Stack and folding type electrode assembly to which a thickness compensating part is applied, method for manufacturing the same, and secondary battery including the same

Abstract

According to one embodiment of the present invention, An electrode assembly having a structure in which a plurality of unit cells are wound with a separation film, The electrode assembly includes a first unit cell and a second unit cell located at outermost sides of the electrode assembly, the unit cell includes at least one selected from the group consisting of a positive electrode and a negative electrode, and a separator, the positive electrode and the negative electrode each have a flat portion where the thickness of an active material layer is constant and a sloped portion where the thickness of the active material layer decreases in a protruding direction of the tab, and a first thickness complement portion and a second thickness complement portion that compensate for a thickness difference between the flat portion and the sloped portion are formed between the first unit cell and an outermost separator film facing the first unit cell, and between the second unit cell and an outermost separator film facing the second unit cell, respectively.

Description

Technical Field

[0001] [Cross - reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2022 - 0136433 filed on October 21, 2022 and Korean Patent Application No. 10 - 2023 - 0127848 filed on September 25, 2023, 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 a stack - and - fold type electrode assembly to which a thickness compensating part is applied, a method for manufacturing the same, and a secondary battery including the same.

Background Art

[0003] As the technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source has been rapidly increasing. In particular, secondary batteries have attracted much attention not only as an energy source for mobile devices such as mobile phones, digital cameras, notebook computers, and wearable devices, but also as an energy source for power devices such as electric bicycles, electric vehicles, and hybrid electric vehicles.

[0004] Secondary batteries are classified according to the shape of the battery case into cylindrical batteries in which the electrode assembly is built into a cylindrical metal can, prismatic batteries in which the electrode assembly is built into a rectangular metal can, and pouch - type batteries in which the electrode assembly is built into a pouch - type case made of an aluminum laminate sheet.

[0005] On the one hand, the electrode assembly built into the battery case is a power generation element capable of charge and discharge, consisting of a laminated structure of a positive electrode, a separator, and a negative electrode, and is classified into a jelly roll type, a stack type, and a stack / folding type. The jelly roll type is a form in which a separator is wound between a long sheet-type positive electrode and a negative electrode coated with an active material, the stack type is a form in which a plurality of positive electrodes and negative electrodes of a predetermined size are sequentially laminated with a separator interposed therebetween, and the stack and folding type is a composite structure of the jelly roll type and the stack type, in which unit cells are arranged on a separation film and these are wound up.

[0006] Recently, the development of secondary batteries in which a stack and folding electrode assembly is built into a pouch-type case has been active.

[0007] The positive electrode and the negative electrode used for manufacturing such an electrode assembly are each manufactured by mixing materials such as an active material, a conductive material, and a binder with a solvent to produce a slurry, and applying this to a current collector. In such a case, since the slurry is a viscous liquid substance, it will flow on the current collector, and a sliding phenomenon in which the thickness becomes thinner in the flowing part appears.

[0008] Such a sliding phenomenon occurs at the interface between the coated portion where the slurry is applied and the uncoated portion where the slurry is not applied, and this generally occurs at the upper end of the pouch cell.

[0009] However, due to the sliding phenomenon, the thickness of the thin part weakens the adhesive force between the electrode and the separator or does not adhere at all, so the distance between the positive electrode-separator-negative electrode increases, thereby increasing the resistance and promoting side reactions. Therefore, ultimately, such problems result in a decrease in battery performance.

[0010] Therefore, recently, in order to solve the above problems, a roller tilting method of twisting the rolling roller so as to be rolled as a whole, a sub-roller method of pressing the upper end once again through an additional roller, a JF taping method of attaching a tape to the separator paper at the jig forming stage so that the upper end of the cell receives a pressure similar to that of the central part of the cell, etc. have been developed.

[0011] However, the roller tilting method can improve the adhesion at the upper end, but there is a problem that the adhesion at the lower end may be weakened or the possibility of non-adhesion increases. The sub-roller method is difficult to finely adjust, there is no guide regarding the optimal conditions, and there is a side effect problem due to excessive pressing. In the JF taping method, when a tolerance occurs in the cell position in the jig forming equipment, a pressure difference may occur, which may induce a performance deviation between cells.

