Manufacturing method of secondary battery

Abstract

The present invention relates to a method for manufacturing a secondary battery, wherein, prior to laminating the electrode and the separator, an aqueous solvent is sprayed onto the surface of the electrode active material layer to activate the electrode active material layer. As a result, the adhesion between the electrode and the separator can be improved, and the capacity retention rate and rate characteristics are improved, thereby improving the lifespan of the battery.

Description

Technology Field

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

[0002] This application is a priority claim application for Korean Patent Application No. 10-2022-0151646 filed on November 14, 2022, and all contents disclosed in the specification of said application are incorporated into this application by reference. Background Technology

[0004] With the increasing technological development and demand for mobile devices, the demand for rechargeable batteries as an energy source is rapidly rising, and consequently, extensive research is being conducted on batteries capable of meeting various requirements. Among these, the development of rechargeable batteries and lithium-ion batteries with high energy density have become the focus of attention. Recently, there is a demand for rechargeable batteries with further improved performance—such as increased capacity, reduced resistance, enhanced mechanical properties, and improved productivity—to ensure safety and support the expansion and advancement of applications.

[0005] A lithium secondary battery is structured such that an electrolyte containing a lithium salt is impregnated into an electrode assembly comprising a positive electrode and a negative electrode, each having an active material coated on an electrode current collector, and a porous separator interposed between the positive and negative electrodes. In a lithium secondary battery, lithium ions released from the positive active material are inserted into the negative active material during charging and subsequently detach during discharge, circulating back and forth between the two electrodes; this process transfers energy, thereby enabling charging and discharging.

[0006] However, active materials repeatedly expand and contract in volume as they react with lithium ions during charging and discharging, which can lead to a decrease in capacity retention rate, charge / discharge efficiency, and lifespan characteristics. Accordingly, research is being conducted to control this using binder polymers included in the active material layer, but it is difficult to apply them stably to existing slurry systems due to viscosity characteristics, and when a large amount of binder polymer is used in the active material layer, there are problems that cause a decrease in battery specifications, such as increased electrode resistance and reduced capacity due to decreased initial efficiency. The problem to be solved

[0008] The present invention was devised to solve the problems of the prior art described above, and aims to provide a method for manufacturing a secondary battery that improves the mechanical and electrochemical performance of the electrode and further improves the battery life by inducing covalent bonding between the binder polymer of the electrode active material layer and the separator.

[0009] It will be readily apparent that other objects and advantages of the present invention can be realized by means or methods described in the claims and combinations thereof. means of solving the problem

[0011] The inventors have discovered that the above problem can be solved through the following method for manufacturing a secondary battery.

[0012] According to the first embodiment,

[0013] (S10) A step of preparing an electrode having an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separator having a porous substrate and an inorganic coating layer formed on at least one surface of the substrate;

[0014] (S20) A step of spraying a water-based solvent onto the surface of the electrode active material layer;

[0015] (S30) A step of manufacturing an electrode assembly including an electrode and a separator by laminating the surface of the electrode active material layer of (S20) and the inorganic coating layer of the separator facing each other; and

[0016] (S40) A step of drying the electrode assembly of (S30); comprising,

[0017] The above electrode active material layer comprises a binder polymer containing carboxyl groups, and

[0018] The present invention relates to a method for manufacturing a secondary battery in which the separator comprises boehmite in an inorganic coating layer.

[0019] According to the second embodiment, in the first embodiment,

[0020] The above (S20) relates to a method for manufacturing a secondary battery, wherein an aqueous solvent at a temperature of 20 to 30°C is sprayed onto at least a portion of the surface of the electrode active material layer.

[0021] According to the third embodiment, in the first embodiment or the second embodiment,

[0022] The above (S20) relates to a method for manufacturing a secondary battery, wherein an aqueous solvent is sprayed in the form of a mist for 1 to 10 seconds onto at least a portion of the surface of the electrode active material layer.

[0023] According to the fourth embodiment, in any one of the first to third embodiments,

[0024] The lamination of the above (S30) is performed at a temperature of 50℃ to 130℃, 1 kgf / cm² 2 up to 10 kgf / cm² 2 This relates to a method for manufacturing a secondary battery, which is performed under pressure conditions.

