Resin current collector, resin current collector for bipolar battery, electrode for bipolar battery, secondary battery, solid-state battery, electric vehicle, electric flying object, and electronic appliance

Abstract

The present invention provides a resin film that has high conductivity, that exhibits both good conductivity and high strength, and that has superior conductivity after being stretched or bent.　Specifically, a resin film according to the present invention satisfies the following conditions 1 and 2 when the penetration resistivity is measured at nine locations within the range of a 90 mm × 90 mm square. Condition 1: The average value of the penetration resistivity is 1.0 × 100 Ωcm to 1.0 × 108 Ωcm. Condition 2: The coefficient of variation (the value obtained by dividing the standard deviation by the average value) of the penetration resistivity is 5-70%. (It is to be noted that the positions for measuring the penetration resistivity are defined by dividing the abovementioned range of a 90 mm × 90 mm square into nine 30 mm × 30 mm squares in a 3 × 3 fashion and considering the centers of the respective squares as the measurement positions.)

Description

Resin current collectors, resin current collectors for bipolar batteries, electrodes for bipolar batteries, secondary batteries, solid-state batteries, electric vehicles, electric flying vehicles, and electronic equipment.

[0001] The present invention relates to resin current collectors, resin current collectors for bipolar batteries, electrodes for bipolar batteries, secondary batteries, solid-state batteries, electric vehicles, electric flying vehicles, and electronic devices.

[0002] In recent years, there has been a strong desire to reduce carbon dioxide emissions for environmental protection. The automotive industry is hoping that the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs) will reduce carbon dioxide emissions, and the development of secondary batteries for motor drives, which are key to the practical application of these vehicles, is being actively pursued. In addition to lithium-ion batteries that can achieve high energy density and high power density, next-generation batteries such as lithium anode batteries using metallic lithium anodes, all-solid-state batteries, and air batteries are being considered. Furthermore, beyond automobiles, development is progressing on next-generation mobility such as drones, flying cars, and flying communication base stations, and lightweight, high-energy-density secondary batteries are in high demand.

[0003] In secondary batteries such as lithium-ion batteries, metal foil (metal current collector foil) has traditionally been used as a current collector. However, in recent years, resin current collectors made of resin film have been proposed as an alternative to metal foil. Resin current collectors are lighter than metal current collector foil, and are expected to improve the output per unit weight of the battery.

[0004] In recent years, there has been a surge in the development of bipolar lithium-ion batteries as compact and high-output lithium-ion batteries. Unlike conventional lithium-ion batteries, which extract current generated in the battery cells from electrode tabs attached to the ends of current-collecting foils and connect multiple battery cells, bipolar lithium-ion batteries stack multiple power generation cells via current-collecting foils arranged in the outermost layer, and the current flows in the thickness direction of the current-collecting foils. This configuration eliminates the need for electrode terminals, wiring, and protective casings for the battery cells that were present in conventional batteries, significantly reducing the battery size. Furthermore, by shifting the current flow from the planar direction to the thickness direction of the current-collecting foil, the resistance to the flowing current can be reduced, thereby increasing the battery output.

[0005] For example, Patent Documents 1 and 2 disclose a resin current collector material for a bipolar resin current collector that uses a combination of polyolefin and elastomer or an imide group-containing resin as the main component and contains a high concentration of conductive filler, as well as a resin current collector having said resin current collector material.

[0006] Japanese Patent Publication No. 2019-179732, International Publication No. 2015 / 005116

[0007] To use resin films as current collectors for bipolar batteries, it is necessary to impart conductivity in the thickness direction. Furthermore, there is a demand for thinner resin current collectors. This is because thinning the resin current collector increases the number of current collectors that can be stacked per unit volume, thereby improving the energy density of lithium-ion batteries. In addition, strength is required for resin current collectors from the standpoint of processability and handling.

[0008] However, while Patent Documents 1 and 2 disclose materials for resin current collectors that use polyolefins and elastomers in combination, or materials for resin current collectors that mainly consist of imide group-containing resins and contain a high concentration of conductive fillers, and resin current collectors having such materials, when we performed biaxial stretching of sheets fabricated based on these documents, we found that the conductivity of the resin film decreased significantly, and that there was room for improvement in the film strength and conductivity after stretching or bending.

[0009] The present invention aims to provide a resin film that has high conductivity, achieves both good conductivity and high strength, and exhibits excellent conductivity after being stretched or bent.

[0010] To solve the above problems, a preferred embodiment of the present invention has the following configuration.

[0011] [I] A resin film that satisfies the following conditions 1 and 2 when the penetration resistivity is measured at 9 locations within a 90 mm x 90 mm square area. Condition 1: The average value of the penetration resistivity is 1.0 x 10 ０ Ωcm or more: 1.0 × 10 ８Condition 2 for less than Ωcm: The coefficient of variation of the penetration resistivity (standard deviation divided by the mean value) is 5% or more and 70% or less (however, the measurement position for the penetration resistivity is to divide the 90 mm x 90 mm square area into nine 30 mm x 30 mm squares in a 3 x 3 grid, and the measurement position is the center of each square.) [II] In the SSRM (scanning broadening resistance microscopy) image of the cross section perpendicular to the principal orientation axis - thickness direction, 1.0 x 10 ８ The standard deviation of the area of ​​the Voronoi region formed by the low-resistance region below Ω is 2.0 × 10⁻⁶. ５ nm ２ The above 6.0 x 10 ６ nm ２The resin film according to [I], which is as follows: [III] The resin film according to [I] or [II], comprising a resin component and at least resin A and resin B, which contain carbon particles and / or metal particles, and the resin component is incompatible with each other. [IV] The resin film according to [III], wherein the total content of carbon particles and metal particles is 1.0% by mass or more and less than 20% by mass, based on 100% by mass of the total mass of the resin film. [V] The resin film according to [III] or [IV], wherein resin A and resin B are selected from polyolefin resin and polyester resin. [VI] The resin film according to any one of [III] to [V], wherein when the weight ratio of resin A is Wa (mass%) and the weight ratio of resin B is Wb (mass%), Wa / Wb is 1.0 or more and 2.5 or less. [VII] The resin film according to any one of [III] to [VI], wherein the difference in glass transition temperatures (Tg) of resin A and resin B is 20°C or more and 200°C or less. [VIII] A resin film according to any one of [III] to [VII], wherein the difference between the heat of fusion derived from resin A and the heat of fusion derived from resin B is 4 J / g or more and 45 J / g or less. [IX] A resin film according to any one of [III] to [VIII], wherein resin A is a polypropylene resin and resin B is a polyethylene resin and / or a cyclic olefin resin. [X] A resin film according to any one of [III] to [VIII], wherein resin A is a polyester resin and resin B is a resin selected from one of polypropylene resins, polyethylene resins, and cyclic olefin resins. [XI] A resin film according to any one of [III] to [X], wherein the contained carbon particles and / or metal particles are carbon particles and / or metal particles (C1) with an aspect ratio of 1 or more and less than 5 and carbon particles and / or metal particles (C2) with an aspect ratio of 10 or more. [XII] The resin film according to [XI], wherein the ratio of carbon particles and / or metal particles (C1) having an aspect ratio of 1 or more and less than 5 to carbon particles and / or metal particles (C2) having an aspect ratio of 10 or more is 0.10 or more and 5.0 or less.[XIII] The resin film according to any one of [I] to [XII], wherein an F5 value in at least one direction in a plane (a value obtained by dividing a load value when a test piece is elongated by 5% by a cross-sectional area of the test piece) is 25 MPa or more and 150 MPa or less. [XIV] The resin film according to any one of [I] to [XIII], wherein F5 values in both the longitudinal direction and the width direction (values obtained by dividing a load value when a test piece is elongated by 5% by a cross-sectional area of the test piece) are 25 MPa or more and 150 MPa or less. [XV] The resin film according to any one of [I] to [XIV], wherein an elongation at break in at least one in-plane direction is 13% or more and 220% or less. [XVI] In a binarized analysis image of an SSRM (scanning spreading resistance microscopy) image of a cross-section in the direction perpendicular to the main orientation-the thickness direction, a low resistance region (1.0×10 ８ Ω or less) has an average aspect ratio of 1.5 or more and 2.5 or less, the resin film according to any one of [I] to [XV]. [XVII] The resin film according to any one of [III] to [XVI], wherein in a cross-sectional image of the resin film obtained by a scanning electron microscope, an average area of carbon particles and / or metal particles is 0.10 μm ２ or more and 10 μm ２ or less. [XVIII] The resin film according to any one of [III] to [XVII], wherein in a cross-sectional image of the resin film obtained by a scanning electron microscope, a ratio of the number of carbon particles and / or metal particles having an area of 0.10 μm ２ or more is 25% or more and 100% or less based on 100% of the total number of particles. [XIX] The resin film according to any one of [I] to [XVIII], comprising at least two or more resin layers. [XX] In an SSRM (scanning spreading resistance microscopy) image of a cross-section in the direction perpendicular to the main orientation axis-the thickness direction, a standard deviation of areas of Voronoi regions formed by low resistance regions of 1.0×10 ８ Ω or less is 2.0×10 ５ nm ２ or more and 6.0×10 ６ nm ２The following resin films: [XXI] A resin film according to any one of [I] to [XX], having a thickness of 1 μm or more and 100 μm or less. [XXII] A current collector having a layer made of metal and / or a metallic compound on at least one surface of the resin film according to any one of [I] to [XXI]. [XXIII] The current collector according to [XXII], wherein the layer made of metal and / or a metallic compound contains an aluminum element. [XXIV] The current collector according to [XXII], wherein the layer made of metal and / or a metallic compound on one surface of the resin film contains an aluminum element, and the layer made of metal and / or a metallic compound on the opposite surface contains a copper element. [XXV] A current collector with a penetration resistivity of 1.0 × 10⁻⁶ ０ Ωcm or more: 1.0 × 10 ８ A current collector according to any of [XXII] to [XXIV], having a current collector of Ωcm or less. A resin current collector for a bipolar battery comprising a current collector according to any of [XXVI], [XXII] to [XXV]. An electrode for a bipolar battery comprising a negative electrode active material layer on one surface of the resin current collector for a bipolar battery according to [XXVII] and [XXVI], and a positive electrode active material layer on the surface opposite to the said surface. A secondary battery comprising an electrode for a bipolar battery according to [XXVIII] and [XXVII]. A solid battery comprising at least two layers of the electrodes for a bipolar battery according to [XXIV] and [XXVII], with a solid electrolyte layer between a plurality of hyperbolic battery electrodes. An electric vehicle equipped with a secondary battery according to [XXX] and [XXVIII] or a solid battery according to [XXIX]. An electric flying vehicle equipped with a secondary battery according to [XXXI] and [XXVIII] or a solid battery according to [XXIX]. Electronic equipment equipped with a secondary battery as described in [XXXII] or [XXVII], or a solid-state battery as described in [XXIX].

[0012] The resin film of the present invention has high conductivity, and can achieve both good conductivity and high strength even after stretching, providing a resin film with excellent conductivity after being stretched or bent.

[0013] From the SSRM image of the film cross-section, 1 × 10⁻¹⁶ values ​​were extracted in the binarization analysis. ８ This figure shows an example of the low-resistance region below Ω. This figure shows the Voronoi region of the low-resistance region in Figure 1.

[0014] The present invention will be described in detail below.

[0015] A preferred embodiment of the present invention is a resin film that satisfies the following conditions 1 and 2 when the penetration resistivity is measured at nine locations within a 90 mm x 90 mm square area. Condition 1: The average value of the penetration resistivity is 1.0 x 10 ０ Ωcm or more: 1.0 × 10 ８ Condition 2 for Ωcm or less: The coefficient of variation of the resistivity (standard deviation divided by the mean) is 5% or more and 70% or less. (However, the measurement position for resistivity is determined by dividing the 90mm x 90mm square area into nine 30mm x 30mm squares in a 3x3 grid, with the center of each square being the measurement position.)

[0016] By adopting the above configuration, the resin film of the present invention can obtain not only high conductivity but also high mechanical strength.

[0017] The resin film in this invention has an average penetration resistivity of 1.0 × 10⁻¹⁰ obtained according to the measurement method "D. Penetration Resistivity" described later. ０ Ωcm or more: 1.0 × 10 ８ It is preferable that the density is Ωcm or less.

[0018] The resistivity at penetration is a value that reflects the conductivity in the thickness direction of the film and is independent of the film thickness. The average value of the resistivity at penetration of the resin film in this invention is 1.0 × 10⁻⁶. ０ By setting the resistance to Ωcm or higher, when producing a cast film by electrostatic application in the film manufacturing casting process described later, it is possible to obtain an unstretched film without wrinkles or thickness variations due to uneven application. Furthermore, it is possible to suppress the occurrence of surface defects when a layer made of metal and / or a metal-based compound (M layer), described later, is provided due to wrinkles or thickness variations in the resin film after film formation, and it is possible to suppress a decrease in current value and large variations when incorporated into the electrodes of a bipolar battery as a resin current collector.

[0019] The electrostatic charging method is a technique for obtaining an unstretched sheet by charging a resin layer, bringing it into close contact with a metal casting drum, and then cooling it. However, if the volume resistivity of the resin film is low, the charge generated by the charging process may flow towards the casting drum, reducing the adhesion to the drum and potentially resulting in uneven charging.

[0020] The average value of the puncture resistivity of the resin film in this invention is 1.0 × 10 ８ By setting the resistivity to Ωcm or less, excellent conductivity is achieved, and when used as a resin current collector for bipolar batteries, the current flowing to the battery can be increased, resulting in sufficient battery performance. Furthermore, the average value of the pass-through resistivity is 1.0 × 10⁻⁶. ８ By setting the resistivity to Ωcm or less, conductive paths are sufficiently formed in the thickness direction, and even when the resin film of the present invention is subjected to deformation such as tension or bending during processing as a battery component, a significant decrease in conductivity can be suppressed. The average value of the through-resistivity is more preferably 1.0 × 10⁻⁶. ４ Ωcm or less, more preferably 1.0 × 10⁻⁶ ３ It is less than or equal to Ωcm, and most preferably 1.0 × 10⁻⁶. ２ It is less than or equal to Ωcm.

[0021] One method for imparting conductivity to a resin film is to add conductive particles to the film. In this case, the conductive particles are responsible for forming conductive paths, and conductivity is achieved when the conductive particles are in close proximity to each other. That is, by creating a moderate bias in the distribution of conductive particles, the conductive particles are more likely to be in close proximity to each other compared to when the distribution of conductive particles in the resin film is uniform. Therefore, high conductivity can be obtained with the addition of a small amount of conductive particles, thus suppressing the reduction in the mechanical strength of the resin film caused by the addition of conductive particles while maintaining high conductivity.

[0022] To ensure an appropriate bias in the distribution of conductive particles, it is preferable that the coefficient of variation of the penetration resistivity (standard deviation divided by the mean) be 5% or more. This embodiment means that there is an appropriate variation in conductivity within the surface of the resin film, that is, there is an appropriate bias in the distribution of conductive particles that are responsible for forming conductive paths in the resin film. A more preferable range for the coefficient of variation of the penetration resistivity is 25% or more, an even more preferable range is 30% or more, and the most preferable range is 55% or more. Furthermore, it is preferable that the coefficient of variation of the penetration resistivity be 70% or less. By adopting this embodiment, it is possible to suppress thermal runaway due to heat generation associated with localized current generation in an energy storage element using the resin film of the present invention as a resin current collector for a bipolar battery.

[0023] Furthermore, in the SSRM (Scanning Spread Resistance Microscopy) image of the cross-section perpendicular to the principal orientation axis and in the thickness direction, 1.0 × 10 ８ The standard deviation of the area of ​​the Voronoi region formed by the low-resistance region below Ω is 2.0 × 10⁻⁶. ５ nm ２ The above 6.0 x 10 ６ nm ２ By doing the following, the cross-section of the resin film in the direction perpendicular to the main orientation and in the thickness direction is 1 × 10 ８ A moderate bias is created in the distribution of the low-resistance region below Ω, i.e., the conductive region. In this specification, the direction orthogonal to the principal orientation is the direction in which the breaking strength is highest when the breaking strength is measured every 15° in the in-plane direction. In a resin film with a perfectly uniform distribution of conductive regions, the overall resistance is high because the distribution is uniform and there are no extremely low-resistance regions. Therefore, by creating a moderate bias in the distribution of conductive regions, high conductivity can be imparted even when the conductive region in the entire film is smaller compared to a resin film with a uniform distribution of conductive regions.

[0024] The above 1 × 10 ８ The standard deviation of the area of ​​the Voronoi region formed by the low-resistance region below Ω is 1.0 × 10⁻⁶. ６ nm ２ It is more preferable that the above be the case, 1.5 × 10 ６ nm ２ It is even more preferable that the above be the case, 3.0 × 10６ nm ２ The above is most preferable. Also, the above 1 × 10 ８ The standard deviation of the area of ​​the Voronoi region formed by low-resistance regions below Ω is 6.0 × 10⁻⁶. ６ nm ２ The following is preferable. If the distribution is extremely wide, areas with low strength may become noticeable. Therefore, by setting the standard deviation of the area of ​​the Voronoi region to the above range, it is possible to suppress the decrease in the mechanical strength of the resin film and to suppress the breakage of conductive paths due to the increase in distance between the low-resistance regions caused by bending or stretching. 1 × 10 within the resin film ８ A large average value of the Voronoi region formed by low-resistance regions below Ω indicates a high probability that the distance between these low-resistance regions is large. The average value of the Voronoi region formed by the aforementioned low-resistance regions is 4.2 × 10⁻⁶. ６ nm ２ The following configuration is preferable, and by adopting such a configuration, conductivity can be improved. Furthermore, if the average value of the Voronoi region formed by the low-resistance region is too small, the low-resistance region may be uniformly distributed within the resin film. Therefore, a large amount of conductive particles must be added to impart sufficient conductivity, which may reduce the strength of the resin film. The average value of the Voronoi region formed by the low-resistance region is 1.2 × 10⁻⁶. ６ nm ２ It is preferable that the above conditions are met.

[0025] In the binarization analysis of the SSRM (Scanning Spread Resistance Microscopy) images of the cross-section of the resin film in the direction orthogonal to the principal orientation and the thickness direction, 1 × 10⁻¹⁰ images were extracted. ８ It is preferable that the average aspect ratio of the low-resistance region of Ω or less is 1.5 or more and 2.5 or less. When the resin film is stretched to increase its strength, the low-resistance region in the resin film is stretched in the direction in which the film is stretched, i.e., in the direction in the film plane, so there is a possibility that the conductive paths in the thickness direction will be severed. 1 × 10 in the resin film ８By setting the average aspect ratio of the low-resistance region (below Ω) to 1.5 or higher, a resin film with greater strength as a current collector can be obtained while maintaining conductive paths in the film thickness direction. ８ The average aspect ratio in the low-resistance region of Ω or less is more preferably 1.7 or higher. Furthermore, by setting this average value to 2.5 or lower, a resin film with both excellent strength and excellent conductivity can be obtained. ８ The average aspect ratio in the low-resistance region of Ω or less is more preferably 2.4 or less.

[0026] (Resin Alloy) As a method for creating an appropriate bias in the distribution of conductive particles in a resin film, one method is to use at least two types of resins that are incompatible with each other. In this specification, incompatible means that when resin A and resin B are melt-kneaded, they do not form a single phase that is uniformly mixed at the molecular level, but rather exhibit a phase-separated structure in which at least one resin exists as a dispersed phase in the other resin. The above-mentioned at least two types of resins that are incompatible with each other include, for example, at least two types of resins with different fluidity. In this specification, different fluidity means that the fluidity of the resins differs in their molten state or when dissolved in a certain solvent. By selecting at least two types of resin A and resin B with different fluidity using the method described later, conductive particles can be unevenly distributed in the resin with high fluidity. Furthermore, by appropriately separating the phases of resin A and resin B in the resin film and forming a sea-island structure or a co-continuous structure, the distribution of conductive particles in the film can be biased.

[0027] In this specification, when a resin film contains multiple different resins, the resins in the resin film will be named as Resin A, Resin B, Resin C, etc., in order from the resin with the highest mass percentage. In this specification, a sea-island structure refers to a structure in which two or more types of resins are phase-separated from each other, and the other resins (Resin B, Resin C, etc.) exist as islands within the main component resin (Resin A). In this specification, a structure in which the island components of the sea-island structure are connected to each other will be referred to as a co-continuous structure.

[0028] Resins with different fluidity can be selected from, for example, resins with different glass transition temperatures (hereinafter sometimes referred to as Tg) or resins with different crystallinity. The differences in glass transition temperature and crystallinity in this specification can be measured in accordance with JIS K 7121-1987, and details will be described later.

