Method for manufacturing a positive electrode current collector coated with an adhesion promoting layer, and a positive electrode current collector coated with an adhesion promoting layer manufactured thereby, a method for manufacturing a positive electrode for a lithium secondary battery, and a positive electrode for a lithium secondary battery manufactured thereby, and a lithium secondary battery including the positive electrode for a lithium secondary battery

Abstract

The present invention discloses a method for producing a positive electrode current collector coated with an adhesion promotion layer, the method including the steps of: preparing an aqueous slurry containing a first binder polymer, including polyvinylidene fluoride-based polymer particles having a melting point of 50 to 150°C, and a first conductive material, in a weight ratio of 0.5:1 to 8:1; and coating at least one surface of a metal current collector with the aqueous slurry, and heat-treating and drying the coating at a temperature higher than the melting point of the polyvinylidene fluoride-based polymer particles to form an adhesion promotion layer.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer, a positive electrode current collector coated with an adhesion-promoting layer manufactured thereby, a method for manufacturing a positive electrode for a lithium secondary battery, a positive electrode for a lithium secondary battery manufactured thereby, and a lithium secondary battery including the positive electrode for a lithium secondary battery.

[0002] This application claims priority based on Korean Patent Application No. 10-2021-0150118 filed on November 3, 2021, and Korean Patent Application No. 10-2021-0150119 filed on November 3, 2021, and the contents disclosed in the specifications and drawings of those applications are incorporated into this application in their entirety. [Background technology]

[0003] Recently, with the rapid spread of battery-powered electronic devices such as mobile phones, notebook PCs, and electric vehicles, the demand for small, lightweight, and relatively high-capacity secondary batteries is rapidly increasing. In particular, lithium secondary batteries are attracting attention as a power source for portable devices due to their light weight and high energy density. As a result, research and development efforts to improve the performance of lithium secondary batteries are actively underway.

[0004] In a lithium secondary battery, an organic or polymer electrolyte is filled between a positive electrode and a negative electrode, which are made of active materials that allow the intercalation and deintercalation of lithium ions. Electrical energy is generated through oxidation and reduction reactions that occur when lithium ions are inserted into and extracted from the positive and negative electrodes.

[0005] A positive electrode of a lithium secondary battery is typically fabricated by coating a positive electrode active material slurry containing a positive electrode active material, a conductive material, a binder polymer, and a solvent onto a positive electrode current collector made of a metal such as aluminum, followed by drying to form a positive electrode active material layer. Specifically, the positive electrode is fabricated by weighing and mixing the components of the positive electrode active material slurry, coating the slurry on the positive electrode current collector, drying, and then pressing.

[0006] The fabricated cathode is then assembled into a lithium secondary battery through a post-process, but the adhesive strength between the cathode active material layer and the current collector is weak, which can lead to the cathode active material detaching. This problem becomes more severe when a lithium iron phosphate-based cathode active material is used or when the size of the active material is small.

[0007] To solve these problems, a method has been proposed in which an adhesion-promoting layer containing a binder polymer is formed on the current collector before the positive electrode active material layer is formed on the current collector. However, there is a need to develop an adhesion-promoting layer that can more firmly bond the positive electrode active material layer to the current collector and has low interfacial resistance.

[0008] There is also a need to reduce the energy used to dry the coated adhesion-promoting layer-forming slurry and to manufacture a lithium secondary battery that can maintain adhesion to the electrode when applied to a lithium secondary battery containing an electrolyte solution. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer that improves the adhesion between a positive electrode active material layer and a current collector and has low interfacial resistance, a positive electrode current collector coated with the adhesion-promoting layer manufactured thereby, a method for manufacturing a positive electrode for a lithium secondary battery, a positive electrode for a lithium secondary battery manufactured thereby, and a lithium secondary battery including the positive electrode for a lithium secondary battery.

[0010] Another object of the present invention is to provide a method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer that reduces the energy used in drying an aqueous slurry for forming a coated adhesion-promoting layer and maintains adhesion to the electrode when applied to a lithium secondary battery containing an electrolyte solution, a method for manufacturing a positive electrode for a lithium secondary battery, a positive electrode for a lithium secondary battery manufactured by the method, and a lithium secondary battery including the positive electrode for a lithium secondary battery. [Means for solving the problem]

[0011] In one aspect of the present invention, there is provided a method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer according to the following embodiment.

[0012] The first embodiment is preparing an aqueous slurry containing a first binder polymer including polyvinylidene fluoride-based polymer particles having a melting point of 50 to 150°C and a first conductive material in a weight ratio of 0.5:1 to 8:1; and coating at least one surface of a metal current collector with the aqueous slurry, and then heat-treating the coating at a temperature higher than the melting point of the polyvinylidene fluoride-based polymer particles, followed by drying, thereby forming an adhesion-promoting layer.

[0013] The second embodiment is the first embodiment, The present invention relates to a method for producing a positive electrode current collector coated with an adhesion-promoting layer, wherein the melting point of the polyvinylidene fluoride polymer is 70 to 150°C, more specifically 90 to 150°C.

[0014] The third embodiment is the first or second embodiment, The polyvinylidene fluoride-based polymer is a copolymer of vinylidene fluoride and hexafluoropropylene, and the method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer is also disclosed.

[0015] A fourth embodiment is any one of the first to third embodiments, The polyvinylidene fluoride polymer has a weight average molecular weight of 700,000 to 1,300,000, more specifically, 800,000 to 1,100,000.

[0016] A fifth embodiment is any one of the first to fourth embodiments, The present invention relates to a method for producing a positive electrode current collector coated with an adhesion-promoting layer, wherein the polyvinylidene fluoride polymer particles have an average particle size of 10 nm to 3 μm.

[0017] The sixth embodiment is any one of the first to fifth embodiments, The present invention relates to a method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer, wherein the polyvinylidene fluoride-based polymer particles have an average particle size of 100 nm to 1,000 nm, and the first conductive material has an average particle size of 10 nm to 1,000 nm.

