Battery cells with non-standard sticker-type protective tape

Abstract

The present invention provides a battery cell for a secondary battery, in which 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, The positive electrode has a positive electrode tab extending from a positive electrode current collector formed on one side thereof, and the negative electrode has a negative electrode tab extending from a negative electrode current collector formed on one side thereof, The positive electrode tab and the negative electrode tab each have a first bent portion and a second bent portion bent in a V shape at an upper end of the electrode assembly from which the positive electrode tab and the negative electrode tab protrude, a sticker-type protective tape is attached to one or more of the first and second bent portions and to an upper end of the electrode assembly adjacent to the first and second bent portions to cover the same; The sticker-type protective tape relates to battery cells that have irregular shapes.

Description

[Technical Field]

[0001] Cross-Citation of Related Applications This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0173368 dated December 7, 2021 and Korean Patent Application No. 10-2022-0168690 dated December 6, 2022, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

[0002] The present invention relates to a battery cell having a non-standard sticker-type protective tape formed thereon. [Background technology]

[0003] As technological development and demand for mobile devices increases, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, lithium secondary batteries, which exhibit high energy density and working potential, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Recently, the design of electronic devices has become a very important factor in consumer product selection, and electronic devices are becoming smaller and thinner in response to consumer preferences. As a result, in order to minimize unnecessary waste of internal space in electronic devices, lithium secondary batteries are also being required to be smaller and thinner, and demand for such batteries is increasing.

[0005] Such a lithium secondary battery is manufactured by manufacturing a positive electrode and a negative electrode, stacking them together with a separator to form an electrode assembly, and then placing the electrode assembly together with an electrolyte in a secondary battery case.

[0006] Meanwhile, in this process, protective tape is attached to the joint between the tap and lead of the electrode assembly, and the tap undergoes a V-forming process. However, such protective tape is generally attached only to the negative electrode portion, which causes pressure deviation between the positive and negative electrodes during a pressurization process of the manufactured electrode assembly, resulting in uneven adhesion. This uneven adhesion ultimately causes deviation in internal resistance due to cycles of the secondary battery.

[0007] Therefore, there is a pressing need to develop a technology for secondary batteries that can solve these problems. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides a battery cell that can improve cell performance by reducing pressure deviation in the longitudinal direction that occurs at the upper end of an electrode assembly where positive and negative electrode tabs are formed, thereby reducing internal resistance deviation due to uneven pressure.

[0009] Another object of the present invention is to provide a battery cell that can solve the problems that may arise during the process, such as reduced sealing performance due to the protective tape interfering with the battery case, by accurately attaching the protective tape at the correct position with flexible molding. [Means for solving the problem]

[0010] A battery cell according to an embodiment of the present invention includes: A battery cell for a secondary battery, in which 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, The positive electrode has a positive electrode tab extending from a positive electrode current collector on one side thereof, and the negative electrode has a negative electrode tab extending from a negative electrode current collector on one side thereof, The positive electrode tab and the negative electrode tab have a first bent portion and a second bent portion bent in a V shape at an upper end of the electrode assembly from which the positive electrode tab and the negative electrode tab protrude, respectively; a sticker-type protective tape is attached to one or more of the first and second bent portions and an upper end of the electrode assembly adjacent to the first and second bent portions to cover the same; The sticker-type protective tape is characterized by having an irregular shape.

[0011] At this time, the sticker-type protective tape is a sticker cut into an irregular shape and may be made of cast polypropylene (CPP).

[0012] The sticker-type protective tape may have a shape including a convex portion covering at least one of the first bent portion and the second bent portion and a concave portion having a smaller width than the convex portion.

[0013] In detail, the convex portion can cover the second bent portion where the negative electrode tap is bent in a V shape, or the convex portion can be formed in two so that it covers both the first bent portion where the positive electrode tap is bent in a V shape and the second bent portion where the negative electrode tap is bent in a V shape.

[0014] In one example, when the protrusion covers only the second folded portion, the electrode assembly may be a single-sided positive electrode in which the outermost electrode in the stacking direction is a positive electrode and a positive electrode active material layer is formed on only one side of the positive electrode current collector. The thickness of the sticker-type protective tape may be 10 μm to 100 μm.

