Metallized film for secondary battery positive electrode, and method for producing same

Abstract

Provided is a metallized film in which the contact resistance is lower than the surface resistance even if a conductive thin film layer is formed on the surface of a resin, the metallized film having excellent suitability for subsequent processes such as conveyance without breaking, and having excellent adhesion to a positive electrode active material. In this metallized film for a secondary battery positive electrode, an aluminum metal layer is formed on at least one surface of a resin film, and when the crystal orientation in the cross section of the aluminum metal layer is imaged by the ACOM-TEM method, the area of crystal regions exhibiting < 001 >, < 011 >, and < 111 > orientations is 75% or less of the total area.

Description

Technical Field

[0001] The present invention relates to a metallized film for a secondary battery and a method for manufacturing the same. Background Art

[0002] In recent years, the use of portable digital devices such as smartphones, tablet computers, mobile phones, notebook personal computers, digital cameras, digital video cameras, portable game consoles, portable devices such as power tools, electric motorcycles, and electric assisted bicycles, and the use of next-generation vehicles such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles, and the use of power generation using natural energy such as sunlight and wind power have become popular, and the demand for the use and storage of local electric energy has increased, and the necessity of batteries and storage systems has increased. Based on this background, the demand for storage elements such as batteries and capacitors has increased, and lithium-ion batteries have become widely popular.

[0003] Lithium-ion batteries generally have the following structure: a separator for secondary batteries and an electrolyte are inserted between a positive electrode formed by stacking a positive electrode active material on a positive electrode collector and a negative electrode formed by stacking a negative electrode active material on a negative electrode collector. In addition, due to the miniaturization of electrical and electronic equipment or the requirements for improved power consumption and extended cruising range of next-generation automobiles, there is a demand for miniaturization and lightness of storage batteries, as well as a high output density that can instantly charge / discharge large currents.

[0004] In order to improve the weight energy density, the battery mounted on the vehicle generally has the following structure: the positive electrode and the negative electrode are formed in a sheet shape, and the positive electrode and the negative electrode are wound or stacked in a housing with a separator also formed in a sheet shape interposed therebetween. The sheet-shaped electrode plate has the following structure: a mixture layer containing an active material is formed on the surface of a metal foil as a current collector.

[0005] In addition, one of the methods for obtaining high output density is to reduce the resistance of various materials constituting the battery (internal resistance of the battery). In the battery, aluminum foil is mostly used as the collector, but the collector usually formed by aluminum foil has an oxide film. It is generally believed that the internal resistance increases due to the oxide film formed on the aluminum surface. If the internal resistance increases, the voltage will decrease when charging / discharging with a large current, resulting in a decrease in the output of the battery. Usually, a strong natural oxide film with a thickness of 5nm to 10nm is formed on aluminum, which is usually an insulator, but the aluminum surface has the characteristic of maintaining good conductivity. It is believed that the reasons are: the statement that the current flows from the defective part of the oxide film; and according to the tunneling phenomenon in the field of quantum mechanics, particles will penetrate the area that cannot be crossed in terms of energy with a certain probability. When the electronic conductor is close to about 10nm or less, a tunneling effect of good electronic conduction will be generated. Although it is not clear, the aluminum oxide film itself will have a great influence on the internal resistance.

[0006] As a method for suppressing the increase in internal resistance caused by the oxide film and reducing the contact resistance between the electrode and the active material, there is a method of forming unevenness on the surface of the metal foil used in the electrode (for example, Patent Document 1). Although it is not clear whether the number of defects is increased by roughening the aluminum surface or the tunnel effect is easily manifested by forming a large number of protrusions, it is effective as a method for reducing contact resistance.

[0007] As a method for achieving miniaturization and lightweight and improving high output density, for the purpose of increasing volume energy density or increasing weight energy density, research is being conducted to make electrodes or electrode collectors thin films. However, if the metal foil used in the electrode is simply thin-filmed in order to cope with it, the problem of insufficient strength will arise. In addition, if the surface unevenness of the thin-filmed metal foil is increased for the purpose of reducing contact resistance, it will further become a cause of reduced strength of the metal foil, so it is not good. Therefore, as a new raw material to replace metal, it is proposed to make the following raw material, that is, a raw material having a structure in which a conductive film layer of a metal or the like is provided on the surface of a biaxially stretched polyester film having excellent mechanical properties or heat-resistant dimensional stability, have a collector function and use it as an electrode substrate (for example, Patent Document 2, Patent Document 3).

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent Application Publication No. 2008-160053

[0011] Patent Document 2: Japanese Patent Laid-Open No. 10-40919

[0012] Patent Document 3: Japanese Patent No. 6211796 Summary of the invention

[0013] Problems to be solved by the invention

[0014] However, in the metallized film having a structure of a conductive film layer of metal or the like formed on the surface of a resin film such as a polyester film, since the thickness of the metal layer is thinner than the metal foil used before, the resistance value of the metallized film, i.e., the surface resistance or contact resistance, will increase compared with the metal foil. On the other hand, as a prior art, it is known that there is a method for roughening the metal surface for the purpose of reducing the contact resistance of the metal surface such as aluminum, but the method for forming a conductive film layer of metal or the like on the surface of a resin film is usually a vacuum evaporation method, etc., and since the formed evaporated metal film is a thin film metal, it is extremely difficult to roughen it using methods such as etching. In addition, even if it is desired to roughen the surface of a resin film such as a polyester film in advance and then form an evaporation metal layer, the resin film is also easy to break, and in the vacuum evaporation method, or in the manufacturing process of applying a positive electrode active material to the metallized film and drying and pressing, etc., it becomes difficult to transport. Therefore, there are problems such as the temperature rise inside the battery due to resistance, or the use under the conditions of high output, rapid charge / discharge, etc. that cannot be tolerated.

[0015] The present invention is based on the above-mentioned facts, and aims to provide a metallized film which has a contact resistance lower than the surface resistance even when a conductive thin film layer is formed on the resin surface, has excellent suitability for subsequent steps such as being able to be transported without breaking, and has excellent adhesion to a positive electrode active material.

[0016] Technical means of solving problems

[0017] The inventors have made great efforts to study the above-mentioned problems, and found that by using a vacuum evaporation method to control the surface shape, crystal size or crystal orientation of the evaporation film, a metallized film with a contact resistance lower than the surface resistance and excellent adhesion to the electrode active material and a method for manufacturing the same are obtained. In addition, it is found that by using a positive electrode collector made of the metallized film, a storage element and a storage module with excellent rate characteristics and cycle characteristics can be obtained.

[0018] That is, the present invention relates to the following contents: a metallized film for a positive electrode of a secondary battery, characterized in that: an aluminum metal layer is formed on at least one surface of a resin film, and when the crystal orientation of a cross section of the aluminum metal layer is photographed using an automated crystal orientation mapping-transmission electron microscope (ACOM-TEM) method, the area of ​​the crystal region showing <001>, <011>, and <111> orientations is less than 75% of the whole;

[0019] According to the metallized film for a secondary battery positive electrode, the surface roughness Ra of the aluminum metal layer not in contact with the resin film is 15nm to 60nm;

[0020] According to the metallized film for a secondary battery positive electrode, the thickness of the aluminum metal layer is in the range of 0.5 μm to 3.0 μm;

[0021] According to the metallized film for a secondary battery positive electrode, when a line parallel to the outermost layer is drawn on the resin film side 300 nm from the top position of the outermost layer of the aluminum metal layer not in contact with the resin film, the average crystal size on the line is 300 nm or less;

[0022] According to the metallized film for a secondary battery positive electrode, the surface resistivity A (Ω / Y) and the contact resistance B (mΩ) of the aluminum metal layer surface measured by a four-terminal method are within the ranges of the following formulas.

