Pouch-type secondary battery and battery module including 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 technology]

[0002] Generally, types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, lithium-ion polymer batteries, etc. These secondary batteries are used not only in 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 (E-bikes), but also in large products that require high output such as electric vehicles and hybrid vehicles, as well as in power storage devices and backup power storage devices that store surplus generated power and new renewable energy.

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

[0004] Secondary batteries are divided into pouch type and can type depending on 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, while the can type houses the electrode assembly in a case made of metal or plastic.

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

[0006] Among such press processes, drawing is performed by inserting a pouch film into a forming device such as a press and applying pressure to the pouch film with a punch to stretch the pouch film. The pouch film is formed of multiple layers, and the moisture barrier layer located in the middle is made of metal. However, in the past, the metal of such moisture barrier layer was an aluminum alloy with a large crystal grain size, and the moisture barrier layer was thin, which reduced formability. Therefore, when forming a cup part in the pouch film, there was a limit to improving the thickness of the bridge and the width of the folding part while forming the depth of the cup part deep. In addition, there was a limit to reducing the size of the butt ear, which reduced the energy density relative to the volume of the secondary battery. Furthermore, there was a limit to manufacturing a sharp shape overall, which resulted in a problem of the secondary battery's appearance being unattractive and its marketability being reduced. Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a pouch-type secondary battery having a beautiful appearance and high energy density by minimizing the distance between the electrodes of an electrode assembly and a pouch.

[0008] Another object of the present invention 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 separators interposed therebetween, and a pouch having a receiving portion formed by sealing a pair of cases connected together by a folding portion, in which the electrode assembly is received. A plurality of outer walls forming a periphery of the receiving portion may include a folding portion-side outer wall including the folding portion, and a sealing portion-side outer wall connected to a sealing portion that fuses the pair of cases together. An average distance between ends of the plurality of negative electrodes and the folding portion-side outer wall may be 0.6 mm or less.

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

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

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

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

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

[0015] The storage section may include a first edge that connects an upper surface or a bottom surface of the storage section to the outer wall of the folding section side and is formed in a round shape, a second edge that connects an upper surface or a bottom surface of the storage section to the outer wall of the sealing section side and is formed in a round shape, a third edge that connects the outer wall of the folding section side and the outer wall of the sealing section side and is formed in a round shape, and a corner where the first edge, the second edge, and the third edge are connected.

[0016] An imaginary line contacting the innermost side of the folding portion and parallel to a stacking direction of the electrode assemblies may pass through at least one of a top surface, a bottom surface, and a first edge of the receiving portion.

[0017] The radius of curvature of the third edge may 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 corner may increase from the periphery to the center.

[0019] The pouch may include a protrusion connecting a corner of the sealing portion and the folding portion and protruding from the corner of the sealing portion in a width direction of the containing portion, and a boundary between the protrusion and the folding portion may be located outside a boundary between the first edge and the corner in a length direction of the folding portion.

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

[0021] The aluminum alloy may have an alloy number of AA8021.

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

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

[0024] The pouch film may further include an orientation assist layer made of a third polymer and laminated between the surface protective layer and the moisture barrier layer.

[0025] The stretching auxiliary layer may have a thickness of 20 to 50 μm.

[0026] 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 separators interposed therebetween, and a pouch having a storage portion formed by sealing a pair of cases connected together by a folding portion, in which the electrode assembly is stored. A plurality of outer walls forming a periphery of the storage portion may include a folding portion-side outer wall including the folding portion, and a sealing portion-side outer wall connected to a sealing portion that fuses the pair of cases together. Ends of the plurality of negative electrodes may protrude further toward the folding portion-side outer wall than ends of the plurality of positive electrodes, and a distance between an end of the negative electrode and the folding portion-side outer wall may be less than half a distance between an end of the negative electrode and an end of the positive electrode.

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

[0028] A battery module according to an embodiment of the present invention may include a housing, a plurality of secondary batteries vertically stacked in the housing, and a cooling unit provided on an inner bottom surface of the housing to cool the plurality of secondary batteries. The secondary battery may include an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators interposed therebetween, and a pouch having a storage unit formed by sealing a pair of cases integrally connected by a folding unit and accommodating the electrode assembly. A plurality of outer walls forming a periphery of the storage unit may include the folding unit, and may include a folding unit-side outer wall adjacent to the cooling unit, and a sealing unit-side outer wall connected to a sealing unit that fuses the pair of cases together. Ends of the plurality of negative electrodes may protrude further toward the folding unit-side outer wall than ends of the plurality of positive electrodes, and a distance between the end of the negative electrode and the folding unit-side outer wall may be less than half the distance between the end of the negative electrode and the end of the positive electrode. Effect 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 plurality of electrodes and the pouch can be shortened compared to the conventional case, thereby enabling the secondary battery to have a sharp appearance.

[0030] In addition, the amount of empty space inside the pouch is reduced, and the energy density of the secondary battery can be improved.

[0031] Also, the cooling efficiency of the electrode assembly by the cooling unit in the battery module can be improved. [Brief description of the drawings]

