Insulator film, lead wire, and non-aqueous electrolyte battery

Abstract

To provide an insulating film, a lead wire, and a non-aqueous electrolyte battery, capable of suppressing occurrence of a short circuit between a metal layer of an enclosure container and a conductor.SOLUTION: An insulating film according to the invention is an insulating film containing a first layer. The first layer contains a polyolefin, and a part of the polyolefin is a crosslinked polyolefin. In a DSC curve of the first layer, one or more melting peaks exist at 40°C or higher and 120°C or lower, and one or more melting peaks exist at 130°C or higher and 170°C or lower. The DSC curve can be obtained by measuring using a differential scanning calorimeter at a condition of a temperature rise rate of 10°C / min in a range of -50°C to 250°C. In a first image obtained by staining a cross section of the first layer in a thickness direction along TD with a ruthenium-based dye and then observing the cross section with a transmission electron microscope, a phase separation structure composed of a stained region and an unstained region is observed, and in the first image, an area percentage of the stained region is 10% or more and 70% or less. The insulating film has a heat deformation residue of 15% or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an insulating film, a lead wire, and a non-aqueous electrolyte battery.

Background Art

[0002] As a lead wire used for a battery, a lead wire composed of a lead conductor connected to a positive electrode or a negative electrode of the battery and an insulating resin layer covering the lead conductor has been proposed.

[0003] Patent Document 1 discloses a lead wire for a non-aqueous electrolyte battery (tab lead) having a lead conductor, a first insulating layer directly covering at least a part of the lead conductor, and a second insulating layer covering the first insulating layer, wherein the second insulating layer is formed from a crosslinked product of a resin composition containing an olefin crystal - ethylene butene - olefin crystal block polymer and polypropylene in a mass ratio of 10:90 to 40:60.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described in Patent Document 1, in a lead wire for a non-aqueous electrolyte battery, by using a crosslinked product for the second insulating layer, it is possible to prevent a short circuit between the metal layer of the encapsulation container and the lead conductor due to melting of the insulating layer during heat fusion bonding between the lead conductor and the insulating layer. Usually, a crosslinked product of polypropylene is used as the crosslinked product.

[0006] Since polypropylene is a material that is difficult to crosslink, in the lead wire for a non-aqueous electrolyte battery of Patent Document 1, the second insulating layer is crosslinked by irradiation with radiation. Irradiation with radiation requires special equipment, and a great deal of cost is incurred for the introduction of the equipment. For this reason, an insulating film that can be manufactured without using irradiation rays, can suppress the occurrence of a short circuit between the metal layer of the encapsulation container and the lead conductor, and has excellent adhesiveness to the conductor, as well as a lead wire and a non-aqueous electrolyte battery including the same, are desired.

[0007] Therefore, an object of the present disclosure is to provide an insulating film that can be manufactured without using irradiation rays, can suppress the occurrence of a short circuit between the metal layer of the encapsulation container and the conductor when used in a non-aqueous electrolyte battery, has excellent adhesiveness to the conductor, as well as a lead wire and a non-aqueous electrolyte battery including the same.

Means for Solving the Problems

[0008] The insulating film of the present disclosure is an insulating film including a first layer, the first layer includes a polyolefin, a part of the polyolefin is a crosslinked polyolefin, in the DSC curve of the first layer, there is one or more melting peaks at 40°C or higher and 120°C or lower, and there is one or more melting peaks at 130°C or higher and 170°C or lower, the DSC curve is obtained by measuring in the range of -50°C to 250°C at a heating rate of 10°C / min using a differential scanning calorimeter, after staining a cross section in the thickness direction along TD of the first layer with a ruthenium-based dye and observing the cross section with a transmission electron microscope, a phase separation structure composed of a stained region and a non-stained region is observed in the first image obtained, in the first image, the area percentage of the stained region is 10% or more and 70% or less, the insulating film has a heat deformation residual rate of 15% or more.

Advantages of the Invention

[0009] According to the present disclosure, there is provided an insulating film that can be manufactured without using irradiation rays, can suppress the occurrence of a short circuit between a metal layer of an encapsulating container and a conductor when used in a non-aqueous electrolyte battery, and has excellent adhesiveness to the conductor, as well as a lead wire and a non-aqueous electrolyte battery including the same.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) The insulating film of the present disclosure is an insulating film including a first layer, wherein the first layer contains a polyolefin, a part of the polyolefin is a crosslinked polyolefin, in the DSC curve of the first layer, there is one or more melting peaks at 40°C or higher and 120°C or lower, and there is one or more melting peaks at 130°C or higher and 170°C or lower, the DSC curve is obtained by measuring in the range of -50°C to 250°C at a heating rate of 10°C / min using a differential scanning calorimeter, In a first image obtained by observing a cross-section in the thickness direction along the TD of the first layer after staining the cross-section with a ruthenium-based dye, a phase separation structure composed of a stained region and a non-stained region is observed. In the first image, the area percentage of the stained region is 10% or more and 70% or less. The insulation film has a heat distortion residue rate of 15% or more.

[0012] According to the present disclosure, it is possible to provide an insulation film that can be manufactured without using irradiation rays, suppress the occurrence of a short circuit between the metal layer of the encapsulation container and the conductor when used in a non-aqueous electrolyte battery, and has excellent adhesiveness to the conductor, as well as a lead wire and a non-aqueous electrolyte battery including the same.

[0013] (2) In the above (1), the polyolefin may include at least one selected from the group consisting of ultra-low density polyethylene, low density polyethylene, and linear polyethylene. According to this, cross-linking can be stably performed.