[0012] Therefore, it is an actual situation that there is a need to develop a secondary battery technology that improves the adhesion between the upper end of the electrode and the separator film to solve the above problems without causing additional problems.

Summary of the Invention

Problems to be Solved by the Invention

[0013] An object of the present invention is to improve the adhesion between the upper end of the electrode and the separator film by complementing the thickness of the inclined portion where the thickness of the active material layer formed by sliding during the manufacturing process of the electrode becomes thin, thereby preventing an increase in resistance and side reactions, and providing an electrode assembly and a secondary battery capable of improving the life characteristics.

[0014] Another object is to provide an electrode assembly and a secondary battery capable of preventing the problem of weakening of the adhesion due to electrolyte wetting of the components of the electrode assembly.

[0015] Furthermore, while exhibiting the above-described effects, the present invention provides an electrode assembly that does not have a problem of deviation in battery performance due to a difference in the degree of improvement between batteries, and does not have a problem of weakening of the adhesive force at the lower end or problems caused by excessive pressing, and a method for manufacturing the same.

[0016] The problems to be solved by the present invention are not limited to the above-described problems, and the problems not mentioned should be clearly understood by those having ordinary knowledge in the technical field to which the present invention pertains from the present specification and the accompanying drawings.

Means for Solving the Problems

[0017] An electrode assembly according to an embodiment of the present invention is an electrode assembly having a structure in which a plurality of unit cells are wound by a separation film, the electrode assembly includes a first unit cell and a second unit cell located in the outermost shells on both sides, the unit cell (first unit cell, second unit cell) includes one or more selected from the group consisting of a positive electrode and a negative electrode, and a separation film, and the positive electrode and the negative electrode each have a flat portion with a constant thickness of the active material layer and an inclined portion in which the thickness of the active material layer decreases as going in the protruding direction of the tab, between the first unit cell and the outermost separation film facing the first unit cell, and between the second unit cell and the outermost separation film facing the second unit cell, a first thickness compensating portion and a second thickness compensating portion for compensating the thickness difference between the flat portion and the inclined portion are respectively formed.

[0018] Here, the first thickness compensating portion and the second thickness compensating portion may be formed so as to cover the inclined portion in the direction in which the tab protrudes from the positive electrode and the negative electrode.

[0019] At this time, it may be formed in a length corresponding to or longer than the upper end length of the outermost shell electrodes of the first unit cell and the second unit cell in a direction perpendicular to the direction in which the tab protrudes.

[0020] More specifically, the first thickness compensating part and the second thickness compensating part may include a cover part covering a part corresponding to the inclined part, and an extension part extending longer than the separation film in a direction in which tabs protrude from the positive electrode and the negative electrode and covering a part of the separation film and the tabs.

[0021] More specifically, the extension parts of the first thickness compensating part and the second thickness compensating part may further include an indented part indented inward from the separation film at a part where the tabs are located.

[0022] Furthermore, according to the present invention, in order to prevent weakening of the adhesive force between components due to electrolyte wetting, the first thickness compensating part and the second thickness compensating part may be directly adhered to each other. Specifically, they may be adhered to each other outside the separation film. Such first and second thickness compensating parts may be, for example, double-sided tapes for ease of manufacturing.

[0023] At this time, the double-sided tapes may each be acrylic tapes having acrylic adhesive layers formed on both sides of a base material.

[0024] On the other hand, the first unit cell and the second unit cell may each be a unit cell in a form in which a positive electrode is located at a part facing the first thickness compensating part and the second thickness compensating part.

[0025] According to still another embodiment of the present invention, a method for manufacturing the electrode assembly is provided.

[0026] The electrode assembly is manufactured by forming first and second thickness compensating parts at ends of positions where first and second unit cells, which will be located at the outermost shell of the electrode assembly in the separation film, are arranged, arranging a plurality of unit cells including the first and second unit cells such that upper ends of the first and second unit cells are located at parts where the first and second thickness compensating parts are formed, and then folding and rolling.

[0027] On the one hand, the unit cell (the first unit cell, the second unit cell) includes tabs protruding from the upper end of the unit cell, and the first thickness compensation part and the second thickness compensation part can specifically include two recessed parts respectively.

