Electrode assembly for secondary battery and manufacturing method thereof

Abstract

The present invention relates to a method for manufacturing an electrode assembly that can improve life characteristics and fast charging performance by minimizing a gap between a folding separator and an electrode, the method including the steps of arranging a plurality of unit cells on one side of a folding separator; fixing the unit cells on the folding separator; providing a binder composition on at least one end of the other side of the folding separator; and folding the folding separator to stack the unit cells.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0107606, filed on August 13, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly for a secondary battery and a manufacturing method thereof, and more particularly to a stack and folding type electrode assembly having excellent life characteristics and fast charging performance and a manufacturing method thereof. [Background technology]

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

[0004] Lithium secondary batteries are generally manufactured by placing an electrode assembly, which includes a stacked cathode, separator, and anode, in a battery case and injecting an electrolyte. Electrode assemblies can be classified into wound (jelly roll) type, layered type, and stack-and-folding type depending on the manufacturing method. Specifically, wound electrode assemblies are manufactured by rolling up long sheet-like cathode plates, separators, and anode plates, while stacked electrode assemblies are manufactured by stacking cathodes, separators, and anodes cut to a predetermined size. Furthermore, stack-and-folding electrode assemblies are manufactured by arranging unit cells, each consisting of a stacked cathode, separator, and anode, side by side on a long sheet-like folding separator, and then folding the assembly from one side.

[0005] Meanwhile, electrodes for lithium secondary batteries are manufactured by coating a current collector with electrode slurry to form an active material layer, which is then rolled. However, electrodes manufactured in this manner suffer from a phenomenon known as "sliding," in which the thickness of the active material layer decreases at the edges of the active material layer compared to the center due to a decrease in the amount of applied slurry. Figure 1 shows the thickness distribution in the width direction of the active material layer of an electrode manufactured by coating a current collector with electrode slurry. Figure 1 confirms the occurrence of the sliding phenomenon, in which the thickness of the active material layer decreases at the edges of the electrode.

[0006] Meanwhile, due to this sliding phenomenon, a gap is formed between the electrode and the separator at the end of the electrode. The gap acts as a diffusion resistance for lithium ions, causing problems such as lithium ions being unable to move smoothly in the corresponding area and being precipitated.

[0007] The gap between the electrode and the separator can be minimized by compressing the electrode and the separator using a heat and pressure process during the manufacturing of the electrode assembly. During the compression process, the binder contained in the electrode active material layer and / or the separator coating layer melts and is extruded into the gap, filling it.

[0008] However, in the case of a stack-and-fold type electrode assembly, due to the characteristics of the manufacturing process, an interface is created where the folding separator and electrode are not pressed together but merely come into contact, creating a gap between the electrode and separator at this interface, which can lead to lithium deposition. Figure 2 is a photograph taken after disassembling a battery cell using a conventional stack-and-fold type electrode assembly, and it can be seen from Figure 2 that lithium deposition occurs at the area where the underside of the folding separator and the unit cell come into contact (indicated by the box). Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is directed to solving the above problems, and provides an electrode assembly and a manufacturing method thereof that can improve life characteristics and fast charging performance by minimizing the gap between the folding separator and the electrode. [Means for solving the problem]

[0010] In one aspect, the present invention provides a method for manufacturing an electrode assembly, including the steps of: arranging a plurality of unit cells on one side of a folding separator; fixing the unit cells on the folding separator; providing a binder composition on at least one end portion of the other side of the folding separator; and folding the folding separator to stack the unit cells.

[0011] Here, the step of fixing the unit cells may be performed by heating and pressurizing the folding separator in which the unit cells are arranged.

[0012] The binder composition may be applied in the length direction of the folded separator, or may be provided at an end portion of the unit cell in a direction where the electrode tabs are disposed.

[0013] Furthermore, the binder composition has a binder coating amount of 0.1 g / m 2 ~1g / m 2 It may be provided so that

[0014] Furthermore, the binder composition may be provided in an area that is a distance of 0.15W from the end of the folding separator, where W is the width of the folding separator.