[0014] (3) In the above (1) or (2), the ratio IA / IB of the peak intensity IA at a wave number of 1082 cm -1 in the infrared absorption spectrum measured by Fourier transform infrared spectroscopy by the transmission method of the first layer to the peak intensity IB after film thickness correction of the peak intensity IA is 0.20 or more. The silicon content measured by ICP emission spectrometry of the first layer may be 0.04% by mass or more and 1.0% by mass or less.

[0015] According to this, cross-linking can be performed without requiring special equipment.

[0016] (4) In any of the above (1) to (3), The first layer includes a first main surface. The insulation film further includes a second layer provided on the first main surface. The second layer may be composed of at least one selected from the first group consisting of acid-modified polypropylene and olefin elastomers, or may be composed of a composite of two or more selected from the first group.

[0017] The second layer has good adhesion to the conductor. Therefore, when the insulating film is used in a non-aqueous electrolyte battery, the insulating film and the conductor can have excellent adhesion.

[0018] (5) In the above (4), The first layer includes a second main surface opposite to the first main surface, The insulating film further includes a third layer provided on the second main surface, The third layer may be composed of at least one selected from the second group consisting of homopolypropylene, block polypropylene, random polypropylene, acid-modified polypropylene, and olefin elastomers, or may be composed of a composite of two or more selected from the second group.

[0019] The third layer has good adhesion to the encapsulation container. Therefore, when the insulating film is used in a non-aqueous electrolyte battery, the insulating film and the encapsulation container can have excellent adhesion.

[0020] (6) In any one of the above (1) to (5), the percentage (T1 / TA)×100 of the average thickness T1 of the first layer with respect to the average thickness TA of the insulating film may be 20% or more. According to this, the effect of suppressing the occurrence of a short circuit between the metal layer of the encapsulation container and the conductor is further improved.

[0021] (7) In any one of the above (1) to (6), the gel fraction of the insulating film may be 5% or more and 40% or less. According to this, the effect of suppressing the occurrence of a short circuit between the metal layer of the encapsulation container and the conductor is further improved.

[0022] (8) The lead wire of the present disclosure a conductor, A lead wire having any one of the insulating films (1) to (7) covering at least a part of the outer peripheral surface of the conductor.

[0023] When the lead wire of the present disclosure is used in a non-aqueous electrolyte battery, it is possible to suppress the occurrence of a short circuit between the metal layer of the encapsulation container and the conductor.

[0024] (9) The non-aqueous electrolyte battery of the present disclosure A battery cell including a positive electrode, a negative electrode, and an electrolyte sandwiched between the positive electrode and the negative electrode, Conductors electrically connected to each of the positive electrode and the negative electrode, An encapsulation container for sealing the battery cell, A part of the conductor is exposed outside the encapsulation container, Any one of the insulating films (1) to (7) is disposed between the conductor and the encapsulation container, A non-aqueous electrolyte battery in which the encapsulation container and the insulating film are fused.

[0025] The non-aqueous electrolyte battery of the present disclosure can suppress the occurrence of a short circuit between the metal layer of the encapsulation container and the conductor.

[0026] [Details of Embodiments of the Present Disclosure] Specific examples of the insulating film, lead wire, and non-aqueous electrolyte battery of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same parts or corresponding parts. Also, dimensional relationships such as length, width, thickness, depth, etc. have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0027] In this specification, the notation in the form of "A to B" means A or more and B or less. When there is no unit description for A and a unit is described only for B, the units of A and B are the same.

[0028] In the present disclosure, when one or more numerical values are described as the lower limit and the upper limit of a numerical range, any combination of any one numerical value described as the lower limit and any one numerical value described as the upper limit shall also be disclosed.

[0029] [Embodiment 1: Insulating Film] An insulating film according to an embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") is an insulating film including a first layer, wherein the first layer contains a polyolefin, a part of the polyolefin is a crosslinked polyolefin, in the DSC curve of the first layer, there is one or more melting peaks at 40°C or higher and 120°C or lower, and there is one or more melting peaks at 130°C or higher and 170°C or lower, the DSC curve is obtained by measuring in the range of -50°C to 250°C at a heating rate of 10°C / min using a differential scanning calorimeter, after staining a cross-section in the thickness direction along TD of the first layer with a ruthenium-based dye and observing the cross-section with a transmission electron microscope, a phase separation structure composed of a stained region and a non-stained region is observed in the first image, in the first image, the area percentage of the stained region is 10% or more and 70% or less, and the insulating film has a heat distortion residual rate of 15% or more.

[0030] ≪Structure of Insulating Film≫ As shown in FIGS. 1 and 2, the insulating film 5 includes a first layer 7. The first layer 7 can include a first main surface 7a and a second main surface 7b opposite to the first main surface 7a. As shown in FIG. 1, the insulating film 5 can include the first layer 7 and a second layer 6 provided on the first main surface 7a of the first layer 7. As shown in FIG. 2, the insulating film 5 can include the first layer 7, a second layer 6 provided on the first main surface 7a of the first layer 7, and a third layer 8 provided on the second main surface 7b of the first layer 7.

[0031] The average thickness of the insulating film 5 can be appropriately set according to the application. The average thickness of the insulating film 5 may be, for example, 20 μm or more and 1000 μm or less, or may be 30 μm or more and 800 μm or less.

[0032] In the present disclosure, the average thickness of the insulating film 5 is measured by the following procedure. Among the outer peripheral surfaces of the insulating film 5, the insulating film 5 is cut with a microtome or the like along the normal direction of the surface having the largest area, and the cross section is exposed. The cross section is observed at 250 times magnification using a digital microscope, and the thickness of the insulating film 5 is measured at five positions. The average of the thicknesses at the five positions is calculated. This average corresponds to the average thickness of the insulating film 5. In the present disclosure, the average thicknesses of the first layer 7, the second layer 6, and the third layer 8 described later are also measured by the same method.

