KR20170068332A - Secondary battery in pouch type and method for manufacturing of the same - Google Patents

Abstract

The present invention relates to a pouch type secondary battery and a method of manufacturing the same, and more particularly, to a pouch type secondary battery including an electrode assembly, and an upper pouch film and a lower pouch film, And a sealing portion in which the upper pouch film and the lower pouch film are in close contact with each other, wherein at least a part of the sealing portion includes a venting portion for guiding the gas discharge, And a pouch type secondary battery including a nonconductive material between the membrane and the lower pouch membrane.
Since the pouch-type secondary battery according to the present invention includes the venting portion, when gas is generated in the pouch-type secondary battery under certain circumstances, it is possible to induce the discharge of gas only to the venting portion, There is an effect that the explosion can be prevented in advance. Further, since the nonconductive material in the venting portion is made of materials that do not affect the insulating property, electrical insulation between the metal portion in the pouch film and internal and external components of the secondary battery can be ensured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pouch type secondary battery,

The present invention relates to a pouch-type secondary battery and a method of manufacturing the same.

As technology development and demand for mobile devices have increased, the demand for secondary batteries as energy sources has been rapidly increasing, and accordingly, a lot of researches on batteries that can meet various demands have been conducted.

Typically, in view of the shape of the battery, there is a demand for a prismatic battery and a pouch type battery which can be applied to products such as cellular phones with a thin thickness, and a lithium cobalt polymer battery having excellent energy density, discharge voltage, Demand for secondary batteries is high.

One of the major research tasks in such secondary batteries is to improve safety. Generally, a lithium secondary battery is a lithium secondary battery having a high temperature and a high pressure inside the battery which can be caused by an abnormal operating state of the battery such as an internal short circuit, a charging state exceeding an allowable current or a voltage, exposure to a high temperature, Thereby causing explosion of the battery.

In such a case, there is a possibility that an internal short circuit may occur in a pouch type secondary battery upon impact such as dropping or an external force.

BACKGROUND ART [0002] In recent years, rechargeable secondary batteries have been widely used as energy sources for wireless mobile devices. The secondary battery is also attracting attention as a power source for electric vehicles, hybrid electric vehicles, and the like, which is proposed as a solution for air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels.

BACKGROUND ART [0002] Medium- to large-sized devices such as automobiles use a middle- or large-sized battery system in which a plurality of battery cells are electrically connected to each other due to the necessity of a high output large capacity. The pouch-type lithium ion polymer secondary battery, which is often used as a unit cell in such a middle- or large-sized battery system, has a relatively large size as compared with the same-type battery used in a small-sized device.

The pouch-type polymer secondary battery includes an electrode assembly, electrode tabs extending from the electrode assembly, electrode leads welded to the electrode tabs, and a pouch-type sheathing member made of a laminate sheet of a polymer resin and aluminum .

 One advantage of the pouch-type battery is that venting occurs in which the gas is discharged without exploding in a specific situation. However, it can be a problem because gas emissions occur in unexpected areas. If the gas is vented from various directions inside the pack rather than in one direction, the gas may not be easily discharged to the outside. If the gas is generated inside the battery, the internal gas must be discharged more quickly to secure safety. The time required for the gas to be vented is prolonged, and the safety of the battery is greatly reduced.

Accordingly, there is a high demand for a pouch-type secondary battery which can quickly dissolve the battery when the internal pressure becomes higher than a certain level, thereby preventing rupture or explosion in advance.

Korean Patent No. 10-0959090

The present invention also provides a pouch-type secondary battery including a non-conductive material in a sealing portion of the pouch type secondary battery so that the sealing portion of the pouch type secondary battery can be bent only at a predetermined portion in a gas generating state.

A second technical object of the present invention is to provide a method for manufacturing the pouch type secondary battery, and a battery module and a battery pack including the pouch type secondary battery.

