Manufacturing method of secondary batteries

Abstract

The present invention relates to a method for manufacturing a secondary battery. Before laminating an electrode and a separator, an aqueous solvent can be sprayed onto the surface of the electrode active material layer to activate the electrode active material layer. As a result, the adhesive force between the electrode and the separator is improved, the capacity retention rate and the rate characteristics are improved, and thus the battery life is improved.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a secondary battery.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0151646, filed on November 14, 2022, and all content disclosed in the specification and drawings of said application is incorporated herein. [Background technology]

[0003] As technological development and demand for mobile devices increase, the demand for rechargeable batteries as an energy source is surging, and consequently, research into rechargeable batteries that can meet diverse requirements is flourishing. Among these, the development of rechargeable batteries and lithium-ion batteries with high energy density are of particular interest. In recent years, there has been a growing demand for rechargeable batteries that offer improved performance in terms of increased capacity, lower resistance, improved mechanical properties, and increased productivity, while ensuring safety and accommodating the expansion and development of applications.

[0004] A lithium secondary battery has a structure in which an electrolyte containing a lithium salt is impregnated into an electrode assembly, which consists of a positive electrode and a negative electrode, each coated with an active material on an electrode current collector, and a porous separation membrane interposed between the positive and negative electrodes. In a lithium secondary battery, during charging, lithium ions from the positive electrode active material are inserted into the negative electrode active material, and during discharge, they are released and travel back and forth between the two electrodes, transferring energy through this process, thereby enabling charging and discharging.

[0005] However, during charging and discharging, the active material repeatedly expands and contracts in volume while reacting with lithium ions, which can lead to a decrease in capacity retention, charge-discharge efficiency, and lifespan characteristics. Research is underway to control this using binder polymers contained in the active material layer. However, due to viscosity characteristics and other factors, stable application to conventional slurry systems is difficult. Furthermore, using a large amount of binder polymer in the active material layer can lead to problems such as increased electrode resistance and decreased capacity due to reduced initial efficiency, resulting in a decline in battery performance. [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention has been made in view of the above-mentioned problems, and aims to provide a method for manufacturing a secondary battery that improves the mechanical and electrochemical performance of the electrode by inducing covalent bonding between the binder polymer of the electrode active material layer and the separation membrane, and thereby improves the battery life.

[0007] Other objectives and advantages of the present invention can be realized by the means and methods described in the claims, or combinations thereof. [Means for solving the problem]

[0008] The inventors have found that the above problems can be solved by the following method for manufacturing a secondary battery.

[0009] According to the first concrete example, (S10) A step of preparing an electrode comprising an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separation membrane comprising a porous substrate and an inorganic coating layer formed on at least one surface of the porous substrate, (S20) A step of spraying an aqueous solvent onto the surface of the electrode active material layer, (S30) A step of manufacturing an electrode assembly including an electrode and a separation membrane by laminating the surface of the electrode active material layer from step S20 and the inorganic coating layer of the separation membrane so that they face each other, (S40) The step of drying the electrode assembly from step S30, The electrode active material layer contains a binder polymer containing a carboxyl group, The aforementioned separation membrane relates to a method for manufacturing a secondary battery, in which the inorganic coating layer contains boehmite.

[0010] According to the second example, in the first example, The above step S20 relates to a method for manufacturing a secondary battery, in which an aqueous solvent at a temperature of 20°C to 30°C is sprayed onto at least a portion of the surface of the electrode active material layer.

[0011] According to the third embodiment, in the first embodiment or the second embodiment, The above step S20 relates to a method for manufacturing a secondary battery, in which an aqueous solvent is sprayed in a mist form onto at least a portion of the surface of the electrode active material layer for 1 to 10 seconds.

[0012] According to the fourth example, in any one of the first to third examples, The lamination in step S30 is carried out at a temperature of 50°C to 130°C and at a load of 1 kgf / cm². 2 ~10 kgf / cm² 2 This relates to a method for manufacturing a secondary battery under certain pressure conditions.

