Electrode assembly including tape for securing the outside of the laminate, and secondary battery including the same.

Abstract

The present invention includes a laminate comprising a positive electrode, a negative electrode, and a separation membrane interposed between the positive and negative electrodes, and one or more pairs of tapes for securing the outside of the laminate. The pair of tapes includes non-overlapping portions that do not overlap each other and overlapping portions that overlap each other. The present invention provides an electrode assembly in which the width of the non-overlapping portion is greater than the width of the overlapping portion, and a secondary battery including the same.

Description

Technical Field

[0001] [Cross - reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2023 - 0061582 filed on May 12, 2023 and Korean Patent Application No. 10 - 2024 - 0061550 filed on May 10, 2024, and all the contents disclosed in the documents of the Korean patent applications are included as part of this specification.

[0002] The present invention relates to an electrode assembly including a tape for fixing the exterior of a laminate and a secondary battery including the same.

Background Art

[0003] Due to the rapid increase in the use of fossil fuels, the demand for the use of alternative and clean energies has been increasing. As part of this, the fields of power generation and power storage using electrochemistry are the most actively studied.

[0004] Currently, a typical example of an electrochemical device that utilizes such electrochemical energy is a secondary battery, and its usage areas are increasingly expanding. [[ID=2…]]

[0005] Recently, as the technology development and demand for portable devices such as portable computers, mobile phones, and cameras have increased, the demand for secondary batteries as an energy source has rapidly increased. Among such secondary batteries, many studies have been conducted on lithium secondary batteries that exhibit high charge / discharge characteristics and long - life characteristics and are environmentally friendly, and they have also been commercialized and widely used.

[0006] Furthermore, the secondary battery has recently been evolving into a configuration with higher energy density and higher output according to user requirements, but in this case, it has the problem of lower safety.

[0007] In particular, gas generation during the activation process tends to increase with higher energy density secondary batteries, necessitating a technique for uniformly pressurizing and promptly releasing the generated gas as described above.

[0008] However, referring to Figures 1 and 2, in the case of conventional stack-type, stack-folding-type, or stack-lamination-type electrode assemblies 10, tapes 11, 12, and 13 are attached to the outside of the electrode assembly 10 to fix the components. These tapes 11, 12, and 13 each come in pairs, and as can be seen from the enlarged view in Figure 2, there is an overlapping portion 11c where the respective unit tapes 11a and 11b overlap.

[0009] However, when gas is generated during the activation process, tapes 11, 12, and 13 exert a force in the opposite direction to the direction in which the gas is generated and discharged. As a result, the pressurizing force in the areas where tapes 11, 12, and 13 are located is higher than in the case where this is not the case, and this is even greater in the overlapping section 11c. This is also true when pressurizing for gas discharge.

[0010] Figure 3 shows a table of applied pressure measured by a pressure sensor to demonstrate that the applied pressure in the overlapping area is greater than in other areas when using a secondary battery with an electrode assembly structure like that shown in Figure 1 (where the overlapping area of ​​the tape exceeds 20%).

[0011] Specifically, the manufactured rechargeable battery was charged at 1C under constant current / constant voltage (CC / CV) conditions at 25°C until it reached 4.35V / 38mA, followed by an activation process in which it was discharged at 2C under constant current (CC) conditions until it reached 2.5V. The pressure applied to the rechargeable battery during the activation process was confirmed at different locations using an electronic pressure sensor (Kitronic Corporation), and the pressure index value was numerically expressed based on the center of the rechargeable battery.

[0012] Referring to Figure 3, it can be seen that the pressure in the overlapping areas of the tape increases significantly more than in other areas, and that the area of ​​the region where the pressure increases significantly is large, as indicated in red.

[0013] Therefore, the pressurizing force in the superimposed area 11c is greater than the pressurizing force in areas other than the superimposed area 11c, resulting in greater non-uniform pressurization in the medium- and large-sized batteries. This causes gas to accumulate in areas with lower pressurization, hindering the smooth discharge of the gas.