According to an aspect of the present invention, there is provided a pouch type secondary battery including an electrode assembly, and an upper pouch film and a lower pouch film, wherein the pouch type secondary battery includes the electrode assembly between the upper pouch film and the lower pouch film, And at least a part of the sealing portion includes a venting portion for guiding the gas discharge, and the venting portion is provided between the upper pouch film and the lower pouch film, A pouch-type secondary battery including a conductive material is provided.

The present invention also provides a method of manufacturing a pouch type secondary battery, comprising the steps of: (1) determining a venting portion on a sealing portion of a pouch type secondary battery; Placing at least one of the upper pouch film or the lower pouch film on the portion to be vented determined in Step 1 (Step 2); And sealing the sealing portion (Step 3). The present invention also provides a method of manufacturing the pouch type secondary battery.

Since the pouch-type secondary battery according to the present invention includes the venting portion, when gas is generated in the pouch-type secondary battery under certain circumstances, it is possible to induce the discharge of gas only to the venting portion, There is an effect that the explosion can be prevented in advance.

Further, since the nonconductive material in the venting portion is made of materials that do not affect the insulating property, electrical insulation between the metal portion in the pouch film and internal and external components of the secondary battery can be ensured.

1 is an exploded perspective view showing the configuration of a pouch-type secondary battery according to an embodiment of the present invention.
2 is a cross-sectional view of a surface of the pouch type secondary battery according to an embodiment of the present invention in which the upper pouch film and the lower pouch film closely contact each other.
3 is a cross-sectional view of a surface of the pouch type secondary battery according to another embodiment of the present invention in which the upper pouch film and the lower pouch film closely contact each other.
Fig. 4 is a photograph of the specimens prepared in Example 2, Example 3, and Comparative Example 1 visually observed after a sealing test. Fig.
5 is a graph showing the results of sealing tests of the specimens prepared in Example 2, Example 3, and Comparative Example 1. Fig.
Fig. 6 is a photograph showing one example of the method for producing the specimen and the measurement of the sealing strength, which are manufactured in Example 2, Example 3, and Comparative Example 1. Fig.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

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

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

In this specification, the terms "comprising," "comprising," or "having ", and the like are intended to specify the presence of stated features, But do not preclude the presence or addition of one or more other features, integers, steps, components, or combinations thereof.

In the pouch type secondary battery 10 including the electrode assembly 100 according to the present invention and the upper pouch film 200 and the lower pouch film 300, A receiving part 500 for accommodating the electrode assembly 100 and a sealing part 600 in which the upper pouch film 200 and the lower pouch film 300 are in close contact with each other are provided between the lower pouch film 200 and the lower pouch film 300, Wherein at least a portion of the sealing portion 600 includes a venting portion 700 for guiding the gas discharge and the venting portion 700 is disposed between the upper pouch layer 200 and the lower pouch layer 300 Non-conductive material 800 may be included.

Conventionally, when gas is generated inside the pouch type secondary battery under certain circumstances, gas discharge occurs at an unexpected portion of the sealing portion of the pouch. At this time, gas discharge may occur simultaneously in various directions, The discharge time is prolonged, which poses a problem in the stability of the secondary battery.

However, since the pouch-type secondary battery according to the present invention includes the venting part including the non-conductive material in the sealing part, it is possible to induce the discharge of the gas into the venting part when the gas is generated inside the pouch- , The problem of gas generation can be solved quickly, and rupture or explosion can be prevented in advance.

The pouch type secondary battery 10 may include a receiving part 500. The receiving part 500 may be a part of the electrode assembly 100 housed between the upper pouch film 200 and the upper pouch film 300. The accommodating part 500 may further contain an electrolyte solution in addition to a part of the electrode assembly 100 and the inner space of the accommodating part 500 may be sealed by the sealing part 600. Here, the electrode assembly 100 means a separator interposed between the anode and the cathode, the collector in the anode, and the electrode tab 400 extending from the collector in the cathode, The portion of the electrode assembly 100 included in the electrode assembly 500 may refer to a portion composed of the positive electrode, the negative electrode, and the separator, and a portion of the electrode tab 400, as shown in FIGS.

