Pouch cell and method for manufacturing the same

Abstract

The present invention relates to a pouch cell that can prevent cracks from occurring in the bridge portion of the pouch due to gases generated during charging or discharging, and a method for manufacturing the same. A method for manufacturing a pouch cell according to the present invention includes the step of (a) forming a pouch film including a metal layer such that a pair of cup portions capable of accommodating an electrode assembly are formed on both sides of a bridge portion in the pouch film, and in the step (a), the pouch film may be formed to satisfy the formula T / D>0.006, where T mm is the thickness of the metal layer of the bridge portion after forming, and D mm is the depth of the cup portions.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application Nos. 10-2022-0171495 filed on Dec. 9, 2022, 10-2023-0048848 filed on Apr. 13, 2023, and 10-2023-0175274 filed on Dec. 6, 2023, and all the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference in their entirety.

[0002] The present invention relates to a pouch cell and a method for manufacturing the same, and more particularly, to a secondary battery pouch cell capable of charging and discharging and a method for manufacturing the same.

Background Art

[0003] In recent years, due to the depletion of fossil fuels, the price of energy sources has increased, and the concern about environmental pollution has amplified. The need for environmentally friendly alternative energy sources has become an essential and indispensable factor for future life. Therefore, research on various power generation technologies such as solar power, wind power, and tidal power has continued, and there has also been a great deal of interest in power storage devices such as batteries for more efficiently using the electrical energy produced in this way.

[0004] Furthermore, as the technology development and demand for electronic mobile devices and electric vehicles using batteries increase, the demand for batteries as an energy source has increased rapidly. Along with this, many studies have been conducted on batteries that can meet various needs.

[0005] Batteries for storing electrical energy can generally be divided into primary batteries and secondary batteries. Primary batteries are disposable and consumable batteries, while secondary batteries are rechargeable batteries manufactured using materials in which the oxidation and reduction processes between current and substances can be repeated. That is, when a reduction reaction is performed on the material by current, the power source is charged, and when an oxidation reaction is performed on the material, the power source discharges, and electricity is generated while such charging and discharging are repeated.

[0006] Rechargeable batteries can be classified into cylindrical cells, pouch cells, prismatic cells, and other types depending on their form. Among these, pouch cells can include electrode assemblies in which a positive electrode, negative electrode, separator, etc., are stacked inside the pouch.

[0007] Generally, pouch cells can be manufactured in a form in which an electrode assembly is housed in the cup portion of a pouch film. Here, the cup portion can be formed by the process of molding the pouch film.

[0008] On the other hand, to increase energy density, pouch cells can be manufactured in which the cup portion of the pouch containing the electrode assembly is formed on both sides in the thickness direction of the pouch. Such pouch cells have a problem where cracks develop in the bridge portion formed between the two cup portions due to gases generated from within, causing damage to the bridge. Damage to the bridge can prevent the pouch cell from functioning properly.

[0009] Therefore, there is a need for a pouch cell and a method for manufacturing the same that can prevent damage to the bridge portion. [Overview of the project] [Problems that the invention aims to solve]

[0010] The object of the present invention is to provide a pouch cell and a method for manufacturing the same that prevent cracks from occurring in the bridge portion of the pouch due to gases generated during the charging or discharging process of the pouch cell, thereby improving safety. [Means for solving the problem]

[0011] A method for manufacturing a pouch cell according to the present invention includes the step of (a) forming a pouch film containing a metal layer such that a pair of cup portions capable of accommodating an electrode assembly are formed on both sides of a bridge portion, wherein in step (a), the pouch film can be formed such that the formula T / D > 0.006 is satisfied, where T is the thickness of the metal layer in the bridge portion after forming and D is the depth of the cup portions.

[0012] In step (a) above, the metal layer can be formed such that, after molding, the thickness of the metal layer in the bridge portion is 0.8 times or more the thickness of the metal layer before molding.

[0013] A method for manufacturing a pouch cell further includes (b) placing an electrode assembly in the cup portion and folding the pouch film with respect to the bridge portion so that the pair of cup portions cover the electrode assembly, and (c) sealing the outer edge of the folded pouch film, wherein in step (c), the sealing can be performed such that the shortest straight-line distance between the sealed portion and the cup portion is 0.5 mm or more and 1.5 mm or less.

[0014] A method for manufacturing a pouch cell further includes (b) placing an electrode assembly in the cup portion and folding the pouch film with respect to the bridge portion so that the pair of cup portions cover the electrode assembly, and (c) sealing the open portion of the folded pouch film, wherein step (c) may include (c-1) sealing the outer edge of the pouch film and (c-2) forming an additional sealing portion with a distance of 0.5 mm or more and 1.5 mm or less from the cup portion.

[0015] A method for manufacturing a pouch cell according to the present invention includes the step of (a) forming a pouch film containing a metal layer such that a pair of cup portions capable of accommodating an electrode assembly are formed on both sides of a bridge portion, wherein in step (a), the metal layer can be formed such that the thickness of the metal layer in the bridge portion is reduced by 20% or less.

[0016] The metal layer may include aluminum (Al).

