Pouch-type battery cell and pouch-type battery case sealing device for manufacturing the same

Abstract

The present invention relates to a pouch-type battery cell including a pouch-type battery case made of a laminate sheet including a resin layer and a metal layer, and an electrode assembly housed in the pouch-type battery case, wherein a sealing portion that is sealed by heat fusion is formed around the outer periphery of the electrode assembly housing portion, the sealing portion is formed such that pressed portions and non-pressed portions are repeatedly arranged from the inside to the outside of the pouch-type battery case, and the thickness of the internal resin layer in the pressed portion decreases toward the outside of the pouch-type battery case, and the sealing portions of the pouch-type battery case can be sequentially bent due to a difference in sealing force of the sealing portions.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0088274, filed July 18, 2022, and Korean Patent No. 10-2023-0093018, filed July 18, 2023, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a pouch-type battery cell and a pouch-type battery case sealing device for manufacturing the same, and more particularly to a pouch-type battery cell that can quickly release gas when the internal pressure of the pouch-type battery cell increases, thereby preventing explosion, and a pouch-type battery case sealing device for manufacturing the same. [Background technology]

[0003] Rechargeable lithium secondary batteries are widely used as energy sources for wireless mobile devices or wearable devices, as well as for electric vehicles and hybrid electric vehicles, which are presented as alternatives to existing gasoline and diesel vehicles that cause air pollution.

[0004] Lithium secondary batteries can be classified into prismatic and cylindrical battery cells having metal can-type cases, and pouch-type battery cells having cases formed from laminate sheets. Among these, pouch-type battery cells are widely used due to their advantages of being easily deformable and capable of increasing energy density when stored and stacked.

[0005] In the lithium secondary battery, side reactions occur between the surface of the electrodes and the electrolyte during repeated charge and discharge. If the gas generated during this reaction cannot be discharged from the inside of the battery case, the battery case may expand and become deformed.

[0006] In particular, unlike cylindrical battery cells that include safety vents, pouch-type battery cells do not include a separate venting structure, so venting can occur in areas of the heat-sealed outer periphery where gas concentrates or in areas where the heat-sealed bond is weak.

[0007] In general, a pouch-type battery cell is manufactured by forming a laminate sheet including an outer coating layer, a metal layer, and an inner resin layer into a pouch-type battery case, housing an electrode assembly inside the pouch-type battery case, and then sealing the pouch-type battery case.

[0008] The laminate sheet may have a more complex and diverse layer structure depending on the embodiment and application environment.

[0009] To seal the pouch-type battery case, the outer periphery of the pouch-type battery case is pressed with a heating block that provides heat and pressure, thereby melting the inner resin layer, and the inner resin layer of the upper case and the inner resin layer of the lower case that are stacked together are heat-sealed.

[0010] Conventionally, the heating block presses the entire outer periphery of the pouch-type battery case with a uniform force, so that the adhesive strength of the entire sealing portion is uniform.

[0011] In such a case, even if the internal pressure of the pouch-type battery cell increases, venting is difficult, and the internal pressure of the pouch-type battery case increases gradually.

[0012] If an external impact is applied while the pouch-type battery case continues to expand, or if thermal runaway occurs due to a chemical chain reaction caused by an electrical short circuit, the pouch-type battery cell may explode.

[0013] Therefore, it is necessary to develop a pouch-type battery cell with a structure that can prevent explosion of the pouch-type battery cell by making the sealing pressure of the outer peripheral sealing portion of the pouch-type battery case uneven, thereby allowing venting to occur easily or sequentially, and that can prevent foreign substances from being introduced into the pouch-type battery cell during this process, as well as a pouch-type battery case sealing device for manufacturing the same. Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention has been made to solve the above problems, and aims to provide a pouch-type battery cell that can induce sequential venting and prevent the penetration of moisture and the like into the inside by dividing the sealing portion of the pouch-type battery cell so that there are differences in adhesive strength, and a pouch-type battery case sealing device for manufacturing the same. [Means for solving the problem]

[0015] To achieve this object, a pouch-type battery cell according to the present invention includes a pouch-type battery case made of a laminate sheet including a resin layer and a metal layer, and an electrode assembly housed in the pouch-type battery case. A sealing portion that is sealed by heat fusion is formed around the outer periphery of the electrode assembly housing portion. The sealing portion is formed so that pressing portions and non-pressing portions are repeatedly arranged from the inside to the outside of the pouch-type battery case, and the sealing force of the pressing portions may increase as they go outward from the pouch-type battery case.