[0029] The larger the Tg difference between resin A and resin B, the more efficiently conductive particles are distributed to one resin during resin film molding. However, if the Tg difference between resin A and resin B is too large, complete phase separation occurs between resin A and resin B, which can lead to void formation and a decrease in the mechanical strength of the resin film. Preferably, the Tg difference between resin A and resin B is 20°C or more and 200°C or less. In other words, it is preferable that the resin film in the present invention has one or more sets of glass transition temperatures where the difference in glass transition temperature (Tg) is 20°C or more and 200°C or less. When the Tg difference is 20°C or more, conductive particles efficiently distribute to the resin with the lower Tg during the resin film molding process, and resin A and resin B undergo moderate phase separation, making it easier to form a sea-island structure or a co-continuous structure. As a result, a resin film with a moderate bias in the distribution of conductive particles and high conductivity can be obtained. More preferably, the Tg difference between resin A and resin B is 80°C or more, even more preferably 120°C or more, and most preferably 130°C or more. Furthermore, by setting the Tg difference to 200°C or less, it is possible to suppress the reduction in strength caused by voids that occur when resin A and resin B completely separate, while maintaining high conductivity. The Tg difference between resin A and resin B is more preferably 180°C or less.

[0030] Furthermore, from the viewpoint of achieving both high conductivity and mechanical strength, it is preferable that there is a difference in the crystallinity of resin A and resin B. Since conductive particles cannot exist in crystals, conductive particles are ubiquitous in the amorphous regions of the resin film. Therefore, the greater the difference in crystallinity between resin A and resin B, the more efficiently conductive particles are distributed in one of the resins, resulting in higher conductivity. On the other hand, if the difference in crystallinity between resin A and resin B is too large, complete phase separation may occur between resin A and resin B, leading to the generation of voids and a decrease in the mechanical strength of the resin film.

[0031] The difference in the crystallinity of the resins can be defined by the difference in the heat of fusion during the heating process in measurements according to JIS K 7121-1987. In this invention, the heat of fusion is the amount of heat generated when the resin present as crystals in the resin film melts when the resin film of the present invention is heated according to measurements according to JIS K 7121-1987. In other words, a large heat of fusion originating from resin A means that a high proportion of resin A exists as crystals in the film of the present invention (high crystallinity). Preferably, the difference between the heat of fusion originating from resin A and the heat of fusion originating from resin B is 4 J / g or more and 45 J / g or less. By setting the difference in heat of fusion to 4 J / g or more, conductive particles efficiently concentrate on the resin side with a smaller heat of fusion (lower crystallinity), and resins A and B undergo appropriate phase separation, making it easier to form a sea-island structure or a co-continuous structure, thus enabling the production of a resin film with high conductivity. The difference between the heat of fusion derived from resin A and the heat of fusion derived from resin B is more preferably 10 J / g or more, and even more preferably 25 J / g or more. Furthermore, by setting the difference between the heat of fusion derived from resin A and the heat of fusion derived from resin B to 45 J / g or less, it is possible to suppress the reduction in strength due to voids generated by the complete phase separation of resin A and resin B while maintaining high conductivity.

[0032] (Ratio of resin A and resin B Wa / Wb) Preferably, the sum of the content of resin A and resin B in 100% by mass of the resin film is 60% by mass or more. By adopting the above configuration, an efficient bias is created in the distribution of conductive particles in the resin film, and resin A and resin B can form a sea-island structure or a co-continuous structure, thereby obtaining a resin film with good conductivity.

[0033] When the fluidity of resin A is higher than that of resin B, and the weight ratio of resin A is Wa (mass%) and the weight ratio of resin B is Wb (mass%), the closer Wa / Wb is to 1.0, the more efficiently conductive paths can be formed. This is because the volume of resin A, i.e., the ocean component, which has high fluidity and where conductive particles tend to be unevenly distributed, decreases, making it easier for the distance between conductive particles to decrease.

[0034] Even when the fluidity of resin A is lower than that of resin B, the closer the Wa / Wb ratio of resins A and B is to 1.0, the more efficiently conductive paths can be formed. Conductive particles tend to be concentrated in resin B, i.e., in the island components of the sea-island structure. In such cases, for the resin film to exhibit conductivity in the thickness direction, it is important to create a co-continuous structure in which the island components containing conductive particles are connected in the thickness direction. This configuration can be achieved by bringing the mass ratio of the weight ratio Wb (mass%) of resin B in the resin film closer to the weight ratio Wa (mass%) of the main component resin A, i.e., bringing Wa / Wb closer to 1.0.

[0035] Therefore, from the viewpoint of conductivity, it is preferable that Wa / Wb be close to 1.0 even when the fluidity of resin A and resin B is reversed. On the other hand, from the viewpoint of the strength of the resin film, it is preferable that Wa / Wb be large. From the viewpoint of providing a resin film that has excellent conductivity while suppressing strength reduction, it is preferable that Wa / Wb be between 1.0 and 2.5. Since it is possible to suppress strength reduction due to layer separation between resin A and resin B while having high conductivity, it is more preferable that Wa / Wb be 1.4 or higher, and even more preferable that it be 1.5 or higher. Furthermore, from the viewpoint of being able to impart high strength while having excellent conductivity, it is more preferable that Wa / Wb be 1.8 or lower.

[0036] When a large amount of conductive material is added to impart conductivity to a resin film, there is a concern that, when resin film is manufactured by melt extrusion, which offers high productivity, discharge irregularities may occur during the process, and that frequent film breakage may occur during stretching treatment aimed at thinning or increasing strength, thus reducing productivity. Furthermore, when processed for use as a battery component, it may be a factor in reducing yield in processing steps such as creating a layer (M layer) made of metal and / or a metal-based compound, or electrode coating. From the viewpoint of productivity and mechanical strength of the resin film, it is preferable that the two types of resins, resin A and resin B, are selected from polyolefin resins and polyester resins. The two types of resins, resin A and resin B, may be selected from two types of polyolefin resins, two types of polyester resins, or one type from polyolefin resins and one type from polyester resins. By adopting the above configuration, stable extrusion molding is possible during the film manufacturing process by melt extrusion, and the resin film is less prone to breakage during subsequent stretching treatments, allowing for efficient acquisition of a resin film that balances strength and conductivity without compromising productivity.

[0037] (Polyolefin resin) In the present invention, a polyolefin resin refers to a resin that contains olefin units in an amount greater than 50 mol% and less than or equal to 100 mol%, when the total constituent units of the resin are set to 100 mol%. The method for producing polyolefins is not particularly limited, and known polymerization methods, such as radical polymerization or ionic polymerization using Ziegler catalysts, metallocene catalysts, or Phillips catalysts, can be employed.

[0038] The polyolefin resins in the present invention include, for example, homopolymers of α-olefins having about 2 to 8 carbon atoms, such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, and 1-hexene; copolymers of these α-olefins with other α-olefins having about 2 to 12 carbon atoms, such as ethylene, propylene, 1-butene, 3-methyl-1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1-decene; vinyl compounds such as vinyl acetate, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, styrene, and vinyl chloride; and graft polymers obtained by grafting the vinyl compounds onto the homopolymers or copolymers of the α-olefins, as well as cyclic olefin resins described later.

[0039] (Polyester Resin) The polyester resin in this invention is obtained by polycondensation of a dicarboxylic acid component and a diol component. In this specification, a component refers to the smallest unit that can be obtained by hydrolysis of polyester.

[0040] Examples of diol components constituting such polyester resins include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol, as well as alicyclic diols such as 1,4-cyclohexanedimethanol and spiroglycol, and multiple diols linked together as described above.

[0041] Examples of dicarboxylic acid components constituting such polyester resins include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, and 4,4'-diphenyletherdicarboxylic acid, or their ester derivatives.

[0042] Examples of polyester resins containing such dicarboxylic acid and diol components include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), and polycyclohexylenedimethylene terephthalate (PCT). These polyester resins may have isophthalic acid or naphthalenedicarboxylic acid copolymerized into a portion of the dicarboxylic acid component of the polyester, or polyethylene glycol copolymerized into a portion of the diol component, to the extent that it does not affect the effects of the present invention.

[0043] When two types of resins, resin A and resin B, are selected from polyolefin resins, it is preferable that resin A is polypropylene resin and resin B is polyethylene resin, or that resin A is polypropylene resin and resin B is a cyclic olefin resin. With the above configuration, resin A and resin B are appropriately phase-separated, resulting in an appropriate bias in the distribution of conductive particles, which allows for high conductivity, as well as a resin film with high mechanical strength, which suppresses performance degradation due to bending when used as a current collector.

[0044] Polypropylene resin refers to a resin in which, when the total constituent units of the resin are set to 100 mol%, propylene units are present in an amount greater than 50 mol% and less than or equal to 100 mol%. Polypropylene resin may be a homopolymer of propylene (homopolypropylene resin) or a copolymer of propylene and an olefin having 2 to 20 carbon atoms (random polypropylene resin). One or more types of olefins may be copolymerized with propylene. Specific examples of random polypropylene resins include propylene-ethylene copolymer, propylene-1-butene copolymer, and propylene-ethylene-1-butene copolymer. Among these, homopolypropylene resin is preferred from the viewpoint of mechanical properties and moldability.

[0045] Polyethylene resin refers to a resin in which, when the total constituent units of the resin are set to 100 mol%, ethylene units are present in an amount greater than 50 mol% and less than or equal to 100 mol%. Polyethylene resin may be a homopolymer of ethylene, or a copolymer of ethylene and an olefin having 2 to 20 carbon atoms. One or more types of olefins may be copolymerized with ethylene. Specific examples of random polypropylene resin include ethylene-propylene copolymer, ethylene-1-butene copolymer, and ethylene-propylene-1-butene copolymer. Among these, a homopolymer of ethylene is preferred, and by using the above-mentioned polyethylene resin, layer separation from the polypropylene resin occurs efficiently, and a bias in the distribution of conductive particles, which is good for high conductivity, can be achieved.

[0046] A cyclic olefin resin is a polyolefin resin that contains 10 mol% to 100 mol% of cyclic olefin units when the total constituent units of the resin are set to 100 mol%. In the case of resins containing multiple types of constituent units equivalent to cyclic olefin units, even if each individual cyclic olefin unit is less than 10 mol%, if the sum of these constituent units exceeds 10 mol%, the resin is considered a cyclic olefin resin.

[0047] The cyclic olefin resin can be any polyolefin resin in which the total amount of components derived from cyclic olefin monomers in 100% by mass of the cyclic olefin resin polymer is greater than 10% by mass but not more than 100% by mass. This includes resins polymerized solely from the cyclic olefin monomers (hereinafter sometimes referred to as COP), resins copolymerized from the cyclic olefin monomers and chain-like olefin monomers (hereinafter sometimes referred to as COC), and cyclic block copolymer resins having an alicyclic structure (hereinafter sometimes referred to as CBC). When the cyclic olefin resin is used in combination with a polypropylene resin in a resin film, it is preferable that it be a COC or CBC having a chain-like olefin structure, from the viewpoint of suppressing a decrease in strength due to complete layer separation between different resins.

[0048] Known methods for producing COP include addition polymerization or ring-opening polymerization of cyclic olefin monomers. Examples include a method of ring-opening metathesis polymerization of norbornene, tricyclodecene, tetracyclodecene, and their derivatives followed by hydrogenation; an addition polymerization method of norbornene and its derivatives; and a 1,2-,1,4-addition polymerization of cyclopentadiene and cyclohexadiene followed by hydrogenation. Among these, the method of ring-opening metathesis polymerization of norbornene, tricyclodecene, tetracyclodecene, and their derivatives followed by hydrogenation is more preferred from the viewpoint of productivity and moldability.

[0049] In the case of COC, preferred chain-like olefin monomers include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. Among these, ethylene or both ethylene and propylene can be particularly preferred from the viewpoint of productivity and cost. Furthermore, known methods for producing resins copolymerized from cyclic olefin monomers and chain-like olefin monomers include addition polymerization of cyclic olefin monomers and chain-like olefin monomers, such as the addition polymerization of norbornene and its derivatives with ethylene. In particular, copolymerizing norbornene and ethylene is more preferable from the viewpoint of productivity and moldability.

[0050] In particular, from the viewpoint of productivity and moldability, methods such as binary polymerization or ternary polymerization using norbornene, tetracyclododecene, or derivatives thereof with ethylene and / or propylene can be preferably used as methods for producing COC. For example, binary polymerization of a tetracyclododecene derivative with ethylene, or ternary polymerization of norbornene, ethylene, and propylene can be preferably used.

[0051] The chain-like olefin monomer and cyclic olefin monomer used to obtain COC may each be one type, or one or both may be two or more types. In particular, using a cyclic olefin copolymer having ethylene and propylene as constituent units is especially preferable from the viewpoint of improving compatibility with polypropylene resin. As for the cyclic olefin monomer, norbornene, norbornadiene, and their derivatives are preferably used alone or in combination from the viewpoint of improving the heat resistance of the biaxially oriented polyolefin film.

[0052] For cyclic block copolymer resins (CBCs), it is preferable to use those having hydrogenated aromatic vinyl polymer block units and hydrogenated conjugated diene polymer block units. Examples of aromatic vinyl monomers before hydrogenation include styrene, α-methylstyrene, vinyltoluene (including all isomers, with p-vinyltoluene being particularly preferred), ethylstyrene, propylstyrene, butylstyrene, vinylbiphenyl, vinylnaphthalene, vinylanthracene (including all isomers), and mixtures thereof. Examples of conjugated diene monomers before hydrogenation include 1,3-butadiene, 2-methyl-1,3-butadiene, 2-methyl-1,3-pentadiene, isoprene and its analogues, and mixtures thereof.

[0053] Known methods for producing CBC include the hydrogenation of block copolymers consisting of the above-mentioned aromatic vinyl monomer and conjugated diene monomer, and among these, the method of hydrogenating styrene-butadiene copolymer is particularly preferred from the viewpoint of productivity and moldability.

[0054] Even when two types of resins, resin A and resin B, are selected from among polyester resins, the resin film in the present invention can be suitably used as a current collector. In such cases, from the viewpoint of the strength of the resin film, it is preferable that resin A is polyethylene naphthalate (PEN) and resin B is selected from polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polycyclohexylene dimethylene terephthalate (PCT).

[0055] Furthermore, in these polyester resins, isophthalic acid or naphthalenedicarboxylic acid may be copolymerized with a portion of the dicarboxylic acid component of the polyester, or polyethylene glycol may be copolymerized with a portion of the diol component. By adopting the above configuration, it is possible to suppress the reduction in mechanical strength due to complete phase separation of resin A and resin B while creating a bias in the distribution of conductive particles in the resin film.

[0056] When the two types of resins, resin A and resin B, are each selected from polyolefin resins or polyester resins, it is preferable that resin A is a polyester resin and resin B is a resin selected from polypropylene resin, polyethylene resin, or cyclic olefin resin. By adopting the above configuration, a resin film with high mechanical strength can be obtained because it contains polyester resin as the main component, and performance degradation due to bending and other factors can be suppressed when used as a current collector. In addition, because resin A and resin B are efficiently phase-separated, a bias occurs in the distribution of conductive particles, and high conductivity can be obtained.

[0057] When the two resins, resin A and resin B, are selected one each from polyolefin resins or polyester resins, and the compatibility between resin A and resin B is insufficient, raising concerns about void formation, a compatibilizer may be added to the extent that it does not impair the effects of the present invention. The compatibilizer is preferably a resin having oxygen functional groups, and from the viewpoint of efficiently achieving compatibility between polyester resins and polyolefin resins, the resin having oxygen functional groups is more preferably an acid-modified polyolefin. The acid-modified polyolefin resin is preferably a polyolefin resin modified with an unsaturated carboxylic acid or its derivative. Examples of such unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, etc. Esters and anhydrides of these can also be used. Examples of derivatives include methyl acrylate, methyl methacrylate, ethyl acrylate, propyl acrylate, butyl acrylate, butyl methacrylate, vinyl acetate, glycidyl acrylate, glycidyl methacrylate, acrylamide, methacrylamide, sodium acrylate, etc.

[0058] (Conductive particles) Examples of conductive particles contained in the resin film of this specification include metal particles, conductive resin particles, and carbon particles.

[0059] Examples of metal particles used as conductive particles include particles mainly composed of one metal selected from the elements gold, silver, copper, tin, nickel, indium, aluminum, and iron; metal particles such as stainless steel and nickel-indium alloys; and particles made of metal oxides such as tin oxide, zinc oxide, and zinc oxide. Alternatively, a core surface made of any resin may be plated with the above metals or metal oxides.

[0060] Examples of conductive resin particles used as conductive particles include resins having a conjugated double bond structure in the main chain skeleton, such as polyacetylene, poly-p-phenylene, polyfluorene, and poly-p-phenylene vinylene; thiophene-based resins such as polyethylenedioxythiophene (PEDOT) / polystyrene sulfonic acid (PSS), polythiophene, and polythiolenylene vinylene; polyaniline; and polypyrrole.

[0061] Carbon particles are defined by Raman spectroscopy as having a graphite structure (sp) commonly referred to as the G band. ２ 1580 cm (derived from the combination) －１ The vicinity, and the diamond structure commonly referred to as the D band (sp ３ 1350 cm (derived from the combination) －１ This indicates materials in which peaks are observed in the vicinity.

[0062] The particles used as conductive particles preferably include one or more selected from metal particles and carbon particles, in order to suppress a decrease in the strength of the resin film and to impart high conductivity with a small amount of addition, and it is even more preferable that the particles are carbon particles.

[0063] In the present invention, it is preferable that the resin film contains a total of 1.0% by mass or more and less than 20% by mass of carbon particles and / or metal particles in 100% by mass of the resin film.

[0064] By including these particles in an amount of 1.0% by mass or more and less than 20% by mass, the penetration resistivity of the aforementioned film can be controlled to a desirable range, and good conductivity can be achieved in the thickness direction of the resin film.

[0065] By ensuring that the amount of carbon material and / or metal particles contained in the resin film is 1.0% by mass or more, the volume resistivity (penetration resistivity) in the penetration direction of the resin film can be reduced, thereby improving the conductivity of the film. Furthermore, the conductivity in the thickness direction can be made uniform. The concentration of these particles is more preferably 4.0% by mass or more, and even more preferably 6.0% by mass or more.

[0066] By limiting the amount of conductive particles contained in the resin film to less than 20% by mass, when the resin film of the present invention is melt-formed, discharge turbulence during the film-forming process can be suppressed, and the occurrence of numerous tears or minute air pockets (hereinafter sometimes referred to as voids) originating from the conductive particles during stretching can be suppressed, preventing the film from tearing during stretching. Since the occurrence of numerous voids can be suppressed, the conductivity in the thickness direction can also be made uniform. Furthermore, by limiting the amount of carbon material and / or metal particles contained in the resin film to less than 20% by mass, a significant decrease in the mechanical strength of the film can be suppressed. This prevents a significant decrease in conductivity even when the film is deformed during processing as a battery component. In addition, when the resin film of the present invention is mounted in a secondary battery as a current collector, it is possible to suppress the rupture of the resin film due to thermal deformation associated with charging and discharging of the battery or minute deformation due to external stress, which would otherwise degrade the battery performance. The total amount of carbon material and / or metal particles contained in the resin film is more preferably 15% by mass or less, and most preferably 10% by mass or less.

[0067] The particle size of the carbon material is not particularly limited as long as it is at least twice the thickness of the resin film, and can be used. Examples of nano-sized carbon materials include furnace black, acetylene black, carbon nanotubes such as single-walled carbon nanotubes, multi-walled carbon nanotubes, and thin-walled carbon nanotubes, carbon fibers, graphene, Ketjenblack, fibrous carbon, fullerene, graphite, carbon nanohorns, carbon nanocones, carbon nanocoils, carbon microcoils, carbon nanowalls, carbon nanochaplets, carbon nanoflakes, and derivatives thereof. As for micro-sized carbon materials, carbon materials such as "Nikabeads®" ICB, PC, MC, and MPA manufactured by Nippon Carbon Co., Ltd. can be used.

[0068] Preferably, the carbon material contains, in 100% by mass, a total of 80% by mass or more of one or more selected from furnace black, acetylene black, carbon nanotubes such as single-walled carbon nanotubes, multi-walled carbon nanotubes, and thin-walled carbon nanotubes, carbon fibers, graphene, Ketjenblack, fibrous carbon, fullerene, graphite, and "Nikabeads®" ICB, PC, MC, and MPA manufactured by Nippon Carbon Co., Ltd., and more preferably, in 100% by mass of the carbon material, a total of 80% by mass or more and 100% by mass or less of Ketjenblack, carbon nanotubes, acetylene black, and one or more selected from "Nikabeads®" ICB, PC, MC, and MPA manufactured by Nippon Carbon Co., Ltd.