[0015] The sticker-type protective tape may have a length sufficient to cover the upper end of the electrode assembly adjacent to the positive electrode tab and the negative electrode tab.

[0016] Meanwhile, the positive electrode and the negative electrode each have a flat portion where the active material layer has a constant thickness and a slope portion where the thickness of the active material layer gradually decreases from the flat portion, the inclined portion is formed at an end portion in a direction in which the positive electrode tab of the positive electrode and the negative electrode tab of the negative electrode protrude, The upper end of the electrode assembly where the sticker-type protective tape is formed may be a portion corresponding to the inclined portion.

[0017] The positive electrode tab and the negative electrode tab may be respectively connected to a positive electrode lead and a negative electrode lead, and the positive electrode lead and the negative electrode lead may be respectively connected to a first bent portion of the positive electrode tab and a second bent portion of the negative electrode tab.

[0018] The positive electrode lead and the negative electrode lead may protrude to the outside of the battery case, and a sealing member may be formed at a portion where the positive electrode lead and the negative electrode lead contact the battery case.

[0019] In this case, the sealing member may be made of one or more materials selected from the group consisting of polyphenylene ether (PPE), polyimide (PI), polypropylene (PP), polyethyleneterephthalate (PET), polyphenylene sulfide (PPS), and polyethylene (PE).

[0020] On the other hand, the battery cell may be a lithium secondary battery. [Effects of the Invention]

[0021] In the battery cell according to the present invention, a sticker-type protective tape is formed to cover all of the folded portions of the positive and negative electrode tabs, thereby reducing the pressure deviation in the longitudinal direction that occurs at the upper end of the electrode assembly where the positive and negative electrode tabs are formed, thereby reducing the internal resistance deviation due to uneven pressure and improving cell performance.

[0022] In addition, by forming the protective tape into a cut sticker type, the protective tape can be attached accurately with free formability, thereby eliminating the problem of reduced sealing performance caused by the protective tape interfering with the battery case, thereby improving safety and cell performance.

[0023] Furthermore, by using a pre-cut sticker-type protective tape, it is possible to prevent the deterioration of the mold life due to the adhesive layer that occurs when cutting the tape using a conventional mold. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 2 is a plan view of a battery cell tap according to an embodiment of the present invention before v-forming. [Figure 2] FIG. 10 is a plan view of a battery cell tap according to another embodiment of the present invention before V-forming; [Figure 3] FIG. 3 is a plan view of the battery cell of FIG. 2 after V-forming of the tap. [Figure 4] FIG. 3 is a cross-sectional view of the battery cell of FIG. 2. [Figure 5] Figure 2 is a schematic diagram of a sticker-type protective tape. [Figure 6] 3D scan of the electrode assembly of Example 1 after cycling according to Experimental Example 1. [Figure 7] 3D scans of the electrode assembly of Comparative Example 1 after cycling according to Experimental Example 1. [Figure 8] 10 is a photograph of the upper end of the electrode assembly of Example 1 according to Experimental Example 2. [Figure 9]10 is a photograph of the upper end of an electrode assembly of Comparative Example 2 according to Experimental Example 2. [Figure 10] 10 is a photograph showing the results of pressure-sensitive paper on the upper end of the electrode assembly of Example 1 according to Experimental Example 3. [Figure 11] 10 is a photograph showing the results of pressure-sensitive paper on the upper end of the electrode assembly of Comparative Example 1 according to Experimental Example 3. [Figure 12] 10 is a comparative graph showing the measurement of the magnitude of pressure applied to the upper end of the secondary batteries of Example 1 and Comparative Example 1 according to Experimental Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0025] The terms and words used in this specification and claims should not be interpreted in their ordinary or dictionary sense, but should be interpreted in a sense and concept that corresponds to 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 explain their inventions.

[0026] Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely preferred embodiments of the present invention and do not fully represent the technical ideas of the present invention. Therefore, there may be various equivalents and modifications that can replace them at the time of filing this application, and the scope of the present invention is not limited to the embodiments described below.

[0027] The present invention will now be described in detail with reference to the drawings and embodiments.