[0017] The pouch cell according to the present invention includes an electrode assembly and a pouch having a metal layer and a shape in which both sides are folded with respect to a bridge portion so as to cover the electrode assembly, the pouch including a cup portion having a space for housing the electrode assembly inside, and the formula T / D > 0.006 can be satisfied when the thickness of the metal layer in the bridge portion is T mm and the depth of the cup portion is D mm.

[0018] The pouch includes a sealing portion that is positioned apart from the cup portion and sealed so as to isolate the electrode assembly from the outside, and the minimum distance between the cup portion and the sealing portion can be 0.5 mm or more and 1.5 mm or less.

[0019] The sealing portion further includes an outer sealing portion disposed at a predetermined distance from the cup portion, and an additional sealing portion disposed between the outer sealing portion and the cup portion, wherein the distance between the additional sealing portion and the cup portion can be 0.5 mm or more and 1.5 mm or less.

[0020] The pouch cell may be configured such that the bridge portion is formed at one end of the cup portion, and the additional sealing portion is positioned such that one end lies on the same line as one end of the cup portion.

[0021] The additional sealing portion may have a shape in which its width gradually decreases as it approaches the cup portion from the outer sealing portion.

[0022] The pouch can be such that the thickness of the metal layer of the bridge portion is 0.8 times or more the thickness of the metal layer of the seal portion.

Advantages of the Invention

[0023] The method for manufacturing a pouch cell according to the present invention includes the step of forming a pair of cup portions in a pouch film including a metal layer, and in the step (a), when the thickness of the metal layer of the formed cup portion is T mm and the depth of the cup portion is D mm, the pouch film can be formed so as to satisfy the mathematical formula of T / D > 0.006.

[0024] Thereby, it is possible to prevent cracks from occurring in the bridge portion of the pouch due to gas or the like generated during the charging or discharging process.

[0025] In addition, the efficiency of the manufacturing process of the pouch cell can be improved.

[0026] In addition, by preventing damage to the bridge portion of the pouch, the safety of the pouch cell can be improved.

[0027] The effects according to the present invention are not limited by the contents exemplified above, and various other effects are included in this specification.

Brief Description of the Drawings

[0028] [Figure 1] It is a flowchart schematically showing a method for manufacturing a pouch cell according to an embodiment of the present invention. [Figure 2] It is a perspective view schematically showing a pouch cell according to an embodiment of the present invention. [Figure 3] It is a front view schematically showing a state in which cracks have occurred in a pouch cell according to a comparative example of the present invention. [Figure 4] It is a perspective view schematically showing a pouch film according to an embodiment of the present invention. [Figure 5]This is a schematic plan view illustrating the top-down view of the sealing portion of a pouch cell according to one embodiment of the present invention. [Figure 6] This is a schematic plan view illustrating the top-down view of the sealing portion of a pouch cell according to another embodiment of the present invention. [Figure 7] This is a schematic plan view illustrating the top-down view of the sealing portion of a pouch cell according to yet another embodiment of the present invention. [Modes for carrying out the invention]

[0029] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings, so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention can be realized in a variety of different forms and is not limited or restricted by the following embodiments.

[0030] For the purpose of clearly describing the present invention, detailed descriptions of related known technologies that are irrelevant to the description or that could obscure the gist of the invention have been omitted. In this specification, when assigning reference numerals to components in each drawing, the same or similar reference numerals are used throughout the specification for components that are the same or similar.

[0031] Furthermore, the terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0032] Manufacturing method of pouch cells Figure 1 is a flowchart schematically illustrating a method for manufacturing a pouch cell according to one embodiment of the present invention, and Figure 2 is a perspective view schematically illustrating a pouch cell 10 according to one embodiment of the present invention.

[0033] A method for manufacturing a pouch cell according to one embodiment of the present invention can be a method for manufacturing a rechargeable and dischargeable secondary battery. Specifically, the method for manufacturing a pouch cell can be a method for manufacturing a pouch cell 10 in which an electrode assembly is arranged inside a pouch 100.

[0034] Referring to Figure 1, a method for manufacturing a pouch cell according to one embodiment of the present invention may include the step (S1) of forming a pouch film 100-1 containing a metal layer 102 such that a pair of cup portions 110 are formed on the pouch film 100-1. Hereinafter, this step will be referred to as step (a).

[0035] Referring to Figure 2, a pouch cell 10 manufactured by a pouch cell manufacturing method according to one embodiment of the present invention may have an electrode assembly including a negative electrode, a positive electrode, and a separator arranged inside a pouch 100. Here, the pouch 100 may be arranged in a manner that encloses the electrode assembly. Specifically, the pouch cell 10 may mean a secondary battery in which an electrode assembly including a negative electrode, a positive electrode, and a separator is housed inside a pouch 100 together with an electrolyte.

[0036] On the other hand, the electrode assembly can have a form in which a negative electrode, a positive electrode, and a separator are stacked or in the form of a wound jelly roll, and the pouch 100 can accommodate the electrode assembly. The pouch 100 may also include a cup portion 110 molded to contain the electrode assembly and the electrolyte inside. Herein, in step (a) of the method for manufacturing a pouch cell according to one embodiment of the present invention, the cup portion 110 can be molded into the pouch film 100-1.

