Pouch-type batteries and sealing devices for pouch-type batteries

Abstract

The present invention relates to a pouch-type battery and a sealing device for the pouch-type battery, and prevents a phenomenon in which the thickness of a lower pouch is reduced during a sealing process using heat sealing, thereby reducing safety.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0167905 filed on November 30, 2021, and all the contents disclosed in the literature of the Korean patent application are included as part of this specification.

[0002] The present invention relates to a pouch-type battery and a sealing device for the pouch-type battery, and prevents a phenomenon in which the thickness of the lower pouch decreases and the safety decreases during the sealing process by heat fusion.

Background Art

[0003] Technological development and demand for mobile devices have increased, and the demand for secondary batteries as an energy source to replace fossil fuels has increased rapidly, and thus many studies on secondary batteries that can meet various requirements have been conducted.

[0004] When looking at secondary batteries from the shape surface of the battery case, they are typically classified into cylindrical batteries and prismatic batteries in which electrode assemblies are built into cylindrical or prismatic metal cans, and pouch-type batteries in which electrode assemblies are built into a pouch-type case of an aluminum laminate sheet. And 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 having a thin thickness in terms of shape, being easy to stack and arrange, and being able to partially deform the shape. The pouch-type battery has a structure in which an electrode assembly and an electrolyte are built into a pouch-type laminate sheet capable of accommodating the electrode assembly, and the resin layer of the laminate sheet has the characteristic of being capable of heat fusion.

[0006] In pouch-type batteries, heat and pressure are applied to laminate sheets that are layered vertically around the battery case to seal the electrode assembly and prevent electrolyte leakage, thus preventing the electrode assembly from being exposed to the outside. Electrode leads protrude from the outside of the pouch-type battery case, and lead films are attached to the surface of the electrode leads. These insulating resin lead films are heat-sealed together with the laminate sheets, i.e., the pouch, to provide a more robust seal around the electrode leads.

[0007] However, when heat-sealing pouches, the pair of pouches enclosing the electrode assembly and electrode leads often have different thicknesses after heat sealing. Heat and pressure are applied using a pair of upper and lower sealing blocks to seal the electrode leads and pouches. In the sealing process, the lower sealing block is raised to support the lower pouch and electrode leads, and then the upper sealing block is lowered to apply heat and pressure. As a result, more heat is supplied to the lower pouch and electrode leads, making it more likely that the resin layer of the lower pouch will become thinner than that of the upper pouch.

[0008] The relatively thin lower pouch is more vulnerable to internal or external pressure. For example, when pressure below the specified endurance limit acts on a pouch-type battery, the upper pouch may withstand the pressure while the lower pouch ruptures, or the resin layer of the lower pouch may stretch and break due to internal pressure from gas generated within the pouch, causing the seal to open. [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The present invention aims to solve the above-mentioned problems and provides a pouch-type battery and a sealing device for the pouch-type battery that prevent a reduction in the thickness of the lower pouch even after sealing by heat fusion. [Means for solving the problem]

[0010] The present invention provides a sealing device for pouch-type batteries. In one embodiment, the sealing device for pouch-type batteries according to the present invention includes an upper sealing block having two upper sealing grooves, including a first upper step forming the bottom surface and a second upper step formed between the first upper step and the surface; and a lower sealing block having two lower sealing grooves, including a first lower step forming the bottom surface and a second lower step formed between the first lower step and the surface. Furthermore, the upper sealing block is in contact with the first surface of the electrode lead sealing portion of the pouch-type battery, and the lower sealing block is in contact with the second surface of the electrode lead sealing portion of the pouch-type battery at a position facing the upper sealing block. Furthermore, the sealing device for pouch-type batteries according to the present invention satisfies the following condition 1.

[0011] [Condition 1]

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[0012] In condition 1 above, B1 represents the difference in average depth between the first upper step and the second upper step in the upper sealing block, and B2 represents the difference in average depth between the first lower step and the second lower step in the lower sealing block.

[0013] In one embodiment, the average depth difference (B1) between the first upper step and the second upper step in the upper sealing block is in the range of 200 to 280 μm. Also, the average depth difference (B2) between the first lower step and the second lower step in the lower sealing block is in the range of 220 to 320 μm.

