Secondary battery and repair method thereof

Abstract

A repair method for a secondary battery according to an embodiment of the present invention for solving the above-mentioned problem includes: forming a crack on the outer surface of a battery case of a soft-pack type secondary battery; locally applying a metal solution to the crack; and forming a coating portion by drying the metal solution.

Description

Technical Field

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2020-0059394, filed on May 18, 2020, which is hereby incorporated by reference herein in its entirety. Technical Field

[0004] The present invention relates to a secondary battery and a repair method for the secondary battery, and more particularly, to a secondary battery and a repair method for the secondary battery, in which, when cracks are formed in the outer surface of a soft-pack type battery case, the cracks are repaired to minimize the penetration of moisture or gas from the outside through the cracks and to prevent electrolyte from leaking from the inside to the outside through the cracks. Background Art

[0005] Generally, secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. These secondary batteries are used in small products such as digital cameras, P-DVDs, MP3 players, mobile phones, PDAs, portable gaming devices, power tools, and electric bicycles, as well as large products requiring high power such as electric and hybrid vehicles, power storage devices for storing surplus electricity or renewable energy, and backup power storage devices.

[0006] Typically, to manufacture a lithium secondary battery, an electrode active material slurry is first applied to a positive electrode collector and a negative electrode collector to produce a positive electrode (cathode) and a negative electrode (anode). The electrodes are then stacked on both sides of a separator to form an electrode assembly. Furthermore, the electrode assembly is housed in a battery case, which is then sealed after an electrolyte is injected into the case.

[0007] Based on the material of the battery case that houses the electrode assembly, these secondary batteries are divided into soft-pack-type secondary batteries and can-type secondary batteries. In soft-pack-type secondary batteries, the electrode assembly is housed in a soft pack made of a flexible polymer material with a variable shape. In can-type secondary batteries, the electrode assembly is housed in a case made of a metal or plastic material with a predetermined shape.

[0008] A soft-pack battery case is manufactured by stretching a flexible soft-pack film to form a cup. This stretching is performed by inserting the soft-pack film into a punch press and applying pressure to the film with a punch to stretch it. Once the cup is formed, the electrode assembly is housed in the cup's accommodating space. The battery case is then folded to seal the seal, thereby producing a secondary battery.

[0009] This type of soft-pack battery case is made of a flexible material. It has the advantages of being easy to form and having excellent energy efficiency relative to its volume due to its thinness. On the other hand, due to its relatively low rigidity, the soft-pack battery case may be easily broken, for example, by a sharp object from the outside. This can cause moisture or gas to penetrate through the broken parts from the outside, or electrolyte to leak from the inside to the outside.

[0010] (Patent Document 1)

[0011] Japanese Patent Publication No. 2009-193729 Summary of the Invention

[0012] Technical issues

[0013] An object of the present invention to solve the above-mentioned problems is to provide a secondary battery and a repair method for the secondary battery, in which, when cracks are formed in the outer surface of a soft-pack type battery case, the cracks are repaired to minimize the penetration of moisture or gas from the outside through the cracks and to prevent the electrolyte from leaking from the inside to the outside through the cracks.

[0014] The objects of the present invention are not limited to the above objects, and those skilled in the art can clearly understand other objects not described herein through the following description.

[0015] Technical Solution

[0016] A secondary battery according to an embodiment of the present invention for solving the above-mentioned problem includes: an electrode assembly, which is formed by alternately stacking electrodes and separators; a soft-pack type battery case, which is configured to accommodate the electrode assembly in the soft-pack type battery case; and a coating portion, which contains metal particles and is formed to be locally coated on the outer surface of the battery case.

[0017] Furthermore, the coating portion may be formed to be coated to cracks formed in the outer surface of the battery case.

[0018] Additionally, cracks may form at edges or corners of the battery case.

[0019] Furthermore, the coating portion may contain aluminum.

[0020] Furthermore, the coating portion may include: a first coating portion containing a colored dye; and a second coating portion containing metal particles and formed on an outer surface of the first coating portion.