[0069] In the resin film of the present invention, it is preferable that the conductive particles contain at least two types of conductive particles: conductive particles C1 with an aspect ratio of 1 or more and less than 5, and conductive particles C2 with an aspect ratio of 10 or more. The method for determining the aspect ratio of the conductive particles contained in the resin film will be described later. Regardless of whether the conductive particles are metal particles, conductive resin particles, or carbon material, the aspect ratio can be determined by the same measurement method.

[0070] The resin film contains at least two types of conductive particles, conductive particles C1 with an aspect ratio of 1 or more and conductive particles C2 with an aspect ratio of 10 or more. This allows the volume resistivity of the film to be within a desirable range with a smaller amount of conductive particles than when either conductive particle is contained alone. Furthermore, conductive paths are sufficiently formed in the thickness direction, and even when the resin film of the present invention is subjected to deformation such as tension or bending during processing as a battery component, a significant decrease in conductivity can be suppressed. In addition, since the conductive particle content can be small, the mechanical strength of the film can be increased.

[0071] The ability to suppress a significant decrease in conductivity even when subjected to deformation such as pulling or bending can be explained as follows. Conductive particles with an aspect ratio of 10 or more have high conductivity in the direction of the long axis of the conductive particle and have the function of transmitting electrons over long distances. However, when subjected to deformation such as pulling or bending, the spacing between conductive particles widens, making the connection points prone to breakage. Conductive particles with an aspect ratio of 1 or more and less than 5 are smaller in size and have a shape closer to a sphere compared to conductive particles with an aspect ratio of 10 or more. When at least two types of conductive particles with different aspect ratios are contained in the resin film, when subjected to deformation such as pulling or bending, conductive particles with an aspect ratio of 1 or more and less than 5 can enter between the broken conductive paths of conductive particles with an aspect ratio of 5 or more, thereby suppressing the breakage of conductive paths.

[0072] Furthermore, the resin film in the present invention contains at least two types of conductive particles: conductive particles C1 with an aspect ratio of 1 or more and conductive particles C2 with an aspect ratio of 10 or more. This suppresses the decrease in conductivity when the resin film is heated. This is because, even if the dispersion state of the contained conductive particles changes due to the increased mobility of the resin molecular chains under high-temperature conditions, conductive particles with an aspect ratio of 1 or more and less than 5 can enter between the broken conductive paths of conductive particles with an aspect ratio of 5 or more, thereby suppressing the breaking of conductive paths. For this reason, in energy storage elements using the resin film in the present invention as a resin current collector for a bipolar battery, the decrease in current value is suppressed even when the temperature rises during operation.

[0073] Furthermore, from the same viewpoint as above, it is preferable that the resin film in the present invention contains at least two types of carbon materials: carbon material C1 having an aspect ratio of 1 or more and less than 5, and carbon material C2 having an aspect ratio of 10 or more.

[0074] Here, the carbon material C1 having an aspect ratio of 1 or more and less than 5 is preferably one or more selected from furnace black, acetylene black, Ketjen black, fullerene, and "Nikabeads®" ICB, PC, MC, and MPA manufactured by Nippon Carbon Co., Ltd., and from the viewpoint of excellent conductivity, the carbon material C1 having an aspect ratio of 1 or more and less than 5 is more preferably acetylene black and / or Ketjen black.

[0075] Furthermore, the carbon material C2 with an aspect ratio of 10 or more is preferably one or more selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, and graphene, and among these, one selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, and carbon fibers is more preferred.

[0076] The resin film of the present invention preferably contains carbon particles and / or metal particles (C1) having an aspect ratio of 1 or more and less than 5, and carbon particles and / or metal particles (C2) having an aspect ratio of 10 or more, wherein the ratio of C1 to C2 is preferably 0.10 or more and 5.0 or less.

[0077] By setting the ratio of C1 to C2 to 0.10 or higher, conductive particles C1 with an aspect ratio of 1 or more and less than 5 can penetrate between conductive particles C2 with an aspect ratio of 10 or more, thereby more effectively suppressing the severance of conductive paths when subjected to deformation such as pulling or bending. In particular, it is possible to suppress the deterioration of electrical properties after the resin film has been subjected to tension-applying processing such as metal deposition. A more preferable range for the ratio of C1 to C2 is 0.20 or higher. Furthermore, by setting the ratio of C1 to C2 to 5.0 or lower, conductivity can be obtained without increasing the particle content, resulting in a film with excellent mechanical strength, a film that does not stretch easily when tension is applied, and an effect of suppressing the severance of conductive paths when subjected to deformation such as pulling or bending. The ratio of C1 to C2 is more preferably 4.5 or lower.

[0078] In a cross-sectional image of a resin film obtained by scanning electron microscopy, the average area of ​​carbon particles and / or metal particles, determined by the method described later, is 0.10 μm. ２ 10 μm or more ２ The following is preferable: The average value of the area is 0.10 μm ２ The above indicates that the carbon particles and / or metal particles contained in the resin film are appropriately aggregated, and act as relay points when electrons are conducted in the thickness direction of the film. This is because, if carbon particles and / or metal particles are excessively dispersed and exist individually, the molecular structure of the carbon particles and / or metal particles restricts the movement of electrons to a linear or planar direction, which may prevent improvement in electron conductivity in the thickness direction. On the other hand, when multiple carbon particles and / or metal particles aggregate in a moderately irregular manner, the carbon particles and / or metal particles spread out three-dimensionally, expanding the range of electron movement. This allows electrons to be efficiently transferred between aggregates of carbon particles and / or metal particles present in the resin film, improving electron conductivity in the thickness direction. The average area of ​​the carbon particles and / or metal particles contained in the resin film is more preferably 2.5 μm. ２ More preferably 3.0 μm ２ That concludes the explanation. Furthermore, the average value of the area is 10 μm. ２ The following conditions can suppress film tearing caused by carbon particles and / or metal particles when the film is stretched or subjected to tensile tension. The average value of the area tends to increase with the concentration of conductive particles, and when carbon particles and / or metal particles are contained in amounts exceeding 20% ​​by mass, the average value of the area becomes 10 μm. ２ The following would be extremely difficult: A more preferable range for the average area of ​​the particles contained in the resin film is 9.0 μm. ２ A more preferred range is 8.5 μm. ２ The following applies:

[0079] In the cross-sectional image of the resin film obtained by scanning electron microscopy, the area determined by the method described later is 0.10 μm. ２Preferably, the proportion of carbon particles and / or metal particles is 25% or more and 100% or less of the total number of particles.

[0080] Area: 0.10 μm ２ As described above, the carbon particles and / or metal particles contained in the resin film aggregate appropriately, which is effective in forming conductive paths in the film thickness direction. Furthermore, the area is 0.10 μm². ２ Between the above particles, there is a 0.10 μm ２ This is because the presence of particles smaller than 0.10 μm allows for the efficient formation of conductive paths in the film thickness direction. ２ A more preferable proportion of the number of particles meeting the above criteria is 30% or more.

[0081] <Method for measuring the area of ​​each particle> Cross-sectional images at a magnification of 3500x using a scanning electron microscope (JEOL Ltd., JSM-6700) are analyzed using image analysis software (National Institutes of Health, ImageJ) as follows.

[0082] (Image Analysis Conditions) (i) Preprocessing After the cross-sectional image is captured by the software, 8-bit grayscale processing is performed by executing the 8-bit command under 'Type' in the 'Image' menu. Next, a straight line with a known distance is drawn using the 'Straight' menu, and the scale of the captured image is set using the 'Set Scales' command under the 'Analyze' menu. After that, the 'Subtract' command under 'Math' in the 'Process' menu is used to subtract with 'Value' set to 30. Using the 'Enhance Contrast' command from the 'Process' menu, 'Saturated pixels' is set to 5%, 'Normalize' is checked, and the 'OK' button is pressed. From the 'Process' menu, select 'Filters' and then the 'Gaussian Blur' command, setting 'Sigma (Radius)' to 1 to apply the blur effect.

[0083] (ii) Binarization From the 'Image' menu, select 'Adjust' and then 'Threshold', check only 'Dark background' and 'Don't reset range', press 'Auto', and then press 'Apply'.

[0084] (iii) Noise Reduction From the 'Process' menu, select 'Noise' and then the 'Remove Outliers' command. Set 'Saturated pixels' to 1 pixel, 'Threshold' to 50, and 'Which Outliers' to Bright, then press the 'OK' button.

[0085] (iv) Particle analysis conditions In the "Analyze" menu, use the "Set Measurements" command, check "Area" and "Feret's diameter", and press the "OK" button. Next, in the "Analyze" menu, use the "Analyze Particles" command, set each item as follows, and press the "OK" button to display the analysis results (Results).

[0086] • Size: 0-Infinity • Circulation: 0.00-1.00 • Show: Nothing • Check the boxes for 'Display Results', 'Clear Results', 'Exclude on edges', and 'include holes'.

[0087] From the obtained results, the average area of ​​the particles and the area of ​​the particles were 0.10 μm. ２ Find the proportion of particles that meet the above criteria.

[0088] (Average area of ​​particles) Using the 'Area' of each particle detected above, the average area is calculated according to Equation 1 below. The average area is calculated for five different fields of view and these averages are taken as the average area S (μm) of the particles in the sample.

[0089] S (μm) ２ ) = Σ(Area) / number of items ... Equation 1

[0090] (Particle area is 0.10 μm)２ (Percentage of particles with the above number) The 'Area' of each particle detected above is defined as the area of ​​each particle. Of the detected particles, the area is 0.10 μm ２ Count the number of particles that meet the above criteria, and determine that the area of ​​each particle is 0.10 μm² according to Equation 2 below. ２ Find the proportion R of particles that meet the above criteria.

[0091] R (%) = (area of ​​0.10 μm) ２ (Number of particles equal to or greater than the specified number) / Total number of particles × 100 (%) ... Equation 2

[0092] The resin film of the present invention preferably has a thickness of 1 μm or more and 100 μm or less. A film thickness of 1 μm or more suppresses the occurrence of tearing during film formation and improves film formation performance. A preferred range for the film thickness is 2.0 μm or more, more preferably 3 μm or more, and most preferably 4.0 μm or more. Furthermore, a film thickness of 100 μm or less minimizes the increase in battery size when incorporated as a resin current collector for a bipolar battery. A more preferred range for the film thickness is 80 μm or less.

[0093] (Film F5 Value) The resin film in the present invention preferably has an F5 value of 25 MPa or more in at least one direction within the surface (the value obtained by dividing the load value when the test piece is stretched by 5% by the cross-sectional area of ​​the test piece), more preferably an F5 value of 25 MPa or more in at least one of the longitudinal and width directions within the film surface, and even more preferably an F5 value of 25 MPa or more in both directions. By setting the F5 value to 25 MPa or more, when the resin film in the present invention is incorporated into an electrode as a current collector, it is possible to suppress the deterioration of the performance as an electrode due to the resin film breaking when a slight impact is applied during transportation of the electrode. The F5 value is more preferably 30 MPa or more, and even more preferably 35 MPa or more. Furthermore, by setting the F5 value to 25 MPa or higher, in processes where the resin film is subjected to high temperatures while bound to the roll during transport, such as roll-to-roll metal deposition processes, slight thermal deformation occurs under the tension during film transport, which inhibits the formation of conductive paths by conductive particles within the resin film and suppresses an increase in volume resistivity. In addition, when the resin film of the present invention is incorporated into a battery element, even if the battery element is subjected to a large impact such as dropping or collision, deformation and fracture of the resin film can be suppressed, thereby suppressing a significant decrease in battery characteristics and preventing the battery element from igniting due to a short circuit.

[0094] Furthermore, in the present invention, the resin film preferably has an F5 value of 150 MPa or less in at least one direction within the film surface (the value obtained by dividing the load value when the test piece is stretched by 5% by the cross-sectional area of ​​the test piece), more preferably an F5 value of 150 MPa or less in at least one of the longitudinal and width directions within the film surface, and even more preferably an F5 value of 150 MPa or less in both the longitudinal and width directions within the film surface. If the F5 value is made to be greater than 150 MPa, high-magnification stretching will be required in the stretching step of the manufacturing method of the biaxially oriented resin film described later, but this may make the film more prone to tearing during stretching. Furthermore, the range of the F5 value in at least one direction within the film surface is preferably 25 MPa or more and 150 MPa or less, and the range of the F5 value in both directions is preferably 25 MPa or more and 150 MPa or less.

[0095] In the present invention, when the F5 value of the resin film is defined as the longitudinal direction when the roll unwinding direction of the resin film is defined as the longitudinal direction, and the direction obtained by rotating the resin film 90° in plane relative to the longitudinal direction is defined as the width direction of the resin film, it is more preferable that at least one of the F5 values ​​in the longitudinal direction and the width direction satisfies the above-mentioned preferred range. It is even more preferable that both the F5 values ​​in the longitudinal direction and the width direction satisfy the above-mentioned preferred range.

[0096] (Elongation at Break) In the present invention, the resin film preferably has an elongation at break of 13% or more and 220% or less in at least one direction within the plane. By setting the elongation at break to 13% or more, when the resin film is incorporated into a battery element, even if the battery element is subjected to a large impact such as dropping or collision, deformation and breakage of the resin film can be suppressed, thereby suppressing a significant decrease in battery performance and preventing the battery element from igniting due to a short circuit. The elongation at break of the resin film in at least one direction within the plane is more preferably 35% or more, and even more preferably 40% or more. Furthermore, the elongation at break is preferably 220% or less. Molecular chains in a resin film with an extremely high elongation at break tend to have insufficient orientation in the in-plane direction, resulting in lower mechanical strength and heat resistance of the resin film. For example, in processes where a resin film with extremely high elongation at break is subjected to high temperatures while bound to a roll during transport, such as a roll-to-roll metal deposition process, the probability of the film undergoing significant thermal shrinkage or the resin film breaking under the tension of film transport increases.

[0097] The resin film in this invention may be a single-layer structure or a laminated structure. The laminated structure may be a two-layer structure of P2 layer / P1 layer or a three-layer structure of P2 layer / P1 layer / P2 layer.

[0098] In the present invention, when a layer made of a metal and / or a metal-based compound (hereinafter referred to as the M layer) is provided in the resin film, corona treatment, plasma treatment, flame treatment, ultraviolet irradiation treatment, solvent treatment, etc. may be performed on the surface of the resin film to the extent that the effects of the present invention are not impaired, in order to improve the adhesion between the resin film and the M layer.

[0099] In the present invention, when a layer made of metal and / or a metal-based compound (hereinafter referred to as the M layer) is provided in the resin film, if the resin film contains a polyolefin resin as the main component of the resin in the resin film, it is preferable to have a laminated structure of two or more layers (P1 layer / P2 layer) from the viewpoint of achieving both adhesion to the layer made of metal and / or a metal-based compound (hereinafter referred to as the M layer) described later and the mechanical strength of the film, and to add a resin having oxygen functional groups only to the outermost layer that is in direct contact with the M layer. This is because increasing the amount of resin having oxygen functional groups improves adhesion to the M layer, but the mechanical properties decrease with increasing amounts. When used as a resin current collector for a bipolar battery described later, it is preferable to provide the M layer on both surfaces of the film, so from the viewpoint of achieving both adhesion to the film and the mechanical strength of the film, it is most preferable that the resin film containing polyolefin resin as resin A has a three-layer structure of P2 layer / P1 layer / P2 layer or P2 layer / P1 layer / P3 layer.

[0100] (Method for manufacturing a biaxially oriented resin film) Next, an example of a method for manufacturing a biaxially oriented resin film in the present invention will be described, but the present invention is not to be interpreted as being limited only to what can be obtained by such example.

[0101] In the present invention, when the resin film contains two or more resins with different fluidity and / or two or more conductive particles, it is preferable to create a master pellet containing one of each resin and one of the conductive particles, and to mix and use it when forming the resin film. By producing the resin film using the above method, it is possible to prevent excessive mixing of resins with different fluidity and / or resins with different crystallinity, and to keep the bias in the distribution of conductive particles within an appropriate range. Furthermore, when mixing conductive particles and resins, the appropriate mixing temperature for dispersing the conductive particles and the shear stress during mixing differ, so if multiple conductive particles are mixed simultaneously, at least one of the conductive particles may aggregate during mixing.

[0102] For creating a master pellet for dispersing conductive particles in a resin, it is preferable to use a twin-screw kneader.

[0103] (Method for manufacturing a film in which polyolefin is the main component) The present invention will be described with an example of a method for manufacturing a resin film in which polyolefin resin is the main component and the film is biaxially oriented, but the present invention is not to be interpreted as being limited only to the product obtained by such example.

[0104] In the present invention, the biaxially oriented film is preferably obtained by biaxially stretching an unstretched sheet using the above-mentioned resin. The biaxial stretching can be performed by any of the following methods: simultaneous inflation biaxial stretching, simultaneous tenter biaxial stretching, or sequential biaxial stretching using a roll stretcher and tenter. Among these, sequential biaxial stretching using a roll stretcher and tenter is preferred in terms of controlling film formation stability, thickness uniformity, high rigidity, and dimensional stability of the film.

[0105] Next, one embodiment of the method for manufacturing a biaxially oriented film according to the present invention will be described using a biaxially oriented polyolefin film with a two-type, three-layer structure as an example, but the biaxially oriented resin film in the present invention is not necessarily limited to this.

[0106] The resin composition pellets obtained above, or a mixture using them, are supplied to a single-screw extruder for the surface layer (I) and / or a single-screw extruder for the base layer (II). Then, melt extrusion is performed at 200 to 280°C, more preferably 220 to 275°C, and even more preferably 230 to 270°C, respectively. After removing foreign matter and modified polymers using a filter installed in the middle of the polymer tube, the layers are laminated in a surface layer (I) / base layer (II) / surface layer (I) configuration using a multi-manifold type composite T-die, and then discharged onto a casting drum for cooling and solidification to obtain a laminated unstretched sheet having a surface layer (I) / base layer (II) / surface layer (I) layer configuration. At this time, the laminate thickness ratio is preferably in the range of 1 / 5 / 1 to 1 / 60 / 1 from the viewpoint of balancing surface properties, mechanical strength, and thermal properties.

[0107] Furthermore, while there are no particular restrictions on the surface temperature of the casting drum, from the viewpoint of suppressing the formation of β crystals during crystallization, it is preferably 10 to 40°C, more preferably 15 to 30°C, even more preferably 19 to 27°C, and particularly preferably 20 to 25°C. The layer structure may also be a two-layer laminated structure of surface layer (I) / base layer (II). As for the method of adhesion to the casting drum, any of the following methods may be used, such as the electrostatic application method, the adhesion method using the surface tension of water, the air knife method, the press roll method, and the underwater casting method, but from the viewpoint of uniform adhesion in the width direction, the electrostatic application method or the air knife method is preferred.

[0108] The obtained laminated unstretched sheet is introduced into the longitudinal stretching process. In the longitudinal stretching process, it is preferable to perform longitudinal stretching in two stages during the preheating process before stretching. In the first stage of preheating, it is preferable to heat the laminated unstretched sheet by bringing it into contact with multiple metal rolls that are kept at a temperature below the softening temperature of the polyolefin resin used for the film. In the second stage of preheating, it is preferable to heat the sheet at a temperature higher than the preheating temperature of the first stage, more preferably at a temperature of 10°C or higher than the preheating temperature of the first stage, and even more preferably at a temperature of 20°C or higher than the preheating temperature of the first stage. By setting the preheating temperature and stretching temperature within the above range, the resin can be appropriately softened in the preheating process, deformation can be controlled during stretching, and as a result, the crystalline structure of the film can be suitably controlled.

[0109] Subsequently, in the stretching process, the laminated unstretched sheet is stretched in the longitudinal direction by 4.0 to 6.0 times, more preferably 4.5 to 5.8 times, and even more preferably 4.8 to 5.5 times, between rolls with a difference in peripheral speed. The longitudinal direction refers to the direction in which the film travels during the manufacturing process (or the winding direction if it is wound into a roll). A stretching ratio of 4.0 times or more in the longitudinal direction increases the mechanical strength in the longitudinal direction, thereby suppressing deformation of the film even under high tension and making it easier to maintain the flatness of the biaxially oriented film. Furthermore, a stretching ratio of 6.0 times or less in the longitudinal direction suppresses thermal shrinkage caused by excessive strain during stretching, making it easier to maintain the flatness of the biaxially oriented film.

