WO2018147662A1 - Lead sealant film, manufacturing method therefor, and secondary battery using same - Google Patents

Abstract

The present invention relates to: a lead sealant film, which is resistant to modification while having a high adhesive property, for sealing the space between an electrode lead and a case; a manufacturing method therefor; and a secondary battery using the same. According to the present invention, the lead sealant film comprises: a first layer comprising an acid-modified copolymer, an elastomer, and a low-density polyolefin; a second layer attached on the first layer, and comprising an acid-modified copolymer, an elastomer, and a low-density polyolefin; and a third layer attached on the second layer, and comprising an acid-modified copolymer, an elastomer, and a vinyl-based copolymer.

Description

Lead Sealant Film, Manufacturing Method thereof and Secondary Battery Using the Same

The present invention relates to a secondary battery, and more particularly, to a lead sealant film resistant to denaturation while being highly adhesive for sealing between an electrode lead and a case, a manufacturing method thereof, and a secondary battery using the same.

In recent years, many portable electronic devices, such as a compact lightweight camera integrated video tape recorder (VTR), a mobile telephone, and a portable computer, have emerged. As a portable power source for these electronic devices, research and development are being actively conducted on batteries, particularly secondary batteries, and especially nonaqueous electrolyte secondary batteries (so-called lithium ion batteries).

Representatively, there is a high demand for rectangular secondary batteries and pouch secondary batteries, which can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and lithium ion batteries with high energy density, discharge voltage, and output stability in terms of materials. There is a high demand for lithium secondary batteries such as lithium ion polymer batteries.

Lithium secondary batteries have been researched in various types of batteries for encapsulating battery elements using a plastic film or a so-called laminate film in which a plastic film and a metal are bonded in order to take advantage of thin and lightweight.

Meanwhile, the pouch-type lithium secondary battery includes an electrode assembly, electrode tabs extending from the electrode assembly, electrode leads welded to the electrode tabs, and a case accommodating the electrode assembly.

Here, the electrode lead and the case are integrated by thermal fusion with a film interposed therebetween. At this time, if a relatively high heat or pressure is applied in the heat fusion process, the film is damaged and the electrode leads are exposed.

As a result, since the case and the electrode lead are brought into contact with each other, a short circuit occurs, so that there is a problem that the safety is greatly reduced and the life of the battery is shortened.

In addition, the pouch-type lithium secondary battery may have a problem in that the internal electrolyte leaks due to the decrease in adhesion between the film and the case or the film and the electrode lead due to continuous charge and discharge operations and external forces such as vibration and dropping.

On the other hand, Japanese Patent Application Laid-Open No. 2006-0128096 is a lead wire for a nonaqueous electrolyte battery in which a positive electrode, a negative electrode, and a separator are stored in a battery case in a laminated film form. The composite coating layer is formed by application of a treatment liquid containing a resin component and a metal salt, and an insulator that is thermally fused to the battery case is formed on the outside of the composite coating layer. Disclosed is a nonaqueous electrolyte battery lead wire that can prevent moisture infiltration and improve adhesion.

In the disclosed nonaqueous electrolyte battery lead wire, a step of applying a compounding ratio of a resin component and a metal salt component to the surface of the electrode lead is added, and thus, the manufacturing process of the electrode lead has a complicated problem.

In addition, Japanese Patent Application Laid-Open No. 2007-0005101 is a lead wire for a nonaqueous electrolyte battery in which an insulator is formed on a surface of a conductor, wherein the insulator has an adhesive layer adhered to the conductor and a crosslinked layer laminated on the opposite layer of the conductor based on the adhesive layer. The resin layer is formed, and the crosslinked resin layer is formed with a plurality of grooves or holes filled with the same material as the adhesive layer, so that the lead wire can improve the electrical insulation and the sealing property of the heat-sealed portion located around the electrode lead. Is starting.

However, the disclosed nonaqueous electrolyte battery lead has a problem in that a cumbersome manufacturing process for filling the same material as the adhesive layer is formed by forming a plurality of grooves or holes in the crosslinked resin layer formed on the adhesive layer.

Accordingly, an object of the present invention is to provide a lead sealant film having a high adhesiveness for sealing between an electrode lead and a case, and a method of manufacturing the same, and a secondary battery using the same, in a simple manufacturing process.

The lead sealant film according to the present invention comprises a first layer comprising an acid-modified copolymer, an elastomer and a low density polyolefin, a second layer bonded on the first layer, and comprising a acid-modified copolymer, an elastomer and a low density polyolefin, and And a third layer bonded on the second layer, the third layer including an acid-modified copolymer, an elastomer and a vinyl copolymer.

In the lead sealant film according to the present invention, when the melting points of the first layer, the second layer, and the third layer are M1, M2, and M3, M2> M3> M1 is satisfied.

In the lead sealant film according to the present invention, the M2 is characterized in that 150 ~ 170 ℃.

In the lead sealant film according to the present invention, the difference between the M1 and the M2 is 15 to 20 ℃, the difference between the M2 and M3 is characterized in that 15 to 20 ℃.

In the lead sealant film according to the present invention, the melt index (MI) of the first layer is 1 to 3, the melt index (MI) of the second layer is 2 to 4, and the melt index (MI) of the third layer is 4 It is characterized in that to 7 to.

In the lead sealant film according to the present invention, the acid-modified copolymer is at least one of maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene, carboxylic acid-modified polypropylene, carboxylic acid-modified polyethylene, acrylic-modified polypropylene, and acrylic-modified polyethylene. It is characterized by including any one.

In the lead sealant film according to the present invention, the elastomer includes an olefinic rubber or an ethylene-based elastomer, and the ethylene-based elastomer includes at least one of ethylene-propylene rubber (EPDM) and ethylene propylene copolymer (EPR). Characterized in that.

In the lead sealant film according to the present invention, the low density polyolefin is characterized in that it comprises at least one of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE).

In the lead sealant film according to the present invention, the content of polypropylene or polyethylene is 100 parts by weight based on 100 parts by weight of the acid-modified copolymer of each of the first layer, the second layer, and the third layer. The second layer is 20 parts by weight or more, and the third layer is 10 parts by weight or more.

In the lead sealant film according to the present invention, the first layer is characterized in that the ratio of the acid-modified copolymer to 20 parts by weight of 20% or more.