[0033] ≪Heating deformation residual ratio of insulating film≫ The heating deformation residual ratio of the insulating film 5 of Embodiment 1 is 15% or more. According to this, the insulating film 5 is difficult to melt during heat fusion with the lead conductor, and it is possible to prevent a short circuit between the metal layer of the encapsulation container and the lead conductor due to melting of the insulating film. The heating deformation residual ratio of the insulating film 5 may be 25% or more, or may be 35% or more. The upper limit of the heating deformation residual ratio of the insulating film 5 is not particularly limited, but can be, for example, 80% or less.

[0034] In the present disclosure, the heating deformation residual ratio of the insulating film 5 is measured by the following procedure. A sample made of the insulating film is placed in a TMA (Thermal Mechanical Analysis) apparatus, and the temperature is raised while applying a load of 0.1 MPa to the probe, and the thickness Tr at room temperature and the thickness Th at 200 °C are measured. The percentage (Th / Tr)×100 of the thickness Th at 200 °C with respect to the thickness Tr at room temperature is defined as the heating deformation residual ratio (%) of the insulating film 5.

[0035] ≪Gel fraction of insulating film≫ The gel fraction of the insulating film 5 of Embodiment 1 may be 5% or more and 40% or less. From the viewpoint of suppressing the melting of the insulating film during heat fusion with the lead conductor, the lower limit of the gel fraction of the insulating film 5 may be 20% or more, or may be 30% or more. From the viewpoint of suppressing over-crosslinking, the upper limit of the gel fraction of the insulating film 5 may be 80% or less, or may be 70% or less. The gel fraction of the insulating film 5 may be 20% or more and 80% or less, or may be 30% or more and 70% or less.

[0036] In the present disclosure, the gel fraction of the insulating film 5 is measured by the following procedure. Approximately 1.0 g of the insulating film (this weight is designated as W1) is immersed in xylene at 120°C for 24 hours, then the liquid portion is discarded, and the solid portion is heated at 120°C for 3 hours to dry and remove the xylene component. Thereafter, the weight of the solid portion (designated as W2) is measured, and (W2 / W1) × 100 (%) is taken as the gel fraction.

[0037] <First layer> In the insulating film 5 of Embodiment 1, the first layer 7 functions as a support for the insulating film 5. The first layer 7 is difficult to melt at the temperature when heat-sealing the opening of the encapsulation container, and can suppress a short circuit between the metal layer of the encapsulation container and the conductor 3.

[0038] ≪Composition of the first layer≫ The first layer 7 contains a polyolefin. Examples of the polyolefin include homopolypropylene, block polypropylene, acid-modified polypropylene, ultra-low density polyethylene, low density polyethylene, and linear polyethylene. Examples of the acid-modified polypropylene include maleic acid-modified polypropylene, acrylic acid-modified polypropylene, and maleic anhydride-modified polypropylene. Ultra-low density polyethylene is polyethylene having a specific gravity of 0.91 or less. Low density polyethylene is polyethylene having a specific gravity greater than 0.91 and less than or equal to 0.94. Linear polyethylene has a specific gravity equivalent to that of low density polyethylene and has a higher peel strength between the conductor and the insulating film than low density polyethylene.

[0039] The first layer can include at least one selected from the group consisting of homopolypropylene, block polypropylene, and acid-modified polypropylene, and at least one selected from the group consisting of ultra-low density polyethylene, low density polyethylene, and linear polyethylene.

[0040] That the first layer 7 contains a polyolefin can be confirmed by performing imaging IR analysis using a Fourier transform infrared spectrophotometer only on the first layer 7 of the insulating film 5. When the first layer 7 contains a polyolefin, the polyolefin is detected in the imaging IR analysis. The first layer 7 may be taken out from the insulating film 5 and the above-described transmission light analysis may be performed.

[0041] In the first layer 7, a part of the polyolefin is a crosslinked polyolefin. That a part of the polyolefin is crosslinked can be confirmed from the heat deformation residual rate of the first layer 7. Specifically, when the heat deformation residual rate of the first layer 7 is 15% or more, it is determined that a part of the polyolefin is crosslinked. In the present disclosure, the heat deformation residual rate of the first layer is measured by the following procedure. Prepare a sample consisting of the entire insulating film including the first layer. Put the sample into a TMA apparatus. Heat the sample while applying a load of 0.1 MPa to the probe, hold it at 200 °C for 1 minute, and take out the sample after cooling to room temperature. Cut each of the samples before and after heating and pressurization by the TMA in the same manner as the method for measuring the average thickness of the above-described insulating film to expose the cross section. In the cross section, measure the thickness of only the first layer. The percentage (Th / Tr)×100 of the thickness Th of the first layer after heating and pressurization to the thickness Tr of the first layer before heating and pressurization is defined as the heat deformation residual rate (%) of the first layer 7.

[0042] The first layer 7 may contain a thermoplastic resin other than the above-described polyolefin and may contain other known additives, as long as the effects of the present disclosure are not impaired. Examples of the known additives include an antioxidant, a flame retardant, an adhesion promoter, a lubricant, a filler, a crystal nucleating agent, a colorant, and the like.

[0043] ≪DSC curve of the first layer≫ In the DSC curve of the first layer 7, there is at least one melting peak at 40°C or higher and 120°C or lower, and at least one melting peak at 130°C or higher and 170°C or lower. This indicates that the first layer 7 contains two or more types of polyolefins.

[0044] In the present disclosure, the DSC curve of the first layer 7 is created using a differential scanning calorimeter in accordance with JIS K 7121-1987 "Method for Measuring the Transition Temperature of Plastics". Specifically, the DSC curve of the first layer 7 is obtained by taking the first layer 7 out of the insulating film 5 and measuring it in a differential scanning calorimeter under the conditions of a temperature increase rate of 10°C / min from -50°C to 250°C.