[0021] Furthermore, the first coating portion may be formed relatively widely, and the second coating portion may be formed relatively narrowly.

[0022] A repair method for a secondary battery according to an embodiment of the present invention for solving the above-mentioned problem includes: forming a crack in the outer surface of a battery case of a soft-pack type secondary battery; locally applying a metal solution to the crack; and drying the metal solution to form a coated portion.

[0023] In addition, in the step of forming the crack, the battery case may include: a surface protection layer made of a polymer and formed on the outermost layer; a sealant layer made of a polymer and formed on the innermost layer; and a gas barrier layer made of metal and stacked between the surface protection layer and the sealant layer.

[0024] Furthermore, in the step of forming cracks, cracks may be formed in the surface protection layer and the gas barrier layer.

[0025] Furthermore, the metal solution may contain aluminum.

[0026] Furthermore, in the step of applying the metal solution, the metal solution may be applied by at least one of spray coating, roll coating, dip coating, slide coating, spin coating, curtain coating, slot coating, or gravure coating.

[0027] Furthermore, in the step of applying the metal solution, the metal solution may be applied on the outer surface of the battery case by a spray coating method.

[0028] In addition, the method may further include the step of applying a colored solution to which a colored dye is added before the step of applying the metal solution.

[0029] Furthermore, in the step of forming the coating portion, the metal solution may be dried for 20 to 28 hours.

[0030] Details of other embodiments are included in the detailed description and accompanying drawings.

[0031] Beneficial effects

[0032] According to the embodiments of the present invention, there are at least the following effects.

[0033] The metal solution may be locally applied to cracks formed in the outer surface of the pouch-type battery case to repair the cracks.

[0034] In addition, the penetration of moisture or gas from the outside through the cracks can be minimized, and the electrolyte can be prevented from leaking from the inside to the outside through the cracks.

[0035] The effects of the present invention are not limited to the aforementioned description, and therefore, more varied effects are included in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a flowchart illustrating a method for repairing a secondary battery according to an embodiment of the present invention.

[0037] Figure 2 is an assembly diagram of a secondary battery according to an embodiment of the present invention.

[0038] Figure 3 is a perspective view of a secondary battery according to an embodiment of the present invention.

[0039] Figure 4 is a cross-sectional view of a soft package film forming a battery case according to an embodiment of the present invention.

[0040] Figure 5 is a diagram illustrating a state in which cracks are formed in the outer surface of a battery case according to an embodiment of the present invention.

[0041] Figure 6 is a diagram illustrating a state in which a metal solution is applied to a crack formed in an outer surface of a battery case to form a coating portion according to an embodiment of the present invention.

[0042] Figure 7 Graphs showing changes in the concentration of hydrogen fluoride (HF) in the secondary battery according to the manufacturing example and the secondary batteries according to Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0043] The advantages and features of the present invention and their implementation methods are illustrated by the following embodiments described in conjunction with the accompanying drawings. However, the present invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make this disclosure thorough and complete and to fully inform those skilled in the art of the scope of the invention. Furthermore, the present invention is limited only by the scope of the claims. Like reference numerals refer to like parts throughout.

[0044] Unless otherwise defined in the present invention, all terms used herein (including technical and scientific terms) have the same meaning as those generally understood by those skilled in the art. In addition, unless clearly and unambiguously defined in the specification, terms defined in commonly used dictionaries are not ideally or excessively interpreted as having formal meanings.

[0045] In the following description, technical terms are used only to illustrate specific exemplary embodiments and do not limit the present invention. In this specification, unless otherwise specified, terms in the singular may also include plural forms. The meaning of "include" and / or "comprising" does not exclude other components besides the components described.

[0046] Hereinafter, preferred embodiments will be described in detail with reference to the accompanying drawings.

[0047] Figure 1 is a flowchart illustrating a method for repairing a secondary battery 1 according to an embodiment of the present invention.