[0025] According to the fifth embodiment, in any one of the first to fourth embodiments,

[0026] The above (S40) relates to a method for manufacturing a secondary battery in which vacuum drying is performed at a temperature of 90 to 130°C.

[0027] According to the 6th embodiment, in any one of the 1st to 5th embodiments,

[0028] The present 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.

[0029] According to the seventh embodiment, in any one of the first to sixth embodiments,

[0030] The present invention relates to a method for manufacturing a secondary battery in which the binder polymer containing the above-mentioned carboxyl group is a water-dispersible or water-soluble binder polymer.

[0031] According to the eighth embodiment, in any one of the first to seventh embodiments,

[0032] The present invention relates to a method for manufacturing a secondary battery in which the binder polymer containing the above-mentioned carboxyl group comprises carboxymethylcellulose, polyacrylic acid, or both.

[0033] According to the ninth embodiment, in any one of the first to eighth embodiments,

[0034] The present invention relates to a method for manufacturing a secondary battery, wherein the electrode further comprises an adhesive binder polymer comprising 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, hydroxypropylmethylcellulose, hydroxypropylcellulose and diacetylcellulose, or two or more of these.

[0035] According to the 10th embodiment, in any one of the 1st to 9th embodiments,

[0036] The present invention relates to a method for manufacturing a secondary battery in which the electrode is a negative electrode and the negative electrode active material comprises a carbon-based active material and a silicon-based active material.

[0037] According to the 11th embodiment, in any one of the 1st to 10th embodiments,

[0038] The present invention relates to a method for manufacturing a secondary battery, wherein the above-mentioned aqueous solvent comprises 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.

[0039] According to the 12th embodiment, the invention relates to a secondary battery manufactured by a manufacturing method of any one of the 1st to 11th embodiments. Effects of the invention

[0041] The method for manufacturing a secondary battery according to the present invention can improve the mechanical performance and electrochemical performance of the electrode in a simpler way. Specifically, by spraying an aqueous solvent onto the electrode active material layer before laminating the electrode and the separator to activate the electrode active material layer, the adhesion between the electrode and the separator can be improved, and the capacity retention rate and rate characteristics can be improved, thereby improving the lifespan of the battery. Brief explanation of the drawing

[0043] The drawings attached to this specification illustrate preferred embodiments of the present invention and serve to help to better understand the technical concept of the present invention together with the description of the invention above; therefore, the present invention is not to be interpreted as being limited only to the matters described in such drawings. Meanwhile, the shape, size, scale, or ratio of elements in the drawings included in this specification may be exaggerated to emphasize a clearer explanation. FIG. 1 is a process flow diagram illustrating a method for manufacturing a secondary battery according to one embodiment of the present invention. FIG. 2 schematically illustrates a process for manufacturing a secondary battery according to one embodiment of the present invention. Figure 3 shows the chemical structure of boehmite and binder polymers and their condensation reaction. Specific details for implementing the invention

[0044] The present invention will be described in detail below. Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely one preferred embodiment of the present invention and do not represent all of the technical spirit of the present invention; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0046] Throughout this specification, when a part is described as "include(s) or comprise(s)" a component, unless specifically stated otherwise, this means that it does not exclude other components but may include additional components.

[0048] Additionally, terms such as “about,” “substantially,” as used throughout this specification, are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the stated meaning, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which precise or absolute values ​​are mentioned to aid in understanding this invention.

[0050] Throughout this specification, the description “A and / or B” means “A or B or both.”

[0052] The present invention relates to a method for manufacturing a secondary battery.

[0053] In the present invention, the 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 preferred.

[0054] The above secondary battery includes an electrode assembly in which electrodes and a separator are stacked, and specifically, at least one negative electrode and at least one positive electrode may be alternately stacked with the separator as a boundary.

[0055] 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 separator comprises a porous substrate and an inorganic coating layer formed on at least one surface of the substrate.