[0032] [Figure 1] FIG. 2 is an assembly diagram of a pouch-type secondary battery according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating folding of a pouch according to one embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic diagram showing a folded pouch according to one embodiment of the present invention. [Figure 4] 1 is a plan view of a pouch-type secondary battery according to an embodiment of the present invention; [Diagram 5] 4 is an enlarged schematic view of the periphery of an outer wall on a folding portion side in the pouch-type secondary battery according to an embodiment of the present invention; FIG. [Figure 6] 11A-11C are schematic diagrams illustrating folding of a pouch according to another embodiment of the present invention. [Figure 7] FIG. 11 is a schematic diagram showing a pouch according to another embodiment of the present invention folded. [Figure 8] FIG. 2 is a cross-sectional view of a pouch film according to one embodiment of the present invention. [Figure 9] 1 is a graph showing the iron and silicon content of aluminum alloys having alloy number AA8079 and aluminum alloys having alloy number AA8021. [Figure 10] 1 is a graph showing the change in tensile strength, elongation, and grain size depending on the iron content of an aluminum alloy having an alloy number of AA8079 and an aluminum alloy having an alloy number of AA8021. [Figure 11] 1 is an SEM photograph showing enlarged crystal grains of an aluminum alloy having alloy number AA8079 and an aluminum alloy having alloy number AA8021. [Figure 12] 1 is a perspective view illustrating the appearance of a portion of a pouch-type secondary battery according to an embodiment of the present invention; [Figure 13] 13 is a view of the pouch-type secondary battery shown in FIG. 12 as seen from another direction. [Figure 14] FIG. 1 is a perspective view illustrating the appearance of a portion of a conventional pouch-type secondary battery. [Figure 15] 15 is a view of the pouch-type secondary battery shown in FIG. 14 as seen from another direction. [Figure 16] 13 is a CT image showing a measurement of a distance between an outer wall of a folding portion side and a negative electrode according to an embodiment of the present invention. [Figure 17] 13 is a CT image showing a measurement of a distance between an outer wall of a folding portion side and a negative electrode according to an embodiment of the present invention. [Figure 18] This is a CT image measuring the distance between the outer wall of the conventional folding section and the negative electrode. [Figure 19] This is a CT image measuring the distance between the outer wall of the conventional folding section and the negative electrode. [Figure 20] 1 is a schematic diagram of a battery module according to one embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in various different forms and is not limited to the following embodiments.

[0034] In order to clearly explain the present invention, detailed descriptions of parts that are not relevant to the description or related known technologies that may obscure the gist of the present invention have been omitted, and when referring to components in each drawing in this specification, the same or similar reference symbols will be used for the same or similar components throughout the specification.

[0035] Furthermore, the terms and words used in this specification and the claims should not be interpreted in a limited manner to their ordinary or dictionary meanings, but should be interpreted in a manner that is consistent with the technical idea of ​​the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

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

[0037] The pouch-type secondary battery 1 (hereinafter, “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 may be formed by alternately stacking separators 11 and electrodes 12. More specifically, the electrodes 12 may include a positive electrode 13 (see FIG. 5) and a negative electrode 14, and the positive electrode 13 and the negative electrode 14 may be alternately stacked with the separator 11 sandwiched therebetween.

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

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

[0041] The plurality of electrode tabs 15 connected to the positive electrode 13 and the plurality of electrode tabs 15 connected to the negative electrode 14 may protrude in different directions from each other with respect to the electrode assembly 10. However, this is not limited thereto, and the plurality of electrode tabs 15 connected to the positive electrode 13 and the plurality of electrode tabs 15 connected to the negative electrode 14 may protrude in parallel in the same direction with respect to the electrode assembly 10.

[0042] An electrode lead 16 for supplying electricity to the outside of the secondary battery 1 may be connected to the plurality of electrode tabs 15 by spot welding or the like. One end of the electrode lead 16 may be connected to the plurality of electrode tabs 15, and the other end may protrude to the outside of the pouch 20.

[0043] A portion of the electrode lead 16 may be surrounded by an insulating portion 17. For example, the insulating portion 17 may include an insulating tape. The insulating portion 17 may be located between a pair of terraces 26 (described later) of the pouch 20, and in this state, the pair of terraces 26 may be heat-sealed to each other. In this state, a portion of the pair of terraces 26 may be heat-sealed to the insulating portion 17. Thus, the insulating portion 17 prevents electricity generated from the electrode assembly 10 from flowing to the pouch 20 via the electrode lead 16, and the pouch 20 may be maintained sealed.

[0044] Meanwhile, the pouch 20 may be formed by sealing a pair of cases 21 connected to each other at a folding portion 29. The configuration of each case 21 described below will be described based on the pouch 20 being in an unfolded state. The "pouch 20 being in an unfolded state" refers to the pouch 20 being unfolded by removing a predetermined adhesion or sealing that was present in the pouch 20.

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

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

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

[0048] After the electrode assembly 10 is accommodated in the recessed space S1 of any one of the cup parts 22, the folding part 29 can be folded so that the pair of cup parts 22 face each other. Thus, the other cup part 22 can cover the electrode assembly 10 from above. That is, the recessed spaces S1 of the cup parts 22 can be connected to each other, and the electrode assembly 10 can be accommodated in the recessed space S1.

[0049] The indentation depths of the pair of cup portions 22 may be the same. In this case, the pair of cup portions 22 may have a symmetrical shape. However, the present invention is not limited thereto, and the indentation depths of the pair of cup portions 22 may be different from each other. In this case, the pair of cup portions 22 may have an asymmetrical shape.

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

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

[0052] The peripheral portions 24, 25 may surround the recessed space S1 together with the bottom portion 23. More specifically, the peripheral portions 24, 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. The second surfaces 25 may be provided in three portions connected to each other to form a U-shape.

[0053] The terrace 26 may be located on the periphery of the cup portion 22. More specifically, the terrace 26 may be connected to upper ends of the plurality of second surfaces 25 of the cup portion 22. Therefore, the terrace 26 may have a substantially U-shape.

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

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

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

[0057] With the electrode assembly 10 placed between the pair of cup portions 22 of the pouch 20, the folding portion 29 is folded and the pair of terraces 26 are fused to each other to form a secondary battery 1 in which the pair of cases 21 are sealed to each other.

[0058] The secondary battery 1 may include a receiving portion for receiving the electrode assembly 10, and a sealing portion in which the pair of cases 21 are fused to each other.

[0059] The receiving portion is formed by connecting cup portions 22 of a pair of cases 21, and will be denoted below for convenience with the same reference numeral "22" as the cup portion 22. The sealing portion is formed by fusing terraces 26 of a pair of cases 21 to each other, and will be denoted below for convenience with the same reference numeral "26" as the terraces.

[0060] The receiving portion 22 may include a bottom surface and a top surface covering both sides of the electrode assembly 10 in the stacking direction of the electrode assembly 10, and a plurality of outer walls forming the periphery of the receiving portion 22 and surrounding the periphery of the electrode assembly 10. The plurality of outer walls may include a folding portion-side outer wall including the folding portion 29, and a sealing portion-side outer wall connected to the sealing portion 26.

[0061] More specifically, the bottom surface of the receiving portion 22 may be formed from the bottom 23 of one of the cup portions 22, and the top surface of the receiving portion 22 may be formed from the bottom 23 of the other of the cup portions 22. Hereinafter, the bottom and top surfaces of the receiving portion 22 will be denoted by the same reference numeral "23" as the bottom 23 of the cup portion 22.

