Conductive resin film for current collector of secondary battery and method for producing same

Abstract

To provide a low-cost conductive resin film for a collector of a secondary battery, along with a method of manufacturing the same, contributing to peeling prevention of the collector of the secondary battery, improvement in conductivity in a thickness direction, and reduction in weight, by improving chemical resistance, to prevent degradation in charge / discharge cycle characteristics.SOLUTION: A conductive resin film 4 for collector with a relative crystallinity of 80% or higher is formed of a forming material 1 containing 100 pts.mass of polyarylene ether ketone resin and 5 or more 35 or less pts.mass of a conductive material. The conductive material comprises 30 ore more and 99 or less mass% of a carbon nano-tube of, and 1 or more and 70 or less mass% of a conductive material other the carbon nano-tube in composition mass ratio. Since the polyarylene ether ketone resin with excellent chemical resistance and low water absorption rate is used to manufacture the conductive resin film 4 for collector, electrolyte components cannot penetrate into the conductive resin film 4 for collector, eliminating the possibility of charge / discharge cycle characteristics degradation.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a conductive resin film for a current collector of a secondary battery used in a lithium ion secondary battery, an all-solid-state battery, or the like, and a method for producing the same. [Background technology]

[0002] In recent years, high-performance rechargeable secondary batteries such as nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, lithium-ion secondary batteries, and all-solid-state batteries have been attracting attention. Among these high-performance secondary batteries, lithium-ion secondary batteries and all-solid-state batteries have been attracting particular attention. A lithium-ion secondary battery is composed of a positive electrode, a negative electrode, a separator, an electrolyte, a container, and other components (not shown). Of these components, the positive electrode (positive electrode plate) is composed of a current collector plate and a positive electrode mixture containing a positive electrode active material formed on the top of the current collector plate. In contrast, the negative electrode (negative electrode plate) is composed of a current collector plate and a negative electrode mixture formed on both sides of the current collector plate.

[0003] Such lithium-ion secondary batteries and all-solid-state batteries have excellent characteristics, such as high energy density, high operating voltage, long life cycle, and low self-discharge, and are therefore used in a wide range of fields, including as power sources for mobile information devices such as mobile phones, multi-function mobile phones, and tablet terminals, electronic devices such as cameras, video cameras, and portable digital music players, automobiles such as electric vehicles (EVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs), and aircraft.

[0004] Lithium-ion secondary batteries and all-solid-state batteries used in mobile information devices, automobiles, and the like are required to have high energy densities. One way to achieve this high energy density is to reduce the battery's weight. Various methods have been investigated to reduce the battery's weight, one of which is the use of conductive resin films. While metal foils are used as current collectors for the positive and negative electrodes of lithium-ion secondary batteries, the use of conductive resin films, which have a lower specific gravity than metals, instead of metal foils can contribute to reducing the battery's weight.

[0005] Therefore, various conductive resin films have been investigated in order to reduce the weight of secondary batteries (see Patent Documents 1, 2, and 3). For example, Patent Document 1 proposes a conductive resin film made of a cyclic olefin resin, a conductive filler, and a conjugated diene rubber, or a cyclic olefin resin, a hydrogenated product of an aromatic vinyl-conjugated diene block copolymer, a conductive filler, and a conjugated diene rubber.

[0006] Patent Document 2 proposes a current collector for a secondary battery having a conductive resin layer containing at least one resin selected from the group consisting of polyether ether ketone and a tetrafluoroethylene-hexafluoropropylene copolymer, and at least one conductive filler selected from the group consisting of ketjen black and multi-walled carbon nanotubes. Patent Document 3 discloses a current collector for a bipolar lithium-ion secondary battery, which comprises a conductive resin layer (first conductive layer) formed by adding a conductive filler to a substrate containing an imide group-containing resin, and a conductive resin layer (second conductive layer) formed by adding a conductive filler to a substrate containing a non-imide group-containing resin, and a metal layer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-77236 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-248430 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-26192 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the conductive resin film described in Patent Document 1 has a problem with chemical resistance, and therefore, when such a conductive resin film is used as a current collector of a lithium-ion secondary battery, electrolyte components may penetrate into the conductive resin film, resulting in a deterioration in charge-discharge cycle characteristics.

[0009] In addition, in the case of the current collector for secondary batteries in Patent Document 2, ketjen black and multi-walled carbon nanotubes are used as conductive filler components, but when ketjen black is used as the conductive filler component, it is difficult to add a large amount of ketjen black to the resin, making it difficult to achieve high conductivity for the current collector for secondary batteries. Furthermore, current collector plates containing ketjen black are brittle and may be damaged during application of positive or negative electrode active material or during assembly into a secondary battery.

[0010] Furthermore, conductive resin layers manufactured from a raw material mixture using multi-walled carbon nanotubes as a conductive filler have the problem that, although the multi-walled carbon nanotubes are oriented in the plane direction, they have excellent in-plane conductivity, but poor conductivity in the thickness direction. Furthermore, when tetrafluoroethylene-hexafluoropropylene copolymer is used as the resin component, the specific gravity of the resin becomes high, at 2.1 or more and 2.2 or less, which poses a major problem of not contributing to weight reduction of the current collector. Furthermore, because tetrafluoroethylene-hexafluoropropylene copolymer is a fluororesin, special steel materials and equipment are required for melt molding, resulting in increased costs for the current collector.

[0011] Furthermore, in the case of the current collector for a bipolar lithium-ion secondary battery described in Patent Document 3, the multilayer structure is made up of two different resins, and because the two resins have different linear expansion coefficients, the difference in the expansion rate of the conductive resins caused by heat generation during repeated charging and discharging may lead to peeling of the current collector between the first and second conductive layers. Furthermore, because the resins used in the first and second conductive layers have different water absorption rates, this current collector may curl due to the difference in expansion rate caused by water absorption after production, or may cause peeling between the first and second conductive layers.

[0012] The present invention has been made in view of the above, and aims to provide an inexpensive conductive resin film for a current collector of a secondary battery, which can improve chemical resistance to prevent a decrease in charge / discharge cycle characteristics, prevent peeling of the current collector of the secondary battery, improve conductivity in the thickness direction, and contribute to weight reduction, and a method for producing the same. [Means for solving the problem]

[0013] As a result of extensive research, the present inventors focused on a mixture of polyarylene ether ketone resin, which has the highest heat resistance of all thermoplastic resins and also excels in chemical resistance and mechanical properties, with lightweight carbon nanotubes, which have the highest conductivity of all conductive materials, and a conductive material other than carbon nanotubes. They discovered that when a conductive resin film is molded from a molding material containing carbon nanotubes, the carbon nanotubes are oriented in the extrusion direction, making it impossible to obtain good conductivity in the thickness direction of the resin film. However, they discovered that adding a conductive material other than carbon nanotubes can improve conductivity in the thickness direction, thereby completing the present invention.

[0014] That is, in order to solve the above-mentioned problems, the present invention provides a conductive resin film for a current collector having a relative crystallinity of 80% or more, which is formed from a molding material containing 100 parts by mass of a polyarylene ether ketone resin and 5 parts by mass or more and 35 parts by mass or less of a conductive material, the conductive material is composed of, in terms of composition mass ratio, 30% by mass or more and 99% by mass or less of carbon nanotubes and 1% by mass or more and 70% by mass or less of conductive material other than carbon nanotubes; The conductive material other than carbon nanotubes is a metal-based or carbon-based conductive material, has a shape of either a polyhedron, a sphere, or an ellipsoid, and has an average particle diameter of 0.1 μm or more and 10.0 μm or less; The resistance value when measured by applying a pressure of 1 MPa in the thickness direction of the conductive resin film for current collector is 1 mΩ cm 2 End 800mΩ·cm 2 It is characterized by the following:

[0015] In addition, the thickness is 10 μm or more and 500 μm or less, and the specific gravity measured in accordance with JIS K 7112 A method is 1.25 or more and 1.60 Hereafter, N-methyl-2-pyrrolidone When immersed in an electrolyte, the mass change rate is 2.0%. It would be better if it was below.

[0016] In addition, the thickness is 25 μm or more and 353 μm or less, the specific gravity when measured in accordance with JIS K 7112 Method A is 1.33 or more and 1.38 or less, and the resistance when measured by applying a pressure of 1 MPa in the thickness direction of the conductive resin film for the current collector is 97 mΩ cm 2 More than 732 mΩ cm 2 Hereinafter, the mass change rate when immersed in N-methyl-2-pyrrolidone and an electrolyte solution can be set to 0.0% or more and 2.0% or less.

[0017] The polyarylene ether ketone resin is preferably at least one of a polyether ether ketone resin and a polyether ketone ketone resin.

[0018] In order to solve the above problems, the present invention provides a method for producing a conductive resin film for a current collector of a secondary battery according to claim 1 or 2, comprising the steps of: A molding material containing 100 parts by mass of polyarylene ether ketone resin and 5 parts by mass or more and 35 parts by mass or less of a conductive material, the conductive material being composed of, in terms of composition mass ratio, 30% by mass or more and 99% by mass or less of carbon nanotubes and 1% by mass or more and 70% by mass or less of a conductive material other than carbon nanotubes, is melted and kneaded; The molding material is extruded through a die into a conductive resin film for a current collector, and then cooled by sandwiching it between a pressure roll and a cooling roll, thereby achieving a relative crystallinity of 80% or more in the conductive resin film for a current collector.

[0019] The cooled conductive resin film for a current collector is subjected to heat compression molding, and the heating temperature of the conductive resin film for a current collector is set to be equal to or higher than the melting point of the polyarylene ether ketone resin but lower than the thermal decomposition temperature, and the pressure applied to the conductive resin film for a current collector is set to be 0.5 kgf / cm with respect to the projected area of ​​the conductive resin film for a current collector. 2 More than 100kgf / cm 2 It is preferable to do the following:

[0020] The molding material in the claims can be prepared by melt-kneading a polyarylene ether ketone resin and a conductive material comprising a mixture of carbon nanotubes and a conductive material other than carbon nanotubes. The molding material and the polyarylene ether ketone resin can be melt-kneaded at a temperature equal to or higher than the melting point of the polyarylene ether ketone resin and lower than the thermal decomposition temperature of the polyarylene ether ketone resin. Furthermore, to utilize the properties of carbon nanotubes, a mixture of multiple types with different outer diameters and lengths may be used.

[0021] The conductive resin film for a current collector may be any of a uniaxially stretched type, a biaxially stretched type, and a non-stretched type. This conductive resin film for a current collector includes not only a thin conductive resin film for a current collector but also a thick conductive resin sheet for a current collector. Furthermore, the secondary battery according to the present invention includes at least a nickel-cadmium storage battery, a nickel-metal hydride storage battery, a nickel-zinc storage battery, a lithium ion secondary battery, a bipolar lithium ion secondary battery, an all-solid-state battery, and the like.