[0018] A seventh embodiment relates to a method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer, wherein the average particle size of the polyvinylidene fluoride-based polymer particles is 3 to 20 times the average particle size of the first conductive material in the sixth embodiment.

[0019] The eighth embodiment is any one of the first to seventh embodiments, The present invention relates to a method for producing a positive electrode current collector coated with an adhesion-promoting layer, wherein the drying is carried out at a temperature 10 to 80° C. higher than the melting point of the polyvinylidene fluoride-based polymer particles.

[0020] According to another aspect of the present invention, there is provided a positive electrode current collector coated with an adhesion promoting layer according to the following embodiment.

[0021] The ninth embodiment is a metal current collector; an adhesion-promoting layer formed on at least one surface of the metal current collector and including a first binder polymer and a first conductive material in a weight ratio of 0.5:1 to 8:1; the first binder polymer includes a polyvinylidene fluoride-based polymer; the first binder polymer is dispersed in an island-like manner on the surface of the metal current collector; The present invention relates to a positive electrode current collector coated with an adhesion-promoting layer, wherein the melting point of the polyvinylidene fluoride polymer is 50 to 150°C.

[0022] The tenth embodiment is the ninth embodiment, The present invention relates to a positive electrode current collector coated with an adhesion-promoting layer, wherein the melting point of the polyvinylidene fluoride polymer is 70 to 150°C, more specifically 90 to 150°C.

[0023] The eleventh embodiment is the ninth or tenth embodiment, The present invention relates to a positive electrode current collector coated with an adhesion promoting layer, wherein the polyvinylidene fluoride-based polymer is a copolymer of vinylidene fluoride and hexafluoropropylene.

[0024] A twelfth embodiment is any one of the ninth to eleventh embodiments, The polyvinylidene fluoride polymer has a weight average molecular weight of 700,000 to 1,300,000, more specifically, 800,000 to 1,100,000, in the positive electrode current collector coated with the adhesion-promoting layer.

[0025] In another aspect, the present invention provides a method for manufacturing a positive electrode for a lithium secondary battery according to the following embodiment.

[0026] The thirteenth embodiment is Preparing a positive electrode current collector coated with an adhesion promoting layer by the manufacturing method according to any one of the first to eighth embodiments; and laminating a positive electrode active material layer, including a positive electrode active material, a second conductive material, and a second binder polymer, on the adhesion-promoting layer and adhering the positive electrode active material layer to the adhesion-promoting layer.

[0027] The fourteenth embodiment is the thirteenth embodiment, The present invention relates to a method for manufacturing a positive electrode for a lithium secondary battery, wherein the metal current collector is made of aluminum, and the positive electrode active material is a positive electrode active material represented by the following Chemical Formula 1: [Chemical formula 1] Li 1+a Fe 1-x M x (PO 4-b )X b (M is one or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and X is one or more elements selected from the group consisting of F, S, and N, and -0.5≦a≦+0.5, 0≦x≦0.5, and 0≦b≦0.1.)

[0028] The fifteenth embodiment is the thirteenth or fourteenth embodiment, The second binder polymer is at least one selected from the group consisting of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), and poly(vinylidene fluoride-chlorotrifluoroethylene).

[0029] A sixteenth embodiment is any one of the thirteenth to fifteenth embodiments, The method for manufacturing a positive electrode for a lithium secondary battery is characterized in that the thickness of the adhesion-promoting layer is 50 to 5,000 nm based on the thickness of the adhesion-promoting layer on one surface of the metal current collector, and the thickness of the positive electrode active material layer is 40 to 200 μm based on the thickness of the positive electrode active material layer on one surface of the adhesion-promoting layer.

[0030] According to another aspect of the present invention, there is provided a positive electrode for a lithium secondary battery according to the following embodiment.

[0031] The seventeenth embodiment is A positive electrode current collector coated with the adhesion promoting layer according to any one of the ninth to twelfth embodiments; and a positive electrode active material layer attached to the adhesion-promoting layer, the positive electrode active material layer including a positive electrode active material, a second conductive material, and a second binder polymer.

[0032] The eighteenth embodiment is the seventeenth embodiment, The metal current collector is made of aluminum, and the positive electrode active material is a positive electrode active material represented by the following Chemical Formula 1: [Chemical formula 1] Li 1+a Fe 1-x M x (PO 4-b )X b (M is one or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and X is one or more elements selected from the group consisting of F, S, and N, and -0.5≦a≦+0.5, 0≦x≦0.5, and 0≦b≦0.1.)

[0033] The 19th embodiment is the 17th or 18th embodiment, The second binder polymer is at least one selected from the group consisting of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), and poly(vinylidene fluoride-chlorotrifluoroethylene).

[0034] A 20th embodiment is any one of the 17th to 19th embodiments, The thickness of the adhesion-promoting layer is 50 to 5,000 nm based on the thickness of the adhesion-promoting layer on one surface of the metal current collector, and the thickness of the positive electrode active material is 40 to 200 μm based on the thickness of the positive electrode active material layer on one surface of the adhesion-promoting layer.

[0035] A twenty-first embodiment provides a lithium secondary battery including the positive electrode according to any one of the seventeenth to twentieth embodiments. [Effects of the Invention]

[0036] According to one embodiment of the present invention, an aqueous slurry for forming an adhesion-promoting layer, which includes polyvinylidene fluoride-based polymer particles having a predetermined melting point range and a first conductive material in a predetermined content ratio range, is coated on a metal current collector and dried at a temperature higher than the melting point. The melted and solidified polyvinylidene fluoride-based polymer of the adhesion-promoting layer is dispersed in islands on the surface of the current collector. That is, the dispersed polyvinylidene fluoride-based polymer does not cover the entire surface of the current collector. As a result, the adhesion-promoting layer improves adhesion between the positive electrode active material layer and the current collector, resulting in low interfacial resistance.