[0014] In one embodiment, the difference between the average depth (A1) of the second upper step and the average depth (A2) of the second lower step is 10 μm or less. Specifically, the difference between the average depth (A1) of the second upper step and the average depth (A2) of the second lower step is in the range of 0.1 to 10 μm, or in the range of 0.1 to 5 μm. For example, the average depth A1 of the second upper step and the average depth A2 of the second lower step are substantially the same.

[0015] In a specific embodiment, the average depth (A1) of the second upper step and the average depth (A2) of the second lower step are in the range of 40 to 100 μm or 70 to 80 μm, respectively.

[0016] In another embodiment, the upper and lower sealing blocks are structured to pressurize and heat the electrode lead sealing portion of the pouch-type battery on both sides. In this case, for example, the heating temperature is in the range of 110 to 200°C.

[0017] Furthermore, the present invention provides a pouch-type battery manufactured via the sealing device described above. In one embodiment, the pouch-type battery according to the present invention includes an electrode assembly, electrode leads extending from the electrode tabs of the electrode assembly, and an upper pouch and a lower pouch that house and seal the electrode assembly. The following condition 2 is also satisfied with respect to the electrode lead sealing portion, in which the upper pouch and the lower pouch enclose the electrode leads on both sides so that the electrode leads of the electrode assembly are exposed.

[0018] [Condition 2] 1 ≤ T2 - T1 ≤ 25 (μm)

[0019] In condition 2 above, T1 represents the average thickness of the upper pouch formed on the first surface of the electrode lead, and T2 represents the average thickness of the lower pouch formed on the second surface of the electrode lead.

[0020] In one embodiment, the pouch-type battery according to the present invention has an average thickness (T1) of the upper pouch formed on the first surface of the electrode lead, relative to the electrode lead sealing portion, in the range of 80 to 90 μm, and an average thickness (T2) of the lower pouch formed on the second surface of the electrode lead, in the range of 91 to 105 μm.

[0021] In another embodiment, the upper pouch and the lower pouch each include a first resin layer located on the inner surface, a metal layer, and a second resin layer located on the outer surface. And, based on the electrode lead sealing portion, the thickness ratio of the first resin layer of the upper pouch is in the range of 10 to 18% based on the thickness of the upper pouch. Also, the thickness ratio of the first resin layer of the lower pouch is in the range of 20 to 30% based on the thickness of the lower pouch.

[0022] In a specific embodiment, based on the electrode lead sealing portion, the thickness of the first resin layer of the upper pouch is in the range of an average of 8 to 17 μm, and the thickness of the first resin layer of the lower pouch is in the range of an average of 20 to 30 μm.

[0023] In another embodiment, the pouch-type battery according to the present invention corresponds to the position where the electrode assembly is accommodated, includes an unsealed region where the upper pouch and the lower pouch are not sealed, and in the unsealed region, the thicknesses of the first resin layers of the upper pouch and the lower pouch are each in the range of an average of 50 to 100 μm.

[0024] In a specific embodiment, the upper pouch and the lower pouch each include polypropylene (Ppolypropylene) resin that becomes the first resin layer, aluminum or an aluminum alloy that becomes the metal layer, and PET (Polyethylene terephthalate) resin that becomes the second resin layer.

[0025] For example, the electrode assembly is a stacked electrode assembly.

Effects of the Invention

[0026] The sealing device for the pouch-type battery of the present invention having the above-described configuration can prevent the thickness of the lower pouch from being reduced even after the sealing process by thermal fusion. Also, the manufactured pouch-type battery can maintain the sealing property even against a larger change in internal and external pressure.

Brief Description of the Drawings

[0022]

[0027] [Figure 1] This is a schematic diagram illustrating the process of sealing a pouch-type battery using a sealing device 10 (hereinafter abbreviated as "sealing device") according to one embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view illustrating a sealing device for a pouch-type battery according to one embodiment of the present invention. [Figure 3] This is a schematic diagram illustrating the process of sealing the electrode lead formation portion of a pouch-type battery using a pouch-type battery sealing device according to one embodiment of the present invention. [Figure 4] This is a schematic diagram illustrating a pouch-type battery 500 that has been sealed using the pouch-type battery sealing device according to the present invention. [Figure 5] Figure 4 is a magnified view of the A-A' cross-section of the pouch-type battery 500. [Modes for carrying out the invention]

[0028] The present invention can be modified in various ways and may have a variety of embodiments; therefore, specific embodiments will be described in detail below.