[0048] According to an embodiment of the present invention, the metal solution can be locally applied to the crack 2 formed in the outer surface of the soft pack type battery case 13 to repair the crack 2. In addition, the penetration of moisture or gas from the outside through the crack 2 can be minimized, and the electrolyte can be prevented from leaking from the inside to the outside through the crack 2.

[0049] To this end, the repair method of the secondary battery 1 according to an embodiment of the present invention includes: forming a crack 2 in the outer surface of the battery case 13 of the soft pack type secondary battery 1; locally applying a metal solution to the crack 2; and drying the metal solution to form a coating portion 15.

[0050] In addition, the secondary battery 1 repaired in this manner includes: an electrode assembly 10, which is formed by alternately stacking electrodes and separators; a soft-pack type battery case 13, which accommodates the electrode assembly 10 therein; and a coating portion 15, which is formed to be locally coated on the outer surface of the battery case 13.

[0051] Refer to below Figures 2 to 5 describe Figure 1 The contents of each step of the flowchart shown.

[0052] Figure 2 is an assembly diagram of a secondary battery 1 according to an embodiment of the present invention, Figure 3 is a perspective view of a secondary battery 1 according to an embodiment of the present invention.

[0053] like Figure 2 As shown, a soft-pack type secondary battery 1 according to an embodiment of the present invention includes: an electrode assembly 10, in which electrodes (such as positive electrodes and negative electrodes) and separators are alternately stacked; and a soft-pack type battery case 13, which accommodates the electrode assembly 10 therein.

[0054] To manufacture a soft-pack secondary battery 1, a slurry containing an electrode active material, a binder, and a plasticizer is first applied to a positive electrode collector and a negative electrode collector to manufacture electrodes, such as a positive electrode and a negative electrode. The electrodes are stacked on both sides of a separator to manufacture an electrode assembly 10 having a predetermined shape. The electrode assembly 10 is then inserted into a battery case 13, and the battery case 13 is sealed after an electrolyte is injected into the battery case 13.

[0055] In particular, the electrode assembly 10 may be a laminated structure comprising two types of electrodes (e.g., a positive electrode and a negative electrode) and a separator disposed between the electrodes to insulate the electrodes from each other or disposed on the left or right side of one electrode. The laminated structure may have various shapes without being restricted by shape. For example, a cathode and an anode, each having a predetermined standard, may be laminated with a separator disposed therebetween, or the laminated structure may be wound in the form of a jelly roll. Each of the two types of electrodes, i.e., the positive electrode and the negative electrode, has a structure in which an active material slurry is applied to an electrode current collector having a metal foil or a metal mesh. The slurry may typically be formed by stirring a granular active material, an auxiliary conductor, a binder, and a plasticizer in the presence of a solvent. The solvent may be removed in a subsequent process.

[0056] like Figure 2 As shown, the electrode assembly 10 includes an electrode terminal tab 11. The electrode terminal tabs 11 are respectively connected to the positive electrode and the negative electrode of the electrode assembly 10 and protrude to the outside of the electrode assembly 10, thereby providing a path for electron movement between the inside and the outside of the electrode assembly 10. The electrode collector of the electrode assembly 10 is composed of a portion coated with an electrode active material and an end (i.e., an uncoated portion) that is not coated with the electrode active material. In addition, each electrode terminal tab 11 can be formed by cutting the uncoated portion or by connecting a separate conductive member to the uncoated portion using ultrasonic welding. As shown Figure 2 As shown, the electrode tabs 11 may protrude in the same direction from one side of the electrode assembly 10, but the present invention is not limited thereto. For example, the electrode tabs 11 may protrude in different directions from each other.

