systems, including electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). The battery pack may be used as a device power source.

Hereinafter, the present invention is further described through Examples and Comparative Examples, but the following Examples are provided to illustrate the present invention, but the scope of the present invention is not limited thereto.

Example 1 Fabrication of Cells

(1) manufacture of gaskets

A copolymer comprising an ethylene-derived unit and a methyl acrylate-derived unit and lauric acid were mixed at 100 ° C. in a weight ratio of 95: 5, and then pelletized to prepare a rust inhibitor in the form of a pellet. 240 g of the rust preventive agent and 3,000 g of polybutylene terephthalate were mixed and then injected at a temperature of 280 ° C. to prepare a gasket.

(2) production of batteries

The can consisted of an inner layer of Fe and a Ni layer disposed on both sides of the inner layer. After placing a gasket in the top opening of the can, the cap assembly was placed in contact with the inner circumferential surface of the gasket, and then a crimping portion was formed. Through this, a battery including the gasket was manufactured.

Example 2: Preparation of Cells

(1) manufacture of gaskets

A copolymer comprising an ethylene-derived unit and a methyl acrylate-derived unit and lauric acid were mixed at 100 ° C. in a weight ratio of 95: 5, and then pelletized to prepare a rust inhibitor in the form of a pellet. 150 g of the rust inhibitor and 3,000 g of polybutylene terephthalate were mixed, and then injected at a temperature of 280 ° C. to prepare a gasket.

(2) production of batteries

The can consisted of an inner layer of Fe and a Ni layer disposed on both sides of the inner layer. After placing a gasket in the top opening of the can, the cap assembly was placed in contact with the inner circumferential surface of the gasket, and then a crimping portion was formed. Through this, a battery including the gasket was manufactured.

Example 3: Fabrication of Batteries

(1) manufacture of gaskets

A copolymer comprising ethylene derived units and methyl acrylate derived units and decanoic acid were mixed at 100 ° C. in a weight ratio of 95: 5, and then pelletized to prepare a rust preventive agent in pellet form. 240 g of the rust preventive agent and 3,000 g of polybutylene terephthalate were mixed and then injected at a temperature of 280 ° C. to prepare a gasket.

(2) production of batteries

The can consisted of an inner layer of Fe and a Ni layer disposed on both sides of the inner layer. After placing a gasket in the top opening of the can, the cap assembly was placed in contact with the inner circumferential surface of the gasket, and then a crimping portion was formed. Through this, a battery including the gasket was manufactured.

Comparative Example 1: Preparation of Battery

(1) manufacture of gaskets

Polybutylene terephthalate was injected at 280 ° C to prepare a gasket.

(2) production of batteries

The can consisted of an inner layer of Fe and a Ni layer disposed on both sides of the inner layer. After placing a gasket in the top opening of the can, the cap assembly was placed in contact with the inner circumferential surface of the gasket, and then a crimping portion was formed. Through this, a battery including the gasket was manufactured.

Comparative Example 2: Preparation of Battery

(1) manufacture of gaskets

Polyethylene and NaNO ₂ were mixed at 140 ° C. in a weight ratio of 70:30, and then pelletized to prepare a rust preventive agent in pellet form. 240 g of the rust preventive agent and 3,000 g of polybutylene terephthalate were mixed and then injected at a temperature of 280 ° C. to prepare a gasket.

(2) production of batteries

The can consisted of an inner layer of Fe and a Ni layer disposed on both sides of the inner layer. After placing a gasket in the top opening of the can, the cap assembly was placed in contact with the inner circumferential surface of the gasket, and then a crimping portion was formed. Through this, a battery including the gasket was manufactured.

Comparative Example 3: Preparation of Battery

(1) manufacture of gaskets

A copolymer comprising an ethylene-derived unit and a methyl acrylate-derived unit and lauric acid were mixed at 100 ° C. in a weight ratio of 95: 5, and then pelletized to prepare a rust inhibitor in the form of a pellet. 240 g of the rust inhibitor and 3,000 g of poly-tetrafluoroethylene (PFA) were mixed and then injected at a temperature of 380 ° C. to prepare a gasket.

(2) production of batteries

The can consisted of an inner layer of Fe and a Ni layer disposed on both sides of the inner layer. After placing a gasket in the top opening of the can, the cap assembly was placed in contact with the inner circumferential surface of the gasket, and then a crimping portion was formed. Through this, a battery including the gasket was manufactured.

Comparative Example 4: Preparation of Battery

(1) manufacture of gaskets

12 g of lauric acid and 3,228 g of polybutylene terephthalate were mixed and then injected at a temperature of 280 ° C to prepare a gasket.

(2) production of batteries

The can consisted of an inner layer of Fe and a Ni layer disposed on both sides of the inner layer. After placing a gasket in the top opening of the can, the cap assembly was placed in contact with the inner circumferential surface of the gasket, and then a crimping portion was formed. Through this, a battery including the gasket was manufactured.

Experimental Example 1: Evaluation of Antirust Function

Each of the batteries of Examples 1 to 3 and Comparative Examples 1 to 4 were stored for 2 weeks in an environment of 65 ° C. and 90% humidity, and then the antirust properties were evaluated and shown in Table 1 below.

