Lead and nonaqueous-electrolyte battery

Abstract

Provided is a lead comprising a conductor and an insulating film which covers at least some of the outer peripheral surface of the conductor. The insulating film comprises a plurality of layers including a first layer, which is in contact with the surface of the conductor. The first layer is a layer of an acid-modified polyolefin. The first layer has a melting peak temperature obtained by heating from 0°C to 250°C at 10 °C / min with a differential scanning calorimeter and a crystallization peak temperature obtained by cooling, after the heating, from 250°C to 0°C at -10 °C / min, the difference between the temperatures being 34°C or less. The melting peak temperature and the crystallization peak temperature are 80-170°C each.

Description

Lead-acid and non-aqueous electrolyte batteries

[0001] This disclosure relates to a lead and a non-aqueous electrolyte battery. This application claims priority to Japanese Application No. 2023-111431, filed on July 6, 2023, and incorporates by reference all of the contents of said Japanese application.

[0002] Patent Document 1 discloses a tab lead using an adhesive film for metal terminals that includes at least one resin layer having a polyolefin skeleton in order to improve adhesion between a conductor and an enclosed container. When measured with a differential scanning calorimeter, this adhesive film for metal terminals exhibits a melting peak in the range of 120°C to 156°C.

[0003] International Publication No. 2019 / 244971

[0004] The lead of the present disclosure is a lead comprising a conductor and an insulating film covering at least a portion of the outer peripheral surface of the conductor, wherein the insulating film has a plurality of layers including a first layer in contact with the surface of the conductor, the first layer being an acid-modified polyolefin layer, wherein the difference between the melting peak temperature obtained by heating the first layer from 0°C to 250°C at 10°C / min using a differential scanning calorimeter and the crystallization peak temperature obtained by cooling the first layer from 250°C to 0°C at -10°C / min after heating is 34°C or less, and the melting peak temperature and the crystallization peak temperature are each 80°C or higher and 170°C or lower.

[0005] Fig. 1 is a perspective view of a lead according to an embodiment of the present disclosure. Fig. 2 is a partial cross-sectional view of a lead according to an embodiment of the present disclosure. Fig. 3 is a perspective view showing an example of a nonaqueous electrolyte battery including a lead according to an embodiment of the present disclosure. Fig. 4 is a longitudinal cross-sectional view of the nonaqueous electrolyte battery of Fig. 3.

[0006] An object of the present disclosure is to provide a lead that exhibits excellent adhesive strength between an insulating film and a conductor even when in contact with an electrolyte solution, and a nonaqueous electrolyte battery including the lead.

[0007] According to the present disclosure, it is possible to provide a lead that has excellent adhesive strength between an insulating film and a conductor even when in contact with an electrolyte solution, and a nonaqueous electrolyte battery including the lead.

[0008] First, embodiments of the present disclosure will be described below. (1) A lead according to the present disclosure includes a conductor and an insulating film covering at least a portion of the outer peripheral surface of the conductor, the insulating film having multiple layers including a first layer in contact with the surface of the conductor, the first layer being an acid-modified polyolefin layer, the difference between the melting peak temperature obtained by heating the first layer from 0°C to 250°C at a rate of 10°C / min using a differential scanning calorimeter and the crystallization peak temperature obtained by cooling the first layer from 250°C to 0°C at a rate of -10°C / min after the heating is 34°C or less, and the melting peak temperature and the crystallization peak temperature are each 80°C or higher and 170°C or lower.

[0009] According to the present disclosure, it is possible to provide a lead that has excellent adhesive strength between an insulating film and a conductor even when in contact with an electrolyte solution, and a nonaqueous electrolyte battery including the lead.

[0010] (2) In the above (1), the crystallization peak temperature may be 100° C. or higher and 120° C. or lower, thereby further improving the adhesive strength between the insulating film and the conductor.

[0011] (3) In the above (1) or (2), the first layer may contain a nucleating agent, which further improves the adhesive strength between the insulating film and the conductor.

[0012] (4) In the above (3), the nucleating agent may include at least one selected from the group consisting of sorbitol-based nucleating agents, nonitol-based nucleating agents, amide-based nucleating agents, aromatic carboxylic acid metal salt-based nucleating agents, phosphate ester metal salt-based nucleating agents, and talc, which further improves the adhesive strength between the insulating film and the conductor.

[0013] This further improves the adhesive strength between the insulating film and the conductor.

[0014] (5) In any one of the above (1) to (4), the storage modulus of the first layer at 25° C. may be 1000 MPa or more and 1400 MPa or less.

[0015] (6) In any one of the above (1) to (5), the loss modulus of the first layer at 25° C. may be 70 MPa or more and 120 MPa or less.