[0057] In the electrode assembly 10, the electrode lead 12 that supplies power to the outside of the secondary battery 1 is connected to the electrode tab 11 by spot welding. In addition, a portion of the electrode lead 12 is surrounded by an insulating portion 14. The insulating portion 14 can be configured to be confined within the sealing portion 134, and the upper shell 131 and the lower shell 132 of the battery case 13 are heat-welded at the sealing portion 134 so that the electrode lead 12 is joined to the battery case 13. In addition, the electricity generated from the electrode assembly 10 can be prevented from flowing to the battery case 13 through the electrode lead 12, and the sealing of the battery case 13 can be maintained. Therefore, the insulating portion 14 can be made of a non-conductor with non-conductivity, which is non-conductive. Generally, an insulating tape that is easy to adhere to the electrode lead 12 and has a thin thickness is mainly used as the insulating portion 14, but the present invention is not limited thereto. For example, various components can be used as the insulating portion 14 as long as the component can insulate the electrode lead 12.

[0058] The electrode lead 12 includes a positive electrode lead 121 and a negative electrode lead 122. One end of the positive electrode lead 121 is connected to the positive electrode tab 111 to extend in the direction in which the positive electrode tab 111 protrudes. One end of the negative electrode lead 122 is connected to the negative electrode tab 112 to extend in the direction in which the negative electrode tab 112 protrudes. Figure 2 As shown, the other ends of the positive electrode lead 121 and the negative electrode lead 122 all protrude to the outside of the battery case 13. Therefore, the electricity generated in the electrode assembly 10 can be supplied to the outside. In addition, since each of the positive electrode tab 111 and the negative electrode tab 112 is formed to protrude in various directions, each of the positive electrode lead 121 and the negative electrode lead 122 can extend in various directions.

[0059] The positive electrode lead 121 and the negative electrode lead 122 can be made of different materials. That is, the positive electrode lead 121 can be made of the same material as the positive electrode current collector, namely, aluminum (Al), while the negative electrode lead 122 can be made of the same material as the negative electrode current collector, namely, copper (Cu) or copper coated with nickel (Ni). In addition, the portion of the electrode lead 12 that protrudes outside the battery case 13 can be provided as a terminal portion and electrically connected to an external terminal.

[0060] The battery case 13 is a soft pack made of a flexible material, in which the electrode assembly 10 is housed. The case where the battery case 13 is a soft pack will be described below. When a flexible soft pack film 135 is stretch-formed using a punch or the like, a portion of the soft pack film 135 is stretched to form a cup portion 133 including a soft pack-shaped housing space 1331, thereby manufacturing the battery case 13. The battery case 13 houses the electrode assembly 10 so that a portion of the electrode lead 12, i.e., the terminal portion, is exposed and then sealed. Figure 2As shown, the battery case 13 includes an upper case 131 and a lower case 132. A receiving space 1331 may be provided in the lower case 132, a cup portion 133 may be formed in the receiving space 1331 to receive the electrode assembly 10, and the upper case 131 may cover the upper side of the receiving space 1331 so that the electrode assembly 10 is not separated from the outside of the battery case 13. In addition, the sealing portion 134 is sealed to seal the receiving space 1331. Here, the cup portion 133 having the receiving portion 1331 may be formed in the upper case 131 to receive the electrode assembly in the upper portion 10. As shown in FIG. Figure 2 As shown, one side of the upper housing 131 and one side of the lower housing 132 may be connected to each other. However, the present invention is not limited thereto. For example, the upper housing 131 and the lower housing 132 may be manufactured separately to be separated from each other.

[0061] When the electrode lead 12 is connected to the electrode tab 11 of the electrode assembly 10 and the insulating portion 14 is provided on a portion of the electrode lead 12, the electrode assembly 10 can be accommodated in the accommodation space 1331 provided in the cup portion 133 of the lower case 132, and the upper case 131 can cover the accommodation space from the upper side. In addition, the electrolyte is injected, and then, as shown in FIG. Figure 3 As shown, a sealing portion 134 extending outward from the edges of the upper case 131 and the lower case 132 is sealed. The electrolyte can move lithium ions generated by the electrochemical reaction of the electrodes during charging and discharging of the secondary battery 1. The electrolyte can include a non-aqueous organic electrolyte that is a mixture of a lithium salt and a high-purity organic solvent or a polymer using a polymer electrolyte. Figure 3 As shown, the pouch-type secondary battery 1 can be manufactured by the above-described method.

