Pouch-type rechargeable battery and battery module containing the same

Abstract

To provide a pouch type secondary battery and a battery module including the pouch type secondary battery.SOLUTION: According to an embodiment of the present invention, a pouch type secondary battery can include an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated across a separator, and a pouch formed by mutually sealing a pair of cases connected into a single body by a folding part to have a housing part for housing the electrode assembly. A plurality of outer walls forming a peripheral edge of the housing part include a folding part side outer wall including the folding part and a ceiling part side outer wall connecting a ceiling part with the pair of cases mutually fused, and an average distance between edge parts of the plurality of negative electrodes and the folding part side outer wall can be 0.6 mm or below.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pouch-type secondary battery and a battery module including the same.

Background Art

[0002] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. Such secondary batteries are not only applicable to small products such as digital cameras, portable DVD players (P-DVDs), MP3 players (MP3Ps), mobile phones, PDAs, portable game devices, power tools, and electric bicycles, but also to large products that require high power such as electric vehicles and hybrid vehicles, as well as power storage devices for storing surplus generated power and newly renewable energy and backup power storage devices.

[0003] To manufacture such a secondary battery, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and these are laminated on both sides of a separator to form an electrode assembly of a predetermined shape. Further, the electrode assembly is housed in a battery case, electrolyte is injected, and then sealed.

[0004] Secondary batteries can be classified into pouch types and can types according to the material of the case that houses the electrode assembly. The pouch type houses the electrode assembly in a pouch made of a flexible polymer material. Also, the can type houses the electrode assembly in a case made of a material such as metal or plastic.

[0005] The pouch, which is the case for a pouch-type rechargeable battery, is manufactured by pressing a flexible pouch film to form a cup portion. Once the cup portion is formed, the electrode assembly is placed in the storage space of the cup portion, and the sides are sealed to manufacture the rechargeable battery.

[0006] Among these press processes, drawing molding involves inserting a pouch film into a molding device such as a press, applying pressure to the pouch film with a punch, and stretching the film. The pouch film is formed from multiple layers, the moisture barrier layer located inside, which is made of metal. However, conventionally, the metal used for this moisture barrier layer was an aluminum alloy with a large grain size, resulting in a thin moisture barrier layer and reduced moldability. Therefore, when forming the cup portion of the pouch film, there were limitations in increasing the depth of the cup portion while improving the thickness of the bridge and the width of the folding portion. There were also limitations in reducing the size of the butt ear, which reduced the energy density relative to the volume of the secondary battery. Furthermore, there were limitations in manufacturing an overall sharp shape, resulting in an aesthetically unappealing appearance of the secondary battery and reduced marketability. [Overview of the project] [Problems that the invention aims to solve]

[0007] One problem that this invention aims to solve is to minimize the distance between the electrodes of the electrode assembly and the pouch, thereby providing a pouch-type secondary battery that has a beautiful appearance and high energy density.

[0008] Another problem that the present invention aims to solve is to provide a battery module in which the distance between the electrodes of the electrode assembly and the pouch is minimized, thereby improving the cooling efficiency of the secondary battery. [Means for solving the problem]

[0009] A pouch-type secondary battery according to an embodiment of the present invention may include an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator in between, and a pouch having a storage section in which the electrode assembly is housed, formed by sealing a pair of cases integrally connected by a folding section. A plurality of outer walls forming the periphery of the storage section may include a folding section-side outer wall including the folding section and a sealing section-side outer wall connected to a sealing section where the pair of cases are fused together. The average distance between the ends of the plurality of negative electrodes and the folding section-side outer wall may be 0.6 mm or less.

[0010] At multiple points spaced apart from each other in the longitudinal direction of the outer wall of the folding portion, the average distance between the ends of the multiple negative electrodes and the outer wall of the folding portion can be 0.6 mm or less, and the overall average distance can be 0.5 mm or less.

[0011] The maximum distance between the ends of the multiple negative electrodes and the outer wall on the folding portion side can be 0.8 mm or less.

[0012] The ends of the plurality of negative electrodes protrude further toward the outer wall on the folding portion side than the ends of the plurality of positive electrodes, and the average distance between the ends of the negative electrodes and the outer wall on the folding portion side can be less than the average distance between the ends of the negative electrodes and the ends of the positive electrodes.

[0013] The distance between the end of the negative electrode and the outer wall on the folding portion side may be less than half the distance between the end of the negative electrode and the end of the positive electrode.

[0014] The folding portion may have a groove shape extending from one end to the other end of the outer wall on the side of the folding portion.

[0015] The storage section may include a first edge formed in a rounded shape that connects the upper or lower surface of the storage section to the outer wall on the folding section side, a second edge formed in a rounded shape that connects the upper or lower surface of the storage section to the outer wall on the sealing section side, a third edge formed in a rounded shape that connects the outer wall on the folding section side and the outer wall on the sealing section side, and a corner to which the first edge, second edge and third edge are connected.

[0016] A virtual line that is in contact with the innermost part of the folding section and is parallel to the stacking direction of the electrode assembly can pass through at least one of the top surface, bottom surface, and first edge of the storage section.

[0017] The radius of curvature of the third edge can be greater than the radius of curvature of the first edge and the radius of curvature of the second edge.

[0018] The radius of curvature of the aforementioned corner can increase from the periphery towards the center.

[0019] The pouch connects the corner of the sealing portion and the folding portion, and includes a protruding portion that extends beyond the corner of the sealing portion in the width direction of the storage portion, and the boundary between the protruding portion and the folding portion can be located outside the boundary between the first edge and the corner with respect to the length direction of the folding portion.

[0020] The pouch can be manufactured by forming a pouch film. The pouch film may include a sealant layer made of a first polymer and formed as the innermost layer, a surface protection layer made of a second polymer and formed as the outermost layer, and a moisture barrier layer made of a metal including an aluminum alloy of alloy number AA80XX and laminated between the surface protection layer and the sealant layer. The thickness of the moisture barrier layer may be 50 to 80 μm, and the thickness of the sealant layer may be 60 to 100 μm.

[0021] The alloy number of the aluminum alloy can be AA8021.

[0022] The aluminum alloy can contain 1.3 wt% to 1.7 wt% of iron, contain 0.2 wt% or less of silicon, and have a crystal grain size of 10 to 13 μm.

[0023] The thickness of the moisture barrier layer can be 55 to 65 μm, and the thickness of the sealant layer can be 75 to 85 μm.

[0024] The pouch film can be made of a third polymer and further include a stretching auxiliary layer laminated between the surface protection layer and the moisture barrier layer.

[0025] The thickness of the stretching auxiliary layer can be 20 to 50 μm.

[0026] The pouch-type secondary battery according to an embodiment of the present invention can include an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with a separator interposed therebetween, and a pouch having a storage portion in which the electrode assembly is accommodated, formed by sealing a pair of cases integrally connected by a folding portion. A plurality of outer walls forming the periphery of the storage portion can include an outer wall on the folding portion side including the folding portion, and an outer wall on the sealing portion side to which a sealing portion where the pair of cases are fused to each other is connected. The ends of the plurality of negative electrodes can protrude further toward the outer wall on the folding portion side than the ends of the plurality of positive electrodes, and the distance between the end of the negative electrode and the outer wall on the folding portion side can be less than half of the distance between the end of the negative electrode and the end of the positive electrode.

[0027] A battery module according to an embodiment of the present invention can include a housing, a plurality of secondary batteries vertically stacked in the housing, and a cooling unit provided on the inner bottom surface of the housing for cooling the plurality of secondary batteries. The secondary battery can include an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator interposed therebetween, and a pouch having a storage portion formed by sealing a pair of cases integrally connected by a folding portion and accommodating the electrode assembly. The plurality of outer walls forming the periphery of the storage portion include the folding portion, and can include an outer wall on the folding portion side adjacent to the cooling unit and an outer wall on the sealing portion side to which a sealing portion obtained by fusing the pair of cases to each other is connected. The average distance between the ends of the plurality of negative electrodes and the outer wall on the folding portion side can be 0.6 mm or less.