[0016] When the internal pressure of the pouch-type battery case increases, the pressure parts may be sequentially released from the adhesive state from the inside to the outside of the pouch-type battery case.

[0017] The pouch-type battery case may include an inner resin layer, a metal layer, and an outer coating layer, and the thickness of the metal layer at the pressed portion may be thinner than the thickness of the metal layer at the non-pressed portion.

[0018] The thickness of the metal layer at the pressing portion of the sealing portion may decrease toward an outer side of the pouch-type battery case.

[0019] The present invention provides a pouch-type battery case sealing device for manufacturing the pouch-type battery cell, which includes a lower sealing member located at a lower part of the pouch-type battery case and an upper sealing member located at an upper part of the pouch-type battery case, and the upper sealing member includes a plurality of sealing tools spaced apart from each other and applying different pressure forces during sealing.

[0020] The plurality of sealing tools may be configured such that the magnitude of the pressing force increases as the sealing tools are disposed closer to the outside of the pouch-type battery case.

[0021] The temperatures of the sealing tools can be configured to be different from one another.

[0022] The temperature of the sealing tools may increase as they are disposed outside the pouch-type battery case.

[0023] The plurality of sealing tools may all have the same length.

[0024] The lower sealing member may have a flat upper surface facing the pouch-type battery case.

[0025] The lower sealing member may be heatable.

[0026] The plurality of sealing tools may be configured to sequentially press the pouch-type battery case from the sealing tool disposed inside the pouch-type battery case toward the sealing tool disposed outside the pouch-type battery case.

[0027] Each of the plurality of sealing tools may be divided into two or more regions along its entire length, and each region may be configured to be capable of independently adjusting at least one of a pressing temperature and a pressing force.

[0028] The plurality of sealing tools may have inclined pressing surfaces.

[0029] Furthermore, the present invention can also be provided in the form of various combinations of means for solving the above problems. [Effects of the Invention]

[0030] As described above, the present invention allows the venting of the sealing portion of the pouch-type battery cell to proceed sequentially from the inside to the outside, thereby accommodating an increase in the volume of the interior of the pouch-type battery case and preventing external substances from entering the interior of the pouch-type battery case.

[0031] In addition, the pressing temperature and pressing force of the multiple sealing tools that make up the upper sealing member are designed to increase from the inside to the outside of the pouch-type battery case, which reduces the size of the poly balls that are formed when the internal resin layer of the pouch-type battery case melts inside the pouch-type battery case, allowing the pouch-type battery case to bend even at low internal pressure. [Brief explanation of the drawings]

[0032] [Figure 1] 1 is a vertical cross-sectional view of a pouch-type battery case sealing device according to a first embodiment, when placed in a sealing portion of the pouch-type battery case. [Figure 2] 2 is a perspective view and a partially enlarged view of FIG. 1. [Figure 3] FIG. 10 is a perspective view of a pouch-type battery case sealing device according to a second embodiment. [Figure 4] 4A and 4B are perspective and partially enlarged views of a pouch-type battery cell sealed by the pouch-type battery case sealing device of FIG. 3. [Figure 5] 10 is a vertical cross-sectional view of a pouch-type battery case sealing device according to a third embodiment, when placed at a sealing portion of the pouch-type battery case. FIG. [Figure 6] 6 is a vertical cross-sectional view of a pouch-type battery cell sealing portion sealed by the pouch-type battery case sealing device of FIG. 5. FIG. [Figure 7] FIG. 10 is a perspective view of a pouch-type battery case sealing device according to a fourth embodiment. [Figure 8] 1A and 1B are diagrams showing poly balls in pouch-type battery cells according to examples and comparative examples. [Figure 9] 1 is a graph showing the results of measuring the adhesive strength of Sample 1. [Figure 10] 10 is a graph showing the results of measuring the adhesive strength of Sample 3. [Figure 11] 1 is a graph showing adhesive strength as a function of temperature. [Figure 12] 1 is a graph showing the change in adhesive strength between Samples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, with reference to the accompanying drawings, a detailed description will be given of an embodiment of the present invention that will enable a person skilled in the art to easily carry out the present invention. However, in describing the operation principle of the preferred embodiment of the present invention in detail, detailed description of related well-known functions or configurations will be omitted if it is determined that such detailed description may unnecessarily obscure the gist of the present invention.