[0023] 0.05≦B / (A×1000)≦0.5

[0024] In addition, the present invention relates to a method for manufacturing a metallized film for a secondary battery positive electrode, wherein the metallized film for a secondary battery positive electrode is manufactured, and the manufacturing method includes the following steps: a vacuum evaporation method, that is, a vacuum evaporation method in which argon gas is introduced when aluminum as an evaporation source is heated and vaporized by at least one selected from the group consisting of resistance heating, induction heating and electron beam, and the vaporized aluminum is vapor-deposited on a resin film to form a film.

[0025] In addition, the present invention relates to an electric storage element including the metallized film for a secondary battery positive electrode; and an electric storage module including the electric storage element.

[0026] Effects of the Invention

[0027] According to the present invention, by using a vacuum evaporation method to control the surface shape, crystal size or crystal orientation of the evaporation film, a metallized film having a contact resistance lower than the surface resistance and excellent adhesion to the electrode active material and a method for manufacturing the same can be obtained. In addition, by using a positive electrode collector made of the metallized film, a storage element and a storage module having excellent rate characteristics and cycle characteristics can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] [ Figure 1 ] is a schematic cross-sectional view of the metallized film of the present invention.

[0029] [ Figure 2 ] is a schematic cross-sectional view of the metallized film of the present invention.

[0030] [ Figure 3 ] is a schematic cross-sectional view of the metallized film of the present invention.

[0031] [ Figure 4 ] is a schematic diagram illustrating the definition of the outermost surface and top position of the aluminum metal layer in the present invention and its relationship with surface roughness.

[0032] [ Figure 5 ] is an electron microscope (SEM) photograph of the surface of an aluminum metal layer (film thickness 1.48 μm) when the grains are grown large and densely using an induction heating evaporation source using a carbon crucible.

[0033] [ Figure 6 ] is a SEM photograph of a cross-section of an aluminum metal layer (film thickness 1.48 μm) when the grains are grown large and densely using an induction heating evaporation source using a carbon crucible.

[0034] [ Figure 7 ] is a SEM photograph of the surface of an aluminum metal layer (film thickness 1.12 μm) grown by a boat heating method in which aluminum metal wires are continuously supplied to a resistance heating boat.

[0035] [ Figure 8 ] is a transmission electron microscope (TEM) photograph of a cross section of an aluminum metal layer (film thickness 1.06 μm) formed using an evaporation source using an induction heating method utilizing a carbon crucible.

[0036] [ Fig. 9 ] is a TEM photograph of a cross section of an aluminum metal layer (film thickness: 1.12 μm) formed by a boat heating method in which aluminum metal wire is continuously supplied to a resistance heating boat.

[0037] [ Fig.10 ] is a TEM photograph of a cross section of an aluminum metal layer (film thickness: 0.96 μm) formed by a boat heating method in which aluminum metal wire is continuously supplied to a resistance heating boat.

[0038] [ Fig.11 ] is a cross-sectional ACOM-TEM photograph of an aluminum metal layer (film thickness 1.06 μm) formed using an evaporation source using an induction heating method using a carbon crucible.

[0039] [ Fig.12 ] is a cross-sectional ACOM-TEM photograph of an aluminum metal layer (film thickness 1.12 μm) formed by a boat heating method in which aluminum metal wire is continuously supplied to a resistance heating boat.

[0040] [ Fig.13 ] is a cross-sectional ACOM-TEM photograph of an aluminum metal layer (film thickness: 0.96 μm) formed by a boat heating method in which aluminum metal wire is continuously supplied to a resistance heating boat.

[0041] [ Fig.14 ] is a color code diagram showing the crystal orientation of aluminum metal

[0042] [ Fig.15 ] is a diagram that provides supplementary explanation of the method of calculating the crystal size of aluminum metal based on cross-sectional photographs taken using the ACOM-TEM method. DETAILED DESCRIPTION

[0043] The present invention is described in detail below.

[0044] <Metalized Film>

[0045] The metallized film 4 for the secondary battery positive electrode of the present invention has an aluminum metal layer 3 ( Figure 1 , Figure 2 , Figure 3 ).

[0046] <Aluminum metal layer>

[0047] The aluminum metal layer 3 in the present invention is an aggregate of aluminum metals formed by laminating one or more layers containing aluminum as the main component. The main component means that the main component exceeds 80 atomic % when the entire layer is taken as 100 atomic %.

[0048] The thickness of the aluminum metal layer 3 in the present invention is preferably 0.5 μm to 3.0 μm, more preferably 0.7 μm to 2.5 μm. When the aluminum metal layer is formed on both surfaces of the resin film, the thickness of each layer preferably satisfies the above thickness.

[0049] In the case of secondary battery electrode applications, when the surface resistance and contact resistance are high, they become resistance inside the battery and cause heat generation, so the lower the resistance, the better. When the metallized film is coated with an active material and pressed to increase the packing density and used as a current collector, the surface resistance of the metal film is preferably 0.15Ω / Y or less, and more preferably 0.05Ω / Y or less, in terms of the surface resistance related to current diffusion and uniformity in the surface direction.

[0050] In addition, the contact resistance on the surface of the metal layer of the metallized film will affect the electron transfer between the metallized film and the active material layer formed on its surface. The contact resistance refers to the resistance value between the two copper plates when the aluminum metal layer 3 of the metallized film 4 is placed on a 10 mm thick NR (Natural Rubber) sponge rubber with the metallized film 4 facing upward, and two 25 mm × 25 mm gold-plated copper plates are separated by 1 mm and a 500 g weight is placed on each copper plate. In order to reduce the internal resistance increase, the metal film contact resistance is preferably less than 30 mΩ, and more preferably less than 20 mΩ.

[0051] On the other hand, in order to increase the volume energy density, it is necessary to make the metallized film thin film, and in order to increase the weight energy density, it is necessary to make the metallized film lightweight, so simply thickening the metal film is not good. If the resistance of the electrode is taken into account, the thickness of the aluminum metal layer is preferably 0.7 μm or more, and if it is 1.0 μm or more, it becomes a low resistance, which can reduce the increase in internal resistance. On the other hand, for the purpose of increasing the volume energy density and weight energy density, it is necessary to promote the thin film of the electrode substrate or reduce the use of heavy metals. Therefore, the thickness of the aluminum metal layer is preferably less than 3.0 μm, and more preferably less than 2.5 μm.

