Positive electrode and secondary battery including same

Abstract

A positive electrode according to the present invention includes: a current collector; a positive electrode mixture layer provided on a part of the current collector and including a positive electrode active material; and an insulating layer adjacent to the positive electrode mixture layer and disposed on the current collector without the positive electrode mixture layer, wherein the insulating layer includes a non-aqueous binder including a solution-polymerized conjugated diene-based copolymer and inorganic particles, and thus cracks can be prevented from occurring in an overlapping region between the insulating layer and the positive electrode mixture layer, and the problem of electrode detachment and the phenomenon of the insulating layer being recessed can be solved.

Description

Anode and secondary battery containing the same

[0001] The present specification relates to a positive electrode and a secondary battery including the same, and more specifically, to a technology for a positive electrode having an insulating layer including a non-aqueous binder including a solution-polymerized conjugated diene copolymer and inorganic particles, and a secondary battery including the same.

[0002]

[0003] With the recent technological development and increasing demand for mobile devices, the demand for batteries as an energy source is rapidly increasing. Consequently, diverse research is being conducted to develop batteries that can meet diverse needs. In particular, active research is being conducted on secondary batteries that possess high energy density and excellent lifespan and cycling characteristics as power sources for these devices.

[0004] A secondary battery includes a positive electrode containing a positive electrode active material capable of insertion / de-insertion of lithium ions, a negative electrode containing a negative electrode active material capable of insertion / de-insertion of lithium ions, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode have a structure in which an electrode active material layer is formed on one surface of an electrode current collector or on the positive electrode, and recently, a technology for forming an insulating layer on the outer surface of the electrode active material layer is being developed to improve the stability of the electrode. By forming an insulating layer on the outer surface of the electrode active material layer, the electrode active material layer can be protected from heat generated during electrode operation, and insulation between electrodes can be improved.

[0005] Conventional electrode insulating layers have typically been formed using binders with insulating properties. However, binders have poor heat resistance. Therefore, conventional binder-based insulating layers exhibit reduced adhesive strength under high-temperature conditions associated with battery operation, thereby compromising battery safety. To address this issue, a technique has been proposed to improve the heat resistance of the insulating layer by adding inorganic particles to an electrode insulating coating composition.

[0006] Even when improving the heat resistance of the insulating layer by adding inorganic particles as described above, a binder must be included, and conventionally, insulating coating was performed using a commonly used non-aqueous binder (e.g., PVDF). However, the insulating layer formed using a non-aqueous binder has a low adhesive strength (hereinafter, wet adhesive strength) when immersed in an electrolyte, and thus has a problem in that the capacity is developed because the movement of lithium ions in the overlay region of the electrode is not blocked.

[0007] Accordingly, research has been conducted on using aqueous binders, such as emulsion polymerized styrene-butadiene rubber (SBR), as a binder for the electrode's insulating layer. To form an insulating layer with an aqueous binder, water is used as a solvent during the process of preparing the coating solution. However, electrodes, especially positive electrodes, have limitations in that the active material components are highly susceptible to moisture. Therefore, using water as a solvent can cause damage to the positive electrode active material layer. Furthermore, if the insulating composition for forming the insulating layer contains an aqueous binder, there is a limitation that gelation occurs upon contact with the non-aqueous binder included in the active material slurry.

[0008]

[0009] The present specification aims to provide an anode in which cracks or depressions do not occur in the overlay portion between the insulating layer and the anode composite layer and the anode composite layer does not detach by using a solution-polymerized conjugated diene copolymer as a binder for the insulating layer.

[0010] In addition, the present specification aims to provide a secondary battery having improved safety by including a positive electrode having an insulating layer as described above, thereby preventing a short circuit between electrodes and preventing the problem of the insulating layer being detached even in an environment impregnated with an electrolyte.

[0011]

[0012] [1] In one aspect, a positive electrode is provided, including: a positive electrode composite layer provided on a portion of the positive electrode composite layer and including a positive electrode active material; and an insulating layer disposed adjacent to the positive electrode composite layer but on a positive electrode composite layer not provided thereon; wherein the insulating layer includes a binder including a solution-polymerized conjugated diene copolymer and inorganic particles.

[0013] [2] In the above [1], the solution polymerized conjugated diene copolymer may include 5 to 95 wt% of a diene monomer unit and 5 to 95 wt% of an aromatic vinyl monomer unit.

[0014] [3] In the above [1] and / or [2], the binder may be surfactant-free.

[0015] [4] In any one or more of the above [1] to [3], the insulating layer may include an overlay portion that covers a portion of the positive electrode composite layer at a portion in contact with the positive electrode composite layer.

[0016] [5] In any one or more of the above [1] to [4], the inorganic particles may include at least one selected from the group consisting of boehmite (AlOOH), aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), alumina (Al2O3), and zirconia (ZrO2).

[0017] [6] In any one or more of the above [1] to [5], the positive electrode active material includes a lithium metal phosphate compound, and the lithium metal phosphate compound may be represented by the following chemical formula 1.

