Pouch-type secondary battery and its manufacturing method

Abstract

The present invention relates to a pouch-type secondary battery and a manufacturing method thereof, comprising an electrode assembly, an electrode lead extended from an electrode tab of the electrode assembly, an upper pouch covering an upper surface of the electrode assembly and the electrode lead, and a lower pouch covering a lower surface of the electrode assembly and the electrode lead, wherein the upper pouch and the lower pouch include a sealing area with a sealed edge, and the average thickness of the sealed area of ​​the upper pouch and the average thickness of the sealed area of ​​the lower pouch are equal to each other, while the average thickness of the unsealed area of ​​the upper pouch is smaller than the average thickness of the unsealed area of ​​the lower pouch, so that even if the thickness of the lower pouch is reduced during a sealing process by heat fusion, there is almost no thickness deviation between the upper pouch and the lower pouch in the sealed area after the sealing process, and the pouches can be formed uniformly.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0005802 filed on January 14, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a pouch-type secondary battery and a manufacturing method thereof, and relates to a pouch-type secondary battery and a manufacturing method thereof, in which an upper pouch and a lower pouch having different thicknesses are introduced and there is almost no deviation in average thickness between the lower pouch and the upper pouch in a sealed area after the upper pouch and the lower pouch undergo a heat-sealing sealing process. [Background technology]

[0003] As technological development and demand for mobile devices increases, and the demand for secondary batteries as an alternative energy source to fossil fuels is also increasing rapidly, a great deal of research is being conducted into secondary batteries that can meet various requirements.

[0004] In terms of the shape of the battery case, secondary batteries are typically classified into cylindrical batteries and prismatic batteries in which the electrode assembly is housed in a cylindrical or prismatic metal case, respectively, and pouch batteries in which the electrode assembly is housed in a pouch case made of an aluminum laminate sheet. In terms of materials, there is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries, which are excellent in terms of high energy density, discharge voltage, and output stability.

[0005] Among these, pouch-type batteries are in high demand due to their advantages of being thin, easy to stack, and the ability to change shape. Pouch-type batteries are constructed with an electrode assembly and electrolyte contained in a pouch-shaped laminate sheet that can house the electrode assembly, and the resin layer of the laminate sheet can be fused by heat.

[0006] Pouch-type batteries are heat-sealed by applying heat and pressure to laminate sheets that are stacked vertically around the periphery of a battery case to prevent the electrode assembly from being exposed to the outside and electrolyte leakage. Electrode leads protrude from the outside of the battery case of a pouch-type battery, and a lead film is attached to the surface of the electrode leads. The lead film made of an insulating resin material is heat-sealed together with the laminate sheet, i.e., the pouch, to more firmly seal the periphery of the electrode leads.

[0007] However, when the pouch is heat-sealed, a pair of upper and lower pouches enclosing the electrode assembly and the electrode lead often have a difference in thickness after heat sealing. In order to seal the electrode lead and the pouch, a pair of upper and lower sealing blocks are used to apply heat and pressure, and in the sealing process, the lower sealing block rises to support the lower pouch and the electrode lead, and then the upper sealing block descends to apply heat and pressure. As a result, more heat is supplied to the lower pouch and the electrode lead, which makes the resin layer of the lower pouch thinner than that of the upper pouch.

[0008] When the thicknesses of the upper and lower pouches are asymmetrical, the lower pouch, which is relatively thinner, becomes more vulnerable to pressure. For example, when pressure below a specified endurance limit is applied to a pouch-type battery, the upper pouch may withstand the pressure but the lower pouch may burst, or the resin layer of the lower pouch may be stretched and broken by the internal pressure applied by gas generated in the pouch, causing the sealed portion to open. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the above problems, and has an object to provide a pouch-type secondary battery and a manufacturing method thereof, which introduces a battery case in which a lower pouch is thicker than an upper pouch, and in which the thicknesses of the upper and lower pouches in the sealed area can be uniform with almost no deviation after a heat sealing process. [Means for solving the problem]

[0010] The present invention relates to a pouch-type secondary battery. In one embodiment, the pouch-type secondary battery according to the present invention includes an electrode assembly, an electrode lead extended from an electrode tab of the electrode assembly, an upper pouch covering an upper surface of the electrode assembly and the electrode lead, and a lower pouch covering a lower surface of the electrode assembly and the electrode lead. The upper pouch and the lower pouch also include sealing regions where edges are sealed.

[0011] In a specific example, the average thickness of the sealing region of the upper pouch and the average thickness of the sealing region of the lower pouch satisfy the following formula 1:

[0012] [Formula 1] 0.95≦D 1 TOP / D 1 BOTTOM ≦1.05

[0013] In formula 1, D 1 TOP represents the average thickness of the sealing area of ​​the upper pouch, and D 1 BOTTOM represents the average thickness of the sealing area of ​​the lower pouch.

[0014] The average thickness of the unsealed area of ​​the upper pouch and the average thickness of the unsealed area of ​​the lower pouch satisfy the following formula 2.

[0015] [Formula 2] 0.65≦D 2 TOP / D 2 BOTTOM ≦0.95

[0016] In Equation 2, D 2 TOP represents the average thickness of the unsealed area of ​​the upper pouch, and D 2 BOTTOM represents the average thickness of the unsealed area of ​​the lower pouch.

[0017] The present invention is characterized in that the deviation between the average thickness of the sealing area of ​​the upper pouch and the average thickness of the sealing area of ​​the lower pouch is within 10% or within 5%, while the average thickness of the unsealed area of ​​the upper pouch is smaller than the average thickness of the unsealed area of ​​the lower pouch. In a specific example, the average thickness of the sealing area of ​​the upper pouch and the average thickness of the sealing area of ​​the lower pouch are at the same level.

[0018] The present invention also provides a method for manufacturing a pouch-type secondary battery, in one embodiment, the method for manufacturing a pouch-type secondary battery according to the present invention includes the steps of: preparing an electrode assembly, an electrode lead extended from an electrode tab of the electrode assembly, an upper pouch covering an upper surface of the electrode assembly and the electrode tab, and a lower pouch covering a lower surface of the electrode assembly and the electrode tab, and positioning the electrode lead and the electrode assembly between the upper pouch and the lower pouch, and applying pressure and heat to seal edges of the upper pouch and the lower pouch with a sealing device.

[0019] In a specific example, the average thickness of the sealing region of the upper pouch and the average thickness of the sealing region of the lower pouch satisfy the following formula 1:

[0020] [Formula 1] 0.95≦D 1 TOP / D 1 BOTTOM ≦1.05

[0021] In formula 1, D 1 TOP represents the average thickness of the sealing area of ​​the upper pouch, and D 1 BOTTOM represents the average thickness of the sealing area of ​​the lower pouch.

[0022] In addition, the average thickness of the unsealed area of ​​the upper pouch and the average thickness of the unsealed area of ​​the lower pouch satisfy the following formula 2.

