Electrode assembly and manufacturing method thereof

Abstract

The present invention relates to an electrode assembly and a manufacturing method thereof, and more particularly to an electrode assembly including a single-sided positive electrode, which is manufactured at low pressure and temperature to prevent deterioration of battery life due to Li-precipitation and increased resistance, and a manufacturing method thereof.

Description

[Technical Field]

[0001] This invention claims the benefit of the filing date of Patent Application No. 10-2023-0052674, filed with the Korean Intellectual Property Office on April 21, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electrode assembly and a manufacturing method thereof, and more particularly to an electrode assembly including a single-sided positive electrode, which is manufactured at low pressure and temperature to prevent deterioration of battery life due to Li-precipitation and increased resistance, and a manufacturing method thereof. [Background technology]

[0003] Electrochemical devices convert chemical energy into electrical energy using electrochemical reactions, and in recent years, lithium secondary batteries have been widely used due to their high energy density, high voltage, and long cycle life, which can be used in a variety of fields. In recent years, with the increasing demand for electric vehicles and energy storage devices, development has been carried out on materials and structures to maximize capacity and energy density.

[0004] A secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and may be manufactured by housing the electrode assembly in a case together with an electrolyte. Secondary batteries may be classified into pouch-type, cylindrical-type, prismatic-type, coin-type, etc. depending on the shape of the case in which the electrode assembly is housed, and may be classified into jelly-roll-type, stack-type, etc. depending on the manufacturing method and shape of the electrode assembly.

[0005] Recently, a zigzag stacking (ZZS) electrode assembly has been developed, in which a long sheet-shaped separator is folded in a zigzag pattern and positive and negative electrodes are alternately placed between adjacent folds. For example, a zigzag electrode assembly can be manufactured by supplying a long sheet-shaped separator wound into a cylinder, tilting or swinging the table on which the electrode assemblies are stacked, or by reciprocating the supply roll that transports the separator, folding the separator in a zigzag pattern and placing each electrode between the folds. Zigzag stacking has the advantage of being simpler than other types of stacking, resulting in superior productivity.

[0006] One method for increasing the energy density of a battery is to place a single-sided cathode on both ends of the battery. However, because single-sided cathodes tend to curl significantly, assembly requires long periods of pressing under high pressure and temperature. In this case, the pores in the electrode and separator may become clogged due to the high pressure and temperature, resulting in poor wettability and increased resistance in the battery. Furthermore, if the battery is manufactured under weak conditions, the single-sided cathodes at both ends of the battery may curl, causing the electrodes to lift with repeated cycles, resulting in Li-deposition in the affected areas and increased resistance, resulting in a decrease in battery life.

[0007] Therefore, there is a need for a method to solve the above problem even under low pressure and temperature conditions while using a single-sided positive electrode. Summary of the Invention [Problem to be solved by the invention]

[0008] The technical problem to be solved by the present invention is to provide an electrode assembly including a single-sided positive electrode, which can be manufactured at low pressure and temperature, and which can prevent deterioration of battery life due to Li-precipitation and increased resistance, and a manufacturing method thereof.

[0009] However, the problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0010] One embodiment of the present invention provides an electrode assembly including a single-sided positive electrode provided at both ends, a unit electrode assembly provided between the single-sided positive electrode, and a first separator provided between the single-sided positive electrode and the unit electrode assembly, wherein the unit electrode assembly has n+1 negative electrodes and n positive electrodes alternately arranged between 2n second separators (n is a positive integer), and an outer periphery of the single-sided positive electrode facing the first separator is at least partially provided with an adhesive coating layer including a first polymer binder.

[0011] According to one embodiment of the present invention, the first and second separators may be formed as a single separator that is folded in a zigzag pattern.

[0012] According to one embodiment of the present invention, the area of ​​the adhesive coating layer provided on the single-sided positive electrode may be 10% to 20% of the total area of ​​the surface of the single-sided positive electrode facing the first separator.

[0013] According to one embodiment of the present invention, the thickness of the adhesive coating layer may be 10% to 100% of the thickness of the first separator.

[0014] According to one embodiment of the present invention, the single-sided positive electrode may have an adhesive coating layer formed in a predetermined pattern on the entire surface facing the first separator.

