Secondary battery with vent formed on insulating film and manufacturing method thereof

Abstract

According to this embodiment, a secondary battery is provided in which an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes is housed in a battery case together with an electrolyte, the positive electrode includes a positive electrode tab, the negative electrode includes a negative electrode tab, the positive electrode tab is electrically connected to a positive electrode lead, and the negative electrode tab is electrically connected to a negative electrode lead, the positive electrode lead and the negative electrode lead are exposed to the outside through a sealed portion of the battery case, a positive electrode insulating film and a negative electrode insulating film are attached to portions of the positive electrode lead and the negative electrode lead that contact the sealed portion of the battery case, respectively, and at least one of the positive electrode insulating film and the negative electrode insulating film has a vent portion that is surface-treated with a non-adhesive material between the positive electrode lead or the negative electrode lead and the insulating film at a portion attached to the positive electrode lead or the negative electrode lead.

Description

[Technical field]

[0001] The present invention relates to a secondary battery having a vent portion formed on an insulating film, and a method for manufacturing the same.

[0002] This application claims priority to Korean Patent Application No. 10-2021-0011775, filed on January 27, 2021, the entire contents of which are incorporated herein by reference in their entirety in the specification and drawings. [Background technology]

[0003] As the use of fossil fuels increases sharply, there is an increasing demand for alternative and clean energy. As part of this, the field in which research is most active is the field of electrochemical power generation and storage.

[0004] At present, a representative example of an electrochemical element that uses such electrochemical energy is a secondary battery, and the range of its use is expanding more and more.

[0005] Recently, with the increasing technological development and demand for portable devices such as portable computers, mobile phones, and cameras, the demand for secondary batteries as energy sources is rapidly increasing. Among such secondary batteries, various researches have been conducted on lithium secondary batteries, which have excellent charge / discharge characteristics and life characteristics and are environmentally friendly, and they have been commercialized and are widely used.

[0006] However, as the range of use of lithium secondary batteries expands, there is a demand for increased energy density. In response to this demand, the amount of gas generated inside the secondary battery increases as the energy density of the secondary battery increases.

[0007] Furthermore, when moisture penetrates into the secondary battery, side reactions occur, which causes the performance of the secondary battery to deteriorate and gas generation to be further accelerated.

[0008] To address this issue, safety issues have been addressed by forming vents in secondary batteries to allow gas generated inside the battery to be released to the outside. However, when a secondary battery is vented, its lifespan is significantly shortened, so there is a need to develop technology that can resolve this issue. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to solve the above-mentioned problems of the conventional technology and the technical problems that have been desired in the past.

[0010] Specifically, the present invention provides a secondary battery and a manufacturing method thereof that efficiently structures a gas exhaust passage in a simpler manner, efficiently exhausts gas to the outside, and minimizes moisture diffusing from the outside, thereby improving the safety of the secondary battery. [Means for solving the problem]

[0011] In order to achieve the above object, a secondary battery according to one embodiment of the present invention comprises: an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, is housed in a battery case together with an electrolyte; the positive electrode includes a positive electrode tab and the negative electrode includes a negative electrode tab; the positive electrode tab is electrically connected to a positive electrode lead, the negative electrode tab is electrically connected to a negative electrode lead, and the positive electrode lead and the negative electrode lead are exposed to the outside through a sealing portion of the battery case; a positive electrode insulating film and a negative electrode insulating film are attached to the positive electrode lead and the negative electrode lead at portions where the positive electrode lead and the negative electrode lead contact with a sealing portion of the battery case, respectively; At least one of the positive insulating film and the negative insulating film has a vent portion that is surface-treated with a non-adhesive material between the positive electrode lead or the negative electrode lead at a portion where the insulating film is attached to the positive electrode lead or the negative electrode lead.

[0012] Here, the vent portion may be a coating layer formed by transferring an unbonded material from a roll onto the insulating film by rolling.

[0013] The non-adhesive material may be a polymer having a melting point of 220° C. or more, or a material obtained by coating gelled ceramic particles and then curing the same. Preferably, the non-adhesive material may be one or more polymers selected from the group consisting of polyimide-based materials, polytetrafluoroethylene, and polymethylpentene, or one or more ceramic particles selected from the group consisting of SiO2, TiO2, ZnO, CaO, and BaO in a gelled state and then cured.