[0023] [Formula 2] 0.65≦D 2 TOP / D 2 BOTTOM ≦0.95

[0024] In Equation 2, D 2 TOP represents the average thickness of the unsealed area of ​​the upper pouch, and D 2 BOTTOM represents the average thickness of the unsealed area of ​​the lower pouch.

[0025] The present invention is characterized in that the deviation between the average thickness of the sealed area of ​​the upper pouch and the average thickness of the sealed area of ​​the lower pouch is within 10% or within 5%, while the average thickness of the unsealed area of ​​the upper pouch is smaller than the average thickness of the unsealed area of ​​the lower pouch. Effect of the Invention

[0026] The pouch-type secondary battery of the present invention having the above-mentioned configuration may be formed uniformly with almost no thickness deviation between the upper and lower pouches in the sealed area after the sealing process, even if the thickness of the lower pouch is reduced during the heat sealing process, by introducing a battery case in which the lower pouch is thicker than the upper pouch.

[0027] As a result, in the pouch-type secondary battery of the present invention, the thickness of the lower pouch is formed relatively thinner than the upper pouch after a sealing process, making the lower pouch more vulnerable to pressure, and the internal pressure of the gas generated in the battery case causes the resin layer of the lower pouch to stretch and break, thereby opening the sealed portion, thereby effectively preventing the conventional problem and improving structural stability. [Brief description of the drawings]

[0028] [Figure 1] 1 is a diagram of a pouch-type secondary battery before being sealed by a sealing device. [Diagram 2]1 is a diagram of a pouch-type secondary battery sealed by a sealing device. [Diagram 3] 1 is a diagram illustrating an electrode lead, an upper pouch, and a lower pouch before being pressed and heated by a sealing device. [Figure 4] 1 is a diagram illustrating an upper pouch and a lower pouch surrounding an electrode lead after pressure and heat are applied in a sealing device. [Diagram 5] 3 is a partially enlarged view of the "XX" cross section of FIG. 2. [Figure 6] This is an enlarged partial view of "Y" and "Z" in Figure 5. [Figure 7] 11 is a partially enlarged view of an upper pouch and a lower pouch according to another embodiment of the present invention. [Figure 8] 11 is a partially enlarged view of an upper pouch and a lower pouch according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Since the present invention can be modified in various ways and can have various embodiments, specific embodiments will be described in detail below.

[0030] However, this is not intended to limit the invention to the particular embodiments, but should be understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0031] In the present invention, the terms "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but should be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0032] In addition, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion in between. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion in between. In addition, in the present application, being "on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0033] The present invention relates to a pouch-type secondary battery. In one embodiment, the pouch-type secondary battery according to the present invention includes an electrode assembly, an electrode lead extending from an electrode tab of the electrode assembly, an upper pouch covering an upper surface of the electrode assembly and the electrode lead, and a lower pouch covering a lower surface of the electrode assembly and the electrode lead. The upper pouch and the lower pouch also include sealing regions where edges are sealed.

[0034] In a specific example, the average thickness of the sealing region of the upper pouch and the average thickness of the sealing region of the lower pouch satisfy the following formula 1:

[0035] [Formula 1] 0.95≦D 1 TOP / D 1 BOTTOM ≦1.05

[0036] In formula 1, D 1 TOP represents the average thickness of the sealing area of ​​the upper pouch, and D 1 BOTTOM represents the average thickness of the sealing area of ​​the lower pouch.

[0037] The numerical value of the above formula 1 is in the range of 0.95 to 1.05, specifically in the range of 0.95 to 1.

[0038] The average thickness of the unsealed area of ​​the upper pouch and the average thickness of the unsealed area of ​​the lower pouch satisfy the following formula 2.

[0039] [Formula 2] 0.65≦D 2 TOP / D 2 BOTTOM ≦0.95

[0040] In Equation 2, D 2 TOP represents the average thickness of the unsealed area of ​​the upper pouch, and D 2 BOTTOM represents the average thickness of the unsealed area of ​​the lower pouch.

[0041] The numerical value relating to the above formula 2 is in the range of 0.65 to 0.95, specifically in the range of 0.75 to 0.85.

[0042] The present invention is characterized in that the deviation between the average thickness of the sealing area of ​​the upper pouch and the average thickness of the sealing area of ​​the lower pouch is within 10% or within 5%, while the average thickness of the unsealed area of ​​the upper pouch is smaller than the average thickness of the unsealed area of ​​the lower pouch. In a specific example, the average thickness of the sealing area of ​​the upper pouch and the average thickness of the sealing area of ​​the lower pouch are at the same level.

[0043] Here, the average thickness (D 2 TOP For example, the average thickness (D 2 TOP The average thickness (D) of the unsealed area of ​​the lower pouch is in the range of 150 to 160 μm. 2 BOTTOM ) is in the range of 175 to 200 μm. For example, the average thickness (D 2 BOTTOM ) is in the range of 180 to 190 μm.

[0044] In another specific example, the upper pouch and the lower pouch each have a three-layer structure including a metal thin film layer, a first resin layer formed on the inside facing the electrode assembly or electrode lead relative to the metal thin film layer, and a second resin layer formed on the outside of the metal thin film layer.

[0045] Here, the deviation between the average thickness of the metal thin film layer and the second resin layer in the unsealed area of ​​the upper pouch and the average thickness of the metal thin film layer and the second resin layer in the unsealed area of ​​the lower pouch may be 5% or less, while the average thickness of the first resin layer in the unsealed area of ​​the upper pouch may be smaller than the average thickness of the first resin layer in the unsealed area of ​​the lower pouch.

[0046] In a specific example, the average thickness of the first resin layer in the unsealed area of ​​the upper pouch and the average thickness of the first resin layer in the unsealed area of ​​the lower pouch satisfy the following formula 3.

[0047] [Formula 3] 0.55≦D 3 TOP / D 3 BOTTOM ≦0.85

[0048] In Equation 3, D 3 TOP represents the average thickness of the first resin layer in the unsealed area of ​​the upper pouch, and D 3 BOTTOM represents the average thickness of the first resin layer in the unsealed area of ​​the lower pouch.

[0049] Here, the average thickness (D 3 TOP ) is in the range of 70 to 85 μm, and the average thickness (D 3 BOTTOM ) can be in the range of 100 to 125 μm.

[0050] The first resin layer may be made of polypropylene (PP) resin, and the second resin layer may contain polyethylene terephthalate (PET) resin.

[0051] Here, the average thickness of the sealed area of ​​the upper pouch and the sealed area of ​​the lower pouch may be mainly affected by the thickness of the first resin layer.

[0052] Meanwhile, in another embodiment of the present invention, the elongation ratio of the first resin layer of the lower pouch may be smaller than the elongation ratio of the first resin layer of the upper pouch.

