Positive electrode for lithium ion secondary battery, positive electrode sheet for lithium ion secondary battery, and lithium ion secondary battery

Abstract

To provide a positive electrode for a lithium ion secondary battery, a positive electrode sheet for a lithium ion secondary battery, and a method for manufacturing the same, which exhibit high performance and can reduce manufacturing cost.SOLUTION: A positive electrode for a lithium ion secondary battery comprises: metal foil 9 (collector); a first combined material layer 11 containing a positive electrode active substance and provided in one surface of the metal foil 9; and a second combined material layer 12 partially covered with the first combined material layer 11 and constituted mainly by particles different from those of an active substance. The second combined material layer 12 is provided on one end 11a side of the first combined material layer 11 in a boundary between a forming region of the first combined material layer 11 and an unforming region of the first combined material layer 11. One end 12a of the second combined material layer 12 is positioned between one surface of the metal foil 9 and a lower surface of the first combined material layer 11 in the forming region of the first combined material layer 11, and the other end 12b is positioned in the unforming region, and contains conductive substances dispersed in the first and second combined material layers 11 and 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a positive electrode for a lithium ion secondary battery, a positive electrode sheet for a lithium ion secondary battery, and a method for producing the same. [Background technology]

[0002] In recent years, in light of environmental issues, interest in electric vehicles and hybrid vehicles has increased, and the technical demand for higher energy density and capacity of the secondary batteries that power these vehicles is increasing.

[0003] Electrodes for such secondary batteries are made from electrode sheets that are made by coating and drying a slurry containing an active material on a strip of metal foil such as aluminum or copper. Methods for coating the active material can be broadly divided into intermittent coating and continuous coating.

[0004] As a structure for suppressing electrical contact between an exposed portion of a positive electrode foil and a negative electrode due to thermal shrinkage of a separator in a lithium ion secondary battery, a configuration in which an insulating layer is provided at an electrode end is described in Patent Documents 1 to 15. Of these, Patent Documents 8, 11, and 13 to 15 have an insulating layer containing a conductive material.

[0005] The electrodes used in secondary batteries designed for high energy density tend to be designed with thin metal foils as current collectors, while the active material film is becoming thicker to achieve higher capacity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-186945 A [Patent Document 2] JP 2004-259625 A [Patent Document 3] JP 2012-204334 A [Patent Document 4] Japanese Patent Application Publication No. 10-74535 [Patent Document 5] Special Publication No. 2005-509247 [Patent Document 6] JP 2003-151535 A [Patent Document 7] JP 2006-147392 A [Patent Document 8] JP 2012-114079 A [Patent Document 9] JP 2012-74359 A [Patent Document 10] Special Publication No. 2009-518808 [Patent Document 11] JP 2009-238487 A [Patent Document 12] JP 2011-81920 A [Patent Document 13] JP 2007-095656 A [Patent Document 14] JP 2012-178326 A [Patent Document 15] International Publication No. 2012 / 128160 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when applying an insulating material after thick-film coating, it is difficult to apply a thin insulating material because the gap between the tip of the coating equipment and the workpiece cannot be narrowed. This causes problems such as an increase in cell thickness due to an increase in the thickness of the active material wrap, an increase in the cost of insulating materials, and a risk of cracks occurring during drying.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a high-performance positive electrode for a lithium-ion secondary battery that can reduce production costs, a positive electrode sheet for a lithium-ion secondary battery, and a method for producing the same. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, each aspect of the present invention employs the following configuration.

[0010] A first aspect relates to a positive electrode sheet for a lithium ion secondary battery. The positive electrode sheet for a lithium ion secondary battery according to the first aspect comprises: a first composite layer containing at least a positive electrode active material and a conductive material, and a second composite layer mainly composed of particles different from the positive electrode active material are continuously formed on both sides or one side of a current collector which is a strip-shaped sheet in a longitudinal direction of the sheet, At least one end of the first mixture layer in the short direction covers at least one end of the second mixture layer in the short direction; The surface of at least one end in the short dimension direction of the second mixture layer contains a conductive material.

[0011] A second aspect relates to a positive electrode for a lithium ion secondary battery. A positive electrode for a lithium ion secondary battery according to a second aspect of the present invention comprises: A positive electrode for a lithium ion secondary battery produced from the positive electrode sheet for a lithium ion secondary battery according to the first aspect, The positive electrode sheet is formed by cutting out an area including the first mixture layer and the second mixture layer from the positive electrode sheet.

[0012] A third aspect relates to a lithium ion secondary battery. A lithium ion secondary battery according to a third aspect is a lithium ion secondary battery that uses the positive electrode for a lithium ion secondary battery according to the second aspect.

[0013] Another aspect of the present invention may be a program that causes at least one computer to execute the method of the present disclosure, or a computer-readable recording medium having such a program recorded thereon. This recording medium includes a non-transitory tangible medium. The computer program includes computer program code that, when executed by a computer, causes the computer to carry out the manufacturing method on a manufacturing apparatus for a positive electrode sheet for a lithium ion secondary battery.

[0014] Any combination of the above components, and any transformation of the present invention into a method, device, system, recording medium, computer program, etc., are also effective as aspects of the present invention.

[0015] Furthermore, the various components of the present invention do not necessarily have to be independent entities, but may be formed as a single member by multiple components, one component may be formed from multiple components, one component may be a part of another component, or part of one component may overlap with part of another component, etc.

[0016] In addition, although the method and computer program of the present invention describe a number of steps in a sequential order, the order does not limit the order in which the steps are executed. Therefore, when implementing the method and computer program of the present invention, the order of the steps can be changed as long as it does not affect the content.

[0017] Furthermore, the steps of the method and computer program of the present invention are not limited to being executed at different timings, and therefore a step may occur while another step is being executed, or the execution timing of a step may overlap partially or entirely with the execution timing of another step, etc. Effect of the Invention

[0018] According to the above aspects, it is possible to provide a high-performance positive electrode for a lithium-ion secondary battery, which enables reduction in manufacturing costs, a positive electrode sheet for a lithium-ion secondary battery, and a method for manufacturing the same. [Brief description of the drawings]

[0019] [Figure 1]FIG. 2 is a partial cross-sectional view of an electrode sheet for illustrating the configuration of a positive electrode for the lithium-ion secondary battery according to the first embodiment. [Diagram 2] FIG. 2 is a top view of the electrode sheet of FIG. [Diagram 3] 2 is a flowchart showing an example of the steps of a method for producing the electrode sheet of FIG. 1. [Figure 4] 2 is a block diagram showing an example of a hardware configuration of a computer that realizes a control device of the electrode sheet manufacturing apparatus of FIG. 1. FIG. [Diagram 5] FIG. 4 is a top view of an electrode sheet according to a modified embodiment of the first embodiment. [Figure 6] 6 is a flowchart showing an example of the steps of a method for producing the electrode sheet of FIG. 5. [Figure 7] 6 is a diagram for explaining a manufacturing process of the electrode sheet of FIG. 5. FIG. [Figure 8] 1 is a schematic diagram showing an example of a configuration of a battery according to an embodiment of the present invention. [Figure 9] FIG. 2 is a diagram showing the procedure of a method for producing the electrode sheets of Example 1 and Comparative Example 1. [Figure 10] 13 is a diagram for explaining a case where a foreign matter is mixed into the electrode sheets of Example 2 and Comparative Example 2. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are given the same reference numerals and the description will be omitted as appropriate.