[0018] [Chemical Formula 1]

[0019] Li 1+x [Fe 1-y M y ]PO4

[0020] In the above chemical formula 1, M includes at least one selected from the group consisting of Mn, Co, Ni, Al, Mg, and Ti, and -0.5≤x≤0.5, 0≤y<1.

[0021] [7] In any one or more of the above [1] to [6], the insulating layer may contain 40 to 95 parts by weight of the inorganic particles and 5 to 60 parts by weight of the binder, based on 100 parts by weight of the insulating layer.

[0022] [8] In any one or more of the above [1] to [7], the binder may further include an auxiliary binder, and the auxiliary binder may include polyvinylidene fluoride.

[0023] [9] In any one or more of the above [1] to [8], the weight ratio of the solution-polymerized conjugated diene copolymer and the auxiliary binder may be 95:5 to 70:30.

[0024]

[0010] In any one or more of the above [1] to [9], the positive electrode composite layer may further include a binder and a conductive material.

[0025]

[0026]

[0011] In one aspect, a method for manufacturing a positive electrode is provided, comprising: a step (S1a) of applying a positive electrode slurry containing a positive electrode active material to a portion of a current collector; a step (S1b) of applying an insulating coating composition on a current collector adjacent to a region where the positive electrode slurry is applied but not applied; and a step (S2) of drying the positive electrode slurry and the insulating coating composition applied on the current collector to form a positive electrode composite layer and an insulating layer; wherein the insulating coating composition includes a non-aqueous binder including a solution-polymerized conjugated diene copolymer, a non-aqueous organic solvent, and inorganic particles.

[0027]

[0012] In the above

[0011] , the S1a step and the S1b step may be performed before the S2 step, but may be performed simultaneously or sequentially.

[0028]

[0013] In the above

[0011] and / or

[0012] , the positive electrode slurry may have a solid content of 50 wt% to 70 wt%, and the insulating coating composition may have a solid content of 10 wt% to 40 wt%.

[0029]

[0030]

[0014] In one aspect, a secondary battery including the aforementioned positive electrode is provided.

[0031]

[0032] The anode described in this specification can prevent cracking and sinking in the overlapping area of ​​the insulating layer and the anode composite layer.

[0033] The method for manufacturing an anode described in this specification can prevent interaction between the anode slurry and the insulating coating composition when coating on a current collector by including a solution-polymerized conjugated diene copolymer in the insulating coating composition, and thus can prevent the anode composite layer from being detached or lifted off from the anode after drying in which the insulating layer is formed.

[0034] The secondary battery described herein has an insulating layer with excellent wet adhesion, which maintains adhesion to the current collector and positive electrode composite layer even after being impregnated with an electrolyte, thereby preventing detachment. This significantly reduces the possibility of short circuits between electrodes, thereby improving the safety of the secondary battery.

[0035]

[0036] Figure 1 is a photograph showing a portion where the positive electrode composite layer and the insulating layer of the electrode of Example 1 are adjacent.

[0037] Figure 2 is a photograph showing a cross-section of a portion where the positive electrode composite layer and the insulating layer of the electrode of Example 1 are adjacent.

[0038] Figure 3 is a photograph showing a portion where the positive electrode composite layer and the insulating layer of the electrode of Comparative Example 1 are adjacent.

[0039] Figure 4 is a photograph showing a cross-section of a portion where the positive electrode composite layer and the insulating layer of the electrode of Example 1 are adjacent.

[0040]

[0041] The advantages and features of the invention described herein, and the methods for achieving them, will become clearer with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0042] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0043] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0044] In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise.

[0045] In this specification, the description of “A and / or B” means A, or B, or A and B.

[0046] In this specification, “%” means weight percent unless explicitly indicated otherwise.

[0047] In this specification, D 50 In the particle size distribution curve of silver particles, it means the particle size corresponding to 50% of the volume accumulation, and D 90 In the particle size distribution curve of silver particles, it means the particle size corresponding to 90% of the accumulated number. The above D 50 and D 90 For example, it can be measured using the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several mm, and can obtain results with high reproducibility and high resolution.

[0048] In this specification, each of the positive electrode, the method for manufacturing the positive electrode, and the secondary battery including the same includes at least one of the technical features and / or technical configurations described below, and these technical features and / or technical configurations can be combined in various ways.

[0049]

[0050] Below, the positive electrode, the manufacturing method of the positive electrode, and the secondary battery are described in detail.

[0051]

[0052] anode

[0053] In one aspect, the positive electrode comprises: a current collector; a positive electrode composite layer provided on a portion of the current collector and including a positive electrode active material; and an insulating layer disposed adjacent to the positive electrode composite layer but on a current collector not provided with the positive electrode composite layer; wherein the positive electrode active material comprises a lithium metal phosphate-based compound, and the insulating layer comprises a non-aqueous binder including a solution-polymerized conjugated diene-based copolymer and inorganic particles.

[0054] The above positive electrode is characterized in that it includes a lithium metal phosphate-based compound in the positive electrode composite layer and a solution-polymerized conjugated diene-based copolymer as a non-aqueous binder in the insulating layer.