[0053] In another embodiment of the present invention, the thermal conductivity of the metal thin film layer of the lower pouch may be greater than that of the metal thin film layer of the upper pouch.

[0054] The present invention also provides a method for manufacturing a pouch-type secondary battery, in one embodiment, the method for manufacturing a pouch-type secondary battery according to the present invention includes the steps of: preparing an electrode assembly, an electrode lead extended from an electrode tab of the electrode assembly, an upper pouch covering an upper surface of the electrode assembly and the electrode tab, and a lower pouch covering a lower surface of the electrode assembly and the electrode tab, and positioning the electrode lead and the electrode assembly between the upper pouch and the lower pouch, and applying pressure and heat to seal edges of the upper pouch and the lower pouch with a sealing device.

[0055] In a specific example, the average thickness of the sealing region of the upper pouch and the average thickness of the sealing region of the lower pouch satisfy the following formula 1:

[0056] [Formula 1] 0.95≦D 1 TOP / D 1 BOTTOM ≦1.05

[0057] In formula 1, D 1 TOP represents the average thickness of the sealing area of ​​the upper pouch, and D 1BOTTOM represents the average thickness of the sealing area of ​​the lower pouch.

[0058] In addition, the average thickness of the unsealed area of ​​the upper pouch and the average thickness of the unsealed area of ​​the lower pouch satisfy the following formula 2.

[0059] [Formula 2] 0.65≦D 2 TOP / D 2 BOTTOM ≦0.95

[0060] In Equation 2, D 2 TOP represents the average thickness of the unsealed area of ​​the upper pouch, and D 2 BOTTOM represents the average thickness of the unsealed area of ​​the lower pouch.

[0061] The present invention is characterized in that the deviation between the average thickness of the sealed area of ​​the upper pouch and the average thickness of the sealed area of ​​the lower pouch is within 10% or within 5%, while the average thickness of the unsealed area of ​​the upper pouch is smaller than the average thickness of the unsealed area of ​​the lower pouch.

[0062] In another example, the upper pouch and the lower pouch in the preparation stage each include a metal thin film layer, a first resin layer formed on the inside of the metal thin film layer facing the electrode lead or electrode assembly, and a second resin layer formed on the outside of the metal thin film layer, and the deviation between the average thickness of the metal thin film layer and the second resin layer in the unsealed area of ​​the upper pouch and the average thickness of the metal thin film layer and the second resin layer in the unsealed area of ​​the lower pouch is 5% or less, while the average thickness of the first resin layer of the upper pouch is smaller than the average thickness of the first resin layer of the lower pouch.

[0063] Here, the average thickness of the first resin layer in the unsealed area of ​​the upper pouch and the average thickness of the first resin layer in the unsealed area of ​​the lower pouch may be characterized by satisfying the following formula 3.

[0064] [Formula 3] 0.55≦D 3 TOP / D 3 BOTTOM ≦0.85

[0065] In Equation 3, D 3 TOP represents the average thickness of the first resin layer in the unsealed area of ​​the upper pouch, and D 3 BOTTOM represents the average thickness of the first resin layer in the unsealed area of ​​the lower pouch.

[0066] The sealing device may include an upper sealing block having a two-stage upper sealing groove formed therein, the two-stage upper sealing groove including a first upper step forming a bottom surface and a second upper step formed between a surface of the upper sealing block and the first upper step, and a lower sealing block having a two-stage lower sealing groove formed therein, the two-stage lower sealing groove including a first lower step forming a bottom surface and a second lower step formed between a surface of the lower sealing block and the first lower step, and heights of the first upper step and the second upper step of the upper sealing block are smaller than heights of the first lower step and the second lower step of the lower sealing block.

[0067] The present invention relates to a pouch-type secondary battery, and more particularly to a pouch-type secondary battery in which a battery case having a lower pouch thicker than an upper pouch is introduced, and the thicknesses of the upper and lower pouches can be uniform with little deviation after a heat sealing process.

[0068] According to one example for achieving this object, the present invention includes an electrode assembly, an electrode lead extended from an electrode tab of the electrode assembly, an upper pouch covering an upper surface of the electrode assembly and the electrode lead, and a lower pouch covering a lower surface of the electrode assembly and the electrode lead, the upper pouch and the lower pouch including a sealing area with a sealed edge, and the average thickness of the sealing area of ​​the upper pouch and the average thickness of the sealing area of ​​the lower pouch are at the same level, while the average thickness of the unsealed area of ​​the upper pouch is smaller than the average thickness of the unsealed area of ​​the lower pouch. In a specific example, the deviation between the average thickness of the sealing area of ​​the upper pouch and the average thickness of the sealing area of ​​the lower pouch is within 10% or within 5%, in the range of 0.01 to 10%, or in the range of 0.1 to 5%.

[0069] By applying a battery case in which the thickness of the lower pouch is asymmetrically thicker than that of the upper pouch, even if the thickness of the lower pouch that first comes into contact with the lower sealing block becomes thinner when the lower sealing block of the sealing device rises to support the lower pouch and the electrode lead during the sealing process and then the upper sealing block descends to apply heat and pressure, there is almost no thickness deviation between the upper pouch and the lower pouch after the sealing process, and the thickness imbalance of the sealing areas of the upper pouch and the lower pouch can be eliminated. This improves the conventional problem that the sealing part of the lower pouch opens because the thinner lower pouch cannot withstand the internal pressure.

[0070] Hereinafter, specific examples of the present invention will be described in detail with reference to the accompanying drawings.

[0071] (First embodiment) The present invention provides, as a first embodiment, a pouch-type secondary battery in which a lower pouch having a thickness greater than that of an upper pouch is used, and the upper pouch and the lower pouch in a sealed area after a sealing process have the same thickness.

[0072] <Pouch-type secondary battery> FIG. 1 is a diagram of a pouch-type secondary battery before being sealed by a sealing device, and FIG. 2 is a diagram of the pouch-type secondary battery after being sealed by the sealing device.

[0073] 1 and 2, in the pouch-type secondary battery 10, an upper pouch 100 and a lower pouch 100' are disposed above and below the electrode assembly 300 electrically connected to the electrode tab 420 and the electrode lead 400 extended from the electrode tab 420 and wrapped in a lead film 410, respectively, and the electrode lead 400 is protruded to the outside with the electrode assembly 300 housed between the upper pouch 100 and the lower pouch 100', and the edges of the upper pouch 100 and the lower pouch 100' are sealed. At this time, the upper pouch 100 and the lower pouch 100' include areas 101, 101' sealed by heat-sealing the edges of each pouch by a sealing device 500, and unsealed areas 102, 102'.