[0052] Usually, there is a correlation between the thickness of the metal film and the surface resistance and the contact resistance, and then there is a correlation between the surface resistance and the contact resistance. If the thickness of the metal film is increased, the surface resistance decreases, and the interface resistance also tends to decrease. In addition, the contact resistance value here is a value including the contact resistance of the two electrode areas of 25mm×25mm and the film resistance (surface resistance) between the two electrodes. Therefore, the ratio of the contact resistance value to the surface resistance value [contact resistance value] / [surface resistance value] can represent a value with less influence of the surface resistance. In addition, the smaller the value obtained by the following formula representing the ratio of the surface resistance A (Ω / Υ) to the contact resistance B (mΩ), the lower the contact resistance is compared with the surface resistance value or the film thickness of the metal film, that is, a low contact resistance is achieved by a thinner and lighter metal film. From the above point of view, the value obtained by the following formula is preferably less than 0.5, more preferably less than 0.4, and further preferably less than 0.3, and particularly preferably less than 0.2. On the other hand, the lower limit of the value obtained by the following formula is not particularly limited, and is preferably more than 0.05.

[0053] Formula: (contact resistance B) / (surface resistance A×1000)

[0054] The inventors and others have conducted intensive research on the aluminum metal layer 3 in the present invention. As a result, through the structure and crystal growth control of the aluminum metal layer described below, they have successfully formed an aluminum metal layer on the resin film that has excellent resistance characteristics and shows excellent contact resistance characteristics compared to the surface resistance and metal film thickness. Therefore, a thinner, lighter, and metallized film for the positive electrode of a secondary battery with excellent resistance characteristics can be obtained.

[0055] Specifically, when the aluminum metal layer is formed by vacuum evaporation, the orientation of the aluminum crystals is controlled in a non-uniform manner, and the crystal growth of the metal film is controlled without extreme bias toward a specific crystal orientation, and the crystals oriented <001>, <011>, and <111> exist in a mixed ratio after appropriate balance. In addition, the resistance characteristics are achieved by growing aluminum crystals of controlled crystal size on the outermost surface of the aluminum metal layer and increasing the surface unevenness, and the close contact with the active material layer formed by coating and pressing in the subsequent processing, the transportability in the roll-to-roll structure, or the damage resistance is also taken into account, thereby preventing the surface of the aluminum metal layer from becoming sparse when the aluminum crystals are grown to the outermost surface of the metal film. By forming the aluminum metal layer 3 in this way, it has the characteristic of reducing the contact resistance compared to the surface resistance.

[0056] In order to realize the structure of the aluminum metal layer 3 that controls the crystal growth of the metal film to reduce the contact resistance, the orientation and crystal size of the aluminum crystals in the aluminum metal layer are focused on, and the ACOM (Automated Crystal Orientation Mapping)-TEM method is used for research. The ACOM-TEM method is a method for analyzing the orientation distribution of crystalline samples using electron diffraction of TEM. By measuring the electron diffraction pattern of each point while scanning the electron beam probe, high spatial resolution crystal information can be obtained. Compared with methods such as the Scanning Electron Microscope-Electron Backscatter Diffraction Pattern (Scanning Electron Microscope-Electron Backscatter Diffraction Pattern, SEM-EBSD) method, the method can obtain information on smaller grains, so it is believed that it can be suitably used for the structure and orientation analysis of thin crystalline films such as the aluminum metal layer in the present invention, and research has been carried out. The analysis of the aluminum metal layer using the ACOM-TEM method and the outline of the analysis sequence are as follows.

[0057] First, a special pre-treatment technique such as the focused ion beam (FIB) method is used to prepare an extremely thin slice sample for observing the cross section of the aluminum metal layer from a sample of the positive electrode metallized film. Next, a TEM image is observed for the prepared extremely thin slice sample, and then the crystal orientation, orientation, and size are grasped using the ACOM-TEM method. Regarding the crystal orientation analysis, the aluminum crystals in the observation and imaging field of view can be classified into representative orientations of aluminum, namely <001>, <011>, and <111>, and are distinguished and displayed by color. Furthermore, for the obtained crystal orientation map, aluminum crystals showing an orientation with an orientation axis offset of less than 30° are regarded as the same orientation and classified as any one of the three, thereby calculating the existence ratio of aluminum crystals of each orientation.

[0058] The preferred form of the metallized film for the secondary battery positive electrode of the present invention is as follows: with respect to the <001>, <011>, and <111> orientations of the aluminum of the aluminum metal layer 3, there is no extreme bias toward any one of the orientations, and even if aluminum crystals with different crystal orientations and orientation axes grow, they have dense contacts and form a film. Specifically, an aluminum metal layer is formed on at least one surface of the resin film, and when the crystal orientation of the cross section of the aluminum metal layer is photographed using the ACOM-TEM method, the area of ​​the crystal region showing the <001>, <011>, and <111> orientations is less than 70% of the total in any orientation, and more preferably less than 65% in any orientation.

[0059] For reference only, since aluminum is a cubic system, when aluminum is in powder form, the crystal orientation is random, so the <111> oriented crystals are most abundant. On the other hand, rolled aluminum foil, which is also widely used in the positive electrode of secondary batteries, becomes dense through the rolling process, and the crystal orientation is consistent, so the <111> orientation in the oblique direction becomes weak, and the existence rate of <011> oriented crystals becomes extremely high.

[0060] As a feature of the surface of the aluminum metal layer 3 that controls the crystal growth of the aluminum metal of the metal film to reduce the contact resistance, improve the processing suitability, and improve the close contact with the active material layer, the surface roughness Ra of the surface of the aluminum metal layer 3 that is not in contact with the resin film 1 is preferably 15nm or more and 60nm or less, and further preferably 20nm or more and 55nm or less. When the aluminum surface is fully roughened and the height of the convex and concave portions ensures a certain degree of size, the contact resistance tends to be lower, and the larger the surface roughness Ra, the more preferred the tendency. Among them, if the surface roughness Ra is too large, the aluminum density near the outermost surface of the thin aluminum metal layer 3 becomes sparse, and the crystal grain boundaries also become relatively large. Therefore, when a stress load is applied to the metal film during transportation, etc., it may become the cause of the metal film fracture, so it is preferably less than 60nm.

[0061] In addition, the resistance characteristics are achieved by growing aluminum crystals of controlled crystal size on the outermost surface side of the aluminum metal layer and setting the surface irregularities to the preferred surface roughness range, while also taking into account the close contact with the active material layer formed by coating and pressing in subsequent processing, the transportability in the roll-to-roll process, or the damage resistance to prevent the reduction of resistance characteristics due to damage. Therefore, when the aluminum crystals are grown from the resin film side to the outermost surface side of the aluminum metal layer, the grain size near the outermost surface of the aluminum metal layer becomes too large and becomes sparse, so the aluminum crystal size can be controlled in the thickness direction of the aluminum metal layer, and aluminum crystals with slightly smaller grain sizes can be densely present on the surface side. Specifically, when a straight line parallel to the average line is drawn from the top position of the outermost surface of the aluminum metal layer toward the inner side of the film at 300 nm, the average crystal size on the line is preferably less than 300 nm. Figure 4 As shown, the so-called outermost surface is the surface roughness curve of the aluminum metal layer, the so-called top position is the highest position in the surface roughness curve, and the average line is defined as the average line of the surface roughness curve shown in Japanese Industrial Standards (JIS) B0601 (2013 edition).

[0062] As a method for controlling the crystal structure, orientation, and outermost surface structure of the aluminum metal layer 3, by increasing the surface temperature of the substrate, i.e., the resin film, during vapor deposition, the columnar crystals are large and dense, and are not biased towards one orientation, and three types of oriented aluminum crystals are mixed, thereby achieving the formation of a dense film.