[0014] The vent portion may have a planar shape of a circle, an ellipse, or a polygon.

[0015] Meanwhile, at least one of the positive electrode lead and the negative electrode lead may include a metal substrate and a coating layer formed on a surface of the metal substrate.

[0016] In addition, the method for manufacturing the secondary battery according to another embodiment of the present invention includes: (a) preparing at least one positive electrode and at least one negative electrode each having a structure in which an electrode active material layer is formed on a current collector having a tab formed on at least one side thereof; (b) interposing a separator between the positive electrode and the negative electrode; (c) forming a vent portion by transferring the unbonded material to at least one of the positive electrode insulating film and the negative electrode insulating film by a roll rolling method using a roll containing the unbonded material corresponding to the shape of the vent portion; (d) electrically connecting a positive electrode lead to a positive electrode tab, electrically connecting a negative electrode lead to the negative electrode tab, and attaching a positive electrode insulating film and a negative electrode insulating film onto the positive electrode lead and the negative electrode lead, respectively; The vent may be disposed between the positive electrode lead and an attachment portion of the positive electrode insulating film, between the negative electrode lead and an attachment portion of the negative electrode insulating film, or both.

[0017] Here, the non-adhesive material may be a polymer having a melting point of 220° C. or more, or a material obtained by coating gelled ceramic particles and then curing the coated material, preferably one or more polymers selected from the group consisting of polyimide-based materials, polytetrafluoroethylene, and polymethylpentene, or one or more ceramic particles selected from the group consisting of SiO2, TiO2, ZnO, CaO, and BaO in a gelled state and then curing the coated material.

[0018] Alternatively, the vent portion may have a planar shape that is circular, elliptical, or polygonal. Effect of the Invention

[0019] As described above, according to one embodiment of the present invention, a vent portion is formed on an insulating film attached to an electrode lead, so that a gas exhaust path can be formed in the lead portion, thereby increasing the effectiveness.

[0020] In addition, the vent portion can be formed very quickly and efficiently by a simplified method of coating a non-adhesive material on the insulating film that is to be adhered to the electrode lead by a roll-rolling method. [Brief description of the drawings]

[0021] [Figure 1] 4 is a schematic diagram showing the shape of a vent portion formed on an insulating film according to an embodiment of the present invention; FIG. [Diagram 2] FIG. 2 is a schematic diagram of a secondary battery according to another embodiment of the present invention. [Diagram 3] 5A to 5C are schematic diagrams illustrating a method of forming a vent portion according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0023] 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 corresponds to the technical concept of the present invention, based on the principle that the inventor himself can appropriately define the concept of the term in order to best describe the invention.

[0024] The terms used in this specification are merely used to describe exemplary embodiments and do not limit the present invention. A singular expression includes a plural expression unless a different meaning is clearly indicated in the context.

[0025] Additionally, in this specification, terms such as "comprise," "include," "comprise," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not exclude the possible presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0026] According to one embodiment of the present invention, an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, is housed in a battery case together with an electrolyte; the positive electrode includes a positive electrode tab and the negative electrode includes a negative electrode tab; the positive electrode tab is electrically connected to a positive electrode lead, the negative electrode tab is electrically connected to a negative electrode lead, and the positive electrode lead and the negative electrode lead are exposed to the outside through a sealing portion of the battery case; a positive electrode insulating film and a negative electrode insulating film are attached to the positive electrode lead and the negative electrode lead at portions where the positive electrode lead and the negative electrode lead contact with a sealing portion of the battery case, respectively; At least one of the positive insulating film and the negative insulating film has a vent portion that is surface-treated with a non-adhesive material between the positive electrode lead or the negative electrode lead at a portion where the positive electrode lead or the negative electrode lead is attached.

[0027] Conventionally, various methods have been developed for forming a vent portion for discharging gas generated inside a secondary battery to the outside, such as forming a notch in a pouch or forming a separate gas discharging member between leads, thereby discharging the gas generated inside the secondary battery to the outside and ensuring the safety of the secondary battery.