[0074] The pouch-type secondary battery 10 has a structure in which the electrode assembly 300 and an electrolyte are embedded in a pouch-shaped laminate sheet capable of storing the electrode assembly 300. To prevent the electrode assembly 300 from being exposed to the outside and to prevent leakage of the electrolyte, heat and pressure are applied to the upper pouch 100 and the lower pouch 100' containing the laminate sheet to perform a heat fusion process for sealing them.

[0075] FIG. 3 illustrates the electrode lead, upper pouch, and lower pouch before pressure and heat are applied with a sealing device, and FIG. 4 illustrates the upper pouch and lower pouch surrounding the electrode lead after pressure and heat are applied with a sealing device.

[0076] Referring to FIG. 3, the sealing device 500 according to an embodiment includes an upper sealing block 510 and a lower sealing block 520 for applying pressure and heat in both directions to a laminated structure in which the upper pouch 100 and the lower pouch 100' are disposed on the upper and lower parts of the electrode lead 400, respectively. The upper sealing block 510 includes a two-stage upper sealing groove 513 including a first upper step 511 forming a bottom surface and a second upper step 512 formed between the surface of the upper sealing block 510 and the first upper step 511. Here, the bottom surface and the surface surface are based on the direction in which the upper sealing groove 513 is viewed from the inside, and the bottom surface refers to the lowest surface of the upper sealing groove 513, and the surface surface refers to the highest surface. In this way, the upper sealing groove 513 forms two steps with respect to the upper sealing block 510. The lower sealing block 520 also includes a similar lower sealing groove 523. The lower sealing groove 523 has two steps including a first lower step 521 forming a bottom surface and a second lower step 522 formed between the surface of the lower sealing block 520 and the first lower step 521 .

[0077] As described above, in the sealing process of the pouch type secondary battery 10, the lower sealing block 520 rises to support the lower pouch 100' and the electrode lead 400, and then the upper sealing block 510 descends to apply heat and pressure. In this manner, since the lower sealing block 520 applies more heat by contacting the lower pouch 100' first, the sealing process of the pouch type secondary battery 10 essentially applies more heat to the lower pouch 100'. That is, the lower pouch 100' to which more heat is supplied stretches more than the upper pouch 100. For this reason, the sealing region 101' of the lower pouch is asymmetrical and has a thinner thickness than the sealing region 101 of the upper pouch.

[0078] In the present invention, in order to alleviate or correct such an essential asymmetric phenomenon, the thickness of the lower pouch 100' before the sealing process is intentionally set to be thicker than the thickness of the upper pouch 100. Meanwhile, the thicknesses of the upper pouch 100 and the lower pouch 100' before the sealing process can be considered to be equivalent to the thicknesses of the upper pouch 100 and the lower pouch 100' in the unsealed areas after the sealing process, respectively.

[0079] 4, the first upper step 511 of the upper sealing block 510 corresponds to the upper part of the electrode lead 400, while the second upper step 512 corresponds to the upper part of the lead film 410. Also, the first lower step 521 of the lower sealing block 520 corresponds to the lower part of the electrode lead 400, while the second lower step 522 corresponds to the lower part of the lead film 410. Since the electrode lead 400 is located inside the first upper step 511 and the first lower step 521, the boundary surfaces of the electrode lead 400, the upper pouch 100, and the lower pouch 100' are tightly adhered to each other. At this time, the sealing area 101 of the upper pouch and the sealing area 101' of the lower pouch adhered to the electrode lead 400 form a uniform thickness with almost no deviation in average thickness.

[0080] This is to solve the conventional problem that the lower pouch 100' is more vulnerable to pressure due to the thickness of the lower pouch 100 being relatively thinner than the upper pouch 100 after the sealing process, and the lower pouch 100' is ruptured due to the internal pressure of the gas generated inside the pouch-type battery case, thereby opening the sealed area of ​​the lower pouch. In this way, the thickness of the lower pouch 100' is made thicker than the thickness of the upper pouch 100 before the sealing process, so that after sealing, there is almost no deviation in the average thickness of the sealed area 101 of the upper pouch and the sealed area 101' of the lower pouch, thereby forming a uniform thickness.

[0081] In this case, the average thickness of the sealed area 101 of the upper pouch and the average thickness of the sealed area 101' of the lower pouch may be characterized as satisfying the following formula 1, and the average thickness of the unsealed area 102 of the upper pouch and the average thickness of the unsealed area 102' of the lower pouch may be characterized as satisfying the following formula 2.

[0082] [Formula 1] 0.95≦D 1 TOP / D 1 BOTTOM ≦1.05

[0083] In formula 1, D 1 TOP represents the average thickness of the sealing area 101 of the upper pouch, and D 1 BOTTOM represents the average thickness of the sealing area 101' of the lower pouch.

[0084] [Formula 2] 0.65≦D 2 TOP / D 2 BOTTOM ≦0.95

[0085] In Equation 2, D 2 TOP represents the average thickness of the unsealed area 102 of the upper pouch, and D 2 BOTTOM represents the average thickness of the unsealed area 102' of the lower pouch.

[0086] Here, the sealing area 101 of the upper pouch and the sealing area 101' of the lower pouch refer to the areas that are heated and pressurized by the sealing device 500. At this time, the average thickness (D 1 TOP ) and the average thickness of the sealing area 101' of the lower pouch (D 1 BOTTOM ) is the average thickness of the area heated and pressed by the sealing device 500, with a margin of error of about 5% or less. 1 TOP / D 1BOTTOM The closer the value is to the integer 1, the more equivalent the thickness is. If the value is less than 0.95 or greater than 1.05, the average thickness (D 1 TOP ) and the average thickness of the sealing area 101' of the lower pouch (D 1 BOTTOM ) do not form equivalent levels, making it difficult to achieve the desired effect.

[0087] In addition, the unsealed area 102 of the upper pouch and the unsealed area 102' of the lower pouch refer to areas that are not heated or pressurized by the sealing device 500, and the average thickness (D 2 TOP ) and the average thickness (D 2 BOTTOM ) is the average thickness of the area not heated or pressed by the sealing device 500, which is also the average thickness of the initial upper and lower pouches before the sealing process. 2 TOP / D 2 BOTTOM " range is less than 0.65, the average thickness (D 2 BOTTOM ) is the average thickness (D 2 TOP ), the internal pressure generated inside the battery case after the sealing process is concentrated in the unsealed area 102 of the upper pouch, which may cause an imbalance in the internal pressure. On the other hand, if it exceeds 0.95, the average thickness (D 1 BOTTOM ) and the average thickness of the sealing area 101 of the upper pouch (D 1 TOP) is not formed at an equal level (average thickness error range of 5% or less), making it difficult to achieve the intended purpose. In other words, when the upper pouch 100 and the lower pouch 100' having a thickness in the range described in the above formula 2 are used for sealing, the upper pouch 100 and the lower pouch 100' in the sealed area after the sealing process can be formed at an equal level of thickness with almost no deviation in average thickness.