[0034] Furthermore, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only a direct connection but also an indirect connection via another element therebetween. Furthermore, unless otherwise specified, "including a certain element" does not mean that other elements are excluded, but that other elements may also be included.

[0035] Furthermore, descriptions that limit or add specific elements are applicable to all inventions and are not limited to a particular invention unless otherwise specified.

[0036] Furthermore, throughout the description of the present invention and the claims, the singular includes the plural unless otherwise stated.

[0037] Furthermore, throughout the description of the present invention and the claims, unless otherwise specified, "or" includes "and." Therefore, "including A or B" means the three cases of including A, including B, or including both A and B.

[0038] The invention will now be explained with reference to the drawings and in conjunction with detailed embodiments.

[0039] FIG. 1 is a vertical cross-sectional view of a pouch-type battery case sealing device according to a first embodiment, placed at the sealing portion of a pouch-type battery case, and FIG. 2 is a perspective view and a partially enlarged view of FIG.

[0040] Referring to Figures 1 and 2, the sealing device for a pouch-type battery case according to the present invention includes a lower sealing member 300 located at the bottom of the pouch-type battery cases 110 and 120, and an upper sealing member 200 located at the top of the pouch-type battery cases 110 and 120, and the upper sealing member 200 includes a plurality of sealing tools with different pressure forces during sealing, and the plurality of sealing tools are arranged to be spaced apart from each other.

[0041] The multiple sealing tools shown in Figures 1 and 2 are composed of a first sealing tool 210, a second sealing tool 220, and a third sealing tool 230, and the three sealing tools are made of separate, individual members that are spaced apart from each other and can press against a pouch-type battery case.

[0042] The multiple sealing tools may be configured so that the magnitude of the pressing force increases in the order of the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230, and the gap between the upper sealing member 200 and the lower sealing member 300 gradually narrows as it goes toward the outside of the pouch-type battery case.

[0043] Therefore, the pouch-type battery cases 110 and 120 are pressed with a gradually increasing force toward the outside, so that the thickness can be gradually reduced.

[0044] For example, the pressure range of the sealing tools can be set within a range that will not damage the pouch-type battery case, specifically, 100 kgf (981 N) or less, more specifically, 20 kgf to 80 kgf (196 N to 785 N). Within this range, the pressure deviation between the first sealing tool 210 and the second sealing tool 220 and the pressure deviation between the second sealing tool 220 and the third sealing tool 230 can be set to be the same or different.

[0045] Meanwhile, the sealing tools can be set to different temperatures.

[0046] Specifically, the temperatures may be set to increase in the order of the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230. For example, the temperature range of the sealing tools may be set to a range in which the inner resin layer of the pouch-type battery case can melt, specifically, a range in which polypropylene, which is widely used as a material for the inner resin layer of pouch-type battery cases, can melt, which may be 130°C to 200°C, more specifically, 140°C to 180°C. Within this range, the temperature difference between the first sealing tool 210 and the second sealing tool 220 and the temperature difference between the second sealing tool 220 and the third sealing tool 230 may be set to be the same or different from each other.

[0047] That is, the temperature of the sealing tool increases as it is positioned closer to the outside of the pouch-type battery cases 110 and 120, and as a result, the degree of melting of the internal resin layer of the pouch-type battery case increases, and as a result, the adhesive strength between the pouch-type battery cases 110 and 120 can increase as it moves outward.