[0110] Next, by applying a relaxation treatment in the longitudinal direction, the increase in the thermal shrinkage rate of the biaxially oriented film can be suppressed. From the viewpoint of improving handling performance as a film with good flatness, the temperature of the relaxation treatment in the longitudinal direction is preferably below the softening temperature of the resin added to the film, more preferably below the resin softening temperature - 10°C, and even more preferably below the resin softening temperature - 20°C. From the viewpoint of good film transportability, the relaxation rate in the relaxation treatment in the longitudinal direction is preferably 2.0% or more and less than 15.0%, the lower limit of the relaxation treatment in the longitudinal direction is more preferably 3.0%, and even more preferably 5.0%. The upper limit of the relaxation treatment in the longitudinal direction is more preferably 12.0%, and even more preferably 10.0%.

[0111] Next, the uniaxially oriented film is guided to a tenter by gripping both ends in the width direction with clips, preheated, and then transversely stretched to 7.0 to 12 times its original width. The lower limit of the stretching ratio is preferably 7.5 times, and more preferably 8.0 times, from the viewpoint of uniform stretching of the film. The upper limit of the stretching ratio is more preferably 11 times, from the viewpoint of stable stretching without tearing the film. The width direction refers to the direction perpendicular to the longitudinal direction within the film surface.

[0112] The preheating temperature is preferably below the melting point of the resin used in the film - 15°C, from the viewpoint of uniformly stretching the film and suppressing the formation of sharp protrusions. The upper limit of the preheating temperature is more preferably below the melting point of the resin - 20°C, and even more preferably below the melting point of the resin - 25°C.

[0113] From the viewpoint of uniform stretching of the film, the stretching temperature is preferably below the melting point of the resin. The lower limit of the stretching temperature is more preferably -5°C from the melting point of the polyolefin resin, and even more preferably -10°C from the melting point of the resin, from the viewpoint of stable stretching without melting and breaking the film. By setting the preheating and stretching temperatures within the above ranges, a uniaxially oriented film can be uniformly stretched laterally, and a biaxially oriented film with a uniform thickness can be obtained.

[0114] In the subsequent heat treatment and relaxation process, from the viewpoint of uniformly relaxing and shrinking the film, both ends in the width direction of the biaxially stretched film are held taut with clips, and while relaxing at a relaxation rate of 5.0 to 20%, more preferably 7 to 15%, and even more preferably 9 to 12% in the width direction, heat setting is performed at 140°C to 180°C, more preferably 150°C to 173°C. Furthermore, while both ends in the width direction are still held taut with clips, the film is guided to the outside of the tenter after a cooling process at 80 to 100°C, and the clips at both ends in the width direction are released. After that, plasma treatment by atmospheric pressure glow discharge is performed on both surfaces of the film in the winder process, the film edges are slit, and the biaxially oriented film product roll is wound up.

[0115] (Method for manufacturing a film with polyester as the main component) Next, an example of a method for manufacturing a resin film in the present invention that contains polyester resin as the main component and is a biaxially oriented film will be described, but the present invention is not to be interpreted as being limited only to the product obtained by such example.

[0116] A conventional polymerization method can be used to obtain the resin film used in the present invention. For example, it can be obtained by transesterifying or esterifying the aforementioned dicarboxylic acid component or its ester-forming derivative with the aforementioned diol component or its ester-forming derivative using a known method, followed by a melt polymerization reaction. Alternatively, if necessary, the polyester obtained by the melt polymerization reaction may be subjected to a solid-phase polymerization reaction at a temperature below the melting point of the polyester.

[0117] The resin film in this invention can be obtained by conventionally known manufacturing methods. Specifically, the resin film in this invention can be obtained by a method in which, if necessary, dried raw materials are heated and melted in an extruder and extruded from a die onto a cooled cast drum to form a sheet (melt casting method). As an alternative method, a method can also be used in which raw materials are dissolved in a solvent, the solution is extruded from a die onto a support such as a cast drum or endless belt to form a film, and then the solvent is dried and removed from the film layer to form a sheet (solution casting method).

[0118] When manufacturing a resin film with two or more layers by the melt casting method, a preferred method is to use an extruder for each layer constituting the biaxially oriented film, melt the raw materials for each layer, and then laminate them in a molten state in a confluence device located between the extruder and the die. After guiding the melted materials to the die, the extruder is pushed from the die onto a cast drum cooled to a surface temperature of 20°C to 60°C, allowing the materials to adhere tightly and be processed into a sheet to form an unstretched film (co-extrusion method). In particular, by setting the cast drum temperature to 40°C or higher, the cooling of the resin is delayed, making it easier for the resin to temporarily adhere to the cast drum, which can sometimes further improve the adhesion between the unstretched film and the cast drum using the electrostatic application method described later.

[0119] Methods for adhering the unstretched film to the cast drum include electrostatic charging, where the extruded resin is charged using a charging device with high voltage application and then adhered to the cast drum; methods for sandwiching the polyester resin between the cast drum and nip rolls and adhering it to the drum; and methods for pressing the resin down with air pressure and adhering it to the cast drum. From the viewpoint of achieving uniform adhesion in the width direction, the electrostatic charging method is preferable.

[0120] (Sequential Biaxial Stretching) When biaxially stretching an unstretched film, the stretching conditions are as follows: When the resin film in this invention is mainly composed of polyester resin, it is preferable to stretch the unstretched film longitudinally using a group of rolls heated to 70°C or higher, and then cool it using a group of rolls set to a temperature of 20°C to 50°C. There is no particular lower limit to the heating roll temperature in longitudinal stretching as long as the stretchability of the sheet is not impaired, but it is preferable to exceed the glass transition temperature of the polyester resin used. Furthermore, the preferred range for the longitudinal stretching ratio is 1.4 times to 5 times. A more preferred range is 2 times to 4 times. When the longitudinal stretching ratio is 1.4 times or higher, orientation crystallization progresses and the film strength can be improved. On the other hand, by setting the stretching ratio to 5 times or lower, it is possible to suppress excessive orientation crystallization of the polyester resin accompanying stretching, which can make the film brittle and cause tearing during film formation.

[0121] Following the process film (uniaxially oriented film) stretched in the longitudinal direction, it is stretched in a direction perpendicular to the longitudinal direction (width direction). Preferably, the uniaxially oriented film is guided to a tenter while being held at both ends with clips, and stretched by 1.4 to 5 times in the direction perpendicular to the longitudinal direction (width direction) in an atmosphere heated to a temperature of 70°C to 160°C.

[0122] Subsequently, it is preferable to heat-treat the stretched film to stabilize its internal orientation structure. The thermal history temperature of the film during heat treatment can be confirmed by the minute endothermic peak (sometimes called Tmeta) temperature that appears just below the melting point temperature, measured by a differential scanning calorimeter (DSC) as described later. When polyester is the main component, it is preferable to set the tenter device temperature to above the resin melting point -80°C or below the resin melting point -10°C. Setting the heat treatment temperature above the resin melting point improves the dimensional stability of the biaxially oriented polyester film. Furthermore, setting the heat treatment temperature below the resin melting point -10°C suppresses the occurrence of film tearing due to the melting of the polyester film, enabling productive manufacturing. A more preferable range for heat treatment temperature is a lower limit of above the resin melting point -70°C and an upper limit of below the resin melting point -20°C.

[0123] Furthermore, to impart dimensional stability after heat treatment, a relaxation treatment may be performed in the range of 1% to 6%. By performing a relaxation treatment of 1% or more, the dimensional stability of the biaxially oriented polyester film can be improved when used in a high-temperature environment, while by performing it of 6% or less, an appropriate tension can be continuously applied to the biaxially oriented polyester film, preventing the deterioration of thickness uniformity.

[0124] The stretching ratio should be 1.4 times or more and 5 times or less in both the longitudinal and width directions, but the area ratio (stretching ratio in the longitudinal direction × stretching ratio in the width direction) is preferably 2 times or more and 25 times or less, and more preferably 9 times or more and 20 times or less. By setting the area ratio to 2 times or more, the molecular orientation of the resulting biaxially oriented polyester film can be promoted and its durability can be improved, and by setting the area ratio to 25 times or less, the occurrence of tearing during stretching can be suppressed.

[0125] (M layer: layer made of metal and / or metallic compound) The resin film in the present invention preferably has at least a layer made of metal and / or metallic compound, the resin film, and a layer made of metal and / or metallic compound in this order, and it is more preferable that a layer made of metal and / or metallic compound (M layer) is provided on both sides of the resin film. With this configuration, when the resin film of the present invention is used as a current collector, the contact resistance between the current collector and the electrode member can be reduced.

[0126] The method for forming the M layer in the present invention is not particularly limited, but methods such as deposition, sputtering, or electroplating under vacuum conditions or reduced pressure conditions with an inert gas such as argon gas (hereinafter collectively referred to as the deposition method), methods of directly bonding a metal foil or metal compound foil to a resin film or via an adhesive layer, and methods of forming a metal layer by electrochemical reaction using a solution containing a metal salt (electroplating method, electroless plating method) can be used. Among these, the deposition method is preferred from the viewpoint of continuously forming the M layer on a film using a resin film roll.

[0127] When using the vacuum deposition method, it is preferable to pre-install a film roll in a vacuum chamber, and while the unwound film is in close contact with a cooling roll, heated and vaporized metal and / or metal compounds are solidified and deposited onto the film surface to form the M layer, and then the film is wound up again as a film roll.

[0128] Here, the inside of the vacuum chamber is 9.0 × 10 －３Under vacuum conditions below Pa, or by sealing with an inert gas such as argon, 9.0 × 10 －３ Pa or more 1×10 －１ Any of the reduced pressure conditions below Pa can be suitably used. Furthermore, the M layer may be formed by performing two or more deposition processes in succession, such as providing a first M layer by sputtering and then providing a second M layer by vacuum deposition.

[0129] Vacuum deposition methods include induction heating deposition, resistance heating deposition, laser beam deposition, and electron beam deposition. Among these, electron beam deposition, laser beam deposition, and induction heating deposition are preferred because they generate a large amount of heat from the deposition source. The amount of heat generated by the deposition source needs to be large enough to form an M layer of the desired thickness, and the substrate surface temperature needs to be sufficiently high. However, since it is difficult to measure this directly, it is possible to determine whether the amount of heat is sufficient by confirming that the M layer after deposition is of the desired thickness.

[0130] However, if the heat generated by the deposition source is increased to the required amount, the temperature of the resin film will rise with the cooling function of a normal vacuum deposition method, potentially leading to thermal damage that degrades the mechanical properties of the resin film, and even melting of the resin film. Therefore, it is preferable to manage the cooling function during deposition to ensure uniform cooling of the film and prevent the temperature from rising too high. Specifically, it is preferable to uniformly cool the film from the back surface using a cooling mechanism consisting of a metal plate or metal roll sufficiently cooled with a refrigerant. To achieve uniform cooling, it is essential to ensure tight contact between the resin film and the cooling mechanism without creating any gaps. By improving the adhesion, thermal damage to the surface of the resin film can be reduced, and the deterioration of the mechanical properties of the resin film can be suppressed.

[0131] For example, if there is a scratch on the metal roll of the cooling mechanism, the scratched area becomes a gap, preventing the resin film from being cooled, and increasing the thermal damage to the resin film. Also, if foreign matter gets into the resin film and the metal roll of the cooling mechanism, the foreign matter prevents the resin film from being cooled, increasing the thermal damage. When the heat output of the deposition source is increased to the required amount, scratches on the metal rolls and foreign matter contamination, which are acceptable in normal vacuum deposition methods, become problematic, so the control of scratches on the metal rolls and foreign matter contamination needs to be made even stricter.

[0132] In the present invention, when the M layer is to have a desired metal layer thickness, a method of forming it in a single deposition (defined as the sequence of unwinding, deposition, and winding) is preferred from the viewpoint of productivity, resistance characteristics, and quality. However, for example, a thin film deposition process in which a 50 nm thick aluminum deposition layer is formed in a single deposition is repeated 20 times (the above sequence is repeated 20 times) to form an aluminum metal layer with a total thickness of 1 μm.

[0133] Examples of metallic elements that constitute the M layer include gold, silver, copper, zinc, lead, nickel, iron, aluminum, titanium, cobalt, manganese, cadmium, and palladium. The M layer may consist of individual metallic elements, or it may consist of a metallic compound in which the metallic elements are mixed with oxygen, nitrogen, fluorine, carbon, boron, chlorine, sulfur, and phosphorus. Furthermore, the metallic elements of the M layer provided on the resin film may be the same on both sides or different on each side.

[0134] When used as a resin current collector for a bipolar battery, it is preferable that the M layer present on both sides of the laminated film be such that one side is an M layer made of copper and / or nickel, and the other side is an M layer made of aluminum. Furthermore, to prevent corrosion and rust of the M layer, a barrier layer may be provided on top of the M layer. Examples of the barrier layer include a carbon layer, a layer made of nickel, a layer made of titanium, and a stainless steel thin film. In particular, when the resin current collector having an M layer on the resin film of the present invention is applied to a solid-state battery equipped with a sulfide-based electrolyte, it is preferable that the barrier layer be selected from a layer made of nickel, a layer made of titanium, and a stainless steel thin film.

[0135] In the resin film of the present invention, the laminated structure of the resin film and the layer made of a metal and / or metallic compound preferably has at least the following in this order: a layer made of a metal and / or metallic compound, the resin film, and a layer made of a metal and / or metallic compound. Specifically, the following configurations can be exemplified. When the resin film is a single layer, it is preferable to have an M layer / P1 layer / M layer configuration, or an M layer / P1 layer / M' layer having a layer (M' layer) made of a metal and / or metallic compound made of a different metal element than the M layer.

[0136] When the resin film consists of two or more layers, it is preferable that the layers are M layer / P1 layer / P2 layer / M layer, M layer / P1 layer / P2 layer / M' layer, or M layer / P2 layer / P1 layer / P2 layer / M layer, or M layer / P2 layer / P1 layer / P2 layer / M' layer. Furthermore, when used as a resin current collector for a bipolar battery, from the viewpoint of reducing contact resistance at the interface between the active material layer and the resin current collector and suppressing a decrease in battery characteristics, it is more preferable that the resin film in the present invention has the P1 layer as the outermost layer on both sides of the resin film, and has layers made of metal and / or metal-based compounds on both sides of the P1 layer.

[0137] Furthermore, the resin film in the present invention may be provided with an anchor layer or an undercoat layer, to the extent that the effects of the present invention are not lost, for the purpose of improving adhesion with the M layer and improving electrochemical stability when used as a resin current collector for a bipolar battery. The thickness of the anchor layer or undercoat layer (U layer) is preferably 0.010 μm or more and 1.0 μm or less. A thickness of 0.010 μm or more for the U layer allows for better adhesion between the resin film and the M layer, and better electrochemical stability when used as a resin current collector for a bipolar battery. Also, a thickness of 1.0 μm or less for the U layer allows for limiting the size of the bipolar battery into which the resin film in the present invention is incorporated when used as a resin current collector for a bipolar battery.

[0138] The thickness of the M layer in the resin film of the present invention is not particularly limited, but it is preferable that it be 0.10 μm or more, as this minimizes the deterioration of electrical properties due to thickness variations in the metal layer when used as a resin current collector. The thickness of the M layer is more preferably 0.20 μm or more, and even more preferably 0.50 μm or more. Furthermore, it is preferable to set the thickness of the M layer to 5.0 μm or less, as this reduces the increase in battery weight when used as a resin current collector for batteries. It is even more preferable that it be 3.0 μm or less.

[0139] In the present invention, it is preferable that the adhesion force between the outermost layer of the resin film and the M layer is 0.50 N / 15 mm or more on both sides. When the adhesion force between the outermost layer of the resin film and the M layer is 0.50 N / 15 mm or more on both sides of the resin film, when the resin film having the M layer is incorporated into a power storage element as a current collector, if the current collector is deformed by stress such as impact or heat, the interface between the outermost layer of the resin film at the edge and the M layer will peel off, and other battery components will penetrate into the interface, thereby reducing the efficiency of the charge-discharge reaction of the power storage element and suppressing a decrease in battery characteristics. The adhesion force is more preferably 0.70 N / 15 mm or more on both sides, and even more preferably 1.0 N / 15 mm or more.

[0140] The average value of the penetration resistivity of a current collector having the M layer on at least one surface of the resin film of the present invention is 1.0 × 10 ０ Ωcm or more: 1.0 × 10 ８ It is preferable that it is Ωcm or less. The average value of the penetration resistivity can be determined in "F. Penetration Resistivity" described below. The average value of the penetration resistivity is 1.0 × 10 ０ By having a resistivity of Ωcm or more, when the resin film of the present invention is incorporated into a storage element as a resin current collector for a bipolar battery, the resin film acts as a resistor, suppressing thermal runaway and ignition from the storage element that occur when the storage element is damaged due to a short circuit. Furthermore, the average value of the through-pass resistivity is 1.0 × 10⁻⁶. ８By being less than or equal to Ωcm, when the resin film of the present invention is incorporated into a bipolar energy storage element as a resin current collector for a bipolar battery, it is possible to suppress the increase in the internal resistance of the bipolar energy storage element and the decrease in battery output. The average value range of the above-mentioned pass-through resistivity is 1.0 × 10 ６ It is more preferable to have a value of Ωcm or less, and 1.0 × 10 ５ It is more preferable to have a value of Ωcm or less, and 1.0 × 10 ５ A value of Ωcm or less is even more preferable, and 1.0 × 10 ４ A value of Ωcm or less is most preferable.

[0141] (Resin Current Collector) The current collector in the present invention preferably consists of the resin film, and has an M layer on both surfaces of the resin film. By using the resin film with good penetration resistivity, the current collector in the present invention has excellent conductivity in the thickness direction. Surface treatment may also be applied to improve the adhesion between the M layer and the resin film. This makes it suitable for use as a current collector for a bipolar battery, as described later.

[0142] (Current collector for bipolar battery) In the current collector for a bipolar battery of the present invention, it is preferable that the current collector has a configuration in which different M layers are present on both sides of the resin film. By using the current collector which has excellent conductivity in the thickness direction, when incorporated into a bipolar battery, it is possible to achieve excellent current value stability as described later and suppress variations in battery characteristics. In addition, a bipolar battery incorporating the current collector for a bipolar battery which has excellent mechanical properties exhibits excellent durability against external stress such as deformation and impact. Furthermore, by controlling the shape of the conductive particles contained in the resin film, stable battery operation can be achieved even in high-temperature environments.

[0143] In the present invention, when used as a lithium-ion battery, it is more preferable that the metal elements constituting the M layer of the current collector for a bipolar battery consist of aluminum on one side and copper on the other.

[0144] (Electrodes) The electrode for a bipolar battery in the present invention consists of an electrode assembly including a positive electrode and a negative electrode, which have a negative electrode active material layer on one side of the surface layer of a resin current collector for a bipolar battery and a positive electrode active material layer on the side opposite to the surface layer.

[0145] (Secondary battery) Examples of secondary batteries 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-based secondary batteries, vanadium-lithium secondary batteries, and the like.

[0146] Among these, secondary batteries are preferred because they can be used for a long period of time, and lithium secondary batteries are more preferred because they can achieve high energy density.

[0147] As the battery case, for example, an aluminum case, an iron case whose inner surface is nickel-plated, a case made of an aluminum laminate film, or the like can be used.

[0148] Examples of the shape of the battery case include pouch type, cylindrical type, prismatic type, coin type, and the like. Among these, the pouch type is preferred because it can achieve high energy density and allows free design of the shape at low cost.

[0149] The positive electrode is formed by laminating a positive electrode material composed of an active material, a binder resin, and a conductive aid on a current collector. As the active material, LiCoO ２ , LiNiO ２ , Li(NiCoMn)O ２ , lithium-containing transition metal oxides having a layered structure such as the above, LiMn ２ O ４ spinel-type manganese oxides such as the above, iron-based compounds such as LiFePO ４ and the like. As the binder resin, a resin having high oxidation resistance may be used. Specific examples include fluorine-containing resins, acrylic resins, styrene-butadiene resins, and the like. Examples of the conductive aid include carbon materials such as carbon black and graphite.

[0150] The negative electrode is formed by laminating a negative electrode material composed of an active material and a binder resin on a current collector. As the active material, carbon materials such as artificial graphite, natural graphite, hard carbon, and soft carbon, lithium alloy-based materials such as tin and silicon, metal materials such as lithium, and lithium titanate (Li４ Ti ５ O １２ ), etc. Examples of the binder resin include fluorine-containing resins, acrylic resins, styrene-butadiene resins, and the like.

[0151] In the secondary battery of the present invention, it is preferable to use a bipolar battery electrode comprising a resin current collector for bipolar batteries formed of a film in which a copper layer is provided on one side and an aluminum layer is provided on the opposite side by vacuum deposition or the like on both sides of a resin film. Particularly preferably, the bipolar battery electrode has a configuration in which at least two or more layers of the positive electrode active material layer and the negative electrode active material layer are laminated with an electrolyte interposed therebetween.