[0062] In addition, the outer wall of the storage part 22 on the folding part side may be composed of a pair of first surfaces 24 of the cup part 22 and the folding part 29. Hereinafter, the outer wall of the storage part 22 on the folding part side will be indicated by the same reference numeral "24" as the first surface 24 of the cup part 22.

[0063] When the cup portions 22 of the pair of cases 21 are formed to have the same or similar depth, the folding portion 29 can be located at the center of the folding portion side outer wall 24 in the stacking direction of the electrode assembly 10.

[0064] In addition, the outer wall of the receiving part 22 on the sealing part side may be composed of the second surface 25 of the pair of cup parts 22. Hereinafter, the outer wall of the receiving part 22 on the sealing part side will be indicated by the same reference numeral "25" as the second surface 25 of the cup part 22.

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

[0066] The sealing part 26 may include a first sealing part formed by welding the sides 27 of the pair of cases 21 to each other, and a second sealing part formed by welding the extension parts 28 of the pair of cases 21 to each other. Hereinafter, the first sealing part will be denoted by "27", which is the same reference number as the side 27, and the second sealing part will be denoted by "28", which is the same reference number as the extension part 28.

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

[0068] The second sealing part 28 may extend in the length direction of the secondary battery 1 and protrude to the opposite side of the folding part side outer wall 24. The second sealing part 28 may be folded at least once toward the receiving part 22, thereby reducing the width of the secondary battery 1. For example, the second sealing part 28 may be folded twice in a double side folding (DSF) manner.

[0069] FIG. 5 is a schematic enlarged view of the periphery of the outer wall on the folding portion side inside the pouch-type secondary battery according to one embodiment of the present invention.

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

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

[0072] Meanwhile, the ends 14a of the plurality of negative electrodes 14 and the ends 13a of the plurality of positive electrodes 13 can be spaced apart from the folded portion-side outer wall 24. However, in the past, the distance between the ends 14a of the plurality of negative electrodes 14 and the folded portion-side outer wall 24 was relatively large, which limited the ability to manufacture a secondary battery with a sharp exterior shape.

[0073] Therefore, it is preferable to separate the ends 14a of the negative electrodes 14 from the outer wall 24 of the folded portion, with the mutual distance being minimized.

[0074] For this purpose, it is desirable to improve the formability of the pouch film, which is the base material of the pouch 20. The pouch film can be formed into the pouch 20 by a forming process using a die and a punch. The forming process is a well-known technique, and therefore a detailed description thereof will be omitted.

[0075] By improving the formability of the pouch film, the tolerance of the forming process is reduced, enabling precise manufacturing, and thus minimizing the gap between the ends 14a of the multiple negative electrodes 14 and the folding portion side outer wall 24. The configuration of the pouch film for improving the formability will be described in detail below.

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

[0077] In the following, the contents that overlap with those described above will be cited, and the differences will be mainly described.

[0078] The pouch 20 according to the present embodiment may be formed by sealing a first case 21a and a second case 21b formed at a folding portion 29 to each other. The first case 21a may be formed with a cup portion 22, and the second case 21b may not be formed with the cup portion 22.

[0079] The second case 21b may have a substantially flat plate shape. A part of the second case 21b may cover the cup portion 22 of the first case 21a, and another part of the second case 21b may be fused to the terrace 26 of the first case 21a.

[0080] More specifically, after the electrode assembly 10 is accommodated 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 according to this embodiment can be formed by the bottom part 23 of the cup part 22 of the first case 21a, and the upper surface of the storage section 22 can be formed by a part of the second case 21b.

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

[0083] In addition, the folding portion side outer wall of the storage portion 22 may be composed 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 may be located on the upper part of the folding portion side outer wall 24 with respect to the stacking direction of the electrode assembly 10.

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

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

[0086] The pouch film according to the present embodiment may be a base material of the pouch 20. The pouch 20 may be manufactured by drawing and forming the pouch film. Hereinafter, for convenience, the pouch film will be indicated by the same reference numeral as the pouch 20, '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 may form the innermost layer of the pouch 20. More specifically, in the secondary battery 1, the sealant layer 20a may be the inner surface of the storage section 22 or may be a layer fused to each other by a pair of sealing sections 26.

[0089] The sealant layer 20a must be insulating since it comes into contact with the electrode assembly 10, and must be corrosion resistant since it also comes into contact with the electrolyte injected into the storage section 22 during the manufacturing process of the secondary battery 1. In addition, the sealant layer 20a must have high sealing properties since it must completely seal the inside of the storage section 22 to block material transfer between the inside and the outside. In other words, the sealing section 26 where the sealant layers 20a are bonded together must have excellent thermal adhesive strength.

[0090] The sealant layer 20a may have a first polymer material, and the first polymer may be one or more selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. 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, and chemical properties such as corrosion resistance, and is mainly used to manufacture the sealant layer 20a. Furthermore, it may be composed of casted polypropylene, acid modified polypropylene, or polypropylene-butylene-ethylene terpolymer. Here, the acid modified polypropylene may be MAH PP (maleic anhydride polypropylene). Also, the sealant layer 20a may have a single film structure made of any one material, or a composite film structure formed by layers of two or more materials.

[0091] The thickness of the sealant layer 20a may be 60 to 100 μm, and particularly 75 to 85 μm. If the thickness of the sealant layer 20a is less than 60 μm, there may be a problem of reduced sealing durability, such as internal destruction during sealing. If the thickness of the sealant layer 20a is greater than 100 μm, the overall thickness of the pouch becomes excessively thick, and the energy density relative to the volume of the secondary battery 1 may instead decrease.

[0092] The moisture barrier layer 20b is laminated between the surface protective layer 20c and the sealant layer 20a to ensure the mechanical strength of the pouch, block the ingress and egress of gas or moisture from the secondary battery 1, and prevent electrolyte leakage. The moisture barrier layer 20b may be made of metal, more specifically, aluminum. Aluminum can ensure a certain level of mechanical strength, is light in weight, and can ensure the complementation of electrochemical properties of the electrode assembly 10 and the electrolyte, heat dissipation, etc.