[0048] In this way, the upper sealing member 200 according to the present invention can individually set the pressure and temperature of each of the multiple sealing tools, so that the lengths H of the first sealing tool 210, the second sealing tool 220 and the third sealing tool 230 can all be configured to be the same.

[0049] That is, even if the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230 all have the same length H, the pressure and temperature can be set differently for each tool, so that when sealing a pouch-type battery case, a sealing portion with different sealing strength depending on the position can be formed.

[0050] The upper surface of the lower sealing member 300 facing the pouch-type battery cases 110 and 120 is flat, so that when multiple sealing tools set to different pressures and temperatures press the pouch-type battery case, the lower sealing member 300 can support the entire sealing portion of the pouch-type battery case.

[0051] In addition, the lower sealing member 300 can be configured to be heatable, so that the lower surfaces of the pouch-type battery cases 110 and 120 are heated to sufficiently melt the internal resin layer.

[0052] In particular, the temperature may be set within the temperature range of the upper sealing member 200. For example, the temperature may be set to the same temperature as the first sealing tool, which is the lowest temperature among the upper sealing members 200.

[0053] The multiple sealing tools can press sequentially from the first sealing tool 210 disposed inside the pouch-type battery case to the third sealing tool 230 disposed outside.

[0054] When the sealing part of the pouch-type battery case is pressed and heated, the inner resin layer in the sealing part melts and moves while being pushed inward and outward at both ends of the sealing part, and when it solidifies in this state, it becomes a round spherical mass, which is called a polyball in this specification.

[0055] The larger the size of the polyballs, the less likely venting of the pouch-type battery case occurs.

[0056] Therefore, in the present invention, by pressing the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230 in that order, the molten inner resin layer can be moved to the outside of the pouch-type battery case, thereby reducing the size of the poly ball formed inside the sealing part of the pouch-type battery case and thus reducing the pressure required to vent the pouch-type battery case.

[0057] 2 shows a state in which only one outer periphery of the pouch-type battery case is pressed by the sealing device for a pouch-type battery case according to the first embodiment, it goes without saying that any of the four outer periphery sealing portions of the pouch-type battery case can be sealed using the sealing device for a pouch-type battery case according to the first embodiment. This also applies to the sealing devices for pouch-type battery cases according to the third and fourth embodiments, which are configured in a linear shape.

[0058] FIG. 3 is a perspective view of a pouch-type battery case sealing device according to the second embodiment.

[0059] Referring to FIG. 3, the sealing device for a pouch-type battery case according to the second embodiment includes an upper sealing member 200 including a first sealing tool 210, a second sealing tool 220 and a third sealing tool 230, and a lower sealing member 300.

[0060] The first sealing tool 210, the second sealing tool 220, and the third sealing tool 230 are configured in the shape of a rectangular frame, and when they are all arranged to overlap, a gap is formed between the first sealing tool 210 and the second sealing tool 220, and a gap is also formed between the second sealing tool 220 and the third sealing tool 230.

[0061] That is, the pouch-type battery case is not directly pressed by the distance.

[0062] The first sealing tool 210, the second sealing tool 220, and the third sealing tool 230 sequentially press the pouch-type battery case from the first sealing tool 210 located inside the pouch-type battery case toward the third sealing tool 230 located outside, thereby moving the molten inner resin layer to the outside of the pouch-type battery case, thereby reducing the size of the poly balls formed inside the sealing portion of the pouch-type battery case and thus reducing the pressure required to vent the pouch-type battery case.

[0063] 4 is a perspective view and a partially enlarged view of a pouch-type battery cell sealed by the pouch-type battery case sealing device of FIG.

[0064] Referring to FIG. 4, a pouch-type battery cell according to the present invention includes a pouch-type battery case 110, 120 made of a laminate sheet including a resin layer and a metal layer, and an electrode assembly housed in the pouch-type battery case 110, 120. A sealing portion that is sealed by heat sealing is formed around the outer periphery of the electrode assembly housing portion. The sealing portion is formed so that pressed portions and non-pressed portions are repeatedly arranged from the inside to the outside of the pouch-type battery case, and the sealing force of the pressed portions increases as they go outward from the pouch-type battery case.