[0055] Previously, when using a non-aqueous binder, the problem of poor wet adhesiveness in an electrolyte-impregnated state led to the use of aqueous binders, and emulsion polymerization SBR has been used as a representative example. The emulsion polymerization SBR is classified as aqueous because polymerization is performed in the presence of an emulsifier and a surfactant using water as a solvent. However, when an aqueous binder is used in the insulating layer coated on the terminal of the positive electrode, the positive electrode active material is very vulnerable to moisture, which can affect battery performance in various ways, and can cause the problem of gelation when in contact with the oil-based binder of the positive electrode slurry.

[0056] Accordingly, a special process is required to use emulsion polymerized SBR as a binder in an insulating layer. The above problem can be solved by replacing the aqueous solvent of emulsion polymerized SBR with a non-aqueous organic solvent, so that its properties are identical to those of the solvent component of the cathode slurry.

[0057] However, replacing the aqueous solvent of the above-mentioned emulsion polymerization SBR with a non-aqueous solvent is a pretreatment that requires a separate process, and there is a problem that the process efficiency is too low when performing the above-mentioned pretreatment for application to the insulating layer, which is indispensable for the battery but occupies a relatively low proportion in the battery, and this can be a major cause of loss of unit price competitiveness.

[0058] The insulating layer applied to the above anode aims to solve the above problem by applying a solution-polymerized conjugated diene copolymer as a binder.

[0059] The insulating layer may include an overlay portion that covers a portion of the anode composite layer at a portion in contact with the anode composite layer.

[0060] As mentioned above, the overlay portion is a portion that comes into contact with the anode composite layer, and is a portion where problems often occur when using an oil-based binder or an aqueous binder, and problems such as easy detachment or cracking frequently occur.

[0061] In the case of the above emulsion polymerization SBR, if the positive electrode active material of the positive electrode composite layer is a lithium nickel-based oxide, it can be used without any problem, but if a lithium metal phosphate-based compound is used as the positive electrode active material, a phenomenon such as the collapse of the difference in surface tension between the positive electrode slurry and the insulating composition occurs due to a surfactant that is inevitably included in the emulsion polymerization SBR due to the characteristics of the polymerization reaction, and this may lead to problems such as the destruction of the insulating layer in the overlay portion due to the lifting or detachment of the composite layer after drying, or the occurrence of a sinking or cracking of a portion of the insulating layer.

[0062] In one aspect, the positive electrode includes a positive electrode active material including a lithium metal phosphate compound in the positive electrode composite layer, and an insulating layer for insulating the positive electrode composite layer includes a solution-polymerized conjugated diene copolymer, thereby solving the problem occurring in the overlay portion as described above, and has excellent wet adhesiveness due to the absence of a surfactant, thereby preventing the problem of delamination even in an electrolyte-impregnated state.

[0063] The above insulating layer may be formed with a certain thickness on the current collector and the positive electrode composite layer. In this case, the thickness of the insulating layer may be 10 μm to 30 μm, preferably 15 μm to 25 μm, and more preferably 17 μm to 23 μm. When the thickness of the insulating layer satisfies the above range, the adhesion of the insulating layer to the current collector and / or the positive electrode composite layer may be further improved.

[0064]

[0065] Below, each component of the above anode is described.

[0066]

[0067] (1) A binder comprising a solution-polymerized conjugated diene copolymer.

[0068] In one aspect, the insulating layer is characterized in that it includes a solution-polymerized conjugated diene copolymer as a binder.

[0069] The above solution-polymerized conjugated diene copolymer can be produced through anionic living polymerization in the presence of an initiator and an organic solvent using a diene monomer such as butadiene and an aromatic vinyl monomer such as styrene, wherein the diene monomer and the aromatic vinyl monomer may each be included in an amount of 5 wt% to 95 wt%. Specific polymerization conditions or polymerization additives for the anionic living polymerization are not particularly limited, as long as they do not conflict with common technical knowledge known in the art.

[0070] The above solution-polymerized conjugated diene copolymer may have the characteristics of being surfactant-free with almost no surfactant. Here, "surfactant-free" means that it is not detected at a detectable level, for example, it may mean a level of 100 ppm or less, 50 ppm or less, or 30 ppm or less based on the total weight of the insulating layer. By having the characteristics of being surfactant-free, unlike emulsion polymerized SBR, even when a lithium metal phosphate-based compound is applied as a positive electrode active material, problems that may occur in the overlay portion, such as detachment of the composite layer and cracking of the insulating layer, can be prevented, and the adhesive strength in an electrolyte-impregnated state can also be excellent.

[0071] The above binder may further include polyvinylidene fluoride (PVDF) in addition to the solution-polymerized conjugated diene copolymer. If polyvinylidene fluoride is further included, stronger adhesive strength can be provided.

[0072] The above insulating layer may contain the binder in an amount of 5 to 60 parts by weight, based on 100 parts by weight of the insulating layer, and preferably, 10 parts by weight or more, 15 parts by weight or more, 20 parts by weight or more, or 25 parts by weight or more, and further, 55 parts by weight or less, 50 parts by weight or less, 45 parts by weight or less, or 40 parts by weight or less. When the binder is contained in the insulating layer in this range, the effect of preventing problems occurring in the overlay portion can be further synergized.

