Method for manufacturing a secondary battery

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] The present 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 of the contents disclosed in the specification and drawings of the application are incorporated into this application.

Background Art

[0003] As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, research on secondary batteries that can meet various requirements is actively underway. Among them, the development of rechargeable secondary batteries and lithium secondary batteries with high energy density have become the focus of interest. In recent years, secondary batteries with improved performance that ensure safety and, with the expansion or development of applications, have further improvements such as increased capacity, reduced resistance, and improved mechanical properties and productivity have been demanded.

[0004] A lithium secondary battery is composed of a positive electrode and a negative electrode, which are electrodes with active materials coated on an electrode current collector, and a porous separator interposed between the positive electrode and the negative electrode, and has a structure in which an electrolyte containing a lithium salt is impregnated in the electrode assembly. In a lithium secondary battery, lithium ions from the positive electrode active material are inserted into the negative electrode active material during charging, and move back and forth between the two electrodes while desorbing during discharging, and energy is transmitted through such a process to enable charging and discharging.

[0005] However, during charge and discharge, the active material may react with lithium ions and repeatedly expand and contract in volume, resulting in a decrease in capacity retention rate, charge-discharge efficiency, and life characteristics. Therefore, research is underway to control it by using a binder polymer contained in the active material layer. However, due to viscosity characteristics and the like, it is difficult to stably apply it to a conventional slurry system. When a large amount of binder polymer is used in the active material layer, there is a problem that it causes a decrease in battery performance such as an increase in electrode resistance and a decrease in capacity due to a decrease in initial efficiency.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above problems, and aims to provide a method for manufacturing a secondary battery that improves the mechanical performance and electrochemical performance of an electrode by inducing a covalent bond between a binder polymer in an electrode active material layer and a separator, and thereby improves the life of the battery.

[0007] Other objects and advantages of the present invention can be realized by the means and methods described in the claims and their combinations.

Means for Solving the Problems

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

[0009] According to a first embodiment, (S10) Preparing an electrode including an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separator including a porous substrate and an inorganic coating layer formed on at least one surface of the porous substrate; (S20) Spraying an aqueous solvent onto the surface of the electrode active material layer; (S30) Manufacturing an electrode assembly including an electrode and a separator by laminating and laminating the surface of the electrode active material layer in step S20 and the inorganic coating layer of the separator so as to face each other. (S40) drying the electrode assembly of step S30; The electrode active material layer contains a binder polymer containing a carboxy group. The separator relates to a method for manufacturing a secondary battery including boehmite in an inorganic coating layer.

[0010] According to a second embodiment, in the first embodiment, 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 part of the surface of the electrode active material layer.

[0011] According to a third embodiment, in the first embodiment or the second embodiment, 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 part of the surface of the electrode active material layer for 1 to 10 seconds.

[0012] According to a fourth embodiment, in any one of the first to third embodiments, The lamination in step S30 is performed under temperature conditions of 50°C to 130°C and a pressure of 1 kgf / cm 2 ~10 kgf / cm 2 relates to a method for manufacturing a secondary battery.

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

[0014] According to a sixth embodiment, in any one of the first to fifth embodiments, relates to a method for manufacturing a secondary battery in which a condensation reaction occurs between the hydroxy group of the boehmite and the carboxy group of the binder polymer to form a covalent bond.

[0015] According to a seventh embodiment, in any one of the first to sixth embodiments, The present invention relates to a method for manufacturing a secondary battery in which the binder polymer containing the 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 in which the binder polymer containing the 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 styrene-butadiene rubber, acrylated 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, 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 in which the electrode is a negative electrode and contains a carbon-based active material and a silicon-based active material as the negative electrode active material.

[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 thereof, 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 manner. Specifically, before laminating the electrode and the separator, an aqueous solvent is sprayed on 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 preferred embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention. 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

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0024] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in this specification and the claims should not be construed as being limited to ordinary or dictionary meanings. The inventor himself / herself should interpret them in accordance with the technical concept of the present invention in accordance with the principle that he / she can appropriately define the concept of the terms in order to explain the invention in the best way. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all of the technical concepts of the present invention. Thus, there may be various equivalents and modifications that can replace them at the time of this application.

[0025] Throughout the specification, when a certain part "includes" a certain component, unless otherwise specified, it does not mean excluding other components, but rather may further include other components.

