Stacked electrode assembly with improved cell capacity

Abstract

This specification discloses an electrode assembly including a stacked electrode assembly having a plurality of positive electrode tabs and a plurality of negative electrode tabs formed on both ends in a width direction, and a positive electrode current collector and a negative electrode current collector to which the plurality of positive electrode tabs and the plurality of negative electrode tabs are electrically connected, respectively, and ends of the positive electrode tabs and the negative electrode tabs are individually bonded to the positive electrode current collector and the negative electrode current collector, respectively.

Description

Technical Field

[0001] The present invention relates to a stacked electrode assembly, and more particularly to a technique for improving the substantial capacity of a stacked electrode assembly by shortening the length of a foil tab of the stacked electrode assembly and reducing the area occupied by a non-patterned portion.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0100270 filed on August 11, 2022, and all the contents disclosed in the literature of the Korean patent application are incorporated herein by reference.

Background Art

[0003] Unlike primary batteries, secondary batteries can be recharged and have been extensively studied and developed in recent years due to their potential for miniaturization and high capacity. With the increasing technological development and demand for mobile devices, as well as the emergence of electric vehicles and energy storage systems in response to the contemporary requirement for environmental protection, the demand for secondary batteries as an energy source has been increasing even more rapidly.

[0004] Secondary batteries can be classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries according to the shape of the battery case. The electrode assembly mounted inside the battery case in a secondary battery is a power generation element capable of charge and discharge, which has a laminated structure of electrodes and a separator.

[0005] The electrode assembly can be roughly classified into a Jellyroll type in which a separator is interposed between sheet-like positive and negative electrodes coated with an active material and wound, a stacked type in which a number of positive and negative electrodes are sequentially laminated with a separator interposed therebetween, and a Stack&Folding type in which unit cells of the stacked type are wound with a long separation film.

[0006] Among these various types of electrode assemblies, a stacked electrode assembly is constructed by stacking multiple unit cells, each with a separator membrane between the positive and negative electrodes, and each unit cell is equipped with its own foil tab. The foil tabs include a positive electrode tab and a negative electrode tab, and are formed by a punching process on the blank areas of the positive and negative electrodes where no active material is applied. The foil tabs serve as the entry and exit points for electrical connection to the electrode assembly, and multiple foil tabs are welded to a current collector and bundled together.

[0007] However, as the capacity of secondary batteries increases, the number of unit cells stacked in the stacked electrode assembly increases, and the number of foil tabs also increases as the number of stacked unit cells increases. The more foil tabs there are, the more difficult it becomes to weld them to the current collector, so the length of the foil tabs is increased to facilitate the welding process.

[0008] An increase in the length of the foil tab means an increase in the width of the blank area at both the positive and negative electrodes. The larger the blank area without active material, the lower the effective capacity compared to an electrode assembly of the same size. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Published Patent No. 2001-256954 [Overview of the project] [Problems that the invention aims to solve]

[0010] The purpose of this invention is to provide a method for effectively welding a large number of wheel tabs to a current collector without increasing the length of the wheel tabs, in line with the trend towards larger and medium-sized capacities of secondary batteries.

[0011] However, the technical problems that the present invention aims to solve are not limited to those described above, and other problems not mentioned can be clearly understood by an ordinary person of the art from the description of the invention below. [Means for solving the problem]

[0012] The present invention provides an electrode assembly comprising a stack-type electrode assembly having a plurality of positive electrode tabs and a plurality of negative electrode tabs formed at both ends in the width direction, and a positive electrode current collector and a negative electrode current collector to which the plurality of positive electrode tabs and the plurality of negative electrode tabs are electrically connected, the ends of the positive electrode tabs and the negative electrode tabs are individually joined to the positive electrode current collector and the negative electrode current collector, respectively.

[0013] The positive electrode tab and the negative electrode tab each have a bent portion at their ends, and the bent portions of the positive electrode tab and the negative electrode tab are individually joined to the positive electrode current collector and the negative electrode current collector, respectively.

[0014] Here, the bent portions of the positive electrode tab and the negative electrode tab can be directly joined to the opposing surfaces of the positive electrode current collector and the negative electrode current collector.