[0073] The above binder may further include an auxiliary binder, and representative examples thereof include polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene (PVdF-CTFE), polymethyl methacrylate, polyvinylacetate, ethylene-co-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, styrene butadiene copolymer (Styrene Butadiene Rubber, SBR), acrylonitrile styrene butadiene Aqueous or non-aqueous polymers comprising a single polymer or a mixture of two or more polymers selected from the group consisting of copolymers and polyimides may be used. Among these, polyvinylidene fluoride (PVdF) is particularly preferred.

[0074] In this case, the solution-polymerized conjugated diene copolymer and the auxiliary binder may have a weight ratio of 95:5 to 70:30, and preferably 90:10 to 75:25. When the above range is satisfied, the aforementioned effects can be further optimized.

[0075]

[0076] (2) Inorganic particles

[0077] In one aspect, the insulating layer is characterized by including a solution-polymerized conjugated diene copolymer as a binder and including inorganic particles.

[0078] The purpose of the insulating layer is to prevent potentially hazardous events, such as thermal runaway or explosion, caused by short circuits between electrodes during battery malfunction. Therefore, it is essential that the insulating layer be able to withstand high temperatures without melting. To address this issue, the insulation layer, which previously used only binders, has been incorporating heat-resistant inorganic particles into the insulation layer.

[0079] Accordingly, the insulating layer provided on the anode also includes inorganic particles, and can most significantly perform a function of increasing heat resistance. Since the inorganic particles do not soften or melt even at high temperatures, for example, at temperatures higher than 900°C, when such inorganic particles are included in the insulating layer, electrode insulation can be maintained even at very high temperatures.

[0080] The above inorganic particles may include, for example, at least one selected from the group consisting of boehmite (AlOOH), aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), alumina (Al2O3), and zirconia (ZrO2). Preferably, boehmite may be applied, and in this case, there is an advantage in that better heat resistance can be secured while having excellent dispersibility, so that heat resistance characteristics can be uniformly obtained throughout the entire insulating layer, and the ability to maintain adhesiveness even after electrolyte impregnation can be excellent due to the presence of hydroxyl groups included in the above inorganic particles.

[0081] D of the above inorganic particles 50 The D of the inorganic particles may be 0.1 μm to 5.0 μm, preferably 0.1 μm to 3.0 μm, more preferably 0.3 μm or more, 0.5 μm or more, and also 2.0 μm or less, 1.5 μm or less. 50When the above range is satisfied, the agglomeration of the inorganic particles within the insulating coating composition is minimized when forming the insulating layer, thereby forming an insulating layer having a uniform thickness and surface.

[0082] The above insulating layer may contain the inorganic particles in an amount of 40 to 95 parts by weight, based on 100 parts by weight of the insulating layer, and preferably 45 parts by weight or more, 50 parts by weight or more, or 55 parts by weight or more, and further 90 parts by weight or less, 85 parts by weight or less, 80 parts by weight or less, 75 parts by weight or less, or 70 parts by weight or less. When the content of the inorganic particles satisfies the above range, the occurrence of agglomeration of the inorganic particles in the insulating coating composition when forming the insulating layer is minimized, so that the viscosity of the composition can be appropriately maintained, and an insulating layer having a uniform thickness and surface can be formed.

[0083]

[0084] (3) Bipolar composite layer

[0085] In one aspect, the positive electrode is characterized in that a positive electrode composite layer is provided on a current collector. In addition, the positive electrode composite layer includes a lithium metal phosphate compound as a positive electrode active material, and may further include a conductive material and a binder.

[0086]

[0087] The current collector may be any conductive material that does not induce chemical changes in the battery, and is not particularly limited. For example, the current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like.

[0088] The thickness of the above-mentioned collector may be 3 ㎛ to 100 ㎛, preferably 8 ㎛ to 80 ㎛, but is not limited thereto. In addition, fine unevenness may be formed on the surface of the collector to increase the adhesive strength of the composite film.

[0089]

[0090] The above positive electrode active material includes a lithium metal phosphate compound and may be represented by the following chemical formula 1.

[0091] [Chemical Formula 1]

[0092] Li 1+x [Fe 1-y M y ]PO4

[0093] In the above chemical formula 1, M includes at least one selected from the group consisting of Mn, Co, Ni, Al, Mg, and Ti, and -0.5≤x≤0.5, 0≤y<1.

[0094] The above lithium metal phosphate compound may be doped with M. In this case, the lattice structure and distance within the olivine crystal structure, which is a crystal structure, are changed, thereby increasing the diffusion of lithium ions, and consequently, the electrochemical characteristics of a battery including a positive electrode active material may be improved.

[0095] The above x may be -0.5 to 0.5, preferably -0.3 or more, -0.1 or more, or 0 or more, and may be 0.5 or less, 0.4 or less, 0.3 or less, 0.2 or less, or 0.1 or less.