[0022] According to the present invention, a conductive resin film for a current collector is produced using a polyarylene ether ketone resin as a molding material, which has excellent mechanical strength, light weight, chemical resistance, and the like, and has low water absorption. Therefore, even if the conductive resin film for a current collector is used as a current collector, there is little penetration of electrolyte components into the conductive resin film for a current collector, and the risk of deterioration in charge-discharge cycle characteristics can be eliminated. Furthermore, since a conductive material other than carbon nanotubes is used as a molding material in addition to carbon nanotubes, the conductivity of the conductive resin film for a current collector in the thickness direction is improved. [Effects of the Invention]

[0023] According to the present invention, it is possible to improve the chemical resistance of a conductive resin film for a current collector and prevent a decrease in charge-discharge cycle characteristics. Furthermore, it is possible to prevent peeling of a current collector of a secondary battery, improve conductivity in the thickness direction, and contribute to weight reduction, and it is possible to provide a conductive resin film for a current collector at low cost. Furthermore, since the conductive material other than carbon nanotubes has a polyhedral, spherical, or ellipsoidal shape, it is expected that conductivity in the thickness direction will be improved. Furthermore, since the particle diameter of the conductive material other than carbon nanotubes is 0.1 μm or more and 10.0 μm or less on an average particle diameter, poor dispersion is not caused, uniform conductivity in the thickness direction can be obtained, and a thin conductive resin film for current collector can be obtained. In addition, it is possible to prevent a decrease in mechanical strength, which would cause breakage, cracking, or holes in the conductive resin film for current collector. Furthermore, when a pressure of 1 MPa is applied in the thickness direction of the conductive resin film for current collector, the resistance value is 1 mΩ·cm. 2 End 800mΩ·cm 2 Since the thickness is less than 100 μm, it is possible to suppress a decrease in energy density and prevent the conductive resin film for current collector from becoming brittle.

[0024] According to the invention of claim 2, the thickness of the conductive resin film for a current collector is 10 μm or more and 500 μm or less, which prevents a significant decrease in the tensile strength of the conductive resin film for a current collector and does not hinder weight reduction when the conductive resin film for a current collector is used as a current collector for a secondary battery. Furthermore, the specific gravity of the conductive resin film for a current collector, measured in accordance with JIS K 7112 Method A, is 1.25 or more and 1.60 or less, which eliminates the risk of voids or cracks occurring in the conductive resin film for a current collector and contributes to weight reduction.

[0025] Also, The mass change rate when immersed in N-methyl-2-pyrrolidone and an electrolyte is 2.0% or less, making it possible to obtain excellent chemical resistance.

[0026] According to the invention of claim 3, the polyarylene ether ketone resin is at least one of a polyether ether ketone resin and a polyether ketone ketone resin, and therefore excellent mechanical strength, light weight, hydrolysis resistance, heat resistance, chemical resistance, etc. can be obtained, and it is also possible to improve availability, reduce production costs, and formability of the conductive resin film for current collector.

[0027] According to the invention of claim 4, the conductive resin film for current collector is manufactured by melt extrusion molding, which improves the thickness accuracy, productivity, and handleability of the conductive resin film for current collector, and is expected to simplify manufacturing equipment. Furthermore, since no special steel materials or equipment are required to mold the conductive resin film for current collector, it is expected that the manufacturing costs of the current collector will be reduced.

[0028] According to the invention of claim 5, the conductive resin film for a current collector is subjected to heat compression molding, which reduces the resistance value of the conductive resin film for a current collector, improves the conductivity, and reduces the amount of conductive material used, thereby reducing costs. [Brief explanation of the drawings]

[0029] [Figure 1]FIG. 1 is an explanatory view schematically showing a melt kneader in an embodiment of the method for producing a conductive resin film for a current collector of a secondary battery according to the present invention. [Figure 2] 1 is an explanatory view schematically illustrating a manufacturing apparatus in an embodiment of a conductive resin film for a current collector of a secondary battery and a manufacturing method thereof according to the present invention. [Figure 3] 1A and 1B are cross-sectional explanatory views schematically illustrating measurement states of the conductivity of conductive resin films for current collectors in examples and comparative examples of the method for producing a conductive resin film for current collectors of secondary batteries according to the present invention. [Figure 4] FIG. 2 is a partial plan view illustrating a schematic diagram of the measurement state of the conductivity of a conductive resin film for a current collector in an example and a comparative example of the method for producing a conductive resin film for a current collector of a secondary battery according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] A preferred embodiment of the present invention will now be described with reference to the drawings. In this embodiment, a conductive resin film 4 for a current collector of a secondary battery is formed into a conductive resin film having a relative crystallinity of 80% or more using a molding material 1 containing a polyarylene ether ketone resin 2 and a conductive material 3, as shown in Figures 1 to 4. The conductive material 3 is composed of carbon nanotubes that contribute to conductivity in the planar direction and a conductive material other than carbon nanotubes that contributes to conductivity in the thickness direction, thereby contributing to the achievement of Goal 9 of the SDGs (the United Nations' international goals for sustainable development, consisting of 17 global goals and 169 targets (achievement criteria)) adopted at the United Nations Summit.

[0031] Molding material 1 is prepared by adding 5 to 35 parts by mass, preferably 8 to 30 parts by mass, and more preferably 10 to 25 parts by mass of conductive material 3 to 100 parts by mass of polyarylene ether ketone resin. This is because, when the amount of conductive material 3 added is less than 5 parts by mass, the resistance value measured by applying a pressure of 1 MPa in the thickness direction of conductive resin film 4 for current collector is 1000 mΩ cm. 2Since the conductivity below this level cannot be obtained, sufficient conductivity cannot be imparted to the conductive resin film 4 for current collector, making it difficult to use it as a current collector for a secondary battery.

[0032] On the other hand, if the amount of conductive material 3 added exceeds 35 parts by mass, the melt viscosity of molding material 1 increases, resulting in a decrease in melt fluidity, and the processability of conductive resin film 4 for current collector decreases due to a decrease in melt elongation, resulting in the formation of holes. In addition, it becomes difficult to blend conductive material 3 into polyarylene ether ketone resin 2. Furthermore, if the amount of conductive material 3 added exceeds 35 parts by mass, conductive material 3 separates from conductive resin film 4 for current collector, causing the generation of resin buildup and resulting in a decrease in the quality of conductive resin film 4 for current collector.

[0033] To explain this point in more detail, when the conductive resin film 4 for a current collector is molded into a film, a large amount of deposits called "pitting resin" may adhere and accumulate at the exit (also called the die lip) of the molding die 23 shown in Fig. 2. When such pitting resin accumulates, die lines may appear in the conductive resin film 4 for a current collector, or the pitting resin may leave the die exit and become mixed into the conductive resin film 4 for a current collector, resulting in a deterioration in the quality of the conductive resin film 4 for a current collector.

[0034] The conductive material 3 is prepared as a mixture of carbon nanotubes and a conductive material other than the carbon nanotubes, and the conductive material other than the carbon nanotubes functions to improve the conductivity in the thickness direction of the conductive resin film for a current collector 4. The composition mass ratio of the carbon nanotubes and the material other than the carbon nanotubes is 30% by mass to 99% by mass of the carbon nanotubes and 1% by mass to 70% by mass of the conductive material other than the carbon nanotubes, preferably 40% by mass to 95% by mass of the carbon nanotubes, more preferably 50% by mass to 90% by mass, and even more preferably 60% by mass to 80% by mass of the carbon nanotubes. This composition mass range allows for high conductivity in the thickness direction of the conductive resin film for a current collector 4 without reducing the chemical resistance of the conductive resin film for a current collector 4.

[0035] The composition weight ratio of carbon nanotubes is 30% by mass or more because if it is less than 30% by mass, sufficient conductivity cannot be imparted to the conductive resin film 4 for current collector, making it difficult to use it as a current collector for a secondary battery. On the other hand, the composition weight ratio of carbon nanotubes is 99% by mass or less because if it exceeds 99% by mass, the carbon nanotubes will be oriented in the extrusion direction, and the resistance value measured by applying a pressure of 1 MPa in the thickness direction will be 1000 mΩ cm. 2 If the temperature exceeds this range, the conductive resin film 4 for current collector cannot be given sufficient conductivity, making it difficult to use it as a current collector for a secondary battery.

[0036] In addition to the polyarylene ether ketone resin 2 and the conductive material 3, such molding material 1 may include, within the range that does not impair the characteristics of the present invention, polyolefin resins such as polyethylene (PE) resin, polypropylene (PP) resin, polymethylpentene (PMP) resin, and polystyrene (PS) resin, acid-modified olefin resins such as maleic anhydride-modified polypropylene, polyester resins such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, and polyethylene naphthalate (PEN) resin, and polyolefin resins such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, and polyolefin resins such as polyethylene terephthalate (PEN) resin, and polyolefin resins such as polyethylene terephthalate (PET) resin, polypropylene terephthalate (PP) resin, and polyolefin resins such as polyethylene terephthalate (PET) resin, polypropylene naphthalate (PEN ... Polyimide resins such as polyimide (PI) resin, polyamideimide (PAI) resin, polyetherimide (PEI) resin, polyamide 4T (PA4T) resin, polyamide 6T (PA6T) resin, modified polyamide 6T (modified PA6T) resin, polyamide 9T (PA9T) resin, polyamide 10T (PA10T) resin, polyamide 11T (PA11T) resin, polyamide 6 (PA6) resin, polyamide 66 (PA66) resin, polyamide 46 (PA46) resin, polyamide resins such as polysulfone (PSU) resin, poly Polysulfone resins such as ether sulfone (PES) resin and polyphenylene sulfone (PPSU) resin; polyarylene sulfide resins such as polyphenylene sulfide (PPS) resin, polyphenylene sulfide ketone resin, polyphenylene sulfide sulfone resin, and polyphenylene sulfide ketone sulfone resin; fluororesins such as polytetrafluoroethylene (PTFE) resin, polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin, tetrafluoroethylene-hexafluoropropyl copolymer (FEP) resin, tetrafluoroethylene-ethylene copolymer (ETFE) resin, polychlorotrifluoroethylene (PCTFE) resin, polyvinylidene fluoride (PVdF) resin, and vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer resin; and thermoplastic resins such as polycarbonate (PC) resin, polyarylate (PAR) resin, polyacetal (POM) resin, liquid crystal polymer (LCP), and aliphatic polyketone resin can be selectively added.

[0037] In addition to the polyarylene ether ketone resin 2, the conductive material 3, and the thermoplastic resin, certain additives can be selectively added to the molding material 1, provided that the properties of the present invention are not impaired. Specifically, nucleating agents, impact modifiers, antioxidants, light stabilizers, ultraviolet absorbers, plasticizers, lubricants, flame retardants, heat resistance improvers, inorganic fillers, organic fillers, glass fibers, carbon fibers, nanofibers, etc. can be selectively added.

[0038] The polyarylene ether ketone resin 2 of the molding material 1 is a crystalline thermoplastic resin consisting of arylene groups, ether groups, and carbonyl groups, and examples thereof include the resins described in Japanese Patent No. 5709878 and Japanese Patent No. 5847522, or in the literature [Asahi Research Center Co., Ltd.: PEEK, a super engineering plastic growing in cutting-edge applications (Part 1)], and is characterized by excellent mechanical strength, light weight, low dielectric properties, hydrolysis resistance, heat resistance, chemical resistance, etc.

[0039] Specific examples of the polyarylene ether ketone resin 2 include, for example, polyether ether ketone (PEEK) resin having a chemical structure represented by chemical formula (1), polyether ketone (PEK) resin having a chemical structure represented by chemical formula (2), polyether ketone ketone (PEKK) resin having a chemical structure represented by chemical formula (3), polyether ether ketone ketone (PEEKK) resin having a chemical structure represented by chemical formula (4), and polyether ketone ether ketone ketone (PEKEKK) resin having a chemical structure represented by chemical formula (5).