[0045] In the DSC curve of the first layer 7, the temperature of the melting peak existing at 40°C or higher and 120°C or lower (hereinafter also referred to as the "first melting peak") may be 45°C or higher and 115°C or lower, or 48°C or higher and 110°C or lower. When there are two or more melting peaks existing at 40°C or higher and 120°C or lower, the first melting peak is the melting peak with the largest peak height. The melting peak existing at 40°C or higher and 120°C or lower is presumed to be a peak derived from ultra-low density polyethylene, low density polyethylene, or linear polyethylene.

[0046] In the DSC curve of the first layer 7, the temperature of the melting peak existing at 130°C or higher and 170°C or lower (hereinafter also referred to as the "second melting peak") may be 135°C or higher and 165°C or lower. When there are two or more melting peaks existing at 130°C or higher and 170°C or lower, the second melting peak is the melting peak with the largest peak height. The melting peak existing at 130°C or higher and 170°C or lower is presumed to be a peak derived from a polypropylene-based material.

[0047] ≪Structure of the First Layer≫ In the first image obtained by observing the cross-section in the thickness direction along the TD of the first layer 7 after staining the cross-section with a ruthenium-based dye, a phase separation structure consisting of a stained region and an unstained region is observed. In the first image, the area percentage of the stained region is 20% or more and 80% or less. The stained region is presumed to be a region corresponding to the amorphous part of the non-crystalline part. The unstained region is presumed to be a region corresponding to the crystalline part of the crystalline part. Examples of the ruthenium-based dye include ruthenium tetroxide. TD (Transverse Direction) means a direction perpendicular to the direction (MD: Machine Direction) in which the insulating film is conveyed in the manufacturing process of the insulating film.

[0048] In the first image, from the viewpoint that the impact resistance of the polymer material improves as the amorphous part increases, the lower limit of the area percentage of the stained region may be 25% or more, or 30% or more. In the first image, since the peel strength is likely to decrease when the amorphous part is large, from the viewpoint of suppressing the decrease in the peel strength, the upper limit of the area percentage of the stained region may be 80% or less, or 75% or less. In the first image, the area percentage of the stained region may be 25% or more and 80% or less, or 30% or more and 75% or less.

[0049] In the present disclosure, the measurement of the area percentage of the stained region is measured by performing image processing on the first image. For the image processing, image analysis software ImageJ is used. Specifically, the first image is acquired as a digital file of a grayscale image (JPEG), and the processing is performed according to the following binarization processing procedure and parameters. Pixels with a tone (bright) above the threshold are output as 1, and pixels with a tone (dark) below the threshold are output as 0, and each is defined as a stained region and an unstained region. The bright pixels are the unstained region and correspond to the crystalline part. The dark pixels are the stained region and correspond to the non-crystalline part.

[0050] <Binarization processing> 1. Spike noise removal (Despeckle) 2. Removal of Island Outliers (radius = 4, threshold = 1, which = Bright) 3. Removal of Sea Outliers (radius = 4, threshold = 1, which = Dark) 4. Despeckle 5. Gaussian Blur in the X-axis (sample short side) direction (threshold = 3 pixels) 6. Contrast Enhancement (saturated = 0.2) 7. Removal of Island Outliers (radius = 4, threshold = 1, which = Bright) 8. Removal of Sea Outliers (radius = 4, threshold = 1, which = Dark) 9. Otsu Binarization

[0051] Using the image analysis software ImageJ, the area percentage of the stained region with respect to the total area of the first image is calculated. The above measurement is performed on three non-overlapping first images. The average of the area percentages of the stained regions of the three first images is calculated. In the present disclosure, the average corresponds to the area percentage of the stained region in the first image.

[0052] ≪Infrared Absorption Spectrum Measured by Fourier Transform Infrared Spectroscopy of the First Layer≫ The ratio IA / IB of the peak intensity IA at a wavenumber of 1082 cm -1 in the infrared absorption spectrum measured by Fourier transform infrared spectroscopy in the transmission method of the first layer 7 and the peak intensity IB after film thickness correction of the peak intensity IA may be 0.05 or more, 0.10 or more, or 0.20 or more. At a wavenumber of 1082 cm -1The peak intensity IA is derived from the siloxane bond. The upper limit of the ratio IA / IB can be set to 1 or less. The ratio IA / IB may be 0.05 or more and 1 or less, may be 0.10 or more and 1 or less, or may be 0.20 or more and 1 or less. The measurement of the infrared absorption spectrum is performed at room temperature (23°C ± 5°C). The peak intensity IB after film thickness correction is obtained by dividing the peak intensity IA measured for the entire insulating film by the first layer film thickness (unit: μm). That is, the peak intensity IB after film thickness correction = peak intensity IA / film thickness.

[0053] ≪Silicon content of the first layer≫ The silicon content measured by ICP emission spectrometry for the first layer 7 may be 0.05 mass% or more and 1.0 mass% or less. The lower limit of the silicon content of the first layer 7 may be 0.05 mass% or more, or 0.1 mass% or more, from the viewpoint of suppressing melting of the insulating film during thermal fusion with the lead conductor. The upper limit of the silicon content of the first layer 7 may be 1 mass% or less, or 0.8 mass% or less, from the viewpoint of maintaining the peel strength. The silicon content of the first layer 7 may be 0.1 mass% or more and 1.0 mass% or less, or 0.1 mass% or more and 0.8 mass% or less.

[0054] The specific method of ICP emission spectrometry is as follows. Approximately 0.1 g of the entire insulating film is collected, added to approximately 8 mL of nitric acid, subjected to microwave treatment to completely dissolve it, and the recovered solution is made up to 50 mL. The silicon concentration of the 50 mL solution is measured. Assuming that the specific gravity of each layer is constant, the dissolved weight of the first layer is calculated from the thickness ratio of the first layer. Considering that silicon is contained only in the first layer, the silicon concentration of the first layer is calculated.