[0028] According to one embodiment, the present invention comprises: A battery cell for a secondary battery, in which 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, The positive electrode has a positive electrode tab extending from a positive electrode current collector on one side thereof, and the negative electrode has a negative electrode tab extending from a negative electrode current collector on one side thereof, The positive electrode tab and the negative electrode tab have a first bent portion and a second bent portion bent in a V shape at an upper end of the electrode assembly from which the positive electrode tab and the negative electrode tab protrude, respectively; a sticker-type protective tape is attached to one or more of the first and second bent portions and an upper end of the electrode assembly adjacent to the first and second bent portions to cover the same; The sticker-type protective tape is provided for battery cells having irregular shapes.

[0029] At this time, the sticker-type protective tape is a sticker cut into an irregular shape and may be made of cast polypropylene (CPP).

[0030] The protective tape is in the form of a cut sticker, which can be easily peeled off from the substrate and attached, making it very easy to use.

[0031] Furthermore, by using this type of sticker, there is no need to use a mold for cutting the protective tape, which solves the problem of adhesive substances adhering to the mold caused by cutting.

[0032] The material of the protective tape is not limited as long as it is an organic material with insulating and adhesive properties, but specifically, it may be solid polypropylene (CPP). Solid polypropylene has excellent heat sealing properties and chemical resistance. Furthermore, it is the same material as the polymer film of the secondary battery case, and is stable and does not cause any side reactions in lithium secondary batteries that use organic solvents as electrolytes, making it suitable for use in such protective tapes.

[0033] Meanwhile, the sticker-type protective tape can be formed into an irregular shape.

[0034] As mentioned above, when an electrode assembly is mounted in a laminated sheet battery case in a typical pouch-type battery cell, the electrode tabs are V-formed and connected to the electrode leads to increase the upper space efficiency. During this process, a short circuit can occur in the electrodes that make up the outermost shell due to impact or dropping, so a device that can protect against this is required.

[0035] As a result, protective tape was attached in the past, but since the negative electrode was manufactured to be located mainly on the outermost shell, protective tape was attached only to the negative electrode tap V-forming portion and a portion of the upper end of the electrode assembly connected to it.

[0036] However, when such an attachment is made, uneven pressure occurs in the length direction at the upper end of the electrode assembly where the positive and negative electrode tabs are formed, resulting in internal resistance deviation and a decrease in cell performance.

[0037] Therefore, the inventors of the present application have confirmed that the resistance deviation problem can be resolved by attaching protective tape to cover the entire upper end of the electrode assembly adjacent to the first bent portion of the positive electrode tab and the second bent portion of the negative electrode tab.

[0038] However, when the protective tape is usually cut into a rectangular or square shape for use, it may be attached at an angle or to one side due to issues such as equipment setup or worker proficiency. As a result, when V-forming is performed later, interference with the sealing film occurs due to the offset, or an unattached portion occurs due to the inability to fold, which can cause problems with the sealing quality of the battery case.

[0039] Therefore, the inventors of the present application have conducted in-depth research to solve this problem, and have discovered that when the protective tape is formed into an irregular sticker type, the problem of reduced sealing performance caused by the protective tape interfering with the battery case can be solved by accurately positioning the protective tape with flexible formability, and have thus completed the present invention.

[0040] To achieve this effect most effectively, more specifically, the sticker-type protective tape may have a shape having a convex portion that covers at least one of the first folding portion and the second folding portion, and a concave portion that is narrower than the convex portion.

[0041] In detail, the convex portion can cover the second bent portion where the negative electrode tap is bent in a V shape, or the convex portion can be formed in two so that it covers both the first bent portion where the positive electrode tap is bent in a V shape and the second bent portion where the negative electrode tap is bent in a V shape.

[0042] In one example, when the convex portion covers only the second folded portion, the electrode assembly may be a single-sided positive electrode in which the outermost electrode in the stacking direction is a positive electrode and a positive electrode active material layer is formed on only one side of the positive electrode current collector.

[0043] In another example, when the convex portion covers both the first and second folding portions, the electrode assembly may be a single-sided negative electrode in which the outermost electrode in the stacking direction is a negative electrode and the negative electrode active material layer is formed on only one side of the negative electrode current collector, or the outermost electrode may be a single-sided positive electrode as described above, or the outermost electrode may be a double-sided negative electrode in which the active material layer is formed on both sides of the current collector, or a double-sided positive electrode, and is not limited thereto.