[0013] According to the fifth example of manifestation, in any one of the first to fourth examples of manifestation, The drying in step S40 is a method for manufacturing a secondary battery, which involves vacuum drying at a temperature of 90°C to 130°C.

[0014] According to the sixth example, in any one of the first to fifth examples, This invention relates to a method for manufacturing a secondary battery in which the hydroxyl group of the boehmite and the carboxyl group of the binder polymer undergo a condensation reaction to form a covalent bond.

[0015] According to the 7th embodiment, in any one of the 1st to 6th embodiments, The present invention relates to a method for manufacturing a secondary battery, wherein the binder polymer containing a carboxy group is a water-dispersible or water-soluble binder polymer.

[0016] According to the eighth embodiment, in any one of the first to seventh embodiments, The present invention relates to a method for manufacturing a secondary battery, wherein the binder polymer containing a carboxy group is carboxymethyl cellulose, polyacrylic acid, or a combination thereof.

[0017] According to the ninth embodiment, in any one of the first to eighth embodiments, The electrode further includes a styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose, or an adhesive binder polymer of two or more of these. The present invention relates to a method for manufacturing a secondary battery.

[0018] According to the tenth embodiment, in any one of the first to ninth embodiments, The present invention relates to a method for manufacturing a secondary battery, wherein the electrode is a negative electrode and contains a carbon-based active material and a silicon-based active material as negative electrode active materials.

[0019] According to the eleventh embodiment, in any one of the first to tenth embodiments, The aqueous solvent includes water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, diethylene glycol, tripropylene glycol, or a mixture of two or more of these, and relates to a method for manufacturing a secondary battery.

[0020] According to the twelfth embodiment, it relates to a secondary battery manufactured by the manufacturing method of any one of the first to eleventh embodiments.

Advantages of the Invention

[0021] The method for manufacturing a secondary battery of the present invention can improve the mechanical performance and electrochemical performance of the electrode in a simpler way. Specifically, before laminating the electrode and the separator, an aqueous solvent is sprayed onto the electrode active material layer to activate the electrode active material layer, thereby improving the adhesion between the electrode and the separator, and further improving the capacity retention rate and rate characteristics, so that the battery life can be improved.

[0022] The following drawings attached to this specification illustrate desirable embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention. Therefore, the present invention should not be construed as being limited only to the matters described in the drawings. Note that the shape, size, scale, or ratio of elements in the drawings attached to this specification may be exaggerated for the purpose of emphasizing a clearer explanation.

Brief Description of the Drawings

[0023] [Figure 1] It is a flowchart showing the manufacturing process of a secondary battery according to an aspect of the present invention. [Figure 2] It is a diagram schematically showing the manufacturing process of a secondary battery according to an aspect of the present invention. [Figure 3] It is a diagram showing the chemical structures of boehmite and a binder polymer and their condensation reaction.

Modes for Carrying Out the Invention

[0024] Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of terms in order to best describe the invention. Accordingly, it should be understood that the embodiments and configurations shown in the drawings described herein are merely the most preferred embodiments of the present invention and do not represent the entirety of the technical idea of ​​the present invention, and that there may be a variety of equivalents and modifications that can be substituted therein at the time of this application.

[0025] When a part of the specification is described as "including" a certain component, unless otherwise specified, it means that it may include other components, rather than excluding them.

[0026] Terms used throughout this specification, such as “approximately” and “substantially,” are used to mean, when specific manufacturing and material tolerances are presented, the numerical values ​​or values ​​close to those values, and are used to prevent unscrupulous infringers from unfairly using disclosures that refer to precise or absolute numerical values ​​to aid in understanding this application.

[0027] Throughout this specification, the phrase "A and / or B" means "A or B, or both."

[0028] This invention relates to a method for manufacturing a secondary battery.