[0021] (First embodiment) The electrode according to this embodiment is a positive electrode for a lithium ion secondary battery. Fig. 1 is a partial cross-sectional view of an electrode sheet 10 for explaining the configuration of a positive electrode for a lithium ion secondary battery according to this embodiment. The positive electrode for a lithium ion secondary battery is produced by cutting out the electrode sheet 10 of Fig. 2. Fig. 1 is a cross-sectional view of the electrode sheet 10 of Fig. 2 taken along line II as viewed from the direction of arrow I.

[0022] The positive electrode for a lithium ion secondary battery of this embodiment includes a current collector (hereinafter also referred to as metal foil 9), a first composite layer 11 containing at least a positive electrode active material provided on at least one surface of the current collector (metal foil 9), and a second composite layer 12 that is partially covered by the first composite layer 11 and mainly composed of particles different from the active material. The second composite layer 12 is provided on at least one end 11a side of the first composite layer 11 in a boundary portion 19 between a formation region (hereinafter also referred to as a coating region 15) where the first composite layer 11 is formed and a non-formation region (hereinafter also referred to as a non-coating region 17) where the first composite layer 11 is not formed. One end 12a of the second composite layer 12 is located between at least one surface of the metal foil 9 and the lower surface of the first composite layer 11 in the coating region 15 of the first composite layer 11, and the other end 12b is located in the non-coating region 17. The first composite layer 11 and the second composite layer 12 contain a conductive material dispersed therein.

[0023] 2 is a top view of an electrode sheet 10 according to an embodiment of the present invention. In this embodiment, the electrode sheet 10 is produced by a continuous coating method, but the method of producing the electrode sheet 10 is not limited thereto and may be an intermittent coating method as described later. The electrode sheet 10 is formed by forming a first composite layer 11 and a second composite layer 12 on at least one surface of a strip-shaped metal foil 9 while the electrode sheet 10 is transported in the longitudinal direction Dx.

[0024] The electrode sheet 10 of this embodiment has a first composite layer 11 containing at least a positive electrode active material, and a second composite layer 12 which is partially covered by the first composite layer 11 and is composed mainly of particles different from the active material, formed continuously in the longitudinal direction Dx of the electrode sheet 10 and in parallel with the longitudinal direction Dx of the electrode sheet 10 on both sides or one side of a current collector (metal foil 9), which is a strip-shaped sheet taken up on a roll of a coating device. At least one end 11 a of the first mixture layer 11 on the side in the short length direction Dy of the electrode sheet 10 is formed so as to cover a part of the second mixture layer 12 .

[0025] <Electrode configuration> The configuration of the electrode will be described in detail below. The electrode of this embodiment is a positive electrode for a lithium ion battery.

[0026] The first mixture layer 11 contains an electrode active material, and if necessary, contains a binder such as a binder resin, a conductive assistant, a thickener, and the like.

[0027] The electrode active material contained in the first mixture layer 11 is not particularly limited as long as it is a normal positive electrode active material that can be used for the positive electrode of a lithium ion battery. For example, lithium and transition metal composite oxides such as lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-manganese composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-aluminum composite oxide, lithium-nickel-cobalt-aluminum composite oxide, lithium-nickel-manganese-cobalt composite oxide, lithium-nickel-manganese-aluminum composite oxide, and lithium-nickel-cobalt-manganese-aluminum composite oxide; transition metal sulfides such as TiS2, FeS, and MoS2; MnO, VO5, and VO 13 , transition metal oxides such as TiO2, and olivine-type lithium phosphate. The olivine-type lithium phosphate contains, for example, at least one element selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe, as well as lithium, phosphorus, and oxygen. These compounds may have some elements partially substituted with other elements in order to improve their properties.

[0028] Among these, olivine-type lithium iron phosphate, lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-manganese composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-aluminum composite oxide, lithium-nickel-cobalt-aluminum composite oxide, lithium-nickel-manganese-cobalt composite oxide, lithium-nickel-manganese-aluminum composite oxide, and lithium-nickel-cobalt-manganese-aluminum composite oxide are preferred. These positive electrode active materials have a high working potential, a large capacity, and a large energy density. The positive electrode active material may be used alone or in combination of two or more kinds.

[0029] The content of the positive electrode active material is preferably 85 parts by mass or more and 99.8 parts by mass or less when the total amount of the first mixture layer 11 is taken as 100 parts by mass. The density of the first mixture layer 11 is 3.40 g / cm 3 That's all.

[0030] The binder resin contained in the first mixture layer 11 is appropriately selected depending on the application. For example, a fluorine-based binder resin that can be dissolved in a solvent, or a water-based binder that can be dispersed in water can be used.

[0031] The fluorine-based binder resin is not particularly limited as long as it can be formed into an electrode and has sufficient electrochemical stability, and examples thereof include polyvinylidene fluoride-based resins and fluororubbers. These fluorine-based binder resins may be used alone or in combination of two or more. Among these, polyvinylidene fluoride-based resins are preferred. The fluorine-based binder resins can be used by dissolving them in a solvent such as N-methyl-pyrrolidone (NMP).

[0032] The aqueous binder is not particularly limited as long as it can be used to form an electrode and has sufficient electrochemical stability, and examples thereof include polytetrafluoroethylene resins, polyacrylic acid resins, styrene-butadiene rubbers, polyimide resins, etc. These aqueous binders may be used alone or in combination of two or more. Among these, styrene-butadiene rubbers are preferred. In this embodiment, the aqueous binder refers to a binder that can be dispersed in water to form an aqueous emulsion solution. When using a water-based binder, a thickener can be further used. The thickener is not particularly limited, but examples thereof include cellulose polymers such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose, and their ammonium salts and alkali metal salts; polycarboxylic acids; polyethylene oxide; polyvinylpyrrolidone; polyacrylates such as sodium polyacrylate; polyvinyl alcohol; and other water-soluble polymers.

[0033] The content of the binder resin is preferably 0.1 parts by mass or more and 10.0 parts by mass or less when the total amount of the first mixture layer 11 is 100 parts by mass. When the content of the binder resin is within the above range, the balance between the coatability of the electrode slurry, the binding property of the binder, and the battery characteristics is further improved. In addition, when the content of the binder resin is equal to or less than the upper limit, the ratio of the electrode active material is increased, and the capacity per mass of the electrode is increased, which is preferable, whereas when the content of the binder resin is equal to or more than the lower limit, the electrode peeling is suppressed, which is preferable.

[0034] The content of the conductive assistant is preferably 0.1 parts by mass or more and 5.0 parts by mass or less when the total amount of the first mixture layer 11 is 100 parts by mass. When the content of the conductive assistant is within the above range, the balance between the coatability of the electrode slurry, the binding property of the binder, and the battery characteristics is further improved. Furthermore, when the content of the conductive assistant is equal to or less than the upper limit, the proportion of the electrode active material is increased, and the capacity per mass of the electrode is increased, which is preferable.When the content of the conductive assistant is equal to or more than the lower limit, the conductivity of the electrode is improved, which is preferable.

[0035] The conductive materials dispersed in the first mixture layer 11 and the second mixture layer 12 may be of the same type.