[0037] The pouch film 100-1 to be formed can be a film in which multiple layers having different properties from each other are laminated. Here, the pouch film 100-1 may include a metal layer 102.

[0038] A pouch film 100-1 containing a metal layer 102 can have a cup portion 110 formed on it by a pouch molding apparatus or the like. Here, the form of the pouch molding apparatus can vary. For example, the pouch molding apparatus includes a punch and a die, and the punch can pressurize the pouch film 100-1 placed on the die to form the cup portion 110.

[0039] Referring to Figure 2, the cup portion 110 of the pouch 100 can have a space formed inside to accommodate the electrode assembly and electrolyte. On the other hand, there can be various forms in which the pouch cell is manufactured. For example, a pouch cell can be manufactured by joining two pouch films, each with a cup portion formed thereon, so as to face each other, or by folding a pouch film with a pair of cup portions formed thereon to form a space between the pair of cup portions in which the electrode assembly is accommodated. A method for manufacturing a pouch cell according to one embodiment of the present invention will be explained using as an example a method in which a pouch film with a pair of cup portions formed thereon is folded to form a space between the pair of cup portions in which the electrode assembly is accommodated.

[0040] Therefore, the pouch film 100-1 used in a method for manufacturing a pouch cell according to one embodiment of the present invention can be molded so that a pair of cup portions 110 are formed. Here, the pair of cup portions 110 can be formed on both sides of a bridge portion 130. That is, a bridge portion 130 can be provided between the pair of cup portions 110. The pouch film 100-1 can be folded to form a space between the pair of cup portions 110 facing each other in which an electrode assembly can be accommodated. Here, the pouch film 100-1 can be folded with respect to the bridge portion 130.

[0041] As described above, the bridge portion 130 can be formed between a pair of cup portions 110. Therefore, after the pouch film 100-1 is folded, the bridge portion 130 can be formed at one end of the cup portion 110.

[0042] Figure 3 is a schematic front view illustrating a state in which a crack has occurred in a pouch cell according to a comparative example of the present invention.

[0043] Referring to Figure 3, conventional pouch cells manufactured by folding a pouch film with a pair of cup sections formed into it have cracks occurring in the section used as the folding reference. Specifically, when folding based on the bridge section 130, cracks occur in the bridge section 130 of the pouch 100. In connection with this, the pouch cell 10 undergoes repeated charging and discharging, which can generate gas inside the pouch 100. The gas inside the pouch 100 applies pressure to the pouch 100, which can cause cracks to occur in the bridge section 130, which is relatively less rigid. In other words, the gas increases the pressure inside the pouch 100, and this increased pressure can cause cracks to occur in the bridge section 130, which is relatively brittle to pressure.

[0044] Furthermore, cracks may occur in the bridge portion 130 during the manufacturing process of the pouch cell 10. For example, cracks may occur in the bridge portion 130 due to gas generated inside the pouch during the activation process. In addition, cracks in the bridge portion 130 may occur during the manufacturing process of the pouch cell 10 due to various physical factors.

[0045] Figure 4 is a schematic perspective view illustrating pouch film 100-1 according to one embodiment of the present invention.

[0046] The pouch film 100-1 used in the manufacturing method of a pouch cell according to one embodiment of the present invention may include multiple layers. For example, the pouch film 100-1 may include an inner layer 101, a metal layer 102, and an outer layer 103.

[0047] The pouch film 100-1 used in the manufacture of the pouch cell 10 of the present invention will be described in detail.

[0048] Referring to Figure 4, the pouch film 100-1 may include an inner layer 101, a metal layer 102, and an outer layer 103, and may optionally further include a stretching aid layer.

[0049] The inner layer 101 is made of polymer and is formed on the innermost layer so that it can directly contact the electrode assembly. Here, "innermost layer" may mean the last layer when viewed from the outer layer 103 toward the electrode assembly.

[0050] The polymer used to manufacture the inner layer 101 can consist of one or more substances selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, poly(p-phenylenebenzobisoxazole), polyarylate, Teflon®, and glass fibers. In particular, polyolefin resins such as polypropylene (PP) or polyethylene (PE) are mainly used. Polypropylene (PP) is excellent in mechanical properties such as tensile strength, rigidity, surface hardness, abrasion resistance, and heat resistance, as well as chemical properties such as corrosion resistance, and is mainly used to manufacture the inner layer 101. Furthermore, it can also consist of unoriented polypropylene (Cated Polypropylene), acid-modified polypropylene, or polypropylene-butylene-ethylene ternary copolymer. Here, acid-modified polypropylene can be MAH PP (Malayic anhydride polypropylene). Furthermore, the inner layer 101 may have a single film structure composed of any one of the materials, or a composite film structure formed by two or more materials each forming a layer.

[0051] On the other hand, the pouch film 100-1 used in the manufacturing method of pouch cells may have an inner layer thickness of 30 μm to 100 μm, preferably 40 μm to 90 μm, and particularly 50 μm to 85 μm.