[0088] However, the "D 1 TOP / D 1 BOTTOM " and "D" in the above formula 2 2 TOP / D 2 BOTTOM The range of " is not limited to the range described above, and can be suitably selected taking into consideration the materials of the upper pouch 100 and the lower pouch 100', the heating temperature and heating time of the sealing device 500, the thickness of the electrode assembly 300, etc.

[0089] More specifically, one embodiment of the present invention is a method for manufacturing a pouch having an average thickness (D 2 TOP ) is in the range of 130 to 165 μm, and the average thickness (D 2 BOTTOM ) may be formed in the range of 175 to 200 μm. This may also be suitably selected in consideration of the materials of the upper pouch 100 and the lower pouch 100′, the heating temperature and heating time of the sealing device 500, the thickness of the electrode assembly 300, etc.

[0090] 3, in the illustrated embodiment, in particular, the height A of the first upper step of the upper sealing block 510 is configured to be smaller than the height A' of the first lower step of the lower sealing block 520, and the height B of the second upper step of the upper sealing block 510 is also configured to be smaller than the height B' of the second lower step of the lower sealing block 520. In other words, the first lower step 521 and the second lower step 522 of the lower sealing block 520 are deeper than the first upper step 511 and the second upper step 512 of the upper sealing block 510.

[0091] In this manner, by making the first lower step 521 and the second lower step 522 of the lower sealing block 520 relatively deep, when the lower pouch 100', which is thicker than the upper pouch 100, is molded under heat and pressure, a marginal space is secured in which the thickness of the lower pouch 100' can be maintained at a greater thickness. In addition, even if the heating temperatures of the upper sealing block 510 and the lower sealing block 520 are the same, the amount of heat transfer can be reduced due to the reduced pressure, thereby eliminating the conventional imbalance problem in which more heat was supplied to the lower pouch 100'.

[0092] Second embodiment The present invention provides, as a second embodiment, a pouch-type secondary battery in which a lower pouch having a thickness greater than that of an upper pouch is used, and the upper pouch and the lower pouch in the sealed area after a sealing process have the same thickness.

[0093] <Pouch-type secondary battery> FIG. 5 is a partially enlarged view of the "XX" cross section of FIG. 2, and FIGS. 6(a) and 6(b) are partially enlarged views of "Y" and "Z" in FIG. 5, respectively.

[0094] Referring to FIG. 5, in one example, the upper pouch 100 and the lower pouch 100' may each have a three-layer structure including a metal thin film layer 120, 120', a first resin layer 110, 110' formed on the inside of the metal thin film layer 120, 120' facing the electrode assembly 300 or the electrode lead 400, and a second resin layer 130, 130' formed on the outside of the metal thin film layer 120, 120'. The first resin layer 110, 110' is a polypropylene (PP) resin, and the second resin layer 130, 130' includes a polyethylene terephthalate (PET) resin. Here, the first resin layer 110, 110' may further include PPa (Acid modified polypropylene), and PPa may mean a material having a structure in which maleic acid is grafted to polypropylene (PP). Furthermore, the second resin layer may further include nylon (orinted nylon).

[0095] The first resin layers 110, 110' are resin layers that come into contact with the electrode lead 400 coated with the lead film 410, and due to strong fusion between the upper pouch 100 and the lower pouch 100' and the electrode lead 400, or between the upper pouch 100 and the lower pouch 100', the first resin layers 110, 110' have a lower melting point than the second resin layers 130, 130'. For example, polypropylene (PP) resin has a melting point that is about 100° C. lower than polyethylene terephthalate (PET) resin.

[0096] In a specific example, the deviation between the average thickness D of the metal thin film layer 120 and the average thickness E of the second resin layer 130 in the unsealed area of ​​the upper pouch and the average thickness D' of the metal thin film layer 120' and the average thickness E' of the second resin layer 130' in the unsealed area of ​​the lower pouch is 5% or less, and the average thickness C of the first resin layer 110 in the unsealed area of ​​the upper pouch is smaller than the average thickness C' of the first resin layer 110' in the unsealed area of ​​the lower pouch (see FIG. 6). This is because the average thicknesses of the sealing area 101 of the upper pouch and the sealing area 101' of the lower pouch are mainly affected by the thicknesses C, C' of the first resin layer (i.e., the thickness of the first resin layer changes most significantly before and after molding due to the sealing device), and the thickness of the entire pouch can be easily controlled by controlling only the thicknesses C, C' of the first resin layer.

[0097] More specifically, in the present invention, the average thickness C of the first resin layer 110 in the unsealed area 102 of the upper pouch and the average thickness C' of the first resin layer 110' in the unsealed area 102' of the lower pouch may satisfy the following formula 3.

[0098] [Formula 3] 0.55≦D 3 TOP / D 3 BOTTOM ≦0.85

[0099] In Equation 3, D 3 TOP represents the average thickness of the first resin layer 110 in the unsealed area 102 of the upper pouch, and D 3 BOTTOM represents the average thickness of the first resin layer 110' in the unsealed area 102' of the lower pouch.

[0100] Under the premise that the average thickness of the sealed area 101 of the upper pouch and the sealed area 101' of the lower pouch is mainly affected by the thicknesses C and C' of the first resin layer, 3 TOP / D 3 BOTTOMWhen the range of " is less than 0.55, the average thickness (D 3 BOTTOM ) is the average thickness (D 3 TOP ), it may cause an imbalance in the internal pressure generated inside the battery case, and the sealing area 101 of the upper pouch after the sealing process may not be able to withstand the internal pressure. On the other hand, if it exceeds 0.85, the average thickness (D 1 BOTTOM ) and the average thickness of the sealing area 101 of the upper pouch (D 1 TOP ) is not formed to the same level (average thickness error range 5% or less), making it difficult to achieve the intended purpose. 3 TOP / D 3 BOTTOM The range of " is not limited to the described range, and can be suitably selected in consideration of the components of the first resin layers 110, 110', the heating temperature and time of the sealing device 500, the thickness of the electrode assembly 300, and the like.

[0101] In particular, the average thickness (D 3 TOP ) is in the range of 70 to 85 μm, and the average thickness (D 3 BOTTOM ) may be in the range of 100 to 125 μm. This may also be suitably selected in consideration of the components of the first resin layer 110 of the upper pouch and the first resin layer 110′ of the lower pouch, the heating temperature and heating time of the sealing device 500, the thickness of the electrode assembly 300, etc.

[0102] Fig. 6(a) is an enlarged view of "Y" in Fig. 5, and Fig. 6(b) is an enlarged view of "Z" in Fig. 5. In one example, the first resin layer 110 of the upper pouch and the first resin layer 110' of the lower pouch may include PP layers 110a, 110a' and PPa layers 110b, 110b', and the second resin layer may include PET layers 130b, 130b', adhesive layers 140, 140', and nylon layers 130a, 130a'. Specifically, based on PP layers 110a, 110a' of first resin layers 110, 110' formed on the inner side facing electrode assembly 300 or electrode lead 400, PPa layers 110b, 110b', metal thin film layers 120, 120', nylon layers 130a, 130a', and PET layers 130b, 130b' may be laminated in this order, and adhesive layers 140, 140' may be formed between metal thin film layers 120, 120' and nylon layers 130a, 130a', and adhesive layers 140, 140' may also be formed between nylon layers 130a, 130a' and PET layers 130b, 130b'.