[0062] Figure 4 is a cross-sectional view of a soft coating film 135 forming a battery case 13 according to an embodiment of the present invention.

[0063] The soft coating film 135 can be stretched to form the battery case 13. That is, the soft coating film 135 is stretched to form the cup portion 133, thereby manufacturing the battery case 13. Figure 3 As shown, the soft envelope 135 includes a gas barrier layer 1351 , a surface protection layer 1352 , and a sealant layer 1353 .

[0064] The gas barrier layer 1351 can ensure the mechanical strength of the battery case 13, prevent moisture or gas from being introduced into and discharged from the outside of the secondary battery 1, and prevent leakage of the electrolyte. Generally, the gas barrier layer 1351 contains metal. In particular, aluminum (Al) foil is mainly used for the gas barrier layer 2351. Aluminum can ensure mechanical strength of a predetermined level or higher, but is lightweight. Therefore, aluminum can ensure the replenishment of electrochemical performance and heat dissipation due to the electrode assembly 10 and the electrolyte. However, the present invention is not limited to this. For example, the gas barrier layer 1351 can be made of various materials. For example, the gas barrier layer 1351 can be made of a material or a mixture of two or more materials selected from the group consisting of Fe, C, Cr, Mn, Ni and Al. When the gas barrier layer 1351 is made of a material containing iron, the mechanical strength can be improved. When the gas barrier layer 1351 is made of a material containing aluminum, the flexibility can be improved. Therefore, considering the characteristics of the gas barrier layer 1351, the material forming the gas barrier layer 1351 can be used.

[0065] The surface protection layer 1352 is made of a polymer and is arranged on the outermost layer to protect the secondary battery 1 from external friction and collision and also to electrically insulate the electrode assembly 10 from the outside. Here, the outermost layer represents the direction opposite to the direction in which the electrode assembly 10 is set relative to the gas barrier layer 1351, that is, the outward direction. The surface protection layer 1352 can be made of at least 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, polyparaphenylenebenzobisoxazole (polyparaphenylenebenzobisoxazole), polyarylate, polytetrafluoroethylene and glass fiber. In particular, a polymer mainly having wear resistance and heat resistance is used, such as nylon resin or polyethylene terephthalate (PET). In addition, the surface protection layer 1352 can have a single-layer structure made of one material or a composite layer structure in which two or more materials are formed into layers.

[0066] The sealant layer 1353 is made of a polymer and is provided in the innermost layer to directly contact the electrode assembly 10. The soft-pack type battery case 13 can be manufactured by stretching the soft-pack film 135 having the laminated structure described above using a punch or the like, while a portion thereof is elongated to form a cup portion 133 including a bag-shaped accommodation space 1331. In addition, when the electrode assembly 10 is accommodated in the accommodation space 1331, the electrolyte is injected. Thereafter, when the upper case 131 and the lower case 132 can be brought into contact with each other and thermal compression is applied to the sealing portion 134, the sealant layer 1353 can be bonded to each other to seal the battery case 13. Here, since the sealant layer 1353 is in direct contact with the electrode assembly 10, the sealant layer 1353 must have insulating properties. In addition, since the sealant layer 1353 is in contact with the electrolyte, the sealant layer 1353 must have corrosion resistance. In addition, since the interior of the battery housing 13 is completely sealed to prevent material from moving between the interior and exterior of the battery housing 13, high sealing performance must be achieved. That is, the sealing portion 134 to which the sealant layer 1353 is bonded should have excellent bonding strength. Typically, the sealant layer 1353 can be made of at least 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, polybenzobisoxazole, polyarylate, polytetrafluoroethylene, and glass fiber. In particular, polyolefin resins such as polypropylene (PP) and polyethylene (PE) are used for the sealant layer 1353. Polypropylene (PP) excels in mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, as well as chemical properties such as corrosion resistance, and is therefore primarily used to manufacture the sealant layer 1353. In addition, the sealant layer 1353 can be made of cationic polypropylene or a polypropylene-butylene-ethylene terpolymer. In addition, the sealant layer 1353 may have a single layer structure made of one material or a composite layer structure in which two or more materials are respectively formed as layers.