[0055] ≪Thickness of the first layer≫ In the insulating film 5 of Embodiment 1, from the viewpoint of suppressing the occurrence of a short circuit between the metal layer of the encapsulation container and the lead conductor, the lower limit of the percentage (T1 / TA)×100 of the average thickness T1 of the first layer with respect to the average thickness TA of the insulating film 5 may be 10% or more, may be 15% or more, or may be 20% or more. The upper limit of the percentage (T1 / TA)×100 may be 80% or less, or may be 75% or less from the viewpoint of maintaining the peel strength. The percentage (T1 / TA)×100 may be 10% or more and 80% or less, may be 15% or more and 80% or less, or may be 20% or more and 75% or less.

[0056] The average thickness T1 of the first layer may be, for example, 10 μm or more and 300 μm or less, or may be 20 μm or more and 250 μm or less.

[0057] <Second layer> In addition to the first layer 7, the insulating film 5 of Embodiment 1 may further include a second layer 6 provided on the first main surface 7a of the first layer 7. The second layer 6 functions as an adhesive layer with the conductor of the lead wire.

[0058] ≪Composition of the second layer≫ The second layer 6 can be composed of at least one selected from the first group consisting of acid-modified polypropylene and olefin-based elastomers, or a composite of two or more selected from the first group. Examples of the acid-modified polypropylene include maleic acid-modified polypropylene, acrylic acid-modified polypropylene, maleic anhydride-modified polypropylene, and the like. The composite of two or more selected from the first group indicates a state in which two or more materials are present in the second layer 6.

[0059] That the second layer 6 is composed of at least one selected from the above first group or a composite of two or more selected from the above first group can be confirmed by performing imaging IR analysis on only the second layer 6 of the insulating film 5 using a Fourier transform infrared spectrophotometer and measuring the melting peak temperature in the DSC curve of the second layer 6.

[0060] When the second layer 6 contains at least one selected from the above first group, at least one selected from the first group is detected in the imaging IR analysis.

[0061] When the second layer 6 contains at least one selected from the above first group, in the DSC curve of the second layer 6, there is one or more melting peaks at 130°C or higher and 170°C or lower. The DSC curve of the second layer 6 is measured under the same conditions as the DSC curve of the above first layer 7.

[0062] The second layer 6 of Embodiment 1 may contain any one or more of a nucleating agent, an antioxidant, a flame retardant, a tackifier, a lubricant, a filler, a crystallization accelerator, and a colorant as long as the effects of the present disclosure are not impaired.

[0063] <Third layer> In addition to the first layer 7 and the second layer 6, the insulating film 5 of Embodiment 1 may further include a third layer 8 provided on the second main surface 7b of the first layer 7. The third layer 8 has a function as an adhesive layer with the encapsulation container.

[0064] ≪Composition of the third layer≫ The third layer 8 can be composed of at least one selected from the second group consisting of homopolypropylene, block polypropylene, random polypropylene, acid-modified polypropylene, and olefin-based elastomer, or a composite of two or more selected from the second group. Examples of the acid-modified polypropylene include maleic acid-modified polypropylene, acrylic acid-modified polypropylene, and maleic anhydride-modified polypropylene.

[0065] The method for confirming that the third layer 8 is composed of at least one selected from the above second group or a composite of two or more selected from the above second group is the same as the method for confirming that the second layer 6 is composed of at least one selected from the above first group or a composite of two or more selected from the above first group.

[0066] The third layer 8 of Embodiment 1 may contain any one or more of a nucleating agent, an antioxidant, a flame retardant, a tackifier, a lubricant, a filler, a crystallization accelerator, and a colorant as long as the effects of the present disclosure are not impaired.

[0067] ≪Method for manufacturing insulating film≫ An example of the method for manufacturing the insulating film of Embodiment 1 will be described below. The method for manufacturing the insulating film of Embodiment 1 can include a step of obtaining silane-grafted polyethylene, a step of obtaining a first mixture, and a step of obtaining an insulating film.

[0068] <Step of obtaining silane-grafted polyethylene> First, polyethylene having a density of 0.92 g / cm 3 or less, a silane coupling agent, and a peroxide are heated and mixed to graft-polymerize the silane coupling agent onto the polyethylene to obtain silane-grafted polyethylene.

[0069] <Step of obtaining a first mixture> Next, the silane-grafted polyethylene, polypropylene, and a silanol condensation catalyst are heated and mixed to obtain a first mixture. The mixing ratio of the silane-grafted polyethylene and polypropylene can be 30:70 to 70:30 on a mass basis. The first mixture can contain an antioxidant in addition to the above components.

[0070] <Step of obtaining an insulating film> Next, the first mixture is extruded to obtain an insulating film including a first layer. In the step of obtaining the insulating film, by co-extruding the first mixture and acid-modified polypropylene, an insulating film having a laminated structure including the first layer and one or both of the second layer and the third layer can be obtained.

[0071] According to the above method for manufacturing an insulating film, the insulating film of Embodiment 1 can be manufactured without using irradiation rays.

[0072] [Embodiment 2: Lead wire] FIG. 3 is a perspective view of the lead wire 1 according to an embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2"). FIG. 4 is a partial cross-sectional view of the lead wire 1 according to an embodiment of the present disclosure. As shown in FIG. 3, the lead wire 1 according to an embodiment of the present disclosure includes a conductor 3 and an insulating film 5 of Embodiment 1 that covers at least a part of the outer peripheral surface of the conductor 3. As shown in FIG. 4, the insulating film 5 includes a first layer 7. As shown in FIG. 4, the insulating film 5 may have a first layer 7, a second layer 6 provided between the first layer 7 and the conductor 3, and a third layer 8 provided on a second main surface 7b opposite to a first main surface 7a where the second layer 6 of the first layer 7 is provided. The conductor 3 corresponds to a lead wire conductor.