[0015] According to one embodiment of the present invention, the first polymer binder may be a polyvinylidene-based resin.

[0016] According to one embodiment of the present invention, the first polymeric binder may be a copolymer of polyvinylidene propylene and hexafluoropropylene.

[0017] According to one embodiment of the present invention, the substitution rate of hexafluoropropylene in the first polymer binder may be 20% or more.

[0018] According to one embodiment of the present invention, the single-sided positive electrode includes a second polymer binder, and the separator includes a porous coating layer provided on at least one surface thereof and including a third polymer binder and inorganic particles. The second polymer binder and the third polymer binder included in the single-sided positive electrode and the porous coating layer may be the same as the first polymer binder included in the adhesive coating layer.

[0019] One embodiment of the present invention provides a method for manufacturing an electrode assembly, including the steps of: providing 2n second separators between first separators at both ends; providing (n+1) negative electrodes and (n) positive electrodes alternately between the first separators and the second separators; and providing single-sided positive electrodes having an adhesive coating layer on an outer periphery of the first separators at both ends to prepare a stack; and manufacturing an electrode assembly by applying heat and pressure to the stack.

[0020] According to one embodiment of the present invention, the electrode assembly may be fabricated at a temperature of less than 90° C. and a pressure of less than 6.5 MPa.

[0021] According to one embodiment of the present invention, the step of providing the second separator may include providing one separator by folding it in a zigzag pattern. [Effects of the Invention]

[0022] An electrode assembly according to one embodiment of the present invention includes a single-sided positive electrode including an adhesive coating layer, which can prevent deterioration of battery life due to Li-precipitation and increased resistance even when the electrode assembly is assembled at low pressure and temperature.

[0023] A method for manufacturing an electrode assembly according to an embodiment of the present invention can manufacture an electrode assembly at low pressure and temperature, thereby preventing deterioration of battery life due to Li-precipitation and increased resistance, and shortening the battery manufacturing time and increasing ease of manufacturing. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 10 is a schematic diagram of an electrode assembly of a comparative example.

[0025] [Figure 2] FIG. 1 is a schematic diagram of Li deposition occurring on the single-face positive electrode of Comparative Example 2.

[0026] [Figure 3] FIG. 1 is a schematic diagram of a single-sided positive electrode provided with an adhesion coating layer according to one embodiment of the present invention.

[0027] [Figure 4] 1 is a schematic diagram of an electrode assembly according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] In this specification, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further include other components, unless specifically stated to the contrary.

[0029] In this specification, "A and / or B" means "A and B, or A or B."

[0030] As used herein, the term "comprising" is used in listing materials, compositions, devices, and methods useful in the present invention, without limiting the listed examples.

[0031] In this specification, when a component is said to be "provided on" another component, this does not exclude other components being disposed therebetween, but means that other components may be further disposed thereon, unless otherwise specified.

[0032] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings, in which the details may be exaggerated, omitted, or illustrated in a schematic manner in order to explain or emphasize the contents of the embodiment of the present invention.

[0033] In one embodiment of the present invention, an electrode assembly 100 includes a single-sided positive electrode 110 provided at both ends, a unit electrode assembly 130 provided between the single-sided positive electrodes 110, and a first separator 111 provided between the single-sided positive electrodes 110 and the unit electrode assembly 130, wherein the unit electrode assembly 130 has n+1 negative electrodes 135 and n positive electrodes 137 alternately arranged between 2n second separators 133 (n is a positive integer), and the single-sided positive electrode 110 has an outer periphery on a surface facing the first separator 111, at least partially provided with an adhesive coating layer 113 including a first polymer binder.

[0034] An electrode assembly according to one embodiment of the present invention includes a single-sided positive electrode including an adhesive coating layer. This single-sided positive electrode has adhesive strength, and therefore, even when the electrode assembly is assembled at low pressure and temperature, deterioration of battery life due to Li-deposition and increased resistance can be prevented.

[0035] According to one embodiment of the present invention, the unit electrode assembly may be manufactured by thermocompression bonding a stack in which the positive electrode and the negative electrode are alternately arranged between separators folded in a zigzag pattern.