[0026] Terms such as "about" and "substantially" used throughout this specification are used as meanings close to that numerical value when the inherent manufacturing and material tolerances are presented in the mentioned meaning, and are used to prevent unscrupulous infringers from misusing the disclosure content where exact or absolute numerical values are mentioned to assist in the understanding of this application.

[0027] Throughout the specification, the description of "A and / or B" means "A or B, or all of these".

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

[0029] In the present invention, a secondary battery is a device that converts chemical energy into electrical energy through an electrochemical reaction, and a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery is desirable.

[0030] The secondary battery includes an electrode assembly in which electrodes and a separator are laminated. Specifically, at least one negative electrode and at least one positive electrode can be alternately laminated with a separator interposed therebetween.

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

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

[0033] The inorganic coating layer of the separator and the electrode active material layer are laminated face to face, and a covalent bond (as a result of a condensation reaction) is formed by the reaction between the hydroxy group (-OH) of the boehmite and the carboxy group (-COOH) of the binder polymer.

[0034] Generally, the main causes of performance degradation and deterioration phenomena of electrodes include the periodic volume expansion and contraction of electrode active materials, specifically negative electrode active materials, during charge and discharge. If the volume change of the electrode active material cannot be controlled, the contact points between the electrode active materials decrease, and the life characteristics may deteriorate due to a decrease in electrical characteristics and the formation of cracks.

[0035] The method for manufacturing a secondary battery according to the present invention includes a predetermined step of spraying an aqueous solvent on the surface of the electrode active material layer, thereby inducing a predetermined chemical bond between the inorganic coating layer of the separator and the electrode active material layer, and serving as a buffer against the volume change of the electrode active material. Therefore, the mechanical performance of the electrode can be improved, and ultimately, the life of the battery can be improved.

[0036] In one embodiment of the present invention, the method for manufacturing a secondary battery is (S10) Prepare an electrode including a current collector electrode and an electrode active material layer formed on at least one surface of the current collector electrode, and a separator including a porous substrate and an inorganic coating layer formed on at least one surface of the substrate. (S20) Spray an aqueous solvent onto the surface of the electrode active material layer. (S30) Manufacture an electrode assembly including the electrode and the separator by laminating and laminating the surface of the electrode active material layer in step S20 and the inorganic coating layer of the separator so that they face each other. (S40) Dry the electrode assembly in step S30.

[0037] Hereinafter, each step will be specifically described.

[0038] First, prepare an electrode including a current collector electrode and an electrode active material layer formed on at least one surface of the current collector electrode, and a separator including a porous substrate and an inorganic coating layer formed on at least one surface of the substrate (step S10).

[0039] At this time, the electrode active material layer contains a binder polymer containing a carboxy group, and the separator contains boehmite in the inorganic coating layer.

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

[0041] The current collector electrode 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, fired carbon, or a surface-treated material with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used.

[0042] When the electrode is a negative electrode, the electrode active material layer contains 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 may 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. Any one or a mixture of two or more of these can be used. In addition, 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 carbon includes soft carbon and hard carbon, and representative high-crystalline carbon includes 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 carbon such as petroleum or coal tar pitch-derived cokes.

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

[0045] The binder polymer includes a binder polymer containing a carboxy group.

[0046] The binder polymer containing a carboxy group can form a covalent bond by a condensation reaction with boehmite contained in the separation membrane described later. Further, in the binder polymer containing a carboxy group, at least a part of the carboxy groups of the binder polymer located on the surface of the electrode active material layer are activated by hydrogen bonding with an aqueous solvent by spraying the aqueous solvent on the surface of the electrode active material layer described later, and the carboxy groups of the activated binder polymer can improve the mechanical properties and life characteristics of the electrode by forming a covalent bond with boehmite in a subsequent process.

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

[0048] The water-dispersible binder polymer may be, for example, polyacrylic acid, the water-soluble binder polymer may be carboxymethyl cellulose, or the water-dispersible binder polymer and the water-soluble binder polymer may be used in combination.

[0049] In addition to the binder polymer containing the carboxy group, the electrode active material layer may further contain an adhesive binder polymer. The adhesive binder polymer can be used without limitation as long as it can adhere the electrode active material layer and the separator, but it is desirable to use an aqueous binder polymer.

[0050] For example, the adhesive binder polymer may include styrene-butadiene rubber, acrylated 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, phenol resin, epoxy resin, polyvinyl alcohol, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, and diacetyl cellulose, or may include two or more of these.