[0015] The binder composition may contain, as a binder, polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and it is particularly preferable to contain a water-based binder such as styrene-butadiene rubber.

[0016] In another aspect, the present invention provides an electrode assembly in which a plurality of unit cells, each including a positive electrode, a separator, and a negative electrode, are wound around a long sheet-like folding separator and stacked, the unit cells including a sliding portion at at least one end of an outermost electrode, where the thickness of an electrode active material layer is reduced, and a binder coating layer is formed between the sliding portion and the folding separator.

[0017] In yet another aspect, the present invention provides a secondary battery including the electrode assembly according to the present invention described above. [Effects of the Invention]

[0018] The present invention is characterized in that, when manufacturing a stack-and-fold type electrode assembly, a folding process is performed after providing a binder composition on the side of the folding separator where unit cells are not disposed. When the folding process is performed after providing the binder composition on the side where unit cells are not disposed as in the present invention, the binder composition is interposed between the outermost electrode of the unit cell and the folding separator, filling the gap between the electrode and the folding separator, thereby minimizing the deposition of lithium ions caused by the gap between the electrode and the folding separator. Therefore, when the electrode assembly manufactured by the method of the present invention is applied to a secondary battery, excellent long-term life characteristics and fast charging performance can be achieved. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a graph showing the thickness distribution of an active material layer of an electrode manufactured by coating an electrode slurry. [Figure 2] 1 is a photograph showing a lithium deposition phenomenon in a battery cell to which a conventional stack-and-fold electrode assembly is applied. [Figure 3] 3A to 3C are diagrams illustrating a manufacturing process of an electrode assembly according to an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a binder composition providing step. [Figure 5] 1A and 1B are diagrams illustrating an example of an electrode assembly according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will be described in detail below with reference to the accompanying drawings. The drawings are provided to allow those skilled in the art to clearly understand the present invention, and the present invention is not limited to the invention disclosed in the drawings.

[0021] In order to clearly explain the present invention, some components may be omitted in the drawings, and the same components are denoted by the same reference numerals.

[0022] Manufacturing method of electrode assembly First, a method for manufacturing an electrode assembly according to the present invention will be described.

[0023] 3 shows one embodiment of a method for manufacturing an electrode assembly according to the present invention. Hereinafter, the method for manufacturing an electrode assembly according to the present invention will be described with reference to FIG.

[0024] As shown in FIG. 3, the method for manufacturing an electrode assembly according to the present invention includes the steps of (A) arranging a plurality of unit cells on one side of a folding separator, (B) fixing the unit cells on the folding separator, (C) applying a binder composition to at least one end of the other side of the folding separator, and (D) folding the folding separator to stack the unit cells.

[0025] First, a plurality of unit cells 20A and 20B are arranged on one surface of the folding separation membrane 10 (see FIG. 3(A)).

[0026] The unit cells 20A and 20B are electrode stacks in which cathodes 22, separators 24, and anodes 26 cut to a predetermined size are stacked. The unit cells may have a bi-cell structure in which the same electrodes are arranged on the outermost sides, such as cathode 22 / separator 24 / anode 26 / separator 24 / cathode 22 or anode 26 / separator 24 / cathode 22 / separator 24 / anode 26, as shown in FIG. 3 . However, the structure is not limited thereto, and the unit cells may have a full-cell structure in which the number of cathodes and anodes is the same, such as cathode / separator / anode. Also, while FIG. 3 shows an electrode stack with a bi-cell structure consisting of five layers, the structure is not limited thereto, and the number of electrodes and separators stacked may vary.

[0027] The folding separator 10 is a long sheet-like separator and is distinguished from the cut separator 24 included in the unit cell. The folding separator 10 may be any of various separators used in the art, and may be, for example, a separator in which a polymer material such as ceramic particles and / or a binder is coated on the surface of a polyolefin-based porous polymer film.

[0028] A plurality of unit cells 20A and 20B are disposed on the folding separator 10. When adjacent unit cells are folded, the anode 26 and the cathode 22 are stacked with the folding separator 10 interposed therebetween.