[0056] The above electrode active material layer comprises a binder polymer containing carboxyl groups as a binder resin, and the above inorganic coating layer comprises boehmite.

[0057] The inorganic coating layer of the above-mentioned separator 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).

[0059] Generally, the primary cause of electrode performance degradation and deterioration 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 are not controlled, the contact points between the materials decrease, which can lead to reduced electrical characteristics and the formation of cracks, thereby degrading lifespan characteristics.

[0060] 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 an electrode active material layer, thereby inducing a predetermined chemical bond between the inorganic coating layer of the separator and the electrode active material layer, which can act as a buffer against volume changes of the electrode active material, thus improving the mechanical performance of the electrode and further improving the lifespan of the battery.

[0062] In one embodiment of the present invention, a method for manufacturing a secondary battery

[0063] (S10) A step of preparing an electrode having an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separator having a porous substrate and an inorganic coating layer formed on at least one surface of the substrate;

[0064] (S20) A step of spraying a water-based solvent onto the surface of the electrode active material layer;

[0065] (S30) A step of manufacturing an electrode assembly including an electrode and a separator by laminating the surface of the electrode active material layer of (S20) and the inorganic coating layer of the separator facing each other; and

[0066] (S40) A step of drying the electrode assembly of (S30); includes.

[0068] Below, each step is explained in detail.

[0070] First, an electrode having an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separator having a porous substrate and an inorganic coating layer formed on at least one surface of the substrate are prepared (S10).

[0071] At this time, the electrode active material layer includes a binder polymer containing carboxyl groups, and the separator includes boehmite in the inorganic coating layer.

[0073] 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, and the electrode active material layer comprises an electrode active material and a binder polymer. The electrode can be manufactured by applying a slurry comprising an electrode active material and a binder polymer to an electrode current collector according to a conventional method known in the art.

[0074] The above electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the secondary battery, and for example, stainless steel, copper, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used.

[0075] The electrode active material layer may include a negative electrode active material when the electrode is a negative electrode, and may include a positive electrode active material when the electrode is a positive electrode.

[0076] For example, the above-mentioned negative electrode active material may be a compound capable of reversible intercalation and deintercalation of lithium. 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); metal-based compounds capable of alloying 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 dedoping lithium such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above-mentioned metal-based compounds and carbon-based active materials such as Si-C composites or Sn-C composites, and any one or more of these may be used. Additionally, a metallic lithium thin film may be used as the above-mentioned negative electrode active material. Furthermore, both low-crystallinity carbon and high-crystallinity carbon may be used as the carbon-based active material. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial 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.

[0077] For example, the above-mentioned positive electrode active material is a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; chemical formula Li 1+x Mn 2-xLithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M x Lithium nickel oxide represented by O2 (where M = one or more 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 Examples include lithium manganese complex oxides represented by 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, but are not limited to these.

[0079] The above binder polymer includes a binder polymer containing carboxyl groups.

[0080] The binder polymer containing the above-mentioned carboxyl groups can form covalent bonds by undergoing a condensation reaction with boehmite included in the separator to be described later. Additionally, by spraying an aqueous solvent onto the surface of the electrode active material layer to be described later, at least some of the carboxyl groups of the binder polymer located on the surface of the active material layer are activated through hydrogen bonding with the aqueous solvent. The activated carboxyl groups of the binder polymer can then form covalent bonds with boehmite in a subsequent process, thereby helping to improve the mechanical properties and lifespan characteristics of the electrode.

[0081] 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 does not dissolve in a water-based solvent when added to a water-based solvent but has at least a portion of dispersibility, and the water-soluble binder polymer is a polymer that dissolves at least a portion when added to a water-based solvent.

[0082] The above water-dispersible binder polymer may be, for example, polyacrylic acid, and the above water-soluble binder polymer may be carboxymethyl cellulose, and the above water-dispersible binder polymer and the water-soluble binder polymer may be used in combination.

[0083] In addition, the electrode active material layer may further include an adhesive binder polymer in addition to the binder polymer containing carboxyl groups. The adhesive binder polymer may be used without limitation as long as it is a material capable of adhering the electrode active material layer and the separator, but it is preferable to use a water-based binder polymer.