[0029] However, this should not be understood as limiting the present invention to any particular embodiment, but rather as including all modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

[0030] In the present invention, terms such as "includes" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof as described in the specification, and should be understood not to preemptively exclude the presence or possibility of adding one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0031] Furthermore, in this invention, when a part such as a layer, film, region, or plate is described as being "on top" of another part, this includes not only the case where it is "directly on top" of the other part, but also the case where another part is located in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is located in between. Also, in this application, being "on top" may include being located not only at the top but also at the bottom.

[0032] The present invention provides a sealing device for pouch-type batteries. In one embodiment, the sealing device for pouch-type batteries according to the present invention includes an upper sealing block having two upper sealing grooves, including a first upper step forming the bottom surface and a second upper step formed between the first upper step and the surface; and a lower sealing block having two lower sealing grooves, including a first lower step forming the bottom surface and a second lower step formed between the first lower step and the surface. Furthermore, the upper sealing block is in contact with the first surface of the electrode lead sealing portion of the pouch-type battery, and the lower sealing block is in contact with the second surface of the electrode lead sealing portion of the pouch-type battery at a position facing the upper sealing block.

[0033] In the present invention, the electrode lead sealing portion refers to the region where the electrode lead protrudes from the electrode assembly. Specifically, the electrode lead sealing portion, viewed from a cross-sectional perspective, is a structure in which a lead metal made of aluminum or copper metal protrudes, and the region in which the lead metal is sealed by the pouch is wrapped in a lead film. The upper pouch is structured to enclose the upper side of the electrode lead, and the lower pouch is structured to enclose the lower side of the electrode lead. In the present invention, the first upper step and the first lower step are regions in which the upper and lower sides of the lead metal wrapped in the lead film are inserted and sealed, respectively. Furthermore, the second upper step and the second lower step are regions in which the extension of the lead film remaining on the side surface of the lead metal is wrapped and sealed from above and below, respectively.

[0034] Furthermore, the sealing device for pouch-type batteries according to the present invention satisfies the following condition 1.

[0035] [Condition 1]

number

[0036] In condition 1 above, B1 represents the difference in average depth between the first upper step and the second upper step in the upper sealing block, and B2 represents the difference in average depth between the first lower step and the second lower step in the lower sealing block.

[0037] The sealing device for pouch-type batteries according to the present invention prevents a reduction in the thickness of the lower pouch during the sealing process of the electrode lead sealing portion by securing space in the lower region. Specifically, in the above-mentioned sealing device for pouch-type batteries, the first lower step of the lower sealing block is made deeper, thereby blocking the concentration of heat and pressure in the lower pouch.

[0038] The value of the formula defined in Condition 1 in the present invention is in the range of 6.5-15%, 6.5-10%, 7.5-15%, 7.5-9%, or 8-8.5%. By satisfying the above range for the value of Condition 1, the sealing device for pouch-type batteries according to the present invention can minimize the reduction in the thickness of the lower pouch and prevent the pouch surrounding the electrode lead sealing portion from expanding.

[0039] In one embodiment, the average depth difference B1 between the first upper step and the second upper step in the upper sealing block is in the range of 200 to 280 μm. Here, the depth difference between the first upper step and the second upper step refers, for example, to the depth from the bottom surface of the second upper step to the bottom surface of the first upper step. Specifically, the depth difference B1 between the first upper step and the second upper step is in the range of 200 to 250 μm, 220 to 280 μm, or 220 to 250 μm.

[0040] Furthermore, the average depth difference B2 between the first and second lower steps in the lower sealing block is in the range of 220 to 320 μm. Here, the depth difference between the first and second lower steps refers, for example, to the depth from the bottom surface of the second lower step to the bottom surface of the first lower step. Specifically, the depth difference B2 between the first and second lower steps is in the range of 220 to 300 μm, 250 to 320 μm, or 250 to 280 μm.

[0041] In this invention, the depth of the lower sealing groove formed by the lower pouch is made deeper than the depth of the upper sealing groove formed by the upper pouch, with respect to the electrode lead sealing portion. This minimizes the reduction in the thickness of the lower pouch during the sealing process. For example, the difference in average depth B1 between the first upper step and the second upper step in the upper sealing block is made 5 to 20 μm greater than the difference in average depth B1 between the first upper step and the second upper step in the upper sealing block.