[0052] The metal layer 102 ensures the mechanical strength of the pouch 100, blocks the inflow and outflow of gases or moisture from the outside of the pouch cell 10, and prevents leakage of the electrolyte.

[0053] The metal layer 102 may include, but is not limited to, a metal selected from the group consisting of copper (Cu), aluminum (Al), nickel (Ni), iron (Fe), carbon (C), chromium (Cr), manganese (Mn), and alloys containing two or more of these. Preferably, the metal layer 102 may include a metal selected from aluminum alloys and stainless steel (SUS).

[0054] Aluminum alloys and stainless steel can ensure mechanical strength above a certain level while being lightweight. Furthermore, aluminum alloys and stainless steel can complement the electrochemical properties of electrode assemblies and electrolytes, and ensure heat dissipation.

[0055] Aluminum alloys can contain a variety of materials. For example, they can contain one or more materials selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), and zinc (Zn).

[0056] The metal layer 102 may be a single layer or a multilayer structure. For example, a multilayer metal layer 102 may consist of an aluminum alloy layer and a stainless steel layer.

[0057] On the other hand, the pouch film 100-1 used in the manufacturing method of pouch cells may have a metal layer 102 thickness of 20 μm to 100 μm, preferably 40 μm to 80 μm, and particularly 50 μm to 70 μm.

[0058] The outer layer 103 is made of polymer, is formed on the outermost surface, protects the pouch cell 10 from friction and impact with the outside, and electrically insulates the electrode assembly from the outside. Here, the outermost layer may mean the last layer as it moves away from the electrode assembly relative to the inner layer 101.

[0059] The polymer used to produce the outer layer 103 can be one or more substances selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, poly(p-phenylenebenzobisoxazole), polyarylate, Teflon, and glass fiber. In particular, it is preferable to use polymers such as polyethylene terephthalate (PET) that have abrasion resistance and heat resistance. The outer layer 103 may have a single film structure made of any one of these substances, or a composite film structure formed by two or more substances each forming a layer.

[0060] On the other hand, the pouch film 100-1 used in the manufacturing method of pouch cells may have an outer layer thickness of 5 μm to 25 μm, preferably 6 μm to 20 μm, and particularly 7 μm to 15 μm.

[0061] The pouch film 100-1 used in the manufacture of the pouch cell 10 may further include a stretching auxiliary layer positioned between the metal layer 102 and the outer layer 103.

[0062] The stretching auxiliary layer is made of polymer and can prevent the metal layer 102 and the outer layer 103 from peeling off when they are stretched.

[0063] The polymer used to produce the stretching auxiliary layer can be one or more substances selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, poly(p-phenylenebenzobisoxazole), polyarylate, Teflon, and glass fiber. In particular, nylon resin readily adheres to the polyethylene terephthalate (PET) of the outer layer 103 and exhibits similar behavior to the aluminum alloy of the metal layer 102 when stretched. Therefore, nylon resin can be mainly used as the polymer for producing the stretching auxiliary layer. Furthermore, the stretching auxiliary layer may have a single film structure composed of any one of these substances, or a composite film structure formed by two or more substances each forming a layer.

[0064] On the other hand, the pouch film 100-1 used in the manufacturing method of pouch cells may have a stretching auxiliary layer thickness of 15 μm to 50 μm, preferably 25 μm to 45 μm, and particularly 25 μm to 40 μm.

[0065] The thickness of the pouch film 100-1, including the inner layer 101, the metal layer 102, the outer layer 103, and the stretching auxiliary layer, can be selected within an appropriate range depending on the application of the pouch cell. For example, the thickness of the pouch film 100-1 can be 70 μm to 275 μm, 90 μm to 250 μm, or 100 μm to 220 μm.

[0066] As an example of a method to prevent cracks from occurring in the bridge portion 130, in step (a) of the method for manufacturing a pouch cell according to one embodiment of the present invention, the pouch film 100-1 can be molded such that the formula T / D > 0.006 is satisfied when the thickness of the metal layer 102 of the bridge portion 130 after molding is T mm and the depth of the cup portion 110 is D mm.

[0067] When the cup portion 110 is formed on the pouch film 100-1, the thickness of the portion where the cup portion 110 is formed and the bridge portion 130 provided between the pair of cup portions 110 may be reduced. Consequently, the thickness of the metal layer 102 of the pouch film 100-1 that forms the cup portion 110 and the metal layer 102 of the pouch film 100-1 that forms the bridge portion 130 may also be reduced. In this regard, in the formula T / D > 0.006, T may represent the thickness of the metal layer 102 of the bridge portion 130 that has been reduced after forming.

[0068] Referring to Figure 4, after molding, the cup portion 110 can have depth. Here, through experimentation, a formula can be obtained for the conditions under which cracks can be prevented from occurring in the bridge portion 130 of the pouch 100. The experiment was conducted at various molding depths, and this formula can be expressed as a relationship between the depth D to which the cup portion 110 is molded and the thickness T of the metal layer of the bridge portion 130 after molding. In other words, this relationship can be a condition for preventing cracks from occurring in the bridge portion 130 of the pouch 100.