[0028] Here, the recessed parts of the first thickness compensation part and the second thickness compensation part are formed so as to face the end of the separation film, and the first unit cell and the second unit cell can be arranged so that the tabs of the first unit cell and the second unit cell are located in the recessed parts.

[0029] More specifically, the unit cell (the first unit cell, the second unit cell) includes one or more selected from the group consisting of a positive electrode and a negative electrode, and a separation film. The positive electrode and the negative electrode each have a flat part with a constant thickness of the active material layer, and an inclined part where the thickness of the active material layer decreases as going in the protruding direction of the tab. The upper ends of the first unit cell and the second unit cell may correspond to the inclined part.

[0030] On the one hand, the first thickness compensation part and the second thickness compensation part can be adhered to each other outside the separation film by the rolling.

[0031] Furthermore, the present invention also provides a secondary battery including the electrode assembly and an electrolyte.

Advantages of the Invention

[0032] According to the present invention, in the electrode assembly of the present invention, between the first unit cell and the second unit cell located in the outermost shells on both sides and the outermost separation film facing these, by forming the first thickness compensation part and the second thickness compensation part at the upper end parts of the unit cells where the inclined parts are formed respectively, the thickness is compensated for the inclined parts, and the adhesive force between the electrode and the separation film at the upper end parts is improved, thereby preventing an increase in resistance and side reactions, and improving the life characteristics.

[0033] Further, by directly adhering the first thickness compensation part and the second thickness compensation part in a direction facing each other, it is possible to prevent the adhesive force from being weakened due to electrolyte wetting of each component of the electrode assembly, and further improve the life characteristics.

[0034] Also, while exhibiting the above effects in a very simple manner without changing process equipment such as rolling rollers, since it can be applied uniformly to all electrode assemblies, there is no problem of occurrence of deviation in battery performance due to differences in the degree of improvement between batteries, and it is also possible to prevent problems such as weakening of the adhesive force at the lower end and problems caused by excessive pressing.

Brief Description of the Drawings

[0035]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0036] Hereinafter, with reference to the accompanying drawings, various embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. The present invention can be realized in various different forms and is not limited to the embodiments described here.

[0037] In order to clearly describe the present invention, parts that are unnecessary for the description are omitted, and the same reference numerals are used for the same or similar components throughout the specification.

[0038] In addition, the sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for the convenience of explanation, and thus the present invention is not necessarily limited to the places shown in the drawings. The thicknesses are enlarged to clearly represent the various layers and regions in the drawings. And in the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggeratedly shown.

[0039] Also, throughout the specification, when a certain part "includes" a certain component, this means that other components can be further included rather than excluding other components unless otherwise stated to the contrary.

[0040] Also, throughout the specification, when referring to "on a plane", this means when looking at the target part from above, and when referring to "in a cross-section", this means when looking at the cross-section obtained by vertically cutting the target part from the side.

[0041] An electrode assembly according to an embodiment of the present invention is an electrode assembly having a structure in which a plurality of unit cells are wound by a separation film, the electrode assembly includes a first unit cell and a second unit cell located in the outermost shells on both sides, the unit cell includes one or more selected from the group consisting of a positive electrode and a negative electrode, and a separation membrane, and the positive electrode and the negative electrode each have a flat part with a constant thickness of the active material layer and an inclined part in which the thickness of the active material layer decreases as going in the protruding direction of the tab, between the first unit cell and the outermost separation film facing the first unit cell, and between the second unit cell and the outermost separation film facing the second unit cell, a first thickness compensation part and a second thickness compensation part for compensating the thickness difference between the flat part and the inclined part are respectively formed.

[0042] And a method for manufacturing such an electrode assembly is A first thickness compensation part and a second thickness compensation part are formed at the ends of the positions where the first unit cell and the second unit cell, which will be located in the outermost shell of the electrode assembly in the separation film, are arranged. After arranging a plurality of unit cells including the first unit cell and the second unit cell such that the upper ends of the first unit cell and the second unit cell are located at the portions where the first thickness compensation part and the second thickness compensation part are formed, folding and rolling are performed.

[0043] The electrode assembly having such a structure and its manufacturing method will be described below with reference to the drawings.

[0044] FIG. 1 schematically shows a cross-sectional view of an electrode assembly according to an embodiment of the present invention cut in the protruding direction of the tabs, and FIG. 2 shows a schematic diagram showing a top view of the electrode assembly before winding.