[0096] The above y may be greater than or equal to 0, less than or equal to 1, and less than or equal to 0.90, less than or equal to 0.80, less than or equal to 0.70, less than or equal to 0.60, less than or equal to 0.50, less than or equal to 0.40, less than or equal to 0.30, less than or equal to 0.20, less than or equal to 0.10, or less than or equal to 0.05.

[0097] The above lithium metal phosphate compound may be, for example, LiFePO4.

[0098] The lithium metal phosphate compound according to the present invention may be in the form of a single particle composed of only one primary particle, or in the form of an irregular secondary particle composed of 2 to 50 primary particles. In addition, the lithium metal phosphate compound may include an olivine structure, and specifically, may be composed only of an olivine structure. The coating layer according to the present invention may be formed not only on the secondary particle but also on the primary particle. That is, the coating layer according to the present invention may be uniformly present on the surface of the primary particle present inside the secondary particle.

[0099] The above coating layer may include a carbon coating layer having a graphite structure, and the coating layer may have a thickness of 0.5 nm to 5 nm. When the thickness of the coating layer is within the above range, there is an advantage in that electrical conductivity is improved and the entry and exit of lithium ions are not hindered. Specifically, the thickness of the coating layer may be 0.5 nm or more, 1.0 nm or more, 1.5 nm or more, 2.0 nm or more, 2.5 nm or more, or 3.0 nm or more, and may be 5.0 nm or less.

[0100] The coating layer may be uniformly coated on the surface of the lithium metal phosphate compound. That is, the coating layer may be in the form of a thin film. The coating layer may improve ionic conductivity and electronic conductivity during charging and discharging of a battery including a positive electrode active material. In addition to carbon, the coating layer may contain trace amounts of impurities such as nitrogen, oxygen, and hydrogen.

[0101] The above coating layer may be included in an amount of 0.5 wt% to 3 wt% based on the total weight of the lithium metal phosphate compound so as to improve electrical conductivity while preventing the entry and exit of lithium ions.

[0102] The above-mentioned positive electrode active material may comprise 80 wt% to 99 wt% based on the total weight of the positive electrode composite layer, preferably 85 wt% or more, 88 wt% or more, 90 wt% or more, 92 wt% or more, 93 wt% or more, or 95 wt% or more, and may also be comprised at 98.5 wt% or less, 98 wt% or less, or 97.5 wt% or less. When comprised within the above range, it may be preferable in terms of both increasing the capacity and energy density of the electrode and optimizing the functions of the conductive material and binder, which are auxiliary materials.

[0103] The conductive agent is a component for further improving the conductivity of the positive electrode active material. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used. Specifically, the conductive agent may include at least one selected from the group consisting of activated carbon, graphite, carbon black, and carbon nanotubes (CNTs) for uniform mixing of the conductive agent and improvement of conductivity.

[0104] The conductive agent may be included in an amount of 0.1 wt% to 10.0 wt% based on the total weight of the positive electrode composite layer. Preferably, it may be included in an amount of 0.2 wt% or more, 0.3 wt% or more, 0.5 wt% or more, or 0.7 wt% or more, and may also be included in an amount of 8.0 wt% or less, 6.0 wt% or less, or 5.0 wt% or less. The more the conductive agent is added, the more advantageous it is for conductive path formation. However, the capacity may be reduced due to a relative decrease in the amount of active material, and it is not easy to control the amount added due to dispersion issues. However, by optimizing the dispersibility within the above range, the effect of conductive path formation can be maximized, so it may be desirable to apply the conductive agent within the above range.

[0105] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0106] The binder may be included in an amount of 0.1 wt% to 10.0 wt% based on the total weight of the positive electrode composite layer. Preferably, it may be included in an amount of 0.2 wt% or more, 0.3 wt% or more, 0.5 wt% or more, or 0.7 wt% or more, and may also be included in an amount of 8.0 wt% or less, 6.0 wt% or less, or 5.0 wt% or less.

[0107]

[0108] Method for manufacturing anode

[0109] In one aspect, the method for manufacturing the positive electrode comprises the steps of: (S1a) applying a positive electrode slurry containing a positive electrode active material to a portion of a current collector; (S1b) applying an insulating coating composition on a current collector adjacent to a region where the positive electrode slurry is applied but not on a region where the positive electrode slurry is applied; and (S2) drying the positive electrode slurry and the insulating coating composition applied on the current collector to form a positive electrode composite layer and an insulating layer; wherein the positive electrode active material comprises a lithium metal phosphate-based compound, and the insulating coating composition comprises a binder including a solution-polymerized conjugated diene-based copolymer, an organic solvent, and inorganic particles.

[0110] The above S1a step can be manufactured according to a conventional positive electrode manufacturing method. Specifically, it can be manufactured by dissolving or dispersing a positive electrode active material, a binder, and a conductive agent in a solvent, applying a positive electrode slurry onto a positive electrode current collector, and then drying and rolling.