[0103] The thickness of the unsealed region 102 of the upper pouch is smaller than the thickness of the unsealed region 102' of the lower pouch. At this time, the thickness E of the second resin layer 130 of the upper pouch and the thickness D of the metal thin film layer 120 are the same as the thickness E' of the second resin layer 130' of the lower pouch and the thickness D' of the metal thin film layer 120', respectively, but the thickness C' of the first resin layer 110' of the lower pouch is thicker than the thickness C of the first resin layer 110 of the upper pouch. This is because, as described above, the average thickness of the sealed region 101 of the upper pouch and the sealed region 101' of the lower pouch are mainly affected by the thicknesses C and C' of the first resin layers 110 and 110', respectively.

[0104] In one example, the thickness of the unsealed area 102 of the upper pouch may be 153 μm, and the thickness of the unsealed area 102' of the lower pouch may be 183 μm. Specifically, the thickness C of the first resin layer of the unsealed area 102 of the upper pouch may be 80 μm, the thickness D of the metal thin film layer may be 40 μm, and the thickness E of the second resin layer including the adhesive layer may be 33 μm. Meanwhile, the thickness C' of the first resin layer of the unsealed area 102' of the lower pouch may be 110 μm, and the thicknesses of the metal thin film layer and the second resin layer may be the same as the thickness E of the metal thin film layer D and the second resin layer of the unsealed area 102 of the upper pouch. This is merely one example, and may be suitably changed according to the purpose.

[0105] Third embodiment The present invention provides, as a third embodiment, a pouch-type secondary battery in which a lower pouch having a thickness greater than that of an upper pouch is used, and the upper pouch and the lower pouch in the sealed area after a sealing process have the same thickness.

[0106] <Pouch-type secondary battery> In the first embodiment described above, the average thickness of the unsealed area 102 of the upper pouch is set to be smaller than the average thickness of the unsealed area 102' of the lower pouch, thereby eliminating the imbalance in average thickness between the sealed area 101 of the upper pouch and the sealed area 101' of the lower pouch, even if more heat is supplied to the lower pouch 100'.

[0107] The third embodiment basically relates to another embodiment for solving the thermal imbalance more effectively while maintaining the first embodiment.

[0108] 7(a) and 7(b) are partial enlarged views of an upper pouch and a lower pouch according to another embodiment of the present invention, respectively. As shown in FIG. 7, the first resin layer 110 of the upper pouch and the first resin layer 110' of the lower pouch have different elongation rates, specifically, the elongation rate of the first resin layer 110' of the lower pouch is smaller than the elongation rate of the first resin layer 110 of the upper pouch. This is because the elongation rate of the first resin layer 110' of the lower pouch is smaller than the elongation rate of the first resin layer 110 of the upper pouch, so that even when heat and pressure are applied by the sealing device 500, the amount of change in thickness of the lower pouch 100' can be reduced.

[0109] As an example, in order to reduce the elongation rate of the first resin layer 110' of the lower pouch, the first resin layer 110 may be a silylated first resin layer 150. The silylated first resin layer 150 may include a silane compound capable of forming a silane cross-linked polypropylene resin through silylation with polypropylene (PP). The vinyl group of the silane compound reacts with a radical portion of the polypropylene resin to perform grafting of the polypropylene (PP) resin.

[0110] When the first resin layer 110' contains a silane compound, a cross-linked structure is formed by chemical bonding with the polypropylene (PP) of the first resin layer 110', and the melt strength of the polypropylene (PP) is increased, improving the viscoelasticity at high temperatures and at the same time increasing the mechanical strength. In other words, the elongation rate can be reduced.

[0111] The silane compound may be one or more selected from the group consisting of vinyl silane, vinyl methoxy silane, vinyl dimethoxy silane, vinyl trimethoxy silane, vinyl ethoxy silane, vinyl diethoxy silane, vinyl triethoxy silane, vinyl propoxy silane, vinyl dipropoxy silane, and vinyl tripropoxy silane, and more preferably may be one or more of vinyl silane, vinyl methoxy silane, vinyl dimethoxy silane, and vinyl trimethoxy silane.

[0112] In addition, a crosslinking accelerator may be further included to promote partial crosslinking between polypropylene (PP) resins that have formed silane crosslinks. As the crosslinking accelerator, an organotin compound may be used, and preferably, an octyl tin-based compound or a butyl tin-based compound may be used.

[0113] (Fourth embodiment) The present invention provides, as a fourth embodiment, a pouch-type secondary battery in which a lower pouch having a thickness greater than that of an upper pouch is used, and the upper pouch and the lower pouch in the sealed area after a sealing process have the same thickness.

[0114] <Pouch-type secondary battery> In the first embodiment described above, the average thickness of the unsealed area 102 of the upper pouch is set to be smaller than the average thickness of the unsealed area 102' of the lower pouch, thereby eliminating the imbalance in average thickness between the sealed area 101 of the upper pouch and the sealed area 101' of the lower pouch, even if more heat is supplied to the lower pouch 100'.

[0115] The fourth embodiment basically relates to another embodiment for solving the thermal imbalance more effectively while maintaining the first embodiment.

[0116] 8(a) and 8(b) are partially enlarged views of an upper pouch and a lower pouch, respectively, according to another embodiment of the present invention. The embodiment of FIG. 8 is characterized in that the thermal conductivity of the metal thin film layer 120' of the lower pouch is greater than that of the metal thin film layer 120 of the upper pouch.

[0117] Heat supplied to the second resin layer 130' of the lower pouch from the lower sealing groove 523 of the sealing device 500 passes through the metal thin film layer 120' of the lower pouch and is transferred to the first resin layer 110'. At this time, the lower the thermal conductivity of the metal thin film layer 120' of the lower pouch, the less the amount of heat transferred from the second resin layer 130' to the first resin layer 110'. Therefore, by lowering the thermal conductivity of the metal thin film layer 120' of the lower pouch and reducing the amount of heat supplied from the sealing device 500 to the first resin layer 110', the survival rate of the first resin layer 110' can be increased.

[0118] However, if the thermal conductivity of the metal thin film layer 120' of the lower pouch is too small compared to the thermal conductivity of the metal thin film layer 120 of the upper pouch, the second resin layer 130' of the lower pouch will absorb most of the heat supplied from the lower sealing groove 523, which may actually reduce the thickness of the second resin layer 130' and lower the survival rate of the second resin layer 130'. Therefore, it is preferable to select a metal thin film layer 120' having a suitable thermal conductivity.