The pouch type secondary battery 10 may include a sealing part 600. The sealing part 600 is a part where the upper pouch film 200 and the lower pouch film 300 are in close contact with each other and thereby the inner space of the receiving part 500 is sealed, And the electrolytic solution to the outside. The sealing part 600 may be located on the outer peripheral surface of the upper pouch film 200 and the lower pouch film 300.

At this time, at least a part of the sealing portion 600 may include a venting portion 700 for guiding gas discharge.

During use of the secondary battery, gas may be generated inside the secondary battery. In this case, internal pressure of the secondary battery may increase and swelling may occur.

Such gas generation may occur due to various causes such as overcharging, overdischarge, short circuit, and high temperature disconnection. This may lead to damage to the secondary battery as well as explosion or ignition, which is further problematic. In addition, since the gas is generated inside the secondary battery and the sealing portion of the pouch is broken, the gas can be leaked to the outside. It is difficult to predict in which direction the gas will flow out because there are various kinds of broken portions of the sealing portion.

However, in the present invention, a specific portion is opened in the sealing portion 600, such as the venting portion 700, including the venting portion 700 for guiding the gas discharge, so that the gas generated in the secondary battery can pass through a safe outflow path To be discharged. The venting part 700 may be formed in the sealing part 600.

2 and 3, the venting part 700 includes a sealing part 600 including the electrode tab 400, which is a part of the electrode assembly 100, One may be formed.

When the venting part 700 is formed on one side where the electrode tab 400 is not formed, the space for forming the venting part 700 is widened, It is possible to solve the problem that the electrode tab 400 included in the electrode tab 400 may exert a slight influence on the internal pressure condition at which the venting occurs.

Also, since the venting part 700 is formed as one inside the sealing part 600, it is possible to more easily adjust the internal pressure at which the venting occurs.

However, the forming position and the number of the venting portions 700 are not limited by the above description.

The venting portion 700 may refer to a portion where the nonconductive material 800 exists. More specifically, as shown in FIG. 2, in a group of the nonconductive material 800, the direction of the non-conductive material (hereinafter, referred to as " The point on the outer line 610 of the sealing portion closest to the outermost nonconductive materials 810 and 820 and the point on the outermost nonconductive material 810 and 820 closest to the outermost non- 810 and 820 and the inner line 620 of the closest sealing portion and the outer line 610 of the sealing portion and the inner line 620 of the sealing portion.

Since the venting part 700 includes the nonconductive material 800 between the upper pouch film 200 and the lower pouch film 300, The adhesive force between the sealing portion 600 and the lower pouch film 300 can be reduced. Therefore, when the pressure of the accommodating part 500 is increased due to the gas generated in the secondary battery, the venting part 700 having a low adhesive force can be opened first, It is possible to discharge the internal gas more quickly.

The area of the venting portion 700 may be 20% to 50% of the area of the sealing portion 600. If the following venting portion is less than 20% of the sealing portion, the gas can not be smoothly discharged. If the venting portion is more than 50%, the electrolyte or the like in the accommodating portion 500 may be excessively discharged . Herein, the area of the sealing part means the area of the surface where the upper pouch film or the lower pouch film abuts, and the area of the venting part means the area of the part corresponding to the venting part among the surfaces abutted by the upper pouch film or the lower pouch film. do.

In this case, the nonconductive material 800 may be included in the range of 30% to 70% with respect to the total area of the venting part 700. In this case, the area of the nonconductive material refers to an area occupied by the nonconductive material when a cross section of the upper pouch film or the lower pouch film is taken as a cross section.

If the area occupied by the nonconductive material is less than 30% of the total area of the venting portion, the adhesion of the venting portion is similar to that of the sealing portion rather than the venting portion. If it is more than 70%, the adhesive force is excessively lowered, and the inside of the battery may be opened even though it is not at the level of dangerous pressure.

For example, when the nonconductive material is contained in an amount of 30% to 70% with respect to the total area of the venting portion, an internal pressure at which bending of the pouch type secondary battery occurs may be 0.4 N / mm ² to 0.7 N / mm ² have. Thus, by regulating the amount of the nonconductive material included in the area of the venting portion, the internal pressure at which the venting occurs can be controlled.