[0029] Next, the unit cells 20A and 20B are fixed on the folding separation membrane 10 so that the unit cells 20A and 20B do not move during the folding process (see FIG. 3(B)).

[0030] The step of fixing the unit cells 20A, 20B may be performed by heating and pressurizing the folding separator 10 in which the unit cells 20A, 20B are arranged. When the heating and pressurizing process is performed, the binder component contained in the electrode active material layer and / or the coating layer of the folding separator melts due to heat, thereby bonding and fixing the unit cells to the folding separator. Specifically, heat is applied to the folding separator 10 in which the unit cells 20A, 20B are arranged using heating means 30 such as a heater, and then the unit cells 20A, 20B are pressed using pressure means 40 such as a roll press, thereby bonding the unit cells 20A, 20B to the folding separator 10 and fixing the unit cells.

[0031] In addition, during the heating and pressurizing process, the binder contained in the electrode active material layer and / or the folding separator coating layer in the region where the active material layer thickness is reduced at the end of the electrode (hereinafter referred to as the sliding portion) is pushed into the space between the folding separator and the electrode, thereby reducing the space between the folding separator and the unit cell, thereby suppressing lithium precipitation due to the space between the folding separator and the electrode.

[0032] On the other hand, the heating may be carried out at a temperature of 50°C to 150°C, preferably 60°C to 120°C, and more preferably 70°C to 90°C.

[0033] The pressure may be applied at a pressure of 10 kPa to 300 kPa, preferably 50 kPa to 250 kPa, and more preferably 100 kPa to 200 kPa.

[0034] When the heating and / or pressure application satisfies the above conditions, the unit cells and the folded separation membrane are smoothly fixed together and the separation space is smoothly reduced without damaging the components of the unit cells or the folded separation membrane.

[0035] Next, once the unit cells 20A and 20B are fixed on one side of the folding separation membrane 10, a binder composition 52 is provided on the other side of the folding separation membrane 10 (see FIG. 3(C)). Here, the other side refers to the side on which no unit cells are arranged, i.e., the surface opposite to the surface of the folding separation membrane on which the unit cells are arranged.

[0036] This step is intended to minimize the gap between the other side of the folded separator and the unit cells after the folding process. As described above, the unit cell fixing step can minimize the gap at the interface between the unit cells and the surface (one side) of the folded separator where the unit cells are arranged. However, gaps due to the sliding phenomenon of the active material layer still remain at the interface between the unit cells and the surface (other side) of the folded separator where no unit cells are arranged after folding. The presence of such gaps inhibits the diffusion of lithium ions, causing lithium ions to precipitate in the corresponding areas, resulting in poor life characteristics and fast charging performance.

[0037] In the present invention, to solve the above problem, a binder composition is provided on the other side of the folding separator immediately before the folding process of folding the folding separator to stack the unit cells, and the folding process is performed so that the binder composition fills the space between the folding separator and the unit cells during the folding process.

[0038] Here, the method for providing the binder composition 52 is not particularly limited, and can be carried out by a composition application method well known in the art, such as spraying, bar coating, roller coating, etc.

[0039] Meanwhile, the binder composition 52 is preferably provided at least at one end of the other surface of the folding separator 10. The sliding portion where the thickness of the electrode active material layer decreases is usually formed at the end of the electrode, so by providing the binder composition at the end of the folding separator corresponding to the end of the electrode, the separation space between the folding separator and the sliding portion can be effectively reduced.

[0040] Figure 4 shows an example of another surface of a folding separator provided with a binder composition by the method of the present invention. As shown in Figure 4, the binder composition 52 may be provided in the length direction L of the folding separator 10. Alternatively, the binder composition 52 may be provided at an end portion in the direction in which the electrode tabs 28 of the unit cell 20 are disposed. Since the sliding portion of the electrode active material layer is typically disposed in the direction of the electrode tabs, providing the binder composition in the length direction of the folding separator at the end portion in the direction in which the electrode tabs are disposed, as shown in Figure 4, is effective in reducing the spacing caused by the sliding portion.