[0036] According to one embodiment of the present invention, the separator (meaning the first separator 111 and / or the second separator 133) may refer to, but is not limited to, a functional separator having a porous coating layer containing an inorganic material and a binder (third polymer binder) formed on at least one surface of a porous polymer substrate such as a polyolefin substrate or a nonwoven fabric. The separator may also refer to a free-standing separator formed of an inorganic material and a binder (third polymer binder) without a porous polymer substrate.

[0037] According to one embodiment of the present invention, the separator (meaning the first separator and / or the second separator) electrically insulates the positive electrode and the negative electrode to prevent short circuits while providing pores through which lithium ions can pass. The separator may be resistant to the electrolyte of the electrochemical device, which is an organic solvent. For example, the separator may include a porous polymer substrate. Specifically, the porous polymer substrate may include, but is not limited to, polymer resins such as polyolefins (e.g., polyethylene, polypropylene, and polybutene), polyvinyl chloride, polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimideamide, polyaramid, polycycloolefin, nylon, polytetrafluoroethylene, and copolymers or mixtures thereof.

[0038] According to one embodiment of the present invention, a porous coating layer may be formed on at least one surface of the separator (meaning the first separator and / or the second separator) by coating and drying a slurry. The slurry may include a polymer binder (third polymer binder), inorganic particles, a dispersion medium, etc. The porous coating layer may include inorganic particles for improving the mechanical properties and insulating properties of the separator, and a polymer binder for improving the adhesive strength between the electrode and the separator. The polymer binder may provide adhesive strength between the electrode and the separator while also binding adjacent inorganic particles and maintaining the bond. The inorganic particles may bind to adjacent inorganic particles to provide interstitial volumes, which are voids between the inorganic particles, and lithium ions may move through the interstitial volumes.

[0039] According to one embodiment of the present invention, the polymer binder (third polymer binder) may be an acrylic binder, a fluorine-based binder, or any other binder known in the art. As described below, the polymer binder (third polymer binder) may preferably be a fluorine-based binder.

[0040] According to one embodiment of the present invention, the inorganic particles may have one or more of lithium ion transport ability, piezoelectricity, and flame retardancy, and may be any inorganic particles known in the art. Specifically, the inorganic particles may be BaSO4, BaTiO3, Pb(Zr,Ti)O3 (PZT), b1-xLaxZr1-yTiyO3 (PLZT, 0 <x<1、0<y<1)、Pb(Mg 1 / 3 Nb 2 / 3)O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, SiC, Al(OH)3, TiO2, aluminum peroxide, zinc tin hydroxide (ZnSn(OH)6), tin-zinc oxide (Zn2SnO4, ZnSnO3), antimony trioxide (Sb2O3), antimony tetroxide (Sb2O4), antimony pentoxide (Sb2O5), boehmite (AlO(OH)), and combinations thereof, but this is merely an example and is not limited thereto.

[0041] According to one embodiment of the present invention, the total content of the inorganic particles may be more than 75 parts by weight based on 100 parts by weight of the adhesive coating layer, but is not limited thereto.

[0042] According to one embodiment of the present invention, the unit electrode assembly 130 has n+1 negative electrodes 135 and n positive electrodes 137 alternately arranged between 2n second separators 133 (n is a positive integer). Specifically, the positive electrode 137 and the negative electrode 135 have second separators 133 attached to both sides thereof, thereby forming 2n second separators 133. In addition, single-sided positive electrodes 110 adjacent to the first separator 111 are provided at both ends of the electrode assembly 100, and therefore, the unit electrode assembly 130 provided between the single-sided positive electrodes 110 provided at both ends has negative electrodes 135 located at both ends. Therefore, the unit electrode assembly 130 has n+1 negative electrodes 135 and n positive electrodes 137 alternately arranged.

[0043] According to one embodiment of the present invention, the positive electrode and the negative electrode may be formed by coating at least one surface of a material that is conductive without causing a chemical change in an electrochemical device with an electrode active material and then drying the coated material. The material and the electrode active material may be of any type that can be used in an electrochemical device.