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

[0094] Such an aluminum alloy may include various materials, such as one or more 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 manufacture the moisture barrier layer 20b according to an embodiment of the present invention will be provided later.

[0095] Conventionally, the moisture barrier layer has a thickness of about 30 to 50 μm, particularly 40 μm, resulting in poor formability. Therefore, even if the pouch film is drawn, the depth of the cup portion 22 becomes deep, and there is a limit to forming the peripheral portions 24, 25 of the cup portion 22 nearly vertically, and there is also a limit to reducing the radius of curvature of the edge connecting the bottom portion 23 of the cup portion 22 and the peripheral portions 24, 25 in a rounded shape.

[0096] If the thickness of the moisture barrier layer 20b is increased to more than about 80 μm in order to solve this problem, not only will the manufacturing cost increase, but the overall thickness of the pouch will become excessively thick, resulting in a problem of a decrease in 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 reduce the overall thickness of the pouch, there will be a problem of a decrease in sealing durability as described above.

[0097] According to the present embodiment, this is improved, and the moisture barrier layer 20b may have a thickness of 50 μm to 80 μm, and particularly 55 μm to 65 μm. Therefore, the formability of the moisture barrier layer 20b is improved, and when the pouch film 20 is drawn, the depth of the cup portion 22 can be formed deep, the peripheral portions 24, 25 of the cup portion 22 become nearly vertical, and the curvature radius of the edge connecting the bottom portion 23 and the peripheral portions 24, 25 of the cup portion 22 can be reduced. As a result, the volume of the recessed space S1 is increased, so that a larger electrode assembly 10 can be accommodated, and the energy efficiency relative to the volume of the secondary battery 1 can be increased. In addition, the manufacturing cost does not increase significantly, and the thickness of the entire pouch does not increase significantly even if the thickness of the sealant layer 20a is not reduced, and the sealing durability does not decrease.

[0098] The surface protective layer 20c is formed on the outermost layer of the pouch 20 to protect the secondary battery 1 from external friction and impact, and to electrically insulate the electrode assembly 10 from the outside. More specifically, in the secondary battery 1, the surface protective 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 materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, 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. In addition, the surface protective layer 20c may have a single film structure made of any one material, or a composite film structure formed by forming layers of two or more materials.

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

[0101] On the other hand, PET is inexpensive, has excellent durability, and is excellent in electrical insulation, but has poor adhesion to aluminum, which is often used as the moisture barrier layer 20b, and their behaviors when stretched by applying stress may differ from each other. 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 peel off during drawing. Therefore, the moisture barrier layer 20b may not be stretched uniformly, which may cause a problem of reduced formability.

[0102] To solve this problem, the pouch film 20 may further include a stretching assist 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, and can prevent 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 may be one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. In particular, nylon resin is easily bonded to the polyethylene terephthalate (PET) of the surface protective layer 20c, and has a similar behavior when stretched to the aluminum alloy of the moisture barrier layer 20b, so nylon resin can be mainly used as the third polymer. In addition, the stretching auxiliary layer 20d may have a single film structure made of any one material, or a composite film structure formed by forming layers of two or more materials.

[0105] Conventionally, the moisture barrier layer has a thickness of about 40 μm, and therefore the stretching auxiliary layer has a thickness of about 15 μm, which is considerably smaller. That is, the ratio of the thickness of the stretching auxiliary layer to the moisture barrier layer is 1:2.67, and the ratio of the thickness of the moisture barrier layer is considerably higher. However, as described above, according to the present embodiment, the moisture barrier layer 20b has a thickness of about 50 to 80 μm, particularly 55 to 65 μm, so that the formability of the moisture barrier layer 20b is improved. In this case, in order to improve the formability of the stretching auxiliary layer 20d as well, the stretching auxiliary layer 20d may have a thickness of 20 μm to 50 μm, particularly preferably 25 to 38 μm. If the stretching auxiliary layer 20d is thinner than 20 μm, it cannot respond to the improved formability of the moisture barrier layer 20b, and may be damaged during stretching. On the other hand, if the thickness is greater than 50 μm, the overall thickness of the pouch will be thick, which may increase the volume of the secondary battery 1 and reduce the energy density. In particular, according to this embodiment, the thickness ratio of the stretching auxiliary layer 20d to the moisture barrier layer 20b can be less than 1:2.5. That is, the thickness ratio of the stretching auxiliary layer 20d can be increased more than in the past. However, if the thickness of the stretching auxiliary layer 20d becomes excessively thick, the overall thickness of the pouch will be thick, so in order to avoid the excessive thickness, the thickness ratio can be greater than 1:1.5. That is, the thickness ratio can be 1:1.5 to 1:2.5.

[0106] FIG. 9 is a graph showing the iron and silicon contents of aluminum alloys having alloy number AA8079 and aluminum alloys having alloy number AA8021.

[0107] When the aluminum alloy contains a large amount of iron, its mechanical strength is improved, and when the iron content is small, its flexibility is improved. Among the aluminum alloys, alloy number AA8079 contains 0.6 wt% to 1.2 wt% of iron and 0.3 wt% or less of silicon. That is, when the moisture barrier layer 20b is manufactured using an aluminum alloy with alloy number AA8079, the relatively small amount of iron contained therein can improve flexibility, but the strength is reduced and there may be a limit to formability.

[0108] Meanwhile, among the aluminum alloys, alloy number AA8021 may contain 1.2wt% to 1.7wt%, particularly 1.3wt% to 1.7wt% of iron, and 0.2wt% or less of silicon. When the moisture barrier layer 20b is manufactured using the aluminum alloy with alloy number AA8021, the tensile strength and elongation rate can be improved since the iron content is relatively high.

[0109] Meanwhile, the relationship between tensile strength and elongation rate when a tensile force is applied to a certain material can be graphed. In this case, the vertical axis of the graph represents tensile strength, and the horizontal axis represents elongation rate. The area under the graph represents the toughness of the material. Toughness indicates the degree to which a material is resistant to breakage, and the higher the toughness, the more the material can be stretched before breaking.