The nonconductive material 800 may be selected from the group consisting of nonconductive carbon, oil, and nanoceramic particles.

Since the nonconductive material in the venting portion is made of materials that do not affect the insulating property, electrical insulation between the metal portion in the pouch film and the internal and external components of the secondary battery can be ensured.

On the other hand, at least one of the upper pouch film and the lower pouch film protects the internal components such as the electrode assembly and the electrolytic solution, and the metal thin film to improve the electrochemical properties of the electrode assembly and the electrolytic solution, Especially aluminum foil. The aluminum thin film is interposed between the insulating layers formed of an insulating material so as to secure electrical insulation between the components inside the secondary battery such as the electrode assembly and the electrolyte, and other components outside the secondary battery.

The nonconductive material 800 in the venting portion 700 may be present in the sealing portion 600 where the upper pouch film 200 and the lower pouch film 300 are in close contact with each other and specifically the upper pouch film 200 and the insulating layer of the lower pouch film 300. The insulating layer of FIG.

Therefore, even if the nonconductive material 800 is inserted to induce venting in a specific portion of the sealing portion 600, the nonconductive material may not affect the insulation of the insulating layer because the nonconductive material is an insulating material.

In particular, when the nonconductive material 800 is in the form of beads, the nonconductive material 800 may be embedded in the insulating layer. In this case, the average diameter (d50) of the nonconductive material may be a spherical shape of 0.1 to 1 占 퐉, and an aspect ratio (length of the long axis / short axis length) of 1 to 2 may be used.

As described above, when the nonconductive material is spherical, it is easier to control the venting according to the pressure as compared with the case of the plate type.

In one embodiment of the present invention, the average diameter (D50) of the nonconductive material may be defined as a particle diameter at a 50% of the particle diameter distribution of the particles. The average particle size (D50) of the particles can be measured using, for example, a laser diffraction method. The laser diffraction method generally enables measurement of a particle diameter of several millimeters from a submicron region, resulting in high reproducibility and high degradability.

For example, at least one of the upper pouch film and the lower pouch film may be formed by successively laminating a PET outer layer / a Nylon layer / an Al metal foil layer / a PP inner layer successively.

At this time, the PP inner layer of the upper pouch film 200 and the PP inner layer of the lower pouch film 300 may be in close contact with each other, and the venting portion 700 in the sealing portion 600, The nonconductive material 800 may be present, and as a result, the nonconductive material 800 may be present on the surface of the PP inner layer.

For example, if the nonconductive material is in the form of beads, at least a portion of the beads may be present in the PP inner layer.

The electrode assembly 100 may include an anode, a cathode, a separator interposed between the anode and the cathode, a collector in the anode, and an electrode tab 400 extending from the collector in the cathode.

The positive electrode may be prepared by applying a slurry prepared by mixing a positive electrode mixture containing a positive electrode active material particle, a conductive material and a binder to an organic solvent, applying the slurry on the positive electrode collector, followed by drying and rolling. The negative electrode may be prepared by coating a negative electrode active material particle, a conductive material, and a negative electrode material mixture containing a binder in an organic solvent on a negative electrode current collector, followed by drying and rolling.

The cathode active material is not particularly limited, but a lithium transition metal oxide may be specifically used. Examples of the lithium transition metal oxide include a Li-Co-based composite oxide such as LiCoO ₂ , a Li-Ni-Co-Mn-based composite oxide such as LiNi _x Co _y Mn _z O ₂ , Li such as LiNiO ₂ Ni-based composite oxide, and Li-Mn-based composite oxide such as LiMn ₂ O ₄ , and these may be used singly or in combination.

As the negative electrode active material used for the negative electrode according to an embodiment of the present invention, a carbon material, lithium metal, silicon, or tin which lithium ions can be occluded and released can be used. Preferably, carbon materials can be used, and carbon materials such as low-crystalline carbon and highly-crystalline carbon can be used. Examples of the low crystalline carbon include soft carbon and hard carbon. Examples of highly crystalline carbon include natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber high temperature sintered carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.