[0063] Among them, when the substrate is a resin film, if the substrate temperature is increased, it will melt and break. Therefore, if a method is not devised for production, the substrate temperature cannot be increased, and the aluminum metal layered film produced by vacuum evaporation will become a columnar crystalline film with large gaps between metal particles.

[0064] In the present invention, even if the substrate is a resin film, by introducing argon gas while increasing the surface temperature of the substrate and controlling the vacuum degree during evaporation to an appropriate range, the columnar crystals of the aluminum metal layer are successfully grown large and dense, the grain size is increased, and when a straight line parallel to the outermost layer is drawn from the outermost surface of the aluminum metal layer toward the inner side of the film at a distance of 300 nm, the average crystal size on the line is less than 300 nm, thereby controlling the crystal size and density of the inner part (substrate film side) and the surface layer of the aluminum metal layer. By forming the aluminum metal layer in this way, appropriate concavities and convexities are successfully formed on the surface of the aluminum metal layer. By increasing the heat generated by the evaporation source while forcibly cooling the resin film from the back, it is possible to increase the temperature only near the surface of the resin film exposed to the evaporation source, and make the columnar crystals large and dense. In addition, the vacuum degree during evaporation is preferably controlled to 9.0×10 -3 Pa or more and 2×10 -2 Pa or less, and preferably controlled to 9.0×10 -3 Pa or more and 1×10 -2 The range is below Pa.

[0065] In the case of a general aluminum vacuum deposition method for forming a relatively thin aluminum metal layer such as an aluminum vapor-deposited gas barrier film for food packaging, a boat heating method is used in which aluminum metal wire is continuously supplied to a resistance-heated boat. However, if the aluminum metal layer is formed by the above method, the orientation of the aluminum crystals tends to be <111>.

[0066] In addition, in order to make the surface temperature of the substrate rise easily, it is preferred to increase the calorific value of the evaporation source as much as possible and form the film in a short time. From the above point of view, it is preferred to use an evaporation source with a large calorific value, such as an induction heating method using a carbon crucible, or a method of heating using an electron beam, thereby increasing the calorific value of the evaporation source and making the grains grow large and dense. Wherein, in the above state, the resin film will melt due to heat, so it is preferred to force the resin film to be cooled from the back to a temperature just before it is about to become non-melting, thereby making the columnar crystals of the aluminum metal layer grow large and dense. From the point of view of the thermal influence on the resin film, it is preferred to use a boat-type resistance heating evaporation. Furthermore, by introducing argon gas during evaporation, it is possible to further form concave and convex on the surface of the aluminum metal layer.

[0067] Figure 5 and Figure 6 The SEM photographs of the surface and cross-section of an aluminum metal layer when large and dense grains are grown on a resin film (polyethylene terephthalate (PET) film) having a surface roughness Ra of 38 nm using an evaporation source using an induction heating method using a carbon crucible with high heat generation. Figure 5 This is a surface SEM photo of an aluminum metal layer with a thickness of 1.48 μm. Figure 6 This is a cross-sectional SEM photograph of an aluminum metal layer with a thickness of 1.48 μm. Figure 5 and Figure 6 , it can be determined that by increasing the grain size, appropriate concavity and convexity can be formed on the surface of the aluminum metal layer. The surface roughness Ra at this time is Figure 5 In addition, according to Figure 6 From the cross-sectional SEM photo, it can be determined that the aluminum metal layer is a columnar crystal, and the convex and concave portion on the surface of the aluminum metal layer is equivalent to a columnar crystal. It can be inferred that the larger the size of the convex and concave portion on the surface of the aluminum metal layer, the larger and denser the columnar crystal.

[0068] on the other hand, Figure 7 , Figure 8 This is a SEM photograph of the surface of an aluminum metal layer grown by a boat heating method in which aluminum metal wires are continuously supplied to a resistance heating boat. Figure 7 The result of the introduction of argon gas found in the present invention, the precise control of the vacuum degree and the control of the growth of aluminum crystals in the aluminum metal layer with a thickness of 1.02 μm is obtained. As shown in the surface SEM photo, appropriate concavities and convexities can be formed, and the surface roughness Ra at this time is 34 nm. In order to increase the crystal grains and make a dense metal film, it is necessary to expose to a certain degree of time under the evaporation source as a heat source, and as a result, the evaporation time needs to be extended. The thickness of the aluminum metal layer is preferably 0.5 μm or more, and it is more preferably 0.7 μm or more, and it is particularly preferably 1.0 μm or more.

[0069] <Method for producing aluminum metal layer>

[0070] As a film forming method of the aluminum metal layer 3, for the purpose of making a thin electrode, a vacuum evaporation method that can form a metal film on a thin resin film without using an adhesive is preferred. Vacuum evaporation methods include induction heating evaporation method, resistance heating evaporation method, laser beam evaporation method, electron beam evaporation method, etc., among which induction heating evaporation method, resistance heating evaporation method, and electron beam evaporation method with a large calorific value of the evaporation source can be appropriately used. It is necessary to increase the calorific value of the evaporation source until the grains of the aluminum metal layer 3 are formed large and densely, and the surface temperature of the substrate needs to be sufficiently high, but because it is difficult to measure, the physical properties required for the aluminum metal layer 3 after evaporation are confirmed to determine whether it is sufficient heat.

[0071] In the aluminum metal layer 3, when the crystal orientation of the aluminum metal layer cross section is photographed by the ACOM-TEM method, the area of ​​the crystal region showing <001>, <011>, and <111> orientation is preferably less than 75% of the whole. The surface roughness Ra of the aluminum metal layer surface not in contact with the resin film is preferably 20nm to 60nm, the thickness of the aluminum metal layer is preferably in the range of 0.5μm to 3.0μm, and when a line parallel to the average line is drawn on the resin film side 300nm away from the top position of the outermost surface of the aluminum metal layer not in contact with the resin film, the average crystal size on the line is preferably less than 300nm. Among them, if the heat generation of the evaporation source is increased to the required heat, the temperature of the resin film may rise and melt in the management of the cooling function of the usual vacuum evaporation method. Therefore, in order not to excessively increase the temperature during evaporation, it is necessary to manage the cooling function in a manner that can uniformly cool the film while performing evaporation. Specifically, it is necessary to use a cooling mechanism including a metal plate or a metal roller that is fully cooled by a refrigerant to uniformly cool from the back of the evaporation surface. In order to perform cooling uniformly, the resin film and the cooling mechanism must be in close contact with each other without any gap.

[0072] For example, if the metal roller of the cooling mechanism is damaged, the damaged portion becomes a gap, and the resin film cannot be cooled and melts in the damaged portion. For example, if foreign matter enters the resin film and the metal roller of the cooling mechanism, the resin film cannot be cooled and melts due to the foreign matter. If the calorific value of the evaporation source is increased to the required heat, the damage to the metal roller or the mixing of foreign matter allowed in the usual vacuum evaporation method will become a problem, so it is necessary to more strictly manage the damage to the metal roller or the mixing of foreign matter. By increasing the heat generation of these evaporation sources and strengthening the management of the cooling function, the grains of the aluminum metal layer 3 can be grown large and densely formed, thereby reducing the internal resistance including the contact resistance. In particular, in the case of electron beam evaporation and laser beam evaporation, the calorific value of the evaporation source can be further increased by using an alumina crucible with better heat preservation than a carbon crucible as the evaporation crucible, so it is more preferred.