[0065] The pouch-type battery case includes an outer coating layer that has excellent resistance to the external environment, a metal layer that prevents the inflow of foreign matter such as gas or moisture or the leakage of electrolyte, and an inner resin layer that has heat-sealing properties.

[0066] The outer coating layer may comprise polyethylene terephthalate or oriented nylon, the metal layer may comprise aluminum or an aluminum alloy, and the inner resin layer may comprise polypropylene.

[0067] The pressing portion includes a first pressing portion 131, a second pressing portion 132, and a third pressing portion 133, and the non-pressing portion includes a first non-pressing portion 141 and a second non-pressing portion 142.

[0068] The first pressing portion 131, the second pressing portion 132, and the third pressing portion 133 are portions pressed by the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230, respectively, of the upper sealing member 200 of FIG.

[0069] When the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230 are set so that the pressing force and pressing temperature increase toward the outside of the pouch-type battery case, the adhesive force of the third pressing part 133 becomes the highest among the first pressing part 131, the second pressing part 132, and the third pressing part 133.

[0070] Therefore, when the internal pressure of the pouch-type battery cases 110, 120 increases, the adhesive state of the plurality of pressing parts is released sequentially from the inside of the pouch-type battery cases 110, 120, where adhesive strength is weak, to the outside, where adhesive strength is strong.

[0071] In detail, when the first pressing portion 131 is released, the internal space of the pouch-type battery case expands to the first non-pressing portion 141, thereby alleviating the increase in internal pressure. When the second pressing portion 132 is subsequently released, the internal space of the pouch-type battery case expands to the second non-pressing portion 142, thereby alleviating the increase in internal pressure. This prevents the pouch-type battery case from suddenly exploding due to an increase in internal pressure. At the same time, the third pressing portion 133 remains pressed, preventing external substances such as moisture from entering the pouch-type battery cell.

[0072] Furthermore, the second pressing portion 132 is thinner than the first pressing portion 131, and the third pressing portion 133 is thinner than the second pressing portion 132.

[0073] Here, the reduction in thickness of the first pressing part 131, the second pressing part 132, and the third pressing part 133 may be due to a reduction in the total thickness of the inner resin layer, the metal layer, and the outer coating layer, but more specifically, may be due to a reduction in the thickness of the metal layer.

[0074] That is, the thickness of the metal layer at the first pressing part 131, the second pressing part 132, and the third pressing part 133 of the sealing part of the pouch-type battery case may decrease toward the outside of the pouch-type battery case.

[0075] Therefore, the thickness of the metal layer at the third pressing part 133 can be thin to the extent that rigidity cannot be expected, and therefore, when the second pressing part 132 vents, the third pressing part 133 cannot maintain its adhesive state and is torn by the venting pressure, allowing the pouch-type battery case to be completely opened.

[0076] Meanwhile, the first non-pressed portion 141 and the second non-pressed portion 142 are portions that are not pressed by the upper sealing member, so the original thickness of the pouch-type battery case can be maintained. Therefore, the thickness of the metal layer at the first pressing portion 131, the second pressing portion 132, and the third pressing portion 133 is thinner than the thickness of the metal layer at the first non-pressed portion 141 and the second non-pressed portion 142.

[0077] FIG. 5 is a vertical cross-sectional view showing a pouch-type battery case sealing device according to a third embodiment, when placed at the sealing portion of the pouch-type battery case.

[0078] 5, the pouch-type battery case sealing device according to the third embodiment has inclined pressing surfaces of the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230. In FIG. 5, the inclination of the pressing surfaces is exaggerated for ease of explanation, and the difference between the longest length H and the shortest length of each sealing tool is smaller than the sum of the thicknesses of the pouch-type battery cases 110 and 120.

[0079] The left side of the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230, which has a longer length H, presses the pouch-type battery cases 110, 120 more strongly than the right side of the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230, which has a shorter length H. Therefore, the sealing portions of the pouch-type battery cases 110, 120 pressed by the left side of the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230 can have a higher sealing force than the sealing portions of the pouch-type battery cases 110, 120 pressed by the right side.