[0036] The conductive material contained in the first mixture layer 11 and the second mixture layer 12 preferably contains at least one type of carbon material selected from carbon nanotubes, carbon nanohorns, graphene, carbon nanobrushes, carbon black, acetylene black, and ketjen black.

[0037] The resistivity of the second composite layer 12 is preferably in the range of 1 to 100 times the resistivity of the first composite layer 11. If it is less than 1, it is not possible to cause a gentle discharge in the lithium ion secondary battery. If it exceeds 100 times, the insulating effect is poor, and the original effect of suppressing the current between the exposed part of the metal foil 9 of the positive electrode and the negative electrode in the lithium ion secondary battery is not achieved.

[0038] Furthermore, the conductive material dispersed in the second mixture layer 12 is preferably contained in an amount of 0.1 to 20.0 parts by mass based on the total amount of the second mixture layer 12. If it is less than 0.1 parts by mass, it is not possible to cause a gentle discharge in the lithium ion secondary battery. If it is more than 20.0 parts by mass, the insulating effect is poor, and the original effect of suppressing the current between the exposed part of the metal foil 9 of the positive electrode and the negative electrode in the lithium ion secondary battery is not achieved.

[0039] A binder may be further dispersed in the second mixture layer 12. The amount of the binder contained in the second mixture layer 12 is preferably 0.5 parts by mass or more and 60 parts by mass or less with respect to the total amount of the second mixture layer 12.

[0040] When the ratio of the binder contained in the second mixture layer 12 to the total amount of the second mixture layer 12 is less than the lower limit of 0.5 parts by mass, the binding between the second mixture layer 12 and the metal foil 9 serving as the current collector cannot be maintained. When the ratio of the binder in the second mixture layer 12 exceeds the upper limit of 60 parts by mass, the viscosity becomes too high and coating becomes difficult. Even if coating is possible, when the first mixture layer 11 and the second mixture layer 12 are simultaneously dried and solidified, the binder on the second mixture layer 12 side diffuses to the first mixture layer 11 side, and the resistance of the first mixture layer 11 becomes too high, which may affect the output characteristics of the battery.

[0041] The thickness of the first mixture layer 11 is not particularly limited, and can be appropriately set according to the desired characteristics. For example, it can be set thick from the viewpoint of energy density, and can be set thin from the viewpoint of output characteristics. The thickness (thickness of one side) of the first mixture layer 11 can be appropriately set within a range of, for example, 10 μm to 250 μm, preferably 20 μm to 200 μm, and more preferably 30 μm to 150 μm.

[0042] The maximum thickness of the second mixture layer 12 is preferably smaller than the minimum thickness of the first mixture layer 11. The average thickness of the second mixture layer 12 is preferably in the range of 3 μm or more and 90% or less of the average thickness of the first mixture layer 11.

[0043] If the thickness of the second mixture layer 12 is less than 3 μm, the film thickness becomes too thin and the original function of suppressing electrical contact between the exposed portion of the positive electrode metal foil 9 and the negative electrode cannot be fully maintained. If the thickness of the second mixture layer 12 exceeds 90% of the thickness of the first mixture layer 11, when the first mixture layer 11 is applied, the step becomes too large at the boundary portion of the end of the second mixture layer 12, and the gap between the tip of the coating equipment and the workpiece does not fall within the appropriate range for applying a uniform film thickness.

[0044] The density of the second composite layer 12 is 0.5 g / cm 3 More than 3.0g / cm 3 The density of the second composite layer 12 is preferably in the range of 0.7 g / cm. 3 More than 2.8g / cm3 The range is as follows:

[0045] The density of the second composite layer 12 is 0.5 g / cm 3 If the density of the second mixture layer 12 is less than 3.0 g / cm, the porosity of the second mixture layer 12 becomes too large, and when the separator of the battery undergoes thermal shrinkage, the original function of suppressing electrical contact between the exposed portion of the metal foil 9 of the positive electrode and the negative electrode cannot be sufficiently maintained. 3 If it exceeds this value, the conductivity of lithium ions passing through the mixture layer deteriorates, and the steady-state battery characteristics cannot be ensured.

[0046] The average particle size of the electrode active material contained in the first mixture layer 11 is preferably 1 μm or more, more preferably 2 μm or more, from the viewpoint of suppressing side reactions during charging and discharging and suppressing a decrease in charge and discharge efficiency, and is preferably 100 μm or less, more preferably 50 μm or less, from the viewpoint of input / output characteristics and electrode fabrication (smoothness of the electrode surface, etc.). Here, the average particle size refers to the particle size (median size: D50) at an integrated value of 50% in the particle size distribution (volume basis) by the laser diffraction scattering method.

[0047] The average particle size of the particles contained as the main component in the second mixture layer 12 is preferably in the range of 0.1 μm to 3.0 μm. The proportion of particles having a particle size of 0.2 μm or less and particles having a particle size of 2 μm or more is preferably 10 volume % or less.

[0048] The particles contained as a main component in the second mixture layer 12 include one or more materials selected from alumina, silica, thermoplastic resin, ionizing radiation curable resin, thermosetting resin, and insulating ink.

[0049] It is preferable that the binder contained in the second composite layer 12 is of the same type as the binder contained in the first composite layer 11, and that the ratio of the binder contained in the second composite layer 12 to the total amount of the second composite layer 12 is greater than the ratio of the binder contained in the first composite layer 11 to the total amount of the first composite layer 11.

[0050] The current collector layer (metal foil 9) according to this embodiment is not particularly limited, and may be made of aluminum, stainless steel, nickel, titanium, or an alloy thereof. Its shape may be, for example, a foil, a flat plate, or a mesh. In particular, any one of aluminum foil, aluminum alloy foil, and iron-stainless steel alloy foil may be suitably used. The thickness of the metal foil 9 is preferably 12 μm or less.

[0051] <Method of manufacturing electrode sheet 10> 3 is a flow chart showing an example of the steps of a method for producing the electrode sheet 10 of this embodiment. The method for producing the electrode sheet 10 includes at least a first coating step (A1), a second coating step (B1), and a solidifying step (C) in this order.

[0052] Although not shown, the manufacturing system for the electrode sheet 10 mainly includes a coating device and a drying device. The coating device includes a roller that takes up the sheet of the metal foil 9 and transports it in the longitudinal direction Dx of the sheet, and at least two die coaters that coat at least one surface of the metal foil 9 with a paste or slurry mixture that forms the first mixture layer 11 and the second mixture layer 12, respectively.

[0053] The roller of the coating device and the die coater are controlled by a control device (a computer described later) not shown, and each step of the manufacturing method of the electrode sheet 10 of this embodiment is realized.

[0054] In the first application step A1, a mixture for forming a second composite layer 12 is continuously applied to both sides or a part of one side of a current collector (metal foil 9), which is a strip-shaped sheet wound around a roll of a manufacturing device, in the longitudinal direction Dx of the metal foil 9 sheet. This step A1 forms the second composite layer 12. This mixture contains any one conductive material (M) selected from a paste-like mixture (M1) containing at least a conductive granular, fibrous or scaly solid material and a dispersion medium, a conductive thermoplastic resin (M2), a conductive thermosetting resin (M3), and a conductive ink (M4).