[0044] According to one embodiment of the present invention, the thickness of the positive electrode 137 may be from 90 μm to 130 μm. Specifically, the thickness of the positive electrode may be from 90 μm to 125 μm, from 90 μm to 120 μm, from 90 μm to 115 μm, from 90 μm to 110 μm, or from 95 μm to 105 μm. Adjusting the thickness of the positive electrode within the above ranges increases ease of assembly of the electrode assembly, ensures a desired battery capacity, and prevents battery performance degradation.

[0045] According to one embodiment of the present invention, the thickness of the negative electrode 135 may be from 100 μm to 150 μm. Specifically, the thickness of the negative electrode may be from 105 μm to 145 μm, from 110 μm to 140 μm, from 115 μm to 135 μm, from 120 μm to 135 μm, or from 125 μm to 135 μm. Adjusting the thickness of the negative electrode within the above ranges increases ease of assembly of the electrode assembly, ensures a desired battery capacity, and prevents deterioration of battery performance.

[0046] According to one embodiment of the present invention, the thickness of the single-sided positive electrode 110 may be from 50 μm to 70 μm. Specifically, the thickness of the single-sided positive electrode may be from 55 μm to 65 μm. Adjusting the thickness of the single-sided positive electrode within the above range can improve ease of assembly of the electrode assembly and prevent deterioration of battery performance.

[0047] According to one embodiment of the present invention, the single-sided positive electrode has an outer periphery facing the first separator, at least partially coated with an adhesive coating layer containing a first polymer binder. FIG. 1 is a schematic diagram of an electrode assembly 10 of a comparative example. In FIG. 1, no adhesive coating layer is provided on the single-sided positive electrode 11. FIG. 2 is a schematic diagram of Li deposition occurring on the single-sided positive electrode 11 of Comparative Example 2. In FIG. 2, when the single-sided positive electrode does not have the adhesive coating layer and the battery is manufactured under weak conditions, the single-sided positive electrode at both ends of the battery curls, causing the gap between the electrodes to lift with repeated cycles, resulting in Li deposition in that area and an increase in resistance, resulting in a decrease in battery life.

[0048] Meanwhile, Figure 3 is a schematic diagram of a single-sided positive electrode 110 having an adhesive coating layer 113 according to Example 1 of the present invention. Figure 4 is a schematic diagram of an electrode assembly 100 according to an embodiment of the present invention. It can be seen from Figures 3 and 4 that, unlike Comparative Example 1, an adhesive coating layer is formed on the single-sided positive electrode. As described above, in the single-sided positive electrode, the outer surface facing the first separator is at least partially provided with an adhesive coating layer including a first polymer binder, thereby preventing deterioration of battery life due to Li-deposition and increased resistance, even when the electrode assembly is assembled at low pressure and temperature.

[0049] According to one embodiment of the present invention, the first separator 111 and the second separator 133 may be formed as a single separator folded in a zigzag pattern. Specifically, the single separator may be zigzag folded at a predetermined interval. In this case, the first separator and the second separator are not separate, independent components, but are connected by a single separator, and are simply defined differently depending on their positions. The interval is not limited as long as it prevents the positive electrode and the negative electrode from contacting each other, but is preferably a constant interval. The electrodes may be stacked with both sides surrounded by separators, and adjacent separators may be bonded to each other by thermocompression. The positive electrode and the negative electrode are bonded to adjacent separators, meaning that the electrodes and separators are bonded within a single electrode assembly. As described above, the first separator and the second separator are formed as a single separator folded in a zigzag pattern and manufactured using a zigzag stacking method, thereby achieving a more stable electrode assembly.

[0050] According to one embodiment of the present invention, the area of ​​the adhesive coating layer 113 provided on the single-sided positive electrode 110 may be 10% to 20% of the total area of ​​the surface of the single-sided positive electrode 110 facing the first separator 111. Specifically, the area of ​​the adhesive coating layer provided on the single-sided positive electrode may be 10% to 20%, 11% to 19%, 12% to 18%, 13% to 17%, or 14% to 16% of the total area of ​​the surface of the single-sided positive electrode facing the first separator. By adjusting the area ratio of the adhesive coating layer within the above ranges, curling of the single-sided positive electrode can be prevented, and deterioration of battery life due to Li-deposition and increased resistance in the corresponding area can be prevented.