[0014] Therefore, there is an urgent need to develop a secondary battery that can smoothly discharge the gas generated during the activation process and improve safety. [Overview of the Initiative] [Problems that the invention aims to solve]

[0015] The problem that this invention aims to solve is to provide a secondary battery with improved safety by minimizing the area that is unevenly pressurized by the tape that fixes the outside of the electrode assembly, thereby facilitating the discharge of gases generated during the activation process. [Means for solving the problem]

[0016] An electrode assembly according to one embodiment of the present invention for achieving such objectives is: A laminate comprising a positive electrode, a negative electrode, and a separation membrane interposed between the positive and negative electrodes, and one or more pairs of tapes for securing the outside of the laminate, The pair of tapes includes non-overlapping portions that do not overlap each other and overlapping portions that overlap each other. The width of the non-overlapping portion may be greater than the width of the overlapping portion.

[0017] Specifically, the pair of tapes may consist of two or more unit tapes, and each unit tape may include a central portion and a tapered portion having a tapered structure in which the width decreases from the central portion toward both ends.

[0018] In this case, the tapered portion may have a width that gradually decreases toward both ends, and more specifically, the tapered portion may have a triangular, trapezoidal, or semicircular shape.

[0019] As a result, the total area of the overlapping portion may be 1% to 20% of the total area surrounded by the pair of tapes.

[0020] In one example, the pair of tapes may be composed of two unit tapes.

[0021] Also, the overlapping portion can be located on the upper surface, or the lower surface, or both the upper and lower surfaces with respect to the stacking direction of the laminate.

[0022] In another specific example, two or more pairs of tapes may be included, and the two or more pairs of tapes may be attached so as to fix the outside of the laminate at intervals of 1 to 4 times the thickness of the laminate.

[0023] Specifically, the intervals between the two or more pairs of tapes may be constant. More specifically, on the upper surface of the laminate, the respective areas divided by the two or more pairs of tapes may be the same.

[0024] Also, the width of the pair of tapes may be 10 mm to 50 mm.

[0025] Therefore, the total area surrounded by the one or more pairs of tapes may be 10% to 40% of the total surface area of the laminate.

[0026] On the other hand, the pair of tapes may contain polyimide.

[0027] Furthermore, according to one embodiment of the present invention, a secondary battery is provided that includes the electrode assembly, an electrolyte, and a battery case that houses the electrode assembly and the electrolyte.

[0028] At this time, the secondary battery may be a pouch-type secondary battery.

Brief Description of the Drawings

[0029] [Figure 1] Figure 1 is a perspective view of a conventional electrode assembly. [Figure 2] Figure 2 is an enlarged schematic diagram of the tape shown in Figure 1. [Figure 3] Figure 3 is a table of the pressure applied during the activation process of a secondary battery using conventional fixing tape, as measured by a pressure sensor. [Figure 4] Figure 4 is a perspective view of an electrode assembly according to one embodiment of the present invention. [Figure 5] Figure 5 is an enlarged schematic diagram of the pair of tapes shown in Figure 4. [Figure 6] Figure 6 is a table showing the applied pressure during the activation process of a secondary battery using the tape of the present invention, as measured by a pressure sensor. [Modes for carrying out the invention]

[0030] The present invention will be described in more detail below to aid in understanding the invention.

[0031] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best describe their invention.

[0032] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0033] Furthermore, when a specification states that a certain part "includes" a certain component, unless otherwise stated, this means that it can further include other components rather than excluding them.

[0034] An electrode assembly according to one embodiment of the present invention is A laminate comprising a positive electrode, a negative electrode, and a separation membrane interposed between the positive and negative electrodes, and one or more pairs of tapes for securing the outside of the laminate, The pair of tapes includes non-overlapping portions that do not overlap each other and overlapping portions that overlap each other. The width of the non-overlapping portion may be greater than the width of the overlapping portion.

[0035] Figure 4 schematically shows a perspective view of an electrode assembly according to one embodiment of the present invention, and Figure 5 shows an enlarged schematic diagram of one pair of tapes from Figure 3.

[0036] Referring to Figure 4, the electrode assembly 100 according to one embodiment of the present invention has a structure that includes a laminate 110 containing a positive electrode, a negative electrode, and a separation membrane interposed between the positive electrode and the negative electrode, and three pairs of tapes 120, 130, and 140 that fix the outside of the laminate 110.

[0037] In this case, referring to Figures 4 and 5, each pair of tapes 120, 130, and 140 includes one or more non-overlapping portions that do not overlap each other and overlapping portions 123, 133, and 143 that do overlap each other, and the width of the overlapping portions 123, 133, and 143 is smaller than the width of the non-overlapping portions.