[0042] In one embodiment, the difference between the average depth A1 of the second upper step and the average depth A2 of the second lower step is 10 μm or less. Specifically, the difference between the average depth A1 of the second upper step and the average depth A2 of the second lower step is in the range of 0.1 to 10 μm, or 0.1 to 5 μm. For example, the average depth A1 of the second upper step and the average depth A2 of the second lower step are substantially the same. In a specific embodiment, the average depth A1 of the second upper step and the average depth A2 of the second lower step are in the range of 40 to 100 μm, or 70 to 80 μm, respectively.

[0043] In another embodiment, the upper and lower sealing blocks are structured to pressurize and heat the electrode lead sealing portion of the pouch-type battery on both sides. In this case, the heating temperature is in the range of 110 to 200°C on average. The sealing device for pouch-type batteries according to the present invention is a device that seals the edge region of the pouch-type battery by applying heat and pressure. Heating partially melts the resin layer located on the inner surface of the pouch, and pressurization joins the partially melted resin layers of the upper and lower pouches. The above heating temperature can be selected considering the type of internal resin layer to be applied, etc. For example, the inner surface of the pouch can be formed with a polypropylene (PP) layer with a melting point in the range of 130 to 171°C, in which case the heating temperature can be controlled in the range of 120 to 180°C.

[0044] Furthermore, the present invention provides a pouch-type battery manufactured via the sealing device described above. The pouch-type battery according to the present invention embodies a lower pouch thickness that is above a certain level, based on the electrode lead sealing portion. In one embodiment, the pouch-type battery according to the present invention includes an electrode assembly, electrode leads extending from the electrode tabs of the electrode assembly, and an upper pouch and a lower pouch that house and seal the electrode assembly. The pouch-type battery according to the present invention also satisfies the following condition 2, based on the electrode lead sealing portion, in which the upper pouch and the lower pouch enclose the electrode lead on both sides so that the electrode leads of the electrode assembly are exposed.

[0045] [Condition 2] 1 ≤ T2 - T1 ≤ 25 (μm)

[0046] In condition 2 above, T1 represents the average thickness of the upper pouch formed on the first surface of the electrode lead, and T2 represents the average thickness of the lower pouch formed on the second surface of the electrode lead.

[0047] In this invention, "pouch" refers to the material of the battery case that encloses the battery. A pouch-type battery includes a structure in which the upper and lower surfaces of the electrode assembly are covered with a pouch and the edges are sealed. During the sealing process, the thickness of the lower pouch decreases, which can cause product defects. The pouch-type battery according to the present invention minimizes the reduction in the thickness of the lower pouch relative to the electrode lead sealing portion.

[0048] In one specific embodiment, the average thickness T1 of the upper pouch formed on the first surface of the electrode lead is in the range of 80 to 90 μm, and the average thickness T2 of the lower pouch formed on the second surface of the electrode lead is in the range of 91 to 105 μm. Specifically, the average thickness T1 of the upper pouch formed on the first surface of the electrode lead is in the range of 83 to 88 μm, and the average thickness T2 of the lower pouch formed on the second surface of the electrode lead is in the range of 94 to 100 μm.

[0049] Specifically, the difference in thickness T2-T1 defined in condition 2 above is in the range of 1-25 μm, 5-20 μm, 6-17 μm, or 8-12 μm.

[0050] The pouch-type battery according to the present invention has a structure in which the lower pouch is formed thicker than the upper pouch, with respect to the electrode lead sealing portion. Normally, heat and pressure are concentrated in the lower pouch during the sealing process, and the thickness of the lower pouch tends to become relatively smaller. However, in the present invention, by applying the sealing device described above, the average thickness of the lower pouch is formed to be 1 μm or more, specifically 6 μm or more, thicker than the upper pouch. When an external force is applied to the pouch-type battery or the internal pressure increases, the electrode lead sealing portion will rupture, and in particular, the lower pouch portion of the electrode lead sealing portion will expand first. In the present invention, the sealing performance of the battery can be improved by increasing the remaining amount of the lower pouch in the electrode lead sealing portion of the pouch-type battery.