[0040] [ka]

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] Among these polyarylene ether ketone resins 2, at least one of polyether ether ketone resins and polyether ketone ketone resins is preferred from the viewpoints of easy availability, cost, and formability of the conductive resin film 4 for current collector. Specific examples of polyether ether ketone resins include Victrex Powder series and Victrex Granules series manufactured by Victrex, Vestakeep series manufactured by Diesel-Evonik, and KetaSpire PEEK series manufactured by Solvay Specialty Polymers. Specific examples of polyether ketone ketone resins include KEPSTAN series manufactured by Arkema.

[0046] The polyarylene ether ketone resin 2 may be used alone or in combination of two or more. The polyarylene ether ketone resin 2 may also be a copolymer having two or more chemical structures represented by chemical formulas (1) to (5). The polyarylene ether ketone resin 2 is usually used in a form suitable for molding, such as powder, granules, or pellets. The method for producing the polyarylene ether ketone resin 2 is not particularly limited, but examples thereof include the method described in the literature [Asahi Research Center Co., Ltd.: PEEK, a super engineering plastic growing in cutting-edge applications (Vol. 1)].

[0047] The apparent shear viscosity of polyarylene ether ketone resin 2 at 375°C, measured with a flow tester using a die with a diameter of 1.0 mm and a length of 10 mm under the conditions of a temperature of 375°C and a load of 50 kgf, was set to 1 x 10 from the viewpoint of improving moldability. 1Pa·s or more 1×10 4 Pa·s or less, preferably 5×10 1 Pa·s or more 5×10 3 Pa·s or less, preferably 1×10 2 Pa·s or more 2×10 3 Pa·s or less is good. This is 1×10 1 If the viscosity is less than Pa·s, the apparent shear viscosity will be low, which will lead to a decrease in melt tension and make it difficult to mold the molding material 1. Therefore, care must be taken. Also, if the apparent shear viscosity is less than 1×10 4 If the viscosity exceeds Pa·s, care must be taken as the melt viscosity will increase and the melt elongation will decrease, making it difficult to mold the molding material 1.

[0048] The carbon nanotubes in the molding material 1 are configured in a cylindrical hollow fiber structure and function to improve the conductivity in the plane direction of the conductive resin film 4 for the current collector and contribute to weight reduction. These carbon nanotubes come in two varieties: single-walled carbon nanotubes, which have a structure in which one surface of graphite is wrapped around it, and multi-walled carbon nanotubes, which have two or more layers wrapped around them. To make the most of their properties, multiple types of carbon nanotubes with different outer diameters and lengths can be mixed and used.

[0049] Carbon nanotubes other than these single-walled carbon nanotubes and multi-walled carbon nanotubes include nanografibers, bamboo-shaped nanotubes, and cup-stacked nanotubes, as described in Non-Patent Document 1 [Introduction to the Materials Chemistry of Carbon Nanotubes, Corona Publishing, edited by Yahachi Saito, pp. 7-9]. Also included are analogues of carbon nanotubes, such as nanohorns, nanocones, microcoils, and nanocoils, as described in Non-Patent Document 1 [Introduction to the Materials Chemistry of Carbon Nanotubes, Corona Publishing, edited by Yahachi Saito, pp. 9-11]. Among these carbon nanotubes and analogues, multi-walled carbon nanotubes are the most suitable from the viewpoint of cost.

[0050] The fiber diameter (outer diameter) of the carbon nanotubes is not particularly limited, but is preferably 0.5 nm or more and 200 nm or less. Such carbon nanotubes can be produced by known production methods. For example, they can be produced by (1) the arc discharge method, (2) the laser evaporation method, or (3) a chemical vapor deposition method (or pyrolysis method) such as the substrate growth method, supported catalyst method, fluidized catalyst method, or HiPco method, as described in Non-Patent Document 1 [Introduction to Materials Chemistry of Carbon Nanotubes, Corona Publishing, edited by Saito Yahachi, pp. 11-12]. They can also be produced by the eDPIS method, the Supergloss method, or the like.

[0051] Specific examples of carbon nanotubes include Supergrowth CNT (manufactured by the New Energy and Industrial Technology Development Organization), eDIPS-CNT (manufactured by the New Energy and Industrial Technology Development Organization), SWNT series (manufactured by Meijo Nanocarbon Co., Ltd.: product name), VGCF series (manufactured by Showa Denko K.K.: product name), FloTube series (manufactured by CNano Technology: product name), AMC (manufactured by Ube Industries, Ltd.: product name), Nanocyl NC7000 series (manufactured by Nanocyl: product name), Baytubes (manufactured by BAYER: product name), GRAPHISTRENGTH (manufactured by Arkema: product name), MWNT7 (manufactured by Hodogaya Chemical Co., Ltd.: product name), K-Nanos series (manufactured by Kumho), and Hyperion CNT (manufactured by Hypeprion Catalysis International: product name).

[0052] The conductive material other than the carbon nanotubes in the molding material 1 is made of a metallic or carbon-based conductive material, and functions to improve the conductivity in the thickness direction of the conductive resin film for current collector 4. Examples of metallic conductive materials include gold, silver, copper, nickel, iron, aluminum, chromium, niobium, titanium, tin, vanadium, and alloys containing two or more of these, metal oxides, metal carbides, metal nitrides, etc.

[0053] Examples of carbon-based conductive materials include carbon blacks such as furnace black (oil furnace black and gas furnace black), channel black, acetylene black, and thermal black; carbon fibers such as carbon nanofibers, fullerenes, amorphous carbon, bread-based carbon fibers, and pitch-based carbon fibers; and graphite such as flake graphite, lump graphite, earthy graphite, expanded graphite obtained by chemically treating flake graphite with concentrated sulfuric acid or the like and then heating it, expanded graphite obtained by heat-treating expanded graphite at high temperatures, and artificial graphite.

[0054] The shape of the conductive material other than carbon nanotubes may be any shape, such as plate-like, scale-like, polyhedral, spherical, or ellipsoidal, but polyhedral, spherical, or ellipsoidal shapes are preferred because they can improve conductivity in the thickness direction. Powder, granular, lumpy, fibrous, or other shapes are also not particularly important. One type may be used alone, or two or more types may be used in combination.

[0055] The particle size of the conductive material other than carbon nanotubes should be an average particle size of 0.1 μm to 10.0 μm, preferably 0.5 μm to 8.0 μm, and more preferably 1.0 μm to 8.0 μm. This is because an average particle size of less than 0.1 μm results in severe secondary aggregation of the conductive material, leading to poor dispersion and making it difficult to achieve uniform conductivity through the thickness. Furthermore, the melt viscosity of the molding material 1 increases, making it difficult to obtain a thin conductive resin film 4 for a current collector. On the other hand, an average particle size of the conductive material exceeding 10.0 μm results in the generation of resin buildup and a decrease in mechanical strength, leading to breakage, cracking, and perforations in the conductive resin film 4 for a current collector, making it difficult to manufacture the conductive resin film 4 for a current collector.

[0056] Furthermore, the conductive material 3 may contain, within a range that does not impair the properties of the conductive resin film 4 for current collector, for example, a silane coupling agent [vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-aminopropylethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, tris-(trimethoxysilylpropyl)isocyanurate, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-isocyanatepropyltriethoxysilane, 3-trimethoxysilylpropylsuccinic anhydride, imidazole silane, etc.], a titanate coupling agent [isopropyl triisostearoyl titanate, isopropyl(dioctyl)silane, etc.], a silane ... Bis(dioctyl pyrophosphate) titanate, isopropyl tris(N-aminoethyl-aminoethyl) titanate, tetraoctyl bis(di-tridecyl phosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl) bis(di-tridecyl) phosphite titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, bis(dioctyl pyrophosphate) ethylene titanate, isopropyl trioctanoyl titanate, isopropyl di The coating may be treated with various coupling agents such as methacrylic isostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctylphosphate) titanate, isopropyl tricumylphenyl titanate, tetraisopropyl(dioctylphosphite) titanate, and aluminate coupling agents such as acetoalkoxyaluminum diisopropylate.

[0057] The apparent shear viscosity of molding material 1 was measured with a flow tester using a die with a diameter of 1.0 mm and a length of 10 mm under the conditions of a temperature of 375°C and a load of 50 kgf. The apparent shear viscosity at a temperature of 375°C was 1 x 10 1Pa·s or more 1×10 4 Pa·s or less, preferably 1×10 2 Pa·s or more 5×10 3 Pa·s or less, preferably 5×10 2 Pa·s or more 2×10 3 The range of Pa·s or less is preferable. This means that the apparent shear viscosity is 1×10 1 Pa·s or more 1×10 4 If the viscosity is within the range of Pa·s or less, the conductive resin film 4 for current collector has excellent formability and can be expected to have sufficient mechanical strength.

[0058] In contrast, the apparent shear viscosity is 1×10 1 If the apparent shear viscosity is less than Pa·s, the apparent shear viscosity is low, which leads to a decrease in melt tension and makes it difficult to form the conductive resin film 4 for a current collector. 4 If the viscosity exceeds Pa·s, the melt viscosity will be high and the melt elongation will be reduced, which may cause holes to form in the conductive resin film 4 for a current collector and cause it to break, which will result in problems with molding the conductive resin film 4 for a current collector.

[0059] In the above, when producing the conductive resin film 4 for a current collector, the polyarylene ether ketone resin 2, the conductive material 3, which is carbon nanotubes, and a conductive material other than carbon nanotubes are melt-kneaded for a predetermined time to prepare a molding material 1, and this molding material 1 is fed into a melt extrusion molding machine 20 for molding resin films and melt-extruded to produce a conductive resin film 4 for a current collector having a thickness of 500 μm or less, for example, 10 μm or more and 500 μm or less.

[0060] Methods for preparing the molding material 1 include: (1) a method in which carbon nanotubes and a conductive material other than carbon nanotubes are simultaneously or separately added to a melt mixer 10 for the molding material, and melt-kneaded with the molten polyarylene ether ketone resin 2 to prepare the molding material 1; and (2) a method in which polyarylene ether ketone resin 2, carbon nanotubes, and a conductive material other than carbon nanotubes are stirred and mixed at room temperature (a temperature of approximately 0°C to 50°C) using a stirring mixer, and then melt-kneaded in the melt mixer 10 to prepare the molding material 1.

[0061] 1 is prepared, and after adding polyarylene ether ketone resin 2 to this melt kneader 10, a stirred mixture of carbon nanotubes and a conductive material other than the carbon nanotubes is newly added by a side feeder method or the like, and melt-kneaded with the already melted polyarylene ether ketone resin 2 to prepare molding material 1. Alternatively, for example, after adding polyarylene ether ketone resin 2 to melt kneader 10, carbon nanotubes and a conductive material other than the carbon nanotubes are newly added to melt kneader 10 by a third feeder method or the like, and melt-kneaded with the already melted polyarylene ether ketone resin 2 to prepare molding material 1.

[0062] Examples of the melt kneader 10 include a Banbury mixer, a mixing roll, a pressure kneader, a single-screw extruder, or a multi-screw extruder consisting of a twin-screw extruder, a triple-screw extruder, a four-screw extruder, or an eight-screw extruder. Among these, a vent-type multi-screw extruder is preferred, as it is expected to achieve good kneading and dispersion of the polyarylene ether ketone resin 2, the carbon nanotubes, and the conductive material other than the carbon nanotubes, and is capable of degassing the moisture and volatile gases generated therefrom.