[0044] The reason why the sticker-type protective tape must cover the negative electrode tab is that the metal used in the negative electrode tab is highly reducible and may cause corrosion of the battery case if it comes into contact with the metal of the battery case. On the other hand, it is more preferable to cover the positive electrode tab as well, since this can also prevent damage to the polymer layer of the battery case.

[0045] Such a configuration is shown in the following FIGS. 1 to 5, and will be described in more detail below with reference to the drawings.

[0046] First, FIG. 1 shows a plan view of a battery cell tap according to one embodiment of the present invention before v-forming.

[0047] 1, a battery cell 100 according to an embodiment of the present invention has an electrode assembly 110 housed in a battery case 120, a positive electrode tab 111 and a negative electrode tab 112 extending parallel to one side from the positive electrode current collector and the negative electrode current collector of the electrode assembly 110 without overlapping, and the positive electrode tab 111 and the negative electrode tab 112 are connected to a positive electrode lead 141 and a negative electrode lead 142 protruding to the outside of the battery case 120, respectively. In addition, sealing members 151 and 152 are formed at the portions where the positive electrode lead 141 and the negative electrode lead 142 contact the battery case 120.

[0048] Meanwhile, the portions where the positive electrode tab 111 and the negative electrode tab 112 are connected to the positive electrode lead 141 and the negative electrode lead 142 are bent into a V shape (V-forming), which becomes the first bent portion and the second bent portion. Therefore, in the battery cell 100 of FIG. 1, the first bent portion and the second bent portion are collectively indicated as A.

[0049] In addition, in the battery cell 100 according to an embodiment of the present invention, a sticker-type protective tape 130 is attached to the second folded portion and the upper end of the electrode assembly 110 adjacent to the region A of the first folded portion and the second folded portion to cover them.

[0050] Therefore, the sticker-type protective tape 130 has a convex portion that is convex toward the second bent portion to cover the second bent portion, and a concave portion that is narrower than the convex portion at the upper end of the electrode assembly 110 to entirely surround only the upper end of the electrode assembly 110. That is, the convex portion may have a width sufficient to cover the entire second bent portion, and the concave portion may have a width sufficient to cover only the upper end of the electrode assembly 110.

[0051] In addition, in order to reduce pressure deviation at the upper end of the electrode assembly, the length of the sticker-type protective tape 130 is formed to a length (l1) that can cover the upper end of the electrode assembly 110 adjacent to the positive electrode tab 111 and the negative electrode tab 112.

[0052] In this case, the outermost electrode of the electrode assembly 110 may be, but is not limited to, a single-sided positive electrode in which a positive electrode active material layer is formed only on one side of a positive electrode current collector. In this case, the positive electrode active material layer is formed only on the portion facing the inner negative electrode.

[0053] The specific shape of such a sticker-type protective tape 130 will be described in more detail below.

[0054] To further explain the present invention, FIG. 2 shows a planar perspective view of a tap of a battery cell according to another embodiment of the present invention before V-forming, and FIG. 3 shows a planar perspective view of the tap of the battery cell of FIG. 2 after V-forming.

[0055] Additionally, to more specifically explain the folding portion where v-forming is performed, Fig. 4 shows a cross-sectional view of the battery cell of Fig. 2, and Fig. 5 shows a schematic diagram of a sticker-type protective tape to more specifically explain the shape of the sticker-type protective tape. The only difference between Fig. 1 and Fig. 2 is the shape of the sticker-type protective tape, and the content described below also applies to Fig. 1.

[0056] 2 to 4, similar to the battery cell 100, the battery cell 200 has an electrode assembly 210 housed in a battery case 220, a positive electrode tab 211 and a negative electrode tab 212 extending parallel to one side from the positive electrode current collector and the negative electrode current collector of the electrode assembly 210 without overlapping, and the positive electrode tab 211 and the negative electrode tab 212 are connected to a positive electrode lead 241 and a negative electrode lead 242, respectively.

[0057] Here, the positive electrode tab 211 and the negative electrode tab 212 each have a first bent portion and a second bent portion bent into a V shape by a V-forming process.

[0058] In this region B, the positive electrode lead 241 and the negative electrode lead 242 are respectively connected to the positive electrode tab 211 and the negative electrode tab 212, and the positive electrode lead 241 and the negative electrode lead 242 protrude to the outside of the battery case 220, and sealing members 251 and 252 are formed at the portions that come into contact with the battery case 220.