[0015] In one embodiment of the present invention, the positive electrode tab and the negative electrode tab may be formed in a single row at the same height relative to the stacked electrode assembly.

[0016] In another embodiment of the present invention, the positive electrode tab and the negative electrode tab may form a plurality of tab groups, each formed in a row at different heights relative to the stacked electrode assembly.

[0017] For example, the above-mentioned multiple tab groups may consist of one tab group each formed by the positive and negative electrode tabs of adjacent unit cells.

[0018] Furthermore, the positive electrode current collector and the negative electrode current collector may each comprise a number of branch current collectors corresponding to the number of tab groups.

[0019] The above-mentioned branch current collectors may have different heights from each other according to the height of the corresponding tab group, and may be arranged side by side along the height direction of the electrode assembly.

[0020] Alternatively, the plurality of tab groups may each form one tab group by height, with the positive electrode tabs and negative electrode tabs arranged in a zigzag pattern with different heights with respect to the stacked electrode assembly.

[0021] Here, the zigzag arrangement of the positive electrode tabs and the negative electrode tabs may be alternately performed for each one or more unit cells along the stacking direction of the unit cells.

[0022] Further, the positive electrode current collector and the negative electrode current collector may each include a number of branch current collectors corresponding to the plurality of tab groups. The branch current collectors may have different heights from each other according to the height of the corresponding tab group, and may be arranged side by side along the thickness direction of the stacked electrode assembly.

[0023] On the other hand, the present invention can provide a rectangular secondary battery including a case in which at least one surface forms an open surface, the electrode assembly housed inside the case through the open surface of the case, a cap plate coupled to seal the open surface of the case and including a positive electrode terminal and a negative electrode terminal electrically connected to the positive electrode current collector and the negative electrode current collector of the electrode assembly, respectively, and an electrolytic solution filled in the case.

Advantages of the Invention

[0024] In the stacked electrode assembly of the present invention having the above-described configuration, each positive electrode tab and negative electrode tab is individually joined to the positive electrode current collector and the negative electrode current collector, so that the problem of the lengthening of the foil tabs caused by temporarily welding a plurality of foil tabs and then welding them again to the current collector as in the prior art is solved. Of course, the effect of improving the current-carrying performance with respect to the stacked electrode assembly can be obtained.

[0025] In addition, the stacked electrode assembly according to the present invention is provided with bent portions at respective ends of a positive electrode tab and a negative electrode tab, and the bent portions of the positive electrode tab and the negative electrode tab are individually joined to a positive electrode current collector and a negative electrode current collector. Thereby, a sufficient welding area can be secured at the end of the foil tab via the bent portion, so that the problem of short circuit between the foil tab and the current collector due to insufficient welding strength can be prevented.

[0026] However, the technical effects obtainable by the present invention are not limited to the above-described effects, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the invention described below.

[0027] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention to be described later. Therefore, the present invention should not be construed as being limited only to the matters described in such drawings.

Brief Description of the Drawings

[0028] [Figure 1] This is a drawing illustrating a stacked electrode assembly constituting an electrode assembly of the present invention. [Figure 2] This is a drawing illustrating a structure in which a current collector is coupled to the stacked electrode assembly of FIG. 1. [Figure 3] This is a drawing illustrating a cross section in which a current collector is joined to the stacked electrode assembly of FIG. 1. [Figure 4] This is a drawing illustrating a stacked electrode assembly and a current collector according to another embodiment of the present invention. [Figure 5] This is a drawing illustrating a stacked electrode assembly and a current collector according to another embodiment of the present invention. [Figure 6] This is a drawing illustrating an example of a square secondary battery including an electrode assembly according to the present invention.

Modes for Carrying Out the Invention

[0029] The present invention can be modified in various ways and may have a variety of embodiments; therefore, specific embodiments are described in detail below.

[0030] However, this is not intended to limit the present invention to any particular embodiment, but rather should be understood to include all modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

[0031] In the present invention, terms such as "includes" and "have" are intended to specify the presence of features, numbers, stages, operations, components, parts, or combinations thereof as described in the specification, and do not preemptively exclude the presence or possibility of adding one or more other features, numbers, stages, operations, components, parts, or combinations thereof.