[0063] 1, melt kneader 10, which is a multi-screw extruder, is configured to include cylinder 12 mounted on base 11, screw 13 built into cylinder 12 and axially supported therein, which is rotated by a motor to melt-knead polyarylene ether ketone resin 2, carbon nanotubes, and conductive materials other than the carbon nanotubes, and extrudes strands (rod-shaped) or the like from die 14 at the tip, inlet 15 for polyarylene ether ketone resin 2 connected to the upstream side of cylinder 12, side feeder 16 connected to the downstream side of cylinder 12 for feeding carbon nanotubes and conductive materials other than the carbon nanotubes, and rotatable cutter 17 for cutting the strands extruded from die 14 of cylinder 12 and cooled by air or water to obtain molding material 1. Side feeders 16 may be used singularly or plurally depending on the method for feeding carbon nanotubes and conductive materials other than the carbon nanotubes.

[0064] The inlet 15 and side feeder 16 of the melt kneader 10 are such that the inlet 15 is installed as a hopper on the upper upstream side of the cylinder 12, and the side feeder 16 has a screw structure and is mounted on the upper downstream side of the cylinder 12. By simultaneously or separately feeding fine powdered carbon nanotubes and conductive materials other than the carbon nanotubes from the side into the side feeder 16, which is located downstream of the inlet 15, the carbon nanotubes and conductive materials other than the carbon nanotubes are injected into the molten polyarylene ether ketone resin 2, improving the uniform dispersion of the molding material 1. Furthermore, since the kneading time of the carbon nanotubes and the conductive materials other than the carbon nanotubes in the polyarylene ether ketone resin 2 is shortened, decomposition can also be prevented.

[0065] The melting temperature when melt-kneading the polyarylene ether ketone resin 2 with the carbon nanotubes and the conductive material 3 other than the carbon nanotubes is not particularly limited as long as it is a temperature at which the melt-kneading dispersion is possible and the polyarylene ether ketone resin 2 does not decompose, but is in the range of not less than the melting point of the polyarylene ether ketone resin 2 and not more than the thermal decomposition temperature of the polyarylene ether ketone resin 2.

[0066] Specifically, the range is from the melting point of polyarylene ether ketone resin 2 +10°C to the melting point of polyarylene ether ketone resin 2 +100°C, preferably from the melting point of polyarylene ether ketone resin 2 +20°C to the melting point of polyarylene ether ketone resin 2 +80°C, more preferably from the melting point of polyarylene ether ketone resin 2 +30°C to the melting point of polyarylene ether ketone resin 2 +60°C, and even more preferably from the melting point of polyarylene ether ketone +30°C to the melting point of polyarylene ether ketone resin 2 +50°C.

[0067] This is because, if the temperature is lower than the melting point of the polyarylene ether ketone resin 2, it is not possible to melt-knead and disperse the polyarylene ether ketone resin 2, the carbon nanotubes, and the conductive material other than the carbon nanotubes 3. Conversely, if the temperature is higher than the thermal decomposition temperature, it is not preferable because it will lead to decomposition of the polyarylene ether ketone resin 2.

[0068] The melt-kneaded polyarylene ether ketone resin 2, carbon nanotubes, and conductive materials other than carbon nanotubes are extruded as strands through a die 14 to prepare molding material 1, but after being extruded as a conductive resin film through the die 14, the molding material 1 may be prepared in the form of powder, granules, flakes, or pellets. When preparing molding material 1, a predetermined amount or more of polyarylene ether ketone resin 2, carbon nanotubes, and conductive materials other than carbon nanotubes may be dispersed to form a masterbatch.

[0069] Next, the preparation method (2) will be described in detail. When this method involves stirring and mixing polyarylene ether ketone resin 2 with carbon nanotubes and a conductive material other than the carbon nanotubes 3 at room temperature, a stirring mixer such as a tumbler mixer, a Henschel mixer, a V-type mixer, a Nauta mixer, a ribbon blender, or a universal stirring mixer is used. In this case, the polyarylene ether ketone resin 2 is preferably in the form of a powder that allows for more uniform dispersion of the carbon nanotubes and the conductive material other than the carbon nanotubes. Examples of methods for pulverizing into a powder include shear pulverization, impact pulverization, collision pulverization, freeze pulverization, and solution pulverization.

[0070] The polyarylene ether ketone resin 2, the carbon nanotubes, and the conductive material other than the carbon nanotubes are stirred and mixed, and then melt-kneaded and dispersed in a melt kneader 10 such as a Banbury mixer, a mixing roll, a pressure kneader, a single-screw extruder or a multi-screw extruder consisting of a twin-screw extruder, a triple-screw extruder, a four-screw extruder, or an eight-screw extruder, to prepare a molding material 1.

[0071] The melt kneader 10 is preferably a vent-type multi-screw extruder that can be expected to achieve good kneading and dispersion of the polyarylene ether ketone resin 2, the carbon nanotubes, and the conductive material other than the carbon nanotubes, and that can degas the moisture and volatile gases generated therefrom. When preparing the molding material 1 using this melt kneader 10, a predetermined amount or more of the polyarylene ether ketone resin 2, the carbon nanotubes, and the conductive material other than the carbon nanotubes 3 can be dispersed to form a masterbatch.

[0072] The moisture content (water content) of the molding material 1 before melt extrusion molding is adjusted by heat drying to 2000 ppm or less, preferably 1000 ppm or less, and more preferably 500 ppm or less. This is because a moisture content exceeding 2000 ppm may cause foaming of the conductive resin film for current collector 4. Therefore, the molding material 1 is preferably heat dried to reduce the moisture content before melt kneading.

[0073] Examples of heat-drying methods for molding material 1 include known methods such as hot air circulation drying, dehumidified hot air drying, heated vacuum drying, and microwave drying. The heat-drying temperature for molding material 1 is between −50°C and +50°C of the glass transition point of polyarylene ether ketone resin 2, preferably between −30°C and +30°C of the glass transition point of polyarylene ether ketone resin 2, and more preferably between −20°C and +20°C of the glass transition point of polyarylene ether ketone resin 2. The heat-drying time for molding material 1 is 2 hours or more, preferably 4 hours or more, and more preferably 8 hours or more. The upper limit of this heat-drying time is not particularly limited, but 24 hours or less is appropriate.

[0074] Once the molding material 1 is prepared, the conductive resin film 4 for a current collector is manufactured using this molding material 1. This manufacturing method can be a melt extrusion method, a calendar molding method, a casting method, or the like. Among these manufacturing methods, the melt extrusion method, which allows the conductive resin film 4 for a current collector to be continuously extruded into a strip shape, is optimal from the viewpoints of improving the thickness accuracy, productivity, and handleability of the conductive resin film 4 for a current collector, and simplifying the equipment.

[0075] The melt extrusion molding method is a method for producing a conductive resin film 4 for a current collector by melt-kneading a molding material 1 using a melt extruder 20 and continuously extruding it from a die 23, such as a T-die or a round die, connected to the tip of the melt extruder 20 (see FIG. 2). As shown in FIG. 2, the melt extruder 20 is, for example, a single-screw extruder or a twin-screw extruder, and has a raw material inlet 21 for the molding material installed at the upper rear. This raw material inlet 21 is connected to an inert gas supply pipe 22 that supplies an inert gas such as helium gas, neon gas, argon gas, krypton gas, or nitrogen gas as needed. The supply of inert gas from this inert gas supply pipe 22 effectively prevents oxidative degradation, oxygen crosslinking, and thermal crosslinking of the molding material 1.

[0076] The melting temperature during melt-kneading in the melt extrusion molding machine 20 is not particularly limited as long as it is a temperature at which melt-kneading dispersion is possible and there is no decomposition of the polyarylene ether ketone resin 2, but it is preferably in the range of not less than the melting point of the polyarylene ether ketone resin 2 but less than the thermal decomposition temperature of the polyarylene ether ketone resin 2.

[0077] Specifically, the temperature ranges from the melting point of polyarylene ether ketone resin 2 +10°C to the polyarylene ether ketone resin 2 +100°C, preferably from the polyarylene ether ketone resin 2 +20°C to the polyarylene ether ketone resin 2 +80°C, more preferably from the polyarylene ether ketone resin 2 +30°C to the polyarylene ether ketone resin 2 +60°C, and even more preferably from the melting point of polyarylene ether ketone +30°C to the melting point of polyarylene ether ketone resin 2 +50°C. This is because, if the temperature is below the melting point of polyarylene ether ketone resin 2, melt extrusion molding of the molding material 1 becomes difficult, and conversely, if the temperature exceeds the thermal decomposition temperature, polyarylene ether ketone resin 2 may be severely decomposed.

[0078] The die 23 is connected to the tip of the melt extruder 20 via a connecting pipe 24, and functions to continuously extrude a strip-shaped conductive resin film 4 for a current collector downward. A T-die is suitable for this die 23, which is capable of producing a conductive resin film 4 for a current collector with excellent thickness precision. A gear pump 25 is preferably attached to the connecting pipe 24 upstream of the die 23. Use of this gear pump 25 makes it possible to transfer the molding material 1 melt-kneaded by the melt extruder 20 to the downstream die 23 at a constant flow rate and with high precision.

[0079] The temperature during extrusion of the die 23 should be in the range of not less than the melting point of the polyarylene ether ketone resin 2 but less than the thermal decomposition temperature of the polyarylene ether ketone resin 2, specifically, not less than the melting point of the polyarylene ether ketone resin 2 +10°C but not more than the melting point of the polyarylene ether ketone resin 2 +100°C, preferably not less than the melting point of the polyarylene ether ketone resin 2 +20°C but not more than the melting point of the polyarylene ether ketone resin 2 +80°C, more preferably not less than the melting point of the polyarylene ether ketone resin 2 +30°C but not more than the melting point of the polyarylene ether ketone resin 2 +60°C, and even more preferably not less than the melting point of the polyarylene ether ketone +30°C but not more than the melting point of the polyarylene ether ketone +50°C.

[0080] This is because if the temperature is below the melting point of the polyarylene ether ketone resin 2, it becomes difficult to melt extrude the molding material 1, and conversely, if the temperature exceeds the thermal decomposition temperature, the polyarylene ether ketone resin 2 may decompose violently.

[0081] Below the die 23, a pair of pressure rolls 26 facing each other at a distance are rotatably supported, and between the pair of pressure rolls 26, a plurality of cooling rolls 27 arranged in a row and in sliding contact with each other are rotatably supported, and of the plurality of cooling rolls 27, the upstream cooling roll 27 and the downstream cooling roll 27 each slide against the circumferential surface of the pressure roll 26. The pair of pressure rolls 26 and the plurality of cooling rolls 27 are configured such that the pressure roll 26 has a reduced diameter and the cooling rolls 27 have an expanded diameter.

[0082] Of the pair of pressure rolls 26, a winder 28 is installed downstream of the downstream pressure roll 26, which winds the conductive resin film 4 for the current collector onto a rotatable winding tube 29. Between the downstream pressure roll 26 and the winder 28, a slit blade 30 is arranged to be able to rise and fall, which forms a slit in the longitudinal direction of the side of the conductive resin film 4 for the current collector. A required number of rotatable tension rolls 31 are supported between this slit blade 30 and the winder 28, which apply tension to the conductive resin film 4 for the current collector so that it can be wound up smoothly.