[0028] A battery module according to an embodiment of the present invention can include a housing, a plurality of secondary batteries vertically stacked in the housing, and a cooling unit provided on the inner bottom surface of the housing for cooling the plurality of secondary batteries. The secondary battery can include an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with a separator interposed therebetween, and a pouch having a storage portion formed by sealing a pair of cases integrally connected by a folding portion and accommodating the electrode assembly. The plurality of outer walls forming the periphery of the storage portion include the folding portion, and can include an outer wall on the folding portion side adjacent to the cooling unit and an outer wall on the sealing portion side to which a sealing portion obtained by fusing the pair of cases to each other is connected. The ends of the plurality of negative electrodes protrude further toward the outer wall on the folding portion side than the ends of the plurality of positive electrodes, and the distance between the end of the negative electrode and the outer wall on the folding portion side can be less than half of the distance between the end of the negative electrode and the end of the positive electrode.

Advantages of the Invention

[0029] According to a preferred embodiment of the present invention, the moldability of the pouch is improved, and the distance between the multiple electrodes and the pouch can be shortened compared to conventional methods. This allows the secondary battery to have a sharp appearance.

[0030] Furthermore, the amount of empty space within the pouch is reduced, which can improve the energy density of the secondary battery.

[0031] Furthermore, the cooling efficiency of the electrode assembly by the cooling section in the battery module can be improved. [Brief explanation of the drawing]

[0032] [Figure 1] This is an assembly diagram of a pouch-type rechargeable battery according to one embodiment of the present invention. [Figure 2] This is a schematic diagram showing how a pouch is folded according to one embodiment of the present invention. [Figure 3] This is a schematic diagram showing how a pouch according to one embodiment of the present invention is folded. [Figure 4] This is a plan view of a pouch-type rechargeable battery according to one embodiment of the present invention. [Figure 5] This is a schematic diagram showing an enlarged view of the area around the outer wall on the folding side inside a pouch-type secondary battery according to one embodiment of the present invention. [Figure 6] This is a schematic diagram showing how a pouch is folded according to another embodiment of the present invention. [Figure 7] This is a schematic diagram showing how a pouch according to another embodiment of the present invention is folded. [Figure 8] This is a cross-sectional view of a pouch film according to one embodiment of the present invention. [Figure 9] This graph shows the iron and silicon content of aluminum alloys with alloy numbers AA8079 and AA8021. [Figure 10] This graph shows the changes in tensile strength, elongation, and grain size of aluminum alloys with alloy number AA8079 and AA8021 depending on their iron content. [Figure 11] These are magnified SEM images of the crystal grains of aluminum alloy alloy number AA8079 and aluminum alloy alloy number AA8021. [Figure 12] This is a perspective view illustrating the external appearance of a portion of a pouch-type rechargeable battery according to one embodiment of the present invention. [Figure 13] This is a view of the pouch-type rechargeable battery shown in Figure 12 from a different direction. [Figure 14] This is a perspective view illustrating the external appearance of a portion of a conventional pouch-type rechargeable battery. [Figure 15] This is a view of the pouch-type rechargeable battery shown in Figure 14 from a different direction. [Figure 16] This is a CT image showing the distance between the outer wall of the folding section and the negative electrode according to one embodiment of the present invention. [Figure 17] This is a CT image showing the distance between the outer wall of the folding section and the negative electrode according to one embodiment of the present invention. [Figure 18] This is a CT image showing the distance between the outer wall of the folding section and the negative electrode. [Figure 19] This is a CT image showing the distance between the outer wall of the folding section and the negative electrode. [Figure 20] This is a schematic diagram of a battery module according to one embodiment of the present invention. [Modes for carrying out the invention]

[0033] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying 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 embodiments described below.

[0034] For the purpose of clearly describing the present invention, detailed descriptions of relevant prior art 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 the drawings, the same or similar reference numerals are used for components that are the same or similar throughout the specification.

[0035] Furthermore, the terms and words used in this specification and 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 appropriately define the concepts of terms in order to best describe their invention.

[0036] Figure 1 is an assembly diagram of a pouch-type secondary battery according to one embodiment of the present invention, and Figure 2 is a schematic diagram showing how the pouch is folded according to one embodiment of the present invention.

[0037] The pouch-type secondary battery 1 (hereinafter referred to as "secondary battery") according to the present invention may include an electrode assembly 10 and a pouch 20 that houses the electrode assembly 10.

[0038] The electrode assembly 10 can be formed by alternately stacking separators 11 and electrodes 12. More specifically, the electrodes 12 may include a positive electrode 13 (see Figure 5) and a negative electrode 14, and the positive electrode 13 and the negative electrode 14 can be alternately stacked with the separator 11 in between.

[0039] The electrode 12 can be formed by coating an electrode current collector in the form of a metal foil or metal mesh with an active material slurry. In the case of the positive electrode 13, the electrode current collector may be made of aluminum. In the case of the negative electrode 14, the electrode current collector may be made of copper.

[0040] The electrode assembly 10 may be provided with electrode tabs 15. The electrode tabs 15 are connected to the positive electrode 13 and negative electrode 14 of the electrode assembly 10, respectively, and protrude outward from the electrode assembly 10, forming paths through which electrons can move between the inside and outside of the electrode assembly 10.

[0041] Multiple electrode tabs 15 connected to the positive electrode 13 and multiple electrode tabs 15 connected to the negative electrode 14 can protrude from the electrode assembly 10 in different directions from each other. However, it is not limited to this, and it is also possible for the multiple electrode tabs 15 connected to the positive electrode 13 and multiple electrode tabs 15 connected to the negative electrode 14 to protrude from the electrode assembly 10 in the same direction and parallel to each other.

[0042] Multiple electrode tabs 15 can be connected by spot welding or the like to electrode leads 16 that supply electricity to the outside of the secondary battery 1. One end of the electrode lead 16 is connected to the multiple electrode tabs 15, and the other end can protrude to the outside of the pouch 20.

[0043] A portion of the electrode lead 16 can be surrounded by an insulating portion 17. For example, the insulating portion 17 may include insulating tape. The insulating portion 17 can be located between a pair of terraces 26 of the pouch 20, which can be heat-sealed to each other. In this state, a portion of the pair of terraces 26 can be heat-sealed to the insulating portion 17. Thus, the insulating portion 17 can prevent electricity generated from the electrode assembly 10 from flowing through the electrode lead 16 to the pouch 20 and maintain the sealing of the pouch 20.

[0044] On the other hand, the pouch 20 can be formed by sealing a pair of cases 21 connected by a folding section 29. The configuration of each case 21 described below will be explained based on the state in which the pouch 20 is unfolded. The "state in which the pouch 20 is unfolded" means the state in which the pouch 20 is unfolded by releasing any predetermined adhesive or sealing present in the pouch 20.

[0045] In this embodiment, each case 21 may include a cup portion 22 having an indented shape and a terrace 26 located on the periphery of the cup portion 22.

[0046] The cup portion 22 can indent from the terrace 26 by a predetermined depth to form an indented space S1.

[0047] The cup portions 22 of a pair of cases 21 can be connected to each other by a folding portion 29. That is, the folding portion 29 can be located between the pair of cup portions 22, and when the pouch 20 is unfolded, the folding portion 29 can be referred to as a bridge. The folding portion 29 can extend parallel to the length of the pouch 20.

[0048] After housing the electrode assembly 10 in the recessed space S1 of one of the cup portions 22, the folding portion 29 can be folded so that the pair of cup portions 22 face each other. This allows the other cup portion 22 to cover the electrode assembly 10 from above. In other words, the recessed spaces S1 of each cup portion 22 can communicate with each other, and the electrode assembly 10 can be housed in the recessed spaces S1.