[0110] Therefore, when the moisture barrier layer 20b is manufactured using the aluminum alloy of alloy number AA8021, the tensile strength and elongation are improved, so that the toughness is increased and the formability is improved.

[0111] FIG. 10 is a graph showing the changes in tensile strength, elongation, and grain size depending on the iron content of aluminum alloys having alloy numbers AA8079 and AA8021, and FIG. 11 is a SEM photograph showing enlarged grains of aluminum alloys having alloy numbers AA8079 and AA8021.

[0112] As shown in Figure 10, the tensile strength, elongation, and grain size change depending on the iron content of the aluminum alloy. Specifically, the tensile strength and elongation are proportional to the iron content, so as the iron content increases, the tensile strength and elongation also increase. Meanwhile, the grain size is inversely proportional to the iron content, so as the iron content increases, the grain size decreases.

[0113] As described above, the aluminum alloy AA8079 contains 0.6 wt% to 1.2 wt% of iron, and therefore has a relatively large grain size of 13 μm to 21 μm, as shown in Fig. 11. Therefore, the internal stress is not sufficiently dispersed during stretching, and pinholes increase, resulting in a problem of reduced formability of the pouch film 20.

[0114] Meanwhile, among aluminum alloys, alloy number AA8021 contains 1.2wt% to 1.7wt% of iron, and therefore has a relatively small crystal grain size of 10μm to 13μm, as shown in Fig. 11. Therefore, the internal stress can be dispersed more when stretched, and pinholes can be reduced, thereby improving the formability of the pouch film 20.

[0115] Therefore, the aluminum alloy forming the moisture barrier layer 20b according to the present embodiment may contain 1.2wt% to 1.7wt% of iron, particularly 1.3wt% to 1.7wt%. The aluminum alloy may contain 0.2wt% or less of silicon. The grain size may be 10μm to 13μm. That is, in the present embodiment, the aluminum alloy for manufacturing the moisture barrier layer 20b may be alloy number AA8021.

[0116] Such a pouch film 20 has improved formability, and the cup portion 22 of the pouch 20 can be formed deeper, the peripheral portions 24, 25 of the cup portion 22 become nearly vertical, and the radius of curvature of the edge connecting the bottom portion 23 of the cup portion 22 to the peripheral portions 24, 25 can be reduced, so that a larger and thicker electrode assembly 10 can be accommodated. Therefore, the energy efficiency per volume of the secondary battery 1 including such a pouch 20 can be increased.

[0117] FIG. 12 is a perspective view showing a partial exterior appearance of a pouch-type secondary battery according to an embodiment of the present invention, and FIG. 13 is a view showing the pouch-type secondary battery shown in FIG. 12 as viewed from another direction.

[0118] In the secondary battery 1, the storage section 22 may include a first edge 41 connecting the top or bottom surface 23 of the storage section 22 to the folding section side outer wall 24, a second edge 42 connecting the top or bottom surface 23 of the storage section 22 to the sealing section side outer wall 25, a third edge 43 connecting the folding section side outer wall 24 to the sealing section side outer wall 25, 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 may be formed in a rounded shape. More specifically, each of the edges 41, 42, and 43 may be curved with a predetermined radius of curvature, and the radius of curvature may be constant or variable along the rounding direction.

[0120] The first edge 41 may be rounded to connect the top or bottom surface 23 of the storage section 22 to the folding section side outer wall 24. The first edge 41 may extend in the length direction of the storage section 22 and may have a relatively constant radius of curvature along the extension direction.

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

[0122] The third edge 43 may be rounded to connect the folding portion side outer wall 24 and the sealing portion side outer wall 25. The third edge 43 may extend in the stacking direction of the electrode assembly 10, i.e., in the height direction of the storage portion 22, and may 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 may be formed by connecting the adjacent first edge 41, second edge 42, and third edge 43. In order to prevent excessive stress from concentrating on the corner 44 during the forming process of the pouch 20, the corner 44 may have a rounded curved shape in the round direction of each of the first edge 41, the second edge 42, and the third edge 43.

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

[0126] More specifically, the radius of curvature in the round direction of the first edge 41 can be increased from the boundary B1 between the first edge 41 and the corner 44 toward the center of the corner 44.

[0127] Furthermore, the radius of curvature of the second edge 42 in the round direction can be increased from the boundary between the second edge 42 and the corner 44 toward the center of the corner 44 .

[0128] Furthermore, the radius of curvature of the third edge 43 in the round direction can be increased from the boundary between the third edge 43 and the corner 44 toward the center of the corner 44 .

[0129] Meanwhile, the pouch 20 may further include a protrusion 30 that connects a corner of the sealing portion 26 to the outer wall 24 of the folding portion and protrudes from the corner of the sealing portion 26 in the width direction of the receiving portion 22 .

[0130] More specifically, the protrusion 30 may connect the corner 27a of the first sealing portion 27 and the folding portion 29, and may protrude outward in a convex shape with respect to the width direction of the storage portion 22. At the same time, the protrusion 30 may have a shape that is curved upward or downward.

[0131] In the process of forming the pouch 20, not only the cup portion 22 is stretched in a limited manner, but also the portion adjacent to the cup portion 22 at the terrace 26 is finely stretched as a whole. Therefore, when the folding portion 29 is folded in the process of manufacturing the secondary battery 1, the finely stretched portions are accumulated, and the protrusion 30 may be formed.

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

[0133] The boundary B2 between the protruding portion 30 and the folding portion 29 may be located outside the boundary B1 between the first edge 41 and the corner 44 in the length direction of the folding portion 29. In other words, the boundary B2 between the protruding portion 30 and the folding portion 29 may be located at a point where it overlaps with the corner 44, not the first edge 41, in the height direction of the storage portion 22.

[0134] This is a feature that can be realized by improving the formability of the pouch film 20 compared to the conventional case. By minimizing the length or size of the protrusion 30, the external appearance of the secondary battery 1 can be formed sharply, and the energy density of the secondary battery 1 can be improved. In addition, the cooling efficiency of the cooling unit 3 in the battery module 100 (see FIG. 20) described later can be improved.

[0135] FIG. 14 is a perspective view showing a partial external appearance of a conventional pouch-type secondary battery, and FIG. 15 is a view of the pouch-type secondary battery shown in FIG. 14 as seen from another 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 as those used for the respective components of secondary battery 1 of the present invention will be used in the description.