[0083] Each pressure roller 26 is adjusted to a temperature of 50°C or higher but lower than the melting point of the polyarylene ether ketone resin 2, preferably 100°C or higher but lower than [melting point of polyarylene ether ketone resin 2 - 50°C], more preferably 130°C or higher but lower than [melting point of polyarylene ether ketone resin 2 - 100°C], and even more preferably 150°C or higher but lower than [polyarylene ether ketone resin 2 - 100°C], and slides against the conductive resin film 4 for current collector and presses it against the cooling roller 27.

[0084] The reason why the temperature of the pressure roller 26 is within this range is that if the temperature is below 50°C, condensation will form on the pressure roller 26. Conversely, if the temperature exceeds the melting point, the conductive resin film 4 for current collector may stick to the peripheral surface of the pressure roller 26 and break, or the strength of the conductive resin film 4 for current collector may decrease, leading to breakage. Methods for adjusting the temperature of the pressure roller 26 include, for example, a method using a heat medium such as air, water, or oil, a method using an electric heater, and a method using induction heating.

[0085] To improve the adhesion between the conductive resin film 4 for current collector and the cooling roll 27, the peripheral surface of each pressure roll 26 is coated with a rubber layer, such as at least natural rubber, isoprene rubber, butadiene rubber, norbornene rubber, acrylonitrile butadiene rubber, nitrile rubber, urethane rubber, silicone rubber, or fluororubber, as needed, and an inorganic compound, such as silica or alumina, is selectively added to this rubber layer. Of these, silicone rubber and fluororubber, which have excellent heat resistance, are preferably selected.

[0086] As the pressure roll 26, a metal elastic roll with a metal surface may be used as needed. When this metal elastic roll is used, it is possible to form a conductive resin film 4 for a current collector with an excellent surface smoothness. Specific examples of this metal elastic roll include a metal sleeve roll, an air roll (manufactured by Dymco Corporation: product name), and a UF roll (manufactured by Hitachi Zosen Corporation: product name). It is also possible to use a pressure roll 26 whose surface is coated with a fluororesin film such as polytetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) resin or tetrafluoroethylene-hexafluoropyrene copolymer (FEP) resin.

[0087] The multiple cooling rolls 27 are, for example, metal rolls with a larger diameter than the pressure-bonding roll 26, and are rotatably supported below the die 23 to sandwich the extruded conductive resin film 4 for the current collector between themselves and the peripheral surface of the pressure-bonding roll 26, and function to cool the conductive resin film 4 for the current collector together with the pressure-bonding roll 26 while controlling its thickness within a predetermined range.

[0088] For the same reasons as for the pressure roll 26, each cooling roll 27 is adjusted to a temperature of 50°C or higher and lower than the melting point of polyarylene ether ketone resin 2, preferably 100°C or higher and lower than [melting point of polyarylene ether ketone resin 2 - 50°C], more preferably 130°C or higher and lower than [melting point of polyarylene ether ketone resin 2 - 100°C], and even more preferably 150°C or higher and lower than [polyarylene ether ketone resin 2 - 100°C], and is brought into sliding contact with the conductive resin film 4 for current collector, and this is pressed against the opposing cooling roll 27. Methods for adjusting the temperature of the cooling roll 27 include, for example, a method using a heat medium such as air, water, or oil, a method using an electric heater, and a method utilizing induction heating.

[0089] After the molding material 1 is extrusion-molded into a strip-shaped conductive resin film 4 for a current collector, this conductive resin film 4 for a current collector is wound around a pair of pressure-bonding rolls 26, a plurality of cooling rolls 27, a tension roll 31, and a winder 28, and both side portions of the conductive resin film 4 for a current collector are cut in the longitudinal direction with a slit blade 30, and the film is sequentially wound around a winding tube 29 of the winder 28, thereby producing a long conductive resin film 4 for a current collector.

[0090] The thickness of the conductive resin film 4 for a current collector produced by cooling with the cooling roll 27 is preferably 10 μm to 500 μm, more preferably 15 μm to 350 μm, more preferably 20 μm to 200 μm, and even more preferably 25 μm to 100 μm. This is because if the thickness of the conductive resin film 4 for a current collector is less than 10 μm, the tensile strength of the conductive resin film 4 for a current collector is significantly reduced, making it difficult to produce. Conversely, if the thickness of the conductive resin film 4 for a current collector exceeds 500 μm, weight reduction will be hindered when the film is used as a current collector for a lithium-ion secondary battery, a bipolar lithium-ion secondary battery, or an all-solid-state battery. The thickness of the conductive resin film 4 for a current collector can be measured using various contact thickness gauges.

[0091] The specific gravity of the conductive resin film 4 for a current collector, measured in accordance with JIS K 7112 Method A, is preferably 1.25 to 1.60, more preferably 1.30 to 1.50, more preferably 1.31 to 1.45, and even more preferably 1.32 to 1.40. This is because if the specific gravity of the conductive resin film 4 for a current collector is less than 1.25, voids or cracks may occur in the conductive resin film 4 for a current collector, which may result in a decrease in mechanical strength, and is therefore undesirable.

[0092] On the other hand, if the specific gravity of the conductive resin film 4 for current collector exceeds 1.60, it will hinder weight reduction when used as a current collector for a secondary battery such as a lithium ion secondary battery, a bipolar lithium ion secondary battery, or an all-solid-state battery. The specific gravity of the conductive resin film 4 for current collector can be measured using a specific gravity measuring device or the like in accordance with JIS K 7112 Method A, for example.

[0093] The relative crystallinity of the conductive resin film 4 for a current collector is optimally 80% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 100%. This is because if the relative crystallinity of the conductive resin film 4 for a current collector is less than 80%, problems arise in the mechanical strength, heat resistance, chemical resistance, and solvent resistance of the conductive resin film 4 for a current collector. In contrast, if the relative crystallinity is more than 80%, the conductive resin film 4 for a current collector can be expected to have sufficient mechanical strength, heat resistance, and chemical resistance to be usable as a conductive resin film 4 for a current collector.

[0094] The crystallinity of the conductive resin film 4 for a current collector can be expressed as a relative crystallinity, which is calculated by the following formula based on the results of thermal analysis measured at a heating rate of 10°C / min using a differential scanning calorimeter.

[0095] Relative crystallinity (%) = {1-(ΔHc / ΔHm)} × 100 ΔHc: Heat quantity at the recrystallization peak of the conductive resin film for the current collector (J / g) ΔHm: Heat of melting peak of conductive resin film for current collector (J / g) The conductivity of the conductive resin film 4 for current collector can be evaluated by the resistance value when measured by applying a pressure of 1 MPa in the thickness direction. The resistance value when measured by applying a pressure of 1 MPa in the thickness direction is 1000 mΩ cm 2 Less than or equal to 1 mΩ·cm, preferably 2 More than 1000mΩ cm 2 Less than or equal to 1 mΩ·cm, preferably 2 More than 800mΩ cm 2 or less, more preferably 50 mΩ·cm 2More than 600mΩ cm 2 Preferably, the resistance is 90 mΩ cm or less. 2 More than 500mΩ cm 2 The following is optimal:

[0096] This indicates that the resistance value measured by applying a pressure of 1 MPa in the thickness direction of the conductive resin film 4 for current collector is 1000 mΩ cm 2 When the resistance exceeds 1 mΩ cm, the energy density decreases when the material is used as a current collector for a secondary battery. 2 If the content is less than this, a large amount of conductive material 3 must be added, which makes the resulting conductive resin film 4 for current collector brittle, resulting in the problem of the conductive resin film 4 for current collector cracking during assembly of the secondary battery.

[0097] The chemical resistance of the conductive resin film 4 for a current collector can be evaluated by immersing the conductive resin film 4 for a current collector in N-methyl-2-pyrrolidone and an electrolyte and measuring the change in mass. From the viewpoint of improving chemical resistance and solvent resistance, the rate of mass change when the conductive resin film 4 for a current collector is immersed in N-methyl-2-pyrrolidone and an electrolyte is optimally 2.0% or less, preferably 0.0% to 2.0%, more preferably 0.0% to 1.0%, and even more preferably 0.0% to 0.1%.

[0098] The electrolyte is an organic electrolytic solution containing a lithium salt dissolved in an organic solvent. Examples of the organic solvent include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), linear carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), cyclic ethers such as tetrahydrofuran (THF) and 1,3-dioxolane (DOXL), linear ethers such as 1,2-dimethoxyethane (DEM) and 1,2-diethoxyethane (DEE), cyclic esters such as gamma-butyrolactone (GBL), and linear esters such as methyl acetate (MA).

[0099] Examples of lithium salts include lithium perchlorate (LiClO4), lithium borofluoride (LiBF4), lithium hexafluorophosphate (LiPF6), lithium trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2), and lithium tris(trifluoromethanesulfonyl)methide (LiC(CF3SO2)3).

[0100] If N-methyl-2-pyrrolidone or the electrolyte remains in the conductive resin film for current collector 4, the N-methyl-2-pyrrolidone or the electrolyte may seep into the secondary battery during operation, causing problems, so care must be taken. Also, care must be taken because the electrolyte of the secondary battery may seep into the current collector, reducing the charge / discharge cycle.

[0101] The molded conductive resin film 4 for a current collector may be used as is, or may be further subjected to heat compression molding. Heat compression molding of the conductive resin film 4 for a current collector can lower the resistance value and increase the conductivity, and can reduce the amount of conductive material 3 used, thereby reducing costs.

[0102] When the conductive resin film 4 for a current collector is subjected to heat compression molding, the conductive resin film 4 for a current collector is sandwiched between a plurality of metal plates, metal rolls, or metal belts that have been heated to a temperature not lower than the melting point of the polyarylene ether ketone resin 2 but lower than the thermal decomposition temperature of the polyarylene ether ketone resin 2, specifically, not lower than the melting point of the polyarylene ether ketone resin 2 +10°C and not higher than the melting point of the polyarylene ether ketone resin 2 +100°C, preferably not lower than the melting point of the polyarylene ether ketone resin 2 +20°C and not higher than the melting point of the polyarylene ether ketone resin 2 +80°C, more preferably not lower than the melting point of the polyarylene ether ketone resin 2 +30°C and not higher than the melting point of the polyarylene ether ketone resin 2 +60°C, and even more preferably not lower than the melting point of the polyarylene ether ketone resin 2 +30°C and not higher than the melting point of the polyarylene ether ketone resin 2 +50°C, and a pressure of 0.5 kgf / cm against the projected area of ​​the conductive resin film 4 for a current collector is applied. 2More than 100kgf / cm 2 The pressure is applied to the polyarylene ether ketone resin 2, and the pressure is maintained for 0.5 seconds to 300 seconds, and the polyarylene ether ketone resin 2 is immediately cooled to a temperature below the glass transition point.

[0103] According to the above, the polyarylene ether ketone resin 2, which is lightweight, excellent in mechanical properties, chemical resistance, and heat resistance, and has low water absorption, is selected as the thermoplastic resin of the molding material 1 to manufacture the conductive resin film 4 for a current collector, so that even if the conductive resin film 4 for a current collector is used as a current collector, electrolyte components do not penetrate into the conductive resin film 4 for a current collector, effectively eliminating the risk of a decrease in charge-discharge cycle characteristics. Furthermore, because the polyarylene ether ketone resin 2 is used instead of a fluororesin, no special steel material or equipment is required for molding, and significant cost reductions in the current collector can be expected.