[0038] More specifically, referring to Figure 5, in order to reduce the area S11 of the overlapping portion 123, the pair of tapes 120 are composed of two unit tapes 121 and 122, each unit tape 121 and 122 including central portions 121a and 122a and tapered portions 121b and 122b having a tapered structure in which its width w decreases from the central portions 121a and 122a toward both ends.

[0039] In this case, the tapered portions 121b and 122b may have a structure in which their width w gradually decreases toward both ends, and in terms of shape, the tapered portions 121b and 122b may be triangular, trapezoidal, or semicircular in shape, and more specifically, they may be trapezoidal as shown in Figure 4.

[0040] Therefore, when unit tapes 121 and 122 are used as a pair to surround the outside of the laminate 110, an overlapping portion 123 is formed at both ends of the tapered portions 121b and 122b, and the area S11 of the overlapping portion 123 is reduced compared to when tapes without tapered portions 121b and 122b are used.

[0041] Therefore, the areas S11, S21, and S31 of the overlapping portions 123, 133, and 143 are reduced, which reduces the area of ​​the portion where the pair of tapes 120, 130, and 140 are not formed, and the area of ​​the region with the highest pressure compared to the non-overlapping portion, thereby reducing the unevenness of pressure and enabling the effects intended by this invention to be achieved.

[0042] In this case, the total areas S11, S21, and S31 of the overlapping sections 123, 133, and 143 in each case may be between 1% and 20% of the total areas S1, S2, and S3 enclosed by the pair of tapes 120, 130, and 140, respectively.

[0043] More specifically, the total areas S11, S21, and S31 of the overlapping sections 123, 133, and 143 in each case may be 2% to 15% of the total areas S1, S2, and S3 enclosed by the pair of tapes 120, 130, and 140, respectively, and more specifically, 3% to 10%.

[0044] If the area is outside the range described above and is excessively large, as explained in the background technology described above, there is a problem that, similar to conventional electrode assemblies, a large amount of pressure is applied at the overlapping portion, increasing the non-uniformity of the pressure and hindering the smooth discharge of gas. If the area is excessively small, the area where the pair of tapes are adhered to each other decreases, reducing the adhesive strength, which may reduce the original purpose of using the tape, namely the fixing strength of the laminate, and is therefore undesirable.

[0045] Figures 4 and 5 show pairs of tapes 120, 130, and 140, each composed of two unit tapes 121 and 122. However, the pairs of tapes 120, 130, and 140 may include three or more unit tapes. In other words, a pair here refers to a bundle of tapes wound around the laminate at the same position, and does not necessarily mean two pairs of unit tapes. Therefore, the number of unit tapes is not limited, or it is preferable that the area of ​​the overlapping portion is reduced, and more specifically, it is more preferable that they are composed of two unit tapes.

[0046] Referring again to Figure 4, the overlapping portions 123, 133, and 143 of the pair of unit tapes 120, 130, and 140 can be located on the top surface, the bottom surface, or both the top and bottom surfaces, relative to the stacking direction of the laminate 110. In other words, when one overlapping portion 123, 133, and 143 is formed by each pair of tapes 120, 130, and 140, it may be formed on the top or bottom surface relative to the stacking direction of the laminate 110, and when two overlapping portions 123, 133, and 143 are formed, they may be located on the top and bottom surfaces relative to the stacking direction of the laminate 110.

[0047] In other words, the overlapping portions 123, 133, and 143 are preferably formed on the flat surface of the laminate 110, and may be formed on the top surface, the bottom surface, or both the top and bottom surfaces. The sides of the laminate 110 have different sizes for the positive electrode, negative electrode, and separation membrane, making it difficult to bond a pair of tapes 120, 130, and 140 together. Therefore, it is more preferable to surround them with a single unit tape for better fixing strength.

[0048] On the other hand, Figure 4 discloses a configuration that includes three pairs of tapes 120, 130, and 140, but it may include only one, and more specifically, two or more may be included for the fixing force of the laminate 110. However, considering the fixing force of the laminate 110 and the non-uniformity of pressure due to the use of tape, it is preferable to include more specifically two or three, and more specifically three.

[0049] On the other hand, when the laminate includes two or more pairs of tapes 120, 130, and 140, the distance d between each pair of tapes 120, 130, and 140 may be such that they are attached to the outside of the laminate 110 at intervals of 1 to 4 times the thickness t of the laminate 110.