[0111] The above S1b step can also be manufactured according to a conventional insulating layer manufacturing method. For example, the insulating coating composition can be manufactured by mixing inorganic particles and a binder in an organic solvent and performing a dispersion process. Specifically, each component of the composition is mixed by adding the particles to the organic solvent and mixing them. At this time, the mixing can be performed using mixing devices well known in the art, such as a homo mixer, but is not limited thereto.

[0112] The composition that has undergone the above mixing process is dispersed by milling. The milling can be performed using a ball mill, a bead mill, or a basket mill, and more specifically, can be performed using a bead mill. Meanwhile, the degree of dispersion of the composition can be controlled by controlling milling conditions, such as the number of times the composition is passed through the ball mill, bead mill, or basket mill (hereinafter, "number of passes"), the rotor speed, etc.

[0113]

[0114] The above steps S1a and S1b may be performed simultaneously, or sequentially before the drying process of step S2 is performed. Specifically, a coater having multiple nozzles may be used to simultaneously apply the positive electrode slurry and the insulating coating composition onto the current collector, and the process may be designed so that the positive electrode slurry coating equipment and the insulating coating composition coating equipment are sequentially arranged in the direction of movement of the conveyor so that both coatings can be performed before drying.

[0115] The above S2 step is a drying process, and conditions generally applied in this technical field can be applied, and for example, drying can be performed at a temperature of 120°C to 170°C, preferably 130°C to 160°C. The above temperature range is a harsher condition than a general drying process. When a lithium metal phosphate compound is used as a positive electrode active material, the solid content contained in the slurry with the same viscosity level as that of a slurry using another positive electrode active material is lower, and thus the content of solvent that must be removed is greater, so the drying process needs to be performed under somewhat harsher conditions. At this time, after the drying process, there may be problems such as detachment of the positive electrode composite layer or the insulating layer, cracks, or depressions, and these problems can occur particularly easily in the overlay portion. However, when an insulating layer according to an embodiment of the present invention is applied, such problems can be solved.

[0116] Meanwhile, according to one embodiment of the present invention, the positive electrode slurry may have a solid content of 50 wt% to 70 wt%, preferably 55 wt% to 65 wt%, and the insulating coating composition may have a solid content of 10 wt% to 40 wt%, preferably 10 wt% to 35 wt%. When the solid content is controlled within the above range, mixing of the positive electrode slurry and the insulating coating composition may not occur, and the problem of the insulating coating composition penetrating into the interface between the positive electrode composite layer and the current collector may not occur.

[0117]

[0118] (1) Organic solvent

[0119] In one aspect, the insulating coating composition may be a mixture of inorganic particles and a binder under an organic solvent, and the positive electrode slurry may also be a mixture of a positive electrode active material, a conductive material, and a binder under an organic solvent. The organic solvents of the insulating coating composition and the positive electrode slurry may be the same or different from each other, and there is no particular limitation on their application as long as they are applied as non-aqueous organic solvents.

[0120] The organic solvent may be a solvent generally used in the relevant technical field, and examples thereof include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethyl formamide (DMF), acetone, and water. One of these may be used alone or a mixture of two or more may be used. The amount of the organic solvent used is sufficient to dissolve or disperse the component particles, taking into account the coating thickness and manufacturing yield of the positive electrode slurry and the insulating coating composition, and to have a viscosity that can subsequently exhibit excellent thickness uniformity.

[0121]

[0122] (2) Dispersant

[0123] In one aspect, the insulating coating composition may further comprise a dispersant. The dispersant is intended to improve the dispersibility of insoluble particles within each of the compositions.

[0124] Examples of such dispersants include cellulose compounds, and non-limiting examples thereof include carboxyl methyl cellulose, carboxyl ethyl cellulose or derivatives thereof, such as cation-substituted compounds such as ammonium ions and monovalent metal ions.

[0125]

[0126] secondary battery

[0127] In one aspect, the secondary battery includes a positive electrode, a negative electrode positioned opposite the positive electrode, and a separator interposed between the positive electrode and the negative electrode, and an electrolyte may be injected and contained after being accommodated in a battery case. Here, since the positive electrode is the same as described above, a detailed description thereof will be omitted, and only the remaining components will be described in detail below.

[0128] The secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container.

[0129]

[0130] In the above secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode composite layer positioned on the negative electrode current collector.

[0131] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the negative electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0132]

[0133] The above negative electrode composite layer optionally includes a binder and a conductive material together with a negative electrode active material.

[0134] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0 < β < 2), metal oxides capable of doping and dedoping lithium, such as SnO2, vanadium oxide, and lithium vanadium oxide; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fibers, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature heat-treated carbon such as petroleum or coal tar pitch derived cokes.

[0135] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0136]

[0137] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0138] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode composite layer. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0139]

[0140] The above negative electrode composite layer can be manufactured by applying and drying a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the negative electrode slurry composition on a separate support, and then laminating the obtained film by peeling it off from the support on a negative electrode current collector.

[0141]

[0142] In the above secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without any particular restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0143]

[0144] Examples of the electrolyte used in the secondary battery include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of secondary batteries.

[0145] The electrolyte may include an organic solvent and a lithium salt.