[0055] In the second coating step B1 following the first coating step A1, a paste-like mixture (P) containing at least a positive electrode active material and a dispersion medium is continuously coated in the longitudinal direction Dx of the sheet of metal foil 9. A first mixture layer 11 is formed by this step B1. Then, in a solidification step C following the second coating step B1, the formed product (the first mixture layer 11 and the second mixture layer 12) is solidified by drying.

[0056] In step B1, the mixture (P) is applied to both a portion of the region 16 to which the mixture containing the conductive substance (M) was applied in step A1, which includes one end of the metal foil 9 sheet in the short length direction Dy, and a portion to which the mixture containing the conductive substance (M) is not applied, and the mixture (P) is prevented from applying to a portion of the region 16 to which the mixture containing the conductive substance (M) was applied, which includes the other end 12b of the metal foil 9 sheet in the short length direction Dy.

[0057] In the step C, the mixture containing the conductive material (M) and the mixture (P) are solidified at the same time.

[0058] Here, a method for preparing the electrode slurry that is applied to form the first mixture layer 11 will be described. The electrode slurry can be prepared by mixing an electrode active material and, if necessary, a binder resin, a conductive assistant, and a thickener. The blending ratio of the electrode active material, the binder resin, and the conductive assistant is the same as the content ratio of the electrode active material, the binder resin, and the conductive assistant in the electrode active material layer, so a description thereof will be omitted here.

[0059] The electrode slurry is prepared by dispersing or dissolving an electrode active material, and, if necessary, a binder resin, a conductive assistant, and a thickener in a solvent. The procedure for mixing the components is not particularly limited. For example, the electrode active material and the conductive assistant are dry-mixed, and then a binder resin and a solvent are added and wet-mixed to prepare the electrode slurry. The mixer used here is not particularly limited and may be a known mixer such as a ball mill or a planetary mixer. The solvent used for the electrode slurry may be an organic solvent such as N-methyl-2-pyrrolidone (NMP) or water.

[0060] The electrode slurry can be applied onto the current collector layer by a generally known method. For example, the die coater method, the doctor blade method, the extrusion method, and the curtain method can be mentioned. Among these, the die coater method is preferred in that it is possible to obtain a good surface condition of the coating layer in accordance with the physical properties such as the viscosity and drying property of the electrode slurry.

[0061] The method for drying the electrode slurry applied onto the current collector layer in step C is not particularly limited, and examples thereof include a method of indirectly heating the electrode slurry from the current collector layer side or the already dried electrode active material layer side using a heated roll to dry the electrode slurry; a method of drying the electrode slurry using electromagnetic waves such as an infrared, far-infrared, or near-infrared heater; and a method of indirectly heating the electrode slurry by applying hot air to the current collector layer side or the already dried electrode active material layer side to dry the electrode slurry.

[0062] The electrode sheet 10 produced by the above steps can be cut to a predetermined size to obtain multiple electrodes. The means for cutting the electrodes from the electrode sheet 10 is not particularly limited, but the electrode sheet 10 can be cut using a blade made of metal or the like, for example.

[0063] 2, one method is to cut the sheet parallel to the short direction Dy to cut out a plurality of electrodes of a predetermined width. Depending on the application, the sheet can be punched out to a predetermined size along a line in the direction Dx perpendicular to the cutting line so as to have the desired outer dimensions as a current collector, thereby obtaining an electrode for a battery.

[0064] FIG. 4 is a block diagram showing an example of a hardware configuration of a computer 100 that realizes a control device for an electrode sheet manufacturing apparatus according to an embodiment of the present invention. Each of the control devices is realized by at least one computer 100. The computer 100 includes a CPU (Central Processing Unit) 102, a memory 104, a program 110 for realizing the control device loaded into the memory 104, a storage 105 for storing the program 110, an I / O (Input Output) 106, and a communication interface (I / F) 107 for network connection. The CPU 102 and each element are connected to each other via a bus 109, and the entire computer 100 is controlled by the CPU 102. However, the method of connecting the CPUs 102 and the like to each other is not limited to bus connection.

[0065] The CPU 102 reads out the program 110 stored in the storage 105 into the memory 104 and executes it, thereby realizing each step of the manufacturing method of the electrode sheet 10 using the control device.

[0066] The control device is realized by any combination of hardware and software of the computer 100. Those skilled in the art will understand that there are various modifications to the realization method and device.

[0067] The program 110 may be recorded on a recording medium readable by the computer 100. The recording medium is not particularly limited and may take various forms. The program may be loaded from the recording medium into the memory 104 of the computer 100, or may be downloaded to the computer 100 via a network and then loaded into the memory 104.

[0068] The recording medium for recording the program 110 includes a non-transitory tangible medium usable by the computer 100, in which program code readable by the computer 100 is embedded. When the program 110 is executed on the computer 100, it causes the computer 100 to execute a manufacturing method for the electrode sheet 10 that realizes a control device.

[0069] As described above, according to this embodiment, step A1 of forming the second composite layer 12 is performed before step A2 of forming the first composite layer 11, so that the second composite layer 12 can be formed as a thin film. This reduces the material cost of the second composite layer 12 and suppresses the occurrence of cracks when the second composite layer 12 dries.

[0070] Furthermore, according to this embodiment, by including a conductive assistant in the second mixture layer 12, it is possible to provide the second mixture layer 12 with the same electronic conductivity as the first mixture layer 11, and form a current path in the second mixture layer 12. In addition, since the resistance of the second mixture layer 12 is lower than that of the first mixture layer 11, the current path from the negative electrode 126 to the positive electrode 121 easily flows toward the second mixture layer 12. As a result, as shown in FIG. 10(a), when a metallic foreign matter 32 is mixed into the second mixture layer 12 during the process, the metallic foreign matter 32 is converted into a metal ion (M + When the metal ions reach the negative electrode, they undergo a reduction reaction on the surface of the negative electrode, which is at a reduction potential, and are then deposited as metal (M), as shown in Figure 10(b).

[0071] However, according to the present embodiment, even if the deposited metal grows and penetrates the separator 120, when it reaches the second mixture layer 12, a current path is formed throughout the second mixture layer 12 via the conductive material in the second mixture layer 12. This allows for gentle discharge, and prevents abnormal heat generation due to local short circuiting.

[0072] On the other hand, as shown in FIG. 10(c), if an insulating layer 34 is provided instead of the second composite layer 12, when the precipitated metal grows and penetrates the separator 120, the positive electrode 121 and the negative electrode 126 become connected, causing a short circuit and resulting in a self-discharge failure.

[0073] FIG. 10 shows an example in which a foreign matter 32 has been mixed into the range d1 where only the second composite layer 12 is present. However, according to this embodiment, even if a foreign matter 32 has been mixed into the range d2 where the first composite layer 11 and the second composite layer 12 are present, or into the range d3 where only the first composite layer 11 is present, the positive electrode 121 and the negative electrode 126 are not connected, and no self-discharge failure occurs.

[0074] Furthermore, if the overlapping portion between the second mixture layer 12 and the first mixture layer 11 does not have electrical conductivity, it will not contribute to the charge / discharge reaction, and the effective capacity of the battery will be small. In this embodiment, the first mixture layer 11 and the second mixture layer 12 have electrical conductivity, which solves this problem.

[0075] In the example of Patent Document 13, in order to reliably cover the exposed area of ​​the current collector with the protective layer, the protective layer must be applied so that it covers the active material layer to some extent. However, if the active material layer exists, the die for forming the protective layer cannot be brought close enough to the foil, making it impossible to form a thin film.