[0073] In FIG. 4, a form of a three-layer structure in which the insulating film 5 includes a second layer 6, a first layer 7, and a third layer 8 is shown, but the number of layers included in the insulating film 5 is not limited to three layers. The insulating film 5 can be composed of a two-layer structure including a second layer 6 and a first layer 7. The insulating film 5 can include other layers in addition to the second layer 6, the first layer 7, and the third layer 8.

[0074] <Conductor> The conductor 3 is connected to an electrode of a non-aqueous electrolyte battery or the like. Examples of the material of the conductor 3 include metal materials such as aluminum, titanium, nickel, copper, aluminum alloy, titanium alloy, nickel alloy, and copper alloy, and materials obtained by plating these metal materials with nickel, gold, or the like. The conductor 3 may be subjected to a surface treatment for preventing corrosion by an electrolyte.

[0075] When the average thickness of the conductor 3 is 0.10 mm or more, a sufficient amount of current can flow in terms of practical use as a battery. When a particularly large current flows through the conductor 3, the average thickness of the conductor 3 is preferably 0.5 mm or more. In actual use, an upper limit of the average thickness of the conductor 3 of 3 mm is sufficient. In the present disclosure, the average thickness of the conductor 3 is the average value of the measured values of the thickness at five points in a cross-section along the normal direction of the main surface of the conductor.

[0076] [Embodiment 3: Non-aqueous electrolyte battery] A non-aqueous electrolyte battery according to an embodiment of the present disclosure (hereinafter also referred to as "Embodiment 3") includes the insulating film of Embodiment 1. Examples of the non-aqueous electrolyte battery include secondary batteries such as lithium-ion batteries.

[0077] FIG. 5 is a perspective view showing an example of the non-aqueous electrolyte battery of Embodiment 3. Further, FIG. 6 is a partial cross-sectional view schematically showing an embodiment of the non-aqueous electrolyte battery. The non-aqueous electrolyte battery (secondary battery) 10 shown in FIGS. 5 and 6 includes a plate-shaped positive electrode, a plate-shaped negative electrode, and a non-aqueous electrolyte (for example, a non-aqueous electrolyte solution), an encapsulation container 11, and a plurality of, specifically, two lead wires 1. The lead wire 1 is the lead wire 1 of Embodiment 2. The non-aqueous electrolyte battery 10 has a substantially rectangular encapsulation container 11 and two lead wires 1 extending from the inside to the outside of the encapsulation container 11. The conductor 3 and the encapsulation container 11 are connected at the seal portion 13 of the encapsulation container 11 via an insulating film 5. The encapsulation container 11 is a container that hermetically houses a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte solution.

[0078] In the encapsulation container 11, the seal portion 13 around two sheet bodies or a bent single sheet body is heat-sealed to be in a sealed state.

[0079] In the two lead wires 1, one lead wire 1 is arranged such that the first end portion 4a of its conductor 3 is exposed from the encapsulation container 11 and the second end portion 4b on the side opposite to the first end portion 4a is connected to the positive electrode inside the encapsulation container 11. The other lead wire 1 is arranged such that the first end portion 4a of its conductor 3 is exposed from the encapsulation container 11 and the second end portion 4b is connected to the negative electrode inside the encapsulation container 11.

[0080] At both ends of the conductor 3, that is, the first end portion 4a and the second end portion 4b, the innermost resin layer 27 of the encapsulation container 11 is not provided. At the second end portion 4b of the conductor 3 of the lead wire 1 on the positive electrode side, an internal connection lead wire 14 is connected via a solder portion 15, and this internal connection lead wire 14 is connected to a positive electrode (not shown). Similarly, at the second end portion 4b of the conductor 3 of the lead wire 1 on the negative electrode side, an internal connection lead wire 14 is connected via a solder portion 15, and this internal connection lead wire 14 is connected to a negative electrode (not shown). As shown in FIG. 6, the middle portions of these lead wires 1 are sandwiched between the sheet bodies which are the encapsulation containers 11 via an insulating film 5. At this portion, the innermost resin layer 27 of the encapsulation container 11 and the third layer 8 of the lead wire 1 are thermally fused.

[0081] As shown in FIG. 6, the encapsulation container 11 is composed of a sheet body in which an innermost resin layer 27, a metal layer 25, and an outermost resin layer 26 are laminated in this order. Then, the encapsulation container 11 is formed by overlapping two sheet bodies and thermally fusing three sides other than the sides through which the conductor 3 penetrates to form a seal portion 13. In the seal portion 13, the innermost resin layers 27 of each sheet are welded together. Also, in the seal portion 13 where the lead wire 1 is located, the insulating film 5 and the encapsulation container 11 are adhered. At this portion, the innermost resin layer 27 of the encapsulation container 11 and the third layer 8 of the lead wire 1 are thermally fused.

[0082] The innermost resin layer 27 is laminated on the inner surface of the metal layer 25 directly or with an adhesive layer or the like in between. It is preferable to use an insulating resin that does not dissolve in the electrolyte inside the battery and does not melt when heated for the innermost resin layer 27. As the innermost resin layer 27, for example, polyolefin, acid-modified polyolefin, acid-modified styrene-based elastomer, etc. can be used. Among these, polypropylene is preferable as the innermost resin layer 27. Also, the average thickness of the innermost resin layer 27 is preferably about 10 μm to 500 μm.