[0041] Meanwhile, when the width of the folding separation membrane is W, the binder composition 52 may be provided in an area 0.15W away from the end E of the folding separation membrane, specifically, in an area 0.01W to 0.15W away from the end E of the folding separation membrane, more specifically, in an area 3mm to 10mm away from the end of the folding separation membrane. When the area where the binder composition is provided satisfies the above conditions, the binder can smoothly fill the space between the folding separation membrane and the sliding part. If the area where the binder composition is provided is too narrow, the space cannot be sufficiently filled. If the area where the binder composition is provided is too wide, the amount of binder composition used increases, which not only increases costs but also adversely affects the processability of the folding process due to the excess binder composition.

[0042] The binder composition has a binder coating amount of 0.1 g / m 2 ~1g / m 2 , preferably 0.1 g / m 2 ~0.8g / m 2 , more preferably 0.3 g / m 2 ~0.5g / m 2 When the amount of binder applied satisfies the above range, the separation space can be effectively reduced while minimizing side effects caused by excess binder.

[0043] Meanwhile, the binder composition may include a binder and a solvent.

[0044] As the binder, various binders used in the field of secondary batteries can be used, such as polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof.

[0045] In particular, it is particularly preferable to include an aqueous binder such as styrene-butadiene rubber. Generally, an aqueous binder is used for the coating layer of the folding separator and the negative electrode where lithium deposition occurs. Therefore, when an aqueous binder is used as the binder, the adhesive strength between the folding separator and the negative electrode is improved, which facilitates the elimination of the separation space, thereby more effectively suppressing lithium deposition.

[0046] On the other hand, the solvent is used to dissolve or disperse the binder component to make it coatable, and an appropriate solvent can be selected and used depending on the binder used. For example, when an aqueous binder is used, water can be used as the solvent, and when a non-aqueous binder is used, an organic solvent such as N-methylpyrrolidone, acetone, or alcohol can be used as the solvent. The solvent can be used in an amount that gives the binder composition a viscosity suitable for coating.

[0047] Although not essential, the binder composition may further contain additives such as inorganic particles, solid electrolytes, and ion-conductive polymers to improve electrolyte impregnation, conductivity, and resistance properties.

[0048] On the other hand, after the application of the binder composition, a drying step for removing the solvent may be further carried out, if necessary.

[0049] Next, the folding separator 10 is folded to stack the unit cells 20A and 20B (see FIG. 3(D)). The binder composition coated on the underside of the folding separator 10 is flexible and is inserted into the space between the folding separator and the unit cells during the folding process, thereby reducing the separation.

[0050] Meanwhile, after the folding is completed and the stacking of the unit cells is completed, a step of heating and / or pressurizing the electrode assembly with the stacked unit cells may be further performed, if necessary.

[0051] The heating and / or pressure application step is for fixing the folding separation membrane and tightly adhering the unit cells.

[0052] Here, the heating may be carried out at a temperature of 50°C to 150°C, preferably 60°C to 120°C, and more preferably 70°C to 90°C.

[0053] The pressure may be applied at a pressure of 10 kPa to 300 kPa, preferably 50 kPa to 250 kPa, and more preferably 100 kPa to 200 kPa.

[0054] When this process is further performed, the adhesive strength of the binder inserted into the gaps is increased by heating and / or pressurization, which is more effective in reducing the gaps. Furthermore, since the solvent in the binder composition can be volatilized during this process, a separate drying process is not required. Furthermore, the application of pressure brings the components within the unit cell and electrode assembly into close contact, which also improves the electrochemical properties.

[0055] electrode assembly Next, the electrode assembly according to the present invention will be described.

[0056] FIG. 5 shows an example of an electrode assembly according to the present invention.

[0057] As shown in FIG. 5, the electrode assembly 1 of the present invention is an electrode assembly in which a plurality of unit cells 20 are wound around a long sheet-like folding separator 10 and stacked.