[0037] Furthermore, by using a polyvinylidene fluoride-based polymer having a predetermined melting point range, even if the aqueous slurry is dried at a relatively low temperature to reduce energy consumption, the polyvinylidene fluoride-based polymer particles melt and solidify, thereby exhibiting good adhesive performance as an adhesion-promoting layer. Furthermore, even when the polymer is applied to a lithium secondary battery containing an electrolyte, the polymer has resistance to dissolution in the electrolyte, thereby enabling the adhesive strength with the positive electrode to be maintained.

[0038] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention, serve to further understand the technical concept of the present invention, so the present invention should not be interpreted as being limited to the matters depicted in the drawings. Note that the shape, size, scale, or ratio of elements in the drawings attached to this specification may be exaggerated to emphasize a clearer description. [Brief explanation of the drawings]

[0039] [Figure 1] 1 is an SEM photograph of an adhesion-promoting layer formed in Example 1. [Figure 2] 1 is a DSC chart for polymer A used in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0040] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in this specification and claims should not be construed as being limited to their ordinary or dictionary meanings, but should be construed as meanings and concepts corresponding to the technical concept of the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of terms in order to best explain the invention. Therefore, it should be understood that the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiment of the present invention and do not represent the entire technical concept of the present invention, and therefore, various equivalents and modifications that can be substituted therefor may exist at the time of filing this application.

[0041] According to one aspect of the present invention, there is provided a method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer, comprising: An aqueous slurry containing a first binder polymer containing polyvinylidene fluoride polymer particles having a melting point of 50 to 150° C. and a first conductive material in a weight ratio of 0.5:1 to 8:1 is prepared.

[0042] The slurry for forming the adhesion-promoting layer is an aqueous slurry using water as a dispersion medium.

[0043] A solvent such as isopropyl alcohol, acetone, ethanol, or butyl alcohol may be optionally added to the water-based slurry to lower the surface energy and improve the coatability.

[0044] The aqueous slurry contains a first binder polymer to improve the adhesive strength between the metal current collector and the positive electrode active material layer, and in the present invention, the first binder polymer contains particles of a polyvinylidene fluoride-based polymer having a melting point of 50 to 150° C. The use of a particulate polyvinylidene fluoride-based polymer improves the resistance increase phenomenon of the adhesion-promoting layer.

[0045] The average particle size of the polyvinylidene fluoride polymer particles may be, for example, 10 nm to 3 μm in terms of dispersibility and storage safety. In particular, the average particle size of the polyvinylidene fluoride polymer particles may be 100 nm to 1,000 nm in consideration of improving the binding strength to the positive electrode active material layer, phase stability in the slurry, and solvent resistance to the electrolyte. Furthermore, the average particle size of the polyvinylidene fluoride polymer particles may be 3 to 20 times the average particle size of the first conductive material.

[0046] If the melting point of the polyvinylidene fluoride-based polymer is less than 50°C, it is more likely to be dissolved in the electrolyte solution used during battery assembly, resulting in a decrease in adhesive strength with the electrode. Furthermore, if the melting point exceeds 150°C, the drying temperature of the aqueous slurry (described below) becomes excessively high, increasing energy consumption and reducing the adhesive strength improvement effect. Therefore, the melting point of the polyvinylidene fluoride-based polymer may be more specifically 70 to 150°C, even more specifically 90 to 150°C, and most specifically 100 to 140°C. The polyvinylidene fluoride-based polymer may be, for example, a vinylidene fluoride-hexafluoropropylene copolymer, but is not limited thereto.

[0047] The weight-average molecular weight of the polyvinylidene fluoride polymer may be 700,000 to 1,300,000, more specifically 800,000 to 1,100,000. When the weight-average molecular weight is in this range, the adhesive strength with the positive electrode active material layer is further increased.

[0048] Of course, the aqueous slurry may further contain other binder polymers in the form of particles or in the form of a solution in water, in addition to the polyvinylidene fluoride-based polymer particles described above, within the limits not impairing the object of the present invention.

[0049] Meanwhile, the aqueous slurry contains a first conductive material to suppress an increase in the resistance of the positive electrode. The content of the first conductive material may be, for example, but is not limited to, 10 to 200 parts by weight based on 100 parts by weight of the first binder polymer. The average particle size of the first conductive material may be, but is not limited to, 10 nm to 1,000 nm, taking into account dispersibility and conductivity in the slurry.

[0050] The first conductive material is not particularly limited as long as it is conductive and does not induce side reactions with other elements of the battery. For example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black (super-p), acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fiber or metal fiber; carbon nanotubes such as MW-CNT or SW-CNT; metal powders such as carbon fluoride, 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 can be used. These materials can be used alone or in combination to reduce interfacial resistance.

[0051] The weight ratio of the first binder polymer containing polyvinylidene fluoride-based polymer particles to the first conductive material in the aqueous slurry is 0.5:1 to 8:1. If the weight ratio is less than 0.5:1, the adhesive strength is poor, and if the weight ratio exceeds 8:1, the interface resistance becomes excessively high. Considering these aspects, the weight ratio of the polyvinylidene fluoride-based polymer particles to the first conductive material may be 1:1 to 5:1.

[0052] To adjust the viscosity, one or more thickeners may be added to the aqueous slurry, including, but not limited to, carboxymethyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, casein, methyl cellulose, and the like.

[0053] In addition to the above-mentioned components, the aqueous slurry may of course further contain other additives such as dispersants within limits that do not impair the object of the present invention.

[0054] Next, the prepared aqueous slurry is coated on at least one surface of a metal current collector, and the coating is heat-treated at a temperature higher than the melting point of the polyvinylidene fluoride polymer particles and dried to form an adhesion-promoting layer.

[0055] A metal current collector such as aluminum is used as the positive electrode current collector. In particular, aluminum can be used in the form of foil. Aluminum foil is easily oxidized in air, forming a surface layer made of aluminum oxide. Therefore, a current collector made of aluminum is interpreted as including a current collector having an aluminum oxide surface layer formed by the oxidation of aluminum on the surface. The thickness of the metal current collector can typically be, but is not limited to, 3 to 500 μm.