[0076] In addition, if a masking tape is applied to the active material layer side, the active material layer itself will peel off from the current collector when the masking tape is peeled off after the application of the protective layer is completed. For this reason, it is not possible to apply a masking tape to the active material layer side, and the area of ​​the protective layer on the active material layer must be set to be large in consideration of the stability and variability of the device used for application. In addition, the area of ​​the protective layer on the active material layer varies greatly depending on the manufacturing conditions, such as the meandering of the foil during application and the positional deviation of the application device. For this reason, the protective layer is formed not only on the inclined portion of the end of the active material layer, but also on the active material layer inside it.

[0077] Furthermore, if, after forming the active material layer, masking tape is applied and a protective layer is applied to the ends of the active material layer, there will be large steps and slopes at the boundaries between the masking tape and the foil and between the active material layer and the foil, which will make the thickness prone to vary and will cause liquid to pool, resulting in a thicker protective layer than necessary.

[0078] When multiple electrodes designed with such a configuration are stacked, a local increase in thickness (step) occurs in the stacking direction only in the area where the protective layer overlaps the active material layer. In other words, the film thickness of the entire battery is not uniform, and only the part with the protective layer protrudes in the thickness direction.

[0079] On the other hand, during the manufacturing and use of lithium-ion batteries, problems such as non-uniform pressure being applied in the stacking direction of the battery can occur, such as non-removal of gases and non-uniform charge / discharge reactions. In addition, in areas where there is a large step or inclination in the coated area, which is the boundary between the masking tape and the foil and the boundary between the active material layer and the foil, liquid pools occur when the protective layer is applied as described above, and drying does not progress sufficiently in those areas, so the binder does not disperse near the foil, the peel strength is weakened, and the protective layer may peel off from there in subsequent processes or when the battery is used.

[0080] In addition, liquid pools formed in the protective layer, and other problems that could occur when the protective layer was not dried sufficiently before subsequent processes were carried out were that the conductive additive has a tendency to aggregate more easily than the filler (such as alumina), so only the conductive additive aggregates, which is likely to cause resistance variations in the protective layer. In other words, the conductive additive is likely to be distributed only on the surface of the protective layer, and coupled with the thick film thickness, electrical conduction does not occur in the film thickness direction, so when the conductive additive is deposited from the negative electrode and reaches the protective layer on the positive electrode, it becomes difficult to form a current path throughout the protective layer through the conductive material in the protective layer, which causes a gentle discharge and prevents abnormal heat generation due to local short circuits.

[0081] When removing the masking tape, the protective layer formed on the surface of the current collector foil may be peeled off together with the masking tape. In addition, there is a risk that the second composite layer 12 may not be completely formed on the exposed portion of the positive electrode foil facing the negative electrode due to misalignment when applying the masking tape.

[0082] In this embodiment, since the conductive second mixture layer 12 is formed before the first mixture layer 11, the second mixture layer 12 can be formed with a uniform thickness even when the second mixture layer 12 is thin, while controlling the application position with high accuracy and precision. The conductive assistant in the second mixture layer 12 is uniformly distributed, and the conductivity in the thickness direction is maintained in every part of the second mixture layer 12, and the resistance is maintained below a certain level.

[0083] Even in the overlapping region between first mixture layer 11 and second mixture layer 12, the conductive assistant in second mixture layer 12 is uniformly distributed and the film thickness is thin, so that electrons contributed by active material particles present on the side of first mixture layer 11 farther from the current collecting foil are also transmitted to the foil side through the conductive path in second mixture layer 12. In other words, the resistance to the movement of electrons on the surface of the active material particles to the foil is reduced, and as a result, the active material in such overlapping regions also contributes to charging and discharging, so that a large battery capacity can be ensured.

[0084] Since the conductivity in the thickness direction is maintained in every part of the second composite layer 12 and the resistance is kept below a certain level, it is possible to induce a gentle discharge. Since the increase in film thickness is kept small even in the overlapping region of the first composite layer 11 and the second composite layer 12, there is no local increase in thickness (step) when the electrodes are stacked, and the battery can be pressed uniformly. This allows sufficient gas release from inside the battery during the manufacturing process, and a uniform charge / discharge reaction occurs even during use, ensuring stable battery characteristics.

[0085] (Modification of the first embodiment) In the first embodiment, an example has been described in which the electrode sheet 10 is produced by a method in which the electrode active material is continuously applied to the metal foil 9. As a modification of the first embodiment, an example in which the electrode sheet 10 is produced by a method in which the electrode active material is intermittently applied to the metal foil 9 will be described below.

[0086] FIG. 5 is a top view of the electrode sheet 10 of this modified embodiment. In the electrode sheet 10 of this embodiment, a first composite layer 11 containing at least a positive electrode active material and a second composite layer 12 which is partially covered by the first composite layer 11 and is composed mainly of particles other than the active material are intermittently formed in the longitudinal direction Dx of the metal foil 9 on both sides or one side of a current collector (metal foil 9), which is a strip-shaped sheet wound up on a roll, in the longitudinal direction Dx of the metal foil 9, each with a predetermined width in the short direction Dy of the metal foil 9.

[0087] The second composite layer 12 is provided on at least one of the ends 11a of the first composite layer 11 in the longitudinal direction Dx of the metal foil 9 sheet, in the boundary portion 19 between the formation region 15 where the first composite layer 11 is formed and the non-formation region 17 where no active material composite layer is formed. One end 12a of the second composite layer 12 is located between at least one surface of the metal foil 9 and the lower surface of the first composite layer 11 in the formation region 15 of the first composite layer 11, and the other end 12b is located in the non-formation region 17.

[0088] <Method of manufacturing electrode sheet 10> 6 is a flow chart showing an example of the procedure of a method for manufacturing the electrode sheet 10 of this modified embodiment. The method for manufacturing the electrode sheet 10 includes at least a first application step (A2), a second application step (B2), and a solidification step (C) in this order.

[0089] In this modified embodiment, a coating device similar to that of the first embodiment described above can be used, but the coating device of this modified embodiment differs from that of the first embodiment in the arrangement of at least two die coaters, which each apply a paste-like or slurry-like mixture forming the first composite layer 11 and the second composite layer 12 to at least one side of the metal foil 9, relative to the electrode sheet 10.

[0090] Next, each step will be described with reference to FIG. 7(a2), 7(b2), and 7(c2) are cross-sectional views of the electrode sheets 10 of FIGS. 7(a1), 7(b1), and 7(c1) taken along line II-II as viewed in the direction of arrow II. First, a metal foil 9 is prepared in a coating device (FIGS. 7(a1) and 7(a2)).

[0091] Next, in the first coating step A2, the mixture for forming the second composite layer 12 is applied intermittently to both sides or a part of one side of the current collector (metal foil 9), which is a strip-shaped sheet wound around a roll of a manufacturing device, in a predetermined width in the short direction Dy of the sheet and in the long direction Dx. By this step A2, the second composite layer 12 is formed as shown in Fig. 7(b1) and Fig. 7(b2).

[0092] 7(b1) and 7(b2), the region of the dashed line 15 indicates the coating region 15 where the second composite layer 12 is formed. As shown in the drawings, the second composite layer 12 is provided on at least one end 11a side of the coating region where the first composite layer 11 is formed, in a boundary portion 19 between the coating region 15 where the first composite layer 11 is formed and a non-coating region 17 where the first composite layer 11 is not formed.