Specifically, the percentage of the area where corrosion occurred based on the area of the trimming part of the upper outer circumferential surface of the can is expressed in%. Corrosion occurred at 3 points over 50%, 2 points over 10% and below 50%, 1 point below 10%, and 0 points without corrosion. After scoring the 30 cells in this way, the average value of the scores were converted to 10 out of 10 points (mean value x (10/3)) to evaluate the antirust function by the final score derived. On the other hand, the extent to which corrosion occurred was visually confirmed with a microscope.

	Antirust function evaluation score
Example 1	0.4
Example 2	1.1
Example 3	0.5
Comparative Example 1	9.7
Comparative Example 2	1.9
Comparative Example 3	10.0
Comparative Example 4	4.9

Referring to Table 1, in the case of Examples 1 to 3 using the gasket rust inhibitor of the present invention, compared to Comparative Example 1 using the rust preventive agent and Comparative Example 2 using the conventional rust inhibitor including NaNO ₂ You can see that it is much higher.

On the other hand, in the case of Comparative Example 3 using PFA other than polybutylene terephthalate as the base resin, since the melting point of the base resin is high, most of the rust preventive agents contained in the base resin are thermally decomposed, and thus it can be seen that the rust preventing function is lowered. In addition, when the rust preventive material is composed only of the rust preventive agent without the polymer resin, the rust preventive function may be deteriorated since the rust preventive agent may not be uniformly dispersed in the gasket due to the difference in specific gravity of the base resin and the rust preventive agent.

Experimental Example 2: Evaluation of Seal Function

Each of the batteries of Example 1 and Comparative Examples 1 to 4 was stored at 72 ° C. at SOC 100% for 40 days. The cell weights before and after storage were evaluated and shown in Table 2 below. The weight change rate of Table 2 calculated the following formula.

Percent Change in Weight = [(Weight before Storage-Battery Weight after Storage) / Weight before Storage] × 100

	Battery weight before storage (g)	Battery weight after storage (g)	% Change in weight
Example 1	48.03	48.02	0.0208
Comparative Example 1	47.90	47.89	0.0209
Comparative Example 2	47.97	47.27	1.4592
Comparative Example 3	47.94	47.92	0.0417
Comparative Example 4	47.99	47.98	0.0208

Referring to Table 2, in the case of Example 1, despite the evaporation of the rust preventive material, since the voids in the gasket is not large, it can be confirmed that the sealing function can be effectively maintained as in Comparative Example 1 not containing the rust preventive material On the other hand, in the case of Comparative Example 2 using NaNO ₂ as a rust-preventing material, it can be seen that a large number of large pores exist in the gasket, and the sealing function is greatly reduced.

Claims (6)

1. Including base resins and rust inhibitors,

   The base resin comprises polybutylene terephthalate,

   The rust preventive agent includes a rust preventive material and a polymer resin,

   The base resin and the polymer resin is different,

   The anti-corrosive material is a gasket for a secondary battery comprising at least one of the compounds of Formulas 1-1 and 1-2:

   Equation 1-1

   

   Formula 1-2

   

   R ₁ is selected from the group consisting of a linear alkyl group having 8 to 20 carbon atoms, a branched alkyl group having 8 to 20 carbon atoms, an alkenyl group having 8 to 20 carbon atoms, alkynyl group having 8 to 20 carbon atoms, and an aryl group having 8 to 18 carbon atoms. Which one,

   R ₂ is a linear alkylene group having 8 to 20 carbon atoms, a branched alkylene group having 8 to 20 carbon atoms, an alkenylene group having 8 to 20 carbon atoms, an alkenylene group having 8 to 20 carbon atoms, and an arylene group having 8 to 18 carbon atoms. Any one selected from the group consisting of,

   A ₁ and A ₂ are each independently any one selected from the group consisting of a carboxyl group, an amino group, a nitro group, a hydroxyl group, and a fluorine group.
2. The method according to claim 1,

   The anti-corrosive material may include a gasket for a secondary battery including at least one of Equation 1-3 and Equation 1-4;

   [Equation 1-3]

   

   [Equation 1-4]

   

   In Equation 1-3 and Equation 1-4,

   P is 4 to 10,

   Q is 3 to 6;
3. The method according to claim 2,

   The rust preventing material is a gasket for a secondary battery including at least one selected from the group consisting of decanoic acid, lauric acid, and myristic acid.
4. The method according to claim 1,

   The polymer resin is polyethylene; And a copolymer comprising two or more derived units selected from the group consisting of ethylene derived units, propylene derived units, butylene terephthalate derived units, ethylene terephthalate derived units and methyl acrylate derived units; Gasket for a secondary battery comprising at least any one of.
5. The method according to claim 1,

   The weight ratio of the polybutylene terephthalate and the rust preventive agent is a gasket for a secondary battery of 98: 2 to 85:15.
6. An electrode assembly comprising an anode and a cathode;

   A can including a top opening;

   A cap assembly formed on an upper circumferential surface of the can and coupled to the can by a crimping portion formed by bending a portion of the upper opening inwardly; And

   Claims 1 to 5, including a gasket for a secondary battery,

   The secondary battery gasket is interposed between the can and the cap assembly.

Images