[0049] The depths of the indentations of the pair of cup portions 22 can be the same. In this case, the pair of cup portions 22 can have a symmetrical shape. However, it is not limited to this, and it is also possible for the indentations of the pair of cup portions 22 to be formed to be different. In this case, the pair of cup portions 22 can have an asymmetrical shape.

[0050] More specifically, each cup portion 22 may include a bottom portion 23 and peripheral portions 24, 25.

[0051] The bottom portion 23 can be formed parallel to the terrace 26.

[0052] The peripheral portions 24 and 25, together with the bottom portion 23, can surround the indented space S1. More specifically, the peripheral portions 24 and 25 may include a first surface 24 connected to the folding portion 29 and a plurality of second surfaces 25 connected to the terrace 26. Three of the second surfaces 25 can be connected to each other to form a "U" shape.

[0053] The terrace 26 can be located on the periphery of the cup portion 22. More specifically, the terrace 26 can be connected to the upper ends of multiple second surfaces 25 of the cup portion 22. Thus, the terrace 26 can have a roughly "U" shape.

[0054] More specifically, the terrace 26 may include an extension 28 located on the opposite side of the folding portion 29 from the cup portion 22, and a pair of sides 27 connecting the folding portion 29 and the extension 28.

[0055] The extension portion 28 can extend parallel to the length of the pouch 20. The pair of sides 27 can extend parallel to the width of the pouch 20 and be positioned opposite each other to the cup portion 22.

[0056] Figure 3 is a schematic diagram showing a folded pouch according to one embodiment of the present invention, and Figure 4 is a plan view of a pouch-type secondary battery according to one embodiment of the present invention.

[0057] By placing the electrode assembly 10 between the pair of cup portions 22 of the pouch 20, folding the folding portion 29, and fusing the pair of terraces 26 together, a secondary battery 1 can be formed in which the pair of cases 21 are sealed to each other.

[0058] The secondary battery 1 may include a housing section for housing the electrode assembly 10 and a sealing section formed by fusing the pair of cases 21 together.

[0059] The storage section is formed by connecting the cup portions 22 of a pair of cases 21, and for convenience, it will be referred to as "22" below, which is the same reference numeral as the cup portion 22 in the drawings. The sealing section is formed by fusing together the terraces 26 of a pair of cases 21, and for convenience, it will be referred to as "26" below, which is the same reference numeral as the terrace.

[0060] The storage section 22 may include a bottom surface and a top surface that cover the electrode assembly 10 on both sides in the stacking direction of the electrode assembly 10, and a plurality of outer walls that form the periphery of the storage section 22 and surround the periphery of the electrode assembly 10. The plurality of outer walls may include a folding section side outer wall including the folding section 29 and a sealing section side outer wall connected to the sealing section 26.

[0061] More specifically, the bottom surface of the storage section 22 is made up of the bottom 23 of one of the cup sections 22, and the top surface of the storage section 22 is made up of the bottom 23 of the other cup section 22. Hereafter, the bottom and top surfaces of the storage section 22 will be denoted by "23", which is the same drawing reference numeral as the bottom 23 of the cup section 22.

[0062] Furthermore, the outer wall of the folding section of the storage section 22 can consist of the first surface 24 of the pair of cup sections 22 and the folding section 29. Hereafter, the outer wall of the folding section of the storage section 22 will be denoted as "24", which is the same drawing reference numeral as the first surface 24 of the cup section 22.

[0063] If the cup portions 22 of a pair of cases 21 are formed to the same or similar depths, the folding portion 29 can be located in the center of the outer wall 24 on the folding portion side with respect to the stacking direction of the electrode assembly 10.

[0064] Furthermore, the outer wall of the storage section 22 on the sealing side can consist of the second surface 25 of a pair of cup sections 22. Hereafter, the outer wall of the storage section 22 on the sealing side will be denoted as "25", which is the same drawing reference numeral as the second surface 25 of the cup section 22.

[0065] Therefore, the outer wall 24 on the folding section side can form one part of the periphery of the storage section 22, and the outer wall 25 on the sealing section side can form another part of the periphery of the storage section 22. The outer wall 24 on the folding section side can include the folding section 29, and the outer wall 25 on the sealing section side can be connected to the sealing section 26.

[0066] The sealing portion 26 may include a first sealing portion where the sides 27 of a pair of cases 21 are fused together, and a second sealing portion where the extension portions 28 of a pair of cases 21 are fused together. Hereinafter, the first sealing portion will be denoted as "27", the same reference numeral as the side 27, and the second sealing portion will be denoted as "28", the same reference numeral as the extension portion 28.

[0067] The first sealing portion 27 extends in the width direction of the secondary battery 1 and may consist of a pair of portions located on opposite sides of the storage portion 22. The electrode leads 16 can protrude to the outside of the pouch 20 through the first sealing portion 27.

[0068] The second sealing portion 28 extends in the longitudinal direction of the secondary battery 1 and can project outwards from the side of the folding portion side outer wall 24. The second sealing portion 28 can be folded at least once toward the storage portion 22, thereby reducing the width of the secondary battery 1. For example, the second sealing portion 28 can be folded twice in a double-side folding (DSF) manner.

[0069] Figure 5 is a schematic diagram showing an enlarged view of the area around the outer wall on the folding section side inside a pouch-type secondary battery according to one embodiment of the present invention.

[0070] In the electrode assembly 10, the negative electrode 14 can be formed larger than the positive electrode 13, and the separator 11 can be formed larger than the negative electrode 14.

[0071] Therefore, the ends 14a of the multiple negative electrodes 14 can protrude further toward the outer wall 24 on the folding section side than the ends 13a of the multiple positive electrodes 13, and the ends 11a of the multiple separators 11 can protrude further toward the outer wall 24 on the folding section side than the ends 14a of the multiple negative electrodes 14. It goes without saying that the ends 11a of the separators 11 can also come into contact with the outer wall 24 on the folding section side.

[0072] On the other hand, the ends 14a of the multiple negative electrodes 14 and the ends 13a of the multiple positive electrodes 13 can be separated from the outer wall 24 on the folding section side. However, conventionally, the distance between the ends 14a of the multiple negative electrodes 14 and the outer wall 24 on the folding section side was relatively large, which limited the ability to manufacture secondary batteries with a sleek appearance.

[0073] Therefore, it is preferable to separate the ends 14a of the multiple negative electrodes 14 from the outer wall 24 on the folding portion side, and to minimize the distance between them as much as possible.

[0074] To achieve this, it is desirable to improve the moldability of the pouch film, which is the base material of pouch 20. The pouch film can be formed into pouch 20 by a forming process using a die and a punch. Since the forming process is a well-known technique, a detailed explanation will be omitted.

[0075] By improving the moldability of the pouch film, the tolerances in the forming process are reduced, enabling precise manufacturing. This allows the gap between the ends 14a of the multiple negative electrodes 14 and the outer wall 24 on the folding side to be minimized. The configuration of the pouch film for improving moldability will be described in detail below.

[0076] Figure 6 is a schematic diagram showing how a pouch according to another embodiment of the present invention is folded, and Figure 7 is a schematic diagram showing the folded state of the pouch according to another embodiment of the present invention.

[0077] The following explanation will refer to the content mentioned above where necessary, and will focus on the differences.

[0078] The pouch 20 according to this embodiment can be formed by sealing together a first case 21a and a second case 21b, which are formed by a folding portion 29. The first case 21a may have a cup portion 22, while the second case 21b may not have a cup portion 22.

[0079] The second case 21b can be substantially flat in shape. Part of the second case 21b can cover the cup portion 22 of the first case 21a, and the other part of the second case 21b can be fused to the terrace 26 of the first case 21a.