[0051] The above-mentioned pouch has a structure that includes, for example, a first resin layer located on the inner surface, a metal layer, and a second resin layer located on the outer surface. During the sealing process, the thickness of the first resin layer located on the inner surface changes significantly, while the thicknesses of the metal layer and the second resin layer do not change much. During the sealing process, for example, the thickness of the first resin layer decreases significantly, while the thicknesses of the metal layer and the second resin layer are maintained without significant fluctuation. In particular, compared to the upper pouch, the thickness of the first resin layer in the lower pouch decreases significantly, which can cause sealing failure and lead to the problem of the sealed area being prone to tearing when internal and external pressure increases.

[0052] In one embodiment, the upper pouch and lower pouch according to the present invention each include a first resin layer located on the inner surface, a metal layer, and a second resin layer located on the outer surface. Furthermore, with respect to the electrode lead sealing portion, the thickness ratio of the first resin layer of the upper pouch is in the range of 10 to 18% of the thickness of the upper pouch, and the thickness ratio of the first resin layer of the lower pouch is in the range of 20 to 30% of the thickness of the lower pouch. Specifically, in the present invention, the thickness ratio of the first resin layer of the upper pouch is in the range of 13 to 17% of the thickness of the upper pouch, and the thickness ratio of the first resin layer of the lower pouch is in the range of 22 to 28% of the thickness of the lower pouch.

[0053] The present invention is characterized by forming the first resin layer of the lower pouch with a greater thickness, based on the electrode lead sealing portion. In the pouch laminated structure, the first resin layer is the layer that provides adhesive force during the sealing process. By forming the first resin layer of the lower pouch with a greater thickness, the adhesive force with the electrode lead is increased, and excellent durability even under high pressure can be achieved.

[0054] In a specific example, using the electrode lead sealing area as a reference, the thickness of the first resin layer of the upper pouch is in the average range of 8 to 17 μm, specifically in the average range of 10 to 15 μm. Also, using the electrode lead sealing area as a reference, the thickness of the first resin layer of the lower pouch is in the average range of 20 to 30 μm, specifically in the average range of 22 to 26 μm.

[0055] In another embodiment, the pouch-type battery according to the present invention includes an unsealed region corresponding to the position in which the electrode assembly is housed, where the space between the upper pouch and the lower pouch is not sealed. Correspondingly, the portion where the upper pouch and the lower pouch are bonded together by heat fusion or the like is called a sealed region. In the unsealed region, the thickness of the first resin layer of the upper pouch and the lower pouch is in the range of 50 to 100 μm on average.

[0056] The above-mentioned pouch has a structure that includes, for example, a first resin layer located on the inner surface, a metal layer, and a second resin layer located on the outer surface. For example, in the upper and lower pouches, the first resin layer contains polypropylene (PP) resin, and the metal layer contains aluminum or an alloy thereof. It also contains PET (Polyethylene terephthalate) resin as the second resin layer, and may have a two-layer structure including a nylon layer and a PET layer formed on top of it. The thickness of the pouch may vary depending on the product or specifications, but is in the average range of 120 to 200 μm. Furthermore, based on the pouch before the sealing process, the thickness of the first resin layer inside the pouch is in the average range of 50 to 100 μm.

[0057] During the sealing process, the thickness of the first resin layer located on the inner surface changes significantly, while the thicknesses of the metal layer and the second resin layer remain largely unchanged. Specifically, the polypropylene resin forming the first resin layer has a relatively low melting point. Therefore, when heat is applied for sealing, the surface of the first resin layer partially melts and is thermally fused to the opposing layer. However, during the sealing process, pressure is also applied in addition to heat, which significantly reduces the thickness of the first resin layer. This reduction in the thickness of the first resin layer leads to sealing defects and causes problems such as the sealed area being prone to tearing when the internal pressure increases.

[0058] In one embodiment, the electrode assembly according to the present invention is a stacked electrode assembly. The stacked electrode assembly encompasses a structure in which unit cell structures, including a positive electrode, a separator membrane, and a negative electrode, are repeatedly stacked. The positive electrode and negative electrode include cases in which an active material layer is formed on one or both sides of the current collector. The number of times the unit cells are repeatedly stacked is, for example, in the range of 20 to 80 times and can be changed according to product specifications and required specifications. In the pouch-type battery according to the present invention, cylindrical and jelly-roll type structures are not excluded as forms of electrode assemblies, but the stacked electrode assembly can be applied more effectively.