[0051] Further, the electrode active material layer may further contain substances used in the production 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 technical field to which the present invention pertains, such as solvents, conductive materials, thickeners, etc.

[0052] In the present invention, the separator includes a porous substrate and an inorganic coating layer formed on at least one surface of the substrate. By being inserted between the negative electrode and the positive electrode, the separator can physically and electrically separate both electrodes to block internal short circuits, provide a migration path for ions, and play a role in impregnating the electrolyte.

[0053] The porous substrate is not limited as long as it has a structure with pores. For example, a porous polymer film made from polyolefin-based polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof can be used, and a normal porous nonwoven fabric, for example, a nonwoven fabric made of high-melting glass fibers, polyethylene terephthalate fibers, etc. can be used.

[0054] The inorganic coating layer is located on at least one surface or both surfaces of the porous substrate and contains a binder polymer and inorganic particles. A separator provided 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 region is suppressed, thereby improving the safety of the battery.

[0055] The inorganic coating layer has porous characteristics due to pores formed by the interstitial volume between inorganic particles. The interstitial volume means a space limited by inorganic particles that are substantially in contact in the filling structure of inorganic particles.

[0056] The inorganic particles serve to form fine pores by enabling the formation of spaces between the inorganic particles and also serve as a kind of spacer to maintain the physical form. Since they have the property that their physical properties do not change even at a high temperature of usually 200 °C or higher, they have excellent heat resistance.

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

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

[0059] The thickness of the inorganic coating layer can be in the range of 20% to 50%, or 20% to 30% with respect to the thickness of the separator. By forming the thickness of the inorganic coating layer within the above range, the heat resistance of the separator is improved, and it is advantageous for forming a condensation reaction with a binder polymer containing a carboxy group in the electrode active material layer, and the mechanical properties of the electrode and the life of the battery can be improved.

[0060] In the present invention, the binder polymer contained in the inorganic coating layer of the separator is not particularly limited as long as it can provide the binding force between the inorganic particles and the 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 on the surface of the electrode active material layer, the carboxy 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 carboxy groups contained in the binder polymer form carboxy group bonds between or within the binder polymers. However, when an aqueous solvent is sprayed, at least some of the carboxy groups form hydrogen bonds with the sprayed aqueous solvent and become detached from the surface of the electrode active material layer. That is, the carboxy groups detached from the surface of the electrode active material layer are in an activated state capable of undergoing a condensation reaction with the hydroxy groups of boehmite. The bond between the binder polymer of the electrode active material layer and boehmite serves as a buffer against the volume change of the electrode active material that occurs during charge and discharge. Therefore, the structure of the electrode can be maintained for a long period, the capacity retention rate and rate characteristics can be improved, and excellent adhesive strength can be exhibited, thereby improving the mechanical properties and lifespan characteristics of the electrode.

[0063] On the other hand, in the structure of the electrode and separator membrane as in the present invention, when activating by spraying an aqueous solvent or the like on one surface of the separator membrane rather than on the surface of the electrode active material layer, since the time for the binder polymer present on the surface of the electrode active material layer to be exposed to the aqueous solvent is short, the activation of the binder polymer is not sufficiently carried out, and thus it is difficult to expect the effects as in the present invention.

[0064] According to an embodiment of the present invention, in step S20, an aqueous solvent at about 20°C to 30°C, specifically 25°C, can be sprayed on at least a part of the surface of the electrode active material layer.

[0065] Also, according to an embodiment of the present invention, in step S20, an aqueous solvent can be sprayed in a mist form on at least a part of the surface of the electrode active material layer for about 1 second to 10 seconds, specifically about 1 second to 3 seconds.

[0066] By spraying an aqueous solvent on the surface of the electrode active material layer at the temperature and / or time as described above, at least some of the carboxy 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 the step S20 and the inorganic coating layer of the separation membrane are laminated so as to face each other to produce an electrode assembly including an electrode and a separation membrane (S30).

[0069] The lamination is performed in a state where a laminated structure is formed with a separation membrane 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 / separation membrane / positive electrode structure. The lamination process is a process of adhering the electrode to the separation membrane. When the electrode and the separation membrane are overly adhered, the wettability of the electrode and the separation membrane decreases, inducing a decrease in the air permeability of the separation membrane. When the electrode and the separation membrane are overly weakly adhered, 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 separation membrane. 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 the step S30 is dried (S40).