[0080] More specifically, after the electrode assembly 10 is placed in the recessed space S1 of the cup portion 22 of the first case 21a, the folding portion 29 can be folded so that the second case 21b covers the recessed space S1 from above.

[0081] Therefore, the bottom surface of the storage section 22 of the secondary battery 1 in this embodiment is formed by the bottom 23 of the cup section 22 of the first case 21a, and the top surface of the storage section 22 can be formed by a part of the second case 21b.

[0082] Furthermore, the sealing portion 26 of the secondary battery 1 can be formed by fusing the terrace 26 of the first case 21a with another part of the second case 21b.

[0083] Furthermore, the outer wall on the folding portion side of the storage portion 22 can consist of the first surface 24 of the cup portion 22 of the first case 21a and the folding portion 29. Therefore, the folding portion 29 can be located above the outer wall 24 on the folding portion side with respect to the stacking direction of the electrode assembly 10.

[0084] Furthermore, the outer wall on the sealing side of the storage section 22 can be made of the second surface 25 of the cup section 22 of the first case 21a.

[0085] Figure 8 is a cross-sectional view of a pouch film according to one embodiment of the present invention.

[0086] The pouch film according to this embodiment can be the base material for pouch 20. Pouch 20 can be manufactured by drawing the pouch film. For convenience, the pouch film will be referred to as "20" below, which is the same drawing reference numeral as pouch 20.

[0087] The pouch film 20 includes a sealant layer 20a, a moisture barrier layer 20b, a surface protection layer 20c, and a drawing assistance layer 20d.

[0088] The sealant layer 20a can form the innermost layer of the pouch 20. More specifically, in the secondary battery 1, the sealant layer 20a can be the inner surface of the housing 22 or a layer fused to each other by a pair of sealing portions 26.

[0089] The sealant layer 20a needs to be insulating because it comes into contact with the electrode assembly 10, and it also needs to be corrosion-resistant because it comes into contact with the electrolyte injected into the housing 22 during the manufacturing process of the secondary battery 1. Furthermore, it needs to have high sealing properties because the inside of the housing 22 must be completely sealed to prevent mass transfer between the inside and outside. In other words, the sealing portion 26, where the sealant layers 20a are bonded together, needs to have excellent thermal bonding strength.

[0090] The sealant layer 20a may have a first polymer material, the first polymer may 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) has excellent 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 sealant layer 20a. Furthermore, it may also consist of casted polypropylene, acid-modified polypropylene, or polypropylene-butylene-ethylene ternary copolymer. Here, acid-modified polypropylene may be MAH PP (Malayic anhydride polypropylene). Furthermore, the sealant layer 20a may have a single film structure consisting of one of the materials, or a composite film structure formed by two or more materials each forming a layer.

[0091] Furthermore, the thickness of the sealant layer 20a can be 60 to 100 μm, and in particular, it can be 75 to 85 μm. If the thickness of the sealant layer 20a is less than 60 μm, there is a possibility of problems such as internal damage during sealing, which reduces the sealing durability. Also, if the thickness of the sealant layer 20a is more than 100 μm, the overall thickness of the pouch becomes excessively thick, which may actually decrease the energy density relative to the volume of the secondary battery 1.

[0092] The moisture barrier layer 20b is laminated between the surface protection layer 20c and the sealant layer 20a to ensure the mechanical strength of the pouch, block the entry and exit of gases or moisture from the outside of the secondary battery 1, and prevent electrolyte leakage. The moisture barrier layer 20b can be made of metal, more specifically aluminum. Aluminum can ensure mechanical strength above a certain level, is lightweight, and can complement the electrochemical properties of the electrode assembly 10 and the electrolyte, as well as ensure heat dissipation.

[0093] Conventionally, aluminum alloys of the AA30XX series with alloy number AA30XX have been commonly used, but they have the problem of low mechanical strength because their iron content is 0.7 wt% or less. To solve this problem, the moisture barrier layer 20b according to this embodiment can be manufactured from a metal containing an aluminum alloy of the AA80XX series with alloy number AA80XX.

[0094] Such 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). A detailed description of the aluminum alloy used to produce the moisture barrier layer 20b according to one embodiment of the present invention will be given later.

[0095] Conventionally, the moisture barrier layer had a thickness of approximately 30-50 μm, particularly 40 μm, which reduced moldability. Therefore, even when the pouch film was pressed and molded, the depth of the cup portion 22 increased, limiting the ability to mold the peripheral portions 24 and 25 of the cup portion 22 nearly vertically, and limiting the reduction of the radius of curvature of the edge connecting the bottom portion 23 and the peripheral portions 24 and 25 of the cup portion 22 in a rounded shape.

[0096] To solve this, increasing the thickness of the moisture barrier layer 20b to more than approximately 80 μm would not only increase manufacturing costs but also lead to a problem where the overall thickness of the pouch becomes excessively thick, reducing the energy density relative to the volume of the secondary battery 1. If the thickness of the sealant layer 20a is reduced to less than 60 μm in order to decrease the overall thickness of the pouch, then, as mentioned above, there is a problem of reduced sealing durability.

[0097] According to this embodiment, the moisture barrier layer 20b can have a thickness of 50 μm to 80 μm, and in particular, 55 μm to 65 μm. Therefore, the moldability of the moisture barrier layer 20b is improved, and when the pouch film 20 is pressed, the depth of the cup portion 22 can be formed to be greater, the peripheral portions 24 and 25 of the cup portion 22 become closer to vertical, and the radius of curvature of the edge connecting the bottom portion 23 of the cup portion 22 and the peripheral portions 24 and 25 can also be reduced. As a result, the volume of the recessed space S1 increases, allowing a larger electrode assembly 10 to be accommodated, and the energy efficiency of the secondary battery 1 relative to its volume can also be increased. Furthermore, manufacturing costs do not increase significantly, and the overall thickness of the pouch does not increase significantly even without reducing the thickness of the sealant layer 20a, and sealing durability does not decrease.

[0098] The surface protection layer 20c is formed on the outermost layer of the pouch 20 to protect the secondary battery 1 from friction and collision with the outside, and to electrically insulate the electrode assembly 10 from the outside. More specifically, in the secondary battery 1, the surface protection layer 20c can be a layer that forms the appearance of the pouch 20.

[0099] The surface protective layer 20c may have a second polymer material, and the second polymer may 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 a polymer such as polyethylene terephthalate (PET) which has abrasion resistance and heat resistance. The surface protective layer 20c may also have a single film structure consisting of one of these substances, or a composite film structure formed by two or more substances each forming a layer.

[0100] According to this embodiment, the thickness of such a surface protective layer 20c can be 5 μm to 25 μm, and in particular, it can be 7 μm to 12 μm. If the thickness of the surface protective layer 20c is less than 5 μm, there may be a problem of reduced external insulation. Conversely, if the thickness of the surface protective layer 20c is greater than 25 μm, the overall thickness of the pouch increases, which may actually decrease the energy density relative to the volume of the secondary battery 1.

[0101] On the other hand, while PET is inexpensive, highly durable, and has excellent electrical insulation properties, it also has poor adhesion to aluminum, which is often used as the moisture barrier layer 20b, and their behavior when stretched under stress may differ. Therefore, if the surface protection layer 20c and the moisture barrier layer 20b are directly bonded, the surface protection layer 20c and the moisture barrier layer 20b may separate during the deep drawing process. As a result, the moisture barrier layer 20b may not be stretched uniformly, which can lead to problems with reduced moldability.

[0102] To address these issues, the pouch film 20 may further include a stretching auxiliary layer 20d laminated between the surface protective layer 20c and the moisture barrier layer 20b.

[0103] The stretching auxiliary layer 20d is laminated between the surface protective layer 20c and the moisture barrier layer 20b, preventing the surface protective layer 20c and the moisture barrier layer 20b from peeling off when they are stretched.