The current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, the collector may be made of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel Treated with carbon, nickel, titanium, silver or the like may be used.

Examples of the binder include polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, Polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM) Various kinds of binder polymers such as sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, poly acrylic acid, polymers substituted with Li, Na or Ca, or various copolymers thereof are used .

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black, acetylene black, Ketjen black, channel black, panes black, lamp black, and thermal black; Conductive fibers such as carbon fiber and metal fiber; Conductive tubes such as carbon nanotubes; Metal powders such as fluorocarbon, aluminum and nickel powder; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

As the separator, a conventional porous polymer film conventionally used as a separator, such as a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer The porous polymer film made of a polymer may be used alone or in a laminated form, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, polyethylene terephthalate fiber or the like may be used. no.

A method of manufacturing a pouch type secondary battery 10 according to an embodiment of the present invention includes the steps of: determining a venting part 700 on a sealing part 600 of the pouch type secondary battery 10 (step 1); Placing at least one of the upper pouch film 200 or the lower pouch film 300 on the portion to be the venting portion 700 determined in Step 1 (Step 2); And sealing the portion to be the sealing portion 600 (Step 3).

Hereinafter, a method of manufacturing a pouch type secondary battery according to the present invention will be described in detail.

In the method of manufacturing a pouch type secondary battery according to the present invention, step 1 is a step of determining a venting part on a sealing part of the pouch type secondary battery. In the pouch-type secondary battery, when gas is generated in the pouch-shaped secondary battery, the gas is discharged only in the venting portion in the sealing portion, so that the gas is discharged more quickly, thereby enhancing the stability.

Wherein the step of determining the venting part comprises the steps of: determining whether a venting part is to be opened when a certain level of internal pressure is reached; In order for the venting portion to be opened by the internal pressure, it is necessary to determine how many percent of the sealing portion should be used as a venting portion, how many venting portions are to be provided at which position, and the number of non- can do.

2 and 3, the venting part 700 includes a sealing part 600 including the electrode tab 400, which is a part of the electrode assembly 100, However, the present invention is not limited thereto.

In the method of manufacturing a pouch type secondary battery according to the present invention, step 2 is a step of placing a nonconductive material on at least one of the upper pouch film and the lower pouch film at the portion to be bent, determined in the step 1.

The step 2 may be performed by placing a nonconductive material on a portion to be bent, determined in the step 1, during at least one of the upper pouch film and the lower pouch film. For example, when at least one of the upper pouch film or the lower pouch film is sequentially laminated with the PET outer layer / the Nylon layer / the Al metal foil layer / the PP inner layer sequentially, Layer PP film, it is possible to apply a nonconductive material only to the portion to be bent, which is determined in Step 1, particularly in the PP film to be extruded, when the PP film is produced singly before the pouch film of the layer.

Alternatively, the electrode assembly may be positioned on at least one of the upper pouch film or the lower pouch film, and then the nonconductive material may be positioned on the portion to be bent, as determined in the step 1. Specifically, in a manufacturing method of a pouch type secondary battery, a groove is formed in a portion to be accommodated in the upper pouch film (or the lower pouch film), and an electrode assembly is mounted in the groove, The nonconductive material may be applied to the portion to be bent as determined in the step 1 above.

In the method for manufacturing a pouch type secondary battery according to the present invention, step 3 is a step of sealing the portion to be sealed.

Step 3 is a step of covering the lower pouch film (upper pouch film) on the upper pouch film (or the lower pouch film) having the nonconductive material formed in the portion to be bent in step 2, sealing the part to be sealed Thereby forming a sealing portion. After the sealing part is formed, the pouch-shaped secondary battery can be manufactured by injecting an electrolyte into the housing part.

The electrolytic solution may include a non-aqueous organic solvent and a metal salt.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane , Acetonitrile, nitromethane, methyl formate, methyl acetate, triester phosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate Nonionic organic solvents such as tetrahydrofuran derivatives, ethers, methyl pyrophosphate, ethyl propionate and the like can be used.