[0152] The secondary battery of the present invention may contain an electrolytic solution, and in this case, it preferably includes a separator interposed between the positive electrode and the negative electrode.

[0153] (Secondary battery containing an electrolytic solution) In the secondary battery containing an electrolytic solution according to the present invention, the electrolytic solution serves as a medium for moving ions between the positive electrode and the negative electrode in an electrochemical device such as a secondary battery, and has a configuration in which an electrolyte is dissolved in an organic solvent.

[0154] Examples of the electrolyte include LiPF ６ , LiBF ４ , and LiClO ４ , and the like. From the viewpoint of solubility in organic solvents and ionic conductivity, LiPF ６ is preferably used.

[0155] Examples of the organic solvent include ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like, and two or more of these organic solvents may be mixed and used.

[0156] Hereinafter, a method for producing a lithium secondary battery containing an electrolytic solution will be described with an example, but the present invention should not be construed as being limited only to products obtained by such examples.

[0157] In a method for manufacturing a lithium secondary battery containing an electrolyte, first, an electrode coating solution is prepared by dispersing an active material and a conductive additive in a binder resin solution. This coating solution is then applied to a current collector, and the solvent is dried to obtain the positive electrode and negative electrode, respectively. The thickness of the coating film after drying is preferably 50 μm or more and 500 μm or less. Furthermore, it is preferable to apply pressure to the active material layer formed on the current collector using a method such as a roll press to densify it and thin the current collector.

[0158] A lithium secondary battery separator is placed between the positive and negative electrodes so as to be in contact with the active material layer of each electrode, then enclosed in an outer packaging material such as an aluminum laminate film, and after injecting the electrolyte, the negative electrode lead and safety valve are installed, and the outer packaging material is sealed.

[0159] The lithium secondary battery obtained in this way has high adhesion to the electrodes, excellent battery characteristics, and can be manufactured at low cost.

[0160] In the present invention, the electrodes for a bipolar battery may be used as a secondary battery by connecting multiple electrodes in series to meet the application and required battery capacity of the secondary battery. In that case, it is preferable to have a secondary battery equipped with voltage control, temperature control, and safety devices by connecting multiple electrodes in series, or to have a secondary battery equipped with voltage control, temperature control, and safety devices by connecting multiple module units, each containing multiple electrodes connected in series and housed in a case, in series or parallel. It is preferable to connect the electrodes with tab lead wires (current extraction wires) and house them in a resin or metal module case to use them as a secondary battery.

[0161] (Solid-state secondary batteries) Solid-state secondary batteries equipped with a solid electrolyte layer are also preferred. One example of a solid-state secondary battery is an all-solid-state secondary battery that does not contain an electrolyte. Semi-solid secondary batteries and quasi-solid secondary batteries that include an electrolyte in which liquid components such as plasticizers, ionic liquids, and solvents remain in the solid electrolyte layer, and / or a gelled electrolyte, are also preferred.

[0162] The solid electrolyte used in the solid-state secondary battery of the present invention is not particularly limited, but examples include sulfide solid electrolytes. A sulfide solid electrolyte is a solid electrolyte that contains at least sulfur atoms and exhibits ionic conductivity due to the contained metal ions, and preferably contains lithium atoms and phosphorus atoms in addition to sulfur atoms, and more preferably contains lithium atoms, phosphorus atoms and halogen atoms, and has ionic conductivity due to lithium atoms.

[0163] The sulfide solid electrolyte may be an amorphous sulfide solid electrolyte or a crystalline sulfide solid electrolyte.

[0164] As an amorphous sulfide solid electrolyte, any electrolyte containing at least a sulfur atom and exhibiting ionic conductivity due to the contained metal ions can be used without particular restrictions. Typical examples include, for example, Li ２ S-P ２ S ５ A solid electrolyte composed of lithium sulfide and phosphorus sulfide, containing sulfur atoms, lithium atoms, and phosphorus atoms; Li ２ S-P ２ S ５ -LiI, Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ - A solid electrolyte composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiI-LiBr; further containing other elements such as oxygen and silicon, for example, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-P ２ S ５ - Solid electrolytes such as LiI are preferred. From the viewpoint of obtaining higher ionic conductivity, Li ２ S-P ２ S ５ -LiI, Li ２ S-P ２ S５ -LiCl, Li ２ S-P ２ S ５ - LiBr, Li ２ S-P ２ S ５ Solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as -LiI-LiBr, are preferred. The types of elements constituting the amorphous sulfide solid electrolyte can be confirmed, for example, by an ICP emission spectrometer.

[0165] The amorphous sulfide solid electrolyte contains at least Li ２ S-P ２ S ５ If it has Li ２ S and P ２ S ５ From the viewpoint of achieving high chemical stability and higher ionic conductivity, the molar ratio is preferably 65-85:15-35, more preferably 70-80:20-30, and even more preferably 72-78:22-28.

[0166] Amorphous sulfide solid electrolytes include, for example, Li ２ S-P ２ S ５ In the case of -LiI-LiBr, the total content of lithium sulfide and phosphorus pentasulfide is preferably 60 to 95 mol%, more preferably 65 to 90 mol%, and even more preferably 70 to 85 mol%. Furthermore, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, even more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0167] When the amorphous sulfide solid electrolyte contains lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms, the mixing ratio (molar ratio) of these atoms is preferably 1.0 to 1.8:1.0 to 2.0:0.1 to 0.8:0.01 to 0.6, more preferably 1.1 to 1.7:1.2 to 1.8:0.2 to 0.6:0.05 to 0.5, and even more preferably 1.2 to 1.6:1.3 to 1.7:0.25 to 0.5:0.08 to 0.4.

[0168] Furthermore, when bromine and iodine are used in combination as halogen atoms, the mixing ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine atoms, and iodine atoms is preferably 1.0 to 1.8:1.0 to 2.0:0.1 to 0.8:0.01 to 0.3:0.01 to 0.3, more preferably 1.1 to 1.7:1.2 to 1.8:0.2 to 0.6:0.02 to 0.25:0.02 to 0.25, more preferably 1.2 to 1.6:1.3 to 1.7:0.25 to 0.5:0.03 to 0.2:0.03 to 0.2, and even more preferably 1.35 to 1.45:1.4 to 1.7:0.3 to 0.45:0.04 to 0.18:0.04 to 0.18. By setting the mixing ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above range, it becomes easier to obtain a solid electrolyte with higher ionic conductivity having the thiolysicon region II type crystal structure described later.

[0169] Furthermore, there are no particular restrictions on the shape of the amorphous sulfide solid electrolyte, but particulate form is one example. The average particle size (D50) of the particulate amorphous sulfide solid electrolyte can be exemplified in the range of 0.01 μm to 500 μm and 0.1 to 200 μm. From the viewpoint of high ionic conductivity and easier filling of the pores of the nonwoven fabric, the average particle size (D50) of the amorphous sulfide solid electrolyte is preferably 0.01 to 15 μm, more preferably 0.1 to 10 μm, and even more preferably 0.3 to 5 μm.

[0170] In this specification, the average particle diameter (D50) is the particle diameter at which the sum of the particle diameters, starting from the smallest particle, reaches 50% of the total when plotting a particle diameter distribution integration curve, and the volume distribution is the average particle diameter that can be measured, for example, using a laser diffraction / scattering particle diameter distribution analyzer.

[0171] As the crystalline sulfide solid electrolyte, for example, it may be a so-called glass ceramic obtained by heating the above amorphous sulfide solid electrolyte above its crystallization temperature, and a sulfide solid electrolyte having the following crystal structure can be used.

[0172] The crystalline structure that a crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, and phosphorus atoms may have is Li ３ PS４ Crystal structure, Li ４ P ２ S ６ Crystal structure, argyrodite type crystal structure, Li ７ P ３ S １１ Examples include crystal structures, and crystal structures having peaks near 2θ = 20.2° and 23.6° (for example, Japanese Patent Publication No. 2013-16423).

[0173] Furthermore, the crystal structure that a crystalline sulfide solid electrolyte containing lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms may have is Li ４－ｘ Ge １－ｘ P ｘ S ４ The thio-LISICON Region II type crystal structure (see Kanno et al., Journal of The Electrochemical Society, 148(7) A742-746 (2001)), Li ４－ｘ Ge １－ｘ P ｘ S ４ Examples include the thio-LISICON Region II type and similar crystal structures (see Solid State Ionics, 177 (2006), 2721-2725). Here, "thio-LISICON Region II type crystal structure" refers to Li ４－ｘ Ge １－ｘ P ｘ S ４ Thio-Lisicon Region II type crystal structure, Li ４－ｘ Ge １－ｘ P ｘ S ４ This indicates that the crystal structure is similar to that of the thio-LISICON Region II system.

[0174] In X-ray diffraction measurements using CuKα rays, Li ３ PS ４ Diffraction peaks of the crystal structure appear, for example, around 2θ = 17.5°, 18.3°, 26.1°, 27.3°, and 30.0°, Li ４ P ２S ６ The diffraction peaks of the crystal structure appear, for example, around 2θ = 16.9°, 27.1°, and 32.5°, while the diffraction peaks of the argyrodite-type crystal structure appear, for example, around 2θ = 15.3°, 25.2°, 29.6°, and 31.0°, Li ７ P ３ S １１ Diffraction peaks of the crystal structure appear, for example, around 2θ = 17.8°, 18.5°, 19.7°, 21.8°, 23.7°, 25.9°, 29.6°, and 30.0°, Li ４－ｘ Ge １－ｘ P ｘ S ４ The diffraction peaks of the thio-LISICON Region II type crystal structure appear, for example, around 2θ = 20.1°, 23.9°, and 29.5°, Li ４－ｘ Ge １－ｘ P ｘ S ４ Diffraction peaks for crystal structures similar to the thio-LISICON Region II type appear, for example, around 2θ = 20.2° and 23.6°. Note that these peak positions may vary within a range of ±0.5°.

[0175] Furthermore, as an argyrodite-type crystal structure, for example, Li ７ PS ６ Crystal structure; Li ７ PS ６ Composition formula Li has a structural framework ７－ｘ P １－ｙ Si ｙ S ６ and Li ７＋ｘ P １－ｙ Si ｙ S ６ Crystal structure represented by (x is -0.6 to 0.6, y is 0.1 to 0.6); Li ７－ｘ－２ｙ PS ６－ｘ－ｙ Cl ｘ Crystal structure shown by (0.8 ≤ x ≤ 1.7, 0 < y ≤ -0.25x + 0.5); Li ７－ｘ PS ６－ｘ Ha ｘ Examples of crystal structures include those represented by (Ha is Cl or Br, and x is preferably 0.2 to 1.8).

[0176] Among the crystal structures described above, Li is an example of a crystal structure found in crystalline sulfide solid electrolytes. ３ PS ４ A crystal structure, a thiolysicon region II type crystal structure, and an argyrodite type crystal structure are preferred.

[0177] There are no particular restrictions on the shape of the crystalline sulfide solid electrolyte, but particulate form is one example. The average particle size (D50) of the particulate crystalline sulfide solid electrolyte can be exemplified in the same range as the average particle size (D50) of the amorphous sulfide solid electrolyte described above, for example, within the ranges of 0.01 μm to 500 μm and 0.1 to 200 μm.

[0178] From the viewpoint of having high ionic conductivity and being more easily filled into the pores of the nonwoven fabric, the average particle size (D50) of the amorphous sulfide solid electrolyte is preferably 0.01 to 15 μm, more preferably 0.1 to 10 μm, and even more preferably 0.3 to 5 μm.

[0179] Oxide solid electrolytes contain, for example, Li, Z (where Z is at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S), and O. Examples of oxide solid electrolytes include garnet-type solid electrolytes, perovskite-type solid electrolytes, NASICON-type solid electrolytes, Li-P-O-based solid electrolytes, and Li-B-O-based solid electrolytes. Examples of garnet-type solid electrolytes include Li ７ La ３ Zr ２ O １２ Li ７－ｘ La ３ (Zr ２－ｘ Nb ｘ ) O １２ (0≦x≦2), Li ５ La ３ Nb ２ O １２ Examples include (Li,La)TiO2. ３ , (Li, La)NbO ３ , (Li, Sr) (Ta, Zr) O ３ Examples include Li(Al,Ti)(PO ４ )３ , Li(Al,Ga)(PO ４ ) ３ Examples include Li-P-O solid electrolytes. ３ PO ４ ,LIPON (Li ３ PO ４ As a Li-B-O solid electrolyte, Li ３ BO ３ Li ３ BO ３ Examples include compounds in which part of the oxygen atom is replaced with carbon.

[0180] A hydride solid electrolyte comprises, for example, Li and a hydrogen-containing complex anion. Examples of complex anions include (BH ４ ) － , (NH ２ ) － , (AlH ４ ) － , (AlH ６ ) ３－ These are some examples.

[0181] A halogenated solid electrolyte is, for example, a compound containing Li, M, and X. Here, M is at least one selected from the group consisting of metallic elements and metalloid elements other than Li. X is at least one selected from the group consisting of F, Cl, Br, and I. The "metalloid elements" are B, Si, Ge, As, Sb, and Te. The "metallic elements" are all elements in groups 1 to 12 of the periodic table (except hydrogen), and all elements in groups 13 to 16 of the periodic table (except B, Si, Ge, As, Sb, Te, C, N, P, O, S, and Se). To improve the ionic conductivity of the halogenated solid electrolyte, M may also contain Y. A halogenated solid electrolyte is, for example, Li ａ Me ｂ Y ｃ X ６The compound may be represented by the following equation: where the equation a + mb + 3c = 6 and c > 0 is satisfied. The value of m represents the valence of Me. To improve the ionic conductivity of the halide solid electrolyte, Me may be at least one selected from the group consisting of Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb. To improve the ionic conductivity of the halide solid electrolyte, X may include at least one selected from the group consisting of Cl and Br. The halide solid electrolyte may be, for example, Li ３ YCl ６ and Li ３ YBr ６ It may include at least one selected from the group consisting of the following.

[0182] Examples of nitrogenized solid electrolytes include Li ３ Examples include N.

[0183] <Method for Forming Solid Electrolyte> In the solid-state secondary battery of the present invention, the method for forming the solid electrolyte is not particularly limited, but can be appropriately selected depending on the type of electrolyte and the battery form. Examples of methods for forming the solid electrolyte include a coating method in which a slurry containing the solid electrolyte is directly applied to the positive electrode layer and / or the negative electrode layer and dried, a transfer method in which a slurry containing the solid electrolyte is applied to a release film, dried, and then transferred to the positive electrode layer and / or the negative electrode layer, and a method for producing a self-supporting film by impregnating a nonwoven fabric or the like with the solid electrolyte. In the case of an all-solid-state secondary battery, examples include a compaction and lamination method using a sulfide-based solid electrolyte, a green sheet firing method using an oxide-based solid electrolyte, and the aforementioned coating method. Furthermore, in the case of semi-solid secondary batteries and quasi-solid secondary batteries, examples of methods for forming electrolyte layers include coating methods in which a slurry containing a solid electrolyte is directly applied to the positive electrode layer and / or the negative electrode layer and dried; methods in which the positive electrode active material and / or the negative electrode active material are pre-mixed with a solid electrolyte powder to form an electrode-solid electrolyte composite layer; in-situ solidification (polymerization) methods in which a liquid precursor is impregnated after electrode stacking and a solid electrolyte layer (gel electrolyte layer) is formed inside the cell by heat, light, electrochemical reactions, etc.; and film formation of polymer-based solid electrolyte films.

[0184] When using the coating method for forming electrodes in an all-solid-state secondary battery, a slurry prepared by adding a solid electrolyte and a binder to a solvent and mixing them can be used. Examples of methods for mixing the slurry include using general mixing equipment such as a dissolver, homomixer, kneader, roll mill, sand mill, attritor, ball mill, vibrator mill, high-speed impeller mill, ultrasonic homogenizer, and shaker.

[0185] It is preferable to use a solvent for the slurry that does not easily degrade the solid electrolyte. In particular, sulfide solid electrolytes and hydride solid electrolytes undergo chemical changes and compositional changes with even trace amounts of water, so it is preferable to use nonpolar aprotic solvents such as hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene, or esters such as butyl butyrate and ethyl acetate, ethers such as dibutyl ether, ketones such as diisobutyl ketone (DIBK), methyl ketone, and methyl propyl ketone, or amines such as tributylamine and allylamine. The proportion of solvent in the slurry is, for example, 60 parts by mass or more and 300 parts by mass or less, when the solid component of the slurry is 100 parts by mass.

[0186] The positive electrode layer is an electrode layer containing a positive electrode active material that releases lithium ions during charging and absorbs lithium ions during discharge. Examples of positive electrode active materials include oxides, sulfides, and phosphorus oxides containing at least one metallic element selected from manganese (Mn), cobalt (Co), nickel (Ni), iron (Fe), molybdenum (Mo), vanadium (V), and tungsten (W). Specifically, MoO ｘ WO ｘ , VO ｘ Li ｘ CoO ｙ (LiCoO ２ etc.), Li ｘ MnO ｙ (LiMnO ２ LiMn ２ O ４ etc.), Li ｘ NiO ｙ (LiNiO ２ etc.), Liｘ VO ｙ (LiVO ２ etc.), Li ｘ Mn ｙ Ni ｚ Co ｗ O(LiNi １／３ Co １／３ Mn １／３ O ２ etc.), Li ｘ FeP ｘ O ｙ (LiFePO) ４ etc.), Li ｘ MnP ｘ O ｙ (LiMnPO) ４ etc.), Li ｘ NiP ｘ O ｙ (LiNiPO) ４ etc.), Li ｘ Cup ｘ O ｙ (LiCuPO) ４ etc.), MoS ｘ CuS ｘ TiS ｘ WS ｘ Li ｘ S ｙ Li ｘ P ｙ S ｚ Examples include the above. Furthermore, the positive electrode layer may be a composite positive electrode layer containing a solid electrolyte, a conductive additive, etc.

[0187] The negative electrode layer is an electrode layer containing a negative electrode active material that absorbs lithium ions during charging and releases lithium ions during discharge. The negative electrode active material may include carbon materials; metals such as lithium (Li), indium (In), aluminum (Al), silicon (Si), or alloys containing these; and Sn ｘ O ｙ MoO ｘ WO ｘ Li ｘ CoO ｙ (LiCoO ２ etc.), Li ｘ Mn ｙ Ni ｚ Co ｗ O(LiNi １／３ Co １／３ Mn１／３ O ２ etc.), Li ｘ Cup ｘ O ｙ (LiCuPO) ４ Examples include oxides such as (etc.). Furthermore, the negative electrode layer may be a composite negative electrode layer further containing a solid electrolyte, a conductive additive, etc.

[0188] The above-mentioned conductive additive can consist of carbon materials, metal powders, metal compounds, etc., of which carbon materials are preferred. Examples of carbon materials include plate-like conductive materials such as graphene; linear conductive materials such as carbon nanotubes and carbon fibers; carbon blacks such as Ketjenblack, acetylene black, thermal black, and channel black; and granular conductive materials such as graphite.

[0189] The following describes, with examples, a method for manufacturing a sulfide-based all-solid-state lithium secondary battery by coating using the resin film of the present invention as a resin current collector for a bipolar battery. However, the present invention is not limited to the product obtained by such examples. The sulfide-based all-solid-state lithium secondary battery in such examples comprises at least a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer.

[0190] Since sulfide-based solid electrolytes have a tendency to react readily with moisture, the following steps are preferably carried out in a dry atmosphere, such as an inert gas atmosphere like an argon atmosphere or a nitrogen atmosphere.

[0191] (Preparation of Sulfide-Based Solid Electrolyte Slurry) As the sulfide solid electrolyte, for example, the sulfide solid electrolyte described above can be used. The sulfide-based solid electrolyte slurry is prepared by mixing and dispersing the sulfide solid electrolyte powder with a solvent and, if necessary, a binder. As the solvent, it is preferable to use a solvent that does not react easily with the sulfide-based solid electrolyte, for example, a hydrocarbon solvent can be used. As the binder, a resin that can impart binding properties to the solid electrolyte particles can be used.

[0192] (Preparation of positive electrode slurry) The positive electrode slurry contains a positive electrode active material, a sulfide-based solid electrolyte, and, if necessary, a conductive additive and a binder. The positive electrode slurry is prepared by mixing and dispersing these materials in a solvent. By including a sulfide-based solid electrolyte in the positive electrode slurry, the interfacial resistance between the positive electrode active material particles and the solid electrolyte can be reduced.