[0028] However, this method has been difficult to gain an advantage in terms of process efficiency and cost competitiveness because the secondary battery cannot be used any more upon venting, the lifespan of the secondary battery is significantly reduced, or additional materials are required.

[0029] In contrast, the present invention provides a method for forming a vent portion in an electrode lead portion using a simpler method, thereby ensuring the safety of the secondary battery and significantly improving its lifespan.

[0030] In particular, the vent can be formed by a very simple and inexpensive process.

[0031] For example, the vent portion may be formed by using various conventional coating methods without limitation, such as spin coating, blade coating, spray coating, and inkjet printing. Preferably, the coating layer may be formed by transferring the unbonded material from a roll onto the insulating film by rolling.

[0032] Such a vent portion can be formed very simply by forming a coating layer of a non-adhesive material on the insulating film to be attached to the lead, and then attaching the insulating film to the lead so that it is interposed between the lead and the insulating film, which is very efficient in terms of process and economy.

[0033] In this case, the non-adhesive material means a material that does not adhere to the positive electrode lead or the negative electrode lead, and may be, for example, a polymer having a melting point of 220° C. or more, or a material obtained by coating gelled ceramic particles and then curing the polymer. Preferably, the non-adhesive material may be one or more polymers selected from the group consisting of polyimide-based materials, polytetrafluoroethylene, and polymethylpentene, or one or more ceramic particles selected from the group consisting of SiO2, TiO2, ZnO, CaO, and BaO in a gelled state and then cured.

[0034] In this case, the coating thickness of the non-adhesive material may be formed to be 30 nm to 1 mm.

[0035] When the coating thickness of the unbonded material satisfies the above range, it is possible to have a process advantage and to prevent the problem of the portion other than the unbonded material not being sealed, thereby more easily preventing the leakage of electrolyte.

[0036] In this case, the vent portion may be formed in an area of ​​10% to 70%, and more particularly, 20% to 50%, of the entire area where the positive electrode lead and the positive electrode insulating film, or the negative electrode lead and the negative electrode insulating film, are attached.

[0037] When the area of ​​the vent portion satisfies the above range, the vent effect can be ensured and problems with sealing, such as leakage of electrolyte, can be more easily prevented.

[0038] Meanwhile, the planar shape of the vent portion is not limited, and may be formed in various shapes such as a circle, an ellipse, or a polygon, and may be formed in a pattern that can efficiently exhaust gas without causing problems such as electrolyte leakage.

[0039] FIG. 1 shows schematic examples of the shape of a vent portion 101 on an insulating film 100. In FIG.

[0040] Referring to FIG. 1, FIG. 1(a) shows a rectangular vent portion 101, FIG. 1(b) shows an elliptical vent portion 101, FIG. 1(c) shows a polygonal vent portion 101 like a concave-convex shape, and FIG. 1(d) shows a triangular vent portion 101.

[0041] However, the drawings are merely examples and the present invention is not limited to these shapes.

[0042] FIG. 2 shows a schematic diagram of a secondary battery 200 according to an embodiment of the present invention.

[0043] Referring to FIG. 2, an electrode assembly 201 including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode is incorporated in a battery case 202 together with an electrolyte, the positive electrode includes a positive electrode tab 203, the negative electrode includes a negative electrode tab 204, the positive electrode tab 203 is electrically connected to a positive electrode lead 205, and the negative electrode tab 204 is electrically connected to a negative electrode lead 206, the positive electrode lead 205 and the negative electrode lead 206 are exposed to the outside through a sealed part of the battery case 202, and a positive electrode insulating film 110 and a negative electrode insulating film 100 are attached to the portions where the positive electrode lead 205 and the negative electrode lead 206 contact the sealed part of the battery case 202, respectively.

[0044] In this case, when examining the structure by enlarging (A) the area where the negative electrode insulating film 100 is attached onto the negative electrode lead 206, it can be seen that a vent portion 101 is formed in a part of the area where the negative electrode insulating film 100 is attached onto the negative electrode lead 206.

[0045] In this case, the vent portion 101 is located between the negative electrode insulating film 100 and the negative electrode lead 206, and serves as a gas discharge passage by not being bonded to the negative electrode lead 206.