[0059] The sealing member may be made of any material that can enhance adhesion to the battery case and improve sealing performance, and may be made of, for example, one or more materials selected from the group consisting of polyphenylene ether (PPE), polyimide (PI), polypropylene (PP), polyethyleneterephthalate (PET), polyphenylene sulfide (PPS), and polyethylene (PE).

[0060] Meanwhile, in the battery cell 200 according to an embodiment of the present invention, in the first and second folding portion region B, sticker-type protective tapes 230 are attached to both sides of the first and second folding portions and the upper end of the electrode assembly 210 adjacent to the first and second folding portion region B to cover them.

[0061] 2 and 5, each sticker-type protective tape 230 has two protrusions 231 that cover the first and second folding portions, and a recess 232 that is narrower than the protrusions 231 and is formed to cover only the upper end of the electrode assembly 210.

[0062] Here, the outermost electrode of the electrode assembly 110 is not limited, and a single-sided positive electrode, a single-sided negative electrode, a double-sided positive electrode, or a double-sided negative electrode may all be disposed. In this case, the convex portion 231 may have a width sufficient to cover the entire first and second bent portions in the first and second bent portion region B, and the concave portion 232 may have a width sufficient to cover only the upper end of the electrode assembly 210.

[0063] Therefore, the attachment position of the sticker-type protective tape 230 can be accurately determined to correspond to the shape, and the convex portion of the sticker-type protective tape 230 is formed only at the portion where the tap is formed. Therefore, as shown in FIG. 3, when the electrode tap is bent after the V-forming process, the sticker-type protective tape 230 located at the upper end of the electrode assembly 210 is significantly less likely to be caught in the sealing portion of the battery case 220, thereby eliminating the problem of reduced sealing performance due to interference with the sealing portion and improving safety and cell performance.

[0064] Meanwhile, although not shown in the drawings, the positive and negative electrodes each have a flat portion where the active material layer has a uniform thickness and a sloped portion where the thickness of the active material layer gradually decreases from the flat portion, and the sloped portion is formed at the end portion in the direction in which the positive electrode tab 211 and the negative electrode tab 212 protrude. In this case, the upper end of the electrode assembly 210 where the sticker-type protective tape 230 is formed may be a portion corresponding to the sloped portion of the electrode.

[0065] In this case, a separate protective tape 230 is formed on the upper end of the electrode assembly 210 corresponding to the inclined portion of the electrode, so that when a subsequent lamination process is performed, the protective tape 230 can cover the difference in thickness between the flat portion and the inclined portion, and the portion corresponding to the inclined portion of the electrode can also receive the same pressure, which is preferable.

[0066] Meanwhile, in the conventional case where a protective tape is formed only on one side of the negative electrode tab, in order to reduce the pressure difference that occurs between the upper end of the electrode assembly adjacent to the positive electrode tab and the upper end of the electrode assembly adjacent to the negative electrode tab, the length of the sticker-type protective tape 230 according to the present invention is formed to a length (l2) that can cover the upper end of the electrode assembly 210 adjacent to the positive electrode tab 211 and the negative electrode tab 212, as shown in FIG.

[0067] Therefore, according to the present invention, the pressure deviation in the length direction of the upper end of the electrode assembly is reduced, and therefore the internal resistance deviation is also reduced, resulting in further improved cell performance.

[0068] Furthermore, the thickness (t) of each sticker-type protective tape 230 may be 10 μm to 100 μm, more specifically 30 μm to 50 μm, as long as it does not increase the volume of the battery cell 200. In this case, the thicknesses of the sticker-type protective tapes 230 on both sides may be different or the same.

[0069] If the thickness is too thin, i.e., outside the above range, the protective tape cannot be effective, and if the thickness is too thick, the thickness and volume of the battery cell may increase, which is undesirable.

[0070] Specific manufacturing methods and constituent materials of components other than the sticker-type protective tape, such as a positive electrode, a negative electrode, a separator, and a battery case, are well known in the art, and therefore, description thereof will be omitted herein.

[0071] Meanwhile, the battery cell according to the present invention may specifically be a lithium secondary battery.