[0067] Figure 5 1 is a diagram showing a state in which a crack 2 is formed in the outer surface of the battery case 13 according to the embodiment of the present invention.

[0068] As described above, in the soft-pack type secondary battery 1, the soft-pack type battery case 13 has high flexibility but low rigidity. Therefore, when the soft-pack film is molded to form the cup portion or the sealing portion is sealed, a sharp object from the outside may easily cause damage such as the formation of cracks 2 in the outer surface (S101). Generally, cracks 2 are often formed when the soft-pack film 135 is molded or the sealing portion is sealed. Therefore, cracks 2 are often formed at the edges or corners of the battery case 13. Figure 5As shown, cracks 2 may be formed not only in surface protection layer 1352 but also in gas barrier layer 1351. Gas barrier layer 1351 can block the introduction and discharge of external moisture or gas. When cracks 2 are formed in gas barrier layer 1351, moisture or gas may leak to the outside through the portion where cracks 2 are formed or penetrate from the outside.

[0069] Figure 6 1 is a diagram showing a state in which a metal solution is applied to the crack 2 formed in the outer surface of the battery case 13 to form the coating portion 15 according to the embodiment of the present invention.

[0070] According to an embodiment of the present invention, a metal solution is locally applied to the crack 2 formed in the outer surface of the battery case 13 of the pouch type ( S102 ).

[0071] The metal solution may be a solution containing fine metal particles and has a certain degree of viscosity, and when applied to the outer surface of the battery case 13, it can maintain a bonded state. The metal particles contained in the metal solution may be one material or a mixture of two or more materials selected from the group consisting of iron (Fe), carbon (C), chromium (Cr), manganese (Mn), nickel (Ni), and aluminum (Al), and specifically preferably contain aluminum. That is, the metal solution may be an aluminum (Al) paint containing aluminum powder.

[0072] The metal solution can be applied by at least one of spraying, roller coating, dip coating, ramp coating, spin coating, curtain coating, slit coating, or gravure coating. That is, the present invention is not limited thereto, and various coating methods can be used. In particular, in order to apply the metal solution only locally to the crack 2 formed in the outer surface of the battery case 13, a spray coating method is preferably used. Specifically, adhesive tape can be applied to the peripheral area of ​​the crack 2 for masking, and the metal solution can be applied using a spray coating method. Thereafter, the adhesive tape can be removed to complete the application of the metal solution.

[0073] According to another embodiment of the present invention, before applying the metal solution, a colored solution to which a colored dye is added may be applied first. If the colored solution containing the colored dye is applied to the crack, the crack can be more clearly identified with the naked eye, so it is easy to determine whether the metal solution is applied and the location where the metal solution is applied. As described above, generally, cracks 2 are often formed at the edges or corners of the battery case 13 when the soft-coat film 135 is formed or the sealing portion is sealed. Therefore, after the soft-coat film 135 is formed or the sealing portion is sealed, a colored solution may be applied to the edges or corners of the battery case 13. These colored dyes may have various colors, but in the case of primary colors such as red or blue or dark colors such as black, the cracks can be more clearly identified, which is preferred.

[0074] After the metal solution is applied, the metal solution is dried. Figure 6 As shown, a coating portion 15 is formed that is locally coated on the crack 2 formed in the outer surface of the battery case 13 (S103). According to another embodiment of the present invention, since the colored solution is applied before the metal solution is applied, the coating portion 15 includes a first coating portion (not shown) and a second coating portion (not shown). In addition, since the first coating portion is formed by applying the colored solution, the first coating portion contains the colored solution. The first coating portion is formed on the crack 2 before the second coating portion is formed, and since the second coating portion is formed by applying the metal solution, the second coating portion contains metal particles and is formed on the outer surface of the first coating portion. Since the first coating portion is applied to check whether the crack 2 occurs and the position of the crack 2, the first coating portion can be formed relatively widely, and since the second coating portion is applied to repair the crack 2, the second coating portion can be formed relatively narrowly.