[0029] In the present invention, the secondary battery is a device that converts chemical energy into electrical energy by an electrochemical reaction, and a lithium secondary battery is preferred, which includes lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries.

[0030] The secondary battery includes an electrode assembly in which electrodes and a separator membrane are stacked, and specifically, at least one negative electrode and at least one positive electrode may be alternately stacked with a separator membrane in between.

[0031] The electrode comprises an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and the separation membrane comprises a porous substrate and an inorganic coating layer formed on at least one surface of the substrate.

[0032] The electrode active material layer contains a binder polymer containing a carboxyl group as a binder resin, and the inorganic coating layer contains boehmite.

[0033] The inorganic coating layer of the separation membrane and the electrode active material layer are laminated facing each other, and the hydroxyl group (-OH) of the boehmite and the carboxyl group (-COOH) of the binder polymer react to form a covalent bond (as a result of a condensation reaction).

[0034] Typically, the main cause of electrode performance degradation is the periodic volume expansion and contraction of the electrode active material, specifically the negative electrode active material, during charging and discharging. If the volume changes of the electrode active material cannot be controlled, the number of contact points between the electrode active materials decreases, which can lead to a reduction in electrical properties and crack formation, thus degrading the lifespan.

[0035] The method for manufacturing a secondary battery according to the present invention includes a predetermined step of spraying an aqueous solvent onto the surface of the electrode active material layer. This induces a predetermined chemical bond between the inorganic coating layer of the separation membrane and the electrode active material layer, which acts as a buffer against volume changes of the electrode active material. As a result, the mechanical performance of the electrode can be improved, and consequently, the battery life can be extended.

[0036] In one embodiment of the present invention, the method for manufacturing a secondary battery is: (S10) A step of preparing an electrode comprising an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separation membrane comprising a porous substrate and an inorganic coating layer formed on at least one surface of the substrate, (S20) A step of spraying an aqueous solvent onto the surface of the electrode active material layer, (S30) A step of manufacturing an electrode assembly including an electrode and a separation membrane by laminating the surface of the electrode active material layer from step S20 and the inorganic coating layer of the separation membrane so that they face each other, (S40) The step of drying the electrode assembly from step S30, is included.

[0037] The following provides a detailed explanation of each stage.

[0038] First, an electrode comprising an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separation membrane comprising a porous substrate and an inorganic coating layer formed on at least one surface of the substrate are prepared (step S10).

[0039] In this case, the electrode active material layer contains a binder polymer containing a carboxyl group, and the separation membrane contains boehmite in its inorganic coating layer.

[0040] In the present invention, the electrode is a positive electrode and / or a negative electrode, and the electrode comprises an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, the electrode active material layer comprising an electrode active material and a binder polymer. The electrode can be manufactured by applying a slurry containing the electrode active material and binder polymer to an electrode current collector by conventional methods in the art.

[0041] The electrode current collector is not particularly limited as long as it does not induce a chemical change in the secondary battery and has high conductivity. For example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc., can be used.

[0042] When the electrode is a negative electrode, the electrode active material layer may contain a negative electrode active material, and when the electrode is a positive electrode, the electrode active material layer may contain a positive electrode active material.

[0043] For example, as the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium can be used. Specific examples include carbon-based active materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; silicon-based active materials such as SiOx (0 < x ≤ 2) can be used, and metal-based compounds alloyable with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides capable of doping and undoping lithium such as SnO2, vanadium oxides, and lithium vanadium oxides; or composites containing the metal-based compound and the carbon-based active material such as Si-C composites or Sn-C composites. One or a mixture of two or more of these can be used. Further, a thin film of metallic lithium can be used as the negative electrode active material. Also, as the carbon-based active material, both low-crystalline carbon and high-crystalline carbon can be used. Representative low-crystalline carbons include soft carbon and hard carbon, and representative high-crystalline carbons include amorphous, plate-like, flaky, spherical, or fibrous natural graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbons such as petroleum or coal tar pitch-derived cokes.