[0073] In addition, the vacuum degree during metal deposition is preferably 9.0×10 -3 Pa or more and 1×10 -2 Pa or less. In the present invention, the surface roughness is set to a preferred range, but the size of the surface roughness of the metal film by vacuum evaporation is greatly affected by the temperature of the substrate and the vacuum degree of the evaporation object. In the present invention, the temperature of the resin film 1 is increased to the limit, and the vacuum degree is set to 9.0×10 -3 Pa or more and 1×10 -2 Specifically, by introducing argon gas while exhausting the vacuum pump, a vacuum degree of 9.0×10 -3 In order to maintain the deposition rate of the metal film, the argon gas was adjusted so as not to add too much and maintain 1×10 -2 Below Pa.

[0074] <Resin film>

[0075] The resin film 1 used in the present invention is preferably a resin film formed by molding a polymer such as a synthetic resin into a thin film. In addition, it is preferably a resin that does not react with the electrolyte used in a secondary battery such as a lithium ion battery and has tolerance. As a resin film that can be suitably used in the present invention, for example, a polyester film can be exemplified, and a polyethylene terephthalate film or a polyethylene naphthalate film, or a polyimide film, a polyphenylene sulfide film, and a polypropylene film can also be exemplified in the polyester film. Among them, a polyethylene terephthalate film can be more preferably used. These resin films can be used alone, or a composite resin film can be used. In addition, it can also be used in a film coated with a resin or an adhesive on the surface of the resin film. In addition, from the viewpoints of mechanical properties or thermal dimensional stability of the resin film, the resin film is preferably a biaxially stretched film stretched biaxially. In a uniaxially stretched film or an unstretched film, the size changes due to insufficient thermal dimensional stability or insufficient mechanical properties, which becomes a cause of reduced safety of the secondary battery or deviation in battery capacity, and is therefore not good.

[0076] The thickness of the resin film 1 is preferably 1 μm or more and 20 μm or less, more preferably 3 μm or more and 10 μm or less, and particularly preferably 4 μm or more and 8 μm or less. In order to thin the electrode substrate, and further miniaturize, lighten, and increase the energy density of the storage element and the storage module using the storage element, the thickness of the resin film is more preferably thin, preferably 20 μm or less, more preferably 10 μm or less, and particularly preferably 8 μm or less. If it is too thin, the yield may be reduced due to breakage in the manufacturing process, and it is preferably 1 μm or more, more preferably 3 μm or more, and particularly preferably 4 μm or more.

[0077] The surface roughness Ra of the resin film can be arbitrary, but when the smoothness is extremely high, there is a situation where the transportability, coiling or adhesion of the aluminum metal layer is deteriorated, and adhesion occurs after coiling. On the other hand, on the contrary, when the surface roughness Ra is very large, although the sliding property or process suitability are excellent, when the aluminum metal layer is formed, the aluminum metal layer becomes sparse, cracks are easily generated, and the adhesion of the aluminum metal layer is deteriorated, which is still not good. Therefore, the surface roughness Ra of the resin film surface is preferably more than 10nm and less than 60nm. As a resin film, it is preferred to form the minimum concave-convex required for transport, and it is as smooth as possible, so the surface roughness Ra is preferably less than 60nm, and further preferably less than 50nm.

[0078] <Anchor layer>

[0079] The metallized film 4 for the secondary battery positive electrode of the present invention may also have an anchor layer 2 between the resin film and the aluminum metal layer 3. By providing the anchor layer 2, it is expected that the adhesion between the resin film and the aluminum metal layer will be improved. As the anchor layer 2, it is preferred to form a metal layer on the resin film by sputtering. In the sputtering method, the thickness of the anchor layer can be made thinner, which is most suitable for storage battery applications that require further thin filming.

[0080] As the anchor layer 2, it is preferred that the anchor layer 2 includes one or more metal layers selected from the group consisting of aluminum, nickel, titanium, nickel-chromium alloy (nichrome) and chromium, and it is further preferred that the anchor layer 2 is an aluminum metal layer formed by sputtering. At this time, it should be noted that it is important to maintain a state in which the metal surface of aluminum, nickel, titanium, chromium, nickel-chromium alloy, etc. selected as the anchor layer 2 is not oxidized while forming the aluminum layer thereon. Specifically, it is important to form the aluminum metal layer 3 while maintaining a vacuum state without opening it to the atmosphere after forming the metal layer as the anchor layer 2 by sputtering. If the metal surface of aluminum, nickel, titanium, chromium, nickel-chromium alloy, etc. selected as the anchor layer 2 is oxidized, a stable metal oxide film is formed, and it is difficult to perform metal bonding with the interface of the aluminum metal layer 3 formed thereon, and the close contact force cannot be ensured, and the aluminum metal layer 3 sometimes peels off from the anchor layer 2. Therefore, it is important not to oxidize aluminum, nickel, titanium, chromium, nickel-chromium alloy, etc. selected as the anchor layer 2. When the anchor layer 2 is an aluminum metal layer formed by sputtering, vacuum-depositing the aluminum metal layer 3 thereon causes the columnar crystals to grow larger and denser, thereby further suppressing the contact resistance of the aluminum metal layer, which is preferred.

[0081] The thickness of the anchor layer 2 is preferably 3 nm or more and 40 nm or less, more preferably 5 nm or more and 20 nm or less. If the thickness is less than 3 nm, sufficient adhesion may not be obtained. On the other hand, even if the anchor layer is increased from 40 nm, the adhesion improvement effect will not be increased, so it is preferably 40 nm or less. In the case of preparing the anchor layer by sputtering method with slow film forming speed, it is further preferred to set the anchor layer to 20 nm or less to improve productivity.

[0082] <Electrical storage element>

[0083] The electric storage element of the present invention comprises an electrode assembly and a battery case accommodating the electrode assembly. The electrode assembly comprises a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

[0084] Examples of such an electric storage element include a primary battery, a secondary battery, an electric double layer capacitor, and an aluminum electrolytic capacitor. However, in the present invention, the electric storage element refers to a secondary battery.

[0085] Examples of the secondary battery include lithium secondary batteries, lead storage batteries, nickel-cadmium batteries, nickel-hydrogen batteries, nickel-iron storage batteries, silver oxide-zinc storage batteries, manganese dioxide-lithium secondary batteries, lithium cobaltate-carbonate secondary batteries, and vanadium-lithium secondary batteries.

[0086] Among these, secondary batteries are preferred from the viewpoint of long-term use, and lithium secondary batteries that achieve high energy density by using an organic solvent are more preferred.

[0087] As the battery case, for example, an aluminum case, an iron case whose inner surface is nickel-plated, a case including an aluminum laminate film, or the like can be used.

[0088] The shape of the battery case includes a pouch type, a cylinder type, a square type, a coin type, etc. Among these, the pouch type is preferred because it can achieve high energy density and can freely design the shape at low cost.

[0089] The positive electrode is a positive electrode obtained by laminating a positive electrode material including an active material, a binder resin, and a conductive auxiliary agent on a current collector. In the present invention, it is preferred to use a current collector.

[0090] Examples of active materials include LiCoO 2 、LiNiO 2 、Li(NiCoMn)O 2 Lithium-containing transition metal oxides with iso-layered structures, LiMn 2 O 4 Spinel manganese oxides, and LiFePO 4 Iron compounds, etc.