[0104] The stretching auxiliary layer 20d is made of a third polymer, which 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 can be mainly used as the third polymer because it adheres easily to polyethylene terephthalate (PET) of the surface protective layer 20c and behaves similarly to the aluminum alloy of the moisture barrier layer 20b when stretched. Furthermore, the stretching auxiliary layer 20d 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 layers.

[0105] Conventionally, the moisture barrier layer has a thickness of approximately 40 μm, resulting in a considerably thinner stretching auxiliary layer of approximately 15 μm. That is, the ratio of the thickness of the stretching auxiliary layer to the moisture barrier layer is 1:2.67, with the moisture barrier layer having a considerably higher thickness. However, as described above, according to this embodiment, the moisture barrier layer 20b has a thickness of approximately 50 to 80 μm, particularly 55 to 65 μm, thus improving the moldability of the moisture barrier layer 20b. In this case, in order to also improve the moldability of the stretching auxiliary layer 20d, the stretching auxiliary layer 20d can have a thickness of 20 μm to 50 μm, and is particularly preferably 25 μm to 38 μm. If it is thinner than 20 μm, the stretching auxiliary layer 20d may not be able to cope with the improved moldability of the moisture barrier layer 20b and may break during the stretching process. Conversely, if the thickness is greater than 50 μm, the overall thickness of the pouch increases, which can increase the volume of the secondary battery 1 and decrease the energy density. In particular, according to this embodiment, the ratio of the thickness of the stretching auxiliary layer 20d to the thickness of the moisture barrier layer 20b can be less than 1:2.5. That is, the ratio of the thickness of the stretching auxiliary layer 20d can be increased compared to the conventional method. However, if the thickness of the stretching auxiliary layer 20d becomes excessively thick, the overall thickness of the pouch increases, so in order to avoid excessive thickness, the ratio of the thicknesses can be greater than 1:1.5. That is, the ratio of the thicknesses can be between 1:1.5 and 1:2.5.

[0106] Figure 9 is a graph showing the iron and silicon content of aluminum alloy alloy number AA8079 and aluminum alloy alloy number AA8021.

[0107] When aluminum alloys contain a large amount of iron, their mechanical strength improves, while when they contain less iron, their flexibility improves. Among aluminum alloys, alloy number AA8079 contains 0.6 wt% to 1.2 wt% iron and less than 0.3 wt% silicon. In other words, when manufacturing the moisture barrier layer 20b with such an aluminum alloy of alloy number AA8079, the relatively low iron content can improve flexibility, but it may also reduce strength and limit formability.

[0108] On the other hand, among aluminum alloys, alloy number AA8021 can contain 1.2 wt% to 1.7 wt% of iron, particularly 1.3 wt% to 1.7 wt%, and 0.2 wt% or less of silicon. When manufacturing the moisture barrier layer 20b with such an aluminum alloy of alloy number AA8021, the tensile strength and elongation rate can be improved due to the relatively high iron content.

[0109] On the other hand, when a tensile force is applied to a material, the relationship between tensile strength and elongation can be shown graphically. In this case, if the vertical axis of the graph is tensile strength and the horizontal axis is elongation, the area under the graph represents the toughness of the material. Toughness indicates the degree to which a material is resistant to fracture; the higher the toughness, the more the material can be stretched before it breaks.

[0110] Therefore, when manufacturing the moisture barrier layer 20b with aluminum alloy alloy number AA8021, the tensile strength and elongation are improved, which increases toughness and improves formability.

[0111] Figure 10 is a graph showing the changes in tensile strength, elongation, and grain size of aluminum alloys with alloy number AA8079 and AA8021 due to iron content, and Figure 11 is a magnified SEM image of the crystal grains of aluminum alloys with alloy number AA8079 and AA8021.

[0112] As illustrated in Figure 10, the tensile strength, elongation, and grain size of an aluminum alloy change depending on its iron content. Specifically, since tensile strength and elongation are proportional to the iron content, they increase as the iron content increases. On the other hand, grain size is inversely proportional to the iron content, so grain size decreases as the iron content increases.

[0113] As mentioned above, among the aluminum alloys, alloy number AA8079 contains 0.6 wt% to 1.2 wt% iron, and as shown in Figure 11, its grain size is relatively large, ranging from 13 μm to 21 μm. Therefore, when stretched, internal stress is not sufficiently distributed, resulting in a large number of pinholes, which leads to a problem of reduced formability of the pouch film 20.

[0114] On the other hand, among aluminum alloys, alloy number AA8021 contains 1.2 wt% to 1.7 wt% iron, and as shown in Figure 11, its grain size is relatively small, ranging from 10 μm to 13 μm. Therefore, internal stress can be more dispersed when stretched, reducing the number of pinholes and improving the formability of the pouch film 20.

[0115] Therefore, the aluminum alloy forming the moisture barrier layer 20b according to this embodiment can contain 1.2 wt% to 1.7 wt% of iron, and in particular, 1.3 wt% to 1.7 wt%. Furthermore, the aluminum alloy can contain 0.2 wt% or less of silicon. In addition, the grain size can be 10 μm to 13 μm. That is, in this embodiment, the aluminum alloy used to produce the moisture barrier layer 20b can be alloy number AA8021.

[0116] Such a pouch film 20 offers improved moldability, allowing for a deeper cup portion 22 of the pouch 20, making the peripheral edges 24 and 25 of the cup portion 22 closer to vertical, and reducing the radius of curvature of the edges connecting the bottom portion 23 of the cup portion 22 to the peripheral edges 24 and 25, thus accommodating a larger and thicker electrode assembly 10. Therefore, a secondary battery 1 including such a pouch 20 can achieve increased energy efficiency relative to its volume.

[0117] Figure 12 is a perspective view showing a partial external view of a pouch-type secondary battery according to one embodiment of the present invention, and Figure 13 is a view of the pouch-type secondary battery shown in Figure 12 from another direction.

[0118] In the secondary battery 1, the storage section 22 may include a first edge 41 connecting the upper or lower surface 23 of the storage section 22 to the outer wall 24 on the folding section side, a second edge 42 connecting the upper or lower surface 23 of the storage section 22 to the outer wall 25 on the sealing section side, a third edge 43 connecting the outer wall 24 on the folding section side and the outer wall 25 on the sealing section side, and a corner 44 connecting the first edge 41, the second edge 42, and the third edge 43.

[0119] The first edge 41, the second edge 42, and the third edge 43 can be formed in a rounded shape. More specifically, each edge 41, 42, and 43 can be a curved surface shape having a predetermined radius of curvature, the radius of curvature can be constant or variable along the rounded direction.

[0120] The first edge 41 can connect the upper or lower surface 23 of the storage section 22 to the outer wall 24 on the folding section side in a rounded manner. The first edge 41 can extend in the longitudinal direction of the storage section 22 and can have a relatively constant radius of curvature along the extension direction.

[0121] The second edge 42 can connect the upper or lower surface 23 of the storage section 22 to the outer wall 25 on the sealing section side in a rounded manner. The second edge 42 adjacent to the first edge 41 can extend in the width direction of the storage section 22 and can have a relatively constant radius of curvature along the extension direction.

[0122] The third edge 43 can connect the folding section side outer wall 24 and the sealing section side outer wall 25 in a rounded manner. The third edge 43 can extend in the stacking direction of the electrode assembly 10, that is, in the height direction of the storage section 22, and can have a relatively constant radius of curvature along the extension direction.

[0123] The radius of curvature of the third edge 43 can be greater than the radius of curvature of the first edge 41 and the radius of curvature of the second edge 42.

[0124] The corner 44 can be formed by connecting the adjacent first edge 41, second edge 42, and third edge 43. To prevent excessive stress concentration at the corner 44 during the forming process of the pouch 20, the corner 44 can have a rounded surface shape in the round direction of each of the first edge 41, second edge 42, and third edge 43.