[0104] Furthermore, since there is no need to use two different types of resin, the risk of peeling of the current collector can be effectively eliminated. In addition, there is no risk of curling due to differences in expansion coefficients caused by water absorption after production, or peeling of the current collector between the first and second conductive layers. Furthermore, when the carbon-based conductive material is carbon nanotubes, it is chemically stable and can further reduce the weight of the secondary battery. Furthermore, since conductive materials other than carbon nanotubes are also used, significant improvement in the conductivity of the conductive resin film 4 for the current collector in the thickness direction can be expected.

[0105] Furthermore, since the thickness of the conductive resin film 4 for the current collector is 10 μm or more and 500 μm or less, a decrease in the tensile strength of the conductive resin film 4 for the current collector is prevented, and a weight reduction of the current collector of the secondary battery can be expected. Furthermore, since the specific gravity of the conductive resin film 4 for the current collector is 1.60 or less, it can contribute to a significant weight reduction of the secondary battery and the current collector. Furthermore, the resistance value when measured by applying a pressure of 1 MPa in the thickness direction of the conductive resin film 4 for the current collector is 1000 mΩ cm 2 Since the energy density is as low as or less, even if the conductive resin film 4 for a current collector is used as a current collector of a secondary battery, a decrease in energy density can be prevented.

[0106] The shape of the polyarylene ether ketone resin 2 of the molding material 1 in the above embodiment does not particularly matter and may be in the form of powder, granules, lumps, powder, pellets, etc. The conductive resin film 4 for current collector has a relative crystallinity of 95% or more and 100% or less, and a resistance of 1 mΩ cm when measured by applying a pressure of 1 MPa in the thickness direction. 2 More than 1000mΩ cm 2 Furthermore, a single cooling roll 27 may be rotatably supported between the pair of pressure rolls 26. [Example]

[0107] EXAMPLES Hereinafter, examples of a conductive resin film for a current collector of a secondary battery according to the present invention and a method for producing the same will be described together with comparative examples. Example 1 First, to prepare the molding material, a commercially available polyether ether ketone resin (manufactured by Solvay Specialty Polymers, product name: KetaSpire PEEK KT-851NL SP (hereinafter abbreviated as "KT-851NL SP")) was prepared as the polyarylene ether ketone resin, and this polyether ether ketone resin was pulverized by a freeze-pulverization method.

[0108] The melting point (also called melting temperature) of polyether ether ketone resin (hereinafter referred to as PEEK resin) was measured using a differential scanning calorimeter (SII NanoTechnology, product name: High Sensitivity Differential Scanning Calorimeter X-DSC7000) at a heating rate of 10°C / min in accordance with JIS K7121. The melting point of KT-851NLSP was measured to be 340°C.

[0109] After the PEEK resin was pulverized, a conductive material consisting of a mixture of the pulverized PEEK resin, carbon nanotubes that had been previously stirred and mixed in a mixer, and a conductive material other than the carbon nanotubes was weighed out so that the conductive material was 8 parts by mass per 100 parts by mass of PEEK resin, as shown in Table 1.The PEEK resin and the conductive material were then added to a mixer and stirred and mixed to prepare a stirred mixture.

[0110] The carbon nanotubes used were NC7000 (manufactured by Nanosil Co., Ltd.; product name: (hereinafter abbreviated as "NC7000")), and the conductive material other than carbon nanotubes was spherical amorphous carbon, Bellpearl C2000SR (manufactured by Air Water Bellpearl Co., Ltd.; product name, average particle size: 8 μm (catalog value); (hereinafter abbreviated as "C2000SR")). The carbon nanotubes and conductive materials other than carbon nanotubes were weighed out so that the ratio of carbon nanotubes was 95% by mass and conductive materials other than carbon nanotubes was 5% by mass, as shown in Table 1. The carbon nanotubes and amorphous carbon were then placed in a mixer and mixed under stirring to prepare a stirred mixture.

[0111] The apparent shear viscosity of the PEEK resin was measured using a flow tester (Shimadzu Corporation, product name: Shimadzu Flow Tester CFT-500D). Specifically, the PEEK resin was dried in a hot air dryer at 160°C for 12 hours, and then 1.5 cm of the PEEK resin was dried. 3 The mixture was packed into a cylinder at 375°C attached to a die (diameter: 1 mm, length: 10 mm), and a 1.0 cm2 cylinder was placed on top of the cylinder. 2 A plunger was attached, and when the temperature of the cylinder reached 375°C, it was preheated for 5 minutes, and immediately after this preheating, a load of 50 kgf was applied to melt and flow out the PEEK resin, and its apparent shear viscosity was measured. The apparent shear viscosity was measured in the same manner as below.

[0112] Once the stirred mixture was prepared, it was fed into a co-rotating twin-screw extruder equipped with a vacuum pump and melt-kneaded under reduced pressure. The melt-kneaded mixture was extruded into rods through the die at the end of the co-rotating twin-screw extruder, cooled with water, and cut to prepare pellet-shaped molding materials. The co-rotating twin-screw extruder was a φ25mm, L / D=41 type. The stirred mixture was melt-kneaded under conditions of a cylinder temperature of 300°C to 370°C and a die temperature of 370°C, with the vent on the raw material inlet side of the co-rotating twin-screw extruder open and the vent on the die side degassed under reduced pressure to prepare molding materials. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was measured to be 372°C.

[0113] The prepared molding material was then placed in a dehumidifying hot air dryer heated to 160°C and dried for at least 12 hours. After confirming that the moisture content of the dried molding material was 300 ppm or less, the molding material was placed in a φ20 mm single-screw extruder and continuously extruded through a 150 mm wide T-die to form a strip-shaped conductive resin film for a current collector. The moisture content of the molding material was confirmed by Karl Fischer titration using a trace moisture analyzer (Mitsubishi Chemical Corporation, product name: CA-100). The moisture content of the molding material was subsequently measured using the same method.

[0114] The single-screw extruder had an L / D ratio of 25, a compression ratio of 2.5, and a full-flight screw type screw. The temperature of the single-screw extruder was adjusted to 360°C to 395°C, the temperature of the T-die to 395°C, and the temperature of the connecting pipe connecting the single-screw extruder to the T-die to 395°C. The temperature of the molten molding material was measured from the resin temperature at the inlet of the T-die and was found to be 398°C. When the molding material was introduced into this single-screw extruder, nitrogen gas was supplied at a rate of 15 L / min.

[0115] After the conductive resin film for a current collector was formed, this conductive resin film for a current collector was sequentially wound around a pair of silicone rubber pressure rolls (210°C) and cooling rolls (220°C) as shown in Figure 2, and a 6-inch take-up tube of a winder located downstream of these, and the continuous conductive resin film for a current collector was sandwiched between the pressure rolls and the cooling roll, and sequentially taken up around the take-up tube, thereby producing a conductive resin film for a current collector having a length of 10 m and a width of 150 mm.

[0116] After producing the conductive resin film for current collectors, the presence or absence of die buildup during production of the conductive resin film for current collectors, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of the conductive resin film for current collectors were evaluated, and the results are summarized in Table 1. The chemical resistance of the conductive film for current collectors was evaluated based on the weight change before and after immersion in NMP and electrolyte. The conductivity of the conductive film for current collectors was also evaluated based on the resistance value in the thickness direction before and after immersion in electrolyte. -Whether or not there is any pitting that occurs during the manufacturing of conductive resin film for current collectors To check for the occurrence of die buildup during the production of conductive resin film for current collectors, the vicinity of the T-die lip was visually observed after 10 m of conductive resin film for current collectors was produced.

[0117] Thickness of conductive resin film for current collector The thickness of the conductive resin film for the current collector was measured using a micrometer (Mitutoyo Corporation, product name: Coolant-proof micrometer, model MDC-25PJ). Measurements were taken at 10 random locations in the extrusion direction (hereinafter abbreviated as "MD") at the center of the width direction (direction perpendicular to the extrusion direction (hereinafter abbreviated as "TD")) of the conductive resin film for the current collector, and the average value was taken as the film thickness.

[0118] Specific gravity of conductive resin film for current collector The specific gravity of the conductive resin film for current collector was measured in an environment of 23°C in accordance with the standard of JIS K7112 Method A.

[0119] Relative crystallinity of conductive resin film for current collector The relative crystallinity of the conductive resin film for current collectors was measured by weighing out approximately 5 mg of a measurement sample from the conductive resin film for current collectors and using a differential scanning calorimeter (manufactured by SII Nanotechnologies, product name: High Sensitivity Differential Scanning Calorimeter X-DSC7000) at a heating rate of 10°C / min over a measurement temperature range of 20°C to 380°C. The heat quantity (J / g) of the melting peak and the heat quantity (J / g) of the recrystallization peak obtained at this time were used to calculate the crystallinity using the following formula.

[0120] Relative crystallinity (%) = {1-(ΔHc / ΔHm)} × 100 ΔHc: Heat quantity at the recrystallization peak of the conductive resin film for the current collector (J / g) ΔHm: Heat of melting peak of conductive resin film for current collector (J / g)

[0121] Chemical resistance of conductive resin film for current collectors The chemical resistance of the conductive resin film for current collectors was evaluated by immersing it in N-methyl-2-pyrrolidone (NMP) and electrolyte and measuring the weight change. To evaluate this weight change, the conductive resin film for current collectors was cut into a size of 55 mm MD x 55 mm TD and weighed [W0]. The conductive resin film and 5 g of NMP or 5 g of electrolyte were placed in a PET / AL / PE flat bag (manufactured by Nippon Seisaku Co., Ltd.: trade name Lamizip) and heat-sealed. The electrolyte used was an electrolyte for lithium primary / secondary / polymer batteries and lithium-ion capacitors (manufactured by Kishida Chemical Co., Ltd.: trade name LiPF6, molarity 1 mol / L, solvent EC:DEC (3:7) V / V%).

[0122] After heat sealing, the PET / AL / PE flat bag was left to stand in a hot air oven heated to 50°C for 15 days. After standing, the conductive resin film for the current collector was removed from the PET / AL / PE flat bag and washed with ethanol. This conductive resin film for the current collector was left to stand in a hot air oven heated to 50°C for 24 hours, and after standing, it was left to stand in a glass desiccator containing a desiccant (manufactured by Ozone Chemical Co., Ltd.: product name OZO-C) in an environment of 24°C for 24 hours. Thereafter, the conductive resin film for the current collector was weighed [W1] and the weight change rate was calculated and evaluated using the following formula:

[0123] Weight change rate (%) = {(W1-W0) x 100} / W0 W0: Initial weight of conductive resin film for current collector [g] W1: Weight of the conductive resin film for the current collector after immersion in NMP or electrolyte [g] A: When the weight change rate is between 0.0% and 0.1% B: Weight change rate is over 0.1% and 1.0% or less C: Weight change rate is over 1.0% and 2.0% or less D: Weight change rate is over 2.0% and 5.0% or less E: Weight change rate is over 5.0% and 10% or less F: Weight change rate is over 10% and 20% or less

[0124] Conductivity of conductive resin film for current collector The conductivity of the conductive resin film for current collectors was evaluated by the resistance value in the thickness direction. To evaluate the resistance value in the thickness direction (Rc), a test piece was prepared by cutting the conductive resin film for current collectors to a size of 5.5 cm x 5.5 cm, as shown in Figures 2 and 3. The test piece was sandwiched between a pair of 5.0 cm x 5.0 cm carbon paper strips, and the pair of carbon paper strips was sandwiched between a pair of gold-plated electrodes. A direct current was applied, and a pressure of 1 MPa was applied from above. The resistance value (R0) after 1 minute was measured with a resistance meter, and the resistance value was calculated using the following formula:

[0125] Rc=R1×S R1 = R0 - (resistance of two sheets of carbon paper) S: Area of ​​carbon paper

[0126] The carbon paper used was SIGRACET Gas Diffusion Media type GDL24B (trade name, manufactured by SGL GROUP), and the resistance meter used was Milliohm HiTester 3540 (trade name, manufactured by Hioki E.E. Corporation).