[0051] According to one embodiment of the present invention, the thickness of the adhesive coating layer 113 may be 10% to 100% of the thickness of the first separator 111. Specifically, the thickness of the adhesive coating layer may be 15% to 95%, 20% to 90%, 25% to 85%, 30% to 80%, 35% to 75%, 40% to 70%, 45% to 65%, or 50% to 60%. As described above, adjusting the thickness of the adhesive coating layer relative to the thickness of the first separator may facilitate assembly of the electrode assembly, and the single-sided positive electrode and the first separator may be uniformly bonded to prevent deterioration of battery life due to Li-deposition and increased resistance.

[0052] According to one embodiment of the present invention, the thickness of the adhesive coating layer 113 may be from 1 μm to 20 μm. Specifically, the thickness of the adhesive coating layer may be from 2 μm to 19 μm, from 3 μm to 18 μm, from 4 μm to 17 μm, from 5 μm to 16 μm, from 6 μm to 15 μm, from 7 μm to 14 μm, from 8 μm to 13 μm, from 9 μm to 12 μm, or from 10 μm to 11 μm. By adjusting the thickness of the adhesive coating layer within the above range, the thickness of the single-sided positive electrode can be controlled and adhesive strength can be exerted, preventing deterioration of battery life due to Li-deposition and increased resistance even when the electrode assembly is assembled at low pressure and temperature.

[0053] According to one embodiment of the present invention, the thickness of the first separator 111 may be from 5 μm to 30 μm. Specifically, the thickness of the first separator may be from 10 μm to 25 μm, or from 15 μm to 20 μm, and preferably 15 μm. By adjusting the thickness of the first separator within the above range, the volume of the electrode assembly can be minimized and the positive and negative electrodes can be electrically insulated.

[0054] Furthermore, the thickness of the second separator 133 may be the same as the thickness of the first separator 111. Also, if the first separator and the second separator are formed as a single separator folded in a zigzag pattern, it is clear that the thickness of the first separator and the second separator are the same.

[0055] In one embodiment of the present invention, the thicknesses of the separator and adhesive coating layer may be measured using a contact-type thickness gauge, such as Mitutoyo's VL-50S-B.

[0056] According to one embodiment of the present invention, the entire surface of the single-sided positive electrode 110 facing the first separator 111 may be provided with an adhesive coating layer 113 in a predetermined pattern. While the adhesive coating layer 113 provided on the single-sided positive electrode 110 has a specific shape as shown in FIGS. 3 and 4, this is merely an example and is not intended to be limiting. As described above, the adhesive coating layer provided in a predetermined pattern on the entire surface of the single-sided positive electrode facing the first separator can increase the adhesive strength between the single-sided positive electrode and the first separator and prevent deterioration of battery life due to Li-deposition and increased resistance.

[0057] According to one embodiment of the present invention, the first polymer binder may be a polyvinylidene-based resin. As described above, by selecting a polyvinylidene-based resin as the first polymer binder, the porosity of the first polymer separator can be maintained and adhesive strength can be maintained even when the coating layer is wetted by the electrolyte after battery activation. Furthermore, the stiffness of the battery can be improved, and bending of the single-sided positive electrode can be prevented, thereby preventing deterioration of battery life due to Li-deposition and increased resistance.

[0058] According to one embodiment of the present invention, the first polymer binder may be a copolymer of polyvinylidene propylene and hexafluoropropylene.

[0059] According to one embodiment of the present invention, the first polymer binder may have a substitution rate of hexafluoropropylene of 20% or more. Specifically, the substitution rate of hexafluoropropylene may be 20% by weight or more and 50% by weight or less, 25% by weight or more and 45% by weight or less, or 30% by weight or more and 40% by weight or less. As described above, by selecting the first polymer binder having a substitution rate of hexafluoropropylene of 20% or more, it is possible to increase the adhesion between the single-sided positive electrode and the first separator while maintaining the porosity of the separator, and to maintain the adhesion even when the coating layer is wetted by the electrolyte after activation of the battery.