[0083] In FIG. 6, the insulating film 5 is shown in the form of a three-layer structure including a second layer 6, a first layer 7, and a third layer 8. However, the number of layers included in the insulating film 5 is not limited to three layers. The insulating film 5 can be composed of a two-layer structure including the second layer 6 and the first layer 7. The insulating film 5 can include other layers in addition to the second layer 6, the first layer 7, and the third layer 8.

Example

[0084] The present embodiment will be described in more detail by way of examples. However, the present embodiment is not limited by these examples.

[0085] [Fabrication of Insulating Film] The insulating films of each sample were fabricated according to the following procedure. [Step of Obtaining Silane Grafted Polyethylene] The following were prepared as raw materials. Ultra-low density PE (density: 0.87): polyethylene, density: 0.84 g / cm 3 , melting point 50 °C Low density PE (density: 0.92): polyethylene, density: 0.92 g / cm 3 , melting point 120 °C Linear PE (density: 0.95): polyethylene, density: 0.95 g / cm 3 , melting point 130 °C Silane coupling agent: vinyltrimethoxysilane Peroxide: bis(1-methyl-1-phenylethyl) peroxide Polyethylene, a silane coupling agent, and a peroxide were prepared in the ratios shown in Table 1. These were heated and mixed using a single-screw extruder at a cylinder temperature of 190 °C, a screw rotation speed of 10 rpm, and a residence time in the extruder of 5 minutes to graft-polymerize the silane coupling agent onto the polyethylene to obtain silane grafted polyethylenes (1) to (3).

[0086]

Table 1

[0087] <Step of obtaining the first mixture> As raw materials, the following were prepared. Homo-PP: Homopolypropylene, melting point 165 °C Random PP: Random polypropylene, melting point 140 °C Silanol condensation catalyst Antioxidant Next, silane-grafted polyethylene, polypropylene, a silanol condensation catalyst, and an antioxidant were prepared in the proportions described in Tables 2 and 3. These were heated and mixed in a kneader to obtain a first mixture. The conditions for the heat mixing were a temperature of 200 °C, a mixing time of 10 minutes, and a rotation speed of 50 rpm.

[0088] <Step of obtaining an insulating film> Next, the first mixture and acid-modified polypropylene were extruded to obtain an insulating film having a three-layer structure. The insulating film consisted of a first layer made of the first mixture, a second layer made of acid-modified polypropylene provided on the first major surface of the first layer, and a third layer made of acid-modified polypropylene provided on the second major surface of the first layer. In all samples, the thickness of the first layer was 50 μm, the thickness of the second layer was 25 μm, and the thickness of the third layer was 25 μm.

[0089] [Evaluation] <Measurement of DSC curve of the first layer> DSC curves of the first layer of the insulating film of each sample were created, and in the obtained DSC curves, the melting peak temperature of the first layer was measured. The specific measurement method is as described in Embodiment 1. The results are shown in the columns of "First layer: DSC curve melting peak temperature" in Tables 2 and 3. In each sample, two melting peak temperatures shown in Tables 2 and 3 were confirmed.

[0090] <Measurement of the structure of the first layer and the area percentage of the stained region> After cross-sections in the thickness direction along TD of the first layer of the insulating film of each sample were stained with a ruthenium-based dye, the tissue morphology of the stained region and the non-stained region was confirmed in the first image obtained by observing the cross-section with a transmission electron microscope. The specific confirmation method is as described in Embodiment 1. The results are shown in Tables 2 and 3.

[0091] Next, in the first image, the area percentage of the stained region was measured. The specific measurement method is as described in Embodiment 1. The results are shown in Tables 2 and 3.

[0092] <Measurement of the ratio IA / IB of the first layer> The ratio IA / IB of the peak intensity IA at a wave number of 1082 cm in the infrared absorption spectrum measured by Fourier transform infrared spectroscopy by the transmission method of the first layer of the insulating film of each sample, and the peak intensity IB after film thickness correction of the peak intensity IA was measured. The specific measurement method is as described in Embodiment 1. The results are shown in Tables 2 and 3. -1

[0093] <Measurement of the silicon content of the first layer> The silicon content of the first layer of the insulating film of each sample was measured. The specific measurement method is as described in Embodiment 1. The results are shown in Tables 2 and 3.

[0094] <Measurement of the heat deformation residual rate of the insulating film> The heat deformation residual rate of the insulating film of each sample was measured. The specific measurement method is as described in Embodiment 1. The results are shown in Tables 2 and 3. When the heat deformation residual rate is 15% or more, it is judged that the insulating film is difficult to melt during heat fusion with the lead conductor, and it is possible to prevent a short circuit between the metal layer of the encapsulation container and the lead conductor due to melting of the insulating film.

[0095] <Measurement of the gel fraction of the insulating film> The gel fraction of the insulating film of each sample was measured. The specific measurement method is as described in Embodiment 1. The results are shown in Tables 2 and 3.

[0096] <Measurement of peel strength> The peel strength of the insulating film of each sample was measured by the following method. (Fabrication of lead conductor) As a member of the lead conductor, an oxygen-free copper plate (C1020) with a length of 100 mm, a width of 45 mm, and a thickness of 0.2 mm was used. As a pretreatment, the substrate was immersed in an aqueous sodium hydroxide solution (40 g / L) at 25 °C, and cathodic electrolytic degreasing was carried out at a current density of 1.0 A / dm 2 2 . After degreasing, the substrate was washed with running water.

[0097] Next, the washed substrate was immersed in a sulfuric acid aqueous solution (10% by mass) at 25 °C for 30 seconds to perform acid activation. After acid activation, the substrate was washed with running water.

[0098] Next, nickel amidosulfate tetrahydrate (350 g / L), nickel chloride hexahydrate (30 g / L), and boric acid (30 g / L) were mixed to obtain a nickel plating solution. The substrate after acid activation was immersed in the nickel plating solution at 50 °C, and plating was carried out at a current density of 5.0 A / dm 2 2 for 120 seconds. By washing the plated substrate with running water, a lead conductor made of nickel-plated copper (nickel-plated metal) was obtained.