[0075] As mentioned above, Figure 6 As shown, since the metal solution is only partially applied to the crack 2 formed in the outer surface of the battery case 13, the coating portion 15 can also be partially applied to the outer surface of the battery case 13. As described above, since the metal solution contains metal particles, the coating portion 15 can also contain metal particles, and in particular, it can preferably contain aluminum. In addition, when drying the metal solution, it is preferably dried for 20 to 28 hours. The soft-pack type secondary battery 1 with the crack 2 can be repaired by the above method.

[0076] Manufacturing Example

[0077] A soft-coated film was prepared in which the thickness of the surface protective layer manufactured by laminating PET having a thickness of 12 μm and nylon having a thickness of 15 μm was 27 μm, the thickness of the gas barrier layer made of aluminum was 40 μm, and the thickness of the sealant layer made of polypropylene was 80 μm. The soft-coated film was stretch-formed to manufacture a battery case, and then the electrode assembly and the electrolyte were contained in the battery case for sealing. Here, the concentration of hydrogen fluoride (HF) in the electrolyte was 105.4 ppm. Thus, a soft-packed secondary battery with a width of 133 mm and a length of 125 mm was manufactured.

[0078] A crack with a length of 1 cm and a depth of 73 μm was formed in the pouch-type secondary battery manufactured as described above using a cutting knife. Furthermore, an aluminum paint containing 10% to 20% aluminum powder was sprayed onto the crack. The pouch-type secondary battery was then dried for 24 hours for repair.

[0079] Comparative Example 1

[0080] It was manufactured in the same manner as in Manufacturing Example, except that the instant glue was applied to the formed cracks.

[0081] Comparative Example 2

[0082] It was manufactured in the same manner as in the manufacturing example, except that no cracks were formed and no aluminum paint was applied.

[0083] Methods for measuring physical properties - changes in HF concentration

[0084] Samples of the soft-pack type secondary batteries manufactured according to the manufacturing example, comparative example 1, and comparative example 2 were stored at a temperature of 60° and a humidity of 90%. In addition, after one week, each sample was disassembled to extract the electrolyte. Then, 1 ml of each electrolyte was placed in an acid-base measuring device (manufacturer: Metrohm, model: 848Titrino plus), and the change in the concentration of hydrogen fluoride (HF) contained in the electrolyte was measured.

[0085] Results of measuring physical properties - changes in HF concentration

[0086] [Table 1]

[0087] Final HF concentration (ppm) HF concentration increase (ppm) Manufacturing Example 350.0 244.6 Comparative Example 1 775.0 669.6 Comparative Example 2 295.8 190.4

[0088] Figure 7 This graph shows the final concentration of hydrogen fluoride (HF) in the secondary battery according to the manufacturing example and the secondary batteries according to Comparative Examples 1 and 2. Generally, since the electrolyte contains a large amount of fluorine (F), the electrolyte combines with moisture to generate hydrogen fluoride (HF). Therefore, the degree of moisture penetration can be determined by the increase in the amount of hydrogen fluoride (HF) in the electrolyte.

[0089] like Figure 7 As shown in Table 1, in the secondary battery according to Comparative Example 2, the hydrogen fluoride (HF) concentration in the internal electrolyte was measured to be 295.8 ppm, thus obtaining an increase of 190.4 ppm. Although the secondary battery according to Comparative Example 2 is a secondary battery in which no cracks are formed, the concentration of hydrogen fluoride (HF) has increased. That is, even in ordinary secondary batteries, it has been confirmed that the concentration of hydrogen fluoride (HF) naturally increases under a high temperature and high humidity environment.

[0090] However, in the secondary battery of the manufacturing example according to the present invention, the concentration of hydrogen fluoride (HF) was measured to be 350.0 ppm, and an increase of 244.6 ppm was obtained. That is, compared with the ordinary secondary battery, the concentration of hydrogen fluoride (HF) in the secondary battery in which the cracks were repaired using the aluminum coating did not increase significantly.