In the lead sealant film according to the present invention, the second layer further includes a crosslinking agent, and the crosslinking agent is trimetholpropane methacrylate, pentaerythritol triacrylate, etched recall dimethacrylate, triallyl cyanurate It is characterized in that at least one selected from the group consisting of a rate and triaryl isocyanurate.

In the lead sealant film according to the present invention, the second layer further includes a phenol-based antioxidant, and the phenolic antioxidant includes 0.1 to 0.4 parts by weight based on 100 parts by weight of the compound included in the second layer. It is characterized by.

In the lead sealant film according to the present invention, the first layer, the second layer, and the third layer include 10 to 200 parts by weight of the elastomer and 10 to 200 parts by weight of the low density polyolefin based on 100 parts by weight of the acid-modified copolymer. It is done.

In the lead sealant film according to the present invention, when the lead sealant film is used for the cathode, the thickness of the first layer is 20 to 25 µm, the thickness of the second layer is 30 to 40 µm, and the thickness of the third layer is It is 50 to 60㎛, characterized in that the total thickness of the first layer, the second layer and the third layer is 100 to 125㎛.

In the lead sealant film according to the present invention, when the lead sealant film is used for the anode, the thickness of the first layer is 20 to 25 µm, the thickness of the second layer is 30 to 40 µm, and the thickness of the third layer is It is 100 to 110㎛, characterized in that the total thickness of the first layer, the second layer and the third layer is 150 to 160㎛.

In the lead sealant film according to the present invention, the first layer, the second layer, and the third layer further include a grafting agent.

In the lead sealant film according to the present invention, the first layer and the second layer may further include a heat resistant reinforcing additive.

In the lead sealant film according to the present invention, the third layer further comprises a metal adhesion enhancer.

In the lead sealant film according to the present invention, the yield strength is 15 to 40 N / mm ² , the tensile strength is 30 to 60 N / mm ² , and the elongation is 500 to 1000%.

In the lead sealant film according to the present invention, the MD / TD of the elongation is 0.9 to 1.1.

In the lead sealant film according to the present invention, the heat of fusion (ΔH) is 6 to 20 (J / g).

In the lead sealant film according to the present invention, the adhesive force is 15 to 35 N / cm.

A secondary battery according to the present invention includes an electrode assembly including a plurality of electrode tabs, a plurality of electrode leads connected to the plurality of electrode tabs, and exposed to the outside, and a lead sealant attached to at least one side of each of the plurality of electrode leads. And a case accommodating the electrode assembly with a portion of the plurality of electrode leads exposed to the outside, wherein the lead sealant film is bonded between the electrode lead and the case, and includes an acid-modified copolymer, an elastomer, A first layer comprising a low density polyolefin, bonded to the first layer, a second layer comprising an acid-modified copolymer, an elastomer and a low density polyolefin and bonded to the second layer, an acid-modified copolymer, an elastomer and And a third layer comprising a vinyl copolymer.

The method for producing a lead sealant film according to the present invention comprises a first compound comprising an acid-modified copolymer, an elastomer and a low density polyolefin, an acid-modified copolymer, a second compound comprising an elastomer and a low density polyolefin, and an acid-modified copolymer, an elastomer and Preparing a third compound comprising a vinyl copolymer, a first layer comprising the first compound by co-extruding the first compound, the second compound, and the third compound, and having the second compound Preparing a lead sealant film comprising a second layer and a third layer including the third compound.

In the method for producing a lead sealant film according to the present invention, in the preparing of the compound, a crosslinking agent is added to the second compound.

In the method of manufacturing a lead sealant film according to the present invention, after the manufacturing of the lead sealant film, the method may further include irradiating an electron beam to the lead sealant film.

In the method of manufacturing a lead sealant film according to the present invention, the step of irradiating the electron beam is characterized in that the second layer is selectively crosslinked.

In the method of manufacturing a lead sealant film according to the present invention, after the step of irradiating the electron beam, further comprising the step of laminating the lead sealant film irradiated with the electron beam through a thermal lamination process.

In the method for producing a lead sealant film according to the present invention, in the preparing of the compound, an inorganic filler is added to the second compound.

Lead sealant film according to the present invention by controlling the melting point of each layer by controlling the content of polyethylene or polypropylene contained in the acid-modified copolymer included in the first layer, the second layer and the third layer, a separate adhesive layer It is possible to provide a lead sealant film that is high in adhesion and resistant to denaturation without forming.

The lead sealant film according to the present invention is resistant to denaturation while maintaining a high adhesive strength without forming a separate adhesive layer by adjusting the melting point of each layer through an acid-modified copolymer included in the first layer, the second layer, and the third layer. A lead sealant film can be provided.

In addition, in the lead sealant film according to the present invention, by adding a crosslinking agent to the second compound included in the second layer and selectively crosslinking only the second layer through electron beam irradiation, the adhesive force between the first layer and the second layer can be improved. .

In addition, the lead sealant film according to the present invention can increase the adhesive strength with the electrode lead by giving a polarity to the first layer in direct contact with the electrode lead by setting the content of the acid-modified copolymer of the first layer to 20% or more. have.

In addition, the lead sealant film according to the present invention may ensure strong tensile properties while preventing oxidation of the lead sealant film by including 0.1 to 0.4 parts by weight of the spentol-based antioxidant based on 100 parts by weight of the second compound in the second layer. .

1 is a view showing a secondary battery according to the present invention.

FIG. 2 is a view illustrating an assembled state of an electrode lead, a lead sealant film, and a case in an assembled state of the secondary battery of FIG. 1.

3 is a view showing a lead sealant film according to the present invention.

4 is a flowchart illustrating a method of manufacturing a lead sealant film according to the present invention.

In the following description, only parts necessary for understanding the embodiments of the present invention will be described, it should be noted that the description of other parts will be omitted so as not to distract from the gist of the present invention.

The terms or words used in the specification and claims described below should not be construed as being limited to the ordinary or dictionary meanings, and the inventors are appropriate to the concept of terms in order to explain their invention in the best way. It should be interpreted as meanings and concepts in accordance with the technical spirit of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the present specification and the configuration shown in the drawings are only preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, and various equivalents may be substituted for them at the time of the present application. It should be understood that there may be variations and variations.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

1 is a view showing a secondary battery according to the present invention, Figure 2 is a view showing the assembled state of the electrode lead, the lead sealant film and the case in the assembled state of the secondary battery of Figure 1, Figure 3 according to the present invention It is a figure which shows a lead sealant film.