[0059] The following describes specific examples of the present invention with reference to the attached drawings, but the scope of the present invention is not limited thereto.

[0060] (First Embodiment) Figure 1 is a schematic diagram illustrating the process of sealing a pouch-type battery using a sealing device 10 (hereinafter abbreviated as "sealing device") according to one embodiment of the present invention. Referring to Figure 1, the sealing device 10 of the present invention has a structure in which an upper pouch 400 and a lower pouch 401 are arranged above and below the electrode lead 300, respectively, and the upper sealing block 100 and the lower sealing block 200 are pressurized and heated to perform sealing. The electrode lead 300 is made of aluminum, and its outer surface is wrapped with a lead film 310. The sealing device 10 also includes an upper sealing block 100 and a lower sealing block 200, and each has two-stage sealing grooves 130 and 230 formed therein.

[0061] The present invention makes the lower sealing groove 230 formed in the lower sealing block 200 relatively deeper than the upper sealing groove 130 formed in the upper sealing block 100.

[0062] (Second Embodiment) Figure 2 is a schematic cross-sectional view illustrating a sealing device for a pouch-type battery according to one embodiment of the present invention.

[0063] Referring to FIG. 2, the sealing device 10 includes an upper sealing block 100 and a lower sealing block 200. Sealing grooves 130 and 230 formed in two stages are formed in the upper sealing block 100 and the lower sealing block 200.

[0064] The upper sealing block 100 includes a two-stage upper sealing groove 130 including a first upper step 110 forming a bottom surface and a second upper step 120 formed between the first upper step 110 and the surface. Here, the bottom surface and the surface are based on the direction of looking inside the upper sealing groove 130. The bottom surface means the lowest surface, and the surface means the highest surface.

[0065] The lower sealing block 200 also includes a lower sealing groove 230 formed in two stages. The lower sealing groove 230 includes a first lower step 210 forming a bottom surface and a second lower step 220 formed between the first lower step 210 and the surface.

[0066] In the sealing device 10, there is a difference in the height of the steps between the upper sealing groove 130 formed in the upper sealing block 100 and the lower sealing groove 230 formed in the lower sealing block 200. Specifically, the height A2 of the first lower step is higher than the height A1 of the first upper step (A1 < A2). Also, the height B1 of the second upper step and the height B2 of the second lower step are at the same level, and the difference is 10 μm or less.

[0067] For example, in the sealing device 10 described above, the height A1 of the first upper step formed in the upper sealing block 100 is 240 μm, and the height B1 of the second upper step is 76 μm. Similarly, the height A2 of the first lower step formed in the lower sealing block 200 is 260 μm, and the height B2 of the second lower step is 76 μm. This differs from conventional sealing devices, where the upper and lower sealing blocks have a symmetrical structure. Conventional sealing devices, for example, control the heights of the first upper step and the first lower step to be equivalent at a 250 μm level. The present invention is differentiated by lowering the height A1 of the first upper step and raising the height A2 of the first lower step.

[0068] (Third embodiment) Figure 3 is a schematic diagram illustrating the process of sealing the electrode lead formation portion of a pouch-type battery using a pouch-type battery sealing device according to one embodiment of the present invention.

[0069] Referring to Figure 3, the first upper step 110 of the upper sealing block 100 corresponds to the upper part of the electrode lead 300 wrapped in the lead film 310. The second upper step 120 corresponds to the upper part of the lead film 310 that extends and remains on the side of the electrode lead 300. The first lower step 210 of the lower sealing block 200 corresponds to the lower part of the electrode lead 300 wrapped in the lead film 310, and the second lower step 220 corresponds to the lower part of the lead film 310 that extends and remains on the side of the electrode lead 300.

[0070] The upper sealing block 100 and the lower sealing block 200 are heated by their built-in heating coils, which pressurize the electrode lead 300 interposed between the upper pouch 400 and the lower pouch 401. The upper pouch 400 and the lower pouch 401 have a structure in which an aluminum layer, a nylon resin layer, and a PET resin layer are laminated on top of an inner polypropylene (PP) resin layer. The heating temperature by the upper sealing block 100 and the lower sealing block 200 is at a level of approximately 150-180°C, and the polypropylene resin forming the inner surface of the pouch is partially melted and heat-fused, thereby realizing adhesive strength.