[0032] Furthermore, in this invention, when a part such as a layer, film, region, or plate is described as being "on top" of another part, this includes not only the case where it is "directly on top" of the other part, but also the case where another part is located in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is located in between. Also, in this application, being "on top" may include being located not only at the top but also at the bottom.

[0033] The present invention provides a stacked electrode assembly and an electrode assembly including a positive electrode current collector and a negative electrode current collector.

[0034] The stacked electrode assembly consists of multiple unit cells stacked in a stack structure, with a separator membrane interposed between the positive and negative electrodes. Multiple positive electrode tabs and multiple negative electrode tabs are formed at both ends in the width direction. In other words, the positive electrode tabs and negative electrode tabs are arranged separately from each other according to their polarity on both sides of the stacked electrode assembly.

[0035] The positive electrode current collector and the negative electrode current collector are conductive material components to which multiple positive electrode tabs and multiple negative electrode tabs are electrically connected, respectively. By connecting both multiple positive electrode tabs and multiple negative electrode tabs to the positive electrode current collector and the negative electrode current collector, the stacked electrode assembly can be housed in the case of a rectangular secondary battery, and the wiring work of connecting it to the positive and negative electrode terminals becomes easier.

[0036] In this invention, the ends of the positive electrode tab and the negative electrode tab are individually joined to the positive electrode current collector and the negative electrode current collector, respectively. By independently joining each positive electrode tab and the negative electrode tab to the positive electrode current collector and the negative electrode current collector, the problem of the wheel tabs becoming longer due to the conventional method of tack welding multiple wheel tabs (positive electrode tabs and negative electrode tabs) to the current collector is solved. Furthermore, it is possible to improve the current carrying performance of the stacked electrode assembly, such as increasing the rated current and decreasing the resistance.

[0037] Furthermore, in this invention, the positive electrode tab and the negative electrode tab are each provided with a bent portion, and the bent portions of the positive electrode tab and the negative electrode tab are individually joined to the positive electrode current collector and the negative electrode current collector, respectively. A sufficient welding area can be secured at the end of the wheel tab via the bent portion, thereby preventing the problem of the wheel tab short-circuiting at the current collector due to insufficient welding strength.

[0038] Specific embodiments of the electrode assembly according to the present invention will be described in detail below with reference to the attached drawings. For reference, the forward / backward and up / down / left / right directions used in the following description to specify relative positions are for the purpose of aiding the understanding of the invention, and unless otherwise defined, the directions shown in the drawings are used as the reference.

[0039] (First Embodiment) Figure 1 is a diagram illustrating a stack-type electrode assembly 1100 that constitutes the electrode assembly 1000 of the present invention.

[0040] The stacked electrode assembly 1100 is constructed by sequentially stacking multiple unit cells, each with a separator membrane interposed between the positive and negative electrodes, along one direction (thickness direction), with multiple positive electrode tabs 1132 and multiple negative electrode tabs 1134 formed at both ends in the width direction W.

[0041] The positive electrode tab 1132 and the negative electrode tab 1134 together are called the foil tab 1130. The positive electrode tab 1132 and the negative electrode tab 1134 are formed by performing a punching process on the blank portion 1120, where no active material is applied, at the positive and negative electrodes, respectively. In other words, the illustrated stack-type electrode assembly 1100 has a surfaced portion 1110 with active material applied in the center, and blank portions 1120 are arranged on both sides of the surfaced portion 1110. As a result, the positive electrode tab 1132 and the negative electrode tab 1134, which are punched out from the blank portion 1120, are separated by polarity and arranged separately on both sides of the stack-type electrode assembly 1100.

[0042] Figure 2 is a diagram illustrating the structure in which the current collector 1200 is connected to the stacked electrode assembly 1100 of Figure 1, and Figure 3 is a diagram illustrating a cross-section of the stacked electrode assembly 1100 with the current collector 1200 connected. Referring to Figures 2 and 3, the ends of the positive electrode tab 1132 and the negative electrode tab 1134 are individually connected to the positive electrode current collector 1210 and the negative electrode current collector 1220, respectively.