[0046] Although not shown, a vent portion may be formed in the positive electrode insulating film 110, or both the positive electrode insulating film 110 and the negative electrode insulating film 100 may have a vent portion formed therein.

[0047] Meanwhile, the vent portion 101 may be formed to occupy 20% to 90% of the contact area between the negative electrode lead 206 and the negative electrode insulating film 100, more specifically, 30% to 80% of the contact area.

[0048] When the area of ​​vent portion 101 satisfies the above range, the vent effect can be ensured, and the adhesion area between the lead and the insulating film can be sufficiently ensured, so that the sealing performance can be more easily ensured.

[0049] The shape of the vent is also the same as that described above.

[0050] The material of the positive electrode insulating film 110 and the negative electrode insulating film 100 may be any one of thermoplastic, thermosetting, and photosetting resins having electrical insulation properties, such as polyolefin resin, styrene-butadiene resin, styrene resin, epoxy resin, urethane resin, acrylic resin, phenol resin, amide resin, acrylate resin, and modified resins thereof, but is not particularly limited as long as the resin can perform the above-mentioned functions.

[0051] Other specific details of the insulating film include those that are conventionally known.

[0052] Meanwhile, at least one of the positive electrode lead 205 and the negative electrode lead 206 may be made of a metal substrate and may include the metal substrate and a coating layer formed on the surface of the metal substrate.

[0053] In this case, the metal substrate may include at least one selected from the group consisting of nickel (Ni), aluminum (Al), copper (Cu) and stainless steel. More specifically, the preferred material of the metal substrate may differ depending on whether the electrode lead is a positive electrode lead or a negative electrode lead. For example, the positive electrode lead may be aluminum, nickel or an alloy containing at least one of these, and the negative electrode lead may be copper, nickel or an alloy containing at least one of these.

[0054] Meanwhile, the coating layer is intended to prevent corrosion of the electrode lead due to strong acid generated when moisture penetrates into the secondary battery and reacts with the electrolyte, and to improve the adhesive strength between the electrode lead and the insulating film, and may contain, for example, a metal or metal oxide. More specifically, the coating layer may contain one or more selected from the group consisting of chromium (Cr), nickel (Ni), iron (Fe), molybdenum (Mo), silicon (Si), titanium (Ti), columbium (Cb), silicon oxide, tin oxide, and titanium oxide.

[0055] In this case, the thickness of the coating layer may be 100 μm or less, preferably 30 μm to 100 μm, more preferably 30 μm to 80 μm, and most preferably 30 μm to 70 μm.

[0056] When this range is satisfied, corrosion of the positive electrode lead and the negative electrode lead due to strong acid generated inside the secondary battery can be more easily prevented, and the thickness of the leads can be easily prevented from becoming too thick.

[0057] The coating layer can be formed by a method known in the art, and the method is not particularly limited. For example, the coating layer can be formed by electroplating.

[0058] The battery case is not limited to a specific one, and may be a pouch-type battery case in which the above-mentioned configuration is appropriately utilized.

[0059] The configurations of the other components, such as the positive electrode, negative electrode, separator, positive electrode tab, negative electrode tab, battery case, and electrolyte, are publicly known, and therefore detailed description thereof will be omitted in the present invention.

[0060] Meanwhile, according to yet another embodiment of the present invention, The method for producing the secondary battery includes the steps of: (a) preparing at least one positive electrode and at least one negative electrode each having a structure in which an electrode active material layer is formed on a current collector having a tab formed on at least one side thereof; (b) interposing a separator between the positive electrode and the negative electrode; (c) forming a vent portion by transferring the unbonded material to at least one of the positive electrode insulating film and the negative electrode insulating film by a roll rolling method using a roll containing the unbonded material corresponding to the shape of the vent portion; (d) electrically connecting a positive electrode lead to a positive electrode tab, electrically connecting a negative electrode lead to the negative electrode tab, and attaching a positive electrode insulating film and a negative electrode insulating film onto the positive electrode lead and the negative electrode lead, respectively; The vent portion is interposed between the positive electrode lead and an attachment portion of the positive electrode insulating film, between the negative electrode lead and an attachment portion of the negative electrode insulating film, or both.