[0045] First, referring to both FIGS. 1 and 2, the electrode assembly 1000 according to the present invention has a structure in which a plurality of unit cells 1100 are wound by a separation film 1200. At this time, the plurality of unit cells 1100 include the unit cell 1140 of the core part, the unit cell 1130 in the winding direction, and up to the first unit cell 1110 and the second unit cell 1120 located in the outermost shell of the electrode assembly 1000.

[0046] Also, between the first unit cell 1110 and the outermost separation film 1210 facing the first unit cell 1110, and between the second unit cell 1120 and the outermost separation film 1220 facing the second unit cell 1120, a first thickness compensation part 1310 and a second thickness compensation part 1320 are respectively formed at the ends in the direction in which the tabs 1111, 1112, 1121, and 1122 protrude.

[0047] Specifically, the first thickness compensation part 1310 is formed in a direction perpendicular to the direction in which the tabs 1111 and 1112 protrude, with a length l2 corresponding to the upper end length l1 of the first unit cell 1110, or a length longer than these. The second thickness compensation part 1320 is also formed in a direction perpendicular to the direction in which the tabs 1121 and 1122 protrude, with a length l4 corresponding to the upper end length l3 of the outermost shell electrode of the second unit cell 1120, or a length longer than these.

[0048] Therefore, the thickness compensation part 1300 does not interfere with the winding of the separation film 1200. That is, if the formation lengths l2 and l4 of the first thickness compensation part 1310 and the second thickness compensation part 1320 are shorter than the upper end lengths l1 and l3 of the outermost shell electrodes of the first unit cell 1110 and the second unit cell 1120, a part of the electrode may not be covered, and resistance may be concentrated in that part, or there may be a problem that the occurrence of side reactions deepens. However, if it is excessively long, the thickness compensation part may interfere during the folding process, or wrinkles may be generated in the folded part, resulting in weakening of the adhesive force, so it is preferably formed with a length within a range that does not affect adjacent unit cells. On the other hand, as described above, the present application is for solving the problems caused by insufficient adhesion between the electrode and the separation film at the end of the electrode due to the sliding phenomenon during electrode manufacturing.

[0049] Therefore, the first thickness compensation part 1310 and the second thickness compensation part 1320 can be formed to cover the electrode sliding phenomenon sites in the direction in which the tabs 1111, 1112, 1121, and 1122 protrude from the outermost unit cells (the first unit cell 1110 and the second unit cell 1120).

[0050] To explain this more specifically, FIG. 3 schematically shows an enlarged view of the part where the first unit cell 1110 of FIG. 1 is formed.

[0051] Referring to Fig. 3, the first unit cell 1110 has a structure including one negative electrode 1113, two positive electrodes 1114, and a separator 1115 interposed therebetween. The positive electrode 1114 located on the outermost shell has a flat portion 1114a with a constant thickness of the active material layer and an inclined portion 1114b where the thickness of the active material layer decreases as it goes in the protruding direction of the tabs 1111 and 1112.

[0052] Although not described with reference numerals, it goes without saying that the negative electrode can also have a structure including a flat portion and an inclined portion.

[0053] Since the distance from such an inclined portion 1114b to the separation film (the outermost separation film 1210) is farther than the distance from the flat portion 1114a to the outermost separation film 1210, if the same rolling is performed during the manufacturing process of the electrode assembly 1000, the adhesion is not well achieved. However, according to the present invention, the first thickness compensating portion 1310 is formed to cover the portion corresponding to the inclined portion 1114b of the positive electrode 1114 located on the outermost side, so that these distances can be reduced and the outermost separation film 1210 and the inclined portion 1114b of the positive electrode 1114 can be adhered with a pressure similar to that of the flat portion 1114a during rolling.

[0054] Therefore, according to the present invention, the pressure difference caused by rolling between the inclined portion 1114b and the flat portion 1114a can be reduced, and the effects of improving the adhesion force and the life performance as intended by the present application can be exerted.

[0055] In addition, in order to examine a more specific structure of the first thickness compensating portion 1310 and the second thickness compensating portion 1320 formed to cover the inclined portion 1114b, an enlarged view of the end portion where the first thickness compensating portion 1310 is formed is shown in Fig. 4.