1 to 3, the secondary battery 10 according to the present invention includes an electrode assembly 30, a lead sealant film 80, and a case 20.

Although not shown, the electrode assembly 30 is stacked in a state in which a positive electrode and a negative electrode are sequentially stacked, a long sheet type positive electrode and a negative electrode are laminated with a separator interposed therebetween, and wound in a circular cross-sectional structure. After the compression in one direction it can be a jelly-roll-type power generation device manufactured in a cross-sectional plate-like structure.

The electrode assembly 30 may include a plurality of electrode tabs 40 and 50. The plurality of electrode tabs 40 and 50 may include a positive electrode tab 40 extending from the current collector of the positive electrode and a negative electrode tab 50 extending from the current collector of the negative electrode. Here, when a plurality of positive electrode current collectors and negative electrode current collectors are provided, each of the positive electrode tab 40 and the positive electrode tab 50 may be provided in plural and may be integrally coupled by welding.

In addition, the electrode assembly 30 may include a plurality of electrode leads 60 and 70 electrically connected to the plurality of electrode tabs 40 and 50. The plurality of electrode leads 60 and 70 may include a positive electrode lead 60 electrically connected to the positive electrode tab 40, and a negative electrode lead 70 electrically connected to the negative electrode tab 50. . The positive electrode lead 60 and the negative electrode lead 70 may be electrically connected to the positive electrode tab 40 and the negative electrode tab 50 by welding.

The electrode assembly 30 may be embedded in the case 20 in a state where some of the plurality of electrode leads 60 and 70 are exposed to the outside.

The lead sealant film 80 may be attached to at least one side of each of the plurality of electrode leads 60 and 70 of the electrode assembly 30. That is, the lead sealant film 80 is provided between the plurality of electrode leads 60 and 70 and the case 20 to increase the sealing degree of the case 20, and the plurality of electrode leads 60 and 70 and the case 20. The electrical insulation state between them can be secured. When the lead sealant film 80 is attached to both sides of each of the plurality of electrode leads 60 and 70, the lead sealant film 80 may have the same length and overlap each other with each of the plurality of electrode leads 60 and 70 interposed therebetween. have.

The lead sealant film 80 may include a first layer 81, a second layer 82, and a third layer 83.

The first layer 81 is a layer in contact with the plurality of electrode leads 60 and 70, and may include a first compound including an acid-modified copolymer, an elastomer, and a low density olefin. Here, the first compound may further include an antioxidant.

The acid-modified copolymer may include at least one of maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene, carboxylic acid-modified polypropylene, carboxylic acid-modified polyethylene, acrylic-modified polypropylene, and acrylic-modified polyethylene.

For example, as the acid-modified polypropylene resin, random type polypropylene or block type polypropylene grafted with unsaturated carboxylic acid may be used. As the polypropylene, homo type polypropylene, random type polypropylene or block type polypropylene may be used. In addition, a mixture comprising three copolymers of ethylene and propylene and butene, which are copolymers containing these acid-modified polypropylenes and polypropylene and ethylene, and ethylene and propylene, ethylene and butene, propylene and butene, etc. Resin (high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, polyethylene resin with a density of 0.9 g / cm ³ or less, butadiene rubber, etc. can be added.

That is, the acid-modified polypropylene resin combines adhesion with the plurality of electrode leads 60 and 70 and good thermal fusion with the packaging material. A molecular weight of 10,000 or more can be used by denaturation with maleic anhydride.

The elastomer may comprise an olefinic rubber or an ethylene-based elastomer. The ethylene-based elastomer may include at least one of ethylene propene rubber (EPDM) and ethylene propylene copolymer (EPR).

The low density olefin may comprise at least one of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE).

Meanwhile, in the first layer 81, the ratio of the acid-modified copolymer in the first compound may be 20% or more. That is, by providing polarity to the first layer 81 through the acid-modified copolymer, it is possible to secure the adhesive force with the plurality of electrode leads 60 and 70. Here, when the ratio of the acid-modified copolymer is less than 20%, a problem may occur that the adhesive strength with the plurality of electrode leads 60 and 70 is lowered.

In addition, the first layer 81 may have a polypropylene or polyethylene content of 10 parts by weight or more based on 100 parts by weight of the acid-modified copolymer. In this case, the melting point of the first layer 81 may be between 130 and 150 ° C. That is, the first layer 81 may be set to have a melting point of 130 to 150 ° C. by controlling the content of polyflopropylene or polyethylene in the acid-modified copolymer. In the case where the melting point of the first layer 81 is less than 130 ° C., there is a problem that reliability cannot be secured when the user of the secondary battery is exposed to a high temperature environment. When the melting point of the first layer 81 exceeds 150 ° C., the difference in melting point with the second layer 82 becomes small, and as a result, a short circuit may occur during coextrusion. Here, the melting point refers to the temperature when the crystals of the polymer are completely dispersed, and in the present invention, 'melting point' refers to the temperature (melting temperature, Tm) when the crystal parts of the polymer are completely dispersed and fluidly changed.

The second layer 82 may be provided between the first layer 81 and the third layer 83, and may include a second compound including an acid-modified copolymer, an elastomer, and a low density olefin. Here, the second layer 82 may further include a crosslinking agent and an antioxidant.

The acid-modified copolymer may include at least one of maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene, carboxylic acid-modified polypropylene, carboxylic acid-modified polyethylene, acrylic-modified polypropylene, and acrylic-modified polyethylene.

For example, as the acid-modified polypropylene resin, random type polypropylene or block type polypropylene grafted with unsaturated carboxylic acid may be used. As the polypropylene, homo type polypropylene, random type polypropylene or block type polypropylene may be used. That is, the acid-modified polypropylene resin combines adhesion with the plurality of electrode leads 60 and 70 and good thermal fusion with the packaging material. A molecular weight of 10,000 or more can be used by denaturation with maleic anhydride.