[0080] 6 is a vertical cross-sectional view of a pouch-type battery cell sealing portion sealed by the pouch-type battery case sealing device of FIG.

[0081] Referring to FIG. 6, the pressing portion includes a first pressing portion 131, a second pressing portion 132, and a third pressing portion 133, and the non-pressing portion includes a first non-pressing portion 141 and a second non-pressing portion 142.

[0082] The first pressing portion 131, the second pressing portion 132, and the third pressing portion 133 are portions pressed by the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230, respectively, of the upper sealing member 200 of FIG.

[0083] When the first sealing tool 210, the second sealing tool 220, and the third sealing tool 230 are set so that the pressing force and pressing temperature increase toward the outside of the pouch-type battery case, the adhesive force of the third pressing part 133 becomes the highest among the first pressing part 131, the second pressing part 132, and the third pressing part 133.

[0084] Therefore, when the internal pressure of the pouch-type battery cases 110, 120 increases, the adhesive state of the plurality of pressing parts is released sequentially from the inside to the outside of the pouch-type battery cases 110, 120.

[0085] The first pressing portion 131, the second pressing portion 132, and the third pressing portion 133 are pressed by an upper sealing member having an inclined pressing surface as shown in FIG. 5, and therefore, the thickness of each of the first pressing portion 131, the second pressing portion 132, and the third pressing portion 133 increases from the inside to the outside of the pouch-type battery case.

[0086] Therefore, the molten internal resin layer can move from the first pressing portion 131 to the first non-pressing portion 141, and then from the second pressing portion 132 to the second non-pressing portion 142, thereby reducing the size of the poly balls that occur inside the first pressing portion 131.

[0087] Additionally, the explanation regarding the thickness difference of the metal layer of the pouch-type battery case can be applied to the pouch-type battery cell shown in FIG. 4 and the pouch-type battery cell sealing portion shown in FIG. 6 in the same manner.

[0088] FIG. 7 is a perspective view of a pouch-type battery case sealing device according to a fourth embodiment.

[0089] Referring to FIG. 7, compared to the pouch-type battery case sealing device shown in FIG. 2, each of the multiple sealing tools constituting the upper sealing member 200 may be divided into two or more regions in the length direction L, and each region may be configured to be able to independently adjust at least one of the pressing temperature and pressing force.

[0090] In FIG. 7, the upper sealing member 200 has a first sealing tool 210 divided into a first region 211 and a second region 212, a second sealing tool 220 divided into a first region 221 and a second region 222, and a third sealing tool 230 divided into a first region 231 and a second region 232.

[0091] The first regions 211, 221, 231 may be configured to be externally integral with the second regions 212, 222, 232, or may be configured as separate structures that are physically separated from one another.

[0092] The first sealing tool 210, the second sealing tool 220, and the third sealing tool 230 can seal the pouch-type battery case sequentially, or either the first region 211, 221, 231 or the second region 212, 222, 232 can seal the pouch-type battery case first.

[0093] The present invention will be described below with reference to examples, but these are for easier understanding of the present invention and are not intended to limit the scope of the present invention.

[0094] Example 1 A pouch-type battery case including an outer coating layer, a metal layer, and an inner resin layer was prepared, and one outer periphery of the pouch-type battery case was pressed and heated using a pouch-type battery case sealing device shown in Figures 1 and 2.

[0095] Here, the pressing force and pressing temperature of the first sealing tool, second sealing tool, and third sealing tool were set as shown in Table 1 below, the temperature of the lower sealing member was set to 140°C, and pressing was performed in the order of the first sealing tool, second sealing tool, and third sealing tool.

[0096] [Table 1]

[0097] <Comparative Example> A pouch-type battery case similar to that of the example was prepared, and the pressing force was set to 40 kgf (392 N) against the upper sealing member and the lower sealing member, which had flat pressing surfaces, and the pressing temperature was set to 180°C, and the outer periphery of one side of the pouch-type battery case was pressed and heated.

[0098] FIG. 8 is a diagram showing the poly balls in the pouch-type battery cells according to the example and the comparative example.