[0193] Examples of positive electrode active materials include oxides, sulfides, and phosphorus oxides containing at least one metallic element selected from manganese (Mn), cobalt (Co), nickel (Ni), iron (Fe), molybdenum (Mo), vanadium (V), and tungsten (W). Specifically, MoO ｘ WO ｘ , VO ｘ Li ｘ CoO ｙ (LiCoO ２ etc.), Li ｘ MnO ｙ (LiMnO ２ LiMn ２ O ４ etc.), Li ｘ NiO ｙ (LiNiO ２ etc.), Li ｘ VO ｙ (LiVO ２ etc.), Li ｘ Mn ｙ Ni ｚ Co ｗ O(LiNi １／３ Co １／３ Mn １／３ O ２ etc.), Li ｘ FeP ｘ O ｙ (LiFePO) ４ etc.), Li ｘ MnP ｘ O ｙ (LiMnPO) ４ etc.), Li ｘ NiP ｘ O ｙ (LiNiPO) ４ etc.), Li ｘ Cup ｘ O ｙ (LiCuPO) ４etc.), MoS ｘ CuS ｘ TiS ｘ WS ｘ Li ｘ S ｙ Li ｘ P ｙ S ｚ These are some examples.

[0194] (Preparation of negative electrode slurry) The negative electrode slurry contains a negative electrode active material, a sulfide-based solid electrolyte, and, if necessary, a conductive additive and a binder. The negative electrode slurry is prepared by mixing and dispersing these materials in a solvent.

[0195] The negative electrode active material may be carbon material; metals such as lithium (Li), indium (In), aluminum (Al), silicon (Si), or alloys containing these; or Sn ｘ O ｙ MoO ｘ WO ｘ Li ｘ CoO ｙ (LiCoO ２ etc.), Li ｘ Mn ｙ Ni ｚ Co ｗ O(LiNi １／３ Co １／３ Mn １／３ O ２ etc.), Li ｘ Cup ｘ O ｙ (LiCuPO) ４ Examples include oxides such as (etc.). Furthermore, the negative electrode layer may be a composite negative electrode layer further containing a solid electrolyte, a conductive additive, etc.

[0196] The above-mentioned conductive additive can consist of carbon materials, metal powders, metal compounds, etc., of which carbon materials are preferred. Examples of carbon materials include plate-like conductive materials such as graphene; linear conductive materials such as carbon nanotubes and carbon fibers; carbon blacks such as Ketjenblack, acetylene black, thermal black, and channel black; and granular conductive materials such as graphite.

[0197] (Formation of electrodes for bipolar batteries) The following describes, with examples, how to form electrodes for bipolar batteries when a current collector is used that has an aluminum layer on one surface of a resin film and copper on the opposite surface. However, the present invention is not limited to what can be obtained by such examples.

[0198] The slurry for the positive electrode obtained by the above method is applied to one side (aluminum layer side) of the resin current collector for the bipolar battery, and the solvent is dried to form the positive electrode layer.

[0199] In the resin current collector for the bipolar battery, the negative electrode slurry obtained by the above method is applied to the side on which the positive electrode layer is not formed (the copper layer side), and the solvent is dried to form the negative electrode layer.

[0200] In this way, by forming a positive electrode layer and a negative electrode layer on both sides of the same resin current collector, an electrode for a bipolar battery can be obtained.

[0201] (Formation of Solid Electrolyte Layer) The solid electrolyte slurry is applied to the electrode for the bipolar battery, which has a positive electrode layer and a negative electrode layer formed on both sides of the resin current collector. The coating surface is applied to the surface of the positive electrode layer and / or the surface of the negative electrode layer, and the solvent is dried to form a solid electrolyte layer. As a coating method, the doctor blade method, slot die method, bar coater method, etc. can be used.

[0202] Multiple bipolar electrodes obtained in (4) above are prepared and stacked so that the units of positive electrode layer / solid electrolyte layer / negative electrode layer are repeated via the resin current collector for the bipolar battery.

[0203] (Restraining Member) The all-solid-state secondary battery of the present invention may be equipped with a restraining member. The restraining member applies restraining pressure in the thickness direction to the positive electrode, solid electrolyte layer, and negative electrode. The restraining pressure is preferably 0.1 MPa or more, more preferably 1 MPa or more, and even more preferably 5 MPa or more. By setting it within the above range, the generation of gaps due to the expansion and contraction of electrodes that occur during charging and discharging can be suppressed, and the battery performance can be maintained. The restraining pressure is preferably 100 MPa or less, more preferably 50 MPa or less, and even more preferably 20 MPa or less. The restraining pressure is preferably 0.1 MPa or more and 100 MPa or less.

[0204] (Forms of All-Solid-State Rechargeable Batteries) The forms of all-solid-state rechargeable batteries are not limited to those generally referred to as coin-type batteries or button-type batteries. For example, they may have an outer casing made of a resin film or a metal-resin laminate film, or an outer casing made of metal with a bottomed cylindrical (cylindrical or rectangular) outer casing and a sealing structure that seals its opening.

[0205] (Electric Vehicles) The secondary batteries produced by the methods described above are one of the preferred forms for use in electric vehicles due to their excellent battery characteristics and durability. An electric vehicle is a vehicle that receives part or all of the driving energy required for driving from a secondary battery. Examples of electric vehicles include BEVs (Battery Electric Vehicles) equipped only with secondary batteries, HEVs (Hybrid Electric Vehicles) and PHEVs (Plug-in Hybrid Electric Vehicles) equipped with both fossil fuels such as gasoline and secondary batteries. The secondary batteries of the present invention can be suitably used in any of these applications.

[0206] (Electric Flying Vehicles) The secondary batteries produced by the methods described above are one of the preferred forms for mounting on electric flying vehicles due to their excellent battery characteristics and durability. An electric flying vehicle is a vehicle that receives part or all of the necessary driving energy for flight from a secondary battery. Specifically, examples include drones, stratospheric communication platform aircraft (HAPS), air metro, and electric aircraft such as air taxis. The secondary batteries of the present invention can be suitably used in any of these applications.

[0207] (Electronic Devices) The secondary batteries produced by the methods described above are one of the preferred forms for use in electronic devices due to their excellent battery characteristics and durability. Electronic devices are devices that receive part or all of the power necessary for their operation from a secondary battery. Specifically, examples include portable electronic devices such as smartphones, tablet devices, laptop computers, personal digital assistants, wearable devices, smartwatches, and wireless earphones. Digital cameras, video cameras, portable game consoles, remote controllers, various sensor terminals, IoT devices, medical electronic devices, and industrial electronic devices are also included. The secondary batteries of the present invention can be suitably used in any of these applications.

[0208] [Method for evaluating properties] A. Film thickness (i) Resin film thickness T The total thickness of the resin film is measured at five arbitrary locations with 10 layers of film stacked, using a dial gauge in accordance with JIS K7130 (1992) A-2 method. The average value is divided by 10 to obtain the film thickness T (μm).

[0209] (ii) Lamination thickness (T Ｐ１ , T Ｐ２ , T Ｍ) The cross-section of the resin film is cut with a microtome in a direction parallel to the film width direction. After sputtering the cross-section with platinum-palladium, it is observed at a magnification of 5000 to 20000 times under the condition of applying an accelerating voltage of 3 kV using a scanning electron microscope (JEOL Ltd., JSM-6700) to determine the thickness ratio of the layers (P1 layer, P2 layer) and the metal and / or metal compound layer (M layer) that constitute the laminated polyolefin film. From the determined lamination ratio and the total film thickness obtained in item (i) above, the thickness of each layer (T Ｐ１ , T Ｐ２ , T Ｍ Calculate the result.

[0210] B. After sputtering the surface of the resin film of the constituent elements of the M layer with platinum-palladium, the metallic elements are identified using a scanning electron microscope (JEOL Ltd., JSM-6700) and its equipped energy-dispersive X-ray spectroscopy (EDX) detector (Oxford Corp., AZtecLiv Standard UltimMax65).

[0211] Measurements are performed by varying the acceleration voltage from 0.5 kV to 30 kV, and the detected elements are considered to be the elements constituting the metal and / or metal compound layer (M layer). In this process, platinum and palladium are excluded, and if only platinum or palladium is detected through measurements at all acceleration voltages, these are considered to be the elements constituting the metal and / or metal compound layer (M layer).

[0212] C. Distribution evaluation of the low-resistance region <1 × 10 ８ Standard deviation of the area of ​​the Voronoi region formed by low-resistance regions below Ω > Using a scanning spreading resistance microscope (hereinafter sometimes referred to as SSRM), a voltage of +1V (DC Sample Bias) is applied from the back side of the sample, and the resistance map of a 30 μm × 30 μm region on the surface of the sample is observed using a probe. The equipment and observation conditions used are as follows.

[0213] Observation equipment: Bruker NanoScope V Dimension Icon. Sample preparation: Embedding in epoxy resin, followed by cross-section preparation using an Ar ion beam. (Processing equipment: IB-19520CCP cooled cross-section polisher) ＴＭ Cross-sectional sample preparation apparatus Measurement environment: Room temperature, high-purity Ar gas atmosphere Scanning mode: Contact mode and simultaneous measurement of spreading resistance Scanning speed: 0.6 Hz Probe: DDESP-FM-V2

[0214] The cross-sectional image of the resin film obtained by the above method was analyzed using image analysis software (ImageJ, manufactured by the National Institutes of Health, USA) as follows: 1 × 10 ８ Extraction of low-resistance regions of Ω or less, calculation of the standard deviation of the area of ​​the low-resistance regions, and 1 × 10⁻¹⁰ ８ The aspect ratio in the low-resistance region (below ohm) is calculated.

[0215] (Image Analysis Conditions) (i) Preprocessing After the cross-sectional image is captured by the software, 8-bit grayscale processing is performed by executing the 8-bit command under 'Type' in the 'Image' menu. Next, a straight line with a known distance is drawn using the 'Straight' menu, and the scale of the captured image is set using the 'Set Scales' command under the 'Analyze' menu. At this time, 'Unit of length' is set to 'nm'. After that, the 'Subtract' command under 'Math' in the 'Process' menu is used, and 'Value' is subtracted by 25. Using the 'Enhance Contrast' command from the 'Process' menu, 'Saturated pixels' is set to 5%, 'Normalize' is checked, and the 'OK' button is pressed. From the 'Process' menu, select 'Filters' and then the 'Gaussian Blur' command, setting 'Sigma (Radius)' to 1 to apply the blur effect.

[0216] (ii) Binarization From the 'Image' menu, select 'Adjust' and then 'Threshold', check only 'Dark background' and 'Don't reset range', press 'Auto', and then press 'Apply'.

[0217] (iii) Noise Reduction From the 'Process' menu, select 'Noise' and then the 'Remove Outliers' command. Set 'Radius' to 1, 'Threshold' to 50, and 'Which Outliers' to Bright, then press the 'OK' button.

[0218] (iv) Voronoi region From the 'Process' menu, select 'Voronoi' under 'Binary'. Next, from the 'Image' menu, select 'Threhold' under 'Adjust', set both scale bars to 0, check only 'Dark background' and 'Don't reset range', and press 'Apply'.

[0219] (v) Voronoi domain analysis conditions In the "Analyze" menu, use the "Set Measurements" command, check "Area" and "Ferret's diameter", and press the "OK" button. Next, in the "Analyze" menu, use the "Analyze Particles" command, set each item as follows, and press the "OK" button to display the analysis results (Results).

[0220] • Size: 0-Infinity • Circulation: 0.00-1.00 • Show: Nothing • Check the boxes for 'Display Results', 'Clear Results', 'Exclude on edges', and 'include holes'.

[0221] The 'Area' in the obtained results is the area A of the Voronoi region formed by each low-resistance region. From this value, the standard deviation s of the area of ​​the Voronoi region formed by the low-resistance regions is calculated using equation 3 below.

[0222]

[0223] <1 x 10 ８ The average value of the aspect ratio in the low resistance region of Ω or less > The above, < 1 × 10 ８For the cross-sectional image of the resin film obtained by <<1 × 10 ８ The standard deviation of the area of ​​the Voronoi region formed by low-resistance regions of Ω or less > (image analysis conditions) is obtained by performing the processes (i), (ii), and (iii) of 1 × 10 ８ An image is obtained in which the low-resistance region of less than Ω is extracted. The image in which the low-resistance region is extracted is then divided into <1 × 10⁻¹⁰ ８ By executing the process "Standard deviation of the area of ​​the Voronoi region formed by low-resistance regions below Ω > (image analysis conditions) (iv)", the analysis results (Results) are displayed.

[0224] (1 x 10 ８ (Aspect ratio in the low resistance region of Ω or less) From the obtained results, 1 × 10 ８ Determine the aspect ratio in the low-resistance region below Ω. The aspect ratio is calculated by dividing the 'Feret' of each particle in the Results by 'MinFeret'. For each of the five different fields of view, 1 × 10⁻¹⁰ ８ Determine the aspect ratio in the low-resistance region of Ω or less, and take the average of 5 fields of view for 1 × 10⁻¹⁰ of the resin film. ８ This is the average aspect ratio in the low-resistance region of Ω or less.

[0225] D. Particle Dispersion Evaluation <Method for measuring the area of ​​each particle> Cross-sectional images at an observation magnification of 3500x using a scanning electron microscope (JEOL Ltd., JSM-6700) are analyzed using image analysis software (National Institutes of Health, ImageJ) as follows.

[0226] (Image analysis conditions) (i) After importing the pre-processing cross-sectional image into the software, perform 8-bit grayscale processing by executing the "8-bit" command under "Type" from the "Image" menu. Next, draw a straight line with a known distance in the "Straight" menu, and set the scale of the imported image using the "Set Scale" command in the "Analyze" menu. Then, use the "Subtract" command under "Math" from the "Process" menu to perform subtraction with "Value" set to 30. Via the "Enhance Contrast" command from the "Process" menu, set "Saturated pixels" to 5%, check "Normalize", and press the "OK" button. Perform blurring processing via the "Gaussian Blur" command under "Filters" from the "Process" menu with "Sigma (Radius)" set to 1.

[0227] (ii) Binarization Select "Threshold" under "Adjust" from the "Image" menu, check only "Dark background" and "Don't reset range", press "Auto" and then "Apply".

[0228] (iii) Noise removal Via the "Remove Outliers" command under "Noise" from the "Process" menu, set "Radius" to 1, "Threshold" to 50, "Which Outliers" to Bright, and press the "OK" button.

[0229] (iv) Particle analysis conditions Via the "Set Measurements" command in the "Analyze" menu, check "Area" and "Feret's diameter", and press the "OK" button. Next, via the "Analyze Particles" command in the "Analyze" menu, set each item as follows, and press the "OK" button to display the analysis results (Results).

[0230] ・Size: 0-Infinity ・Circularity: 0.00-1.00 ・Show: Nothing ・Check and select "Display Results", "Clear Results", "Exclude on edges" and "include holes"

[0231] From the obtained Results, the average area of particles and the area of particles is 0.10 μm ２ The proportion of the number of particles with the above-specified area is determined.

[0232] (Average area of particles) The average value of the area is calculated according to the following formula 4 using the "Area" of each particle detected above. The average area is obtained for five different fields of view, and the average value of these is taken as the average area S (μm) of particles in the sample.

[0233] S (μm ２ ) = Σ(Area) / number of particles ・・・Formula 4

[0234] (Proportion of the number of particles with particle area of 0.10 μm ２ or greater) The "Area" of each particle detected as described above is taken as the area of each particle. Among the detected particles, the particle area is 0.10 μm ２ or greater, count the number of such particles, and according to the following formula 5, when the particle area is 0.10 μm ２ determine the proportion R of the number of particles with the above-specified area.

[0235] R (%) = (number of particles with area of 0.10 μm ２ or greater) / total number of particles × 100 (%) ・・・Formula 5

[0236] E. Method for determining particle aspect ratio and the existence ratio of C1 relative to C2 The particle aspect ratio is determined by the method described below. Subsequently, the total area (SC1) of conductive particles (conductive particles C1) present in the region with aspect ratio of 1 or more and less than 5, and the total area (SC2) of conductive particles (conductive particles C2) present in the region with aspect ratio of 10 or more are determined. The existence ratio of C1 relative to C2 is calculated by determining the ratio of the area (SC1) occupied by the conductive particles C1 to the area (SC2) occupied by the conductive particles C2 contained in the resin film.

[0237] <Method for measuring the area occupied by each conductive particle> A cross-sectional image in the width direction and thickness direction, observed at a magnification of 10,000x using a scanning electron microscope (JEOL Ltd., JSM-6700), is analyzed using image analysis software (National Institutes of Health, ImageJ) as follows.

[0238] (Image Analysis Conditions) (i) Preprocessing After the cross-sectional image is captured by the software, 8-bit grayscale processing is performed by executing the 8-bit command under 'Type' in the 'Image' menu. Next, a straight line with a known distance is drawn using the 'Straight' menu, and the scale of the captured image is set using the 'Set Scales' command under the 'Analyze' menu. After that, the 'Subtract' command under 'Math' in the 'Process' menu is used to subtract with 'Value' set to 30. Using the 'Enhance Contrast' command from the 'Process' menu, 'Saturated pixels' is set to 5%, 'Normalize' is checked, and the 'OK' button is pressed. From the 'Process' menu, select 'Filters' and then the 'Gaussian Blur' command, setting 'Sigma (Radius)' to 1 to apply the blur effect.

[0239] (ii) Binarization From the 'Image' menu, select 'Adjust' and then 'Threshold', check only 'Dark background' and 'Don't reset range', press 'Auto', and then press 'Apply'.

[0240] (iii) Noise Reduction From the 'Process' menu, select 'Noise' and then the 'Remove Outliers' command. Set 'Saturated pixels' to 1 pixel, 'Threshold' to 50, and 'Which Outliers' to Bright, then press the 'OK' button.

[0241] (iv) Particle analysis conditions In the "Analyze" menu, use the "Set Measurements" command, check "Area" and "Feret's diameter", and press the "OK" button. Next, in the "Analyze" menu, use the "Analyze Particles" command, set each item as follows, and press the "OK" button to display the analysis results (Results).

[0242] • Size: 0-Infinity • Circulation: 0.00-1.00 • Show: Nothing • Check the boxes for 'Display Results', 'Clear Results', 'Exclude on edges', and 'include holes'.

[0243] From the obtained results, the aspect ratio and area of ​​each particle are determined. The aspect ratio is calculated by dividing the 'Feret' value of each particle in the Results by 'MinFeret'. The area is the 'Area' value of each particle.

[0244] (Particle Size of Conductive Particles) Using the 'Feret' value of each particle detected above, the volume-based average particle size is determined according to Equation 6 below. The value of 'Feret' is the particle size of conductive particles as defined herein. The volume-based average particle size is determined for five different fields of view, and their average value is taken as the volume-based average particle size R (μm) of the particles in the sample. R is the average particle size as defined herein.

[0245] R (μm) = (Σ (Ferret) ２ (× number) / (Σ(Feret) × number) ... Equation 6

[0246] (Aspect ratio of conductive particles, and the ratio of C1 to C2) For five different fields of view, the obtained aspect ratios are plotted on the horizontal axis in increments of 0.5 for intervals between 1 and 10, and in increments of 10 for intervals of 10 or more, to create a count histogram. If a maximum value exists in the region where the aspect ratio is between 1 and 5 in the count histogram, the minimum value of the interval showing that maximum value (for example, if the interval between 2 and 2.5 is the maximum value, 2 is adopted as the maximum value) is taken as the aspect ratio of conductive particles (conductive particles C1) present in the region where the aspect ratio is between 1 and 5. If there are multiple maximum peaks in the region where the aspect ratio is between 1 and 5, the weighted average value using their vertical axis values ​​is taken as the aspect ratio of conductive particles (conductive particles C1) present in the region where the aspect ratio is between 1 and 5.

[0247] Similarly, if a maximum value exists in the region where the aspect ratio is 10 or greater, that maximum value is taken as the aspect ratio of the conductive particles (conductive particles C2) present in the region where the aspect ratio is 10 or greater. If multiple maximum peaks exist in the region where the aspect ratio is 10 or greater, the weighted average value using their vertical axis values ​​is taken as the aspect ratio of the conductive particles (conductive particles C2) present in the region where the aspect ratio is 10 or greater.

[0248] For each of the five different fields of view, the aspect ratios of conductive particles (conductive particles C1) located in the region with an aspect ratio of 1 or more and less than 5, and conductive particles (conductive particles C2) located in the region with an aspect ratio of 5 or more are determined, and the average value of the five fields of view in each region is taken as the aspect ratio of conductive particles C1 and conductive particles C2 in the resin film.