[0056] Referring to FIG. 4, the first thickness compensating portion 1310 has a cover portion 1312 covering a portion corresponding to the inclined portion 1114b in the direction in which the tabs 1111 and 1112 project from the first unit cell 1110, and an extension portion 1311 extending longer than the separation film 1200 in the projecting direction of the tabs 1111 and 1112 and covering a part of the separation film 1200 and the tabs 1111 and 1112. The extension portion 1311 has a structure including an indented portion 1313 indented inward from the separation film 1200 at the portion where the tabs 1111 and 1112 are located.

[0057] That is, the first thickness compensating portion 1310 and the second thickness compensating portion 1320 can increase the overall adhesion force to the electrodes by means of the cover portion 1312 covering the upper end of the outermost shell electrode in the direction in which the tabs 1111, 1112, 1121, and 1122 project from the outermost unit cells (the first unit cell 1110 and the second unit cell 1120), despite the sliding phenomenon of the electrodes included in the unit cell 110.

[0058] Also, referring again to FIGS. 1 and 2 together, the first thickness compensating portion 1310 and the second thickness compensating portion 1320 can be structured such that the extension portions 1311 are adhered to each other outside the separation film 1200.

[0059] That is, according to the present invention, the first thickness compensating portion 1310 and the second thickness compensating portion 1320 include the extension portion 1311 covering a part of the separation film 1200 and the tabs 1111 and 1112, so that they are formed outside the separation film 1200. Thus, the outermost separation films 1210 and 1220 can be adhered to each other, and a stronger adhesion is achieved between the components of the electrode assembly. Then, even in the case of electrolyte wetting, the expansion of these intervals during the cycle can be minimized.

[0060] Thereby, the problems of increased resistance and side reactions in the projecting direction of the conventional tabs 1111, 1112, 1121, and 1122 can be solved.

[0061] Furthermore, by including the recessed portions 1313 in the first thickness compensation portion 1310 and the second thickness compensation portion 1320, the tabs 1111 and 1112 can also prevent interference with the tabs of other unit cells 1120, 1130, and 1140 during adhesion and welding to form an electrical connection. At the same time, the adhesion site of the thickness compensation portion 1300 can be maximally widened to maximize the adhesion force between the electrode and the separation membrane.

[0062] Although the first thickness compensation portion 1310 has been described with reference to FIG. 4, it goes without saying that the same also applies to the second thickness compensation portion 1320.

[0063] On the other hand, referring to FIG. 3 again, FIG. 3 shows a configuration in which the positive electrode is located on the outermost shell of the first unit cell 1110 and the positive electrode is located at a position facing the first thickness compensation portion 1310. However, the negative electrode may be arranged, and any case is included in the present invention. The same also applies to the second unit cell 1120 located on other outermost shells.

[0064] The unit cell 1100 also shows a bicell having a structure in which electrodes with the same polarity are arranged on both sides as an example of the first unit cell 1110. However, each of the unit cells 1100 is not limited, and it may be a full cell having a structure in which electrodes with different polarities are arranged on both sides, a bicell having a structure in which electrodes with the same polarity are arranged on both sides, or a monocell having a structure in which one electrode and a separation membrane are laminated.

[0065] Also, the type and material of the thickness compensation portion (the first thickness compensation portion 1310) are not limited, and generally applicable thickness compensation portions can be applied. In particular, tape materials used for secondary batteries can be more preferably used. For example, an acrylic tape having acrylic adhesive layers formed on both sides of a base material may be used. On the other hand, the manufacturing method of the electrode assembly 1000 according to an embodiment of the present invention will be described with reference to FIGS. 2 and 4 again.

[0066] Referring to FIG. 2, in the separation film 1200 of the electrode assembly 1000, the first thickness compensation part 1310 and the second thickness compensation part 1320 are formed at the ends of the positions where the first unit cell 1110 and the second unit cell 1120, which are located in the outermost shell of the electrode assembly 1000, are arranged. After arranging a plurality of unit cells 1100 including the first unit cell 1110 and the second unit cell 1120 such that the upper ends of the first unit cell 1110 and the second unit cell 1120 are located at the portions where the first thickness compensation part 1310 and the second thickness compensation part 1320 are formed, it is manufactured by a method of folding and rolling.