[0044] For example, the positive electrode active material includes layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; chemical formula Li 1+x Mn2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Lithium nickel oxide represented by O2 (where M = one or more elements selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and x = 0.01 to 0.9); chemical formula LiMn 2-x M x Lithium manganese composite oxides represented as O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta, and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc., are examples, but are not limited to these.

[0045] The aforementioned binder polymer includes a binder polymer containing a carboxyl group.

[0046] The binder polymer containing the carboxyl group can undergo a condensation reaction with boehmite contained in the separation membrane described later to form a covalent bond. Furthermore, by spraying an aqueous solvent onto the surface of the electrode active material layer described later, at least some of the carboxyl groups of the binder polymer located on the surface of the active material layer are activated by hydrogen bonding with the aqueous solvent. The activated carboxyl groups of the binder polymer then form a covalent bond with boehmite in a subsequent process, thereby improving the mechanical properties and lifespan of the electrode.

[0047] The binder polymer containing the carboxyl group may be water-dispersible or water-soluble. In this specification, the water-dispersible binder polymer is a polymer that, when added to an aqueous solvent, does not dissolve in the aqueous solvent but is at least partially dispersible, and the water-soluble binder polymer is a polymer that, when added to an aqueous solvent, is at least partially dissolved.

[0048] The water-dispersible binder polymer may be, for example, polyacrylic acid, and the water-soluble binder polymer may be carboxymethylcellulose. The water-dispersible binder polymer and the water-soluble binder polymer may also be used in mixture form.

[0049] Furthermore, the electrode active material layer may further contain an adhesive binder polymer in addition to the binder polymer containing the carboxyl group. The adhesive binder polymer can be any substance capable of adhering the electrode active material layer and the separation membrane, but it is preferable to use an aqueous binder polymer.

[0050] For example, the adhesive binder polymer may include styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropyl cellulose, and diacetylcellulose, or two or more of these.

[0051] Furthermore, the electrode active material layer may further contain substances used in the manufacture of the electrode active material layer, in addition to the electrode active material and the binder polymer. For example, it may further contain additives commonly used in the art to which the present invention belongs, such as solvents, conductive materials, and thickeners.

[0052] In the present invention, the separation membrane comprises a porous substrate and an inorganic coating layer formed on at least one surface of the substrate. The separation membrane can be inserted between a negative electrode and a positive electrode to physically and electrically separate the two electrodes, interrupt internal short circuits, provide a passage for ion movement, and impregnate an electrolyte.

[0053] The porous substrate is not limited as long as it has a pore structure. For example, porous polymer films or laminated structures of two or more layers made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer can be used, and ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used.

[0054] The inorganic coating layer is located on at least one or both sides of the porous substrate and contains a binder polymer and inorganic particles. A separation film equipped with such an inorganic coating layer has excellent electrical insulation properties and can suppress short circuits. Even if a short circuit occurs, the expansion of the short-circuited area is suppressed, thereby improving the safety of the battery.

[0055] The inorganic coating layer has porous properties due to pores formed by interstitial volumes between inorganic particles. The interstitial volume refers to the space limited by inorganic particles that are substantially in contact with each other in a packed structure of inorganic particles.

[0056] The inorganic particles serve two purposes: to form micropores by enabling the creation of spaces between them, and to act as a kind of spacer that maintains their physical form. As a result, they possess excellent heat resistance, as their physical properties do not change even at high temperatures of 200°C or higher.

[0057] In the present invention, the inorganic particles include boehmite. As described above, the boehmite can form a covalent bond through a condensation reaction with a binder polymer containing carboxyl groups contained in the electrode active material layer. In particular, boehmite can exhibit chemical and mechanical properties suitable for battery use, and because it contains a large amount of hydroxyl groups (-OH), it is more advantageous for forming a condensation reaction with a binder polymer containing carboxyl groups.