[0056] The aqueous slurry may be applied to a metal current collector using a conventional method and apparatus. Examples of suitable methods include bar coating using a Meyer bar, gravure coating, two-roll reverse coating, vacuum slot die coating, and two-roll coating. The adhesion-promoting layer is formed on at least one surface of the metal current collector, i.e., on one or both surfaces of the metal current collector, to improve adhesion between the metal current collector and a positive electrode active material layer (described later). The thickness of the adhesion-promoting layer (based on the thickness of an adhesion-promoting layer formed on one surface of the metal current collector, not both surfaces) may be, for example, 50 to 5,000 nm, more specifically, 100 to 1,000 nm, taking into account the effect of improving adhesion and the degree of increase in positive electrode resistance, but is not limited thereto.

[0057] The metal current collector coated with the aqueous slurry is heat-treated at a temperature higher than the melting point of the polyvinylidene fluoride-based polymer particles and dried to form an adhesion-promoting layer. Specifically, the drying step can be performed at a temperature 10 to 80°C higher than the melting point of the polyvinylidene fluoride-based polymer particles, but is not limited thereto.

[0058] When the polyvinylidene fluoride-based polymer particles are heat-treated and dried at a temperature higher than the melting point of the polyvinylidene fluoride-based polymer particles, the melted polyvinylidene fluoride-based polymer particles undergo a drying process, and then solidify as the temperature drops, forming an adhesion-promoting layer on the metal current collector. In this case, the polyvinylidene fluoride-based polymer in the adhesion-promoting layer is dispersed in the form of islands on the surface of the current collector. That is, the dispersed polyvinylidene fluoride-based polymer does not cover the entire surface of the current collector. As a result, the adhesion-promoting layer improves the adhesion between the positive electrode active material layer and the current collector, resulting in low interfacial resistance.

[0059] Furthermore, as described above, the use of a polyvinylidene fluoride-based polymer having a predetermined melting point range allows the aqueous slurry to be dried at a relatively low temperature to reduce energy consumption, and the formed adhesion-promoting layer exhibits good adhesion performance. This adhesion-promoting layer is resistant to dissolution in an electrolyte solution when applied to a lithium secondary battery containing the electrolyte solution, thereby maintaining adhesion to the positive electrode.

[0060] The positive electrode current collector coated with the adhesion promoting layer according to one embodiment manufactured by the above-described manufacturing method is a metal current collector; an adhesion-promoting layer formed on at least one surface of the metal current collector and including a first binder polymer and a first conductive material in a weight ratio of 0.5:1 to 8:1; the first binder polymer includes a polyvinylidene fluoride-based polymer; the first binder polymer is dispersed in an island-like manner on the surface of the metal current collector; The melting point of the polyvinylidene fluoride polymer is 50 to 150°C.

[0061] The metal current collector, the first binder polymer, the first conductive material, and the adhesion-promoting layer that constitute the positive electrode current collector coated with the adhesion-promoting layer have been described above, and therefore, further description thereof will be omitted.

[0062] After preparing a positive electrode current collector coated with an adhesion-promoting layer by the above-described preparation method, a positive electrode active material layer including a positive electrode active material, a second conductive material, and a second binder polymer is laminated on the adhesion-promoting layer and adhered to the adhesion-promoting layer to prepare a positive electrode for a lithium secondary battery.

[0063] The positive electrode active material layer contains a positive electrode active material, a second conductive material, and a second binder polymer, as in the case of a typical positive electrode active material layer for a lithium secondary battery.

[0064] The positive electrode active material may be a typical positive electrode active material used in lithium secondary batteries, such as a lithium transition metal oxide, etc. In particular, the positive electrode active material may be a positive electrode active material represented by the following Chemical Formula 1: [Chemical formula 1] Li 1+a Fe 1-x M x (PO 4-b )X b (M is one or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and X is one or more elements selected from the group consisting of F, S, and N, and -0.5≦a≦+0.5, 0≦x≦0.5, and 0≦b≦0.1.)

[0065] The positive electrode active material of Formula 1 is a lithium iron phosphate-based compound, and has a problem of low adhesion to an aluminum current collector. Therefore, when applying the adhesion-promoting layer according to the present invention, there is an increasing industrial need for an improved adhesion to the current collector.

[0066] The second binder polymer, which binds the positive electrode active materials together, may be a binder polymer typically used in positive electrode mixtures. Examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. One or a mixture of two or more of these may be used. More preferably, the second binder polymer may be a polyvinylidene fluoride-based polymer, which further improves interlayer adhesion through interaction with the polyvinylidene fluoride-based polymer of the adhesion-promoting layer. In this regard, the second binder polymer may preferably be at least one selected from the group consisting of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), and poly(vinylidene fluoride-chlorotrifluoroethylene). The binder may be included in an amount of 1 to 30 wt % based on the total weight of the positive electrode active material layer.

[0067] The second conductive material used in the positive electrode active material may be the first conductive material of the adhesion promoting layer, which may be used independently. The second conductive material may be typically included in an amount of 1 to 30 wt % based on the total weight of the positive electrode active material layer.

[0068] The method for laminating the positive electrode active material layer and adhering the adhesion promoting layer to it may be any method known in the art.

[0069] For example, a method may be used in which a composition for forming a positive electrode active material layer, including a positive electrode active material, a second conductive material, and a second binder polymer, is applied onto the adhesion-promoting layer, followed by drying and rolling.

[0070] The solvent used in the composition for forming the positive electrode active material layer may be a solvent commonly used in the art. Examples include dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, and water. These may be used alone or in combination. The amount of solvent used should be sufficient to dissolve the binder polymer, disperse the conductive material and positive electrode active material, and provide a viscosity that provides excellent thickness uniformity during subsequent coating for positive electrode fabrication, taking into account the coating thickness and manufacturing yield of the coating solution.