[0067] Specifically, referring to both FIG. 2 and FIG. 4, first, the recessed portions 1313 and 1323 formed in the first thickness compensation part 1310 and the second thickness compensation part 1320 are formed at the ends of the separation film 1200 at the positions where the first unit cell 1110 and the second unit cell 1120 are arranged so as to face the ends of the separation film 1200. Then, the first unit cell 1110 and the second unit cell 1120 are arranged such that the tabs 1111, 1112, 1121, and 1122 of the first unit cell 1110 and the second unit cell 1120 are located in the recessed portions 1313 and 1323.

[0068] Also, as described above, the unit cell 1100 includes one or more selected from the group consisting of a positive electrode and a negative electrode, and a separation membrane. The positive electrode and the negative electrode each have a flat part with a constant thickness of the active material layer and an inclined part where the thickness of the active material layer decreases as going in the protruding direction of the tab. Therefore, the upper ends of the first unit cell 1110 and the second unit cell 1120 located at the portions where the first thickness compensation part 1310 and the second thickness compensation part 1320 are formed correspond to the inclined parts.

[0069] At this time, the unit cells 1100 are arranged such that the positive electrode and the negative electrode are alternately laminated in the lamination direction after winding.

[0070] On the other hand, after arranging all the unit cells 1100 on the separation film 1200 as shown in FIG. 2, folding can be performed in one direction.

[0071] To clearly show the electrode assembly 1000 that has undergone such folding, FIG. 5 schematically shows a cross-sectional view of the electrode assembly 1000 cut in a direction perpendicular to the protruding directions of the tabs 1111, 1112, 1121, and 1122.

[0072] Referring to FIG. 5, the unit cells 1110, 1120, 1130, and 1140 are in a state of being wound in one direction by the separation film 1200, and the positive and negative electrodes are alternately arranged in the stacking direction.

[0073] Alternatively, after arranging the unit cells on the separation film, the electrode assembly can also be manufactured by alternately folding them in a zigzag manner.

[0074] To clearly show the electrode assembly 2000 that has undergone such folding, FIG. 6 schematically shows a cross-sectional view of the electrode assembly 2000 cut in a direction perpendicular to the protruding direction of the tab.

[0075] Referring to FIG. 6, the unit cell 2100 is in a state of being wound alternately in a zigzag manner by the separation film 2200, and the positive and negative electrodes are alternately arranged in the stacking direction.

[0076] At this time, FIGS. 5 and 6 show a configuration in which the positive electrodes are located in the outermost shells on both sides, but this is not limiting. The negative electrodes may be arranged in the outermost shells on both sides, or the positive electrode may be arranged in one outermost shell and the negative electrode may be arranged in the other outermost shell, which is of course also possible.

[0077] Returning again to FIGS. 2 and 1, when the folding is completed as described above, the electrode assembly 1000 is rolled.

[0078] By such rolling, the separation film 1200 and the unit cell 1100 are adhered and laminated to each other and firmly bonded, and the thickness is also complemented at the portion corresponding to the inclined portion, so that the adhesive force can be made similar as a whole.

[0079] Also, at this time, the first thickness compensation part 1310 and the second thickness compensation part 1320 can also be adhered to each other.

[0080] Thereby, the electrode assembly 1000 according to an embodiment of the present application is manufactured, and by applying the thickness compensation part 1300, problems such as an increase in resistance, acceleration of side reactions, and lithium plating in the protruding directions of the tabs 1111, 1112, 1121, and 1122 intended by the present application can be solved.

[0081] On the other hand, since the compositions, structures, etc. of the positive electrode, negative electrode, and separator membrane constituting other electrode assemblies are known in the art, detailed descriptions thereof are omitted in this specification.

[0082] On the other hand, the present invention provides a secondary battery including an electrode assembly and an electrolyte, and provides a battery module including the same.

[0083] Since such secondary batteries and battery modules are also known in the art, detailed descriptions thereof except for the above configurations are omitted in this specification.

[0084] As described above, the preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also belong to the scope of the present invention.