The elastomer may comprise an olefinic rubber or an ethylene-based elastomer. The ethylene-based elastomer may include at least one of ethylene propene rubber (EPDM) and ethylene propylene copolymer (EPR).

The low density olefin may comprise at least one of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE).

Crosslinkers include Trimethylopropane Trimethacrylate (TMPTMA), pentaerythritol triacrylate, etched recall dimethacrylate, triallyl cyanurate (TAC), triarylisocyanurate (Triallyl isocyanuratet (TAIC)), dicumyl peroxide (DCP) and high vinylpolybutadiene (HVPBD) may be at least one selected from the group consisting of.

In addition, any crosslinking agent conventionally used as a crosslinking agent may be used, but is preferably dimethyloltricyclodecanediacrylate, divinylbenzene, ethylene glycol dimethacrylate, propyleneglycoldimethacrylate, 1,4-butanediol Dimethacrylate, 1,6-hexanediol dimethacrylate, neopentylglycol dimethacrylate, allyl methacrylate, allyl acrylate, bisphenol dimethacrylate, bisphenol diacrylate, cyclic aliphatic di At least one crosslinking agent selected from the group consisting of acrylate, diacrylated isocyanurate and trimethylolpropanetrimethacrylate can be used.

Here, the second layer 82 contains a crosslinking agent, and after co-extruding the first layer 81, the second layer 82, and the third layer 83, the second layer 82 is irradiated with an electron beam. By selectively crosslinking, the adhesive force between the first layer 81, the second layer 82 and the third layer 83 can be increased.

The antioxidant may include a phenolic antioxidant, and may include 0.1 to 0.4 parts by weight based on 100 parts by weight of the second compound included in the second layer 82. Here, when the antioxidant exceeds 0.4 parts by weight, a problem may occur that the adhesive force is lowered. For example, antioxidants can be used as a mixture of primary and secondary antioxidants, primary antioxidants are used as radical scavengers, and secondary antioxidants are used in the form of peroxide decomposers (Hydroperoxide (ROOH) decomposer). It is used as). In addition, Hindered phenol-based and Lactone-based antioxidants may be used as primary antioxidants, and phosphite-based and thioester-based antioxidants may be used as secondary antioxidants.

In addition, the second layer 82 may further include an inorganic filler. For example, the inorganic filler may include clay, silica, calcium carbonate (CaCO ₃ ), titanium dioxide (TiO ₂ ), glass fibers, and the like. Inorganic fillers have high surface energy and are not compatible with low olefinic polymers, but due to the content of acid-modified copolymers, the polarity of the polar fillers with the first layer 81 is higher than that of the second layer 82. By placing the inorganic filler at the interface of the polymer by the inter-molecular transfer phenomenon of the inorganic filler can increase the adhesion.

In addition, the second layer 82 may have a polypropylene or polyethylene content of 20 parts by weight or more based on 100 parts by weight of the acid-modified copolymer. In this case, the second layer 82 may have a melting point of 150 to 170 ° C. In the case where the melting point of the second layer 82 is less than 150 ° C., the melting point difference between the first layer 81 or the third layer 83 is small, which may cause a short circuit during coextrusion, and the melting point exceeds 170 ° C. It's hard to control.

The third layer 83 is bonded to the second layer 82 and is a portion that substantially contacts the case 20. The third layer 83 may include a third compound including an acid-modified copolymer, an elastomer and a vinyl copolymer. Here, the second layer 82 may further include an antioxidant.

The acid-modified copolymer may include at least one of maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene, carboxylic acid-modified polypropylene, carboxylic acid-modified polyethylene, acrylic-modified polypropylene, and acrylic-modified polyethylene.

For example, as the acid-modified polypropylene resin, random type polypropylene or block type polypropylene grafted with unsaturated carboxylic acid may be used. As the polypropylene, homo type polypropylene, random type polypropylene or block type polypropylene may be used. That is, the acid-modified polypropylene resin combines adhesion with the plurality of electrode leads 60 and 70 and good thermal fusion with the packaging material. A molecular weight of 10,000 or more can be used by denaturation with maleic anhydride.

The elastomer may comprise an olefinic rubber or an ethylene-based elastomer. The ethylene-based elastomer may include at least one of ethylene propene rubber (EPDM) and ethylene propylene copolymer (EPR).

The vinyl copolymer may include ethylene vinyl acetate copolymer or ethylene vinyl chloride copolymer.

In addition, the third layer 83 may have a polypropylene or polyethylene content of 10 parts by weight or more based on 100 parts by weight of the acid-modified copolymer. In this case, the first layer 83 may have a melting point between 130 and 150 ° C. That is, the third layer 83 may be set to have a melting point of 130 to 150 ° C. by controlling the content of polyflopropylene or polyethylene in the acid-modified copolymer. If the melting point of the third layer 83 is less than 130 ° C., there is a problem that reliability cannot be ensured when the user of the secondary battery is exposed to a high temperature environment. When the melting point of the third layer 83 exceeds 150 ° C, the difference in melting point with the second layer 82 becomes small, and as a result, a short circuit may occur during coextrusion.

That is, when the melting points of the first layer, the second layer, and the third layer are expressed by M1, M2, and M3, M2> M3> M1 may be satisfied. M2 may be 150 ~ 170 ℃. In addition, the difference between M1 and M2 is 15 to 20 ℃, the difference between M2 and M3 may be 15 to 20 ℃. That is, in the lead sealant film according to the present invention, the difference in melting temperature of adjacent layers may be set to 25 ° C., more preferably 15 ° C. to 20 ° C., in order to prevent interlayer peeling.

In addition, the melt index MI of the first layer may be 1 to 3, the melt index MI of the second layer may be 2 to 4, and the melt index MI of the third layer may be 4 to 7. The melt index (MI) is a flow rate when the polymer melt is extruded from the piston under a predetermined temperature, and is an index indicating the ease of flow of the melt.

In addition, the first layer, the second layer and the third layer may include 10 to 200 parts by weight of the elastomer, 10 to 200 parts by weight of the low density polyolefin based on 100 parts by weight of the acid-modified copolymer. Here, the first layer and the second layer may further include a heat resistant reinforcing additive, and the third layer may further include a metal adhesion enhancer.