[0249] The sum of the areas (SC1) of conductive particles (conductive particle C1) located in the region with an aspect ratio of 1 or more and less than 5, as confirmed in the aforementioned histogram, is calculated. Next, the sum of the areas (SC2) of conductive particles (conductive particle C2) located in the region with an aspect ratio of 10 or more is calculated, and SC1 / SC2 is determined as the ratio of C1 to C2. Note that the area ratio can be determined using the same measurement method regardless of whether the conductive particles are metal particles or carbon particles.

[0250] F. A 90 mm x 90 mm square sample of a resistivity resin film, or a current collector having an M layer on both surfaces of the resin film, is sampled to create an evaluation sample. The measurement position for resistivity is determined by dividing the 90 mm x 90 mm square into nine 30 mm x 30 mm squares in a 3 x 3 grid, with the center of each square being the measurement position. From both sides of the sample, each measurement position is sandwiched between circular copper electrodes with a diameter of 20 mm and a thickness of 10 mm, equipped with electrode tabs, and a pressure of 1.5 MPa is applied in the thickness direction of the sample. The electrode tabs are connected to a Texio GOM-805 milliohmmeter, and the value is read one minute after the resistance value is displayed under DC +6.25 V conditions. The obtained resistance value is multiplied by the electrode area (3.14 cm²). ２ Multiply by ( ) and divide by the sample thickness (cm) to obtain the penetration resistivity (Ωcm). Perform the same measurement at nine measurement positions to obtain the penetration resistivity, and take the average of these values ​​as the average penetration resistivity of the sample.

[0251] The coefficient of variation (CV) of the resistivity is calculated using the following equation 7, with the mean value α and standard deviation σ of the resistivity at the nine measurement locations obtained by the method described above.

[0252] CV=σ / α...Formula 7

[0253] G. Measurement Method of Glass Transition Temperature (Tg) The glass transition temperature (Tg) was measured in accordance with JIS K 7121-1987. Using a differential scanning calorimeter (Rigaku Thermoplus EVO2 DSCvesta), 3 mg of film or resin was heated from 30°C to 300°C at a rate of 20°C / min in a nitrogen atmosphere, then held at 300°C for 5 minutes, and then cooled to -130°C at a rate of 20°C / min. After holding at 20°C for 5 minutes, the temperature was raised again from -130°C to 300°C at a rate of 20°C / min. The glass transition temperature (Tg) was calculated from the DSC curve obtained during the reheating process using the following equation 8.

[0254] Glass transition temperature = (Extracorporeal glass transition start temperature + Extracorporeal glass transition end temperature) / 2 ... Equation 8

[0255] H. Measuring the melting point (Tm) and heat of fusion (ΔHm): Using a differential scanning calorimeter (DSC) such as a Rigaku Thermo Plus Evo2 series DSC Vesta, approximately 5 mg of the sample was placed on an aluminum tray and heated from room temperature to 300°C at a heating rate of 20°C / min, holding for 5 minutes (1st Run measurement). The amount of heat at the endothermic peak of melting observed at that time was defined as the heat of fusion (ΔHm), and the temperature of the endothermic peak was defined as the melting point (Tm). This measurement was repeated three times, and the average values ​​of the measurements were defined as the heat of fusion (ΔHm) and melting point (Tm) of the sample.

[0256] If it is difficult to distinguish the minute endothermic peak Tmeta that appears just below the melting point temperature in the DSC chart of the film, perform the following measurement in addition to the 1st Run measurement described above. Heat the film to 300°C at a heating rate of 20°C / min and hold for 5 minutes, then rapidly cool it using liquid nitrogen, and heat it again to 300°C at a heating rate of 20°C / min (2nd Run measurement). Check the number and temperature of the melting point peaks, and identify the peaks that have disappeared from the 1st Run measurement as the minute endothermic peak Tmeta that appears just below the melting point temperature, and exclude them from the 1st Run measurement data.

[0257] I. Carbon content and identification of carbon species (i) Amount of carbon material added (when the resin is polyolefin) Using a thermogravimetric analyzer (Shimadzu DTG-60), 10 g of the film of the present invention is heated to 600°C at 5°C / min under a nitrogen atmosphere (nitrogen flow rate: 300 ml / min). After cooling, the weight of the resulting residue is divided by the weight of the original film to determine the content of conductive particles contained in the film of the present invention.

[0258] (When the resin is polyester) The P1 or P2 layer portion of the film of the present invention is immersed in 200 ml of hexafluoroisopropanol (HFIP) to dissolve the polyester resin. 200 ml of water is added to the dissolved solution, and the liquid is then centrifuged to allow the particles to settle, and the supernatant is removed. The particles are then washed with water, and the centrifugation process is repeated twice. The particles obtained in this way are dried, and their mass is measured to calculate the particle content (mass %) in each layer. The above procedure is performed on three different locations of the polyester film of the present invention, and the resulting particle content is taken as the conductive particle content of the sample.

[0259] If multiple types of carbon materials are identified as conductive materials through the identification analysis described in section (ii) below, the concentration of each carbon material will be determined using the relative abundance of the carbon materials observed in section (ii) below.

[0260] (ii) Identification of carbon species The carbon particles obtained in item 1 above are analyzed by Raman spectroscopy to determine the graphite structure (sp) commonly referred to as the G band. ２ 1580 cm (derived from the combination) －１ The vicinity, and the diamond structure commonly referred to as the D band (sp ３ 1350 cm (derived from the combination) －１ Nearby peaks are observed, and identification is performed based on the ratio of their peak intensities. During identification, the results are compared with known Raman spectrum databases and peak intensity data obtained by measuring commercially available carbon materials. The carbon material is observed using a transmission electron microscope (TEM) at 50,000 to 500,000x magnification, and its shape is observed. This, combined with the Raman spectroscopy results from the previous section, is used to identify the type of carbon material present in the sample. If multiple carbon materials are observed, the number of each carbon material observed by the TEM is converted to a volume ratio, and this value is used as the abundance ratio of each carbon material.

[0261] J. Evaluation of mechanical properties of resin film The F5 value of a resin film (the value obtained by dividing the load value when a test piece elongates by 5% by the cross-sectional area of the test piece) and the elongation at break are measured. A sample was cut from a resin film into a rectangular shape with a length of 150 mm and a width of 10 mm such that the unrolling direction of the roll was defined as the longitudinal direction of the resin film and the longitudinal direction corresponded to the long side of the rectangle. In accordance with the following method specified in ASTM-D882, using an Instron-type tensile tester (AMF / RTA-100 manufactured by Orientec Co., Ltd.), a sample film with a width of 10 mm was set so that the distance between chucks was 50 mm, a tensile test was performed at a tensile speed of 300 mm / min, and the F5 value and elongation at break were read. The measurement is performed 5 times, and the average value thereof is taken as the F5 value and elongation at break in the longitudinal direction of the resin film.

[0262] In the same manner as the measurement in the longitudinal direction, the direction obtained by rotating the longitudinal direction of the resin film by 90° in the plane is defined as the width direction, and the F5 value and elongation at break of a sample cut into a rectangular shape with a length of 150 mm and a width of 10 mm such that the width direction corresponds to the long side are measured. The measurement is performed 5 times, and the average value thereof is taken as the F5 value and elongation at break in the width direction of the resin film.

[0263] When the longitudinal direction and width direction of the resin film are unclear, the F5 value and elongation at break are measured for a total of 4 directions: a specific direction and directions rotated by 45°, 90°, and 135° in the plane from the specific direction. The maximum value of the obtained F5 values in the four directions is taken as the F5 value of the longitudinal direction and the F5 value of the resin film whose longitudinal direction is unclear. Similarly, the maximum value of the obtained elongations at break in the four directions is taken as the elongation at break of the longitudinal direction and the elongation at break of the resin film whose longitudinal direction is unclear.

[0264] K. Adhesion between M layer and resin film A sample provided with an M layer formed on the surface of a resin film is cut into a rectangular shape of 15 mm width × 80 mm length. As a peeling tape, Nitto Cellophane Tape No. 29 (tape width: 15 mm) is attached to the M layer of the cut sample, brought into close contact using a 2 kg rubber roller, and conditioned for 1 day at 23°C and 65% RH.

[0265] After humidity adjustment, a 180° peel test is performed on the sample using a tack / film peel analyzer (VPA-2) manufactured by Kyowa Interface Science Co., Ltd. under the following conditions. After fixing the side of the humidity-adjusted sample opposite to the tape application side to the apparatus, the end of the peel tape is fixed to the load cell of the apparatus and measured.

[0266] (Peel test conditions) ・Peel angle: 180° ・Tape width: 15 mm ・Peel speed: 25 mm / min ・Initial peel force: 0 N ・Measurement distance: 50 mm

[0267] From the obtained peel force waveforms, the average value of the peel force (N / 15mm) in the travel distance range of 15mm to 35mm is calculated. The peel force is measured for three different samples, and the average value of these measurements is taken as the adhesion between the M layer and the resin film.

[0268] [Method for evaluating application characteristics] L. Discharge stability: In the manufacturing process of the resin film, a 10m roll of unstretched film is taken from the unstretched film obtained by melt extrusion from a die and cooling in a cast drum using an electrostatic application method.

[0269] For the obtained unstretched film roll, the thickness of the unstretched film is measured every 50 cm in the winding direction. The average of all measured values ​​is taken as the average thickness of the unstretched film, and the standard deviation of all measured values ​​is taken as the standard deviation of the thickness of the unstretched film. The percentage obtained by dividing the standard deviation of thickness by the average thickness is taken as the thickness unevenness value (%) of the unstretched film, and the discharge stability is evaluated as follows.

[0270] A: The thickness variation value (%) of the unstretched film is 10 or less. B: The thickness variation value (%) of the unstretched film is greater than 10 and 15 or less. C: The thickness variation value (%) of the unstretched film is greater than 15 and 20 or less. D: The thickness variation value (%) of the unstretched film is greater than 20.

[0271] For evaluating discharge stability, A to C are preferable, with A being the best among them.

[0272] M. A film-forming resin film is wound up to 1000m at a winding speed of 20m / min or more. The film-forming properties are evaluated as follows based on the number of times the film breaks during the film roll collection.

[0273] A: Film breakage count is 2 or less. B: Film breakage count is 3 to 4 times. C: Film breakage count is 5 to 6 times. D: Film breakage count is 7 or more times.

[0274] In terms of film-forming properties, grades A to C are preferred, with A being the best among them.

[0275] N. Evaluation of electrical properties and processability (i) Conductivity evaluation In accordance with "D. Penetration resistivity" above, the resin film having an M layer on both surfaces shall be evaluated as follows.

[0276] AA: The average value of the penetration resistance is 1.0 × 10⁻⁶ ０ Ωcm or more: 1.0 × 10 ４ Less than Ωcm. A: The average value of the penetration resistivity is 1.0 × 10⁻⁶. ４ Higher than Ωcm, 1.0 × 10 ５ Less than Ωcm. B: The average value of the penetration resistivity is 1.0 × 10⁻⁶. ５ Higher than Ωcm, 1.0 × 10 ６ Less than Ωcm. C ＋ The average value of the penetration resistance is 1.0 × 10⁻⁶ ６ Higher than Ωcm, 1.0 × 10 ７ Less than Ωcm. C － The average value of the penetration resistance is 1.0 × 10⁻⁶ ７ Higher than Ωcm, 1.0 × 10 ８ Less than Ωcm. D: The average value of the penetration resistivity is 1.0 × 10⁻⁶. ８ It is higher than Ωcm.

[0277] Conductivity evaluation ranges from AA to C. － Of these, AA is preferable and the best among them.

[0278] (ii) Conductivity evaluation after tensile testing Ten 10 pieces of resin film having an M layer on both surfaces are cut to 10 cm x 10 cm. The ends of the cut samples are sandwiched between two metal plates with rubber attached to each end to secure the samples. At this time, the distance between the metal plates that secure both ends, i.e., the exposed portion of the resin film, is set to 50 mm. Then, an Instron-type tensile testing machine (AMF / RTA-100, manufactured by Orientec Co., Ltd.) is used, and the metal plates to which the cut samples are secured are fixed to the machine's chuck, and a tensile test is performed to deform the resin film by 2%. Specifically, the initial sample length is set to 50 mm, and the tensile test is performed at a tensile speed of 300 mm / min until the sample length is stretched by 1 mm. After that, the penetration resistivity of the stretched portion is measured in the same manner as in "D. Penetration Resistivity" above. Using the obtained resistivity R1 (Ωcm) and the resistivity R0 (Ωcm) obtained in item (i) above, the following evaluation is performed using the rate of increase of resistivity obtained by the following equation 9.

[0279] Increase rate of penetration resistance (%) = 100 × (R1 - R0) / R0 ... Equation 9

[0280] AA: The rate of increase in penetration resistance is 20% or less. A: The rate of increase in penetration resistance is greater than 20% but 30% or less. B: The rate of increase in penetration resistance is greater than 30% but 50% or less. C: The rate of increase in penetration resistance is greater than 50% but 100% or less. D: The rate of increase in penetration resistance is greater than 100%.

[0281] For conductivity evaluation after tensile stress, AA to C is preferred, with AA being the best among them.

[0282] (iii) Conductivity evaluation after bending Ten 10 pieces of resin film having an M layer on both surfaces are cut to 10 cm x 10 cm. The 10 cm x 10 cm samples are attached to a SUS cylinder with a diameter of 3 cm and a length of 15 cm, with a load of 300 g applied from both ends. The samples attached to the cylinder are placed in an oven heated to 50°C and subjected to heat treatment for 1 hour.

[0283] After heat treatment, the sample is removed from the cylinder, and the resistivity of the central portion of the sample is measured in the same manner as in "D. Resistivity" above. Using the obtained resistivity R2 (Ωcm) and the resistivity R0 (Ωcm) obtained in item (i) above, the following evaluation is performed using the rate of increase in resistivity obtained by the following equation 10.

[0284] Increase rate of penetration resistance (%) = 100 × (R2 - R0) / R0 ... Equation 10

[0285] AA: The rate of increase in penetration resistance is 20% or less. A: The rate of increase in penetration resistance is greater than 20% but 30% or less. B: The rate of increase in penetration resistance is greater than 30% but 50% or less. C: The rate of increase in penetration resistance is greater than 50% but 100% or less. D: The rate of increase in penetration resistance is greater than 100%.

[0286] For evaluating conductivity after bending, AA to C are preferred, with AA being the best among them.

[0287] O. Evaluation of bipolar batteries (i) Fabrication of resin current collectors for bipolar batteries A resin current collector for bipolar batteries is fabricated by creating a film on which a copper layer is attached to one side and an aluminum layer to the opposite side by vacuum deposition on both sides of a resin film.

[0288] Specifically, the roll of resin film used in this invention is placed in a roll-type vacuum deposition apparatus (ULVAC EWC-060), and an aluminum ingot is heated using an induction heating deposition method employing a carbon crucible to create an aluminum metal layer by vacuum deposition. At this time, the transport speed and output conditions are adjusted so that the aluminum metal layer reaches a predetermined thickness, and vacuum deposition is performed. Next, the roll of resin film with the aluminum metal layer on one side is again placed in the roll-type vacuum deposition apparatus (ULVAC EWC-060), and a copper metal layer is created on the resin film surface opposite to the side with the aluminum metal layer by heating a copper ingot using an induction heating deposition method employing a carbon crucible, and vacuum deposition is performed. At this time, the transport speed and output conditions are adjusted so that the copper metal layer reaches a predetermined thickness, and vacuum deposition is performed.

[0289] (ii) Active material for positive electrode, active material for negative electrode LiMn２ O ４ A cathode active material slurry is prepared by mixing 85% by mass of [unclear], 5% by mass of acetylene black as a conductive additive, 10% by mass of polyvinylidene fluoride (PVDF) as a binder, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent.

[0290] Furthermore, as a positive electrode to be placed at the end of a bipolar battery, the positive electrode active material slurry is applied to a 30 μm thick aluminum foil and cured by thermal polymerization to produce a terminal positive electrode in which the positive electrode is formed on the aluminum.

[0291] A slurry of the negative electrode active material is prepared by mixing 90 parts by mass of hard carbon as the negative electrode active material, 5 parts by mass of acetylene black as a conductive additive, 10 parts by mass of PVDF as a binder, and an appropriate amount of NMP as a slurry viscosity adjusting solvent.

[0292] Furthermore, as a negative electrode to be placed at the end of a bipolar battery, a negative electrode slurry is applied to a 30 μm copper foil and cured by thermal polymerization to produce a terminal negative electrode in which the negative electrode is formed on the copper foil.

[0293] (iii) Preparation of battery evaluation cell <Positive electrode - resin current collector assembly> After applying the positive electrode active material slurry onto the aluminum layer surface of the resin film having the metal layer using a doctor blade, press is applied to the coating of positive electrode active material slurry to make the current collector film thickness 30 μm.

[0294] <Fabrication of the electrolytic layer> PEO (polyethylene oxide) (64.5% by mass) is used as the ion-conducting polymer, and Li(C) is used as the supporting salt. ２ F ５ SO ２ ) ２ Prepare N (35.5% by mass) and use acetonitrile as a viscosity-adjusting solvent to prepare an electrolyte slurry.

[0295] An electrolyte slurry is poured between glass plates with a 50 μm gap in between, and then dried to create a 40 μm electrolyte layer.

[0296] <Fabrication of a cell for evaluation of a bipolar battery> The fabricated terminal positive electrode, negative electrode, terminal negative electrode, electrolyte layer, and positive electrode-current collector junction are cut to 120 mm x 70 mm. The terminal positive electrode and negative electrode, positive electrode-current collector junction, and electrolyte layer are stacked twice in sequence, and finally the terminal negative electrode is attached to fabricate a three-layer bipolar battery.

[0297] Al tabs and Ni tabs are welded to the positive and negative terminal ends, respectively, and the resulting battery is sealed under high pressure within an aluminum laminate to complete the evaluation cell for the bipolar battery.

[0298] (iv) Measurement of current value during charging and discharging The bipolar battery evaluation cell is set to 10 mV (Li ＋ Charge and discharge operations are performed up to / Li, and the current value generated during these operations is measured.

[0299] (v) Samples are taken from 10 different locations on a resin film having current-stabilizing metal layers on both sides, and 10 bipolar battery evaluation cells are prepared according to items (i) to (iii) above.

[0300] Next, charge and discharge operations are performed according to item (iv) above, and the current values ​​flowing through each of the 10 bipolar battery evaluation cells are recorded. The current value stability is evaluated as follows based on the average value obtained and the fluctuation of the current value relative to the average value through the charge and discharge operations.

[0301] A: The current value is halved from the average value once or less. B: The current value is halved from the average value two to three times. C: The current value is halved from the average value four to five times. D: The current value is halved from the average value six or more times, or the current value is zero once or more times.

[0302] In terms of current value stability, A through C show good results, with A being the best among them.

[0303] (vi) Battery characteristic variation Regarding the current values ​​during charging and discharging performed in (v) above, the average value of the 10 obtained current values ​​and the difference between the maximum and minimum values ​​of the 10 current values ​​are used to determine the variation using the following equation 11, which is defined as the battery characteristic variation and evaluated as follows.

[0304] (Battery characteristic variation) = 100 × (maximum value - minimum value) / (average value) ... Equation 11

[0305] A: Battery characteristic variation is 10% or less. B: Battery characteristic variation is greater than 10% but 20% or less. C: Battery characteristic variation is greater than 20% but 30% or less. D: Battery characteristic variation is greater than 30%.

[0306] In terms of battery characteristic variation, A through C show good results, with A being the best among them.

[0307] (vii) Samples are taken from 10 different locations on a resin film having a high-temperature stable metal layer on both sides, and 10 bipolar battery evaluation cells are prepared according to items (i) to (iii) above.

[0308] Next, charge and discharge operations are performed according to item (iv) above, and the current values ​​flowing through each of the 10 bipolar battery evaluation cells are recorded. Then, the 10 bipolar battery evaluation cells are heated in a constant temperature bath with air circulation from 25°C to 70°C at a heating rate of 5°C / min. After continuing heating for 30 minutes, charge and discharge operations are performed according to item (iv) above, and the current values ​​flowing through each of the 10 bipolar battery evaluation cells are recorded.

[0309] The following evaluation is performed based on the percentage decrease in current value before and after the heating treatment.

[0310] A: The decrease in current value after heat treatment is 20% or less. B: The decrease in current value after heat treatment is greater than 20% and 40% or less. C: The decrease in current value after heat treatment is greater than 40% and 50% or less. D: The decrease in current value after heat treatment is greater than 50%.

[0311] In terms of high-temperature battery stability, A through C show good performance, with A being the best among them.

[0312] (viiii) Samples are taken from 10 different locations on a resin film having a metal layer with battery heat deformation resistance on both sides, and 10 bipolar battery evaluation cells are prepared according to items (i) to (iii) above.