[0099] (Film formation) Chromium chloride hexahydrate (5.0 g / L) and potassium formate (170 g / L) were mixed in pure water to obtain a surface treatment solution. The lead conductor was immersed in the surface treatment solution at 45 °C, and cathodic electrolysis was carried out at a current density of 10 A / dm 2 2 for 30 seconds. By washing the lead conductor after cathodic electrolysis with running water, a lead conductor with a film formed thereon was obtained. The thickness of the film was 4 nm.

[0100] (Preparation of measurement sample) The lead conductor with a film formed thereon and the insulating film of each sample obtained in the above process were pressed and bonded at 220 °C for 30 seconds at 0.5 MPa to obtain a measurement sample.

[0101] (Peel strength) One of the lead conductors and the insulating film of each sample is cut and bent at 180°, and then set on a tensile testing machine (EX-SX manufactured by Shimadzu Corporation). The peeled strength was measured by pulling the set cut portion at a tensile speed of 50 mm / min. The results are shown in the "Peeled Strength (N / cm)" columns of Tables 2 to 3. When the peeled strength is 10 N / cm or more, it can be evaluated as a lead wire having high adhesiveness. Also, the peeled portions are shown in the "Peeled Portion" columns of Tables 2 to 3. Interfacial peeling indicates peeling between the conductor and the insulating film tube. Interlayer peeling indicates peeling between the first layer and the second layer, or between the first layer and the third layer.

[0102] [Table 2]

[0103] [Table 3]

[0104] [Discussion] Samples 2, 3, 6, 7, 10, and 11 correspond to the examples. Samples 1, 4, 5, 8, and 9 correspond to the comparative examples.

[0105] The samples of the examples were manufactured without using irradiation rays. Since the heat deformation residual rate of these samples is 15% or more, when used in a non-aqueous electrolyte battery, the occurrence of a short circuit between the metal layer of the encapsulation container and the conductor can be suppressed. Also, these samples have a peeled strength of 10 N / cm or more and are excellent in adhesiveness to the conductor.

[0106] As described above, the embodiments and examples of the present disclosure have been explained. However, it has been planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples and to variously modify them. The embodiments and examples disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above-described embodiments and examples but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Explanation of Reference Numerals

[0107] 1 Lead wire 3 Conductor 4a First end portion 4b Second end portion 5 Insulating film 6 Second layer 7 First layer 7a First major surface 7b Second major surface 8 Third layer 10 Non-aqueous electrolyte battery 11 Encapsulation container 13 Seal portion 14 Internal connection lead wire 15 Solder portion 25 Metal layer 26 Outermost resin layer 27 Innermost resin layer

Claims

1. An insulating film including a first layer, wherein the first layer contains a polyolefin, a part of the polyolefin is a crosslinked polyolefin, in the DSC curve of the first layer, there is one or more melting peaks at 40°C or higher and 120°C or lower, and there is one or more melting peaks at 130°C or higher and 170°C or lower, the DSC curve is obtained by measuring in the range of -50°C to 250°C at a heating rate of 10°C / min using a differential scanning calorimeter, in a first image obtained by observing a cross-section in the thickness direction along TD of the first layer after staining the cross-section with a ruthenium-based dye using a transmission electron microscope, a phase separation structure composed of a stained region and a non-stained region is observed, in the first image, the area percentage of the stained region is 10% or more and 70% or less, an insulating film, wherein the heat deformation residue rate of the insulating film is 15% or more.

2. The insulating film according to claim 1, wherein the polyolefin contains at least one selected from the group consisting of ultra-low density polyethylene, low density polyethylene, and linear polyethylene.

3. The ratio IA / IB of the peak intensity IA at a wave number of 1082 cm in the infrared absorption spectrum measured by Fourier transform infrared spectroscopy by the transmission method of the first layer －１ to the peak intensity IB after film thickness correction of the peak intensity IA is 0.20 or more, The insulating film according to claim 1 or claim 2, wherein the silicon content measured by ICP emission spectrometry of the first layer is 0.04% by mass or more and 1.0% by mass or less.

4. the first layer includes a first main surface, the insulating film further includes a second layer provided on the first main surface, the insulating film according to claim 1 or claim 2, wherein the second layer is composed of at least one selected from the first group consisting of acid-modified polypropylene and olefin-based elastomer, or a composite of two or more selected from the first group.

5. the first layer includes a second main surface opposite to the first main surface, the insulating film further includes a third layer provided on the second main surface, the insulating film according to claim 4, wherein the third layer is composed of at least one selected from the second group consisting of homopolypropylene, block polypropylene, random polypropylene, acid-modified polypropylene, and olefin-based elastomer, or a composite of two or more selected from the second group.

6. The insulating film according to claim 1 or claim 2, wherein the percentage (T1 / TA)×100 of the average thickness T1 of the first layer to the average thickness TA of the insulating film is 20% or more.

7. The gel fraction of the insulating film is 5% or more and 40% or less. The insulating film according to claim 1 or claim 2.

8. A conductor, The lead wire having the insulating film according to claim 1 or claim 2 covering at least a part of the outer peripheral surface of the conductor.

9. A battery cell including a positive electrode, a negative electrode, and an electrolyte sandwiched between the positive electrode and the negative electrode, Conductors electrically connected to each of the positive electrode and the negative electrode, An encapsulation container for encapsulating the battery cell, A part of the conductor is exposed outside the encapsulation container, An insulating film according to claim 1 or claim 2 is disposed between the conductor and the encapsulation container, A non-aqueous electrolyte battery in which the encapsulation container and the insulating film are fused.

Images