[0060] According to one embodiment of the present invention, the single-sided positive electrode includes a second polymer binder, and the separator includes a porous coating layer provided on at least one surface thereof and including a third polymer binder and inorganic particles, and the second and third polymer binders included in the single-sided positive electrode and the porous coating layer may be the same as the first polymer binder included in the adhesive coating layer. As described above, by forming the first, second, and third polymer binders to be the same, the adhesive strength between the adhesive coating layer and the single-sided positive electrode and between the adhesive coating layer and the first separator is increased, thereby preventing deterioration of battery life due to Li-deposition and increased resistance, even when the battery assembly is assembled at low pressure and temperature.

[0061] According to one embodiment of the present invention, the electrode assembly 100 can be used in an electrochemical device. The electrochemical device can be manufactured by inserting the electrode assembly into a pouch or case, injecting an electrolyte, and then sealing the pouch or case.

[0062] According to one embodiment of the present invention, the electrolyte may be a non-aqueous electrolyte containing a lithium salt. The electrolyte may include an electrolyte and a lithium salt, and the electrolyte may be a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, or the like.

[0063] According to one embodiment of the present invention, the shape of the case or pouch into which the electrode assembly is inserted is not limited. For example, the electrochemical device may be a cylindrical, prismatic, coin-shaped, or pouch-shaped lithium secondary battery. The lithium secondary battery is packed or modularized as a unit cell and can be used in small devices such as computers, mobile phones, and power tools; power tools powered by battery-like motors; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheelers including electric bicycles (E-bikes) and electric scooters; electric golf carts; and energy storage systems.

[0064] One embodiment of the present invention provides a method for manufacturing an electrode assembly, including the steps of: providing 2n second separators 133 between first separators 111 at both ends; providing (n+1) negative electrodes 135 and n positive electrodes 137 alternately between the first separators 111 and the second separators 133; and providing single-sided positive electrodes 110 each having an adhesive coating layer 113 on an outer periphery on the first separators 111 at both ends to prepare a stack; and applying heat and pressure to the stack to manufacture an electrode assembly 100. In the description of the method for manufacturing the electrode assembly, the same content as the description of the electrode assembly described above shall be substituted with the description of the previous embodiment.

[0065] A method for manufacturing an electrode assembly according to an embodiment of the present invention can manufacture an electrode assembly at low pressure and temperature, thereby preventing deterioration of battery life due to Li-precipitation and increased resistance, and shortening the battery manufacturing time and increasing ease of manufacturing.

[0066] According to one embodiment of the present invention, the method includes providing 2n second separators between the first separators at both ends. The 2n second separators are necessary because the positive electrode and the negative electrode have second separators attached adjacent to each other on both sides.

[0067] According to one embodiment of the present invention, the second separator may be formed by stacking each cut separator in the order of second separator, anode, second separator, cathode, second separator, anode, and second separator (when n=1) to form a unit electrode assembly, but this is merely an example and is not limited thereto.

[0068] According to one embodiment of the present invention, the method includes preparing a stack by alternately disposing (n+1) negative electrodes and (n) positive electrodes between the first and second separators and disposing single-sided positive electrodes on the first separators at both ends. Specifically, the thickness of the stack may be 2 mm to 9.5 mm. Specifically, the thickness of the stack may be 2.5 mm to 9 mm, 3 mm to 8.5 mm, 3.5 mm to 8 mm, 4 mm to 7.5 mm, 4.5 mm to 7 mm, or 5 mm to 6.5 mm. Adjusting the thickness of the stack within the above ranges allows uniform adhesion between all electrodes and separators constituting the stack through thermocompression bonding.

[0069] According to one embodiment of the present invention, the method includes applying heat and pressure to the laminate to manufacture an electrode assembly. Specifically, the heat and pressure may be applied to the laminate to bond the positive electrode and the separator, and the negative electrode and the separator to manufacture a unit electrode assembly. The thermocompression may be performed by compressing the top and bottom layers of the laminate using a press. The press may be of any type, as long as it can simultaneously or at different times apply heat and pressure to one or both sides of the laminate while maintaining the alignment of the separator and electrodes contained in the laminate, thereby bonding the separator and the electrodes.