[0313] Next, in accordance with the heating test described in JIS 8715-2 (2019), ten fully charged bipolar battery evaluation cells are heated from 25°C to 85°C at a heating rate of 5°C / min in a constant temperature bath with air circulation. After holding the bipolar battery evaluation cells at 85°C for 3 hours, they are removed from the constant temperature bath, and the ten bipolar battery evaluation cells are evaluated according to the following conditions.

[0314] A: One or fewer cells out of 10 ignited or exploded. B: Two to three cells out of 10 ignited or exploded. C: Four to five cells out of 10 ignited or exploded. D: Six or more cells out of 10 ignited or exploded.

[0315] In terms of battery heat deformation resistance, grades A through C are good, with A being the best among them.

[0316] (ix) Samples are taken from 10 different locations on a film having a metal layer with battery shock resistance on both sides, and 10 bipolar battery evaluation cells are prepared according to items (i) to (iii) above.

[0317] Next, in accordance with the impact test described in JIS 8715-2 (2019), ten bipolar battery evaluation cells are discharged to 50% of their rated capacity and placed on a flat concrete floor. A SUS316 round bar with a diameter of 15.8 mm and longer than the maximum dimensions of the bipolar battery evaluation cells is placed so as to straddle the center of the bipolar battery evaluation cells, and a weight of 9.1 kg is dropped onto the round bar from a height of 610 mm. The evaluation is then performed on the ten bipolar battery evaluation cells in the following state.

[0318] A: One or fewer cells out of 10 ignited or exploded. B: Two to three cells out of 10 ignited or exploded. C: Four to five cells out of 10 ignited or exploded. D: Six or more cells out of 10 ignited or exploded.

[0319] In terms of battery shock resistance, A through C indicate good performance, with A being the best among them.

[0320] The present invention will be described below with reference to examples, but the present invention is not necessarily limited to these examples. The resins and conductive particles used in the production of the films in the examples and comparative examples are described below.

[0321] (Thermoplastic resins) Thermoplastic resin 1: Sumitomo Chemical Co., Ltd.'s polypropylene "Sumitomo Noblen" (registered trademark) FS2011DG3. Thermoplastic resin 2: USI Co., Ltd.'s CBC (Cyclic Block Copolymers. Hydrogenated styrene-butadiene block copolymer) "Vivion" (registered trademark) 0645. Thermoplastic resin 3: Nippon Polyethylene Co., Ltd.'s polyethylene "Novatec HD" (registered trademark) HY540. Thermoplastic resin 4: Mitsui Chemicals, Inc.'s modified polyolefin "Admer" (registered trademark) QF500.

[0322] Thermoplastic resin 5 and thermoplastic resin 6 were produced as resin pellets by the following manufacturing method.

[0323] [Production of Thermoplastic Resin 5] 1.9 moles of ethylene glycol were added to 1 mole of 2,6-dimethylnaphthalate (2,6DMN), and 0.03 parts by mass of magnesium acetate tetrahydrate and 0.010 parts by mass of phosphoric acid were added to 100 parts by mass of 2,6-dimethylnaphthalate (2,6DMN), and a heated transesterification was performed. Subsequently, 0.025 parts by mass of antimony trioxide were added, and polycondensation was carried out under high pressure and heated to obtain pellets of thermoplastic resin 5, which is a polyethylene naphthalate resin that is substantially particle-free. Thermoplastic resin 5 is a polyester resin containing a dicarboxylic acid component with 12 carbon atoms and a diol component with 2 carbon atoms, and has a glass transition temperature of 110°C, a crystallization temperature of 160°C, a melting peak temperature of 265°C, an intrinsic viscosity of 0.85 dl / g, and a water content of 2100 ppm by mass.

[0324] [Production of Thermoplastic Resin 6] To 1 mole of a dicarboxylic acid component consisting of 0.97 moles of dimethyl terephthalate (DMT) and 0.03 moles of dimethyl isophthalate, 0.60 moles of cyclohexanedimethanol and 1.30 moles of ethylenediol were added. In addition, 0.05 parts by mass of magnesium acetate tetrahydrate and 0.015 parts by mass of phosphoric acid were added to 100 parts by mass of the dicarboxylic acid component, and a heated transesterification was carried out. Subsequently, 0.025 parts by mass of antimony trioxide was added, and polycondensation was carried out under high pressure and increased temperature to obtain a pellet of thermoplastic resin 6 that is substantially particle-free. Thermoplastic resin 6 is a copolymer polyethylene terephthalate resin having 33 mol% of cyclohexanedimethanol and 67 mol% of ethylenediol as diol components. The thermoplastic resin 6 obtained by adjusting the polymerization time had a glass transition temperature of 80°C, a crystallization temperature of 135°C, a melting peak temperature of 251°C, an intrinsic viscosity of 0.77 dl / g, and a water content of 3800 ppm by mass.

[0325] Thermoplastic resin 7: α-olefin copolymer "Tafmer" (registered trademark), manufactured by Mitsui Chemicals, Inc.

[0326] (Conductive particles) Ketjenblack: Ketjenblack (registered trademark) EC600JD, manufactured by Lion Specialty Chemicals Co., Ltd. Carbon nanotubes: Multiwall carbon nanotubes (diameter: 9-20 nm, fiber length: 1 μm or more).

[0327] (Method for manufacturing carbon material master pellets) [Manufacturing of carbon-1] The thermoplastic resin 1 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 260°C to obtain carbon-1, which is a master pellet containing 10% by mass of Ketjenblack.

[0328] [Production of Carbon-2] The thermoplastic resin 1 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 260°C to obtain Carbon-2, a master pellet containing 10% by mass of carbon nanotubes.

[0329] [Production of Carbon-3] The thermoplastic resin 2 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 270°C to obtain Carbon-3, a master pellet containing 10% by mass of Ketjenblack.

[0330] [Production of Carbon-4] The thermoplastic resin 2 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 270°C to obtain Carbon-4, a master pellet containing 10% by mass of carbon nanotubes.

[0331] [Production of Carbon-5] The thermoplastic resin 3 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 260°C to obtain Carbon-5, which is a master pellet containing 10% by mass of Ketjenblack.

[0332] [Production of Carbon-6] The thermoplastic resin 3 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 260°C to obtain carbon-6, which is a master pellet containing 10% by mass of carbon nanotubes.

[0333] [Production of Carbon-7] The thermoplastic resin 4 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 260°C to obtain Carbon-7, which is a master pellet containing 10% by mass of Ketjenblack.

[0334] [Production of Carbon-8] The thermoplastic resin 4 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 260°C to obtain Carbon-8, a master pellet containing 10% by mass of carbon nanotubes.

[0335] [Production of Carbon-9] The thermoplastic resin 5 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 230 to 280°C to obtain Carbon-9, which is a master pellet containing 10% by mass of Ketjenblack.

[0336] [Production of Carbon-10] The thermoplastic resin 5 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 230 to 280°C to obtain carbon-10, which is a master pellet containing 10% by mass of carbon nanotubes.

[0337] [Production of Carbon-11] The thermoplastic resin 6 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 230 to 290°C to obtain Carbon-11, a master pellet containing 10% by mass of Ketjenblack.

[0338] [Production of Carbon-12] The thermoplastic resin 6 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 230 to 290°C to obtain carbon-12, which is a master pellet containing 10% by mass of carbon nanotubes.

[0339] [Production of Carbon-13] The thermoplastic resin 1 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 260°C to obtain Carbon-13, which is a master pellet containing 30% by mass of Ketjenblack.

[0340] [Production of Carbon-14] The thermoplastic resin 1 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 260°C to obtain carbon-14, a master pellet containing 30% by mass of carbon nanotubes.

[0341] [Production of Carbon-15] The thermoplastic resin 2 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 270°C to obtain Carbon-15, which is a master pellet containing 30% by mass of Ketjenblack.

[0342] [Production of Carbon-16] The thermoplastic resin 2 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 200 to 270°C to obtain carbon-16, a master pellet containing 30% by mass of carbon nanotubes.

[0343] [Production of Carbon-17] The thermoplastic resin 7 and Ketjenblack were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 170 to 250°C to obtain Carbon-17, which is a master pellet containing 10% by mass of Ketjenblack.

[0344] [Production of Carbon-18] The thermoplastic resin 7 and carbon nanotubes were kneaded and extruded using a twin-screw kneader set to gradually increase the temperature from 170 to 250°C to obtain carbon-18, which is a master pellet containing 10% by mass of carbon nanotubes.

[0345] The microstructure evaluation of the low-resistance region in the film cross-section according to an embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows the results of binarization analysis of an SSRM image obtained by performing scanning spreading resistance microscopy (SSRM) measurement on the film cross-section according to the method described in "C. Distribution Evaluation of Low-Resistance Region," with a resistivity of 1 × 10⁻⁶. ８ This figure shows an example of extracting the low-resistance region, where the resistance is less than Ω.

[0346] As shown in Figure 1, the binarization process based on the SSRM image clearly visualizes the spatial distribution of low-resistance regions within the film cross-section. In this embodiment, a predetermined threshold of 1 × 10⁻¹⁰ is used. ８ By using Ω, the region contributing to conductivity is extracted as a low-resistance region.

[0347] Figure 2 shows the Voronoi regions obtained by performing Voronoi tessellation based on the low-resistance regions extracted in Figure 1, using the centroid position of each low-resistance region as the generation point, according to the method described in "C. Distribution Evaluation of Low-Resistance Regions". The Voronoi regions shown in Figure 2 are used to quantitatively evaluate the distribution state of low-resistance regions and their spatial uniformity within the film cross-section, and the degree of dispersion and uneven distribution of low-resistance regions can be understood based on the area and shape of each Voronoi region.

[0348] (Examples 1-8, 11-14, Comparative Examples 1-3) Using thermoplastic resin 1, thermoplastic resin 2, thermoplastic resin 3, thermoplastic resin 4, thermoplastic resin 7, and master pellets Carbon-1 to Carbon-8 and Carbon-13 to Carbon-18 containing Ketjenblack (aspect ratio 1.2) or carbon nanotubes (aspect ratio 250), each pellet was mixed so that the final content ratio was as shown in Tables 1-1 and 1-2, and supplied to extruders for P1 and P2. In the case of a single-layer configuration, the same raw materials were supplied to each extruder. Melt extrusion was performed on each resin mixture, and after removing foreign matter with a 20 μm cut sintered filter, the layers were laminated using a feed block type A / B / A composite T die so that the surface layer (I) / base layer (II) / surface layer (I) had a thickness ratio of 1 / 8 / 1. The obtained molten sheet was discharged into a casting drum with a surface temperature controlled to 20°C and pressed tightly against the casting drum with an air knife. Subsequently, compressed air at 15°C was injected at an air velocity of 140 m / s onto the uncooled drum surface of the sheet on the casting drum using an air knife to cool the sheet and obtain an unstretched sheet. Next, the unstretched sheet was brought into contact with a metal roll at 95°C in the first half of the preheating process, and then heated to 120°C in the second half of the preheating process. It was then stretched longitudinally at the magnification ratio shown in the table between rolls at 147°C with a difference in peripheral speed. Next, a 5.5% relaxation treatment was performed longitudinally on a metal roll heated to 95°C to obtain a uniaxially oriented film. Next, the obtained uniaxially oriented film was introduced into a tenter-type stretcher with both ends in the width direction gripped with clips, preheated at 137°C for 2 seconds, stretched in the width direction at the magnification ratio shown in the table at 152°C, and then heat-treated at 155°C while providing a 10% relaxation in the width direction. Subsequently, after a cooling process at 100°C, the film was guided to the outside of the tenter, the clips at both ends in the film width direction were released, and plasma treatment was performed on both surfaces of the film by atmospheric pressure glow discharge. After that, the film was wound onto a core to obtain biaxially oriented films with a thickness of 5 μm or 90 μm. The physical properties and evaluation results of the obtained films are shown in the table.

[0349] A film with a metal layer was obtained by applying metal layers M and M' to both sides of the obtained film using vacuum deposition so that the thickness of the metal layer was as shown in the table. A resin current collector for a bipolar battery was fabricated by using the metal types as shown in the table. As described in the [Bibpolar Battery Evaluation] section above, the film with the metal layer was incorporated as a resin current collector into a cell for bipolar battery evaluation, and the bipolar battery was evaluated. The evaluation results are shown in the table.

[0350] (Examples 9 and 10) Using thermoplastic resin 1, thermoplastic resin 4, thermoplastic resin 5, thermoplastic resin 6, and master pellets containing Ketjenblack (aspect ratio 1.2) or carbon nanotubes (aspect ratio 250), namely carbon-1, carbon-2, carbon-7, carbon-8, and carbon-9 to carbon-12, each resin was mixed so that the final content ratio was as shown in the table, and supplied to extruders for P1 and P2. Thermoplastic resin 5, carbon-9, and carbon-10 were dried under reduced pressure at 180°C for 4 hours, and thermoplastic resin 6, carbon-11, and carbon-12 were dried under reduced pressure at 70°C for 12 hours before use. In the case of a single-layer structure, the same raw materials were supplied to each extruder. Melt extrusion was performed on each resin mixture, and after removing foreign matter with a 20 μm cut sintered filter, the layers were laminated in a feed block type A / B / A composite T die so that the surface layer (I) / base layer (II) / surface layer (I) had a thickness ratio of 1 / 8 / 1. The resulting molten sheet was discharged into a casting drum with a surface temperature controlled to 50°C, and an unstretched sheet was obtained by adhering it to the casting drum and cooling it using an electrostatic ignition casting method.

[0351] Next, the film was guided to a group of stretching rolls heated to 60°C to 120°C in the longitudinal direction and stretched to 3.0 times its original length. After that, the uniaxially stretched film was guided to a tenter and preheated to 90°C, then stretched to 3.0 times its original length in the width direction at a temperature of 100°C to 130°C. Heat treatment was then performed at 210°C below a constant length, and a 4% relaxation treatment was applied in the width direction to obtain a biaxially oriented film with a thickness of 5 μm. The physical properties and evaluation results of the obtained film are shown in the table.

[0352] A film with a metal layer was obtained by applying metal layers M and M' to both sides of the obtained film using vacuum deposition so that the thickness of the metal layer was as shown in the table. A resin current collector for a bipolar battery was fabricated by using the metal types as shown in the table. As described in the [Bibpolar Battery Evaluation] section above, the film with the metal layer was incorporated as a resin current collector into a cell for bipolar battery evaluation, and the bipolar battery was evaluated. The evaluation results are shown in the table.

[0353]

[0354]

[0355]

[0356]

[0357]

[0358]

[0359]

[0360]

[0361]

Claims

1. A resin film that satisfies the following conditions 1 and 2 when the penetration resistivity is measured at 9 locations within a 90 mm x 90 mm square area. Condition 1: The average value of the penetration resistivity is 1.0 x 10 ０ Ωcm or more: 1.0 × 10 ８ Condition 2 for Ωcm or less: The coefficient of variation of the resistivity (standard deviation divided by the mean) is 5% or more and 70% or less. (However, the measurement position for resistivity is determined by dividing the 90mm x 90mm square area into nine 30mm x 30mm squares in a 3x3 grid, with the center of each square being the measurement position.) 2. In the SSRM (Scanning Spread Resistance Microscopy) image of the cross-section perpendicular to the principal orientation axis and in the thickness direction, 1.0 × 10 ８ The standard deviation of the area of ​​the Voronoi region formed by the low-resistance region below Ω is 2.0 × 10⁻⁶. ５ nm ２ The above 6.0 x 10 ６ nm ２ The resin film according to claim 1, which is as follows:

3. The resin film according to claim 1 or 2, comprising a resin component and at least resins A and B, which include carbon particles and / or metal particles, wherein the resin component is immiscible with respect to each other.

4. The resin film according to claim 3, wherein the total content of carbon particles and metal particles is 1.0% by mass or more and less than 20% by mass, based on 100% by mass of the total mass of the resin film.

5. The resin film according to claim 3, wherein resin A and resin B are selected from polyolefin resin and polyester resin.

6. The resin film according to claim 3, wherein when the weight ratio of resin A is Wa (mass%) and the weight ratio of resin B is Wb (mass%), Wa / Wb is 1.0 or more and 2.5 or less.

7. The resin film according to claim 3, wherein the difference in glass transition temperatures (Tg) of resin A and resin B is 20°C or more and 200°C or less.

8. The resin film according to claim 3, wherein the difference between the heat of fusion derived from resin A and the heat of fusion derived from resin B is 4 J / g or more and 45 J / g or less.

9. The resin film according to claim 3, wherein resin A is a polypropylene resin and resin B is a polyethylene resin and / or a cyclic olefin resin.

10. The resin film according to claim 3, wherein resin A is a polyester resin and resin B is a resin selected from one of polypropylene resin, polyethylene resin, and cyclic olefin resin.

11. The resin film according to claim 3, wherein the contained carbon particles and / or metal particles are carbon particles and / or metal particles (C1) having an aspect ratio of 1 or more and less than 5, and carbon particles and / or metal particles (C2) having an aspect ratio of 10 or more.

12. The resin film according to claim 11, wherein the ratio of carbon particles and / or metal particles (C1) having an aspect ratio of 1 or more and less than 5 to carbon particles and / or metal particles (C2) having an aspect ratio of 10 or more is 0.10 or more and 5.0 or less.

13. The resin film according to claim 1 or 2, wherein the F5 value (the value obtained by dividing the load value when the test piece is stretched by 5% by the cross-sectional area of ​​the test piece) in at least one direction within the plane is 25 MPa or more and 150 MPa or less.

14. The resin film according to claim 1 or 2, wherein the F5 value (the value obtained by dividing the load value when the test piece is stretched by 5% by the cross-sectional area of ​​the test piece) in both the longitudinal and width directions is 25 MPa or more and 150 MPa or less.

15. The resin film according to claim 1 or 2, wherein the elongation at break in at least one direction within the plane is 13% or more and 220% or less.

16. In the binarized analysis image of the SSRM (Scanning Spread Resistance Microscopy) image in the cross-sectional area perpendicular to the principal orientation and thickness direction, the low-resistance region (1.0 × 10) ８ The resin film according to claim 1 or 2, wherein the average value of the aspect ratio (less than or equal to Ω) is 1.5 or more and 2.5 or less.

17. In a cross-sectional image of the resin film obtained by a scanning electron microscope, the average area of the carbon particles and / or metal particles is 0.10 µm ２ or more and 10 µm ２ or less, the resin film according to claim 3.

18. In a cross-sectional image of a resin film taken with a scanning electron microscope, the area is 0.10 μm². ２ The resin film according to claim 3, wherein the proportion of the number of carbon particles and / or metal particles is 25% or more and 100% or less of the total number of particles.

19. The resin film according to claim 1 or 2, comprising at least two or more resin layers.

20. In the SSRM (Scanning Spread Resistance Microscopy) image of the cross-section perpendicular to the principal orientation axis and in the thickness direction, 1.0 × 10 ８ The standard deviation of the area of ​​the Voronoi region formed by the low-resistance region below Ω is 2.0 × 10⁻⁶. ５ nm ２ The above 6.0 x 10 ６ nm ２ The following is a resin film.

21. The resin film according to claim 1 or 2, wherein the thickness is 1 μm or more and 100 μm or less.

22. A current collector having a layer made of a metal and / or a metallic compound on at least one surface of the resin film according to claim 1 or 2.

23. The current collector according to claim 22, wherein the layer made of the metal and / or metallic compound contains an aluminum element.

24. The current collector according to claim 22, wherein a layer made of metal and / or a metallic compound on one surface of the resin film contains an aluminum element, and a layer made of metal and / or a metallic compound on the opposite surface contains a copper element.

25. Penetration resistivity is 1.0 × 10⁻⁶ ０ Ωcm or more: 1.0 × 10 ８ The current collector according to claim 22, wherein the current is less than or equal to Ωcm.

26. A resin current collector for a bipolar battery comprising the current collector described in claim 22.

27. An electrode for a bipolar battery, comprising a negative electrode active material layer on one surface of a resin current collector for a bipolar battery according to claim 26, and a positive electrode active material layer on the surface opposite to the said surface.

28. A secondary battery comprising the bipolar battery electrode described in claim 27.

29. A solid-state battery comprising at least two or more electrodes for a bipolar battery as described in claim 27, and a solid electrolyte layer between a plurality of hyperbolic battery electrodes.

30. An electric vehicle equipped with a secondary battery according to claim 28 or a solid battery according to claim 29.

31. An electric flying vehicle equipped with a secondary battery according to claim 28 or a solid battery according to claim 29.

32. An electronic device equipped with a secondary battery according to claim 28 or a solid battery according to claim 29.

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