[0058] In the present invention, the inorganic coating layer may further contain inorganic particles other than boehmite, and the further inorganic particles are not particularly limited as long as they are electrochemically stable, and are not particularly limited as long as they are inorganic particles that do not undergo oxidation and / or reduction reactions within the operating voltage range of the battery (for example, 0 to 5V based on Li / Li+).

[0059] The thickness of the inorganic coating layer may be in the range of 20% to 50% or 20% to 30% of the thickness of the separation membrane. By forming the inorganic coating layer within this range, the heat resistance of the separation membrane is improved, and the formation of a condensation reaction with the binder polymer containing carboxyl groups in the electrode active material layer becomes more favorable, thereby improving the mechanical properties of the electrode and the battery life.

[0060] In the present invention, the binder polymer contained in the inorganic coating layer of the separation membrane is not particularly limited, as long as it is capable of providing binding force between inorganic particles and binding force between the inorganic coating layer and the electrode.

[0061] Next, an aqueous solvent is sprayed onto the surface of the electrode active material layer (S20).

[0062] By spraying an aqueous solvent onto the surface of the electrode active material layer, the carboxyl groups contained in the binder polymer present on the surface of the electrode active material layer can be activated. Specifically, on the surface of the electrode active material layer, the carboxyl groups contained in the binder polymer form carboxyl group bonds between or within the binder polymers. When an aqueous solvent is sprayed, at least some of the carboxyl groups form hydrogen bonds with the sprayed aqueous solvent and detach from the surface of the electrode active material layer. That is, the carboxyl groups detached from the surface of the electrode active material layer become activated and capable of condensation reactions with the hydroxyl groups of boehmite. The bond between the binder polymer of the electrode active material layer and boehmite acts as a buffer against volume changes in the electrode active material that occur during charging and discharging. This allows the electrode structure to be maintained for a long period of time, improving capacity retention and rate characteristics, and exhibiting excellent adhesion, thereby improving the mechanical properties and lifespan characteristics of the electrode.

[0063] On the other hand, in an electrode and separation membrane structure like the present invention, if an aqueous solvent is sprayed onto one side of the separation membrane rather than the surface of the electrode active material layer to activate it, the binder polymer present on the surface of the electrode active material layer is exposed to the aqueous solvent for a short time. As a result, the binder polymer is not sufficiently activated, making it difficult to expect the effects described in the present invention.

[0064] According to one embodiment of the present invention, step S20 may involve spraying an aqueous solvent at about 20°C to 30°C, specifically 25°C, onto at least a portion of the surface of the electrode active material layer.

[0065] Furthermore, according to one embodiment of the present invention, step S20 may involve spraying an aqueous solvent in a mist form onto at least a portion of the surface of the electrode active material layer for about 1 to 10 seconds, specifically, about 1 to 3 seconds.

[0066] By spraying an aqueous solvent onto the surface of the electrode active material layer at the temperatures and / or times described above, at least some of the carboxyl groups located on the surface of the electrode active material layer can form hydrogen bonds with the aqueous solvent.

[0067] The type of the aqueous solvent is not limited as long as it can activate the binder polymer containing a carboxy group already applied to the electrode active material layer. For example, the aqueous solvent may contain water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, diethylene glycol, tripropylene glycol, or a mixture of two or more of these. Desirably, the aqueous solvent may be water. At this time, the water may be deionized water (D.I water) from which impurities have been removed.

[0068] Next, the surface of the active material layer in step S20 and the inorganic coating layer of the separator are laminated so as to face each other to produce an electrode assembly including an electrode and a separator (S30).