[0127] The resistance value (Rc) through the thickness direction was measured before and after a chemical resistance test using the conductive resin film for the current collector and an electrolyte for lithium primary / secondary polymer batteries and lithium ion capacitors (Kishida Chemical Co., Ltd., product name: electrolyte LiPF6, molar concentration 1 mol / L, solvent EC:DEC (3:7) V / V%). The measurement was carried out in an environment of a temperature of 23°C ± 2°C and a relative humidity of 50 RH ± 5% RH.

[0128] Example 2 The polyarylene ether ketone resin and conductive material of Example 1 were weighed as shown in Table 1, and a pellet-shaped molding material was prepared in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was found to be 371°C. The conductive material used was the carbon nanotubes used in Example 1, and amorphous carbon as a conductive material other than carbon nanotubes, with the amounts added being changed. The carbon nanotubes and amorphous carbon were weighed to have the composition mass ratio shown in Table 1, and then charged into a mixer and stirred and mixed to prepare a conductive material.

[0129] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and was found to be 398°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film for a current collector was produced in the same manner as in Example 1, and the generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of the conductive resin film for a current collector were evaluated in the same manner as in the examples and the results are summarized in Table 1.

[0130] Example 3 The process was basically the same as in Example 1, except that the molding material, PEEK resin, which is a polyarylene ether ketone resin used in Example 1, was changed from KT-851NL SP to Victrex Granules 381G (Victrex Corporation; product name (hereinafter abbreviated as "381G")) which had been pulverized in advance using the method of Example 1, and the PEEK resin and conductive material were weighed to obtain the mass ratio shown in Table 1 to prepare a stirred mixture.

[0131] The conductive materials used were the same as those used in Example 1, with amorphous carbon used as a conductive material other than carbon nanotubes, but the amounts added were changed. The carbon nanotubes and amorphous carbon were weighed to achieve the composition mass ratio shown in Table 1, and then the carbon nanotubes and amorphous carbon were added to a mixer and stirred and mixed to prepare a conductive material. The apparent shear viscosity of 381G was measured using the same method as in Example 1. The melting point of 381G was measured using the same method as in Example 1 and was found to be 343°C.

[0132] Next, a molding material was prepared in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was found to be 372°C.

[0133] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and was found to be 398°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film for a current collector was produced in the same manner as in Example 1, and the generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of the conductive resin film for a current collector were evaluated in the same manner as in Example 1 and the results are summarized in Table 1.

[0134] [Table 1]

[0135] Example 4 The example was basically the same as in Example 1, except that the PEEK resin, which is a polyarylene ether ketone resin, was changed from KT-851NL SP to Victrex Granules 450G (manufactured by Victrex; product name (hereinafter abbreviated as "450G")) which had been previously pulverized by the method of Example 1. This PEEK resin and conductive material were weighed out so as to obtain the mass ratio shown in Table 2, and a stirred mixture was prepared.

[0136] The carbon nanotubes were changed from NC7000 used in Example 1 to FloTube 9000 (product name, manufactured by CNano Technology). In addition, the conductive material other than the carbon nanotubes was changed from the amorphous carbon C2000SR used in Example 1 to amorphous carbon with spherical particle shape, Bellpearl CR1-2000 (product name, manufactured by Air Water Bellpearl, average particle size: 1.2 μm (catalog value), hereinafter abbreviated as "CR1-2000")

[0137] The conductive material was prepared by weighing carbon nanotubes and amorphous carbon to obtain the composition mass ratio shown in Table 2, charging them into a mixer, and stirring and mixing them. The apparent shear viscosity of 450G was measured in the same manner as in Example 1. The melting point of 450G was also measured in the same manner as in Example 1 and was found to be 341°C.

[0138] Next, a molding material was prepared in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molding material in a molten state immediately after extrusion from the die, and was found to be 373°C.

[0139] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and was found to be 396°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film for a current collector was produced in the same manner as in Example 1, and the generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of the conductive resin film for a current collector were evaluated using the methods of Example 1, and the results are summarized in Table 2.

[0140] Example 5 The process was basically the same as in Example 1, except that the molding material, PEEK resin, which is a polyarylene ether ketone resin used in Example 1, was changed from KT-851NL SP to Victrex Granules 151G (Victrex; product name (hereinafter abbreviated as "151G"), which had been previously pulverized using the method of Example 1, and the PEEK resin and the conductive material were weighed to obtain the mass ratio shown in Table 2, to prepare a stirred mixture.

[0141] The apparent shear viscosity of 151G was measured in the same manner as in Example 1. The melting point of 151G was measured in the same manner as in Example 1 and was found to be 341°C. The conductive material was prepared by using the carbon nanotubes and amorphous carbon used in Example 4, measuring them so as to have the composition mass ratio shown in Table 2, and adding them to a mixer and stirring and mixing them.

[0142] Next, a molding material was prepared in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was found to be 375°C.

[0143] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and was found to be 395°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film was produced in the same manner as in Example 1, and the generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of the conductive resin film for a current collector were evaluated in the same manner as in Example 1 and the results are summarized in Table 2.

[0144] Example 6 First, to prepare the molding material, a polyether ketone ketone resin (manufactured by Arkema, product name: KEPSTAN 8003PF ST (hereinafter abbreviated as "8003PF") was prepared as a commercially available polyarylene ether ketone resin, and this polyether ketone ketone resin (hereinafter abbreviated as PEKK resin) and the conductive material used in Example 1 were weighed out to obtain the mass ratio shown in Table 2. Thereafter, the PEKK resin and the conductive material were placed in a mixer and stirred to prepare a stirred mixture.

[0145] The conductive materials used were the carbon nanotubes used in Example 1 and amorphous carbon, a conductive material other than the carbon nanotubes. The conductive materials were weighed to have the composition weight ratios shown in Table 2, and then charged into a mixer and mixed by stirring to prepare the conductive materials. The melting point of 8003PF was measured using the same method as in Example 1 and was found to be 361°C.

[0146] The apparent shear viscosity of 8003PF was measured using a flow tester (Shimadzu Corporation, product name: Shimadzu Flow Tester CFT-500D). Specifically, 8003PF was dried in a hot air dryer at 160°C for 12 hours, and then dried at 1.5cm. 3The 8003PF was filled into a cylinder at 375°C attached to a die (diameter: 1 mm, length: 10 mm), and a 1.0 cm2 area was placed on top of the cylinder. 2 A plunger was attached, and when the temperature of the cylinder reached 375°C, it was preheated for 5 minutes, and immediately after this preheating, a load of 50 kgf was applied to melt and flow out the PEKK resin, and its apparent shear viscosity was measured.

[0147] Next, a molding material was prepared in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was found to be 375°C.

[0148] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and was found to be 397°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film for a current collector was produced in the same manner as in Example 1, and the generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of the conductive resin film for a current collector were evaluated in the same manner as in Example 1 and the results are summarized in Table 2.

[0149] [Table 2]

[0150] Comparative Example 1 First, the polyarylene ether ketone resin and conductive material used in Example 1 were weighed out in a mass ratio outside the range of the present invention shown in Table 3 and charged into a stirring mixer to prepare a stirred mixture, and this stirred mixture was prepared into a pellet-shaped molding material in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was found to be 371°C.

[0151] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and found to be 398°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film for a current collector was produced in the same manner as in Example 1. The generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of this conductive resin film for a current collector were each evaluated in the same manner as in Example 1 and the results are shown in Table 3. As a result, the conductivity of the conductive resin film for a current collector was significantly deteriorated.

[0152] Comparative Example 2 First, the polyarylene ether ketone resin and conductive material used in Example 1 were weighed out in a mass ratio outside the range of the present invention shown in Table 3 and charged into a stirring mixer to prepare a stirred mixture, and this stirred mixture was prepared into a pellet-shaped molding material in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was found to be 379°C.

[0153] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape with a thickness of 450 μm in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and found to be 403°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film for a current collector was produced in the same manner as in Example 1, and the generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of this conductive resin film for a current collector were evaluated in the same manner as in Example 1 and are listed in Table 3. As a result, the chemical resistance of the conductive resin film for a current collector was deteriorated.

[0154] Comparative Example 3 First, the polyarylene ether ketone resin used in Example 1 and the carbon nanotubes used in Example 4 were weighed out in a mass ratio outside the range of the present invention shown in Table 3 and charged into a stirring mixer to prepare a mixture. In this Comparative Example 3, no conductive material other than the carbon nanotubes was used. After preparing the mixture, this mixture was processed into a pellet-shaped molding material in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was measured to be 372°C.

[0155] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and found to be 393°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film for a current collector was produced in the same manner as in Example 1. The generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of this conductive resin film for a current collector were each evaluated in the same manner as in Example 1 and the results are shown in Table 3. As a result, the conductivity of the conductive resin film for a current collector was deteriorated.

[0156] [Table 3]

[0157] Comparative Example 4 First, the carbon nanotubes and amorphous carbon used in Example 1 were weighed out in a composition mass ratio outside the range of the present invention shown in Table 3, and charged into a stirring mixer to prepare a conductive material. After the conductive material was prepared in this manner, the conductive material and the polyarylene ether ketone resin used in Example 1 were weighed out in a mass ratio within the range of the present invention shown in Table 3, and charged into a stirring mixer to prepare a stirred mixture. This stirred mixture was then prepared into a pellet-shaped molding material in the same manner as in Example 1. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was found to be 371°C.

[0158] Next, the prepared molding material was used to mold a conductive resin film for a current collector into a strip shape in the same manner as in Example 1. The temperature of the molten molding material was measured from the resin temperature at the entrance of a T-die and found to be 393°C. After molding the conductive resin film for a current collector in this manner, a conductive resin film for a current collector was produced in the same manner as in Example 1. The generation of die boogers during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of this conductive resin film for a current collector were evaluated in the same manner as in Example 1 and the results are shown in Table 4. As a result, the conductivity of the conductive resin film for a current collector was deteriorated.

[0159] Comparative Example 5 First, a conductive resin film for a current collector having a relative crystallinity of 37% was molded in the same manner as in Example 1 using the molding material composed of the polyarylene ether ketone resin and conductive material used in Example 3. However, while the temperatures of the pressure roll and the chill roll were 210°C and 220°C in Example 1, the conductive resin film for a current collector was molded into a strip shape at 100°C for the pressure roll and 100°C for the chill roll in Comparative Example 5. The temperature of the molten molding material was measured from the resin temperature at the entrance of the T-die and was found to be 398°C.