[0071] (Fourth Embodiment) Figure 4 is a schematic diagram illustrating a pouch-type battery 500 that has been sealed using the pouch-type battery sealing device according to the present invention, and Figure 5 is a partially enlarged view of the A-A' cross-section of the pouch-type battery 500 in Figure 4.

[0072] Referring to Figure 4, the pouch-type battery 500 has a structure in which a pouch-type battery case 440 encloses an electrode assembly housed inside, with electrode leads 300 extending from electrode tabs and protruding to the outside. A lead film 310 is located between the electrode leads 300 and the pouch-type battery case 440. The pouch-type battery case 440 includes an upper pouch 400 and a lower pouch 401, and its edges are sealed.

[0073] Figure 5 shows a cross-section of the sealing region of the electrode lead 300. The upper pouch 400 and the lower pouch 401 each have a three-layer structure including a first resin layer 410, 411 and an aluminum layer 420, 421 formed on the inside, and a second resin layer 430, 431 formed on the outside. The electrode lead 300 is also encased in a lead film 310.

[0074] In this invention, the safety of the battery is maximized by minimizing the reduction in the thickness of the first resin layer 411 in the lower pouch 401.

[0075] The present invention will be described in more detail below through examples and other means.

[0076] <Examples> The sealing of the pouch-type battery was performed using the sealing device shown in Figure 2. The sealing was performed based on the area where the electrode leads were formed. The heating temperature during the sealing process was 180°C, and the detailed specifications of the sealing device are summarized in Table 1 below.

[0077] Furthermore, the pouch used for the pouch-type battery has a three-layer structure consisting of a polypropylene layer, an aluminum layer, and a PET layer. The overall thickness of the pouch is 155 μm, of which the polypropylene resin layer is 80 μm thick.

[0078] <Comparative Example> Except for changing the specifications of the sealing device as shown in Table 1 below, sealing of the pouch-type battery was performed using the same method as in the example.

[0079] [Table 1]

[0080] <Experimental Example 1: Evaluation of PP residue rate in pouches> The remaining polypropylene layer was evaluated for the sealed pouch-type batteries in the examples and comparative examples. The PP remaining rate (%) was calculated by comparing the thickness of the polypropylene layer before sealing with the thickness of the polypropylene layer after sealing.

[0081] [Table 2]

[0082] Referring to Table 2, it can be seen that in the comparative example, heat and pressure were concentrated in the lower pouch during the sealing process, resulting in a PP retention rate of only 13% within the lower pouch.

[0083] In contrast, the pouch-type battery according to the embodiment shows that the PP remaining rate in the lower pouch is as high as 30%. If the pouch ruptures due to the application of external force or an increase in internal pressure, the lower pouch will expand first within the electrode lead sealing section. The present invention enhances the safety of pouch-type batteries by maximizing the PP remaining rate in the lower pouch within the electrode lead sealing section.

[0084] Furthermore, in the examples, it was confirmed that the PP retention rate in the upper pouch was low, at around 16%. This was because the upper pouch was more strongly heat-sealed at the electrode lead sealing portion, which reduced the PP retention rate in the upper pouch.

[0085] <Example of experiment> The sealing strength and internal pressure strength were evaluated for the sealed pouch-type batteries in the examples and comparative examples. The evaluation results are shown in Table 3 below.

[0086] Sealing strength evaluation: Under room temperature conditions, a vertical force is applied and the force at the point where the electrode lead sealing section breaks is measured.

[0087] Internal pressure strength: The internal pressure strength was measured under 60°C conditions. Specifically, a hole was made in one side of a sealed pouch-type battery, inactive gas (Ar) was injected, and the pressure at the point where the electrode lead sealing portion was damaged was measured.

[0088] [Table 3]

[0089] Referring to Table 3, it can be confirmed that the sealing strength and internal pressure strength of the pouch-type battery according to the example were significantly improved compared to the comparative example.