[0050] More specifically, the pairs of tapes 120, 130, and 140 may be attached to the outside of the laminate 110 at intervals d that are two to three times the thickness t of the laminate 110.

[0051] If the tape is formed too finely outside the aforementioned range, the overall area enclosed by the tape increases, which can lead to problems such as poor gas discharge or increased uneven pressure distribution in one direction. Conversely, if the spacing is too large, the fixing strength of the laminate may decrease, which is undesirable.

[0052] Furthermore, in such cases, the two or more pairs of tapes 120, 30, and 140 may have a constant spacing between them, and more specifically, the areas separated by the two or more pairs of tapes 120, 30, and 140 on the upper surface of the laminate may be the same (S5=S6=S7=S8).

[0053] Furthermore, the width w' of the pair of tapes 120, 130, and 140 may be between 10 mm and 50 mm, more specifically between 10 mm and 40 mm, and even more specifically between 20 mm and 40 mm.

[0054] Here, the width w' can be based on the width of the non-overlapping portion of the pair of tapes 120, 130, and 140.

[0055] If the width falls outside the aforementioned range and is excessively thin, the fixing strength of the laminate decreases, and if it is excessively large, the area enclosed by the tape as a whole increases, which may hinder smooth gas discharge, and is therefore undesirable.

[0056] Similarly, the area enclosed by one or more pairs of tapes 120, 130, and 140 (S1+S2+S3) may be 10% to 40% of the total surface area of ​​the laminate, more specifically 10% to 30%, and more specifically 15% to 20%.

[0057] If the pair of tapes surround an excessively large area outside the aforementioned range, the overall area surrounded by the tapes increases, which can lead to problems such as poor gas discharge or increased uneven pressure distribution in one direction. Conversely, if the area surrounded is excessively small, it can reduce the fixing strength of the laminate, which is undesirable.

[0058] On the other hand, the two or more pairs of tapes relating to the present application may contain polyimide, and more specifically, may be polyimide tapes.

[0059] Polyimide (PI) is a polymeric material with thermal stability based on a rigid aromatic main chain, and possesses excellent mechanical strength, chemical resistance, throat resistance, and heat resistance based on the chemical stability of the imide ring. In addition, it also has excellent electrical properties such as insulating properties and a low dielectric constant.

[0060] In terms of heat resistance, polyimide can maintain high physical strength with minimal morphological deformation up to approximately 400°C, exceeding the heat resistance temperature range of 120°C to 180°C for commonly used separation membranes. Therefore, polyimide tapes, which use polyimide as the main material, can effectively control the morphological deformation of the laminate even under high-temperature conditions.

[0061] More specifically, the pair of tapes may be adhesive tapes comprising a functional layer containing polyimide and an adhesive layer containing an adhesive substance on one surface of the functional layer. Since the pair of tapes are adhered to the surface of the laminate by the adhesive layer, it is possible to prevent the pair of tapes from detaching from the laminate.

[0062] On the other hand, the laminate may be of the stacked type, stack-folding type, or stack-lamination type, and more specifically, it may be of the stacked type or stack-lamination type.

[0063] The stacked laminate is manufactured in a form in which positive and negative electrodes are stacked alternately, with a separation membrane interposed between the positive and negative electrodes.

[0064] The aforementioned stack-folding laminate is manufactured by arranging unit cells, each in which one or more negative electrodes and positive electrodes are stacked with a separation membrane in between, on a separation film, and then winding the film.

[0065] Finally, stack-lamination type laminates are stack-type laminates with additional lamination, resulting in more robust bonding between components. Furthermore, stack-lamination type laminates can be used to manufacture batteries with a desired capacity by, for example, producing unit cells as described for stack-folding type laminates, and then stacking multiple unit cells to improve the efficiency of the lamination process. The stacking order and number of unit cell electrode layers, as well as the stacking order and number of multiple unit cells, can be appropriately adjusted depending on the type, capacity, and application of the battery.

[0066] Furthermore, according to yet another embodiment of the present invention, a secondary battery is provided which includes the electrode assembly, an electrolyte, and a battery case for housing the electrode assembly and the electrolyte.

[0067] In this instance, a specific description of the positive electrode, negative electrode, separator membrane, and electrolyte included in the electrode assembly is similar to those known in the art and is therefore omitted herein.