[0091] On the other hand, the concentration of hydrogen fluoride (HF) was measured to be 775.0 ppm in the secondary battery according to Comparative Example 1, which showed an increase of 669.6 ppm. That is, the concentration of hydrogen fluoride (HF) was significantly increased in the secondary battery in which cracks were repaired using a general polymer adhesive such as instant glue, compared to the ordinary secondary battery.

[0092] Therefore, when a general polymer adhesive is used to repair cracks, moisture or gas can easily penetrate from the outside through the cracks. However, it can be seen that when aluminum paint is used to repair cracks, the penetration of moisture or gas from the outside through the cracks can be minimized.

[0093] Those skilled in the art will appreciate that the present invention may be implemented in other specific forms without changing the technical concept or essential features. Therefore, the embodiments disclosed above are considered to be illustrative rather than restrictive. Therefore, the scope of the present invention is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein. Various modifications within the equivalent meanings of the claims of the present invention and within the scope of the claims should be considered to be within the scope of the present invention.

[0094] [Explanation of Reference Signs]

[0095] 1: Secondary battery 2: Crack

[0096] 10: Electrode assembly 11: Electrode terminal

[0097] 12: Electrode lead 13: Battery case

[0098] 14: Insulation part 15: Coating part

[0099] 111: Positive terminal lug 112: Negative terminal lug

[0100] 121: Positive lead 122: Negative lead

[0101] 131: Upper shell 132: Lower shell

[0102] 133: Cup part 134: Sealing part

[0103] 135: Soft film 1331: Accommodation space

[0104] 1351: Gas barrier layer 1352: Surface protection layer

[0105] 1353: Sealant layer

Claims

1. A secondary battery comprising: an electrode assembly formed by alternately stacking electrodes and separators; a soft-pack type battery case configured to accommodate the electrode assembly therein; as well as a coating portion containing metal particles and formed to be partially coated on the outer surface of the battery case, Wherein, the coating unit includes: a first coating section comprising a colored dye; and a second coating portion containing metal particles and formed on an outer surface of the first coating portion, wherein the first coating portion is formed broadly and the second coating portion is formed narrowly. Wherein, the battery housing comprises: a surface protection layer made of a polymer and formed on the outermost layer; a sealant layer made of a polymer and formed as an innermost layer; and a gas barrier layer made of metal and laminated between the surface protection layer and the sealant layer, wherein the coating portion contains aluminum to repair cracks in the gas barrier layer and the surface protection layer of the battery housing composed of aluminum foil, Here, the coating portion is formed to be coated to a crack formed in the outer surface of the battery case.

2. The secondary battery according to claim 1, wherein The cracks are formed at edges or corners of the battery case.

3. A method for repairing a secondary battery, the method comprising: forming a crack in an outer surface of a battery case of a pouch-type secondary battery; The step of locally applying a metal solution to the crack; as well as a step of drying the metal solution to form a coating portion, Wherein, in the step of forming the crack, the battery housing includes: a surface protection layer made of a polymer and formed on the outermost layer; a sealant layer made of a polymer and formed as an innermost layer; and a gas barrier layer made of metal and laminated between the surface protection layer and the sealant layer, wherein, in the step of forming the cracks, the cracks are formed in the surface protection layer and the gas barrier layer; wherein the metal solution contains aluminum, The method further includes the step of broadly applying a colored solution to which a colored dye is added before the step of narrowly applying the metal solution.

4. The method for repairing a secondary battery according to claim 3, wherein: In the step of applying the metal solution, the metal solution is applied by at least one of spray coating, roll coating, dip coating, slant coating, spin coating, flow coating, slit coating, or gravure coating.

5. The method for repairing a secondary battery according to claim 4, wherein: In the step of applying the metal solution, the metal solution is applied on the outer surface of the battery case by spraying.

6. The method for repairing a secondary battery according to claim 3, wherein: In the step of forming the coating portion, the metal solution is dried for 20 to 28 hours.

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