Here, as the heat resistance strengthening additive, any resin added to enhance the heat resistance of the conventional film may be added, and preferably, polyimide resin, polyamideimide resin, polyesterimide resin, polyetherimide resin or polyamide resin It is preferable to add an etc.

In addition, as the metal adhesion enhancer, any resin conventionally added to enhance the metal adhesion of the film may be added. Preferably, a styrene block copolymer, a polyurethane copolymer, or an ethylene propylene copolymer may be added. It is preferable.

Meanwhile, when the lead sealant film according to the present invention is used for the cathode, the thickness of the first layer is 20 to 25 µm, the thickness of the second layer is 30 to 40 µm, and the thickness of the third layer is 50 to 60 µm. The thickness can be 100 to 125 mu m.

When the lead sealant film according to the present invention is used for the anode, the thickness of the first layer is 20 to 25 µm, the thickness of the second layer is 30 to 40 µm, and the thickness of the third layer is 50 to 60 µm. May be 150 to 160 μm.

In addition, the lead sealant film according to the present invention may have a yield strength of 15 to 40 N / mm ² , a tensile strength of 30 to 60 N / mm ² , and an elongation of 500 to 1000%.

The yield strength is the deformation when the external force is applied to the sample. The strength is the level of the elastic deformation that can be restored to the circular shape after the external force disappears and the plastic deformation that cannot be restored. Is the level of force, and elongation is the elongation of the sample at break, divided by the original length of the material.

In addition, the lead sealant film of the present invention may have an elongation of MD / TD of 0.9 to 1.1. Here, MD (Machine Direction) / TD (Transverse Direction) is a value obtained by dividing the shrinkage rate in the MD direction by the shrinkage rate in the TD direction. The smaller the difference between the shrinkage rate in the MD direction and the shrinkage rate in the TD direction is, the more the film shrinks. That means you can.

In addition, the MD / TD ratio of the elongation is 0.9 to 1.1 to minimize the difference in shrinkage in the MD direction and shrinkage in the TD direction. These results show that the lead sealant film according to the present invention is suitable for use as a lead electrode film of a secondary battery.

In addition, the lead sealant film according to the present invention may have a heat of fusion (ΔH) of 6 to 20 (J / g). In addition, the lead sealant film according to the present invention may have an adhesive strength of 15 to 35 N / cm.

The case 20 may accommodate the electrode assembly 30 therein with a portion of the plurality of electrode leads 60 and 70 exposed. The case 20 may include a case body 21 having a space for accommodating the electrode assembly 30, and a case cover 22 coupled to the case body 21 to seal the electrode assembly 30. have. The case body 21 and the case cover 22 may each include an outer coating layer 20a, a barrier layer 20b, and an inner sealant layer 20c. For example, the outer coating layer 20a may include a stretched nylon film ONy. For example, the barrier layer 20b may include aluminum. For example, the inner sealant layer 20c may comprise an unstretched polypropylene film (CPP). In addition, since a hot melt layer (not shown) is coated on the edge of the inner sealant layer 20c, the case body 21 and the case cover 22 may be tightly fixed to each other by heat and pressure through a heat fusion machine.

Hereinafter, a method of manufacturing the lead sealant film according to the present invention will be described.

4 is a flowchart illustrating a method of manufacturing a lead sealant film according to the present invention.

Referring to FIG. 4, first, a first compound, a second compound, and a third compound are prepared in step S10. Wherein the first compound may comprise an acid-modified copolymer, an elastomer and a low density polyolefin. The second compound can include acid-modified copolymers, elastomers and low density polyolefins. The third compound may include an acid-modified copolymer, an elastomer and a vinyl copolymer. Examples of acid-modified copolymers, elastomers, low-density polyolefins, and vinyl-based copolymers have been omitted. The first compound, the second compound and the third compound may be formed in the form of a master batch.

In addition, a crosslinking agent may be added to the second compound in step S10. By adding a crosslinking agent to the second compound, it is possible to selectively crosslink the second layer containing the second compound through electron beam irradiation in step S30 to be described later.

In addition, an antioxidant may be added to the first compound, the second compound, and the third compound in step S10, preferably, a crosslinking agent may be added to the second compound, and an antioxidant may be added to the first and third compounds. .

In addition, the inorganic filler may be added to the second compound in step S10. Here, the inorganic filler has a high surface energy and is not affinity with a low polar olefin polymer, but includes a first compound having a high polarity compared to a second layer containing a second compound by the content of an acid-modified copolymer. Due to the difference in polarity with the first layer, the inorganic filler may be positioned at the interface of the polymers due to the inter-polymer migration of the inorganic fillers, thereby increasing the adhesive force.

Next, in step S20, the first compound, the second compound, and the third compound of the master batch form are coextruded to include a first layer including the first compound, a second layer including the second compound, and a third compound. A lead sealant film including a third layer may be manufactured. In this case, by changing the content of polyethylene or polypropylene contained in the acid-modified copolymer of the first layer, the second layer and the third layer, the melting point between the first layer, the second layer and the third layer is changed to separate the adhesive layer. It is possible to produce a lead sealant film having a laminate structure through coextrusion without this need. Accordingly, the manufacturing method of the lead sealant film according to the present invention can reduce the manufacturing cost.

For example, when the melting points of the first layer, the second layer, and the third layer are expressed by M1, M2, and M3, M2> M1> M3 may be satisfied. Here, the difference between M1 and M3 may be 10 ~ 20 ℃. Here, the melting point M2 of the second layer 82 may be 150 to 170 ° C, and the melting points M1 and M3 of the first layer and the third layer may be 130 to 150 ° C.

Next, in step S30, the lead sealant film may be irradiated with an electron beam to selectively crosslink the second layer. That is, the crosslinking agent may be included in the second compound in step S10, and the crosslinking agent may be selectively crosslinked by irradiating an electron beam in step S30 to double the adhesive force between the first layer, the second layer, and the third layer.

Next, the lead sealant film according to the present invention may be manufactured by completely laminating the lead sealant film in a step S40.

Meanwhile, in the method of manufacturing a lead sealant film according to the present invention, a thermal lamination process (S40) is performed after the electron beam is irradiated (S30) to the coextruded lead sealant film, but the present invention is not limited thereto. After the electron beam can be irradiated (S30).