[0069] The specific experimental results can be seen in Tables 1 and 2 below.

[0070] [Table 1]

[0071] [Table 2]

[0072] Referring to Table 1, it can be confirmed that when the T / D value exceeds 0.006, no cracks occur in the bridge portion 130. On the other hand, referring to Table 2, when the T / D value is less than 0.006, repeated charging and discharging of the pouch cell 10 occurs, causing cracks to occur in the bridge portion 130. Cracks also occur when the T / D value is 0.006. As an example of a method to prevent cracks from occurring in the bridge portion 130, in step (a) of the method for manufacturing a pouch cell according to one embodiment of the present invention, the metal layer can be formed such that the thickness T of the metal layer 102 of the bridge portion 130 after molding is 0.8 times or more the thickness of the metal layer before molding. That is, the thickness T of the metal layer 102 of the bridge portion 130 after molding can be 80% or more and 100% or less the thickness of the metal layer before molding.

[0073] As described above, during the process of forming the cup portion 110 on the pouch film 100-1, the thickness of the metal layer 102 of the cup portion 110 and the bridge portion 130 may decrease. Here, if the thickness T of the metal layer 102 of the bridge portion 130 after forming is 80% or more of the thickness before forming, no cracks occurred in the bridge portion 130 of the pouch cell 10. Here, 80% can be a value obtained through repeated experiments.

[0074] On the other hand, in order to prevent crack formation in the bridge portion 130, in step (a) of the method for manufacturing the pouch cell, the metal layer 102 of the metal layer 102 of the cup portion side portion 111 after molding can be formed to be 0.8 times or more the thickness of the metal layer before molding. That is, the thickness of the metal layer 102 of the cup portion side portion 111 after molding can be 80% to 100% of the thickness of the metal layer before molding. Here, the cup portion side portion 111 can mean the portion surrounding the side of the cup portion 110 so as to form a space provided in the cup portion 110 for housing the electrode assembly (see Figure 4).

[0075] The process of forming the cup portion 110 on the pouch film 100-1 can cause a significant relative change in the thickness of the bridge portion 130 and the cup portion side portion 111. In this regard, a method for manufacturing a pouch cell according to one embodiment of the present invention allows for setting the change in the thickness of the metal layer of the bridge portion 130 and the cup portion side portion 111. This effectively prevents cracks from occurring in the bridge portion 130 of the completed pouch cell 10.

[0076] A method for manufacturing a pouch cell according to one embodiment of the present invention may further include the step (S2) of placing an electrode assembly in the cup portion 110 and folding the pouch film 100-1 between the pair of cup portions 110 such that the pair of cup portions 110 cover the electrode assembly. Specifically, the pouch film 100-1 can be folded with respect to the bridge portion 130. The method may further include the step (S3) of sealing the outer edge of the folded pouch film 100-1 (see Figure 1). Hereinafter, the sealing step will be referred to as step (c).

[0077] Figure 5 is a schematic plan view illustrating the seal portion 120 of the pouch cell 10 according to one embodiment of the present invention, as seen from above.

[0078] As an example of a method to more efficiently prevent cracks from occurring in the bridge portion 130, in step (c) of the method for manufacturing a pouch cell according to one embodiment of the present invention, the seal portion 120 and the cup portion 110 can be sealed such that the shortest straight-line distance L is 0.5 mm or more and 1.5 mm or less. Here, the seal portion 120 may mean the sealed portion.

[0079] On the other hand, the shape of the pouch film 100-1 when viewed from above can be approximately rectangular. When the pouch film 100-1 is folded with respect to the bridge portion 130, three places can be opened in addition to the part where the bridge portion 130 is formed. Specifically, there can be three corners that are sealed by a seal. In step (c), the three corners can be sealed so that the electrode assembly housed in the cup portion 110 can be sealed from the outside.

[0080] In this regard, in step (c), the sealing can be performed such that the shortest straight distance L between the sealing portion 120 and the cup portion 110 is 0.5 mm or more and 1.5 mm or less. Specifically, when sealing the corners formed on both sides of the bridge portion 130, in addition to the corner formed on the opposite side of the bridge portion 130 with respect to the cup portion 110, the sealing can be performed such that the shortest straight distance L between the sealing portion 120 and the cup portion 110 is 0.5 mm or more and 1.5 mm or less. Preferably, in step (c), the sealing can be performed such that the shortest straight distance L between the sealing portion 120 and the cup portion 110 is 1 mm or less.

[0081] A pouch cell 10 sealed such that the distance L between the cup portion 110 and the seal portion 120 is between 0.5 mm and 1.5 mm can prevent cracking of the bridge portion 130. Here, the numerical value related to the distance can be a value obtained through repeated experiments.

[0082] Experiments showed that in pouch cells 10 where the distance L between the cup portion 110 and the seal portion 120 was between 0.5 mm and 1.5 mm, no cracks occurred in the bridge portion 130 even under relatively high pressure. Therefore, in pouch cells 10 according to one embodiment of the present invention, the phenomenon of damage such as cracks occurring in the bridge portion 130 can be delayed or prevented.