[0071] The polyvinylidene fluoride polymer contained in the adhesion-promoting layer has fluidity when heated and pressurized. For example, when heated and pressurized at a temperature higher than the glass transition temperature of the polyvinylidene fluoride polymer, in a temperature range from the melting point (Tm) of the polymer - 60°C to the melting point (Tm) of the binder polymer + 60°C, more specifically, in a temperature range from the melting point (Tm) of the binder polymer - 50°C to the melting point (Tm) of the binder polymer + 50°C, or even more specifically, in a temperature range from the melting point (Tm) of the binder polymer - 40°C to the melting point (Tm) of the binder polymer + 30°C, the binder polymer in the adhesion-promoting layer flows due to the heat and adheres to the surface of the positive electrode active material layer in contact with the adhesion-promoting layer.

[0072] In one embodiment of the positive electrode for a lithium secondary battery manufactured by the above-described manufacturing method, the thickness of the positive electrode active material layer (based on the thickness of the positive electrode active material layer formed on one side of the adhesion-promoting layer, not on both sides of the adhesion-promoting layer, after rolling) may be, but is not limited to, 40 to 200 μm.

[0073] The adhesive strength of the positive electrode active material layer is preferably 30 gf / 2 cm or more, more preferably 40 gf / 2 cm or more. The interface resistance of the positive electrode active material layer is 3 Ω cm. 2 It is desirable that the resistance is less than 2Ωcm. 2 It is more desirable that:

[0074] The positive electrode for a lithium secondary battery according to one embodiment manufactured by the above-described manufacturing method is a positive electrode current collector coated with the adhesion-promoting layer; The positive electrode active material layer is deposited on the adhesion-promoting layer and includes a positive electrode active material, a second conductive material, and a second binder polymer.

[0075] The metal current collector, binder polymer, conductive material, and positive electrode active material that constitute the positive electrode for such a lithium secondary battery have been described above, and therefore further description thereof will be omitted.

[0076] According to yet another embodiment of the present invention, there is provided a positive electrode for a lithium secondary battery and a lithium secondary battery including the positive electrode.

[0077] The lithium secondary battery may further include a battery container that houses the electrode assembly including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0078] In the lithium secondary battery, the negative electrode includes a negative electrode current collector and a negative electrode active material layer located on the negative electrode current collector.

[0079] The negative electrode current collector is not particularly limited as long as it does not induce chemical changes in the battery and has high conductivity. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, and aluminum-cadmium alloys can be used. The negative electrode current collector typically has a thickness of 3 to 500 μm. As with the positive electrode current collector, the surface of the current collector can be formed with fine irregularities to enhance the binding strength of the negative electrode active material. The negative electrode current collector can be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0080] The negative electrode active material layer may include a negative electrode active material and, optionally, a binder and a conductive material. For example, the negative electrode active material may be prepared by applying a negative electrode-forming composition including the negative electrode active material and, optionally, the binder and the conductive material to a negative electrode current collector and drying the composition, or by casting the negative electrode-forming composition on a separate support, peeling the composition from the support, and laminating the resulting film on the negative electrode current collector.

[0081] The negative electrode active material may be a compound capable of reversible lithium intercalation and deintercalation. 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 alloys, Sn alloys, and Al alloys; metal oxides capable of doping and dedoping lithium, such as SiOβ(0<β<2), SnO2, vanadium oxide, and lithium vanadium oxide; and composites containing the metallic compounds and carbonaceous materials, such as Si-C composites and Sn-C composites. A mixture of any one or more of these may be used. Alternatively, a metallic lithium thin film may be used as the negative electrode active material. Carbon materials may include both low-crystalline carbon and high-crystalline carbon. Typical low-crystalline carbons include soft carbon and hard carbon, and typical high-crystalline carbons include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature-fired carbons such as petroleum or coal tar pitch-derived cokes.

[0082] The binder and conductive material may be the same as those described above for the positive electrode.

[0083] Meanwhile, in the lithium secondary battery, the separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without limitation. It is particularly desirable for the separator to have low resistance to electrolyte ion movement and excellent electrolyte impregnation capability. Specifically, a porous polymer film, such as a porous polymer film made from a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof, can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made from high-melting-point glass fiber or polyethylene terephthalate fiber, can also be used. Separators coated with ceramic components or polymer materials to ensure heat resistance or mechanical strength can also be used, and can be selectively used in a single-layer or multi-layer structure.

[0084] Furthermore, examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the production of lithium secondary batteries, but are not limited to these.

[0085] Specifically, the electrolyte may be an electrolytic solution containing an organic solvent and a lithium salt.

[0086] The organic solvent may be any solvent that can act as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, examples of the organic solvent include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate. Examples of suitable solvents include carbonate-based solvents such as PC (carbonate); alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a C2-C20 linear, branched, or cyclic hydrocarbon group that may contain a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolanes. Among these, carbonate-based solvents are preferred, and mixtures of cyclic carbonates (e.g., ethylene carbonate or propylene carbonate) with high ionic conductivity and high dielectric constants, which can enhance the charge / discharge performance of batteries, and low-viscosity linear carbonate compounds (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate) are more preferred. In this case, the cyclic carbonate and linear carbonate should be mixed in a volume ratio of about 1:1 to about 1:9 to achieve excellent electrolyte performance.

[0087] The lithium salt can be any compound capable of providing lithium ions used in lithium secondary batteries. Specifically, examples of the lithium salt include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, and LiB(C2O4)2. The lithium salt concentration is preferably within a range of 0.1 to 2.0 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion mobility.

[0088] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds (e.g., difluoroethylene carbonate), pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, to improve battery life, inhibit battery capacity loss, and improve battery discharge capacity. In this case, the additives may be contained in an amount of 0.1 to 5 wt % based on the total weight of the electrolyte.

[0089] Such lithium secondary batteries are useful in the fields of portable devices such as mobile phones, notebook PCs, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0090] Therefore, according to another embodiment of the present invention, there is provided a battery module including the lithium secondary battery as a unit cell, and a battery pack including the same.