[0091] As the binder resin, any resin having high oxidation resistance may be used, and specific examples thereof include fluorine-containing resins, acrylic resins, and styrene-butadiene resins.

[0092] Examples of the conductive aid include carbon materials such as carbon black and graphite.

[0093] As the positive electrode current collector, metal foil is suitable, and aluminum foil is particularly preferably used.

[0094] The negative electrode is a negative electrode in which a negative electrode material including an active material and a binder resin is stacked on a current collector.

[0095] Examples of active materials include carbon materials such as artificial graphite, natural graphite, hard carbon, and soft carbon, lithium alloy materials such as tin and silicon, metal materials such as lithium, and lithium titanate (Li 4 Ti 5 O 12 )wait.

[0096] Examples of the binder resin include fluorine-containing resins, acrylic resins, and styrene-butadiene resins.

[0097] As the negative electrode current collector, metal foil is suitable, and copper foil is particularly preferably used.

[0098] The electric storage device of the present invention preferably contains an electrolyte solution. The electrolyte solution is a place where ions migrate between the positive electrode and the negative electrode in an electrochemical device such as a secondary battery, and has a structure in which an electrolyte is dissolved in an organic solvent.

[0099] As the electrolyte, LiPF 6 , LiBF 4 and LiClO 4 From the viewpoint of solubility in organic solvents and ionic conductivity, LiPF 6 .

[0100] Examples of the organic solvent include ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Two or more of these organic solvents may be used in combination.

[0101] Hereinafter, a method for producing a lithium secondary battery which is also preferably used as an electric storage element will be described.

[0102] As a method for making a lithium secondary battery, an active material and a conductive aid are first dispersed in a binder resin solution to prepare an electrode coating liquid, the coating liquid is applied to a collector, and the solvent is dried to obtain a positive electrode and a negative electrode, respectively. The film thickness of the dried coating film is preferably set to be 50 μm or more and 500 μm or less. Furthermore, it is preferred that a method such as a roll pressing method is used to apply pressure to the active material layer formed on the collector to densify it, thereby thinning the collector.

[0103] A separator for a lithium secondary battery is arranged between the obtained positive electrode and negative electrode in contact with the active material layer of each electrode, and sealed in an outer packaging material such as an aluminum laminate film. After injecting an electrolyte, a negative electrode lead or a safety valve is provided, and the outer packaging material is sealed.

[0104] The lithium secondary battery obtained in this way has high adhesion to electrodes and excellent battery characteristics, and can be produced at low cost.

[0105] <Electricity Storage Module>

[0106] The storage element manufactured by the above method is sometimes used as a storage module by connecting a plurality of storage elements in series to meet the application of the storage element or the required battery capacity. In such a case, the storage elements are connected to each other by tab lead wires (current extraction wires) and housed in a resin or metal module case, thereby being used as a storage module.

[0107] Example

[0108] Hereinafter, the present invention will be described based on the embodiments. In addition, the present invention is not limited to these embodiments, and these embodiments can be deformed and changed based on the spirit of the present invention, and these are not excluded from the scope of the invention.

[0109] (Magnetron Sputtering)

[0110] The resin film was placed in a batch vacuum deposition apparatus (EBH-800 manufactured by Ulvac) using a target of 50 mm × 550 mm in size and the vacuum level was adjusted to 5 × 10 -1 Pa or less, and a direct current (DC) power supply is continuously applied for a time period to achieve a predetermined metal film thickness.

[0111] Alternatively, a resin film was placed in a roll vacuum deposition apparatus (EWC-060 manufactured by Ulvac), a target size of 70 mm × 550 mm was used, and the vacuum degree was adjusted to 1 × 10 -2 Pa or less, a pulse power supply is applied to form a metal layer.

[0112] In addition, unless otherwise specified, sputtering and vacuum evaporation are continuously performed so that the anchor layer and the aluminum metal layer are not exposed to the atmosphere.

[0113] (Vacuum deposition)

[0114] A resin film was placed in a batch vacuum deposition apparatus (EBH-800 manufactured by Ulvac), aluminum was placed on a deposition boat in an amount to achieve a target thickness, and then vacuum was evacuated until the vacuum reached a degree of 9.0 × 10 -3 Pa or less, and then the deposition boat is heated to perform vacuum deposition to form an aluminum metal layer.

[0115] Alternatively, a resin film is set in a roller vacuum evaporation device (EWC-060 manufactured by Ulvac), and the aluminum ingot is heated by an induction heating evaporation method using a carbon crucible at a conveying speed and output conditions at which the thickness of the aluminum metal layer becomes a specified value, thereby performing vacuum evaporation to form an aluminum metal layer.

[0116] Alternatively, a resin film is placed in a roll vacuum deposition apparatus (EWC-060 manufactured by Ulvac), and an aluminum wire is introduced into a deposition boat heated by resistance heating at a conveying speed at which the thickness of the aluminum metal layer becomes a predetermined value, thereby performing vacuum deposition to form an aluminum metal layer.

[0117] In addition, no matter which method is used, from the perspective of productivity, resistance characteristics, color and quality, it is preferred to form the desired aluminum metal layer thickness through a single vapor deposition (the entire set of operations of unwinding, vapor deposition, and winding is defined as a single vapor deposition). For example, a thin film vapor deposition of a 50nm thick aluminum vapor deposition layer formed by a single vapor deposition can be repeated 20 times (the entire set of operations is repeated 20 times) to form an aluminum metal layer with a total thickness of 1μm.

[0118] (About the introduction of argon gas)

[0119] The argon gas introduced during magnetron sputtering was used. Since sputtering and vacuum deposition were not performed simultaneously in a batch vacuum deposition apparatus (EBH-800 manufactured by Ulvac), argon gas was not introduced during vacuum deposition.

[0120] Since sputtering and vacuum deposition are continuously processed in a roll vacuum deposition apparatus (EWC-060 manufactured by Ulvac), sputtering and vacuum deposition are simultaneously performed in the same deposition chamber, and argon gas is always introduced into the deposition source of vacuum deposition.

[0121] (Processing of metallized film for secondary battery positive electrode into positive electrode for secondary battery)

[0122] LiCoO 2 ) was added with acetylene black graphite and polyvinylidene fluoride, dispersed in N-methyl-2-pyrrolidone and made into slurry. The slurry was evenly coated on one side or both sides of the metallized film for the positive electrode of the secondary battery of the embodiment or the comparative example, and then dried to form a positive electrode composite layer. Thereafter, compression molding was performed using a roll press to produce a positive electrode layer with a density of 3.6 g / cm2 without the collector. 3 The positive electrode strip.

[0123] (Aluminum crystal analysis using ACOM-TEM method)

[0124] It is a method for analyzing the orientation distribution of crystalline samples by electron diffraction of TEM. By measuring the electron diffraction pattern of each point while scanning the electron beam probe, high spatial resolution crystal information can be obtained. If the method is used, the method can obtain information on smaller grains than other methods such as SEM-EBSD. First, an extremely thin section for cross-section observation is collected from the measured sample using the FIB method (Foucused Ion Beam method, using equipment: Helios G4 manufactured by Thermo Fisher Scientific, Inc.).