[0083] Figure 6 is a schematic plan view illustrating the seal portion 120 of the pouch cell 10 according to another embodiment of the present invention, as seen from above.

[0084] A method for manufacturing a pouch cell according to another embodiment of the present invention may further include the step of placing an electrode assembly in a cup portion 110 and folding the pair of cup portions 110 so that the pair of cup portions 110 cover the electrode assembly. It may also further include the step of sealing the open portion of the folded pouch film 100-1. Hereinafter, the sealing step will be referred to as step (c).

[0085] As an example of a method to more efficiently prevent cracks from occurring in the bridge portion 130, step (c) of the method for manufacturing a pouch cell according to another embodiment of the present invention may include steps (c-1) and (c-2). Here, step (c-1) may be a step of sealing the outer edge of the pouch film 100-1, and step (c-2) may be a step of forming an additional sealing portion 122 such that the gap L between the folded portion and the pair of cup portions 110 is 0.5 mm or more and 1.5 mm or less. Here, the outer edge of the pouch film 100-1 may mean the remaining outer part of the cup portion 110 other than one end that has been folded and sealed.

[0086] In step (c) of the method for manufacturing pouch cells, step (c-2) may be performed after step (c-1), or steps (c-1) and (c-2) may be performed simultaneously.

[0087] Referring to Figure 6, the seal portion 120 of a pouch cell 10 manufactured by a method for manufacturing a pouch cell according to another embodiment of the present invention may include an outer seal portion 121 and an additional seal portion 122. Here, the outer seal portion 121 may be positioned further away from the cup portion 110 relative to the additional seal portion 122, and the additional seal portion 122 may be positioned between the outer seal portion 121 and the cup portion 110. The outer seal portion 121 can be formed by step (c-1), and the additional seal portion 122 can be formed by step (c-2).

[0088] Experiments have shown that the entire seal portion 120 does not need to form a gap of 0.5 mm to 1.5 mm between it and the cup portion 110. In other words, if the gap L between the bridge portion 130 where cracks occur and the seal portion 120 is 0.5 mm to 1.5 mm, the occurrence of cracks can be prevented. Therefore, in order to satisfy these conditions and reduce the portion that is sealed, step (c) of the method for manufacturing a pouch cell according to other embodiments of the present invention may include step (c-2).

[0089] Referring to Figure 6, the additional sealing portion 122 can be formed on the same line as one end of the cup portion 110 on which the bridge portion 130 is formed. Furthermore, the length of the additional sealing portion 122 can be shorter than the length of the outer sealing portion 121. Therefore, a relatively large space can be left unsealed between the outer sealing portion 121 and the cup portion 110. Because the unsealed space is relatively large, additional processes such as welding the electrode assembly and electrode leads can be carried out efficiently.

[0090] Figure 7 is a schematic plan view illustrating the seal portion 120 of the pouch cell 10 according to yet another embodiment of the present invention, as seen from above.

[0091] Referring to Figure 7, a method for manufacturing a pouch cell according to yet another embodiment of the present invention can be used to manufacture a pouch cell such that the additional sealing portion 122 has a shape in which its width gradually decreases as it approaches the cup portion 110 from the outer sealing portion 121.

[0092] As the width of the additional sealing portion 122 gradually decreases as it approaches the cup portion 110 from the outer sealing portion 121, the area of ​​the unsealed portion between the outer sealing portion 121 and the cup portion 110 can be increased. Therefore, processes in which the unsealed portion is used can be carried out more efficiently.

[0093] Even if the method for manufacturing the pouch cell includes only one of the features of the method for manufacturing the pouch cell that prevents cracks from occurring in the bridge portion 130 described above, it is still possible to delay or prevent cracks from occurring in the bridge portion 130. However, in order to more efficiently prevent cracks from occurring in the bridge portion 130, the method for manufacturing the pouch cell may include all of the features described above.

[0094] Pouch Cell A pouch cell 10 according to one embodiment of the present invention may mean a rechargeable and dischargeable secondary battery in which an electrode assembly is arranged inside a pouch 100.

[0095] A pouch cell 10 according to one embodiment of the present invention may have an electrode assembly including a negative electrode, a positive electrode, and a separator arranged inside a pouch 100 (see Figure 2). Here, the pouch 100 may be arranged in a manner that encloses the electrode assembly. Specifically, the pouch cell 10 may mean a secondary battery in which an electrode assembly including a negative electrode, a positive electrode, and a separator is housed together with an electrolyte inside a pouch 100.

[0096] A pouch cell 10 according to one embodiment of the present invention may include an electrode assembly and a pouch 100. The pouch 100 may include a metal layer 102 and have a shape in which both sides are folded with respect to a bridge portion 130 so as to cover the electrode assembly. The pouch 100 may also include a cup portion 110 for housing the electrode assembly.