[0061] Specifically, according to the present invention, the bent portion is formed by a rolling method.

[0062] Such a manufacturing method is shown simply in FIG.

[0063] Referring to FIG. 3, the vent portion 101 can be formed by using a roll 300 having a surface on which an unbonded material 111 corresponding to the shape of the vent portion 101 is formed, and then transferring and coating the unbonded material 111 onto the surface of the insulating film 100 by a rolling method.

[0064] In this case, the specific example of the unbonded material 111 is the same as that described above, and although the shape of the vent portion 101 is shown as a rectangle, the shape is not limited thereto, and the planar shape may be a circle, an ellipse, a polygon, or the like.

[0065] As described above, a person having ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above content. [Explanation of symbols]

[0066] 100 Negative electrode insulating film 101 Vent 110 Positive electrode insulating film 111 Unbonded substances 200 Secondary battery 201 Electrode assembly 202 Battery case 203 Positive electrode tab 204 Negative electrode tab 205 Positive lead 206 Negative lead 300 rolls

Claims

1. an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, is housed in a battery case together with an electrolyte; the positive electrode includes a positive electrode tab and the negative electrode includes a negative electrode tab; the positive electrode tab is electrically connected to a positive electrode lead, the negative electrode tab is electrically connected to a negative electrode lead, and the positive electrode lead and the negative electrode lead are exposed to the outside through a sealing portion of the battery case; a positive electrode insulating film and a negative electrode insulating film are attached to the positive electrode lead and the negative electrode lead at portions where the positive electrode lead and the negative electrode lead contact with a sealing portion of the battery case, respectively; At least one of the positive insulating film and the negative insulating film has a vent portion that is surface-treated with a non-adhesive material between the positive electrode lead or the negative electrode lead at a portion where the positive electrode lead or the negative electrode lead is attached, and The vent portion is formed in an area of ​​10% to 70% of an entire area where the positive electrode lead and the positive electrode insulating film, or the negative electrode lead and the negative electrode insulating film are attached.

2. The non-adhesive material is at least one polymer selected from the group consisting of polyimide-based materials, polytetrafluoroethylene, and polymethylpentene, or SiO ２ , TiO ２ 2. The secondary battery according to claim 1, comprising one or more ceramic particles selected from the group consisting of ZnO, CaO and BaO.

3. The secondary battery according to claim 1 , wherein the vent portion has a planar shape that is circular, elliptical or polygonal.

4. At least one of the positive electrode lead and the negative electrode lead is The secondary battery according to claim 1 , comprising: a metal substrate; and a coating layer formed on a surface of the metal substrate.

5. A method for producing the secondary battery according to any one of claims 1 to 4, comprising the steps of: (a) preparing at least one positive electrode and at least one negative electrode each having a structure in which an electrode active material layer is formed on a current collector having a tab formed on at least one side thereof; (b) interposing a separator between the positive electrode and the negative electrode; (c) forming a vent portion by transferring the unbonded material to at least one of the positive electrode insulating film and the negative electrode insulating film by a roll rolling method using a roll containing the unbonded material corresponding to the shape of the vent portion; (d) electrically connecting a positive electrode lead to a positive electrode tab, electrically connecting a negative electrode lead to the negative electrode tab, and attaching a positive electrode insulating film and a negative electrode insulating film onto the positive electrode lead and the negative electrode lead, respectively; The method for manufacturing a secondary battery, wherein the vent portion is interposed between the positive electrode lead and an attachment portion of the positive electrode insulating film, between the negative electrode lead and an attachment portion of the negative electrode insulating film, or both.

6. The non-adhesive material is at least one polymer selected from the group consisting of polyimide-based materials, polytetrafluoroethylene, and polymethylpentene, or SiO ２ , TiO ２ 6. The method for producing a secondary battery according to claim 5, wherein the ceramic particles are one or more selected from the group consisting of ZnO, CaO and BaO, which are coated in a gel state and then hardened.

7. The method for manufacturing a secondary battery according to claim 5 or 6, wherein the vent portion has a planar shape that is circular, elliptical or polygonal.

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