[0125] The radius of curvature of corner 44 can increase from the periphery towards the center. Therefore, the boundary between corner 44 and each edge 41, 42, 43 can be defined as the point where the radius of curvature between each edge 41, 42, 43 and corner 44 begins to increase sharply. The boundary can also be defined not only as a specific point, but as a predetermined range in the direction of extension of each edge 41, 42, 43.

[0126] More specifically, the radius of curvature of the first edge 41 with respect to the rounding direction can increase as you move from the boundary B1 between the first edge 41 and the corner 44 towards the center of the corner 44.

[0127] Furthermore, the radius of curvature of the second edge 42 with respect to the rounding direction can be increased as you move from the boundary between the second edge 42 and the corner 44 towards the center of the corner 44.

[0128] Furthermore, the radius of curvature of the third edge 43 with respect to the rounding direction can be increased as you move from the boundary between the third edge 43 and the corner 44 towards the center of the corner 44.

[0129] On the other hand, the pouch 20 may further include a protruding portion 30 that connects the corner of the sealing portion 26 to the outer wall 24 on the folding portion side and protrudes from the corner of the sealing portion 26 in the width direction of the storage portion 22.

[0130] More specifically, the protruding portion 30 connects the corner 27a of the first sealing portion 27 to the folding portion 29 and can protrude outward in a convex shape relative to the width direction of the storage portion 22. At the same time, the protruding portion 30 can have a shape that curves upward or downward.

[0131] During the forming process of the pouch 20, not only the cup portion 22 is stretched, but the portion adjacent to the cup portion 22 on the terrace 26 is also finely stretched overall. Therefore, when the folding portion 29 is folded during the manufacturing process of the secondary battery 1, the finely stretched portion accumulates, and the protruding portion 30 can be formed.

[0132] The protruding portion 30 can be connected to the folding portion 29 at the outer wall 24 on the folding portion side. The folding portion 29 may have a groove shape that extends from one end to the other end of the outer wall 24 on the folding portion side.

[0133] The boundary B2 between the protruding portion 30 and the folding portion 29 can be located outside the boundary B1 between the first edge 41 and the corner 44 with respect to the length direction of the folding portion 29. In other words, the boundary B2 between the protruding portion 30 and the folding portion 29 can be located at a point in the height direction of the storage portion 22 that coincides with the corner 44, rather than the first edge 41.

[0134] This feature is achievable by improving the moldability of the pouch film 20 compared to conventional designs. By minimizing the length or size of the protrusions 30, the secondary battery 1 can be formed with a sharper appearance, and its energy density can be improved. Furthermore, the cooling efficiency of the cooling section 3 can be improved in the battery module 100 (see Figure 20), which will be described later.

[0135] Figure 14 is a perspective view illustrating a portion of the external appearance of a conventional pouch-type rechargeable battery, and Figure 15 is a view of the pouch-type rechargeable battery shown in Figure 14 from a different direction.

[0136] As a comparative example, a conventional secondary battery will be described with reference to Figures 13 and 14. For ease of understanding, the same reference numerals used in the same components of the secondary battery 1 of the present invention will be used for the description.

[0137] Conventional rechargeable batteries have poor moldability in the pouch 20, resulting in relatively large radii of curvature for the first edge 41, second edge 42, and third edge 43. Consequently, there are limitations to forming a sharp appearance, and problems such as wrinkles and creases occur.

[0138] Furthermore, wrinkles may occur at the ends of the outer wall 24 on the folding section side and the outer wall 25 on the sealing section side, which may cause at least one of the first edge 41, the second edge 42, and the third edge 43 to have a radius of curvature that is excessively variable along the extension direction.

[0139] For example, wrinkles may form at the end of the outer wall 24 on the folding section side, which can cause the radius of curvature of the first edge 41 to suddenly increase or decrease in the portion adjacent to the corner 44. Consequently, there was a problem of irregular deformation of the corner 44.

[0140] Furthermore, the groove shape formed by the folding portion 29 may not extend to the end of the outer wall 24 on the folding portion side, but may disappear midway, or the protruding portion 30 may not be connected to the folding portion 29 at the outer wall 24 on the folding portion side.

[0141] Furthermore, even when the protruding portion 30 is connected to the folding portion 29, the boundary B2 between the protruding portion 30 and the folding portion 29 can be located outside the boundary B1 between the first edge 41 and the corner 44 with respect to the length direction of the folding portion 29. In other words, the boundary B2 between the protruding portion 30 and the folding portion 29 can be located at a point that coincides with the first edge 41 in the height direction of the storage portion 22. This is the opposite configuration to that of the present invention, and means that the protruding portion 30 of a conventional secondary battery is formed to be longer and larger in size.

[0142] Figures 16 and 17 are CT images showing the distance between the outer wall of the folding section and the negative electrode according to one embodiment of the present invention.

[0143] More specifically, Figure 16 is a CT (Computerized Tomography) image measured at the first point P1 in Figure 4, and Figure 17 is a CT image measured at the second point P2 in Figure 4. However, the method for measuring the distance between the folding section outer wall 24 and the negative electrode 14 is not limited to these methods; it is also possible to measure it using methods such as MRI (Magnetic Resonance Imaging) or X-ray.

[0144] The present invention improves the moldability of the pouch 20 so that the ends 14a (see Figure 5) of the multiple negative electrodes 14 and the outer wall 24 on the folding part side remain separated, and the distance between them is minimized during manufacturing. In this case, the distance may refer to the horizontal distance between the ends 14a (see Figure 5) of the multiple negative electrodes 14 and the outer wall 24 on the folding part side when the secondary battery 1 is placed on a horizontal surface such as a floor.

[0145] The distance between the end 14a of the negative electrode 14 and the outer wall 24 on the folding portion side can be less than the distance between the end 14a of the negative electrode 14 and the end 13a of the positive electrode 13.

[0146] Preferably, the distance between the end 14a of the negative electrode 14 and the outer wall 24 on the folding portion side can be less than half the distance between the end 14a of the negative electrode 14 and the end 13a of the positive electrode 13.

[0147] In other words, the distance between the end 14a of the negative electrode 14 and the outer wall 24 on the folding side can be shorter than half the distance that the negative electrode 14 protrudes from the positive electrode 13 toward the outer wall 24 on the folding side. This can be easily confirmed with the naked eye in Figures 16 and 17.

[0148] This minimizes void space within the pouch 20, increases the cooling efficiency of the cooling unit 3 (see Figure 20), and allows for a higher energy density of the secondary battery 1.

[0149] More specifically, the average distance between the ends 14a of the multiple negative electrodes 14 and the outer wall 24 on the folding section side can be reduced to 0.6 mm or less. The average distance may be measured at any point along the extension direction of the outer wall 24 on the folding section side. The average distance can be varied along the extension direction of the outer wall 24 on the folding section side.

[0150] Furthermore, the maximum distance between the ends 14a of the multiple negative electrodes 14 and the outer wall 24 on the folding section side can be 0.8 mm or less. If the maximum distance exceeds 0.8 mm, and the average distance is 0.6 mm or less, the deviation in the distance between the ends 14a of the multiple negative electrodes 14 and the outer wall 24 on the folding section side becomes excessively large, resulting in a problem of uneven quality in the secondary battery 1.

[0151] Furthermore, each of the multiple average distances measured at multiple points spaced apart in the longitudinal direction of the outer wall 24 on the folding section side is 0.6 mm or less, and the overall average distance, which is the average of the multiple average distances, can be 0.5 mm or less.

[0152] For example, at a first point P1 (see Figure 4) adjacent to the folding section side outer wall 24 by one of its ends, the average distance between the ends 14a of the multiple negative electrodes 14 and the folding section side outer wall 24 is referred to as the first distance. Similarly, at a second point P2 (see Figure 4) adjacent to the folding section side outer wall 24 by the other end, the average distance between the ends 14a of the multiple negative electrodes 14 and the folding section side outer wall 24 is referred to as the second distance. In this case, the first distance and the second distance can each be 0.6 mm or less, and the average of the first distance and the second distance, i.e., the overall average distance, can be 0.5 mm or less.