[0090] The present invention has been described in more detail above through the drawings and embodiments. However, the configurations described in the drawings or embodiments described herein are merely one embodiment of the present invention and do not represent the entire technical concept of the present invention. It should be understood that there are various equivalents and modifications that can be substituted for them at the time of filing this application. [Explanation of Symbols]

[0091] 10: Sealing device 100: Upper sealing block 110: First upper step 120: Second upper step 130: Upper sealing groove 200: Lower sealing block 210: First lower step 220: Second lower step 230: Lower sealing groove 300: Electrode Leads 310: Lead film 400: Top pouch 401: Lower pouch 410, 411: 1st resin layer 420, 421: Aluminum layer 430, 431: Second resin layer 440: Pouch-type battery case 500: Pouch-type battery A1: Height of the first upper step B1: Height of the second upper step A2: Height of the first lower step B2: Height of the second lower step

Claims

1. In a sealing device for pouch-type batteries, An upper sealing block having two upper sealing grooves formed, including a first upper step that forms the bottom surface and a second upper step formed between the first upper step and the surface, A lower sealing block having two lower sealing grooves formed, including a first lower step that forms the bottom surface and a second lower step formed between the first lower step and the surface, The upper sealing block is in contact with the first surface of the electrode lead sealing portion of the pouch-type battery, and the lower sealing block is in contact with the second surface of the electrode lead sealing portion of the pouch-type battery at a position facing the upper sealing block. The following condition 1 is met, [Condition 1] [Math 1] In the above condition 1, A1 indicates the height of the first upper step in the upper sealing block. A2 is a sealing device for pouch-type batteries, indicating the height of the first lower step in the lower sealing block.

2. The height of the first upper step in the upper sealing block is in the range of 200 to 280 μm. The sealing device for a pouch-type battery according to claim 1, wherein the height of the first lower step in the lower sealing block is in the range of 220 to 320 μm.

3. The sealing device for a pouch-type battery according to claim 1, wherein the difference between the height of the second upper step and the height of the second lower step is 10 μm or less.

4. The sealing device for a pouch-type battery according to claim 3, wherein the height of the second upper step and the height of the second lower step are each in the range of 40 to 100 μm.

5. The upper sealing block and the lower sealing block are structured to pressurize and heat the electrode lead sealing portion of the pouch-type battery on both sides. A sealing device for pouch-type batteries according to any one of claims 1 to 4, wherein the heating temperature is in the range of 110 to 200°C.

6. Electrode assembly and An electrode lead extending from the electrode tab of the electrode assembly, It includes an upper pouch and a lower pouch for housing and sealing the electrode assembly, Based on the electrode lead sealing portion, which has a structure in which the upper pouch and the lower pouch enclose the electrode lead of the electrode assembly on both sides so that the electrode lead is exposed, the following condition 2 is met: [Condition 2] 1≦T2-T1≦25 (μm) In the above condition 2, T1 indicates the average thickness of the upper pouch formed on the first surface of the electrode lead. T2 represents the average thickness of the lower pouch formed on the second surface of the electrode lead, in a pouch-type battery.

7. Using the electrode lead sealing portion as a reference, The pouch-type battery according to claim 6, wherein the average thickness of the upper pouch formed on the first surface of the electrode lead is in the range of 80 to 90 μm, and the average thickness of the lower pouch formed on the second surface of the electrode lead is in the range of 91 to 105 μm.

8. The upper pouch and the lower pouch each include a first resin layer located on the inner surface, a metal layer, and a second resin layer located on the outer surface, Using the electrode lead sealing portion as a reference, The thickness ratio of the first resin layer of the upper pouch is in the range of 10 to 18% based on the thickness of the upper pouch. The pouch-type battery according to claim 6, wherein the thickness ratio of the first resin layer of the lower pouch is in the range of 20 to 30% based on the thickness of the lower pouch.

9. Using the electrode lead sealing portion as a reference, The thickness of the first resin layer of the upper pouch is in the range of 8 to 17 μm on average. The pouch-type battery according to claim 8, wherein the thickness of the first resin layer of the lower pouch is in the range of 20 to 30 μm on average.

10. The pouch-type battery includes an unsealed region corresponding to the position in which the electrode assembly is housed, between the upper pouch and the lower pouch, where the seal is not maintained. The pouch-type battery according to claim 8, wherein in the unsealed region, the thickness of the first resin layer of the upper pouch and the lower pouch is in the range of 50 to 100 μm on average.

11. The upper pouch and the lower pouch are, respectively It contains a polypropylene resin which forms the first resin layer, It contains aluminum or an aluminum alloy that forms a metallic layer. The pouch-type battery according to claim 6, comprising a PET resin that forms the second resin layer.

12. The pouch-type battery according to any one of claims 6 to 11, wherein the electrode assembly is a stack-type electrode assembly.

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