[0043] Conventionally, multiple foil tabs 1130 (positive electrode tabs and negative electrode tabs) provided on the stacked electrode assembly 1100 were tack-welded to structurally and electrically interconnected, and then re-welded to the current collector 1200. As a result, the foil tabs 1130 had to be sufficiently long as the distance from the stacked electrode assembly 1100 to the current collector 1200 increased.

[0044] In contrast, in the electrode assembly 1000 of the present invention, the distance from the stacked electrode assembly 1100 to the current collector 1200 is minimized because each positive electrode tab 1132 and negative electrode tab 1134 is independently joined to the positive electrode current collector 1210 and the negative electrode current collector 1220. As a result, the shorter the length of the foil tab 1130, which is processed from the blank portion 1120 without active material, the greater the effective capacity relative to a stacked electrode assembly 1100 of the same size. Furthermore, since each foil tab 1130 is directly welded to the current collector 1200, a sufficient current-carrying area can be secured to handle high current loads, thus improving current-carrying performance such as an increase in rated current and a decrease in resistance.

[0045] Furthermore, referring to Figures 1 to 3, the positive electrode tab 1132 and the negative electrode tab 1134 each have a bent portion 1140 at their ends, and the bent portions 1140 of the positive electrode tab 1132 and the negative electrode tab 1134 are individually joined to the positive electrode current collector 1210 and the negative electrode current collector 1220, respectively. In addition, the bent portions 1140 of the positive electrode tab 1132 and the negative electrode tab 1134 can be directly joined to the opposing surfaces of the positive electrode current collector 1210 and the negative electrode current collector 1220 without a separate current-carrying medium.

[0046] In this way, by forming bent portions 1140 at the ends of the positive electrode tab 1132 and the negative electrode tab 1134, a sufficient welding area can be secured at the end of the wheel tab 1130, thereby effectively preventing the problem of insufficient welding strength causing the wheel tab 1130 to short-circuit with the current collector 1200.

[0047] In the first embodiment of the present invention, the positive electrode tab 1132 and the negative electrode tab 1134 may be formed in a line at the same height relative to the stacked electrode assembly 1100. Correspondingly, the positive electrode current collector 1210 and the negative electrode current collector 1220 will have a width that is approximately equivalent to the thickness of the stacked electrode assembly 1100, and the respective bent portions 1140 of the positive electrode tab 1132 and the negative electrode tab 1134 will be welded in a line to the positive electrode current collector 1210 and the negative electrode current collector 1220, respectively.

[0048] (Second Embodiment) Figures 4 and 5 illustrate a stacked electrode assembly 1100 and a current collector 1200 according to a second embodiment of the present invention. The second embodiment of the present invention is characterized in that the positive electrode tab 1132 and the negative electrode tab 1134 form a plurality of tab groups 1150, each formed in a row at different heights relative to the stacked electrode assembly 1100. In other words, in the first embodiment described above, the positive electrode tab 1132 and the negative electrode tab 1134 form a single tab group 1150 formed in a row at the same height relative to the stacked electrode assembly 1100, whereas in the second embodiment, the positive electrode tab 1132 and the negative electrode tab 1134 are divided into a plurality of tab groups 1150 with varying heights.

[0049] In the first embodiment, in which multiple positive electrode tabs 1132 and negative electrode tabs 1134 are welded in a line to the current collector 1200, if the number of stacked unit cells increases and the thickness of the stacked electrode assembly 1100 increases, it may occur that the number of foil tabs 1130 that can be welded to the current collector 1200 is exceeded. Here, the number of foil tabs 1130 that can be welded to the current collector 1200 can be understood not only as the limit of foil tabs 1130 that are physically impossible to weld, but also as encompassing cases where there are practical difficulties in the welding work, such as when the welding space is narrow and welding is difficult, or when it is difficult to obtain uniform welding quality.