[0119] The metal thin film layers 120, 120' may be made of one or more of an alloy of iron (Fe), carbon (C), chromium (Cr) and manganese (Mn), an alloy of iron (Fe), carbon (C), chromium (Cr) and nickel (Ni), aluminum (Al) and copper (Cu). The present invention does not limit the material, but it is preferable to use aluminum (Al) in terms of flexibility. As an example, the metal thin film layer 120 of the upper pouch may be made of aluminum A1, and the metal thin film layer 120' of the lower pouch may be made of an alloy containing aluminum (Al) and iron (Fe). This is because iron (Fe) has a lower thermal conductivity than aluminum (Al), and the metal thin film layer 120' of the lower pouch may be made of an alloy containing aluminum (Al) and iron (Fe), so that the thermal conductivity may be relatively lower than that of the metal thin film layer 120 of the upper pouch.

[0120] Conversely, the metal thin film layer 120' of the lower pouch may be made of aluminum (Al), and the metal thin film layer 120 of the upper pouch may be made of an alloy containing aluminum (Al) and copper (Cu). By using the property that copper (Cu) has a higher thermal conductivity than aluminum (Al), the metal thin film layer 120 of the upper pouch may be made of an alloy containing aluminum (Al) and copper (Cu), and the thermal conductivity may be relatively higher than that of the metal thin film layer 120' of the lower pouch.

[0121] Fifth embodiment The present invention provides, as a fifth embodiment, a method for manufacturing a pouch-type secondary battery in which a lower pouch having a thickness greater than that of an upper pouch is used, and the upper pouch and the lower pouch have the same level of thickness in a sealed area after a sealing process.

[0122] <Manufacturing method of pouch-type secondary battery> The present invention provides a method for manufacturing the above-mentioned pouch-type secondary battery 10. In one example, the method for manufacturing the pouch-type secondary battery 10 according to the present invention may include the steps of preparing an electrode assembly 300, an electrode lead 400 extending from an electrode tab 420 of the electrode assembly 300, an upper pouch 100 covering upper surfaces of the electrode assembly 300 and the electrode tab 420, and a lower pouch 100' covering lower surfaces of the electrode assembly 300 and the electrode tab 420.

[0123] Thereafter, the electrode lead 400 and the electrode assembly 300 may be positioned between the upper pouch 100 and the lower pouch 100', and the edges of the upper pouch 100 and the lower pouch 100' may be sealed by applying pressure and heat with a sealing device 500. At this time, the average thickness of the sealed region 101 of the upper pouch and the average thickness of the sealed region 101' of the lower pouch may be at the same level, while the average thickness of the unsealed region 102 of the upper pouch may be smaller than the average thickness of the unsealed region 102' of the lower pouch.

[0124] In a specific example, in the manufacturing method of the pouch-type secondary battery 10 according to the present invention, the average thickness of the sealing area 101 of the upper pouch and the average thickness of the sealing area 101' of the lower pouch may satisfy the following formula 1, and the average thickness of the unsealed area 102 of the upper pouch and the average thickness of the unsealed area 102' of the lower pouch may satisfy the following formula 2.

[0125] [Formula 1] 0.95≦D 1 TOP / D 1 BOTTOM ≦1.05

[0126] In formula 1, D 1 TOP represents the average thickness of the sealing area 101 of the upper pouch, and D 1 BOTTOM represents the average thickness of the sealing area 101' of the lower pouch.

[0127] [Formula 2] 0.65≦D 2 TOP / D 2 BOTTOM ≦0.95

[0128] In Equation 2, D 2 TOP represents the average thickness of the unsealed area 102 of the upper pouch, and D 2 BOTTOM represents the average thickness of the unsealed area 102' of the lower pouch.

[0129] Meanwhile, the upper pouch and the lower pouch in the above preparation stage may each include a metal thin film layer 120, 120', a first resin layer 110, 110' formed on the inside of the metal thin film layer 120, 120' facing the electrode lead 400 or the electrode assembly 300, and a second resin layer 130, 130' formed on the outside of the metal thin film layer 120, 120'.

[0130] In this case, the average thickness deviation between the metal thin film layer 120 and the second resin layer 130 in the unsealed area 102 of the upper pouch and the metal thin film layer 120' and the second resin layer 130' in the unsealed area 102' of the lower pouch is 5% or less, while the average thickness of the first resin layer 110 of the upper pouch can be made smaller than the average thickness of the first resin layer 110' of the lower pouch.

[0131] Specifically, the average thickness of the first resin layer 110 in the unsealed area 102 of the upper pouch and the average thickness of the first resin layer 110' in the unsealed area 102' of the lower pouch may satisfy the following formula 3.

[0132] [Formula 3] 0.55≦D 3 TOP / D 3 BOTTOM ≦0.85

[0133] In Equation 3, D 3 TOP represents the average thickness of the first resin layer 110 in the unsealed area 102 of the upper pouch, and D 3 BOTTOM represents the average thickness of the first resin layer 110' in the unsealed area 102' of the lower pouch.

[0134] That is, in manufacturing the pouch-type secondary battery 10 according to the present invention, after a sealing process in which the upper pouch 100 and the lower pouch 100' are heat-sealed using the lower pouch 100' that is thicker than the upper pouch 100, the sealing area 101 of the upper pouch and the sealing area 101' of the lower pouch can have the same thickness. This can improve the imbalance that occurs when the internal pressure is concentrated only in the sealing area 101' of the lower pouch having a thin thickness, causing the sealing part to open.

[0135] The present invention has been described in more detail above with reference to the drawings and embodiments, etc. However, the configurations described in the drawings or embodiments, etc. in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, so it should be understood that there may be various equivalents and modifications that can replace them at the time of filing this application. [Explanation of symbols]

[0136] 10: Pouch-type secondary battery 100: Upper pouch 100': Lower pouch 101: Sealing area of ​​upper pouch 101': Sealing area of ​​lower pouch 102: Unsealed area of ​​upper pouch 102': Unsealed area of ​​lower pouch 110, 110': First resin layer 120, 120': Metal thin film layer 130, 130': Second resin layer 140, 140': Adhesive layer 150: silylated first resin layer 300: electrode assembly 400: Electrode lead 410: Lead film 420: Electrode tab 500: Sealing device 510: Upper sealing block 511: First upper step 512: Second upper step 513: Upper sealing groove 520: Lower sealing block 521: First lower step 522: Second lower step 523: Lower sealing groove A: Height of the first upper step A': Height of the first lower step B: Height of the second upper step B': Height of the second lower step C, C': thickness of first resin layer D, D': thickness of metal thin film layer E, E': thickness of the second resin layer