[0091] The battery module or battery pack may be used as a power source for one or more medium- to large-sized devices including power tools; electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems.

[0092] While the present invention may be embodied in many different forms, it is to be understood that the invention is not limited to the specific embodiments set forth herein. [Example]

[0093] Example 1 Polymer A (Solvay, vinylidene fluoride-hexafluoropropylene copolymer, VDF:HFP=3:1 (weight ratio), average particle size: 250 nm, melting point: 100°C, Mw=1,080,000) and Denka carbon black (BET=60m 2 / g, DBP = 200ml / 100g) was dispersed in water at a weight ratio of 2:1, and then Daicel 2200 was added as a thickener at 1 / 5 the weight of the binder polymer to prepare an aqueous slurry with a solid content of 10%. The aqueous slurry was then applied to both sides of a 20μm-thick aluminum foil using a microgravure coater and dried at 120°C for 3 minutes to form an adhesion-promoting layer on the aluminum foil. LiFe(PO4), polyvinylidene fluoride (Mw = 630,000) as a second binder polymer, and Denka carbon black (BET = 60m) as a conductive material were then coated on the formed adhesion-promoting layer. 2 / g, DBP=200ml / 100g) and a positive electrode active material slurry mixed at a ratio of 96:2:2 was applied to the substrate, dried at 140°C for 10 minutes, and then rolled to prepare a positive electrode.

[0094] Lithium metal was used as the negative electrode, and a separator (Celgard) was placed between the negative and positive electrodes to form an electrode assembly. This was punched into a coin shape, and an electrolyte solution of 1M LiPF6 dissolved in a mixed solvent of propylene carbonate (PC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) (PC:EMC:EC=3:4:3) was injected to fabricate an experimental lithium secondary battery.

[0095] Example 2 The same procedure as in Example 1 was carried out except for the changes shown in Table 1 below.

[0096] Example 3 The same procedure as in Example 1 was carried out except for the changes shown in Table 1 below.

[0097] Example 4 The same procedure as in Example 1 was carried out, except that Polymer B (Solvay, vinylidene fluoride-hexafluoropropylene copolymer, VDF:HFP=97:3 (weight ratio), average particle size: 250 nm, melting point: 140°C, Mw=800,000) was used as the first binder polymer, and the changes were made as shown in Table 1 below.

[0098] Example 5 The same procedure as in Example 1 was carried out except for the same changes as in Table 1 below. In Example 5, the weight ratio of polymer A: Denka carbon black: Mw-CNT was 2:1:0.1.

[0099] Comparative Example 1 The same procedure as in Example 1 was carried out except for the changes shown in Table 1 below.

[0100] Comparative Example 2 The same procedure as in Example 1 was carried out, except that Polymer C (Solvay, polyvinylidene fluoride, average particle size: 250 nm, melting point: 168°C, Mw = 600,000) was used as the first binder polymer and was changed as shown in Table 1 below.

[0101] Comparative Example 3 A lithium secondary battery was fabricated in the same manner as in Example 1, except that an adhesion promoting layer was formed as follows.

[0102] Polymer D (Solvay, polyvinylidene fluoride, melting point: 168°C, Mw=630,000) as a first binder polymer and Denka carbon black (trade name: Li-250) were added in a weight ratio of 2:1 to prepare a 10% oil-based slurry in which Denka carbon black was dispersed and Polymer D was dissolved in NMP. The oil-based slurry was then applied to both sides of a 20 μm-thick aluminum foil and dried at 120°C for 3 minutes to form an adhesion-promoting layer on the aluminum foil.

[0103] Comparative Example 4 Polymer E (Solvay, polyvinylidene fluoride, melting point: 170°C, Mw = 1,000,000) was used as the first binder polymer, and Denka carbon black (BET = 60m 2 The same procedure as in Comparative Example 3 was carried out, except that Denka carbon black was dispersed in NMP (DBP = 200 ml / 100 g, DBP = 200 ml / 100 g) at a weight ratio of 2:1, and polymer D was dissolved in NMP to prepare a 10% oil-based slurry.

[0104] Example 6 Polymer A (Solvay, vinylidene fluoride-hexafluoropropylene copolymer, VDF:HFP = 3:1 (weight ratio), average particle size: 250 nm, melting point: 100°C, Mw = 1,080,000) as the first binder polymer and Denka carbon black (trade name: Li-250) with an average particle size of 37 nm as the first conductive material were dispersed in water at a weight ratio of 2:1, and then Daicel 2200 was added as a thickener at 1 / 5 the weight of the binder polymer to prepare an aqueous slurry with a solids content of 10%. Next, the aqueous slurry was applied to both sides of a 20 μm thick aluminum foil using a microgravure coater and dried at 120°C for 3 minutes to form an adhesion-promoting layer on the aluminum foil. A positive electrode active material slurry, which was a 96:2:2 mixture of LiFe(PO), polyvinylidene fluoride (Mw=630,000) as a second binder polymer, and Denka carbon black (trade name: Li-250) as a second conductive material, was applied onto the formed adhesion-promoting layer, dried at 140°C for 10 minutes, and then rolled to produce a positive electrode.

[0105] An electrode assembly was fabricated by stacking lithium metal as the anode and cathode with a separator (Celgard) between them, which was then punched into a coin shape and filled with an electrolyte solution of 1M LiPF6 dissolved in a mixed solvent of propylene carbonate (PC), ethyl methyl carbonate (EMC), and ethylene carbonate (EC) (PC:EMC:EC=3:4:3) to fabricate an experimental lithium secondary battery.

[0106] Example 7 The same procedure as in Example 6 was carried out, except that Denka carbon black (trade name: Li-435) having an average particle size of 23 nm was used as the first conductive material, and the ratio of polymer A to the conductive material was changed to 1:1.

[0107] Example 8 The same procedure as in Example 6 was carried out, except for the changes shown in Table 2 below.