[0099] 8, (a) shows the results of a comparative example, and (b) shows the results of an example, and it can be seen that when using a pouch-type battery case sealing device like the example, the size of the polyballs 400 is significantly reduced. Therefore, the pouch-type battery case 100 can be easily vented even at low pressure, which can prevent the pouch-type battery cell from exploding.

[0100] <Example 2> The electrode assembly was placed in a pouch-type battery case with a thickness of 71 μm, and the outer periphery of the pouch-type battery case was sealed to prepare a pouch-type battery cell.

[0101] The sealing conditions for the outer periphery of the pouch-type battery case were set to three conditions: 40 kgf (392 N) and 185°C for 2 seconds; 40 kgf (392 N) and 170°C for 2 seconds; and 40 kgf (392 N) and 150°C for 2 seconds. Five pouch-type battery cells were manufactured so that the thicknesses of the sealed portion of the pouch-type battery cells were 127 μm, 132 μm, and 137 μm, respectively. The one with a sealing thickness of 127 μm was designated Sample 1, the one with a sealing thickness of 132 μm was designated Sample 2, and the one with a sealing thickness of 137 μm was designated Sample 3.

[0102] <Analysis of the thickness of the internal resin layer of the sealing part and measurement of adhesive strength> The sealing portions of the pouch-type battery cells of Samples 1 and 3 were cut, and the thickness of the internal resin layer of the pouch-type battery cells was measured at the cut surface.

[0103] The average thickness of the internal resin layer of Sample 1 is 33.2 μm, and the average thickness of the internal resin layer of Sample 3 is 42.31 μm.

[0104] The adhesive strength of Sample 1 and Sample 3 was measured.

[0105] FIG. 9 is a graph showing the results of measuring the adhesive strength of Sample 1, and FIG. 10 is a graph showing the results of measuring the adhesive strength of Sample 3.

[0106] 9 and 10, the average adhesive strength of Sample 1 is 3.34 kgf (32.8 N), and the average adhesive strength of Sample 3 is 1.35 kgf (13.2 N).

[0107] Therefore, when the sealing forces of the sealing parts are configured to be different from each other as in the present invention, sample 1, in which the thickness of the inner resin layer is relatively thin, can be considered to correspond to the outer peripheral sealing part of the electrode assembly receiving part located toward the outside of the pouch-type battery case, and sample 3, in which the thickness of the inner resin layer is relatively thick, can be considered to correspond to the outer peripheral sealing part of the electrode assembly receiving part located toward the inside of the pouch-type battery case.

[0108] That is, it can be predicted that the thickness of the internal resin layer at the pressing portion will become thinner as one moves from the inside to the outside of the pouch-type battery case, and the adhesive strength will increase.

[0109] <Measurement of adhesive strength by temperature> A chamber for storing Samples 1 to 3 was prepared, set to a certain temperature, and then the samples were placed in. When the temperature of the chamber reached the set temperature, the adhesive strength was measured after waiting for 1 minute.

[0110] The constant temperatures are room temperature, 100°C, 110°C, 120°C and 130°C, respectively.

[0111] FIG. 11 is a graph showing the adhesive strength as a function of temperature, and FIG. 12 is a graph showing the change in the adhesive strength of Samples 1 to 3.

[0112] Referring to FIG. 11, (a) shows the highest adhesive strength values ​​by temperature during the adhesive strength measurement process, and (b) shows the average value of the section where the adhesive strength was stably measured.

[0113] Referring to FIG. 12, the adhesive strength of the sealing portion was measured at room temperature, 100°C, 110°C, 120°C and 130°C.

[0114] The adhesive strength was measured by measuring the adhesive strength over time while expanding the pouch-type battery case from the side where the polyballs were present. The section with the highest adhesive strength was the part where the polyballs were formed at the beginning of the adhesive strength measurement.

[0115] 11(a) and (b) show that the thicker the inner resin layer, the lower the adhesive strength, and the higher the chamber temperature, the lower the adhesive strength. Figure 12 shows that the maximum adhesive strength was measured at the part where the poly balls were formed at the beginning of the adhesive strength measurement under all temperature conditions.