[0153] This allows the distance between the ends 14a of the multiple negative electrodes 14 and the outer wall 24 of the folding section to be kept relatively close overall along the extension direction of the outer wall 24 of the folding section.

[0154] If the overall average distance exceeds 0.5 mm, the void space within the pouch 20 increases, which reduces the cooling efficiency of the cooling unit 3 (see Figure 20), and also lowers the energy density of the secondary battery 1.

[0155] Furthermore, if the average distance exceeds 0.6 mm in any part of the outer wall 24 on the folding section side, that part will protrude compared to the surrounding area, limiting the aesthetic appeal of the secondary battery 1. This may prevent proper cooling of that part by the cooling section 3 (see Figure 20), which will be described later, potentially causing a localized temperature rise.

[0156] As an experimental example, referring to Figures 16 and 17, at the first point P1, the distances between the five negative electrodes 14 spaced apart from each other in the stacking direction of the electrode assembly 10 and the outer wall 24 on the folding section side were measured to be 0.60 mm, 0.74 mm, 0.53 mm, 0.30 mm, and 0.39 mm, respectively, confirming that the maximum distance was 0.74 mm and the average distance was 0.51 mm.

[0157] Furthermore, at the second location P2, the distances between the five negative electrodes 14, which are spaced apart from each other in the stacking direction of the electrode assembly 10, and the outer wall 24 on the folding section side were measured to be 0.22 mm, 0.54 mm, 0.41 mm, 0.57 mm, and 0.39 mm, respectively, confirming that the maximum distance was 0.57 mm and the average distance was 0.43 mm.

[0158] Therefore, it can be confirmed that the overall average distance at the first point P1 and the second point P2 is 0.47 mm.

[0159] In other words, the present invention makes it possible to confirm that the maximum distance at each point P1 and P2 is 0.8 mm or less, the average distance at each point P1 and P2 is 0.6 mm or less, and the overall average distance is 0.5 mm or less.

[0160] On the other hand, a virtual line VP that is in contact with the innermost part of the folding section 29 and is parallel to the stacking direction of the electrode assembly 10 can pass through at least one of the upper surface 23, the bottom surface 23, or the first edge 41 of the storage section 22.

[0161] Referring to Figure 16, it can be confirmed that the virtual line VP passes through one of the first edges 41 at the first point P1, and referring to Figure 17, it can be confirmed that the virtual line VP passes through the top and bottom surfaces 23 of the storage section 22 at the second point P2.

[0162] This configuration is made possible by improving the moldability of the pouch 20 of the present invention, which minimizes void space within the pouch 20, increases the cooling efficiency of the cooling section 3 (see Figure 20) described later, and increases the energy density of the secondary battery 1.

[0163] Figures 18 and 19 are CT images showing the distance between a conventional pouch and the negative electrode.

[0164] More specifically, Figure 18 is a CT image of a conventional secondary battery, showing the portion corresponding to the first point P1, and Figure 19 is a CT image of a conventional secondary battery, showing the portion corresponding to the second point P2.

[0165] Referring to Figures 18 and 19 as comparative examples, it can be confirmed that the distance between the end 14a of the negative electrode 14 and the outer wall 24 on the folding portion side is less than half the distance between the end 14a of the negative electrode 14 and the end 13a of the positive electrode 13. Furthermore, it can be confirmed that the distance between a portion of the end 14a of the negative electrode 14 and the outer wall 24 on the folding portion side is greater than the distance between the end 14a of the negative electrode 14 and the end 13a of the positive electrode 13.

[0166] Therefore, conventional rechargeable batteries have the problem of low cooling efficiency and energy density because a large void space is formed within the pouch 20.

[0167] Furthermore, at the portion corresponding to the first point P1, the distances between the five negative electrodes 14, which are spaced apart from each other in the stacking direction of the electrode assembly 10, and the outer wall 24 on the folding section side were measured to be 0.89 mm, 1.19 mm, 0.84 mm, 0.94 mm, and 1.23 mm, respectively, confirming that the maximum distance was 1.23 mm and the average distance was 1.01 mm.

[0168] Furthermore, in the portion corresponding to the second point P2, the distances between the five negative electrodes 14, which are spaced apart from each other in the stacking direction of the electrode assembly 10, and the outer wall 24 on the folding section side were measured to be 0.90 mm, 0.89 mm, 0.89 mm, 1.22 mm, and 0.75 mm, respectively, confirming that the maximum distance was 1.22 mm and the average distance was 0.93 mm.

[0169] Therefore, it can be confirmed that the overall average distance of the portions corresponding to the first point P1 and the second point P2 is 0.97 mm.

[0170] In other words, in the comparative example, unlike the present invention, it can be confirmed that the maximum distance at each point is greater than 0.8 mm, the average distance at each point is greater than 0.6 mm, and the overall average distance is greater than 0.5 mm.

[0171] Furthermore, referring to Figure 18, it can be confirmed that the groove shape of the folding section 29 disappears due to wrinkles in the outer wall 24 on the folding section side at the portion corresponding to the first point P1. Therefore, it is impossible to define the imaginary line.

[0172] Referring to Figure 19, it can be seen that the virtual line VP can be defined in the portion corresponding to the second point P2, but the virtual line VP does not pass through the upper surface 23, the bottom surface 23, or the first edge 41 of the storage portion 22, but instead passes through the outer wall 24 on the folding portion side. This is because, in the case of conventional secondary batteries, the moldability of the pouch 20 is not good, the outer wall 24 on the folding portion side is not formed nearly vertically, and the radius of curvature of the first edge 41 is formed to be large.

[0173] Figure 20 is a schematic diagram of a battery module according to one embodiment of the present invention.

[0174] Large and medium-sized electronic devices such as automobiles require a large output, thus necessitating a large number of secondary batteries 1. To facilitate the easy transport and installation of such secondary batteries 1, a battery module 100 containing a large number of secondary batteries 1 can be manufactured.

[0175] More specifically, the battery module 100 may include a plurality of secondary batteries 1, a housing 2 that houses the plurality of secondary batteries 1, and a cooling unit 3 provided on the inner bottom surface of the housing 2 for cooling the plurality of secondary batteries 1.

[0176] The housing 2 may, but is not limited to, have a generally box shape. The housing 2 can form the external appearance of the battery module 100.

[0177] Multiple secondary batteries 1 can be stacked vertically within the housing 2. More specifically, the multiple secondary batteries 1 can be positioned such that the folding section side outer wall 24 faces downward and the second sealing section 28 faces upward. Thus, the folding section side outer wall 24 can come into contact with the cooling section 3. Since the folding section side outer wall 24 is formed to be longer than the second sealing section 28, the cooling efficiency of each secondary battery 1 by the cooling section 3 can be improved.

[0178] Furthermore, the electrode leads 16 of each secondary battery 1 can be connected to a bus bar (not shown) to transmit power to the outside.

[0179] The cooling unit 3 is adjacent to the outer wall 24 on the folding side of multiple secondary batteries 1, and can cool multiple secondary batteries 1. The cooling unit 3 can cool the heat generated by chemical reactions during the process of electricity generation in the electrode assembly 10 of the secondary battery 1.

[0180] The outer wall 24 on the folding section side of each secondary battery 1 can be in direct contact with the cooling section 3. However, it is not limited to this, and it goes without saying that a mediating agent such as thermal grease can be provided between the outer wall 24 on the folding section side and the cooling section 3.

[0181] The cooling section 3 can have a substantially plate shape and can be manufactured separately from the housing 2 and placed on the inner bottom surface of the housing. Alternatively, the cooling section 3 can form the bottom surface of the housing 2.