[0137] In the conventional secondary battery, the formability of the pouch 20 is low, and the radius of curvature of the first edge 41, the second edge 42, and the third edge 43 is relatively large. Therefore, there is a limit to how sharp the appearance can be formed, and there is a problem that wrinkles and creases occur.

[0138] In addition, wrinkles may occur at the ends of the folding section side outer wall 24 and the sealing section side outer wall 25, 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 varies excessively along the extension direction.

[0139] For example, wrinkles may occur at the end of the outer wall 24 on the folding section side, which may cause the radius of curvature of the first edge 41 to suddenly increase or decrease at the portion adjacent to the corner 44. This causes a problem of the shape of the corner 44 becoming irregularly deformed.

[0140] In addition, the groove shape formed by the folding portion 29 may not continue to the end of the folding portion side outer wall 24 but may disappear midway, or the protrusion 30 may not be connected to the folding portion 29 at the folding portion side outer wall 24.

[0141] In addition, even if the protrusion 30 is connected to the folding portion 29, the boundary B2 between the protrusion 30 and the folding portion 29 can be located outside the boundary B1 between the first edge 41 and the corner 44 in the length direction of the folding portion 29. That is, the boundary B2 between the protrusion 30 and the folding portion 29 can be located at a point where it overlaps with the first edge 41 in the height direction of the storage portion 22. This is the opposite configuration to the present invention, and means that the protrusion 30 of the conventional secondary battery is formed to be longer and larger.

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

[0143] More specifically, Fig. 16 is a CT (Computerized Tomography) photograph measured at a first point P1 in Fig. 4, and Fig. 17 is a CT photograph measured at a second point P2 in Fig. 4. However, the method for measuring the distance between the outer wall 24 on the folding portion side and the negative electrode 14 is not limited to this, and the measurement can also be performed using methods such as MRI (Magnetic Resonance Imaging) and X-ray.

[0144] The present invention improves the moldability of the pouch 20, thereby allowing the ends 14a (see FIG. 5) of the plurality of negative electrodes 14 to be kept apart from the outer wall 24 of the folding portion and the distance between them to be as close as possible. In this case, the distance may refer to the horizontal distance between the ends 14a (see FIG. 5) of the plurality of negative electrodes 14 and the outer wall 24 of the folding portion when the secondary battery 1 is placed on a horizontal surface such as a floor.

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

[0146] Preferably, the distance between the end 14a of the negative electrode 14 and the outer wall 24 of the folded portion is less than half the distance between the end 14a of the negative electrode 14 and the end 13a of the positive electrode 13.

[0147] That is, the distance between the end 14a of the negative electrode 14 and the folded section side outer wall 24 can be shorter than half the distance that the negative electrode 14 protrudes toward the folded section side outer wall 24 relative to the positive electrode 13. This can be easily confirmed with the naked eye in Figures 16 and 17.

[0148] This minimizes void space within the pouch 20, improves the cooling efficiency of the cooling section 3 (see FIG. 20) described below, and enables the energy density of the secondary battery 1 to be increased.

[0149] More specifically, the average distance between the ends 14a of the negative electrodes 14 and the folding portion side outer wall 24 may be 0.6 mm or less. The average distance may be measured at any one point in the extension direction of the folding portion side outer wall 24. The average distance may vary along the extension direction of the folding portion side outer wall 24.

[0150] In addition, the maximum distance between the ends 14a of the negative electrodes 14 and the folded portion-side outer wall 24 may 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 negative electrodes 14 and the folded portion-side outer wall 24 becomes excessively large, resulting in a problem of non-uniform quality of the secondary batteries 1.

[0151] In addition, each of a plurality of average distances measured at a plurality of points spaced apart in the extension direction of the outer wall 24 on the folding portion side may be 0.6 mm or less, and the overall average distance, which is the average of the plurality of average distances, may be 0.5 mm or less.

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

[0153] As a result, the distance between the ends 14a of the negative electrodes 14 and the outer wall 24 on the folding portion side along the extension direction of the outer wall 24 on the folding portion side can be generally kept close.

[0154] If the overall average distance exceeds 0.5 mm, the void space within the pouch 20 will become large, reducing the cooling efficiency of the cooling section 3 (see FIG. 20) described below and causing a problem of a reduced energy density of the secondary battery 1.

[0155] Furthermore, if the average distance exceeds 0.6 mm even in a certain portion of the outer wall 24 on the folding section side, that portion will protrude compared to the surrounding area, limiting the ability of the secondary battery 1 to have a beautiful appearance, and the cooling of that portion by the cooling section 3 (see Figure 20) described below will not be performed properly, which may result in a localized temperature rise.

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

[0157] In addition, at the second point P2, 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 portion side were measured to be 0.22 mm, 0.54 mm, 0.41 mm, 0.57 mm, and 0.39 mm, respectively, with the maximum distance being 0.57 mm and the average distance being 0.43 mm.

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

[0159] That is, the present invention can confirm that the maximum distance at each of the points P1 and P2 is 0.8 mm or less, the average distance at each of the points P1 and P2 is 0.6 mm or less, and the overall average distance is 0.5 mm or less.

[0160] Meanwhile, an imaginary line VP that contacts the innermost side of the folding portion 29 and is parallel to the stacking direction of the electrode assembly 10 can pass through at least one of the top surface 23 , the bottom surface 23 , or the first edge 41 of the storage portion 22 .

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

[0162] Such a configuration can be realized by improving the moldability of the pouch 20 of the present invention, thereby minimizing void space within the pouch 20 and increasing the cooling efficiency of the cooling section 3 (see FIG. 20) described below, thereby enabling the energy density of the secondary battery 1 to be increased.

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

[0164] More specifically, FIG. 18 is a CT photograph taken at a portion of a conventional secondary battery corresponding to the first point P1, and FIG. 19 is a CT photograph taken at a portion of a conventional secondary battery corresponding to the second point P2.

[0165] 18 and 19 as comparative examples, it can be seen that the distance between end 14a of negative electrode 14 and outer wall 24 on the folded portion side is more than half the distance between end 14a of negative electrode 14 and end 13a of positive electrode 13. Furthermore, it can be seen that the distance between end 14a of some negative electrodes 14 and outer wall 24 on the folded portion side is more than the distance between end 14a of negative electrode 14 and end 13a of positive electrode 13.