Hereinafter, the characteristics of the lead sealant film according to the present invention will be described through examples.

Example

3 layer consisting of 1st layer (outer layer, pouch layer)-2nd layer (heat resistant layer, core layer)-3rd layer (inner layer, metal layer) using 3-layer pilot co-extruder A layered lead sealant film was prepared.

The first layer (outer layer, pouch layer) and the second layer (core layer, heat resistant layer) are acid-modified copolymers, ter-PP (TerPolymer Polypropylene), olefin-based rubber, EBR (Ethylene-Butylene Rubber) and linear low density polyethylene ( LLDPE) was used, and the third layer (inner layer, metal layer) was an acid-modified copolymer, ter-PP (TerPolymer Polypropylene), ethylene vinyl acetate copolymer (EVA), and an olefinic rubber, EBR (Ethylene-). Butylene Rubber) was used as the polymer composition. At this time, the total thickness of the film was 100 μm (produced for the cathode lead).

The mixing ratio of each polymer in each layer is different when the film is used for the cathode lead and the anode lead, the ratio is shown in Table 1 below was prepared accordingly.

At this time, melting temperature (Tm, melting temperature) is the first layer (outer layer, pouch layer) and the third layer (inner layer, metal layer) is 145 ℃, the second layer (core layer, heat-resistant layer) is 160 ℃, melting The melt index (MI) is in the range of 1 to 3 for the first layer (outer layer, pouch layer) and 2nd layer (core layer, heat resistant layer) and 3 to 3 for the third layer (inner layer, metal layer). Each resin was coextruded by adjustment to produce a lead sealant film having a three-layer laminate structure.

More specifically, in Example 1, the melting point (Melting index, MI) of the first layer is 2 ± 1, the melting point is 144.31 ° C, the second layer is the melting point is 3 ± 1, and the melting point is 163.81 ° C. In the third layer, the melting point was 6 ± 1 and the melting point was set at 144.51 ° C.

In Example 2, the melting index of the first layer is 2 ± 1, the melting point is 145.15 ° C, the second layer is the melting index of 3 ± 1, the melting point is 164.04 ° C, and the third layer is the melting index of 5 ± 1. It set to 1 and set melting | fusing point to 147.11 degreeC.

Melting temperature (Tm, melting temperature) is the temperature at which the polymer changes from a solid state to a fluid liquid state, and melt index (MI, melt index) is the flow rate when the polymer melt is extruded from the piston under a predetermined temperature, It is an index indicating ease.

Specific configurations are shown in Table 2 below, and two versions of the lead film were prepared as shown in Table 3 below.

Specifically, the configuration of Example 1 is the same as in Table 2, in the case of Example 2 was added to the heat resistant reinforcing additive was added to the first layer and the second layer, was prepared by additionally adding a metal adhesion enhancer to the third layer. .

Film total thickness (㎛)	Cathode Lead	For anode lead
Full thickness	100 ± 10%	150 ± 10%
First floor	20 ± 10%, 25 ± 10%	20 ± 10%, 25 ± 10%
The second layer	30 ± 10%	30 ± 10%
3rd floor	50 ± 10%	100 ± 10%

rescue	Tm	Meterial	MI
First floor	145	Main ingredient 1: ter-PP (PP-PE-MAH) = acid-modified PP = copolymer = Random PP = PP-g-MAH main ingredient 2: EBR (Ethylene-Butylene Rubber) = olefin-based rubber main ingredient 3: LLDPE = PE Other Ingredients: Grafting Agent	1 to 3
The second layer	160	Main ingredient 1: ter-PP (PP-PE-MAH) = acid-modified PP = 3 copolymer = RandomPP = PP-g-MAH Main ingredient 2: EBR (Ethylene-Butylene Rubber) = olefin-based rubber, main ingredient 3: LLDPE = PE Other Ingredients: Grafting Agent	1 to 3
3rd floor	145	Main ingredient 1: ter-PP (PP-PE-MAH) = acid-modified PP = copolymer = Random PP = PP-g-MAH main ingredient 2: EVA (ethylene-vinyl acetate copolymer), main ingredient 3: EPR (Ethylene -Propylene Rubber, Other Ingredients: Grafting Agent	5 ~ 7

	Example 1			Example 2
	First floor	The second layer	3rd floor	First floor	The second layer	3rd floor
MI	2 ± 1	3 ± 1	6 ± 1	2 ± 1	3 ± 1	5 ± 1
Tm	144.31 ℃	163.81 ℃	144.51 ℃	145.15 ℃	164.04 ℃	147.11 ℃

Tensile physical properties of the lead sealant films according to Examples 1 and 2 were measured.

Table 4 is a table showing the tensile properties of the lead sealant film according to Example 1 and Example 2.

		Example 1		Example 2
		100 μm	150	100	150
Yield strength	MD	18.93 N / ㎡	19.70 N / ㎡	21.33 N / ㎡	22.12 N / mm2
	TD			20.38 N / ㎡	21.01 N / ㎡
The tensile strength	MD	37.45 N / ㎡	40.11 N / ㎡	40.77 N / ㎡	50.00 N / ㎡
	TD			39.18 N / ㎡	38.18 N / ㎡
Elongation	MD	727.03%	778.76%	708.50%	777.99%
	TD			806.77%	796.49%

Referring to Table 4, the lead sealant film prepared in Example was cut to 10 mm x 70 mm to measure yield strength, tensile strength, and elongation.

Yield strength is related to the rigidity of the film, and considering the manufacturing processability (film supply, heat fusion process, softening, etc.), the appropriate range is 15 to 40 N / mm2. The lead sealant films according to Examples 1 and 2 were found to satisfy all of the appropriate ranges.

In addition, considering the manufacturing processability, the proper tensile strength is 30 ~ 60 N / ㎜, elongation is 500 ~ 1000% level, the lead sealant film according to Example 1 and Example 2 to satisfy both the appropriate tensile strength and the loss rate Confirmed.

On the other hand, Table 5 is a table analyzing the thermal characteristics of the lead sealant film according to Examples 1 and 2 of the present invention.