[0070] According to one embodiment of the present invention, the method may further include the step of preparing an adhesive coating layer including a first polymer binder on the outer periphery of the single-sided positive electrode before the step of preparing the laminate. As described above, by further including the step of preparing an adhesive coating layer including a first polymer binder on the outer periphery of the single-sided positive electrode before the step of preparing the laminate, the single-sided positive electrode has adhesive strength, and deterioration of battery life due to Li-deposition and increased resistance can be prevented even when the electrode assembly is assembled at low pressure and temperature.

[0071] According to one embodiment of the present invention, in the step of preparing the laminate, providing a single-sided positive electrode having an adhesive coating layer on the outer periphery of the first separator at both ends may mean providing the single-sided positive electrode such that the first separator and the outer periphery face each other. As described above, by providing the single-sided positive electrode, the single-sided positive electrode has adhesive strength, and therefore, deterioration of battery life due to Li-deposition and increased resistance can be prevented even when the electrode assembly is assembled at low pressure and temperature.

[0072] According to one embodiment of the present invention, the electrode assembly may be fabricated at a temperature of less than 90° C. and a pressure of less than 6.5 MPa.

[0073] Specifically, the temperature may be 45°C or higher but lower than 90°C, 50°C or higher but lower than 85°C, 55°C or higher but lower than 85°C, or 60°C or higher but lower than 85°C. Specifically, the pressure may be 3 MPa or higher but lower than 6.5 MPa, 3 MPa or higher but lower than 6.0 MPa, or 3 MPa or higher but lower than 5.5 MPa. If the pressure is lower than this range, the electrodes may not be fixed in position, and the electrodes may come off from their designated positions during handling of the stack. If the pressure exceeds this range, the coating layer formed on the electrodes may be destroyed or the pore structure formed in the separator may be destroyed, resulting in problems with the separator's air permeability and electrical resistance.

[0074] By adjusting the temperature and pressure conditions of the thermocompression bonding within the above ranges, the adhesive strength between the separator and the electrodes constituting the laminate can be realized without causing damage to the laminate, and deterioration of battery life due to Li-precipitation and increased resistance can be prevented.

[0075] According to one embodiment of the present invention, the step of providing the separator may include providing a separator by zigzag folding. Furthermore, a stack may be prepared by alternately arranging positive and negative electrodes between folds formed by zigzag folding the separator. The step of manufacturing an electrode assembly by applying heat and pressure to the stack may be the same as described above.

[0076] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples of the present invention can be modified into various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples in this specification are provided to more completely explain the present invention to those skilled in the art.

[0077] Example 1 A 15 μm thick separator coated with a slurry containing an inorganic material and a binder was prepared, and 30 100 μm thick positive electrodes and 31 130 μm thick negative electrodes were prepared. The separator was folded in a zigzag pattern at intervals of 98.5 mm, with the positive and negative electrodes alternately arranged between the separators. A stack was then prepared by placing single-sided positive electrodes (60 μm thick) with adhesive coating layers (5 μm thick) on the separators at both ends.

[0078] The laminate was placed in a press and subjected to thermocompression bonding once at 60° C. and a pressure of 4.5 MPa for 20 seconds to prepare an electrode assembly.

[0079] <Example 2> The same laminate as in Example 1 was prepared.

[0080] The laminate was placed in a press and subjected to thermocompression bonding once at 70° C. and a pressure of 5.5 MPa for 10 seconds to prepare an electrode assembly.

[0081] Example 3 The same laminate as in Example 1 was prepared.

[0082] The laminate was placed in a press and subjected to thermocompression bonding once at 85° C. and a pressure of 3.0 MPa for 10 seconds to prepare an electrode assembly.

[0083] <Comparative Example 1> A laminate was prepared in the same manner as in Example 1, except that a single-sided positive electrode without an adhesive coating layer was used.

[0084] The laminate was placed in a press and subjected to thermocompression bonding once at 90° C. and a pressure of 6.5 MPa for 20 seconds to prepare an electrode assembly.

[0085] <Comparative Example 2> A laminate was prepared in the same manner as in Example 1, except that a single-sided positive electrode without an adhesive coating layer was used.

[0086] The laminate was placed in a press and subjected to thermocompression bonding once at 60° C. and a pressure of 4.5 MPa for 20 seconds to prepare an electrode assembly.