[0084] For example, it 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, phenolic resin, epoxy resin, polyvinyl alcohol, hydroxypropylmethylcellulose, hydroxypropylcellulose and diacetylcellulose, or two or more of these.

[0085] In addition, the electrode active material layer may further include materials used to manufacture the electrode active material layer in addition to the electrode active material and the binder polymer. For example, it may further include additives commonly used in the technical field to which the present invention belongs, such as solvents, conductive materials, and thickeners.

[0087] In the present invention, the separator comprises a porous substrate and an inorganic coating layer formed on at least one surface of the substrate. The separator is inserted between the cathode and the anode to physically and electrically separate the two electrodes to prevent internal short circuits, provide a pathway for ion movement, and impregnate an electrolyte.

[0088] The above porous substrate is not limited to any structure having pores. For example, a porous polymer film made of a polyolefin-based polymer 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 may be used, and a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc. may also be used.

[0089] The above inorganic coating layer may be located on at least one or both surfaces of the porous substrate and comprises a binder polymer and inorganic particles. A separator 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.

[0090] The above-mentioned inorganic coating layer has porous characteristics due to pores formed by the interstitial volume between inorganic particles. The interstitial volume refers to the space defined by the inorganic particles that are substantially in contact within the packing structure of the inorganic particles.

[0091] The above inorganic particles enable the formation of empty spaces between the inorganic particles, thereby serving as a type of spacer that forms micropores and maintains a physical shape. Generally, they possess excellent heat resistance because their physical properties do not change even at high temperatures of 200°C or higher.

[0093] In the present invention, the inorganic particles include boehmite. As described above, the boehmite can form a covalent bond by condensing with a binder polymer containing carboxyl groups included in the electrode active material layer. In particular, boehmite can exhibit chemical and mechanical properties suitable for battery use and, at the same time, contains a large amount of hydroxyl groups (-OH), making it more advantageous to form a condensation reaction with a binder polymer containing carboxyl groups.

[0094] In the present invention, the inorganic coating layer may additionally include inorganic particles other than boehmite, and the inorganic particles that may additionally include 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 in the operating voltage range of the battery (e.g., 0 to 5 V based on Li / Li+).

[0095] The thickness of the inorganic coating layer may be in the range of 20% to 50% or 20% to 30% relative 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 at the same time, it is advantageous to form a condensation reaction with a binder polymer containing carboxyl groups of the electrode active material layer, thereby improving the mechanical properties of the electrode and the lifespan of the battery.

[0096] In the present invention, the binder polymer included in the inorganic coating layer of the separator 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.

[0098] Next, a water-based solvent is sprayed onto the surface of the electrode active material layer (S20).

[0099] 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, the carboxyl groups contained in the binder polymer on the surface of the electrode active material layer form carboxyl group bonds between or within the binder polymers; however, 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 reach an activated state capable of undergoing a condensation reaction with the hydroxyl groups of boehmite. The bonding between the binder polymer of the electrode active material layer and boehmite can act as a buffer against volume changes of the electrode active material that occur during charging and discharging, thereby maintaining the structure of the electrode for a long period, which can improve capacity retention rate and rate characteristics. Additionally, since excellent adhesion can be exhibited, it can help improve the mechanical properties and lifespan characteristics of the electrode.

[0100] On the other hand, in the structure of the electrode and separator as in the present invention, if activation is attempted by spraying an aqueous solvent or the like onto one side of the separator rather than the surface of the electrode active material layer, the binder polymer present on the surface of the electrode active material layer is exposed to the aqueous solvent for a short time; consequently, sufficient activation of the binder polymer is not achieved, making it difficult to expect the same effect as in the present invention.

[0102] According to one embodiment of the present invention, the above (S20) may spray an aqueous solvent at a temperature of about 20 to 30°C, specifically 25°C, onto at least a portion of the surface of the electrode active material layer.

[0103] In addition, according to one embodiment of the present invention, the above (S20) may spray an aqueous solvent in the form of a mist on 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.