[0058] The unit cell 20 is an electrode stack in which at least one positive electrode 22 and at least one negative electrode 26 are alternately stacked with a separator 24 interposed therebetween, and the positive electrode 22, the negative electrode 26, and the separator 24 are cut to a predetermined size.

[0059] The positive electrode, negative electrode, and separator included in the unit cell 20 may be any positive electrode, negative electrode, and separator used in the field of secondary batteries, and the material and shape thereof are not particularly limited.

[0060] For example, the positive electrode 22 may be manufactured by coating one or both surfaces of a positive electrode current collector with a positive electrode composite including a positive electrode active material, a binder, and a conductive material to form a positive electrode active material layer, and the negative electrode 26 may be manufactured by coating one or both surfaces of a negative electrode current collector with a negative electrode composite including a negative electrode active material, a binder, and a conductive material to form a negative electrode active material layer.

[0061] The positive electrode active material may be any of various materials used in the art, for example, lithium transition metal oxides such as lithium cobalt-based oxides, lithium nickel-based oxides, lithium manganese-based oxides, lithium nickel-cobalt-manganese-based oxides, lithium nickel-cobalt-aluminum-based oxides, and lithium nickel-cobalt-manganese-aluminum-based oxides, but is not limited thereto.

[0062] The negative electrode active material may be any of various materials used in the art, for example, carbonaceous materials such as natural graphite, artificial graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds that can be alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, and Al alloys; and SiO β Examples of the metal oxides that can be doped and dedoped with lithium, such as (0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, but are not limited to these.

[0063] The binder is a component that aids in bonding between the current collector and the active material and between the active materials, and examples of the binder include, but are not limited to, polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0064] The conductive material is a component for improving the conductivity of the electrode, and examples thereof include, but are not limited to, polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0065] Meanwhile, the separator refers to a separator that is cut to a predetermined size and interposed between the positive and negative electrodes of a unit cell, and is used as a concept distinct from a long, sheet-like folding separator. The separator may be a separator commonly used in the art, and its material is not particularly limited. For example, the separator may be a porous polymer film, such as a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may also be used. Furthermore, to ensure heat resistance or mechanical strength, a separator coated with a ceramic component or a polymer material may also be used, and may be selectively used as a single-layer or multi-layer structure.

[0066] Meanwhile, the unit cell 20 may have a full-cell structure including the same number of positive electrodes and negative electrodes, or a bi-cell structure in which the number of one of the positive electrodes and negative electrodes is one more than the other so that electrodes of the same polarity are arranged on the outermost upper and lower surfaces of the electrode stack.

[0067] FIG. 5 illustrates a bi-cell structure unit cell 20 in which three electrodes are stacked with two separators interposed therebetween, but the present invention is not limited thereto, and the number of electrodes and separators may be varied in various ways.

[0068] The folding separator 10 is a long sheet-like separator that is folded to surround the unit cells 20. The folding separator 10 may be any of various separators used in the art, and may be, for example, a separator in which a polymer material such as ceramic particles and / or a binder is coated on the surface of a polyolefin-based porous polymer film.

[0069] Meanwhile, the unit cell 20 includes a sliding portion where the thickness of the electrode active material layer is reduced at at least one end of the outermost electrode contacting the folding separator 10, and a binder coating layer 54 is formed between the sliding portion and the folding separator (see enlarged view in FIG. 5).

[0070] As described above, when an electrode active material layer is formed using a slurry coating process, a sliding portion occurs at the end of the coating, where the amount of coating slurry is reduced and the thickness of the active material layer is reduced. This sliding portion can be alleviated to a certain extent by performing a heating and / or pressure process. However, in the case of a conventional stack-and-fold type electrode assembly, the folding process creates an interface where the folding separator and the electrode are not pressed together but merely come into contact. The electrode located at this interface does not relax the sliding portion, leaving a gap between the folding separator and the electrode. In contrast, the electrode assembly 1 of the present invention provides a binder composition on the other side of the folding separator immediately before the folding process, and the binder composition forms a binder coating layer between the sliding portion and the folding separator, thereby reducing the gap.