[0166] Therefore, in the conventional secondary battery, a large void space is formed in the pouch 20, which causes a problem that the cooling efficiency and energy density of the secondary battery are low.

[0167] In addition, at the portion corresponding to 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 of the folding portion side were measured to be 0.89 mm, 1.19 mm, 0.84 mm, 0.94 mm, and 1.23 mm, respectively, with the maximum distance being 1.23 mm and the average distance being 1.01 mm.

[0168] In addition, at the portion corresponding to the second point P2, 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 portion side were measured to be 0.90 mm, 0.89 mm, 0.89 mm, 1.22 mm, and 0.75 mm, respectively, with the maximum distance being 1.22 mm and the average distance being 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] That is, in the case of the comparative example, unlike the present invention, it can be confirmed that the maximum distance at each point is more than 0.8 mm, the average distance at each point is more than 0.6 mm, and the overall average distance is more than 0.5 mm.

[0171] 18, it can be seen that the groove shape of the folding part 29 disappears due to the wrinkles of the folding part side outer wall 24 at the portion corresponding to the first point P1, so it is impossible to define the imaginary line.

[0172] 19, the imaginary line VP may be defined in the portion corresponding to the second point P2, but it can be seen that the imaginary line VP does not pass through the top surface 23, the bottom surface 23 or the first edge 41 of the receiving portion 22, but instead passes through the folding portion side outer wall 24. This is because, in the case of a conventional secondary battery, the formability of the pouch 20 is not good, the folding portion side outer wall 24 is not formed nearly vertically, and the first edge 41 has a large radius of curvature.

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

[0174] Medium to large electronic devices such as automobiles require high output, and therefore require a large number of secondary batteries 1. In order to easily move and install such secondary batteries 1, a battery module 100 including 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 accommodates the plurality of secondary batteries 1, and a cooling section 3 provided on the inner bottom surface of the housing 2 to cool the plurality of secondary batteries 1.

[0176] The housing 2 may have a substantially box-like shape, but is not limited thereto. The housing 2 may form the outer appearance of the battery module 100.

[0177] A plurality of secondary batteries 1 may be stacked vertically in the housing 2. More specifically, a plurality of secondary batteries 1 may be stood such that the folding section side outer wall 24 faces downward and the second sealing section 28 faces upward. Therefore, the folding section side outer wall 24 may contact the cooling section 3. Since the folding section side outer wall 24 is formed longer than the second sealing section 28, the cooling efficiency of each secondary battery 1 by the cooling section 3 may be improved.

[0178] In addition, the electrode leads 16 of each secondary battery 1 are 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 of the folding unit of the secondary batteries 1 and can cool the secondary batteries 1. The cooling unit 3 can cool heat generated by a chemical reaction in the process of generating electricity in the electrode assembly 10 of the secondary battery 1.

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

[0181] The cooling unit 3 may have a substantially plate-like shape and may be manufactured separately from the housing 2 and disposed on the inner bottom surface of the housing 2. Alternatively, the cooling unit 3 may form the bottom surface of the housing 2.

[0182] The cooling unit 3 may be air-cooled or water-cooled, and the configuration and method thereof are not limited. For example, a flow path through which cooling water flows may be formed inside the cooling unit 3 having a plate shape.

[0183] Meanwhile, as described above, the distance between the outer wall 24 of the folding part of each secondary battery 1 and the plurality of negative electrodes 14 can be formed very close to each other. Therefore, the heat of the electrode assembly 10 can be effectively cooled by the cooling part 3.

[0184] This can eliminate the risk of malfunction of the circuitry of an electrical device in which the secondary battery 1 is installed or of the life of the electrical device being shortened due to high heat.

[0185] Also, as described above, the protrusion 30 of each secondary battery 1 can be formed very small. Therefore, if a gap occurs between the folding part side outer wall 24 and the cooling part 3 due to the protrusion 30, the gap is formed very small, and the amount of a medium such as thermal grease to be injected into the gap can be reduced.

[0186] The above description is merely an illustrative example of the technical concept of the present invention, and various modifications and variations are possible by those having ordinary knowledge in the technical field to which the present invention pertains without departing from the essential characteristics of the present invention.

[0187] Therefore, the embodiments disclosed in the present invention are for the purpose of explanation and not for the purpose of limiting the technical idea of ​​the present invention, and such embodiments do not limit the scope of the technical idea of ​​the present invention.

[0188] The scope of protection of the present invention should be interpreted according to the following claims, and all technical ideas within the scope equivalent thereto should be interpreted as being included in the scope of the present invention. [Explanation of symbols]

[0189] 1 Secondary battery 10 Electrode assembly 11 Separator 12 electrodes 13 Positive electrode 14 Negative electrode 15 Electrode tab 16 Electrode Lead 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 (cup part), top or bottom of (storage part) 24 (Cup section) first surface, (Storage section) Folding section side outer wall 25 (Cup section) second surface, (storage section) sealing section side outer wall 26 Terrace, ceiling section 27 Side, first sealing part 28 Extension section, second sealing section 30 Protrusion 41 First Edge 42 2nd Edge 43 Third Edge 44 Corner 2. Housing 3. Cooling section 100 Battery Module

Claims

1. an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators interposed therebetween; a pouch formed by sealing a pair of cases that are integrally connected by a folding portion and have a receiving portion in which the electrode assembly is received; The plurality of outer walls forming the periphery of the storage section include A folding portion side outer wall including the folding portion; a sealing part-side outer wall connected to a sealing part formed by fusing the pair of cases together; The average distance between the ends of the plurality of negative electrodes and the outer wall of the folding portion is 0.6 mm or less; The maximum distance between the ends of the negative electrodes and the outer wall of the folding portion is 0.8 mm or less; the folding portion forming a part of the folding portion side outer wall has a groove shape extending from one end of the folding portion side outer wall to the other end thereof and formed toward the electrode assembly accommodated in the accommodation portion, The storage section includes: A first edge that connects the top surface or the bottom surface of the storage section to the outer wall of the folding section and is formed in a round shape; A second edge that is rounded and connects the top or bottom surface of the storage portion to the outer wall of the sealing portion; a third edge that connects the folding portion side outer wall and the sealing portion side outer wall and is formed in a round shape; having a radius of curvature of the third edge is greater than a radius of curvature of the first edge and a radius of curvature of the second edge.