Explanation of Reference Numerals

[0085] 1000, 2000: Electrode assembly 1100, 2100: Unit cell 1110: First unit cell 1120: Second unit cell 1200, 2200: Separation film 1300: Thickness compensation part 1310: First thickness compensation part 1320: Second thickness compensation part

Claims

1. An electrode assembly having a structure in which a plurality of unit cells are wound by a separation film, wherein the electrode assembly includes a first unit cell and a second unit cell located in the outermost shells on both sides, the first unit cell and the second unit cell each include one or more selected from the group consisting of a positive electrode and a negative electrode, and a separation membrane, and the positive electrode and the negative electrode each have a flat portion with a constant thickness of the active material layer and an inclined portion in which the thickness of the active material layer decreases as going in the protruding direction of the tab, and between the first unit cell and the outermost separation film facing the first unit cell, and between the second unit cell and the outermost separation film facing the second unit cell, a first thickness compensation portion and a second thickness compensation portion for compensating the thickness difference between the flat portion and the inclined portion are respectively formed. An electrode assembly.

2. The electrode assembly according to claim 1, wherein the first thickness compensation portion and the second thickness compensation portion are formed to cover the inclined portion in the direction in which the tab protrudes from the positive electrode and the negative electrode.

3. The electrode assembly according to claim 2, wherein the first thickness compensation portion and the second thickness compensation portion are formed with a length corresponding to or longer than the upper end length of the outermost shell electrode of the first unit cell and the second unit cell in a direction perpendicular to the direction in which the tab protrudes.

4. The electrode assembly according to claim 2, wherein the first thickness compensation portion and the second thickness compensation portion include a cover portion covering a portion corresponding to the inclined portion and an extension portion extending longer than the separation film in the direction in which the tab protrudes from the positive electrode and the negative electrode to cover a part of the separation film and the tab.

5. The electrode assembly according to claim 4, wherein the extension portions of the first thickness compensation portion and the second thickness compensation portion include an indented portion indented inward from the separation film at the portion where the tab is located.

6. The electrode assembly according to claim 1, wherein the first thickness compensation portion and the second thickness compensation portion are directly adhered to each other.

7. The electrode assembly according to claim 1, wherein the first thickness compensation portion and the second thickness compensation portion are adhered to each other outside the separation film.

8. The electrode assembly according to claim 1, wherein the first thickness compensation portion and the second thickness compensation portion are each a double-sided tape.

9. The electrode assembly according to claim 8, wherein the double-sided tapes are acrylic tapes each having an acrylic adhesive layer formed on both sides of a base material.

10. The electrode assembly according to claim 1, wherein the first unit cell and the second unit cell are each in a form in which the positive electrode is located at a portion facing the first thickness compensating portion and the second thickness compensating portion.

11. A method for manufacturing an electrode assembly according to any one of claims 1 to 10, forming a first thickness compensating portion and a second thickness compensating portion at an end of a position where the first unit cell and the second unit cell, which will be located in the outermost shell of the electrode assembly, are arranged in the separation film, and arranging a plurality of unit cells including the first unit cell and the second unit cell such that the upper ends of the first unit cell and the second unit cell are located at a portion where the first thickness compensating portion and the second thickness compensating portion are formed, and then folding and rolling, the method for manufacturing an electrode assembly.

12. The first unit cell and the second unit cell each include a tab protruding from the upper end of the unit cell, the first thickness compensating portion and the second thickness compensating portion each include two recessed portions, the first thickness compensating portion and the second thickness compensating portion are formed such that the recessed portions face the end of the separation film, and arranging the first unit cell and the second unit cell such that the tabs of the first unit cell and the second unit cell are located in the recessed portions, the method for manufacturing an electrode assembly according to claim 11.

13. The first unit cell and the second unit cell each include one or more selected from the group consisting of a positive electrode and a negative electrode, and a separation membrane, and the positive electrode and the negative electrode each have a flat portion with a constant thickness of the active material layer and an inclined portion in which the thickness of the active material layer decreases as going in the protruding direction of the tab, the method for manufacturing an electrode assembly according to claim 11, wherein the upper ends of the first unit cell and the second unit cell correspond to the inclined portions.

14. The method for manufacturing an electrode assembly according to claim 11, wherein the first thickness compensating portion and the second thickness compensating portion are adhered to each other outside the separation film by the rolling.

15. A secondary battery including the electrode assembly according to any one of claims 1 to 10 and an electrolyte.

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