[0093] The mixture forming the second composite layer 12 includes a paste-like mixture (M1) containing at least a conductive granular, fibrous or scaly solid and a dispersion medium, and any one of a conductive substance (M) selected from a conductive thermoplastic resin (M2), a conductive thermosetting resin (M3) and a conductive ink (M4).

[0094] In the second coating step B2 following the first coating step A2, a paste-like mixture (P) containing at least a positive electrode active material and a dispersion medium is intermittently coated in a predetermined width in the short-length direction Dy of the sheet in the long-length direction Dx. By this step B2, a first mixture layer 11 is formed as shown in Fig. 7(c1) and Fig. 7(c2).

[0095] In this step B2, the mixture (P) is applied so that it covers both the portion of the region 16 to which the mixture containing the conductive substance (M) was applied in step A2, including one end 12a in the longitudinal direction Dx of the metal foil 9, and the portion (non-coated region 17) to which the mixture containing the conductive substance (M) is not applied, and the mixture (P) is prevented from applying to the portion of the region 16 to which the mixture containing the conductive substance (M) is applied, including the other end 12b in the longitudinal direction Dx of the sheet.

[0096] Then, in the solidification step C following the second application step B2, the formed product (the first mixture layer 11 and the second mixture layer 12) is solidified by drying. In this step C, the mixture containing the conductive material (M) and the mixture (P) are solidified at the same time.

[0097] As described above, the electrode sheet 10 of this modified embodiment can also achieve the same effects as those of the first embodiment.

[0098] Although the embodiments of the present invention have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted. Furthermore, the present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention. A battery manufactured using the positive electrode produced in the first embodiment will be described below.

[0099] FIG. 8 is a schematic diagram showing an example of the configuration of a battery 150 according to an embodiment of the present invention. The battery according to this embodiment includes a positive electrode made from the electrode sheet 10 described in the above embodiment. Hereinafter, the battery according to this embodiment will be described as a representative example in which the battery is a laminated battery 150 that is a lithium ion battery.

[0100] The stacked battery 150 includes a battery element in which positive electrodes 121 and negative electrodes 126 are alternately stacked in multiple layers with separators 120 between them, and these battery elements are housed in a container made of flexible film 140 together with an electrolyte (not shown). A positive electrode terminal 131 and a negative electrode terminal 136 are electrically connected to the battery element, and a part or the whole of the positive electrode terminal 131 and the negative electrode terminal 136 are pulled out to the outside of the flexible film 140.

[0101] The positive electrode 121 has a positive electrode active material coated portion (positive electrode active material layer 122) and a non-coated portion on the front and back of the positive electrode current collector layer 123, and the negative electrode 126 has a negative electrode active material coated portion (negative electrode active material layer 127) and a non-coated portion on the front and back of the negative electrode current collector layer 128.

[0102] The portion of the positive electrode collector layer 123 on which the positive electrode active material is not applied is a positive electrode tab 130 for connecting to a positive electrode terminal 131, and the portion of the negative electrode collector layer 128 on which the negative electrode active material is not applied is a negative electrode tab 125 for connecting to a negative electrode terminal 136. The positive electrode tabs 130 are gathered together on a positive electrode terminal 131 and connected together with the positive electrode terminal 131 by ultrasonic welding or the like, and the negative electrode tabs 125 are gathered together on a negative electrode terminal 136 and connected together with the negative electrode terminal 136 by ultrasonic welding or the like. In addition, one end of the positive electrode terminal 131 is drawn out to the outside of the flexible film 140, and one end of the negative electrode terminal 136 is also drawn out to the outside of the flexible film 140.

[0103] As described above, the second mixture layer 12 can be formed at the boundary 124 between the coated portion (coated region 15) (positive electrode active material layer 122) of the positive electrode active material and the non-coated portion (non-coated region 17). One end of the second mixture layer 12 overlaps with the coated portion (coated region 15) (positive electrode active material layer 122) of the positive electrode active material, and the other end extends to the positive electrode tab 130.

[0104] If necessary, an insulating member can be formed at the boundary 129 between the coated portion of the negative electrode active material (negative electrode active material layer 127) and the non-coated portion, and can be formed near the boundary between both the negative electrode tab 125 and the negative electrode active material.

[0105] Usually, the outer dimensions of the negative electrode active material layer 127 are larger than the outer dimensions of the positive electrode active material layer 122 and smaller than the outer dimensions of the separator 120 .

[0106] (Non-aqueous electrolyte containing lithium salt) The nonaqueous electrolyte containing a lithium salt used in this embodiment can be appropriately selected from known electrolytes depending on the type of electrode active material, the application of the lithium ion battery, and the like.

[0107] Specific examples of lithium salts include LiClO4, LiBF6, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10 , LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiC4F9SO3, Li(CF3SO2)2N, lithium lower fatty acid carboxylates, etc.

[0108] The solvent for dissolving the lithium salt is not particularly limited as long as it is a liquid that is usually used to dissolve an electrolyte, and examples of the solvent include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and vinylene carbonate (VC); lactones such as γ-butyrolactone and γ-valerolactone; trimethoxymethane, 1,2-dimethoxyethane, diethyl ether, tetrahydrofuran, and 2-methyltetrahydrofuran. ethers, sulfoxides such as dimethyl sulfoxide, dioxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane, nitrogen-containing solvents such as acetonitrile, nitromethane, formamide, and dimethylformamide, organic acid esters such as methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and ethyl propionate, phosphoric acid triesters and diglymes, triglymes, sulfolanes such as sulfolane and methyl sulfolane, oxazolidinones such as 3-methyl-2-oxazolidinone, and sultones such as 1,3-propane sultone, 1,4-butane sultone, and naphtha sultone. These may be used alone or in combination of two or more.

[0109] (container) In this embodiment, a known material can be used for the container, and it is preferable to use a flexible film 140 from the viewpoint of reducing the weight of the battery. The flexible film 140 can be a film in which a resin layer is provided on the front and back sides of a metal layer serving as a base material. The metal layer can be selected from those having a barrier property such as preventing leakage of the electrolyte and intrusion of moisture from the outside, and aluminum, stainless steel, etc. can be used. At least one surface of the metal layer is provided with a heat-sealable resin layer such as modified polyolefin, and the heat-sealable resin layers of the flexible film 140 are opposed to each other via the battery element, and the periphery of the part that houses the battery element is heat-sealed to form an exterior body. A resin layer such as a nylon film or polyester film can be provided on the surface of the exterior body that is the surface opposite to the surface on which the heat-sealable resin layer is formed.

[0110] (Terminal) In this embodiment, the positive electrode terminal 131 may be made of aluminum or an aluminum alloy, and the negative electrode terminal 136 may be made of copper, a copper alloy, or a nickel-plated version of these. Each terminal is drawn out to the outside of the container, and a heat-sealable resin may be provided in advance at the location where the periphery of the exterior body of each terminal is to be heat-sealed.

[0111] (Insulating material) When forming an insulating member at the boundary 129 between the coated and non-coated portions of the active material, polyimide, glass fiber, polyester, polypropylene, or a material containing any of these may be used. The insulating member can be formed by applying heat to these members to melt them at the boundary 129, or by applying a gel resin to the boundary 129 and drying it.