[0182] The cooling unit 3 can operate using either air cooling or water cooling, and its configuration and method are not limited. As an example, a cooling unit 3 having a plate shape may have a flow channel through which cooling water flows.

[0183] On the other hand, as described above, the distance between the folding portion side outer wall 24 of each secondary battery 1 and the multiple negative electrodes 14 can be made very close. Therefore, the heat of the electrode assembly 10 can be effectively cooled by the cooling portion 3.

[0184] This eliminates the risk of malfunctions occurring in the circuit of the electrical equipment in which the secondary battery 1 is installed due to high heat, or of the lifespan of the electrical equipment being shortened.

[0185] Furthermore, as described above, the protrusions 30 of each secondary battery 1 can be formed to be very small. Therefore, if a gap is created between the folding section side outer wall 24 and the cooling section 3 due to the protrusions 30, the gap can be formed to be very small, and the amount of thermal grease or other mediating substance injected into the gap can be reduced.

[0186] The above description is merely illustrative of the technical concept of the present invention, and any person with ordinary skill in the art to which the present invention belongs can make various modifications and alterations without departing from the essential characteristics of the present invention.

[0187] Therefore, the embodiments disclosed in this invention are not intended to limit the technical concept of the invention, but rather to illustrate it, and the scope of the technical concept of the invention is not limited by such embodiments.

[0188] The scope of protection of this invention shall be interpreted in accordance with the following claims, and all technical ideas within an equivalent scope shall be interpreted as being included within the scope of the rights of this invention. [Explanation of symbols]

[0189] 1 Secondary battery 10 Electrode assembly 11 Separator 12 electrodes 13 Positive electrode 14 Negative electrode 15 Electrode Tabs 16 electrode leads 17 Insulation 20 pouches 20a Sealant layer 20b Moisture barrier layer 20c surface protection layer 20d stretching auxiliary layer 21 cases 22 Cup section, storage section 23. Bottom (of the cup section), top or bottom (of the storage section) 24 (Cup section) First surface, (Storage section) Folding section side outer wall 25 (Cup section) Second side, (Storage section) Sealing section side outer wall 26 Terrace, ceiling section 27 Side, first sealing section 28. Expansion section, second sealing section 30 Protrusion 41 First Edge 42 Second Edge 43 Third Edge 44 Corner 2 Housing 3. Cooling section 100 Battery Modules

Claims

1. An electrode assembly in which multiple positive electrodes and multiple negative electrodes are alternately stacked with a separator in between, A pair of cases, integrally connected by a folding section and sealed to each other, are formed, and the pouch includes a storage section in which the electrode assembly is housed. The multiple outer walls that form the periphery of the aforementioned storage section are The outer wall on the side of the folding portion, including the aforementioned folding portion, The pair of cases mentioned above are fused together, and the sealing portion is connected to the sealing portion side outer wall, The ends of the plurality of negative electrodes protrude further toward the outer wall on the folding portion side than the ends of the plurality of positive electrodes. The average distance between the end of the negative electrode and the outer wall on the folding portion side is less than the average distance between the end of the negative electrode and the end of the positive electrode. The folding portion has a groove shape extending from one end to the other end of the outer wall on the side of the folding portion. A pouch-type secondary battery, wherein a virtual line that contacts the innermost part of the groove shape, passes through the storage section, and is parallel to the stacking direction of the electrode assembly passes through the top and bottom surfaces of the storage section.

2. The pouch-type secondary battery according to claim 1, wherein at a plurality of points spaced apart from each other in the longitudinal direction of the outer wall on the folding portion side, the average distance between the ends of the plurality of negative electrodes and the outer wall on the folding portion side is 0.6 mm or less, and the overall average distance is 0.5 mm or less.

3. The pouch-type secondary battery according to claim 1 or 2, wherein the maximum distance between the ends of the plurality of negative electrodes and the outer wall on the folding portion side is 0.8 mm or less.

4. The pouch-type secondary battery according to claim 1, wherein the distance between the end of the negative electrode and the outer wall on the folding portion side is less than half the distance between the end of the negative electrode and the end of the positive electrode.

5. The aforementioned storage compartment is The upper or lower surface of the storage section is connected to the outer wall on the folding section side, and a first edge is formed in a rounded shape, The upper or lower surface of the storage section is connected to the outer wall on the sealing section side, and a second edge is formed in a rounded shape, A third edge, formed in a rounded shape, connects the outer wall on the folding section side and the outer wall on the sealing section side. A pouch-type secondary battery according to claim 1, comprising a corner to which the first edge, the second edge, and the third edge are connected.

6. The pouch-type secondary battery according to claim 5, wherein the radius of curvature of the third edge is greater than the radius of curvature of the first edge and the radius of curvature of the second edge.

7. The pouch-type secondary battery according to claim 5, wherein the radius of curvature of the corner increases from the periphery towards the center.

8. The aforementioned pouch is The corner of the sealing portion and the folding portion are connected, and the storage portion includes a protruding portion that extends beyond the corner of the sealing portion in the width direction of the storage portion. The boundary between the protruding portion and the folding portion is The pouch-type secondary battery according to claim 5, wherein the folding portion is located outside the boundary between the first edge and the corner with respect to the length direction of the folding portion.

9. The aforementioned pouch is manufactured by forming a pouch film, The aforementioned pouch film is A sealant layer is formed in the innermost layer, manufactured from the first polymer, A surface protective layer is formed on the outermost layer, manufactured with a second polymer. It is made of a metal containing an aluminum alloy of alloy number AA80XX, and includes a moisture barrier layer laminated between the surface protective layer and the sealant layer, The thickness of the moisture barrier layer is 50 to 80 μm. The pouch-type secondary battery according to claim 1, wherein the thickness of the sealant layer is 60 to 100 μm.

10. The pouch-type secondary battery according to claim 9, wherein the alloy number of the aluminum alloy is AA8021.

11. The aforementioned aluminum alloy is A pouch-type secondary battery according to claim 9, comprising 1.3 wt% to 1.7 wt% of iron, 0.2 wt% or less of silicon, and having a grain size of 10 to 13 μm.

12. The thickness of the moisture barrier layer is 55 to 65 μm. The pouch-type secondary battery according to claim 9, wherein the thickness of the sealant layer is 75 to 85 μm.

13. The aforementioned pouch film is The pouch-type secondary battery according to claim 9, further comprising a stretching auxiliary layer manufactured from a third polymer and laminated between the surface protective layer and the moisture barrier layer.

14. The pouch-type secondary battery according to claim 13, wherein the thickness of the stretching auxiliary layer is 20 to 50 μm.

15. Housing and Multiple secondary batteries are stacked vertically within the aforementioned housing, The housing includes a cooling section provided on the inner bottom surface for cooling the plurality of secondary batteries, The aforementioned secondary battery is An electrode assembly in which multiple positive electrodes and multiple negative electrodes are alternately stacked with a separator in between, A pair of cases, integrally connected by a folding section and sealed to each other, are formed, and the pouch includes a storage section in which the electrode assembly is housed. The multiple outer walls forming the periphery of the storage section are, Including the aforementioned folding portion, the folding portion side outer wall adjacent to the cooling portion, The pair of cases mentioned above are fused together, and the sealing portion is connected to the sealing portion side outer wall, The ends of the plurality of negative electrodes protrude further toward the outer wall on the folding portion side than the ends of the plurality of positive electrodes. The average distance between the end of the negative electrode and the outer wall on the folding portion side is less than the average distance between the end of the negative electrode and the end of the positive electrode. The folding portion has a groove shape extending from one end to the other end of the outer wall on the side of the folding portion. A battery module in which a virtual line, which is in contact with the innermost part of the groove shape, passes through the storage section, and is parallel to the stacking direction of the electrode assembly, passes through the top and bottom surfaces of the storage section.

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