LiBCl ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ , LiBF ₄ , LiBF ₄ , LiBF ₄ , LiBF ₄ , _{SO 3, LiCF 3 CO 2,} LiAsF 6, LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, 4-phenyl Lithium borate, imide and the like can be used.

According to another embodiment of the present invention, there is provided a battery module including the pouch type secondary battery as a unit cell and a battery pack including the same. Since the battery module and the battery pack include the secondary battery having excellent stability, the battery module and the battery pack can be used as a power source for a middle- or large-sized device selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, have.

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

≪ Example 1 > Production of pouch type secondary battery

Hereinafter, embodiments of the present invention will be described in more detail with reference to Figs. 1 and 2. Fig.

Step 1: Venting  decision

As shown in FIGS. 1 and 2, a part of the side of the sealing portion located on the opposite side of the portion where the electrode tab of the electrode assembly protrudes is set as a venting portion. The venting portion was set to 16% with respect to the area of the sealing portion so as to be opened by an internal pressure of 0.5 N / mm ² , and the nonconductive material was designed to have an area of 50% with respect to the venting portion.

Step 2: Nonconductivity  Application of material

An upper pouch film and a lower pouch film in which a PET outer layer / a Nylon layer / an Al metal foil layer / a PP inner layer were sequentially laminated were prepared. A groove was formed on a portion of the lower pouch film (PP inner layer) where the electrode assembly was to be accommodated, and a part of the electrode assembly was mounted on the groove. Thereafter, 3 g of nonconductive carbon powder containing non-conductive carbon particles having an average diameter (D50) of 1 mu m was applied to the portion to be bent as determined in step 1 above.

Step 3: Sealing  Produce

The upper pouch film having grooves formed on the lower pouch film formed in step 2 was covered with the upper pouch film. The upper pouch film was subjected to a thermal fusion process for 2 seconds in a heating jig at 180 ° C and a pressure of 0.3 Mpa, After the electrolyte solution was injected, a pouch-type secondary battery having a venting portion was manufactured.

(Example 2) Preparation of a sealing part test piece having a venting part (see Fig. 6)

Al metallic foil having a width of 150 mm and a length of 266 mm formed with a polypropylene (PP) coating layer was prepared as a pouch film. On the coating layer of the Al metal foil on which the polypropylene coating layer was formed, nonconductive carbon powder (average diameter (D50) 1 mu m) was applied to an area of 150 mm in width and 7 mm in length in an area of 70%.

The pouch film coated with the nonconductive carbon powder was folded in half so as to cover the nonconductive carbon powder, and then the portion where the nonconductive carbon powder was located was thermally fused in a heating jig at 180 DEG C under a pressure of 0.3 MPa for 2 seconds, To form a formed sealing portion.

The specimen was sampled at a width of 15 mm and a length of 66.5 mm to prepare a sealing part specimen having a bent portion having a width of 15 mm and a length of 7 mm.

≪ Example 3 > Preparation of sealing part specimen having venting part

 A sealing part specimen having a venting portion was prepared in the same manner as in Preparation Example 1, except that the nonconductive carbon powder of Preparation Example 1 was applied to the venting portion at 30%.

≪ Comparative Example 1 >

 A sealing part specimen was produced in the same manner as in Preparation Example 1, except that the nonconductive carbon powder was not applied in the above Production Example 1.

<Experimental Example 1> Measurement of sealing strength

The sealing test specimens prepared in Examples 2 and 3 and Comparative Example 1 were measured for sealing strength with UTM (universal test machine) under conditions of 25 ° C. and relative humidity of 50% Graphs and photographs.

As shown in Fig. 4, the specimen prepared in Example 2 had a maximum strength of 42 N / 15 mm (0.4 N / mm ² ) at 14 to 15 mm points on the graph (within half a point (3.5 mm) And the specimen prepared in Example 3 showed a maximum strength of 74 N / 15 mm (0.7 N / mm ² ) at 11-13 mm points on the graph (within half a point (3.5 mm) of the sealing portion).