[0104] By spraying an aqueous solvent onto the surface of the electrode active material layer while satisfying the temperature and / or time as presented 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.

[0105] The above-mentioned aqueous solvent is not limited in type as long as it can activate the binder polymer containing carboxyl groups already coated on the electrode active material layer. For example, the above-mentioned aqueous solvent may include 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. Preferably, the above-mentioned aqueous solvent may be water, wherein the water may be deionized water (DI water) from which impurities have been removed.

[0107] Next, the surface of the active material layer of the above (S20) and the inorganic coating layer of the separator are laminated facing each other to manufacture an electrode assembly including an electrode and a separator (S30).

[0108] The above lamination is performed in a state where a laminated structure is formed by interposing a separator between electrodes, and an electrode assembly is manufactured by laminating the laminated structure. In a specific embodiment of the present invention, the electrode assembly may be arranged in a negative electrode / separator / anode structure. The lamination process is a process of bonding the electrode to the separator; if the electrode and the separator are bonded too excessively, it causes a decrease in the wettability of the electrode and the separator and a decrease in the air permeability of the separator, and if the electrode and the separator are bonded too weakly, there is a concern that the resistance of the secondary battery will increase and processability will be reduced. Therefore, it is desirable to maintain adhesion at appropriate temperature and pressure and to improve the interfacial characteristics between the electrode and the separator. In this regard, the lamination is performed at a temperature of 50°C to 130°C and 1 kgf / cm² 2 up to 10 kgf / cm² 2 It can be performed under pressure.

[0110] Next, the electrode assembly of the above (S30) is dried (S40).

[0111] In the present invention, by drying the electrode assembly, the condensation reaction between the carboxyl groups contained in the binder polymer of the electrode active material layer and the hydroxyl groups of the boehmite contained in the inorganic coating layer of the separator is promoted, thereby enabling the formation of more covalent bonds.

[0112] The above drying may be performed by vacuum drying in a vacuum atmosphere at a temperature of 90 to 130°C. By performing drying under the conditions presented above, water, which is a product of the condensation reaction between carboxyl and hydroxyl groups, can be removed, thereby further promoting the condensation reaction and allowing for the formation of more covalent bonds. As a result, the adhesion between the electrode and the separator can be improved, and the capacity retention rate and rate characteristics can be improved, thereby improving the battery life.

[0114] The secondary battery manufactured by the manufacturing method of the present invention described above may have -COO- bonds formed by a condensation reaction at the interface between the separator and the electrode. Specifically, it can be confirmed that -COO- bonds are formed at the interface between the separator and the electrode inside the secondary battery by analysis or measurement methods such as XPS (X-ray photoelectron spectroscopy) or Raman spectroscopy.

[0116] Hereinafter, the present invention will be described in detail with reference to FIG. 2 and embodiments to specifically explain the invention. However, the drawings and embodiments according to the present invention may be modified in various different forms, and the scope of the present invention should not be interpreted as being limited to the drawings and embodiments. The drawings and embodiments of the present invention are provided to more completely explain the invention to those with average knowledge in the art.

[0118] For example, referring to FIG. 2, a method for manufacturing a secondary battery according to an embodiment of the present invention is described as follows: the electrode having an electrode active material layer is unwound from the electrode roll (100) and moves at a constant speed on a conveyor. Before the electrode and the separator are laminated, an aqueous solvent is sprayed onto the surface of the electrode active material layer by a spray 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 facing each other. Subsequently, an electrode assembly is manufactured by laminating through a lamination device (400), specifically a heater chamber (410) and a roller (420), and the electrode assembly can be dried by passing through a drying device (500).

[0120] Specifically, one embodiment according to the present invention is described as follows.

[0121] 1) Cathode manufacturing

[0122] A water-based binder-based cathode was prepared by mixing a cathode active material, a water-based binder, and SBR in a weight ratio of 97.5:1:1.5.

[0123] The cathode active material comprises graphite and Si-based cathode materials (pure-Si, SiO, SiOx, SiC), and the aqueous binder comprises carboxymethylcellulose (CMC) and polyacrylic acid (PAA).