[0050] A second embodiment of the present invention is provided to improve various aspects of welding quality and welding control by dividing a plurality of positive electrode tabs 1132 and negative electrode tabs 1134 into a plurality of tab groups 1150. The second embodiment can be further divided into the specific embodiments shown in Figures 4 and 5 in terms of the arrangement or structure of the tab groups 1150. Here, the second embodiment shown in the drawings takes the example of forming two tab groups 1150, but it is of course possible to further subdivide the tab groups 1150 into three or more.

[0051] The second embodiment shown in Figure 4 illustrates a case where the positive electrode tab 1132 and negative electrode tab 1134 of adjacent unit cells each form a tab group 1150. In other words, a tab group 1150 consists of foil tabs 1130 of adjacent unit cells.

[0052] Accordingly, the positive electrode current collector 1210 and the negative electrode current collector 1220 may each have a number of branch current collectors 1230 corresponding to the number of tab groups 1150. A branch current collector 1230 refers to a partial current collector that branches off from a single current collector acting as a stem, and each branch current collector 1230 has a different length corresponding to the vertical arrangement of the tab groups 1150, and is arranged in a line along the height direction H of the stacked electrode assembly 1100. The branched branch current collectors 1230 make welding work to each tab group 1150 easier.

[0053] In the second embodiment shown in Figure 5, positive electrode tabs 1132 and negative electrode tabs 1134 are arranged in a zigzag pattern with varying heights relative to the stacked electrode assembly 1100, each forming one tab group 1150 based on height. That is, positive electrode tabs 1132 and negative electrode tabs 1134 of the same height form one tab group 1150 while skipping a certain number of unit cells. In Figure 5, the positive electrode tabs 1132 and negative electrode tabs 1134 are arranged in a zigzag pattern along the stacking direction of the unit cells, skipping one unit cell at a time.

[0054] In the embodiment shown in Figure 5, in one tab group 1150, the distance between the positive electrode tabs 1132 and the negative electrode tabs 1134 is wider than the spacing of the skipped unit cells. A wider distance between electrode tabs provides more welding space on the current collector 1200, which is advantageous for maintaining and improving welding quality.

[0055] The positive electrode current collector 1210 and the negative electrode current collector 1220 each have a number of branch current collectors 1230 corresponding to the number of tab groups 1150. In the embodiment shown in Figure 5, the branch current collectors 1230 are arranged along the thickness direction T of the stacked electrode assembly 1100, each having a different height depending on the height of the corresponding tab group 1150. This is because, since the width of each tab group 1150 with different heights is approximately the same as the thickness of the stacked electrode assembly 1100, it is advantageous from a design perspective to arrange the branch current collectors 1230 in a staggered and bent form.

[0056] On the other hand, the present invention may provide a prismatic secondary battery 10 including an electrode assembly 1000 according to the first or second embodiment, and an example of such a prismatic secondary battery 10 is shown in Figure 6.

[0057] Referring to Figure 6, the prismatic secondary battery 10 includes a case 100 on which at least one side forms an open surface, and the stacked electrode assembly 1100 and electrode assembly 1000 described above are housed inside the case 100 through the open surface of the case 100. The cap plate 200, which is coupled to seal the open surface of the case 100, has electrode terminals 210 with opposite polarities for the positive electrode terminal 212 and the negative electrode terminal 214, and the positive electrode current collector 1210 and the negative electrode current collector 1220 of the electrode assembly 1000 are electrically connected to the positive electrode terminal 212 and the negative electrode terminal 214 of the cap plate 200, respectively. The case 100 is filled with an electrolyte 300 that serves as a medium for ion conduction between the positive electrode and the negative electrode.

[0058] The rectangular secondary battery 10 shown in Figure 6 is suitable for the recent trend towards higher capacity secondary batteries because it includes an electrode assembly 1000 in which the effective capacity is improved by shortening the length of the foil tab 1130.