[0072] Other components of the lithium secondary battery are well known in the art, and therefore a description thereof will be omitted here. [Example]

[0073] Example 1 A slurry for the positive electrode active material layer was prepared by mixing LiCoO2 as a positive electrode active material, carbon black as a conductive material, and PVDF as a binder in an N-methylpyrrolidone solvent in a weight ratio of 97:1:2. The slurry for the positive electrode active material layer was coated onto one side of a 10 μm-thick aluminum (Al) thin film positive electrode current collector using a slot die and dried under vacuum at 130°C for 1 hour to form an active material layer. The active material layer thus formed was rolled using a roll pressing method until the porosity of the flat part of the active material layer was 20%, thereby preparing a positive electrode having an active material layer with a thickness of 90 μm.

[0074] A slurry for the active material layer was prepared by mixing a 96:2:2 mixture of artificial graphite as the negative electrode active material, a binder (a 2:1 mixture by weight of SBR and CMC), and carbon black as the conductive material in a weight ratio of 96:2:2 with water as the dispersion medium in a weight ratio of 1:2. The slurry for the active material layer was coated onto one side of a 10 μm-thick copper (Cu) thin film negative electrode current collector using a slot die and dried at 130°C under vacuum for 1 hour to form an active material layer. The active material layer thus formed was rolled using a roll pressing method until the porosity of the flat part of the active material layer was 24%, producing a negative electrode with an active material layer having a thickness of 120 μm.

[0075] An electrode assembly was fabricated by placing a porous polyethylene separator between the cathode and anode fabricated as described above, and then attaching sticker-type protective tape to both sides of the electrode assembly to cover the top end and the bent portion of the tap, as shown in Figure 2. Then, a sealing member was attached to the lead portion that contacts the battery case, and the electrode assembly was placed inside the battery case, and an electrolyte was injected into the case.

[0076] After the electrolyte injection, the lithium secondary battery was subjected to an activation process using a pressure of 1.2 MPa (charging at 0.2 C, SOC 5%, then charging to 2.0 C, SOC 65%) and degassed to prepare a final lithium secondary battery.

[0077] <Comparative Example 1> A lithium secondary battery was fabricated in the same manner as in Example 1, except that a protective tape was attached to cover only the bent portion of the negative electrode tab of the electrode assembly fabricated in Example 1 and the adjacent upper end of the electrode assembly.

[0078] <Comparative Example 2> A lithium secondary battery was fabricated in the same manner as in Example 1, except that rectangular protective tapes were attached to cover the bent portions of the positive and negative electrode tabs of the electrode assembly fabricated in Example 1 and the adjacent upper ends of the electrode assemblies.

[0079] <Experimental Example 1> The lithium secondary batteries prepared in Example 1 and Comparative Example 1 were charged and discharged 177 times at 0.5 C in the range of 4.47 V to 3.2 V at 45° C., then removed from the batteries in a state of 100% SOC and cooled at room temperature for 4 hours. The results of 3D scanning were then shown in FIGS. 6 and 7.

[0080] 6 and 7, it can be seen that in the lithium secondary battery prepared in Comparative Example 1, side reactions occurred below the cathode during the charge / discharge process due to uneven pressure at the top, which was shown as an uneven surface state in the 3D scan.

[0081] <Experimental Example 2> Photographs of the upper ends of the lithium secondary batteries prepared in Example 1 and Comparative Example 2 were taken and are shown in FIGS. 8 and 9 below.

[0082] 8 and 9, it can be seen that sealing interference occurred in the lithium secondary battery manufactured in Comparative Example 2.

[0083] <Experimental Example 3> Pressure sensitive paper was photographed at the upper end of the electrode assemblies prepared in Example 1 and Comparative Example 1, and the results are shown in FIGS. 10 and 11 below.

[0084] The pressure sensing paper is sandwiched between the pressure injection device and the electrode assembly during the manufacturing process of the electrode assembly, and subsequently senses the pressure measured at each position, thereby visually confirming the pressure uniformity.

[0085] 10 and 11, it can be seen that almost no pressure is applied to the upper end of the lithium secondary battery manufactured in Comparative Example 1 where no protective tape is attached, whereas it can be seen that sufficient pressure is applied to the upper end of the lithium secondary battery manufactured in Example 1.

[0086] <Experimental Example 4> The jig pressure applied to the upper end of the lithium secondary batteries manufactured in Example 1 and Comparative Example 1 was measured, and the results are shown in FIG.