[0108] Example 9 The same procedure as in Example 6 was carried out, except that Polymer B (Solvay, vinylidene fluoride-hexafluoropropylene copolymer, VDF:HFP=97:3 (weight ratio), average particle size: 250 nm, melting point: 140°C, Mw=800,000) was used as the first binder polymer and was changed as shown in Table 2 below.

[0109] Example 10 LiNi instead of LiFe(PO4) 0.50 Co 0.20 Mn 0.30 The same procedure as in Example 6 was carried out, except that O2 was used, polyvinylidene fluoride (Mw=630,000) was used as the second binder polymer, and Super-P was used as the second conductive material in a weight ratio of 97.5:1.5:1.

[0110] Comparative Example 5-6 The same procedure as in Example 6 was carried out, except for the changes shown in Table 2 below.

[0111] Comparative Example 7 LiNi instead of LiFe(PO4) 0.50 Co 0.20 Mn 0.30 The same procedure as in Example 6 was carried out, except that O2 was used, polyvinylidene fluoride (Mw=630,000) was used as the second binder polymer, and Super-P was used as the second conductive material in a weight ratio of 97.5:1.5:1.

[0112] Comparative Example 8 A lithium secondary battery was fabricated in the same manner as in Example 6, except that an adhesion promoting layer was formed as follows.

[0113] Polymer C (Solvay, polyvinylidene fluoride, melting point: 168°C, Mw=880,000) as a first binder polymer and Denka carbon black (trade name: Li-250) were added in a weight ratio of 2:1 to prepare a 10% oil-based slurry in which Denka carbon black was dispersed and Polymer C was dissolved in NMP. The oil-based slurry was then applied to both sides of a 20 μm-thick aluminum foil and dried at 120°C for 3 minutes to form an adhesion-promoting layer on the aluminum foil.

[0114] <Melt point measurement of binder polymer> The melting point of the binder polymer was measured using DSC. Using a TA DSC2500 device, 5 to 10 mg of sample was placed in the flask, and a thermal scan was performed in the following order: heating from 50 to 250°C at a heating rate of 10°C / min under a nitrogen atmosphere, followed by cooling at a rate of 10°C / min, and then heating from 50 to 250°C at a heating rate of 10°C / min.

[0115] Figure 2 is a DSC chart for Polymer A in Example 1. Referring to Figure 2, the melting point was obtained from the endothermic reaction of the peak obtained in the second heating, and the melting point was confirmed from the temperature of the peak.

[0116] <Measurement of weight-average molecular weight of polymers> 0.04 g of polymer was dissolved in 10 g of tetrahydrofuran to prepare a sample. The standard (polystyrene) and sample were filtered through a 0.45 μm pore filter and then injected into a GPC injector. The number-average molecular weight, weight-average molecular weight, and polydispersity of the acrylic polymer were determined by comparing the elution time of the sample with the calibration curve of the standard. Measurements were performed using a GPC (Infinity II 1260, Agilient) at a flow rate of 1.00 mL / min and a column temperature of 35.0°C.

[0117] <Measuring the average particle size of polymer particles> After photographing the polymer particles with an SEM, the average length of the major axis was measured as the average particle size.

[0118] <Measurement of Average Particle Size of Conductive Material> The average particle size D50 of the conductive material was measured using the laser diffraction method. After dispersing the conductive material in a dispersion medium, the average particle size D50 at the 50% standard of the particle size distribution was calculated using a laser diffraction particle size measuring device (Microtac MT 3000).

[0119] <Adhesive Strength Evaluation> The positive electrodes produced by the examples and comparative examples were punched out to a width of 2 cm × a length of 10 cm or more using a punching machine. After attaching double-sided tape to glass as a base plate (width 2.5 cm × length 7.5 cm × thickness 1T), the punched electrodes were attached in parallel. The electrode attached to the tape was 6 cm, and the adhesive strength of the electrode was measured using a texture analyzer equipment (LLOYD) while maintaining a 90° angle with the base plate.

[0120] <WET Adhesive Strength Evaluation> For the evaluation of the WET adhesive strength, the foil coated with the electrode was held at 130 °C for 24 hours by a vacuum drying oven to remove moisture. After sealing the electrode together with the electrolytic solution in an aluminum pouch, it was held in a 70 °C oven for two weeks, and then the adhesive strength was measured. At this time, in order to remove the remaining electrolytic solution, the electrode was washed with a DMC cleaning solution and completely dried before measurement.As the solubility resistance of the adhesion promoting layer is poorer compared to before the evaluation of the resistance to the electrolytic solution, the adhesive strength of the adhesion promoting layer to the electrolytic solution tends to decrease when applied to a lithium secondary battery.

[0121] <Interface Resistance Evaluation> The positive electrodes produced by the examples and comparative examples were punched out to a width of 5 cm × a length of 5 cm using a punching machine. After inputting the thickness of the punched electrode, the thickness of the aluminum foil, and the specific resistance value of the current collector (2.82E-06) using an Mp tester (manufactured by HIOKI), the punched electrode was placed under the chip with a built-in probe, and the bar was lowered for measurement.

[0122]

Table 1

[0123] [Table 2]

[0124] From the results of Tables 1 and 2, it can be seen that the positive electrodes of Examples 1 to 10, which are provided with an adhesion-promoting layer containing a binder polymer and a conductive material according to the present invention, have improved adhesion and reduced interfacial resistance when using a specific binder component.

[0125] On the other hand, Comparative Example 1, which does not contain a conductive material, exhibits high interfacial resistance, and Comparative Example 2, which does not use a binder polymer having a specific melting point of the present invention, exhibits inferior adhesive strength compared to the positive electrodes of Examples 1 and 2. Furthermore, Comparative Examples 3, 4, and 8, which use an oil-based slurry in which a binder polymer is dissolved in a solvent, exhibit high interfacial resistance.

[0126] In addition, it was confirmed that Comparative Examples 5 and 7, in which the weight ratio of the first conductive material to the first binder polymer was too low, had too high interfacial resistance, and Comparative Example 6, in which the weight ratio of the first conductive material to the first binder polymer was too high, had a significantly reduced adhesive strength.