	Example 1		Example 2
	Temp. (℃)	ΔH (J / g)	Temp. (℃)	H (J / g)
Tm-1	126	1.04	122.62	1.432
Tm-2	143	9.62	149.28	18.86
Tm-3	164	4.04	165.53	7.278
Tc-1			103.11	46.09
Tc-2			115.09	18.23

Referring to Table 5, the thermal characteristics of the temperature and temperature reduction rate of 10 ℃ / min under a nitrogen stream using a TA Instrument differential scanning thermal analyzer (DSC) was analyzed, and the results are shown in Table 5 below.

It can be seen that the lead sealant films according to Examples 1 and 2 of the present invention exhibit excellent thermal characteristics.

In addition, the heat of melting of the melting temperature of Example 2 is higher than that of Example 1, it can be seen that the heat-resistant reinforcing additive is added to show a strong effect on the denaturation by heat.

Also, as a result of analyzing the thermal characteristics, it was confirmed that the heat of fusion (ΔH) of similar melting temperature (Tm) is higher in Example 2 (lead film ver2) than Example 1 (lead film ver1). In the case of Example 2, the heat of fusion was increased by adding a heat-resistant reinforcing agent, and the higher the heat of fusion means better heat resistance.

Melting temperature (Tm, Melting temperature) is the temperature at which the polymer changes from a solid state to a fluid liquid state and refers to the temperature at which the flow of the crystal portion starts. In the present invention, the temperature at which the crystal portion of the lead sealant film changes fluidly it means.

The heat of fusion (ΔH) refers to the energy required when a substance changes from a solid to a liquid. In the present invention, the heat of fusion refers to the energy applied when a crystalline portion of a polymer starts to flow into a fluid liquid state.

In addition, Table 6 is a table which measured the adhesive force with the electrode lead of the lead sealant film which concerns on Examples 1 and 2 of this invention.

	Example 1		Example 2		Remarks
	Cathode (Cu)	Anode (Al)	Cathode (Cu)	Anode (Al)
BT	18.2 N / cm	27.5 N / cm	23.01 N / cm	33.79 N / cm	Adhesion before electrolyte impregnation
DBT	15.1 N / cm	17.7 N / cm	19.99 N / cm	32.1 N / cm	Adhesion after electrolyte impregnation

Referring to Table 6, Examples 1 and 2 confirmed that there is no significant difference in the adhesive strength before and after the impregnation in the electrolyte solution. In addition, in Example 2 to which the metal adhesion enhancer is added, it can be seen that the adhesion is measured higher. These results show that the lead sealant film of this invention shows the outstanding adhesiveness as a lead film.

Comparative Example 1

In Comparative Example 1, a first compound, a second compound, and a third compound, which were the same as in Example 2, were prepared, and the first compound, the second compound, and the third compound were sequentially laminated and coextruded to prepare a film.

Table 7 below is a table showing the tensile properties of the lead sealant film according to the Examples and Comparative Examples.

		Comparative example		Example
		100 μm	150	100	150
Yield strength	MD	14.93 N / mm2	15.70 N / ㎡	21.33 N / ㎡	22.12 N / mm2
	TD	13.43 N / ㎡	14.23 N / ㎡	20.38 N / ㎡	21.01 N / ㎡
The tensile strength	MD	25.45 N / ㎡	27.11 N / ㎡	40.77 N / ㎡	50.00 N / ㎡
	TD	24.35 N / mm2	26.25 N / mm2	39.18 N / ㎡	38.18 N / ㎡
Elongation	MD	486.05%	443.76%	708.50%	777.99%
	TD	495.03%	452.76%	806.77%	796.49%

Referring to Table 7, tensile properties of Example 2 and Comparative Example 1 were analyzed.

Yield strength, on the other hand, is related to the rigidity of the film, and considering the manufacturing process (film supply, heat fusion process, softening, etc.), the appropriate range is 15 to 40 N / mm2.

As a result of measuring the yield strength for Example 2 and Comparative Example 1, Example 2 is included in the yield strength of 15 ~ 40 N / ㎜, Comparative Example 1 is 15 N / which is a low level compared to Example 2 It confirmed that it was mm <2> or less.

In addition, considering the manufacturing processability, the appropriate tensile strength is 30 ~ 60 N / ㎜, elongation is 500 ~ 1000% level, Example 2 satisfies both the appropriate tensile strength and elongation, whereas the comparative example is 30N / It was confirmed that the mm 2 or less and the elongation were 500% or less.

As a result of the comparison between Example 2 and Comparative Example 1, it can be confirmed that Example 2 has a significantly higher tensile properties compared to Comparative Example 1.

Comparative Example 2

In Comparative Example 2, a first compound, a second compound, and a third compound, which were the same as in Example 2, were prepared, and the first compound, the second compound, and the third compound were sequentially laminated and coextruded to prepare a film. Here, the ter-ppp (PP-PE-MAH) ratio of the first compound was set to 15%.

Table 1 below is a table measuring the adhesion of the lead sealant film according to Example 2 and Comparative Example 2.

	Comparative example		Example		Remarks
	Cathode (Cu)	Anode (Al)	Cathode (Cu)	Anode (Al)
BT	15.2 N / cm	25.5 N / cm	23.01 N / cm	33.79 N / cm	Adhesion before electrolyte impregnation
DBT	11.3 N / cm	18.5 N / cm	19.99 N / cm	32.1 N / cm	Adhesion after electrolyte impregnation

Referring to Table 8, as a result of analyzing the adhesion properties between the electrode leads of Example 2 and Comparative Example 2, it can be seen that the adhesion of Example 2 is significantly higher than the comparative example for both the positive electrode and the negative electrode.

The lead sealant film according to Example 2 of the present invention sets the content of the acid-modified copolymer of the first layer to 20% or more, thereby giving polarity to the first layer in direct contact with the electrode lead, It can be seen that the adhesion can be increased.