[0069] The lamination is performed in a state where a laminated structure is formed with a separator interposed between the electrodes, and the laminated structure is laminated to produce an electrode assembly. In a specific embodiment of the present invention, the electrode assembly may be arranged in a negative electrode / separator / positive electrode structure. The lamination process is a process of adhering the electrodes to the separator. If the electrodes and the separator are adhered excessively, the wettability of the electrodes and the separator decreases, inducing a decrease in the air permeability of the separator. If the electrodes and the separator are adhered too weakly, there is a risk of an increase in the resistance of the secondary battery and a decrease in workability. Therefore, it is desirable to maintain the adhesive force at an appropriate temperature and pressure to improve the interfacial characteristics between the electrode and the separator. In this regard, the lamination can be performed under a pressure of 1 kgf / cm 2 ~10 kgf / cm 2 at a temperature of 50°C to 130°C.

[0070] Next, the electrode assembly in step S30 is dried (S40).

[0071] In the present invention, drying the electrode assembly promotes the condensation reaction between the carboxyl groups contained in the binder polymer of the electrode active material layer and the hydroxyl groups of boehmite contained in the inorganic coating layer of the separation membrane, making it possible to form more covalent bonds.

[0072] The drying can be performed under vacuum conditions at a temperature of 90°C to 130°C. By drying under the conditions described above, water, which is a product of the condensation reaction between carboxyl groups and hydroxyl groups, can be removed, further promoting the condensation reaction and enabling the formation of more covalent bonds. Therefore, the adhesion between the electrode and the separation membrane is improved, and the battery life is improved by improving the capacity retention rate and rate characteristics.

[0073] A secondary battery manufactured by the manufacturing method of the present invention described above may have a -COO- bond formed at the interface between the separation membrane and the electrode by a condensation reaction. Specifically, it can be confirmed that a -COO- bond has been formed at the interface between the separation membrane and the electrode inside the secondary battery by analytical or measurement methods such as X-ray photoelectron spectroscopy (XPS) or Raman spectroscopy.

[0074] The present invention will be described in detail below with reference to Figure 2 and the examples. However, the drawings and examples of the present invention are modifiable to a variety of other forms and should not be construed as limiting the scope of the present invention to the drawings and examples. The drawings and examples of the present invention are provided to give a more complete explanation of the present invention to a person of average skill in the art.

[0075] For example, referring to Figure 2, a method for manufacturing a secondary battery according to one embodiment of the present invention is described. The electrode, which has an electrode active material layer, is unwinded from the electrode roll 100 and moves at a constant speed on a conveyor. Before the electrode and the separation membrane are laminated, an aqueous solvent is sprayed onto the surface of the electrode active material layer by a spraying device 200. Next, the surface of the electrode active material layer and the separation membrane unwinded from the separation membrane roll 300, specifically the inorganic coating layer of the separation membrane, are laminated face to face. After that, the electrode assembly is manufactured by laminating through a laminating device 400, specifically a heater chamber 410 and rollers 420, and the electrode assembly can be dried through a drying device 500.

[0076] A specific embodiment of the present invention is described below.

[0077] 1) Manufacturing of the negative electrode A negative electrode based on an aqueous binder was manufactured by mixing a negative electrode active material, an aqueous binder, and SBR in a weight ratio of 97.5:1:1.5.

[0078] The negative electrode active material includes graphite and Si-based negative electrode material (pure silicon (pure-Si), SiO, SiOx, SiC), and the aqueous binder includes carboxymethylcellulose (CMC) and polyacrylic acid (PAA).

[0079] 2) Manufacturing of the positive electrode The positive electrode was manufactured by mixing the positive electrode active material, PVDF binder, and conductive material in a weight ratio of 97:1.5:1.5. The positive electrode active material contained LCO and NCM, and the conductive material contained Ketjenblack and Super P.

[0080] 3) Manufacturing of separation membranes A separation membrane with an inorganic coating layer was manufactured by applying a slurry prepared by adding PVDF as a binder polymer and boehmite (particle size: 0.2 μm) as inorganic particles in a weight ratio of 5:95 to the solvent NMP (N-methyl-2-pyrrolidone) to a porous polyethylene substrate (thickness: approximately 9 μm, porosity: approximately 40% to 45%) and drying the slurry.