Claims

1. electrode assembly, an electrode lead extending from an electrode tab of the electrode assembly; an upper pouch for covering an upper surface of the electrode assembly and the electrode lead; and a lower pouch for covering the electrode assembly and a lower surface of the electrode lead; the upper pouch and the lower pouch include a sealing region having sealed edges; The average thickness of the sealing region of the upper pouch and the average thickness of the sealing region of the lower pouch satisfy the following formula 1: The average thickness of the unsealed area of ​​the upper pouch and the average thickness of the unsealed area of ​​the lower pouch satisfy the following formula 2: [Formula 1] 0.95≦D １ ＴＯＰ / D １ ＢＯＴＴＯＭ ≦1.05 In Formula 1, D １ ＴＯＰ represents the average thickness of the sealing area of ​​the upper pouch, D １ ＢＯＴＴＯＭ represents the average thickness of the sealing area of ​​the lower pouch, [Formula 2] 0.65≦D ２ ＴＯＰ / D ２ ＢＯＴＴＯＭ ≦0.95 In formula 2, D ２ ＴＯＰ represents the average thickness of the unsealed area of ​​the upper pouch, D ２ ＢＯＴＴＯＭ represents the average thickness of the unsealed area of ​​the lower pouch, pouch-type secondary battery.

2. The average thickness (D ２ ＴＯＰ ) is in the range of 130 to 165 μm; The average thickness (D ２ ＢＯＴＴＯＭ 2. The pouch-type secondary battery according to claim 1, wherein the thickness of the first electrode is in the range of 175 to 200 μm.

3. 2. The pouch-type secondary battery according to claim 1, wherein the upper pouch and the lower pouch each have a three-layer structure including a metal thin film layer, a first resin layer formed on an inner side of the metal thin film layer facing the electrode assembly or the electrode lead, and a second resin layer formed on an outer side of the metal thin film layer.

4. The deviation between the average thickness of the metal thin film layer and the second resin layer in the unsealed region of the upper pouch and the average thickness of the metal thin film layer and the second resin layer in the unsealed region of the lower pouch is 5% or less, The pouch-type secondary battery according to claim 3 , wherein an average thickness of the first resin layer in the unsealed region of the upper pouch is smaller than an average thickness of the first resin layer in the unsealed region of the lower pouch.

5. The average thickness of the first resin layer in the unsealed region of the upper pouch and the average thickness of the first resin layer in the unsealed region of the lower pouch satisfy the following formula 3: [Formula 3] 0.55≦D ３ ＴＯＰ / D ３ ＢＯＴＴＯＭ ≦0.85 In formula 3, D ３ ＴＯＰ represents the average thickness of the first resin layer in the unsealed area of ​​the upper pouch; D ３ ＢＯＴＴＯＭ The pouch-type secondary battery according to claim 3 or 4, wherein represents an average thickness of the first resin layer in an unsealed region of the lower pouch.

6. The average thickness (D ３ ＴＯＰ ) is in the range of 70 to 85 μm; The average thickness (D ３ ＢＯＴＴＯＭ 6. The pouch-type secondary battery according to claim 5, wherein the thickness of the first electrode is in the range of 100 to 125 μm.

7. The pouch-type secondary battery according to claim 3 , wherein the first resin layer is a polypropylene resin, and the second resin layer contains a polyethylene terephthalate resin.

8. The pouch-type secondary battery according to claim 7 , wherein an average thickness of the sealed area of ​​the upper pouch and the sealed area of ​​the lower pouch is mainly affected by a thickness of the first resin layer.

9. The pouch-type secondary battery according to claim 3 , wherein the elongation rate of the first resin layer of the lower pouch is smaller than the elongation rate of the first resin layer of the upper pouch.

10. The pouch-type secondary battery according to claim 3 , wherein the thermal conductivity of the metal thin film layer of the lower pouch is greater than the thermal conductivity of the metal thin film layer of the upper pouch.

11. preparing an electrode assembly, an electrode lead extending from an electrode tab of the electrode assembly, an upper pouch covering an upper surface of the electrode assembly and the electrode tab, and a lower pouch covering a lower surface of the electrode assembly and the electrode tab; positioning the electrode lead and the electrode assembly between an upper pouch and a lower pouch, and sealing edges of the upper pouch and the lower pouch by applying pressure and heat with a sealing device; The average thickness of the sealing region of the upper pouch and the average thickness of the sealing region of the lower pouch satisfy the following formula 1: The average thickness of the unsealed area of ​​the upper pouch and the average thickness of the unsealed area of ​​the lower pouch satisfy the following formula 2: [Formula 1] 0.95≦D １ ＴＯＰ / D １ ＢＯＴＴＯＭ ≦1.05 In Formula 1, D １ ＴＯＰ represents the average thickness of the sealing area of ​​the upper pouch, D １ ＢＯＴＴＯＭ represents the average thickness of the sealing area of ​​the lower pouch, [Formula 2] 0.65≦D ２ ＴＯＰ / D ２ ＢＯＴＴＯＭ ≦0.95 In formula 2, D ２ ＴＯＰ represents the average thickness of the unsealed area of ​​the upper pouch, D ２ ＢＯＴＴＯＭ represents the average thickness of the unsealed area of ​​the lower pouch.

12. In the preparing step, each of the upper pouch and the lower pouch includes a metal thin film layer, a first resin layer formed on an inner side of the metal thin film layer facing the electrode lead or the electrode assembly, and a second resin layer formed on an outer side of the metal thin film layer, The deviation between the average thickness of the metal thin film layer and the second resin layer in the unsealed region of the upper pouch and the average thickness of the metal thin film layer and the second resin layer in the unsealed region of the lower pouch is 5% or less, The method for manufacturing a pouch-type secondary battery according to claim 11 , wherein an average thickness of the first resin layer of the upper pouch is smaller than an average thickness of the first resin layer of the lower pouch.

13. The average thickness of the first resin layer in the unsealed region of the upper pouch and the average thickness of the first resin layer in the unsealed region of the lower pouch satisfy the following formula 3: [Formula 3] 0.55≦D ３ ＴＯＰ / D ３ ＢＯＴＴＯＭ ≦0.85 In formula 3, D ３ ＴＯＰ represents the average thickness of the first resin layer in the unsealed area of ​​the upper pouch; D ３ ＢＯＴＴＯＭ The method for manufacturing a pouch-type secondary battery according to claim 12 , wherein represents an average thickness of the first resin layer in an unsealed region of the lower pouch.

14. The sealing device includes an upper sealing block having a two-stage upper sealing groove including a first upper step forming a bottom surface and a second upper step formed between a surface of the upper sealing block and the first upper step; a lower sealing block having a two-stage lower sealing groove including a first lower step forming a bottom surface and a second lower step formed between a surface of the lower sealing block and the first lower step; The method of claim 11, wherein a height of the first and second upper steps of the upper sealing block is smaller than a height of the first and second lower steps of the lower sealing block.

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