[0087] The jig pressure was measured by a digital pressure sensor.

[0088] The digital pressure gauge is located between the jig that applies pressure during the activation process and the secondary battery in Example 1 and Comparative Example 1, and when the pressure of the jig reaches a target value, it reads information about the actual pressure applied to the secondary battery and graphs that pressure.

[0089] 12, it can be seen that almost no pressure is applied to the upper end portion of the lithium secondary battery manufactured in Comparative Example 1 where no protective tape is attached. In contrast, it can be seen that sufficient pressure is applied to the upper end portion of the lithium secondary battery manufactured in Example 1, and the overall pressure distribution is uniform.

[0090] Those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above content.

Claims

1. A battery cell for a secondary battery, in which 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, The positive electrode has a positive electrode tab extending from a positive electrode current collector on one side thereof, and the negative electrode has a negative electrode tab extending from a negative electrode current collector on one side thereof, The positive electrode tab and the negative electrode tab have a first bent portion and a second bent portion bent in a V shape at an upper end of the electrode assembly from which the positive electrode tab and the negative electrode tab protrude, respectively; a protective tape is attached to one or more of the first and second bent portions and an upper end of the electrode assembly adjacent to the first and second bent portions to cover the same; the protective tape has a shape including a convex portion covering at least one of the first bent portion and the second bent portion and a concave portion having a smaller width than the convex portion, The protective tape is made of cast polypropylene (CPP). Battery cell.

2. A battery cell for a secondary battery, in which 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, The positive electrode has a positive electrode tab extending from a positive electrode current collector on one side thereof, and the negative electrode has a negative electrode tab extending from a negative electrode current collector on one side thereof, The positive electrode tab and the negative electrode tab have a first bent portion and a second bent portion bent in a V shape at an upper end of the electrode assembly from which the positive electrode tab and the negative electrode tab protrude, respectively; a protective tape is attached to one or more of the first and second bent portions and an upper end of the electrode assembly adjacent to the first and second bent portions to cover the same; the protective tape has a shape including a convex portion covering at least one of the first bent portion and the second bent portion and a concave portion having a smaller width than the convex portion; Battery cell.

3. 3. The battery cell of claim 1, wherein the protrusion covers a second bent portion where the negative electrode tab is bent in a V shape, and the electrode assembly is a single-sided positive electrode in which the outermost electrode in the stacking direction is a positive electrode and a positive electrode active material layer is formed only on one side of the positive electrode current collector.

4. 3. The battery cell according to claim 1, wherein the protrusions are formed in two portions so as to completely cover a first bent portion where the positive electrode tab is bent in a V shape and a second bent portion where the negative electrode tab is bent in a V shape.

5. 3. The battery cell according to claim 1, wherein the protective tape has a thickness of 10 μm to 100 μm.

6. The battery cell of claim 1 or 2, wherein the protective tape has a length sufficient to cover upper ends of the electrode assembly adjacent to the positive electrode tab and the negative electrode tab.

7. The positive electrode and the negative electrode each have a flat portion where an active material layer has a constant thickness and a slope portion where the thickness of the active material layer gradually decreases from the flat portion, the inclined portion is formed at an end portion in a direction in which the positive electrode tab of the positive electrode and the negative electrode tab of the negative electrode protrude, The battery cell according to claim 1 or 2, wherein the upper end of the electrode assembly on which the protective tape is formed corresponds to the inclined portion.

8. 3. The battery cell according to claim 1, wherein the positive electrode tab and the negative electrode tab are respectively connected to a positive electrode lead and a negative electrode lead, and the positive electrode lead and the negative electrode lead are respectively connected to a first bent portion of the positive electrode tab and a second bent portion of the negative electrode tab.

9. 9. The battery cell according to claim 8, wherein the positive electrode lead and the negative electrode lead protrude to the outside of the battery case, and a sealing member is formed at a portion where the positive electrode lead and the negative electrode lead contact the battery case.

10. 10. The battery cell of claim 9, wherein the sealing member is made of one or more materials selected from the group consisting of polyphenylene ether (PPE), polyimide (PI), polypropylene (PP), polyether terephthalate (PET), polyphenylene sulfide (PPS), and polyethylene (PE).

11. The battery cell according to claim 1 or 2, wherein the battery cell is a lithium secondary battery.

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