[0125] Next, the ultra-thin slices (cross sections) collected by the pretreatment method were photographed using an atomic resolution analysis electron microscope (JEM-ARM200F manufactured by JEOL) for TEM observation. Furthermore, for the purpose of analyzing the crystal size and orientation, the aluminum metal layer was analyzed using ASTAR manufactured by Nanomeans, and the ACOM-TEM analysis image was obtained using analysis software (OIM Analysis ver. 8 manufactured by EDAX-TSL solution).

[0126] (Aluminum crystal size analysis using ACOM-TEM method)

[0127] Regarding crystal size analysis, using the ACOM-TEM analysis image taken using the method, a line parallel to the outermost layer is drawn on the resin film side 300nm away from the top position of the outermost layer of the aluminum metal layer, and then the sum of the sizes (nm) of all aluminum crystals on the line is divided by the number of crystals to estimate the average crystal size.

[0128] (Contact resistance measurement)

[0129] A metallized film was placed on a 10 mm thick NR sponge rubber (NRS-06 manufactured by Waki ​​Industry Co., Ltd.) with the metal film facing upward, and two 25 mm × 25 mm gold-plated copper plates were separated by 1 mm and a 500 g weight was placed on each copper plate. The resistance value between the two copper plates was measured using a resistance meter RM3544 manufactured by Hioki Electric Co., Ltd. and was set as the contact resistance.

[0130] (Surface resistance measurement)

[0131] The metallized film was cut into a size of about 300 mm x about 80 mm, and the surface resistance of three locations was measured by a four-terminal method using a simple low resistivity meter ("Loresta" (registered trademark) EP MCP-T360 manufactured by Mitsubishi Chemical Analytech Co., Ltd.), and the average value was used as the surface resistance value.

[0132] (Aluminum metal layer thickness)

[0133] An ultra-thin section for cross-sectional observation was collected from the metallized film sample by the FIB method. Next, an atomic resolution analysis electron microscope (JEM-ARM200F manufactured by JEOL) was used to take a TEM observation image of the ultra-thin section (cross-section) collected by the pretreatment method, and the distance between the resin film surface and the outermost surface of the aluminum metal layer was measured based on the observation image to calculate the thickness of the aluminum metal layer.

[0134] (Surface roughness Ra)

[0135] The surface roughness Ra was measured using a scanning white interference microscope manufactured by Hitachi High-Tech Science Co., Ltd. The surface roughness Ra was measured under the measurement conditions of the measurement mode "wave", the light source was 530 white (White), and the objective lens was 50 times, and the attached analysis software was used to calculate the surface correction under the conditions of 4 times, the supplementation was "complete", and the Gaussian filter was "cutoff 2μm".

[0136] (Evaluation of adhesion between resin film and aluminum metal layer)

[0137] A paper adhesive tape (NITTO, No. 720) with a width of 18 mm was attached to the surface of the aluminum metal layer, and then, when the paper adhesive tape was peeled off, it was judged whether the vapor-deposited film peeled off from the resin film. The case where the vapor-deposited film peeled off from the resin film was set as × (unqualified), and the case where there was no peeling was set as ○ (qualified), and it was used as a benchmark for whether it can be used as a metallized film for a secondary battery positive electrode.

[0138] (Evaluation of Adhesion Strength between Aluminum Metal Layer and Positive Electrode Active Material Layer)

[0139] For the surface coated with the positive electrode active material and pressed, use a 1.5cm×8cm double-sided tape (NITTO, No. 5000NS) to evenly adhere to the stainless steel plate while pressing with a hand roller. Afterwards, use the Tensilon universal testing machine RTG-1210 manufactured by AND to peel off the sample at a speed of 200mm / min in a direction 90 degrees relative to the stainless steel plate to implement a peeling test. It is judged based on whether the positive electrode active material peels off from the aluminum metal layer during peeling. The case where the positive electrode active material peels off from the aluminum metal film is set to × (unqualified), and the case where there is no peeling is set to ○

[0140] (Pass), and used as a criterion for whether it can be used as a positive electrode for a secondary battery].

[0141] (Evaluation of suitability for use)

[0142] On both sides of the metallized film for the positive electrode of the secondary battery obtained by the method, on the aluminum metal layer not in contact with the resin film, the positive electrode active material is continuously coated by the method described in the embodiment, and after heating and drying, it is calendered and pressed to form a positive electrode collector. During the processing, carefully observe whether coating rejection (defects), wrinkles, breaks, poor sliding, etc. occur during the conveying or winding process. If these defects do not occur, it is judged as suitability for use ○, and if these defects occur, it is judged as suitability for use ×.

[0143] (Example 1)

[0144] As the resin film, a biaxially oriented polyethylene terephthalate film with a thickness of 5.7 μm ("Lumirror" (registered trademark), model: F53, manufactured by Toray Co., Ltd.) was used. The average surface roughness Ra of the resin film was 38 nm. The roll-shaped original blank of the resin film was placed in a roller vacuum deposition device (EWC-060 manufactured by Ulvac), and a pulse power supply was applied to deposit aluminum with a thickness of 5 nm by sputtering. As a condition, the sputtering output was 2.0 kW using a pulse power supply. Thereafter, the aluminum ingot was heated by an induction heating deposition method using a carbon crucible, thereby vacuum depositing an aluminum metal layer with a thickness of 1.48 μm by a vacuum deposition method.

[0145] ACOM-TEM analysis of the aluminum metal layer of the metallized film produced in this way showed that the existence ratio of <001> oriented crystals was 0.184, the existence ratio of <011> oriented crystals was 0.221, the existence ratio of <111> oriented crystals was 0.595, and the surface roughness Ra of the surface of the aluminum metal layer not in contact with the resin film was 52 nm.

[0146] The surface resistance value (A) of the aluminum metal layer of the metal film that is not in contact with the resin film is 0.037Ω / Υ, the contact resistance value (B) is 8.63mΩ, and the [contact resistance (B) / (surface resistance (A)×1000)] representing the correlation between the contact resistance value and the surface resistance value is 0.24.

[0147] The contact resistance value was 15 mΩ or less, which was sufficiently small, and was determined to be practically usable as an electrode current collector.

[0148] Furthermore, on the surface of the aluminum metal layer not in contact with the resin film, a ternary lithium-containing transition metal oxide Li(NiCoMn)O 2 (Ni / Co / Mn=6 / 2 / 2), binder resin polyvinylidene fluoride (PVDF), conductive aid carbon black were added with diluent solvent N-methylpyrrolidone in a weight ratio of 94 / 3 / 3 and mixed to obtain a positive electrode active material dispersion. The positive electrode active material dispersion was continuously coated in a roll-to-roll manner using a coating machine including a die coating head, and then calendered and pressed after heating and drying, thereby processing the electrode coating density to 2.8g / cc. During the processing, no coating defects, poor transportability, etc. were found, and the suitability for use was judged as ○.

[0149] (Examples 2 to 4)

[0150] A metallized film was produced and evaluated in the same manner as in Example 1, except that the thickness of the aluminum metal layer was set as described in Table 1. Table 1 shows the results.

[0151] (Example 5)

[0152] As the resin film, a biaxially oriented polyethylene terephthalate film ("Lumirror" (registered trademark), model: F53, manufactured by Toray Co., Ltd.) with a thickness of 5.7 μm was used. The surface roughness Ra of the resin film was 38 nm. The roll-shaped original body of the resin film was placed in a roll vacuum deposition device (EWC-060 manufactured by Ulvac), and the vacuum degree was adjusted to 1×10 -2 Pa or less, and then an aluminum wire was put into the deposition boat heated by resistance heating to perform vacuum deposition, and an aluminum metal layer was vacuum-deposited to a thickness of 1.04 μm and evaluated. The results are shown in Table 1.