Claims

1. preparing an aqueous slurry containing a first binder polymer including polyvinylidene fluoride-based polymer particles having a melting point of 50 to 150°C and a first conductive material in a weight ratio of 0.5:1 to 8:1; and coating the aqueous slurry on at least one surface of a metal current collector, and then heat-treating the aqueous slurry at a temperature higher than the melting point of the polyvinylidene fluoride-based polymer particles and drying the coated surface to form an adhesion-promoting layer. The method for manufacturing a positive electrode current collector includes coating an adhesion promoting layer on the surface of the metal current collector, the adhesion promoting layer being dispersed in the form of islands on the surface of the metal current collector.

2. 2. The method of claim 1, wherein the melting point of the polyvinylidene fluoride polymer is 70 to 150°C.

3. 2. The method for manufacturing a positive electrode current collector coated with an adhesion-promoting layer according to claim 1, wherein the polyvinylidene fluoride-based polymer is a copolymer of vinylidene fluoride and hexafluoropropylene.

4. 2. The method of claim 1, wherein the polyvinylidene fluoride polymer has a weight average molecular weight of 700,000 to 1,300,000.

5. 2. The method of claim 1, wherein the polyvinylidene fluoride-based polymer particles have an average particle size of 10 nm to 3 μm.

6. 2. The method of claim 1, wherein the polyvinylidene fluoride-based polymer particles have an average particle size of 100 nm to 1,000 nm, and the first conductive material has an average particle size of 10 nm to 1,000 nm.

7. 7. The method for manufacturing a positive electrode current collector coated with an adhesion promoting layer according to claim 6, wherein the average particle size of the polyvinylidene fluoride-based polymer particles is 3 to 20 times the average particle size of the first conductive material.

8. 2. The method of claim 1, wherein the drying is performed at a temperature 10 to 80° C. higher than the melting point of the polyvinylidene fluoride-based polymer particles.

9. a metal current collector; an adhesion-promoting layer formed on at least one surface of the metal current collector, the adhesion-promoting layer including a first binder polymer and a first conductive material in a weight ratio of 0.5:1 to 8:1; the first binder polymer includes a polyvinylidene fluoride-based polymer; the first binder polymer is dispersed in an island-like manner on the surface of the metal current collector, The adhesion-promoting layer-coated positive electrode current collector is characterized in that the melting point of the polyvinylidene fluoride-based polymer is 50 to 150°C.

10. 10. The positive electrode current collector coated with an adhesion-promoting layer according to claim 9, wherein the melting point of the polyvinylidene fluoride-based polymer is 70 to 150°C.

11. 10. The positive electrode current collector coated with an adhesion-promoting layer according to claim 9, wherein the polyvinylidene fluoride-based polymer is a copolymer of vinylidene fluoride and hexafluoropropylene.

12. 10. The positive electrode current collector coated with an adhesion-promoting layer according to claim 9, wherein the polyvinylidene fluoride-based polymer has a weight-average molecular weight of 700,000 to 1,300,000.

13. Producing a positive electrode current collector coated with an adhesion promoting layer by the manufacturing method of any one of claims 1 to 8; and laminating a cathode active material layer, the cathode active material layer including a cathode active material, a second conductive material, and a second binder polymer, on the adhesion promoting layer to adhere the cathode active material layer to the adhesion promoting layer.

14. 14. The method for manufacturing a positive electrode for a lithium secondary battery according to claim 13, wherein the metal current collector is made of aluminum, and the positive electrode active material is represented by the following Chemical Formula 1: [Chemical formula 1] Li １＋ａ Fe １－ｘ M ｘ (PO ４－ｂ )X ｂ (M is one or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and X is one or more elements selected from the group consisting of F, S, and N, and -0.5≦a≦+0.5, 0≦x≦0.5, and 0≦b≦0.1.)

15. 14. The method for manufacturing a positive electrode for a lithium secondary battery according to claim 13, wherein the second binder polymer is at least one selected from the group consisting of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), and poly(vinylidene fluoride-chlorotrifluoroethylene).

16. 14. The method for manufacturing a positive electrode for a lithium secondary battery according to claim 13, wherein the thickness of the adhesion promoting layer is 50 to 5,000 nm based on the thickness of the adhesion promoting layer on one surface of the metal current collector, and the thickness of the positive electrode active material layer is 40 to 200 μm based on the thickness of the positive electrode active material layer on one surface of the adhesion promoting layer.

17. A positive electrode current collector coated with the adhesion-promoting layer according to any one of claims 9 to 12; a positive electrode active material layer attached to the adhesion-promoting layer, the positive electrode active material layer including a positive electrode active material, a second conductive material, and a second binder polymer.

18. 18. The positive electrode for a lithium secondary battery according to claim 17, wherein the metal current collector is made of aluminum, and the positive electrode active material is represented by the following Chemical Formula 1: [Chemical formula 1] Li １＋ａ Fe １－ｘ M ｘ (PO ４－ｂ )X ｂ (M is one or more elements selected from the group consisting of Al, Mg, Ni, Co, Mn, Ti, Ga, Cu, V, Nb, Zr, Ce, In, Zn, and Y, and X is one or more elements selected from the group consisting of F, S, and N, and -0.5≦a≦+0.5, 0≦x≦0.5, and 0≦b≦0.1.)

19. 18. The positive electrode for a lithium secondary battery of claim 17, wherein the second binder polymer is at least one selected from the group consisting of polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene), and poly(vinylidene fluoride-chlorotrifluoroethylene).

20. 18. The positive electrode for a lithium secondary battery according to claim 17, wherein the thickness of the adhesion promoting layer is 50 to 5,000 nm based on the adhesion promoting layer on one surface of the metal current collector, and the thickness of the positive electrode active material is 40 to 200 μm based on the positive electrode active material layer on one surface of the adhesion promoting layer.

21. A lithium secondary battery comprising the positive electrode according to claim 17.

Images