[0081] 4) Manufacturing of secondary batteries The surface of the negative electrode active material layer of the negative electrode manufactured in 1) above was sprayed with pure water from which impurities had been removed, thereby activating the binder polymer that appeared on the surface of the negative electrode active material layer.

[0082] Subsequently, the separation membrane described in 3) above is interposed between the manufactured negative electrode and positive electrode to produce an electrode assembly, which is then heated at a temperature of 50°C to 130°C and subjected to a pressure of 1 kgf / cm². 2 ~10 kgf / cm² 2 The secondary battery was manufactured by laminating under pressure and then vacuum drying at a temperature of 90°C to 130°C.

Claims

1. (S10) A step of preparing an electrode comprising an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separation membrane comprising a porous substrate and an inorganic coating layer formed on at least one surface of the porous substrate, (S20) A step of spraying an aqueous solvent onto the surface of the electrode active material layer, (S30) A step of manufacturing an electrode assembly including an electrode and a separation membrane by laminating the surface of the electrode active material layer from step S20 and the inorganic coating layer of the separation membrane so that they face each other, (S40) The step of drying the electrode assembly from step S30, The electrode active material layer comprises a binder polymer containing a carboxyl group, A method for manufacturing a secondary battery, characterized in that the separation membrane contains boehmite in its inorganic coating layer.

2. The method for manufacturing a secondary battery according to claim 1, characterized in that step S20 involves spraying an aqueous solvent at a temperature of 20°C to 30°C onto at least a portion of the surface of the electrode active material layer.

3. The method for manufacturing a secondary battery according to claim 1, characterized in that step S20 involves spraying an aqueous solvent in a mist form onto at least a portion of the surface of the electrode active material layer for 1 to 10 seconds.

4. The lamination in step S30 is carried out at a temperature of 50°C to 130°C and at a load of 1 kgf / cm². ２ ~10 kgf / cm² ２ A method for manufacturing a secondary battery according to claim 1, characterized in that it is carried out under the pressure conditions.

5. The method for manufacturing a secondary battery according to claim 1, characterized in that the drying in step S40 is performed by vacuum drying at a temperature of 90°C to 130°C.

6. A method for producing a secondary battery according to claim 1, characterized in that the hydroxyl group of the boehmite and the carboxyl group of the binder polymer undergo a condensation reaction to form a covalent bond.

7. The method for producing a secondary battery according to claim 1, characterized in that the binder polymer containing the carboxyl group is a water-dispersible or water-soluble binder polymer.

8. The method for producing a secondary battery according to claim 1, characterized in that the binder polymer containing the carboxyl group contains carboxymethylcellulose, polyacrylic acid, or any of the above.

9. A method for producing a secondary battery according to claim 1, characterized in that the electrode further comprises styrene-butadiene rubber, acrylic styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, hydroxypropyl methylcellulose, hydroxypropyl cellulose, and diacetylcellulose, or two or more adhesive binder polymers thereof.

10. The method for manufacturing a secondary battery according to claim 1, characterized in that the electrode is a negative electrode and the negative electrode active material includes a carbon-based active material and a silicon-based active material.

11. The method for producing a secondary battery according to claim 1, characterized in that the aqueous solvent includes water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, diethylene glycol, tripropylene glycol, or a mixture of two or more of these.

12. An electrode comprising an electrode active material layer, A separation membrane having an inorganic coating layer, A secondary battery that includes, The electrode active material layer comprises a binder polymer containing a carboxyl group, The separation membrane contains boehmite in the inorganic coating layer, The electrode active material layer faces the inorganic coating layer, A secondary battery characterized in that the hydroxyl group (-OH) of the boehmite and the carboxyl group (-COOH) of the binder polymer form a covalent bond.

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