[0116] That is, the highest adhesive strength was measured for Sample 1, which has a thin internal resin layer. Considering that the poly balls are formed larger in areas where the internal resin layer is thin, it can be seen that the adhesive strength increases as the size of the poly balls increases.

[0117] Therefore, when the thickness of the inner resin layer is formed to become thinner toward the outside of the pouch-type battery case by varying the pressing force of multiple sealing tools, it can be confirmed that the adhesive strength increases toward the outside of the pouch.

[0118] Furthermore, when sealing is performed sequentially from the inside to the outside of the sealing portion of the pouch-type battery case as in the present invention, the size of the poly balls formed inside the pouch-type battery case decreases, making it possible to provide a pouch-type battery cell with low adhesive strength at the sealing portion.

[0119] Those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above content. [Explanation of symbols]

[0120] 100, 110, 120 Pouch-type battery case 131 First pressing part 132 Second pressing part 133 Third pressing part 141 First non-pressing portion 142 second non-pressing portion 200 Upper sealing member 210 First Sealing Tool 220 Second sealing tool 230 Third Sealing Tool 300 Lower sealing member 400 Polyballs

Claims

1. a pouch-type battery case made of a laminate sheet including an inner resin layer, a metal layer, and an outer coating layer; and an electrode assembly housed in the pouch-type battery case, A sealing part is formed around the outer periphery of the electrode assembly receiving part, which is sealed by heat sealing. the sealing part is formed so that pressing parts and non-pressing parts are repeatedly arranged from the inside to the outside of the pouch-type battery case, The thickness of the inner resin layer at the pressing portion decreases toward the outside of the pouch-type battery case.

2. The pouch-type battery cell according to claim 1 , wherein when the internal pressure of the pouch-type battery case increases, the pressure portions are sequentially released from the adhesive state from the inside to the outside of the pouch-type battery case.

3. The pouch-type battery cell according to claim 1 , wherein the thickness of the metal layer in the pressed portion is thinner than the thickness of the metal layer in the non-pressed portion.

4. The pouch-type battery cell according to claim 3 , wherein the thickness of the metal layer at the pressing portion of the sealing portion decreases toward an outer side of the pouch-type battery case.

5. The pouch-type battery cell according to claim 1 , wherein the sealing force of the pressing portion increases toward the outside of the pouch-type battery case.

6. A pouch-type battery case sealing device for manufacturing the pouch-type battery cell according to any one of claims 1 to 5, comprising: a lower sealing member located at a lower portion of the pouch-type battery case, and an upper sealing member located at an upper portion of the pouch-type battery case; The upper sealing member includes a plurality of sealing tools spaced apart from each other and applying different pressure forces during sealing.

7. The pouch-type battery case sealing device according to claim 6 , wherein the pressure applied by the sealing tools increases as the sealing tools are disposed closer to the outside of the pouch-type battery case.

8. The pouch-type battery case sealing device according to claim 6 , wherein the temperatures of the plurality of sealing tools are different from each other.

9. The pouch-type battery case sealing device according to claim 6 , wherein the temperature of the sealing tools increases as they are disposed closer to the outside of the pouch-type battery case.

10. The pouch-type battery case sealing device according to claim 6 , wherein the plurality of sealing tools all have the same length.

11. The pouch-type battery case sealing device according to claim 6 , wherein the lower sealing member has a flat upper surface facing the pouch-type battery case.

12. The pouch-type battery case sealing device according to claim 11 , wherein the lower sealing member is heatable.

13. The pouch-type battery case sealing device according to claim 6 , wherein the plurality of sealing tools are configured to sequentially press the pouch-type battery case from a sealing tool disposed inside the pouch-type battery case toward a sealing tool disposed outside the pouch-type battery case.

14. 7. The pouch-type battery case sealing device according to claim 6, wherein each of the plurality of sealing tools is divided into two or more regions along its entire length, and each region is configured to be able to independently adjust at least one of a pressing temperature and a pressing force.

15. The pouch-type battery case sealing device according to claim 6 , wherein the plurality of sealing tools have inclined pressing surfaces.

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