On the other hand, the embodiments disclosed in the drawings are merely presented specific examples to aid understanding, and are not intended to limit the scope of the invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

Claims (29)

1. A first layer comprising an acid-modified copolymer, an elastomer and a low density polyolefin;

   A second layer bonded on the first layer and comprising an acid-modified copolymer, an elastomer and a low density polyolefin; And

   A third layer bonded on the second layer and including an acid-modified copolymer, an elastomer and a vinyl copolymer;

   Lead sealant film comprising a.
2. The method of claim 1,

   The melting point of the said 1st layer, the said 2nd layer, and the said 3rd layer is M1, M2, and M3, M2> M3> M1 is satisfied. The lead sealant film characterized by the above-mentioned.
3. The method of claim 1,

   Lead sealant film, characterized in that M2 is 150 ~ 170 ℃.
4. The method of claim 1,

   The difference between the M1 and the M2 is 15 to 20 ℃, the difference between the M2 and the M3 is 15 to 20 ℃ lead sealant film, characterized in that.
5. The method of claim 1,

   Lead sealant film, characterized in that the melt index (MI) of the first layer is 1 to 3, the melt index (MI) of the second layer is 2 to 4, the melt index (MI) of the third layer is 4 to 7. .
6. The method of claim 1,

   The acid-modified copolymer may include at least one of maleic anhydride-modified polypropylene, maleic anhydride-modified polyethylene, carboxylic acid-modified polypropylene, carboxylic acid-modified polyethylene, acrylic-modified polypropylene, and acrylic-modified polyethylene. Sealant film.
7. The method of claim 1,

   The elastic body includes an olefin rubber or an ethylene elastic body,

   The ethylene-based elastic body is a lead sealant film, characterized in that it comprises at least one of ethylene propene rubber (EPDM) and ethylene propylene copolymer (EPR).
8. The method of claim 1,

   The low density polyolefin is a lead sealant film, characterized in that it comprises at least one of low density polyethylene (LDPE) and linear low density polyethylene (LLDPE).
9. The method of claim 1,

   The content of polypropylene or polyethylene is 100 parts by weight or more based on 100 parts by weight of the acid-modified copolymer of each of the first layer, the second layer and the third layer, and the second layer is 20 parts by weight. As mentioned above, the said 3rd layer is 10 weight part or more, The lead sealant film characterized by the above-mentioned.
10. The method of claim 1,

    The first layer is a lead sealant film, characterized in that the ratio of the acid-modified copolymer to 20 parts by weight or more.
11. The method of claim 1,

    The second layer further comprises a crosslinking agent,

    The crosslinking agent is at least one selected from the group consisting of trimetholpropane methacrylate, pentaerythritol triacrylate, etched recall dimethacrylate, triallyl cyanurate and triarylisocyanurate Lead sealant film.
12. The method of claim 11,

    The second layer further comprises a phenol-based antioxidant,

    The phenolic antioxidant comprises 0.1 to 0.4 parts by weight based on 100 parts by weight of the compound contained in the second layer.
13. The method of claim 1,

    The first layer, the second layer and the third layer is 10 to 200 parts by weight of the elastomer, 10 to 200 parts by weight of the low density polyolefin with respect to 100 parts by weight of the acid-modified copolymer.
14. The method of claim 1,

    When the lead sealant film is used for the cathode, the thickness of the first layer is 20 to 25 µm, the thickness of the second layer is 30 to 40 µm, the thickness of the third layer is 50 to 60 µm, and the first layer The total thickness of the second layer and the third layer is 100 to 125㎛, characterized in that the lead sealant film.
15. The method of claim 1,

    When the lead sealant film is used for the anode, the thickness of the first layer is 20 to 25 µm, the thickness of the second layer is 30 to 40 µm, the thickness of the third layer is 100 to 110 µm, and the first layer The total thickness of the second layer and the third layer is 150 to 160㎛, characterized in that the lead sealant film.
16. The method of claim 1,

    And the first layer, the second layer and the third layer further comprise a grafting agent.
17. The method of claim 1,

    The first sealant and the second layer further comprises a heat resistant strengthening additive.
18. The method of claim 1,

    The third layer further comprises a metal adhesion enhancer.
19. The method of claim 1,

    A yield sealant having a yield strength of 15 to 40 N / mm ² , a tensile strength of 30 to 60 N / mm ² , and an elongation of 500 to 1000%.
20. The method of claim 1,

    A lead sealant film having an elongation of MD / TD of 0.9 to 1.1.
21. The method of claim 1,

    Heat of fusion (ΔH) is 6 to 20 (J / g), characterized in that the lead sealant film.
22. The method of claim 1,

    Lead sealant film, characterized in that the adhesive force of 15 to 35 N / cm.
23. An electrode assembly including a plurality of electrode tabs and a plurality of electrode leads connected to the plurality of electrode tabs and exposed to the outside;

    A lead sealant film attached to at least one side of each of the plurality of electrode leads;

    A case accommodating the electrode assembly with a portion of the plurality of electrode leads exposed to the outside; Including,

    The lead sealant film is bonded between the electrode lead and the case, the first layer comprising an acid-modified copolymer, an elastomer and a low density polyolefin, is bonded on the first layer, the acid-modified copolymer, an elastomer and a low density polyolefin A secondary battery comprising a second layer comprising a and a third layer bonded to the second layer, the acid-modified copolymer, an elastomer and a vinyl-based copolymer.
24. A first compound comprising an acid-modified copolymer, an elastomer and a low density polyolefin, a second compound comprising an acid-modified copolymer, an elastomer and a low density polyolefin, and a third compound comprising an acid-modified copolymer, an elastomer and a vinyl-based copolymer. Manufacturing step;

    Co-extrusion of the said 1st compound, the said 2nd compound, and the said 3rd compound, The 1st layer which comprises the said 1st compound, The 2nd layer which contains the said 2nd compound, and the 3rd layer which comprises the said 3rd compound Manufacturing a lead sealant film comprising a;

    Method for producing a lead sealant film comprising a.
25. The method of claim 24,

    In the step of preparing the compound,

    A crosslinking agent is added to the said 2nd compound, The manufacturing method of the lead sealant film characterized by the above-mentioned.
26. The method of claim 24,

    After manufacturing the lead sealant film,

    Irradiating an electron beam on the lead sealant film;

    Method of producing a sealant film further comprising a.
27. The method of claim 26,

    Irradiating the electron beam,

    And selectively crosslinking the second layer.
28. The method of claim 27,

    After irradiating the electron beam,

    Laminating the lead sealant film irradiated with the electron beam through a thermal lamination process;

    Method of producing a sealant film further comprising a.
29. The method of claim 24,

    In the step of preparing the compound,

    An inorganic filler is added to the said 2nd compound, The manufacturing method of the sealant film characterized by the above-mentioned.

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