[0097] As an example of a configuration to prevent cracks from occurring in the bridge portion 130, the pouch 100 of the pouch cell 10 according to one embodiment of the present invention can satisfy the formula T / D > 0.006 when the thickness of the metal layer 102 of the bridge portion 130 is T mm and the depth of the cup portion 110 is D mm.

[0098] In this regard, the pouch cell 10 undergoes repeated charging and discharging, which can generate gas inside the pouch 100. The gas inside the pouch 100 can put pressure on the pouch 100, potentially causing cracks to form in the relatively less rigid bridge portion 130. In other words, the gas increases the pressure inside the pouch 100, and this increased pressure can cause cracks to form in the relatively pressure-vulnerable bridge portion 130.

[0099] A pouch cell 10 containing a pouch 100 that satisfies the formula T / D > 0.006, where T is the thickness of the metal layer 102 of the bridge portion 130 and D is the depth of the cup portion 110, can prevent cracks from occurring in the bridge portion 130.

[0100] The pouch 100 of the pouch cell 10 may include a cup portion 110 and a sealing portion 120.

[0101] As an example of another configuration to prevent cracking of the bridge portion 130, in the pouch 100 of the pouch cell 10 according to one embodiment of the present invention, the thickness T of the metal layer 102 of the bridge portion 130 can be 0.8 times or more the thickness T' of the metal layer 102' of the seal portion 120.

[0102] In this regard, the thickness of the multiple layers constituting the pouch 100 may change depending on the manufacturing process of the pouch cell 10. Furthermore, the thickness of the layers may change depending on the part of the pouch 100. For example, the thicknesses of the inner layer 101, metal layer 102, and outer layer 103 of the bridge portion 130 may differ from the thicknesses of the inner layer 101', metal layer 102', and outer layer 103' of the seal portion 120.

[0103] Since the bridge portion 130 is provided between the pair of cup portions 110, it can be affected by the molding of the cup portions 110 during the manufacturing process of the pouch 100. On the other hand, the seal portion 120 can be unaffected by the molding during the manufacturing process of the pouch 100. Therefore, the thickness of the metal layer 102 of the bridge portion 130 can change during the manufacturing process, while the thickness of the metal layer 102' of the seal portion 120 can hardly change during the manufacturing process. Here, a difference in thickness may occur between the metal layer 102 of the bridge portion 130 and the metal layer 102' of the seal portion 120.

[0104] Results obtained from repeated experiments show that if the thickness T of the metal layer 102 of the bridge portion 130 is 0.8 times or more the thickness T' of the metal layer 102' of the seal portion 120, no cracks will occur in the bridge portion 130 of the pouch 100. In other words, the thickness T of the metal layer 102 of the bridge portion 130 in which no cracks occur in the bridge portion 130 of the pouch 100 can be 80% to 100% of the thickness T' of the metal layer 102' of the seal portion 120. As an example of an additional configuration to more efficiently prevent cracks from occurring in the bridge portion 130, the pouch 100 of the pouch cell 10 according to one embodiment of the present invention can have a minimum distance L between the cup portion 110 and the seal portion 120 that is 0.5 mm or more and 1.5 mm or less. Preferably, the pouch 100 of the pouch cell 10 can have a minimum distance L between the cup portion 110 and the seal portion 120 that is 1.0 mm or less. This value can be a value obtained through experimentation.

[0105] If the seal portion 120 of the pouch 100 is formed with a separation of 0.5 mm to 1.5 mm from the cup portion 110, it is possible to prevent cracks from occurring in the bridge portion 130 due to the pressure of the gas inside the pouch 100. Furthermore, even if stronger pressure is applied to the pouch 100, damage to the bridge portion 130 can be delayed or prevented.

[0106] Figure 6 is a schematic plan view illustrating the seal portion 120 of the pouch cell 10 according to another embodiment of the present invention, as seen from above.

[0107] Referring to Figure 6, the sealing portion 120 of the pouch 100 according to another embodiment of the present invention may include an outer sealing portion 121 and an additional sealing portion 122. Specifically, the outer sealing portion 121 of the sealing portion 120 may be positioned at a predetermined distance from the cup portion 110, and the additional sealing portion 122 may be positioned between the outer sealing portion 121 and the cup portion 110. That is, the outer sealing portion 121 may be positioned at an even greater distance from the cup portion 110 relative to the additional sealing portion 122.

[0108] Here, as an example of a configuration to more efficiently prevent cracks from occurring in the bridge portion 130, in another embodiment of the present invention, the pouch cell 10 can have a distance L between the additional seal portion 122 and the cup portion 110 that is 0.5 mm or more and 1.5 mm or less.

[0109] In another embodiment of the present invention, the pouch cell 10 can have a wider unsealed space between the cup portion 110 and the seal portion 120 compared to the pouch cell 10 of one embodiment of the present invention. Therefore, it is possible to prevent the occurrence of cracks in the bridge portion 130 and to carry out processes such as welding the electrode assembly and electrode leads more efficiently.

[0110] On the other hand, the bridge portion 130 of the pouch 100 can be formed at one end of the cup portion 110. Here, one end of the cup portion 110 may mean the right end of the cup portion 110 with reference to Figure 6.