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

3. the ends of the negative electrodes protrude further toward the outer wall of the folding portion than the ends of the positive electrodes; The pouch-type secondary battery according to claim 1 , wherein an average distance between an end of the negative electrode and an outer wall on the folding portion side is less than an average distance between an end of the negative electrode and an end of the positive electrode.

4. 4. The pouch-type secondary battery according to claim 3, wherein a distance between the end of the negative electrode and the outer wall on the folding portion side is less than half a distance between the end of the negative electrode and the end of the positive electrode.

5. The storage section includes: The pouch-type secondary battery of claim 1 , further comprising a corner where the first edge, the second edge, and the third edge are connected.

6. The pouch-type secondary battery of claim 5 , wherein an imaginary line contacting an innermost side of the folding portion and parallel to a stacking direction of the electrode assembly passes through at least one of an upper surface, a bottom surface, and a first edge of the receiving portion.

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

8. The pouch comprises: a protrusion connecting a corner of the sealing part and the folding part and protruding from the corner of the sealing part in a width direction of the receiving part, The boundary between the protruding portion and the folding portion is The pouch-type secondary battery according to claim 5 , wherein the folded portion is located outside a boundary between the first edge and the corner in a longitudinal direction of the folded portion.

9. The pouch is manufactured by forming a pouch film, The pouch film is a sealant layer formed on the innermost layer and made of a first polymer; a surface protective layer formed on the outermost layer and made of a second polymer; The present invention relates to a method for manufacturing a sealing member, comprising: forming a sealing member using a sealing material having a sealing layer and a sealing member having a sealing property; The moisture barrier layer has a thickness of 50 to 80 μm.

2. The pouch-type secondary battery according to claim 1, wherein the sealant layer has a thickness of 60 to 100 μm.

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

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

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

13. The pouch film is The pouch-type secondary battery according to claim 9 , further comprising an orientation-assist layer made of a third polymer and laminated between the surface protection layer and the moisture barrier layer.

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

15. an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators interposed therebetween; a pouch formed by sealing a pair of cases that are integrally connected by a folding portion and have a receiving portion in which the electrode assembly is received; The outer walls forming the periphery of the storage section include A folding portion side outer wall including the folding portion; a sealing part-side outer wall connected to a sealing part formed by fusing the pair of cases together; the ends of the negative electrodes protrude further toward the outer wall of the folding portion than the ends of the positive electrodes; a distance between an end of the negative electrode and an outer wall of the folding portion side is less than half a distance between an end of the negative electrode and an end of the positive electrode; The maximum distance between the ends of the negative electrodes and the outer wall of the folding portion is 0.8 mm or less; the folding portion forming a part of the folding portion side outer wall has a groove shape extending from one end of the folding portion side outer wall to the other end thereof and formed toward the electrode assembly accommodated in the accommodation portion, The storage section includes: A first edge that connects the top surface or the bottom surface of the storage section to the outer wall of the folding section and is formed in a round shape; A second edge that is rounded and connects the top or bottom surface of the storage portion to the outer wall of the sealing portion; a third edge that connects the folding portion side outer wall and the sealing portion side outer wall and is formed in a round shape; having a radius of curvature of the third edge is greater than a radius of curvature of the first edge and a radius of curvature of the second edge.

16. Housing and a plurality of secondary batteries vertically stacked within the housing; a cooling section provided on an inner bottom surface of the housing for cooling the plurality of secondary batteries; The secondary battery is an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators interposed therebetween; a pouch formed by sealing a pair of cases that are integrally connected by a folding portion and have a receiving portion in which the electrode assembly is received; The outer walls forming the periphery of the storage section include a folding portion side outer wall including the folding portion and adjacent to the cooling portion; a sealing part-side outer wall connected to a sealing part formed by fusing the pair of cases together; the average distance between the ends of the negative electrodes and the outer wall of the folding portion is 0.6 mm or less; The maximum distance between the ends of the negative electrodes and the outer wall of the folding portion is 0.8 mm or less; the folding portion forming a part of the folding portion side outer wall has a groove shape extending from one end of the folding portion side outer wall to the other end thereof and formed toward the electrode assembly accommodated in the accommodation portion, The storage section includes: A first edge that connects the top surface or the bottom surface of the storage section to the outer wall of the folding section and is formed in a round shape; A second edge that is rounded and connects the top or bottom surface of the storage portion to the outer wall of the sealing portion; a third edge that connects the folding portion side outer wall and the sealing portion side outer wall and is formed in a round shape; having 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.

17. Housing and a plurality of secondary batteries vertically stacked within the housing; a cooling section provided on an inner bottom surface of the housing for cooling the plurality of secondary batteries; The secondary battery is an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators interposed therebetween; a pouch formed by sealing a pair of cases that are integrally connected by a folding portion and have a receiving portion in which the electrode assembly is received; The outer walls forming the periphery of the storage section include a folding portion side outer wall including the folding portion and adjacent to the cooling portion; a sealing part-side outer wall connected to a sealing part formed by fusing the pair of cases together; the ends of the negative electrodes protrude further toward the outer wall of the folding portion than the ends of the positive electrodes; a distance between an end of the negative electrode and an outer wall of the folding portion side is less than half a distance between an end of the negative electrode and an end of the positive electrode; The maximum distance between the ends of the negative electrodes and the outer wall of the folding portion is 0.8 mm or less; the folding portion forming a part of the folding portion side outer wall has a groove shape extending from one end of the folding portion side outer wall to the other end thereof and formed toward the electrode assembly accommodated in the accommodation portion, The storage section includes: A first edge that connects the top surface or the bottom surface of the storage section to the outer wall of the folding section and is formed in a round shape; A second edge that is rounded and connects the top or bottom surface of the storage portion to the outer wall of the sealing portion; a third edge that connects the folding portion side outer wall and the sealing portion side outer wall and is formed in a round shape; having 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.

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