[0112] (Separator) The separator 120 according to this embodiment preferably includes a resin layer containing a heat-resistant resin as a main component. Here, the resin layer is formed of a heat-resistant resin as a main component. Here, "main component" means that the proportion in the resin layer is 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and may be 100% by mass. The resin layer constituting the separator 120 according to this embodiment may be a single layer or two or more types of layers.

[0113] Examples of the heat-resistant resin that forms the resin layer include one or more selected from polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, poly-m-phenylene terephthalate, poly-p-phenylene isophthalate, polycarbonate, polyester carbonate, aliphatic polyamide, wholly aromatic polyamide, semi-aromatic polyamide, wholly aromatic polyester, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyimide, polyarylate, polyetherimide, polyamideimide, polyacetal, polyether ether ketone, polysulfone, polyethersulfone, fluorine-based resin, polyether nitrile, modified polyphenylene ether, and the like.

[0114] Among these, from the viewpoint of an excellent balance of heat resistance, mechanical strength, stretchability, price, etc., one or more selected from polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, aliphatic polyamide, wholly aromatic polyamide, semi-aromatic polyamide, and wholly aromatic polyester are preferred, one or more selected from polyethylene terephthalate, polybutylene terephthalate, aliphatic polyamide, wholly aromatic polyamide, and semi-aromatic polyamide are more preferred, one or more selected from polyethylene terephthalate and wholly aromatic polyamide are even more preferred, and polyethylene terephthalate is more preferred.

[0115] The resin layer constituting the separator 120 according to the present embodiment is preferably a porous resin layer. With this, when an abnormal current is generated in the lithium ion battery and the temperature of the battery rises, the micropores in the porous resin layer are blocked to cut off the flow of current, and thermal runaway of the battery can be avoided.

[0116] The porosity of the porous resin layer is preferably 20% or more and 80% or less, more preferably 30% or more and 70% or less, and particularly preferably 40% or more and 60% or less, from the viewpoint of the balance between mechanical strength and lithium ion conductivity. The porosity can be calculated from the following formula. ε={1-Ws / (ds·t)}×100 Where, ε: porosity (%), Ws: basis weight (g / m 2 ), ds: True density (g / cm 3 ), t: film thickness (μm).

[0117] The planar shape of the separator 120 according to this embodiment is not particularly limited and can be appropriately selected in accordance with the shapes of the electrodes and current collectors, and can be, for example, rectangular.

[0118] The thickness of the separator 120 according to this embodiment is preferably 5 μm or more and 50 μm or less from the viewpoint of the balance between mechanical strength and lithium ion conductivity.

[0119] As described above, an electrochemical device such as a battery can be assembled using a positive electrode made from the electrode sheet 10 of any of the above embodiments. EXAMPLES

[0120] Example 1 9(a1) to 9(a3) are diagrams showing the steps of a method for producing the electrode sheet 10 of Example 1 of the present invention.

[0121] 9(a1), in Example 1, as described in FIG. 3 and FIG. 6, first, the second composite layer 12 is applied to at least one surface of the metal foil 9 by step A1 or step A2. Therefore, the position of the die coater 22 of the application device for the second composite layer 12 can be set at a height h1 close to the upper surface of the metal foil 9. This can be lower than the position of the die coater 22 of the application device of the comparative example in FIG. 9(b2) described later, i.e., height h2.

[0122] In this manner, die coater 22 can be disposed adjacent to metal foil 9, so that second mixture layer 12 can be applied in a thin film as shown in FIG. 9(a2).

[0123] Then, as shown in FIG. 9(a3), a first mixture layer 11 is formed by step B1 or step B2 so as to partially cover the second mixture layer 12 that has been formed into a thin film.

[0124] In this way, the second composite layer 12 formed in Example 1 can be formed as a thin film, which reduces the material cost of the second composite layer 12 and also suppresses the occurrence of cracks when the second composite layer 12 dries.

[0125] Comparative Example 1 9(b1) to 9(b3) are diagrams showing the steps of a method for producing the electrode sheet 10 of Comparative Example 1. FIG. In Comparative Example 1, as shown in FIG. 9(b1), the first composite layer 11 is applied to the metal foil 9 before the second composite layer 12. Then, as shown in FIG. 9(b2), the position (height h2) of the die coater 22 of the application device is higher by the height of the first composite layer 11 than the position (height h1) of Example 1 in FIG. 9(a1), that is, it is a position away from the metal foil 9. Therefore, as shown in FIG. 9(b3), the second composite layer 12 formed by Comparative Example 1 has a thicker film thickness than the second composite layer 12 formed by Example 1. Therefore, the material cost of the second composite layer 12 is high, and cracks 30 are likely to occur when the second composite layer 12 is dried.

[0126] Example 2 10(a) and 10(b) are schematic cross-sectional views of a lithium ion secondary battery according to Example 2 produced using the positive electrode of the present invention. The battery 150 of Example 2 shown in FIG. 10(a) uses a positive electrode 121 having a second mixture layer 12 containing the conductive material of the present invention. As shown in FIG. 10(a), when a foreign metal substance 32 is mixed into the second mixture layer 12 during the process, the foreign metal substance 32 is converted into a metal ion (M + When the metal ions reach the negative electrode, they undergo a reduction reaction on the surface of the negative electrode, which is at a reduction potential, and are then deposited as metal (M), as shown in Figure 10(b).

[0127] However, even if the deposited metal grows and penetrates the separator 120, when it reaches the second mixture layer 12, a current path is formed throughout the second mixture layer 12 via the conductive material in the second mixture layer 12. This allows for gentle discharge and prevents abnormal heat generation due to local short circuiting.

[0128] Comparative Example 2 10(c) is a schematic cross-sectional view of a lithium-ion secondary battery of Comparative Example 2 produced using a positive electrode without second mixture layer 12. When insulating layer 34 is provided instead of second mixture layer 12, the deposited metal grows and penetrates separator 120 to connect positive electrode 121 and negative electrode 126, causing a short circuit and resulting in self-discharge failure.