[0111] In another embodiment of the present invention, the pouch cell 10 can be arranged such that the additional sealing portion 122 is collinear with one end of the cup portion 110. That is, the additional sealing portion 122 can be arranged to be in contact with one end of the outer sealing portion 121. Here, a wider space is formed between the part of the outer sealing portion 121 that is not in contact with the additional sealing portion 122 and the cup portion 110, and other processes that utilize this space can be carried out more efficiently.

[0112] Figure 7 is a schematic plan view illustrating the seal portion 120 of the pouch cell 10 according to yet another embodiment of the present invention, as seen from above.

[0113] Referring to Figure 7, the additional sealing portion 122 according to yet another embodiment of the present invention may have a shape in which the width gradually decreases as it approaches the cup portion 110 from the outer sealing portion 121. Here, the degree to which the width decreases can vary, and the shape of the additional sealing portion 122 can vary.

[0114] If the additional sealing portion 122 has a shape in which its width gradually decreases as it approaches the cup portion 110 from the outer sealing portion 121, a wider unsealed portion can be formed between the cup portion 110 and the outer sealing portion 121. Therefore, the efficiency of the unsealed portion can be further improved.

[0115] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible by persons with ordinary skill in the art to which the present invention pertains, within the equivalent scope of the technical concept of the present invention and the claims described below. [Explanation of symbols]

[0116] 10 pouch cells 100 pouches 100-1 Pouch Film 101 Inner layer 102 Metal layer 103 Outer layer 110 cup section 111 Side of the cup 120 Seal part 121 Outer seal section 122 Additional sealing section 130 Bridge section

Claims

1. (a) The step of forming the pouch film containing a metal layer such that a pair of cup portions capable of housing the electrode assembly are formed on both sides of the bridge portion, In step (a) above, A method for manufacturing a pouch cell, wherein the pouch film is formed such that the formula T / D > 0.006 is satisfied when the thickness of the metal layer in the bridge portion after molding is T mm and the depth of the cup portion is D mm.

2. In step (a) above, The method for manufacturing a pouch cell according to claim 1, wherein, after molding, the metal layer is molded such that the thickness of the metal layer in the bridge portion is 0.8 times or more the thickness of the metal layer before molding.

3. (b) The step of placing the electrode assembly in the cup portion and folding the pouch film with respect to the bridge portion so that the pair of cup portions cover the electrode assembly, (c) further includes the step of sealing the outer edge of the folded pouch film, In step (c) above, A method for manufacturing a pouch cell according to claim 1 or 2, wherein the seal is made such that the shortest straight-line distance between the sealed portion and the cup portion is 0.5 mm or more and 1.5 mm or less.

4. (b) The step of placing the electrode assembly in the cup portion and folding the pouch film with respect to the bridge portion so that the pair of cup portions cover the electrode assembly, (c) further includes the step of sealing and sealing the open portion of the folded pouch film, Step (c) above is, (c-1) The step of sealing the outer edge of the pouch film, (c-2) A method for manufacturing a pouch cell according to claim 1 or 2, comprising the step of forming an additional sealing portion having a distance of 0.5 mm or more and 1.5 mm or less from the cup portion.

5. (a) The step of forming the pouch film containing a metal layer such that a pair of cup portions capable of housing an electrode assembly are formed on both sides of the bridge portion, In step (a) above, A method for manufacturing a pouch cell, wherein the metal layer is formed such that the thickness of the metal layer in the bridge portion is reduced by 20% or less.

6. The aforementioned metal layer is A method for producing a pouch cell according to claim 5, comprising aluminum (Al).

7. Electrode assembly and It includes a pouch having a metal layer and a shape in which both sides are folded relative to the bridge portion so as to cover the electrode assembly, The aforementioned pouch is It includes a cup portion having a space inside for housing the electrode assembly, A pouch cell that satisfies the formula T / D > 0.006, where T is the thickness of the metal layer in the bridge portion and D is the depth of the cup portion.

8. The aforementioned pouch is It includes a sealing portion that is positioned separately from the cup portion and is sealed so as to isolate the electrode assembly from the outside, The pouch cell according to claim 7, wherein the minimum distance between the cup portion and the sealing portion is 0.5 mm or more and 1.5 mm or less.

9. The aforementioned sealing portion is The cup portion and the outer sealing portion are arranged at a predetermined distance apart, The present invention further includes an additional sealing portion disposed between the outer sealing portion and the cup portion, The pouch cell according to claim 8, wherein the distance between the additional sealing portion and the cup portion is 0.5 mm or more and 1.5 mm or less.

10. The bridge portion is formed at one end of the cup portion, The aforementioned additional sealing portion is The pouch cell according to claim 9, wherein one end is positioned to be on the same line as one end of the cup portion.

11. The aforementioned additional sealing portion is The pouch cell according to claim 9, having a shape in which the width gradually decreases as it approaches the cup portion from the outer sealing portion.

12. The aforementioned pouch is The pouch cell according to any one of claims 8 to 11, wherein the thickness of the metal layer in the bridge portion is 0.8 times or more the thickness of the metal layer in the seal portion.

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