[0087] <Experimental Example 1> The manufacturing process of the electrode assemblies manufactured in the examples and comparative examples, the time required for manufacturing the electrode assemblies, and whether or not lithium (Li) was deposited after manufacturing are summarized in Table 1 below.

[0088] <Experimental Example 2> The electrical resistance was measured by preparing cells using the electrode assemblies prepared in the examples and comparative examples, leaving the cells at room temperature for one day, and then measuring the resistance of the separator of the electrode assembly using an impedance measurement method. The measured resistance values ​​(mΩ) are summarized in Table 1 below.

[0089] [Table 1]

[0090] Figure 2 is a schematic diagram of Li deposition occurring on the single-sided positive electrode of Comparative Example 2. As can be seen from Figure 2, Li deposition occurs when the adhesive coating layer is not provided on the single-sided positive electrode and the battery is manufactured under weak conditions.

[0091] Meanwhile, Figure 3 is a schematic diagram of a single-sided positive electrode provided with an adhesive coating layer in Examples 1 to 3. Figure 4 is a schematic diagram of an electrode assembly in Examples 1 to 3. It can be seen from Figures 3 and 4 that, unlike the Comparative Example, Li-deposition does not occur even when the electrode assembly is assembled at low pressure and temperature because an adhesive coating layer is provided on the single-sided positive electrode. [Explanation of symbols]

[0092] 10, 100: Electrode assembly

[0093] 11, 110: Single-sided positive electrode

[0094] 13, 130: unit electrode assembly

[0095] 1, 111: First separation membrane

[0096] 113: Adhesive coating layer

[0097] 3, 133: Second separation membrane

[0098] 5, 135: Negative electrode

[0099] 7, 137: Positive electrode

Claims

1. An electrode assembly including single-sided positive electrodes provided at both ends, unit electrode assemblies provided between the single-sided positive electrodes, and a first separator provided between the single-sided positive electrodes and the unit electrode assemblies, The unit electrode assembly has n+1 negative electrodes and n positive electrodes alternately arranged between 2n second separators (n is a positive integer), In the single-sided positive electrode, an outer surface of a surface facing the first separator is at least partially provided with an adhesive coating layer including a first polymer binder.

2. The electrode assembly of claim 1 , wherein the first separator and the second separator are formed as a single separator folded in a zigzag pattern.

3. 2. The electrode assembly of claim 1, wherein the adhesive coating layer on the single-sided positive electrode has an area of ​​10% to 20% of the total area of ​​the surface of the single-sided positive electrode facing the first separator.

4. The electrode assembly of claim 1 , wherein the thickness of the adhesive coating layer is 10% to 100% of the thickness of the first separator.

5. The electrode assembly of claim 1 , wherein the single-sided positive electrode has an adhesive coating layer formed in a predetermined pattern on the entire surface facing the first separator.

6. The electrode assembly of claim 1 , wherein the first polymer binder is a polyvinylidene-based resin.

7. The electrode assembly of claim 1 , wherein the first polymer binder is a copolymer of polyvinylidene propylene and hexafluoropropylene.

8. The electrode assembly of claim 7 , wherein the substitution rate of the hexafluoropropylene in the first polymer binder is 20% or more.

9. the single-sided positive electrode comprises a second polymeric binder; the separator includes a porous coating layer provided on at least one surface thereof, the porous coating layer including a third polymer binder and inorganic particles; 3. The electrode assembly of claim 2, wherein the second polymer binder and the third polymer binder contained in the single-sided positive electrode and the porous coating layer are the same as the first polymer binder contained in the adhesive coating layer.

10. providing 2n second separation membranes between the first separation membranes at both ends; preparing a stack by alternately providing n+1 negative electrodes and n positive electrodes between the first separator and the second separator, and providing single-sided positive electrodes having adhesive coating layers on the outer peripheries of the first separators at both ends; and applying heat and pressure to the laminate to produce an electrode assembly.

11. The method of claim 10, wherein the step of fabricating the electrode assembly is performed at a temperature of less than 90°C and a pressure of less than 6.5 MPa.

12. 12. The method of claim 10, wherein the providing of the second separator comprises providing one separator by folding it in a zigzag pattern.

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