[0071] In the present invention, by drying the electrode assembly, the condensation reaction between the carboxy groups contained in the binder polymer of the electrode active material layer and the hydroxy groups of boehmite contained in the inorganic coating layer of the separator is promoted, and it is possible to form more covalent bonds.

[0072] The drying can be carried out by vacuum drying in a vacuum atmosphere at a temperature of 90°C to 130°C. By drying under the above-mentioned conditions, water, which is a product of the condensation reaction between carboxy groups and hydroxy groups, can be removed, so that the condensation reaction is further promoted and it is possible to form more covalent bonds. Therefore, the adhesion between the electrode and the separator is improved, and the battery life is improved by improving the capacity retention rate and rate characteristics.

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

[0074] Hereinafter, the present invention will be specifically described in detail with reference to FIG. 2 and Examples. However, the drawings and examples according to the present invention can be changed into other various forms, and the scope of the present invention should not be construed as being limited to the drawings and examples. The drawings and examples of the present invention are provided to more fully explain the present invention to those having average knowledge in the art.

[0075] For example, referring to FIG. 2, a method for manufacturing a secondary battery according to an embodiment of the present invention will be described. The electrode having the electrode active material layer is unwound from the electrode roll 100 and moves on the conveyor at a constant speed. Before the electrode and the separator 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 separator unwound from the separator roll 300, specifically, the inorganic coating layer of the separator are laminated face to face. Thereafter, an electrode assembly is manufactured by laminating through a laminating device 400, specifically, a heater chamber 410 and a roller 420, and the electrode assembly can be dried through a drying device 500.

[0076] Specifically, an example according to the present invention will be described as follows.

[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 at a weight ratio of 97.5:1:1.5.

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

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

[0080] 3) Manufacturing of the separator A slurry was prepared by adding PVDF as a binder polymer and boehmite (particle size: 0.2 μm) as inorganic particles to a polyethylene porous substrate (thickness: about 9 μm, porosity: about 40% - 45%) at a weight ratio of 5:95 to NMP (N-methyl-2-pyrrolidone) as a solvent, and the slurry was coated and dried to manufacture a separator having an inorganic coating layer.

[0081] 4) Manufacture of secondary battery Pure water from which impurities had been removed was sprayed onto the surface of the negative electrode active material layer of the negative electrode manufactured in the above 1), and the binder polymer that appeared on the surface of the negative electrode active material layer was activated.

[0082] Thereafter, a separator membrane of the above 3) was interposed between the manufactured negative electrode and positive electrode to manufacture an electrode assembly, which was heated at a temperature of 50°C to 130°C and pressed at a pressure of 1 kgf / cm 2 to 10 kgf / cm 2 to perform lamination, and vacuum drying was performed at a temperature of 90°C to 130°C to manufacture a secondary battery.

Claims

1. (S10) preparing an electrode including a current collector electrode and an electrode active material layer formed on at least one surface of the current collector electrode, and a separator including a porous substrate and an inorganic coating layer formed on at least one surface of the porous substrate; (S20) spraying an aqueous solvent onto the surface of the electrode active material layer; (S30) manufacturing an electrode assembly including the electrode and the separator by laminating and laminating the surface of the electrode active material layer in step S20 and the inorganic coating layer of the separator so as to face each other; (S40) drying the electrode assembly in step S30, wherein the electrode active material layer includes a binder polymer containing a carboxy group, wherein the separator contains boehmite in the inorganic coating layer, a method for manufacturing a secondary battery.

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

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

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

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

6. The method for manufacturing a secondary battery according to claim 1, characterized in that a condensation reaction occurs between the hydroxy group of the boehmite and the carboxy group of the binder polymer to form a covalent bond.

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

8. The method for manufacturing a secondary battery according to claim 1, characterized in that the binder polymer containing a carboxy group contains carboxymethyl cellulose, polyacrylic acid, or both.

9. The manufacturing method of the secondary battery according to claim 1, characterized in that the electrode further comprises styrene-butadiene rubber, acrylated 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, hydroxypropylmethyl cellulose, hydroxypropyl cellulose and diacetyl cellulose, or an adhesive binder polymer of two or more of these.

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

11. The manufacturing method of the secondary battery according to claim 1, characterized in that the aqueous solvent contains 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. A secondary battery, characterized in that it is manufactured by the manufacturing method according to any one of claims 1 to 11.

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