[0071] When a binder coating layer is formed between the sliding part and the folding separator as in the present invention, lithium diffusion becomes smoother than when a separation space is present, thereby significantly reducing the lithium ion deposition phenomenon due to lithium diffusion resistance.

[0072] On the other hand, the binder coating layer 54 may include various binders used in the field of secondary batteries, such as polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and it is particularly preferable that the binder coating layer 54 include a water-based binder such as styrene-butadiene rubber.

[0073] The electrode assembly of the present invention as described above can be usefully applied to secondary batteries.

[0074] Specifically, the secondary battery according to the present invention includes a battery case, an electrode assembly and an electrolyte housed inside the battery case, wherein the electrode assembly is the above-described electrode assembly according to the present invention.

[0075] The battery case may be any of various battery cases used in the art, such as a square, cylindrical, or pouch-type battery case, and is preferably a pouch-type battery case.

[0076] On the other hand, as the electrolyte, any electrolyte commonly used in the field of secondary batteries, such as an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte, can be used, and the type of the electrolyte is not particularly limited.

[0077] The secondary battery is preferably a lithium ion battery or a lithium ion polymer battery, but is not limited thereto.

[0078] The lithium secondary battery according to the present invention has a minimized space between the folding separator and the unit cell, thereby suppressing lithium deposition and thereby achieving excellent long-term life characteristics and fast charging performance. Therefore, the battery can be effectively used in portable devices such as mobile phones, laptops, and digital cameras, electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs), and power storage systems. [Explanation of symbols]

[0079] 10 Folding separation membrane 20, 20A, 20B unit cells 22 Positive electrode 24 Separation membrane 26 negative electrode 28 Electrode tab 30 Heating means 40 Pressurizing means

Claims

1. disposing a plurality of unit cells on one surface of the folding separation membrane; Fixing a unit cell on the folding separation membrane; providing a binder composition on at least one end of the other surface of the folding separator; and The folding separator is folded to stack the unit cells, The unit cell includes a sliding portion at at least one end where the thickness of the electrode active material layer is reduced, the binder composition is interposed between the sliding portion and the folding separator to fill a space between the sliding portion and the folding separator; The step of fixing the unit cells is performed by heating and pressurizing the folding separator in which the unit cells are arranged, The method for manufacturing an electrode assembly may further include, after the step of stacking the unit cells, heating and pressurizing the electrode assembly on which the unit cells are stacked.

2. The method of claim 1 , wherein the binder composition is provided in the length direction of the folding separator.

3. The method for manufacturing an electrode assembly according to claim 1 , wherein the binder composition is provided at an end portion of the unit cell in a direction in which an electrode tab is disposed.

4. The step of providing the binder composition comprises providing a binder composition having a binder coating weight of 0.1 g / m ２ ~1.0 g / m ２ The method for manufacturing an electrode assembly according to claim 1 , wherein the method is carried out so as to:

5. The method of claim 1 , wherein the binder composition is provided in an area that is 0.15W away from an end of the folding separator, where W is a width of the folding separator.

6. The method for manufacturing an electrode assembly according to claim 1 , wherein the binder composition comprises a water-based binder.

7. 2. The method for manufacturing an electrode assembly according to claim 1, wherein, in the step of fixing the unit cells or the step of heating and pressurizing the electrode assembly including the stacked unit cells, the heating is performed at a temperature of 50°C to 150°C and the pressurization is performed under a pressure condition of 10 kPa to 300 kPa.

8. An electrode assembly in which a plurality of unit cells including a positive electrode, a separator, and a negative electrode are wound around a long sheet-like folding separator and stacked, The unit cell includes a sliding portion at at least one end where the thickness of the electrode active material layer is reduced, The electrode assembly, wherein a binder coating layer fills a space between the sliding portion and the folding separator.

9. The electrode assembly of claim 8 , wherein the binder coating layer comprises a water-based binder.

10. A secondary battery comprising the electrode assembly according to claim 8 or 9.

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