[0129] Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above-mentioned embodiments and examples. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0130] Below, examples of reference forms are given. 1. A current collector; a first mixture layer including at least a positive electrode active material provided on at least one surface of the current collector; a second mixture layer that is partially covered by the first mixture layer and is mainly composed of particles different from the positive electrode active material; The second mixture layer is provided on at least one end side of the first mixture layer in a boundary portion between a formation region where the first mixture layer is formed and a non-formation region where the first mixture layer is not formed, one end of the second mixture layer is located between the at least one surface of the current collector and a lower surface of the first mixture layer in a formed region of the first mixture layer, and the other end is located in the non-formed region; a conductive material dispersed in the first composite layer and the second composite layer; Positive electrode for lithium-ion secondary batteries. 2. The conductive material dispersed in the first mixture layer and the second mixture layer is of the same type; 1. A positive electrode for a lithium ion secondary battery according to claim 1. 3. The conductive material includes at least one carbon material selected from carbon nanotubes, carbon nanohorns, graphene, carbon nanobrushes, carbon black, acetylene black, and ketjen black; 1. A positive electrode for a lithium ion secondary battery according to 1. or 2. 4. The resistivity of the second mixture layer is in the range of 1 to 100 times the resistivity of the first mixture layer. 4. A positive electrode for a lithium ion secondary battery according to any one of 1. to 3. 5. The conductive material dispersed in the second mixture layer is Contains 0.1 parts by mass or more and 20.0 parts by mass or less, 5. A positive electrode for a lithium ion secondary battery according to any one of 1. to 4. 6. The second mixture layer further contains a dispersed binder, The amount of the binder contained in the second mixture layer is 0.5 parts by mass or more and 60 parts by mass or less with respect to the total amount of the second mixture layer; 6. A positive electrode for a lithium ion secondary battery according to any one of 1. to 5. 7. The maximum thickness of the second composite layer is less than the minimum thickness of the first composite layer; 6. A positive electrode for a lithium ion secondary battery according to any one of 1. to 5. 8. The average thickness of the second composite layer is 3 μm or more and 90% or less of the average thickness of the first composite layer. 8. A positive electrode for a lithium ion secondary battery according to any one of 1. to 7. 9. The density of the second composite layer is 0.5 g / cm 3 More than 3.0g / cm 3 In the range of 9. A positive electrode for a lithium ion secondary battery according to any one of 1. to 8. 10. The average particle size of the particles contained as a main component in the second mixture layer is in the range of 0.1 μm to 3.0 μm. 10. A positive electrode for a lithium ion secondary battery according to any one of 1. to 9. 11. The particles contained as a main component in the second mixture layer include one or more materials selected from alumina, silica, thermoplastic resin, ionizing radiation curable resin, thermosetting resin, and insulating ink. 11. A positive electrode for a lithium ion secondary battery according to any one of 1. to 10. 12. The binder contained in the second composite layer is the same type as the binder contained in the first composite layer, and the ratio of the binder contained in the second composite layer to the total amount of the second composite layer is greater than the ratio of the binder contained in the first composite layer to the total amount of the first composite layer. 12. A positive electrode for a lithium ion secondary battery according to any one of 6. to 11. 13. A first mixture layer containing at least a positive electrode active material on both sides or one side of a current collector which is a strip-shaped sheet wound around a roll; a second mixture layer that is partially covered by the first mixture layer and is mainly composed of particles different from the positive electrode active material; are formed continuously in the longitudinal direction of the sheet and in parallel with the longitudinal direction of the sheet, A positive electrode sheet for a lithium ion secondary battery, formed such that at least one end of the first mixture layer in the short length direction of the sheet covers a portion of the second mixture layer. 14. On one or both sides of a current collector, which is a strip-shaped sheet wound into a roll, In the longitudinal direction of the sheet, A first mixture layer including at least a positive electrode active material; a second mixture layer that is partially covered by the first mixture layer and is mainly composed of particles different from the positive electrode active material; Each is formed intermittently, The second mixture layer is provided on at least one end side of the first mixture layer in the longitudinal direction of the sheet, in a boundary portion between a formation region where the first mixture layer is formed and a non-formation region where the first mixture layer is not formed; A positive electrode sheet for a lithium ion secondary battery, wherein one end of the second composite layer is located between at least one surface of the current collector and the lower surface of the first composite layer in the formation region of the first composite layer, and the other end is located in the non-formation region. 15. A process (A1) of continuously applying a mixture containing any one of a conductive material (M) selected from a paste-like mixture (M1) containing at least conductive granular, fibrous or scaly solid matter and a dispersion medium, a conductive thermoplastic resin (M2), a conductive thermosetting resin (M3) and a conductive ink (M4) to both sides or a portion of one side of a current collector, which is a strip-shaped sheet wound on a roll, in the longitudinal direction of the sheet; A step (B1) of continuously applying a paste-like mixture (P) containing at least a positive electrode active material and a dispersion medium to the sheet in a longitudinal direction; (C) solidifying the formed product by drying; in at least this order, A method for producing a positive electrode sheet for a lithium ion secondary battery, comprising: in the step (B1), applying the mixture (P) so as to cover both a portion of the region where the mixture containing the conductive material (M) is applied in the step (A1) that includes one end in the short dimension of the sheet and a portion where the mixture containing the conductive material (M) is not applied, and preventing the mixture (P) from applying to a portion of the region where the mixture containing the conductive material (M) is applied that includes the other end in the short dimension of the sheet. 16. A process (A2) of intermittently applying a mixture containing any one of a conductive material (M) selected from a paste-like mixture (M1) containing at least conductive granular, fibrous or scaly solid matter and a dispersion medium, a conductive thermoplastic resin (M2), a conductive thermosetting resin (M3) and a conductive ink (M4) to both sides or a portion of one side of a current collector, which is a strip-shaped sheet wound on a roll, in the longitudinal direction of the sheet; A step (B2) of intermittently applying a paste-like mixture (P) containing at least a positive electrode active material and a dispersion medium to the sheet in a longitudinal direction; (C) solidifying the formed product by drying; in at least this order, A method for producing a positive electrode sheet for a lithium ion secondary battery, comprising: in the step (B2), applying the mixture (P) so as to cover both a portion of the region applied with the mixture containing the conductive material (M) in the step (A2) that includes one end in the longitudinal direction of the sheet and a portion of the region not applied with the mixture containing the conductive material (M), and preventing the mixture (P) from applying to a portion of the region applied with the mixture containing the conductive material (M) that includes the other end in the longitudinal direction of the sheet. 17. In the step (C), the mixture containing the conductive material (M) and the mixture (P) are solidified simultaneously. 15. A method for producing a positive electrode sheet for a lithium ion secondary battery according to 16. or 17. [Explanation of symbols]

[0131] 9 Metal foil 10 Electrode sheet 11 First composite layer 12 Second composite layer 15 Application area, forming area 16 areas 17 Non-coating area, non-forming area 19 Boundary 22 Die Coater 30 Crack 32 Metallic foreign bodies 34 Insulating layer 100 Computers 102 CPU 104 Memory 105 Storage 106 I / O 107 Communication I / F 109 Bus 110 Programs 120 Separator 121 Positive electrode 122 Cathode active material layer 123 Positive electrode current collector layer 124 Boundary 125 Negative electrode tab 126 Negative electrode 127 Negative electrode active material layer 128 Negative electrode current collector layer 129 Boundary 130 Positive electrode tab 131 Positive terminal 136 Negative terminal 140 Flexible Film 150 batteries

Claims

1. a first composite layer containing at least a positive electrode active material and a conductive material, and a second composite layer mainly composed of particles different from the positive electrode active material are continuously formed on both sides or one side of a current collector which is a strip-shaped sheet in a longitudinal direction of the sheet, At least one end of the first mixture layer in the short direction covers at least one end of the second mixture layer in the short direction; A surface of at least one end of the second mixture layer in the short length direction contains a conductive material, A positive electrode sheet for a lithium ion secondary battery, wherein the density of the second mixture layer is in the range of 0.5 g / cm 3 or more and 3.0 g / cm 3 or less.

2. A positive electrode for a lithium ion secondary battery, which is manufactured from the positive electrode sheet for a lithium ion secondary battery according to claim 1, The positive electrode sheet is formed by cutting out a region including the first mixture layer and the second mixture layer from the positive electrode sheet. Positive electrode for lithium-ion secondary batteries.

3. The positive electrode for a lithium ion secondary battery according to claim 2 is used. Lithium-ion secondary battery.

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