[0059] The present invention has been described in more detail above with reference to the drawings and embodiments. However, the configurations described in the drawings or embodiments described herein are merely one embodiment of the present invention and do not represent the entire technical concept of the present invention. It should be understood that there are various equivalents and modifications that can substitute for them at the time of filing this application. [Explanation of symbols]

[0060] 10: Rectangular rechargeable battery 100: Case 200: Cap plate 210: Electrode terminal 212: Positive terminal 214: Negative terminal 300: Electrolyte 1000: Electrode Assembly 1100: Stacked electrode assembly 1110:Landed section 1120: Plain section 1130: Foil Tab 1132: Positive Tab 1134: Negative electrode tab 1140: Bend part 1150: Tab Group 1200: Current collector 1210: Positive electrode current collector 1220: Negative electrode current collector 1230: Branch current collector W: width direction H: Height direction T: thickness direction

Claims

1. A stack-type electrode assembly having multiple positive electrode tabs and multiple negative electrode tabs formed only on the upper part at both ends in the width direction, A positive electrode current collector and a negative electrode current collector, each electrically connected to the plurality of positive electrode tabs and the plurality of negative electrode tabs, Includes, The ends of the positive electrode tab and the negative electrode tab are individually joined to the positive electrode current collector and the negative electrode current collector, respectively. The positive electrode tab and the negative electrode tab each have a bent portion at their ends. The aforementioned bent portion is bent in the same direction, An electrode assembly comprising a positive electrode current collector configured to cover a portion of the upper surface and the upper part at one end in the width direction of the stacked electrode assembly, and a negative electrode current collector configured to cover a portion of the upper surface and the upper part at the other end in the width direction of the stacked electrode assembly.

2. The electrode assembly according to claim 1, wherein the bent portions of the positive electrode tab and the negative electrode tab are individually joined to the positive electrode current collector and the negative electrode current collector, respectively.

3. The electrode assembly according to claim 2, wherein the bent portions of the positive electrode tab and the negative electrode tab are directly joined to the opposing surfaces of the positive electrode current collector and the negative electrode current collector.

4. The positive electrode tab and the negative electrode tab are The electrode assembly according to claim 2, which is formed in a single row at the same height relative to the stacked electrode assembly.

5. A stack-type electrode assembly having multiple positive electrode tabs and multiple negative electrode tabs formed at both ends in the width direction, A positive electrode current collector and a negative electrode current collector, each electrically connected to the plurality of positive electrode tabs and the plurality of negative electrode tabs, Includes, The ends of the positive electrode tab and the negative electrode tab are individually joined to the positive electrode current collector and the negative electrode current collector, respectively. The positive electrode tab and the negative electrode tab each have a bent portion at their ends. The positive electrode tab and the negative electrode tab are An electrode assembly comprising a plurality of tab groups formed in a single row at different heights relative to the aforementioned stacked electrode assembly.

6. The aforementioned multiple tab groups are The electrode assembly according to claim 5, wherein the positive electrode tab and negative electrode tab of adjacent unit cells each form one tab group.

7. The positive electrode current collector and the negative electrode current collector are The electrode assembly according to claim 6, comprising a number of branch current collectors corresponding to the plurality of tab groups.

8. The aforementioned branch current collector is The electrode assembly according to claim 7, having different heights from one another depending on the height of the corresponding tab group, and arranged side by side along the height direction of the stacked electrode assembly.

9. The aforementioned multiple tab groups are The electrode assembly according to claim 5, wherein positive electrode tabs and negative electrode tabs arranged in a zigzag pattern with varying heights relative to the stacked electrode assembly each form a tab group according to their respective heights.

10. The electrode assembly according to claim 9, wherein the zigzag arrangement of the positive electrode tabs and the negative electrode tabs is alternated for each of one or more unit cells along the stacking direction of the unit cells.

11. The positive electrode current collector and the negative electrode current collector are The electrode assembly according to claim 9, comprising a number of branch current collectors corresponding to the plurality of tab groups.

12. The aforementioned branch current collector is The electrode assembly according to claim 11, having different heights from one another depending on the height of the corresponding tab group, and arranged side by side along the thickness direction of the stacked electrode assembly.

13. Cases in which at least one side forms an open surface, An electrode assembly according to any one of claims 1 to 12, which is housed inside the case through the open surface of the case, A cap plate having positive and negative terminals which are coupled to the open surface of the case to seal it and electrically connected to the positive and negative current collectors of the electrode assembly, respectively, The electrolyte solution filled inside the case, A rectangular rechargeable battery, including one.

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