[0146] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0147]

[0148] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in secondary batteries. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the concentration of the lithium salt within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0149]

[0150] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0151]

[0152] In another aspect, the secondary battery may be an all-solid-state battery, in which case a solid electrolyte layer may be interposed between the positive and negative electrodes instead of a separator. The solid electrolyte may be one commonly used in this technical field, and there are no particular limitations thereon.

[0153]

[0154] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention solely to these examples.

[0155]

[0156] Preparation of insulating coating composition

[0157] Manufacturing Example 1

[0158] D 50 This 1.0 μm, specific surface area is about 5.0 m 2 / g to 8.5 m 260 parts by weight of boehmite (product name: BP10, manufacturer: KEATON), 35 parts by weight of solution-polymerized SBR (a linear copolymer solution-polymerized with 40 parts by weight of styrene and 60 parts by weight of butadiene, weight average molecular weight 250,000) as a binder, and 5 parts by weight of PVDF (product name: KF9700, manufacturer: KUREHA) were mixed in a non-aqueous organic solvent NMP to prepare a 1 kg mixture, and mixing was performed for 1 hour using a Homo mixer (product name: Dispermat LC, manufacturer: VMA).

[0159] Next, an insulating coating composition was manufactured by performing a dispersion process using a bead mill (product name: LS-1, manufacturer: Netsch) at a rotor speed of 3300 RPM, a 1-pass discharge amount of 540 g / min, and a pass number of 8.

[0160]

[0161] Manufacturing Example 2

[0162] An insulating coating composition was manufactured in the same manner as in Manufacturing Example 1, except that 65 parts by weight of boehmite was added and PVDF was not added among the binders.

[0163]

[0164] Manufacturing Example 3

[0165] An insulating coating composition was manufactured in the same manner as in Manufacturing Example 1, except that 65 parts by weight of boehmite was added and 30 parts by weight of solution-polymerized SBR among the binders was added.

[0166]

[0167] Manufacturing Example 4

[0168] An insulating coating composition was manufactured in the same manner as in Manufacturing Example 1, except that 70 parts by weight of boehmite was added, 30 parts by weight of solution-polymerized SBR as a binder was added, and PVDF was not added.

[0169]

[0170] Comparative Manufacturing Example 1

[0171] To 100 parts by weight of a dispersion of emulsion polymerized SBR (hereinafter, ZEON BM451B product) in water at a weight ratio of 60:40, 500 parts by weight of N-methyl-2-pyrrolidone (NMP) solvent was added and stirred. Then, the stirred mixture was heated at 100 to 120°C for 2 hours to completely evaporate the contained water, thereby preparing an NMP-substituted emulsion polymerized SBR binder. Then, an insulating coating composition was prepared in the same manner as in Preparation Example 1 using the NMP-substituted SBR binder instead of the solution polymerized SBR.

[0172]

[0173] Comparative Manufacturing Example 2

[0174] An insulating coating composition was prepared in the same manner as in Manufacturing Example 2, except that 35 parts by weight of PVDF was added instead of solution-polymerized SBR in the binder.

[0175]

[0176]

[0177] The weight average molecular weight of the binder polymer used above is the value measured using gel permeation chromatography (GPC) under the following conditions and converted to standard polystyrene, and the standard polystyrene of the Agilent system was used to prepare the calibration curve.

[0178] <Measurement conditions>

[0179] Measuring instrument: Agilent GPC (Agilent 1200 series)

[0180] Column: PL Mixed B 2 connections

[0181] Column temperature: 40℃

[0182] Eluent: Tetrohydrofuran

[0183] Flow rate: 1.0 mL / min

[0184] Concentration: ~ 1 mg / mL (100 μL injection)

[0185]

[0186] Manufacturing of anodes

[0187] Examples 1 to 4

[0188] As a cathode active material, LiFePO496 parts by weight, as a binder, 2 parts by weight, as a conductive material, carbon black 2 parts by weight, were weighed and mixed in an N-methylpyrrolidone (NMP) solvent to prepare a cathode slurry. Then, the cathode slurry and the insulating coating compositions prepared in Preparation Examples 1 to 4 were simultaneously applied to a current collector using a double slot die coater, and the cathode composite layer had a loading of 20 mg / cm. 2 , and the insulating layer was made to have an average thickness of 20 ㎛. Then, each electrode sample was dried at an average temperature of 130℃ to manufacture a cathode.

[0189]

[0190] Comparative Example 1

[0191] An anode was manufactured in the same manner as in Example 1, except that the insulating coating composition manufactured in Comparative Manufacturing Example 1 was used.

[0192]

[0193] Comparative Example 2

[0194] An anode was manufactured in the same manner as in Example 1, except that the insulating coating composition manufactured in Comparative Manufacturing Example 2 was used.