On the other hand, in the case of Comparative Example 1 in which the venting portion was not formed, the maximum strength was 82 N / 15 mm (0.8 N / mm ² ).

On the other hand, the intensity per unit area (N / mm ² ) was calculated as the maximum strength / 15 mm x 7 mm (area of the sealing portion).

As a result, the internal pressure at which the bending occurred in the venting portions formed in Examples 2 and 3 was 0.4 N / mm &lt; ² &gt; And 0.7 N / mm &lt; ² &gt; And 0.8 N / mm &lt; ² &gt; in the sealing portion without venting portion It can be seen that the venting is caused by the internal pressure of the cylinder.

As described above, it can be seen that the pressure at which the venting occurs can be controlled by adjusting the amount of the nonconductive material applied to the venting portion as in Examples 2 and 3. [

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

10: Pouch type secondary battery
100: electrode assembly
200: upper pouch membrane
300: Lower pouch membrane
400: Electrode tab
500:
600: sealing part
610: outer line of the sealing part
620: inner line of the sealing part
700: Venting part
800: nonconductive material
810, 820: Outermost nonconductive material

Claims (17)

An electrode assembly, and an upper pouch film and a lower pouch film,
The pouch-type secondary battery includes a receiving part for receiving the electrode assembly between the upper pouch film and the lower pouch film, and a sealing part in which the upper pouch film and the lower pouch film are in close contact with each other,
Wherein at least a portion of the sealing portion includes a venting portion to induce gas discharge,
Wherein the venting portion includes a nonconductive material between the upper pouch film and the lower pouch film.
The method according to claim 1,
Wherein the nonconductive material is at least one selected from the group consisting of nonconductive carbon, oil, and nanoceramic particles.
The method according to claim 1,
Wherein the nonconductive material is spherical.
The method according to claim 1,
Wherein the nonconductive material has a spherical shape having an average diameter (D50) of 0.1 占 퐉 to 1 占 퐉.
The method according to claim 1,
Wherein an area of the venting portion is 20% to 50% with respect to an area of the sealing portion.
The method according to claim 1,
Wherein the nonconductive material is included in an area of 30% to 70% of the total area of the upper and lower pouch films of the venting portion.
The method according to claim 1,
When the nonconductive material is included in an area of 30% to 70% of the total area of the upper and lower pouch films of the venting part,
Wherein an inner pressure at which bending of the pouch type secondary battery occurs is 0.4 N / mm ² to 0.7 N / mm ² .
The method according to claim 1,
Wherein at least one of the upper pouch film and the lower pouch film comprises a PET outer layer / a Nylon layer / an Al metal foil layer / a PP inner layer sequentially laminated successively.
9. The method of claim 8,
Wherein the nonconductive material is present on the surface of the PP inner layer.
Determining a venting part on the sealing part of the pouch type secondary battery (step 1);
Placing at least one of the upper pouch film or the lower pouch film on the portion to be vented determined in Step 1 (Step 2); And
And sealing the portion to be sealed (Step 3).
11. The method of claim 10,
Wherein the step 2 is performed by placing a nonconductive material on a portion to be bent, which is determined in the step 1, during at least one of the manufacturing process of the upper pouch film or the lower pouch film.
12. The method of claim 11,
Wherein at least one of the upper pouch film and the lower pouch film comprises a PET outer layer, a Nylon layer, an Al metal foil layer, and a PP inner layer sequentially laminated successively.
13. The method of claim 12,
Wherein the step (2) is carried out by placing a nonconductive material on a portion to be bent, which is determined in the step (1), when the PP inner layer is prepared.
11. The method of claim 10,
Wherein the step 2 is performed by placing the electrode assembly in at least one of the upper pouch film or the lower pouch film and then placing the nonconductive material in the portion to be bent, Gt;
A battery module comprising the pouch type secondary battery of claim 1 as a unit cell.
A battery pack comprising the battery module of claim 15 and used as a power source for a middle- or large-sized device.
17. The method of claim 16,
Wherein the middle- or large-sized device is selected from the group consisting of an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle and a system for power storage.

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