[0068] The secondary battery may be a rectangular, cylindrical, or pouch-type secondary battery depending on the battery case, but more specifically, it may be a pouch-type secondary battery, depending on the type of laminate.

[0069] Furthermore, the secondary battery may be a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery, depending on the type of active material and electrolyte, and more specifically, it may be a lithium ion secondary battery.

[0070] To demonstrate the effects of the present invention, Figure 6 shows a pressure table measured by a pressure sensor to show that the pressurizing force acts uniformly over a large area on a secondary battery using an electrode assembly with the structure shown in Figure 4 (where the overlapping area of ​​the tape is approximately 10%).

[0071] Specifically, the manufactured rechargeable battery was charged at 1C under constant current / constant voltage (CC / CV) conditions at 25°C until it reached 4.35V / 38mA, followed by an activation process in which it was discharged at 2C under constant current (CC) conditions until it reached 2.5V. The pressure applied to the rechargeable battery during the activation process was confirmed at different locations using an electronic pressure sensor (Kitronic Corporation), and the pressure index value was numerically expressed based on the center of the rechargeable battery.

[0072] Referring to Figure 6, it can be seen that because the overlapping area of ​​the tape is very small, the pressure is distributed more evenly over a wider area than before, and the area where the pressure index value reaches its highest point (255) is clearly reduced.

[0073] Therefore, it is expected that the pressure non-uniformity in medium and large batteries will be reduced, thereby playing a role in enabling smooth gas discharge overall.

[0074] Anyone with ordinary skill in the art to which this invention belongs can make various applications and modifications within the scope of this invention based on the above-described content. [Industrial applicability]

[0075] As explained above, according to the present invention, by minimizing the area in which one or more pairs of tapes fixing the outside of the laminate overlap each other, it is possible to reduce the area in which the pressure is increased compared to the area in which no tape is formed and the area in which the pressure is increased compared to the non-overlapping portion of one or more pairs of tapes. Therefore, since the non-uniformity of the pressure can be reduced, the gas discharge generated in the activation process can be made smoother, which has the effect of improving safety.

Claims

1. The laminate includes a positive electrode, a negative electrode, and a separation membrane interposed between the positive and negative electrodes, and one or more pairs of tapes that secure the outside of the laminate. The pair of tapes includes non-overlapping portions that do not overlap each other and overlapping portions that overlap each other. An electrode assembly in which the width of the non-overlapping portion is greater than the width of the overlapping portion.

2. The electrode assembly according to claim 1, wherein the pair of tapes is composed of two or more unit tapes, and each unit tape includes a central portion and a tapered portion having a tapered structure in which the width decreases from the central portion toward both ends.

3. The electrode assembly according to claim 2, wherein the width of the tapered portion gradually decreases toward both ends.

4. The electrode assembly according to claim 2, wherein the tapered portion has a triangular, trapezoidal, or semicircular shape.

5. The electrode assembly according to claim 1, wherein the total area of ​​the overlapping portion is 1% to 20% of the total area surrounded by the pair of tapes.

6. The electrode assembly according to claim 1, wherein the pair of tapes is composed of two unit tapes.

7. The electrode assembly according to claim 1, wherein the superimposed portion is located on the upper surface, the lower surface, or both the upper and lower surfaces, with reference to the stacking direction of the laminate.

8. The electrode assembly according to claim 1, wherein the pair of tapes comprises two or more, and the two or more pairs of tapes are attached to the outside of the laminate at intervals of one to four times the thickness of the laminate.

9. The electrode assembly according to claim 8, wherein the two or more pairs of tapes are spaced at a constant distance from each other.

10. The electrode assembly according to claim 8, wherein the upper surface of the laminate is divided by the two or more pairs of tapes, and the respective areas are the same.

11. The electrode assembly according to claim 1, wherein the width of the pair of tapes is 10 mm to 50 mm.

12. The electrode assembly according to claim 1, wherein the total area surrounded by the one or more pairs of tapes is 10% to 40% of the total surface area of ​​the laminate.

13. The electrode assembly according to claim 1, wherein the pair of tapes comprises polyimide.

14. A secondary battery comprising an electrode assembly according to any one of claims 1 to 13, an electrolyte, and a battery case for housing the electrode assembly and the electrolyte.

15. The secondary battery according to claim 14, wherein the secondary battery is a pouch-type secondary battery.

Images