[0153] (Examples 6-7)

[0154] As the resin film, a biaxially oriented polyethylene terephthalate film with a thickness of 5.7 μm ("Lumirror" (registered trademark), model: F53, manufactured by Toray Co., Ltd.) was used. The surface roughness Ra of the resin film is 38 nm. The roll-shaped original body of the resin film is placed in a roller vacuum deposition device (EWC-060 manufactured by Ulvac), a pulse power supply is applied, and aluminum is deposited with a thickness of 5 nm by sputtering. As a condition, the sputtering output is 2.0 kW using a pulse power supply. Thereafter, an aluminum wire is put into the deposition boat heated by resistance heating, thereby vacuum deposition is carried out, and aluminum metal layers are vacuum deposited with thicknesses of 1.02 μm and 0.78 μm, respectively, and evaluated. The results are shown in Table 1.

[0155] (Example 8)

[0156] As the resin film, a biaxially oriented polyethylene terephthalate film with a thickness of 5.7 μm ("Lumirror" (registered trademark), model: F53, manufactured by Toray Co., Ltd.) was used. The surface roughness Ra of the resin film was 38 nm. The resin film was placed in a batch vacuum deposition apparatus (EBH-800 manufactured by Ulvac), a pulse power supply was applied, and aluminum was deposited with a thickness of 5 nm by sputtering. As a condition, the sputtering output was 2.0 kW using a pulse power supply. Thereafter, an aluminum metal layer was vacuum deposited with a thickness of 1.44 μm using a resistance heating deposition method in which a deposition boat was heated.

[0157] ACOM-TEM analysis of the aluminum metal layer of the metallized film produced in this way showed that the existence ratio of <001> oriented crystals was 0.715, the existence ratio of <011> oriented crystals was 0.105, the existence ratio of <111> oriented crystals was 0.180, and the surface roughness Ra of the surface of the aluminum metal layer not in contact with the resin film was 47 nm.

[0158] The surface resistance value (A) of the aluminum metal layer of the metal film that is not in contact with the resin film is 0.038Ω / Υ, the contact resistance value (B) is 15.38mΩ, and the [contact resistance (B) / (surface resistance (A)×1000)] representing the correlation between the contact resistance value and the surface resistance value is 0.41.

[0159] The contact resistance value is high, and the contact resistance is also high compared with the surface specific resistance related to the thickness of the aluminum metal layer. The value of [contact resistance (B) / (surface resistance (A)×1000)] is 0.41, which is larger than the metal films described in Examples 1 to 7.

[0160] (Example 9)

[0161] A metallized film was produced and evaluated in the same manner as in Example 8, except that the thickness of the aluminum metal layer was set as described in Table 1. Table 1 shows the results.

[0162] (Example 10)

[0163] After the metallized film of Example 6 was prepared, an aluminum metal layer was formed on the opposite side of the resin film where no aluminum metal layer was formed by the same conditions as the method described in Example 6, thereby forming aluminum metal layers on both sides of the resin film.

[0164] Furthermore, the positive electrode active material dispersion was applied onto the aluminum metal layers on both surfaces of the resin film by the method described in Example 1, and roll pressing was performed after drying.

[0165] (Comparative Example 1)

[0166] A metallized film was produced and evaluated in the same manner as in Example 8, except that the thickness of the aluminum metal layer was set as described in Table 1. Table 1 shows the results.

[0167] (Comparative Examples 2 to 3)

[0168] As the resin film, a biaxially oriented polyethylene terephthalate film ("Lumirror" (registered trademark), model: F53, manufactured by Toray Co., Ltd.) with a thickness of 5.7 μm was used. The surface roughness of the resin film was 38 nm. The roll-shaped original body of the resin film was placed in a roll vacuum deposition device (EWC-060 manufactured by Ulvac), and the vacuum degree was adjusted to 1×10 -2 Pa or less, and then aluminum wire was put into the vapor deposition boat heated by resistance heating, thereby vacuum vapor deposition was performed in a manner that the thickness of the aluminum metal layer became about 50nm. In Comparative Example 2, the vapor deposition process was performed a total of 19 times, and in Comparative Example 3, the vapor deposition process was performed a total of 8 times. In Comparative Example 2, the aluminum metal layer was vacuum-deposited with a thickness of 1.05μm, and in Comparative Example 3, the aluminum metal layer was vacuum-deposited with a thickness of 0.41μm, and the evaluation was performed. The results are shown in Table 1.

[0169] Among the characteristics of the metal film, the interfacial adhesion between the resin film and the aluminum metal layer is weak. In the pressing process after applying the positive electrode active material, a part of the aluminum metal layer / positive electrode active material composite layer peels off from the resin film. In addition, the surface roughness Ra of the aluminum metal layer surface not in contact with the resin film is small at 19nm and 17nm. In terms of suitability of the conveying process, there are also some undesirable conditions such as wrinkles. In addition, the contact resistance is also higher than that of the embodiment, so it is generally judged to lack practicality.

[0170]

[0171]

[0172] Description of Figure Numbers

[0173] 1: Resin film

[0174] 2: Anchoring layer

[0175] 3: Aluminum metal layer

[0176] 4: Metallized film

Claims

1. A metallized film for a secondary battery positive electrode, characterized in that: An aluminum metal layer is formed on at least one surface of the resin film, and when the crystal orientation of the aluminum metal layer cross-section is photographed using automatic crystal orientation mapping-transmission electron microscopy, the areas of the crystalline regions with <001>, <011>, and <111> orientations are all less than 75% of the total. 2 . The metallized film for a secondary battery positive electrode according to claim 1 , wherein the surface roughness Ra of the aluminum metal layer not in contact with the resin film is 15 nm to 60 nm. 3 . The metallized film for a secondary battery positive electrode according to claim 1 , wherein the thickness of the aluminum metal layer is in the range of 0.5 μm to 3.0 μm.

4. The metallized film for a secondary battery positive electrode according to claim 1, wherein when a line parallel to the average line is drawn on the resin film side 300 nm from the top position of the outermost surface of the aluminum metal layer not in contact with the resin film, the average crystal size on the line is 300 nm or less.

5. The metallized film for a secondary battery positive electrode according to claim 1, wherein the surface specific resistance A (Ω / Y) and the contact resistance B (mΩ) of the aluminum metal layer measured by a four-terminal method are in the range of the following formula: 0.05≦B / (A×1000)≦0.

5.

6. A method for producing a metallized film for a secondary battery positive electrode, comprising the steps of: using a vacuum evaporation method, that is, while heating and vaporizing aluminum as an evaporation source by at least one selected from the group consisting of resistance heating, induction heating, and electron beam, introducing argon gas and controlling the vacuum degree to 9.0×10 -3 Pa or more and 1×10 -2 A step of forming a film by depositing the vaporized aluminum on a resin film using a vacuum deposition method at a pressure of Pa or less. 7 . A power storage element comprising the metallized film for a secondary battery positive electrode according to claim 1 . 8 . A power storage module comprising the power storage element according to claim 7 .

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