[0124] 2) Anode manufacturing

[0125] A cathode was prepared by mixing a cathode active material, a PVDF binder, and a conductive material in a weight ratio of 97:1.5:1.5. The cathode active material includes LCO and NCM, and the conductive material includes Ketjenblack and Super P.

[0126] 3) Preparation of the separator

[0127] A separation membrane having an inorganic coating layer was prepared by applying and drying a slurry prepared by adding PVDF as a binder polymer and boehmite (particle size: 0.2㎛) as an inorganic particle to NMP (N-Methyl-2-pyrrolidone) as a solvent in a weight ratio of 5:95 to a polyethylene porous substrate (thickness about 9㎛, porosity about 40%~45%).

[0128] 4) Manufacturing of secondary batteries

[0129] The impurity-removed DI water was sprayed onto the surface of the cathode active material layer of the cathode prepared in 1) above, thereby activating the binder polymer exposed on the surface of the cathode active material layer.

[0130] Subsequently, the separator of 3) above was interposed between the manufactured cathode and anode to manufacture an electrode assembly, heated to a temperature of 50°C to 130°C, and 1 kgf / cm² 2 up to 10 kgf / cm² 2 Lamination was performed by applying pressure, and a secondary battery was manufactured by vacuum drying at a temperature of 90 to 130°C.

Claims

Claim 1 (S10) a step of preparing an electrode having an electrode current collector and an electrode active material layer formed on at least one surface of the electrode current collector, and a separator having a porous substrate and an inorganic coating layer formed on at least one surface of the substrate; (S20) a step of spraying a water-based solvent onto the surface of the electrode active material layer; (S30) a step of laminating the surface of the electrode active material layer of (S20) and the inorganic coating layer of the separator to form an electrode assembly including an electrode and a separator; and (S40) a step of drying the electrode assembly of (S30); wherein the electrode active material layer comprises a binder polymer containing carboxyl groups, and the separator comprises boehmite in the inorganic coating layer, and the hydroxyl groups of the boehmite and the carboxyl groups of the binder polymer undergo a condensation reaction to form a covalent bond, thereby forming a method for manufacturing a secondary battery. Claim 2 A method for manufacturing a secondary battery according to claim 1, wherein (S20) is spraying an aqueous solvent at a temperature of 20 to 30°C onto at least a portion of the surface of the electrode active material layer. Claim 3 A method for manufacturing a secondary battery according to claim 1, wherein (S20) is spraying an aqueous solvent in the form of a mist for 1 to 10 seconds onto at least a portion of the surface of the electrode active material layer. Claim 4 In claim 1, the lamination of (S30) is at a temperature of 50℃ to 130℃ and 1 kgf / cm² 2 up to 10 kgf / cm² 2 A method for manufacturing a secondary battery, which is performed under pressure conditions. Claim 5 A method for manufacturing a secondary battery according to claim 1, wherein the drying of (S40) is performed by vacuum drying at a temperature of 90 to 130°C. Claim 6 delete Claim 7 A method for manufacturing a secondary battery according to claim 1, wherein the binder polymer containing the carboxyl group is a water-dispersible or water-soluble binder polymer. Claim 8 A method for manufacturing a secondary battery according to claim 1, wherein the binder polymer containing the carboxyl group comprises carboxymethylcellulose, polyacrylic acid, or all of these. Claim 9 A method for manufacturing a secondary battery according to claim 1, wherein the electrode further comprises an adhesive binder polymer comprising 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, hydroxypropylmethylcellulose, hydroxypropylcellulose and diacetylcellulose, or two or more of these. Claim 10 A method for manufacturing a secondary battery according to claim 1, wherein the electrode is a negative electrode and the negative electrode active material comprises a carbon-based active material and a silicon-based active material. Claim 11 A method for manufacturing a secondary battery according to claim 1, wherein the aqueous solvent comprises 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. Claim 12 A secondary battery manufactured by the manufacturing method of any one of paragraphs 1 to 5 or paragraphs 7 to 11.

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