[0160] After forming the conductive resin film for a current collector in this manner, the conductive resin film for a current collector was produced in the same manner as in Example 1, and the generation of die deposits during the production of the conductive resin film for a current collector, as well as the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of the conductive resin film for a current collector were evaluated in the same manner as in Example 1, and the results are shown in Table 4. As a result, the chemical resistance of the conductive resin film for a current collector was deteriorated.

[0161] [Table 4]

[0162] Comparative Example 6 To prepare the molding material, polyarylene ether ketone resin was replaced with polyamide 9T resin. Genestar N1000A-M42NA (product name, manufactured by Kuraray Co., Ltd., hereinafter abbreviated as "N1000A") was selected as the polyamide 9T resin, and this polyamide 9T resin (hereinafter abbreviated as PA9T resin) was pulverized by a freeze-pulverization method. This PA9T resin and the conductive material used in Example 1 were stirred and mixed in the mass ratio shown in Table 5 to prepare a stirred mixture.

[0163] The melting point of N1000A resin was measured using a differential scanning calorimeter (SII NanoTechnology, product name: High Sensitivity Differential Scanning Calorimeter X-DSC7000) in accordance with JIS K7121 at a heating rate of 10°C / min. The melting point of N1000A was measured to be 300°C.

[0164] The apparent shear viscosity of PA9T resin was measured using a flow tester (Shimadzu Corporation, product name: Shimadzu Flow Tester CFT-500D). Specifically, the PA9T resin was dried in a hot air dryer at 160°C for 12 hours, and then 1.5 cm of PA9T resin was dried. 3 The mixture was packed into a 360°C cylinder attached to a die (diameter: 1 mm, length: 10 mm), and a 1.0 cm2 cylinder was placed on top of the cylinder. 2 A plunger was attached, and when the temperature of the cylinder reached 360°C, it was preheated for 5 minutes, and immediately after this preheating, a load of 50 kgf was applied to melt and flow out the PA9T resin, and its apparent shear viscosity was measured.

[0165] After preparing the stirred mixture, this stirred mixture was supplied to the co-rotating twin-screw extruder equipped with a vacuum pump used in Example 1, melt-kneaded under reduced pressure, and extruded into a rod shape from the die at the tip of the co-rotating twin-screw extruder, cooled with water, and cut to prepare a pellet-shaped molding material. The stirred mixture was melt-kneaded under conditions of a cylinder temperature of 330°C to 360°C, an adapter temperature of 360°C, and a die temperature of 360°C. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was measured to be 363°C.

[0166] The prepared molding material was then placed in a dehumidifying hot air dryer heated to 160°C and dried for 12 hours or more. After confirming that the moisture content of the dried molding material was 300 ppm or less, the molding material was placed in a φ20 mm single-screw extruder equipped with a 150 mm wide T-die used in Example 1 and continuously extruded through the T-die to form a strip-shaped conductive resin film for a current collector. The moisture content of the molding material was confirmed by Karl Fischer titration using a trace moisture analyzer (manufactured by Mitsubishi Chemical Corporation, product name: CA-100). The single-screw extruder was the same as used in Example 1, with an L / D of 25, a compression ratio of 2.5, and a full-flight screw.

[0167] The temperature of the single-screw extruder was adjusted to 340°C to 360°C, the temperature of the T-die to 360°C, and the temperature of the connecting pipe connecting the single-screw extruder to the T-die to 360°C. The temperature of the molten molding material was measured from the resin temperature at the inlet of the T-die and was found to be 363°C. When the molding material was introduced into this single-screw extruder, nitrogen gas was supplied at a rate of 15 L / min.

[0168] After the conductive resin film for current collector was produced, the presence or absence of die buildup during production of the conductive resin film for current collector, and the thickness, specific gravity, relative crystallinity, chemical resistance, and conductivity of the conductive resin film for current collector were evaluated in the same manner as in Example 1, and the results are summarized in Table 5. When the conductive resin film for current collector was immersed in NMP and an electrolyte and then observed, it was found that the conductive resin film for current collector was deformed, and the conductivity could not be fully evaluated.

[0169] Comparative Example 7 To prepare the molding material, the polyarylene ether ketone resin was changed to a polyetherimide resin [polycondensate of 4,4'-[isopropylidenebis(p-phenyloxy)diphthalic dianhydride and m-phenylenediamine], manufactured by SABIC, product name: ULTEM 1010-1000-NB [product name manufactured by SABIC, (hereinafter abbreviated as "1010")]], and this polyetherimide resin (hereinafter abbreviated as PEI resin) was pulverized by the freeze-pulverization method.

[0170] To measure the melting point (also called melting temperature) of 1010, a differential scanning calorimeter (manufactured by SII Nanotechnology, product name: High Sensitivity Differential Scanning Calorimeter X-DSC7000) was used in accordance with JIS K7121 at a heating rate of 10°C / min, but no melting point was observed.

[0171] The apparent shear viscosity of the PEI resin was measured using a flow tester (Shimadzu Corporation, product name: Shimadzu Flow Tester CFT-500D). Specifically, the PEI resin was dried in a hot air dryer at 160°C for 12 hours, and then 1.5 cm of the PEI resin was dried. 3 The mixture was packed into a cylinder at 375°C attached to a die (diameter: 1 mm, length: 10 mm), and a 1.0 cm2 cylinder was placed on top of the cylinder. 2 A plunger was attached, and when the temperature of the cylinder reached 375°C, it was preheated for 5 minutes. Immediately after this preheating, a load of 50 kgf was applied to melt and flow out the PEI resin, and its apparent shear viscosity was measured.

[0172] After pulverizing the PEI resin, this PEI resin and the conductive material used in Example 1 were stirred and mixed in the mass ratio shown in Table 4 to prepare a stirred mixture. After preparing the stirred mixture in this manner, this stirred mixture was fed to the co-rotating twin-screw extruder equipped with a vacuum pump used in Example 1, melt-kneaded under reduced pressure, and extruded into a rod shape from the die at the tip of the co-rotating twin-screw extruder. The rod was water-cooled and cut to prepare a pellet-shaped molding material. The stirred mixture was melt-kneaded under conditions of a cylinder temperature of 350°C to 380°C, an adapter temperature of 380°C, and a die temperature of 360°C. The temperature during melt-kneading was measured by measuring the temperature of the molten molding material immediately after extrusion from the die, and was found to be 383°C.

[0173] The prepared molding material was then placed in a dehumidifying hot air dryer heated to 160°C and dried for 12 hours or more. After confirming that the moisture content of the dried molding material was 300 ppm or less, the molding material was placed in the φ20 mm single-screw extruder used in Example 1 and continuously extruded through a 150 mm wide T-die to form a strip-shaped conductive resin film for a current collector. The moisture content of the molding material was confirmed by Karl Fischer titration using a trace moisture analyzer (manufactured by Mitsubishi Chemical Corporation, product name: CA-100). The strip-shaped conductive resin film for a current collector was formed by continuously extruding through the 150 mm wide T-die.

[0174] The single-screw extruder was the same as that used in Example 1, with an L / D of 25, a compression ratio of 2.5, and a full-flight screw. The temperature of the single-screw extruder was adjusted to 350°C to 380°C, the temperature of the T-die to 360°C, the temperature of the connecting pipe connecting the single-screw extruder to the T-die to 380°C, and the gear pump to 380°C. The temperature of the molten molding material was measured from the resin temperature at the inlet of the T-die and was found to be 384°C. When the molding material was introduced into this single-screw extruder, nitrogen gas was supplied at a rate of 15 L / min.

[0175] After the conductive resin film for current collector was produced, the presence or absence of die buildup during production of the conductive resin film for current collector, and the thickness, specific gravity, chemical resistance, and conductivity of the conductive resin film for current collector were evaluated in the same manner as in Example 1, and the results are summarized in Table 5.

[0176] The melting point of the conductive resin film for the current collector could not be determined, so the relative crystallinity could not be calculated. Furthermore, when the conductive resin film for the current collector was immersed in NMP and an electrolyte, the conductive resin film for the current collector dissolved, raising doubts about its practical use.

[0177] [Table 5] [Industrial Applicability]

[0178] The conductive resin film for a current collector of a secondary battery and the method for producing the same according to the present invention are used in the field of producing various secondary batteries. [Explanation of symbols]

[0179] 1 Molding material 2 Polyarylene ether ketone resin 3. Conductive materials 4. Conductive resin film for current collectors 10 Melt kneader 12 cylinders 13 Screw 14 dice 20 Melt extrusion molding machine 23 Dice 26 Crimping roll 27 Cooling roll 28 Winder 29 Winding tube

Claims

1. A conductive resin film for a current collector having a relative crystallinity of 80% or more is formed from a molding material containing 100 parts by mass of a polyarylene ether ketone resin and 5 parts by mass or more and 35 parts by mass or less of a conductive material, the conductive material is composed of, in terms of composition mass ratio, 30% by mass or more and 99% by mass or less of carbon nanotubes and 1% by mass or more and 70% by mass or less of a conductive material other than carbon nanotubes; The conductive material other than carbon nanotubes is a metal-based or carbon-based conductive material, has a shape of either a polyhedron, a sphere, or an ellipsoid, and has an average particle diameter of 0.1 μm or more and 10.0 μm or less; The resistance value measured by applying a pressure of 1 MPa in the thickness direction of the conductive resin film for current collector is 1 mΩ cm ２ 800 mΩ・cm or more ２ A conductive resin film for a current collector of a secondary battery, characterized in that:

2. 2. The conductive resin film for a current collector of a secondary battery according to claim 1, which has a thickness of 10 μm or more and 500 μm or less, a specific gravity of 1.25 or more and 1.60 or less when measured in accordance with JIS K 7112 Method A, and a mass change rate of 2.0% or less when immersed in N-methyl-2-pyrrolidone and an electrolyte solution.

3. 3. The conductive resin film for a current collector of a secondary battery according to claim 1, wherein the polyarylene ether ketone resin is at least one of a polyether ether ketone resin and a polyether ketone ketone resin.

4. A method for producing the conductive resin film for a current collector of a secondary battery according to claim 1 or 2, comprising: a molding material containing 100 parts by mass of polyarylene ether ketone resin and 5 parts by mass or more and 35 parts by mass or less of a conductive material, the conductive material being composed of, in terms of composition mass ratio, 30% by mass or more and 99% by mass or less of carbon nanotubes and 1% by mass or more and 70% by mass or less of a conductive material other than carbon nanotubes; A method for producing a conductive resin film for a current collector of a secondary battery, comprising extruding a molding material through a die into a conductive resin film for a current collector, and then cooling the film by sandwiching the film between a pressure roll and a cooling roll, thereby making the relative crystallinity of the conductive resin film for a current collector 80% or more.

5. The cooled conductive resin film for a current collector is subjected to heat compression molding, and the heating temperature of the conductive resin film for a current collector is set to be equal to or higher than the melting point of the polyarylene ether ketone resin but lower than the thermal decomposition temperature, and a pressure of 0.5 kgf / cm is applied to the conductive resin film for a current collector relative to the projected area of ​​the conductive resin film for a current collector. ２ More than 100kgf / cm ２ The method for producing a conductive resin film for a current collector of a secondary battery according to claim 4, wherein the following is performed:

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