[0195]

[0196]

[0197] Positive electrode active material Boehmite (weight part) Binder type Content Example 1 LFP60SSBR+PVDF35+5 Example 2 LFP65SSBR35 Example 3 LFP65SSBR+PVDF30+5 Example 4 LFP70SSBR30 Comparative example 1 LFP60ESBR (solvent replacement)+PVDF35+5 Comparative example 2 LFP65PVDF35

[0198] Experimental Example 1: Appearance Evaluation

[0199] For the positive electrodes of Examples 1 to 4 and Comparative Examples 1 and 2, the surface of the insulating layer was photographed to check whether cracks or depressions occurred, and the occurrence of detachment / lifting of the positive electrode composite layer was checked through cross-sectional photographs of the positive electrodes. After the positive electrodes were impregnated with an electrolyte (EC:DMC=55:45 organic solvent, LiPF61M), they were stored in an oven at 60°C for one week, and then whether the insulating layer detached was checked. The surface and cross-sectional photographs of the insulating layers of the positive electrodes of Example 1 and Comparative Example 1 are attached as FIGS. 1 to 4.

[0200] Overlay cracks, depressions, presence or absence of composite layer lifting, presence or absence of electrolyte wetting and detachment, Example 1XXXX, Example 2XXXX, Example 3XXXX, Example 4XXXX, Comparative Example 1OOOX, Comparative Example 2XXXO

[0201] First, looking at Figures 1 and 2, they are photographs of the surface of the insulating layer of Example 1 and Comparative Example 1, respectively, and W is indicated in the drawings. I is the insulation width and W O means the width of the overlay portion. Unlike Fig. 1, in Fig. 2, it can be confirmed that part B is sunken, and cracks have occurred like part A. In addition, looking at Figs. 3 and 4, in the photo of Fig. 3, which is a cross-section of Example 1, it can be confirmed that the positive electrode composite layer and the insulating layer are well adhered to the current collector, but in the positive electrode cross-section of Comparative Example 1 in Fig. 4, it can be confirmed that the positive electrode composite layer is detached from the current collector and a part is lifted.

[0202] In addition, referring to Table 1 above, it was confirmed that in the case of Examples 2 to 4, no lifting, detachment, or cracking occurred on the surface or cross-section, similar to Example 1. In addition, in the case of Comparative Example 2, it was confirmed that the PVDF binder used had a property of being easily wetted by the electrolyte, and thus, a problem of detachment occurring after wetting with the electrolyte occurred.

Claims

1. A current collector; a positive electrode composite layer provided on a portion of the current collector and including a positive electrode active material; and an insulating layer disposed adjacent to the positive electrode composite layer but on a current collector not provided with the positive electrode composite layer; The above insulating layer is an anode comprising a binder including a solution-polymerized conjugated diene copolymer and inorganic particles.

2. In paragraph 1, The above solution polymerized conjugated diene copolymer comprises 5 to 95 wt% of a diene monomer unit and 5 to 95 wt% of an aromatic vinyl monomer unit.

3. In paragraph 1, The above binder is surfactant-free and positive.

4. In paragraph 1, The above insulating layer is an anode, which includes an overlay portion covering a portion of the anode composite layer at a portion in contact with the anode composite layer.

5. In paragraph 1, The anode comprises at least one selected from the group consisting of boehmite (AlOOH), aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), alumina (Al2O3), and zirconia (ZrO2).

6. In paragraph 1, The above positive electrode active material includes a lithium metal phosphate compound, The above lithium metal phosphate compound is represented by the following chemical formula 1, the positive electrode: [Chemical Formula 1] Li 1+x [Fe 1-y M y ]PO4 In the above chemical formula 1, M includes at least one selected from the group consisting of Mn, Co, Ni, Al, Mg, and Ti, and -0.5≤x≤0.5, 0≤y<1.

7. In paragraph 1, The above insulating layer is, for 100 parts by weight of the insulating layer, A positive electrode comprising 40 to 90 parts by weight of the inorganic particles and 10 to 60 parts by weight of the binder.

8. In paragraph 1, An anode, wherein the binder further comprises an auxiliary binder, and the auxiliary binder comprises polyvinylidene fluoride.

9. In paragraph 8, The above solution polymerized conjugated diene copolymer and auxiliary binder have a weight ratio of 95:5 to 70:30, the positive electrode.

10. In paragraph 1, An anode, wherein the above anode composite layer further comprises a binder and a conductive material.

11. Step of applying a cathode slurry containing a cathode active material to a part of the current collector (S1a); A step (S1b) of applying an insulating coating composition on a current collector adjacent to an area where the positive electrode slurry is applied, but in an area where the positive electrode slurry is not applied; and A step (S2) of drying the positive electrode slurry and insulating coating composition applied on the above-mentioned collector to form a positive electrode composite layer and an insulating layer; A method for manufacturing an anode, wherein the insulating coating composition comprises a binder including a solution-polymerized conjugated diene copolymer, an organic solvent, and inorganic particles.

12. In paragraph 11, A method for manufacturing a positive electrode, wherein the above steps S1a and S1b are performed before the S2 step, but are performed simultaneously or sequentially.

13. In paragraph 11, The above positive electrode slurry has a solid content of 50 wt% to 70 wt%, A method for manufacturing an anode, wherein the insulating coating composition has a solid content of 10 wt% to 40 wt%.

14. A secondary battery comprising the positive electrode described in paragraph 1.

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