[0016] (7) A nonaqueous electrolyte battery according to the present disclosure is a nonaqueous electrolyte battery including an enclosed container and a plurality of leads according to any one of (1) to (6) above, which are arranged so as to extend from the inside to the outside of the enclosed container, wherein the enclosed container is formed from a sheet body in which an innermost resin layer, a metal layer, and an outermost resin layer are laminated in the aforementioned order, and the innermost resin layer and the insulating film are fused together.

[0017] According to the present disclosure, it is possible to provide a nonaqueous electrolyte battery including a lead that has excellent adhesive strength between an insulating film and a conductor even when in contact with an electrolyte solution.

[0018] [Details of the embodiments of the present disclosure] Specific examples of the lead and nonaqueous 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 or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0019] In the present disclosure, when two or more numerical values ​​are recited as the lower limit and the upper limit of a numerical range, a combination of any one numerical value recited as the lower limit and any one numerical value recited as the upper limit is also considered to be disclosed. For example, when a1, b1, and c1 are recited as the lower limit and a2, b2, and c2 are recited as the upper limit, the following are considered to be disclosed: a1 to a2, a1 to b2, a1 to c2, b1 to a2, b1 to b2, b1 to c2, c1 to a2, c1 to b2, and c1 to c2.

[0020] [Embodiment 1: Lead] Fig. 1 is a perspective view of a lead 1 according to an embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1"). Fig. 2 is a partial cross-sectional view of the lead 1 according to an embodiment of the present disclosure. As shown in Figs. 1 and 2, the lead 1 according to an embodiment of the present disclosure includes a conductor 3 and an insulating film 5 covering at least a portion of the outer peripheral surface of the conductor 3. The insulating film 5 has multiple layers including a first layer 6 in contact with the surface of the conductor 3. As shown in Fig. 2, the insulating film 5 may include, in order from the first layer 6 in contact with the surface of the conductor 3, a second layer 7 in contact with the surface of the first layer 6 and a third layer 8 in contact with the surface of the second layer 7. The conductor 3 corresponds to a lead conductor.

[0021] 2 shows the insulating film 5 having a three-layer structure including a first layer 6, a second layer 7, and a third layer 8, but the number of layers included in the insulating film 5 is not limited to three. The insulating film 5 may also have a two-layer structure including the first layer 6 and the second layer 7. The insulating film 5 may also include other layers in addition to the first layer 6, the second layer 7, and the third layer 8.

[0022] <Conductor> The conductor 3 is connected to the electrodes of the nonaqueous electrolyte battery. Examples of materials for the conductor 3 include metal materials such as aluminum, titanium, nickel, copper, aluminum alloys, titanium alloys, nickel alloys, and copper alloys, as well as materials obtained by plating these metal materials with nickel, gold, or the like. The conductor 3 may be subjected to a surface treatment to prevent corrosion by the electrolyte.

[0023] When the average thickness of the conductor 3 is 0.10 mm or more, a sufficient current can be passed through the conductor 3 for practical use as a battery. The average thickness of the conductor 3 may be 0.5 mm or more. In this case, a particularly large current can be passed through the conductor 3. In practical use, an upper limit of the average thickness of the conductor 3 is sufficient if it is 3 mm. In the present disclosure, the average thickness of the conductor 3 is the average value of thickness measurements at five points on a cross section along the normal direction of the main surface of the conductor.

[0024] <Insulating Film> The insulating film 5 is used as an insulating film for the lead 1. The insulating film 5 has a plurality of layers, and is provided on the outer peripheral surface of the conductor 3 so as to cover at least a part of the outer peripheral surface of the conductor 3.

[0025] When the average thickness of the insulating film 5 is 0.02 mm or more, no gaps are formed between the conductor 3 and the sealing container 11, and the insulating film 5 can fill the gap. The upper limit of the average thickness of the insulating film 5 is 0.30 mm.

[0026] In the present disclosure, the average thickness of the insulating film 5 is measured by the following procedure. The insulating film 5 is cut using a microtome or the like along the normal direction of the surface with the largest area among the outer peripheral surfaces of the insulating film 5 to expose the cross section. The cross section is observed at 250x magnification using a digital microscope, and the thickness of the insulating film 5 is measured at five locations. The average of the thicknesses at the five locations 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 6, second layer 7, and third layer 8 described below are also measured in the same manner.

[0027] As long as measurements were made on the same sample, it was confirmed that there was almost no variation in the measurement results even if the cutting position of the insulating film was arbitrarily set.

[0028] <Composition of First Layer> The first layer 6 is an acid-modified polyolefin layer. The first layer 6 has good adhesiveness to the conductor and can fully exhibit adhesiveness to the second layer 7.

[0029] Acid-modified polyolefins are polyolefins containing acid-modifying groups that have been modified with carboxylic acids such as maleic acid, acrylic acid, methacrylic acid, and maleic anhydride. Acid-modified polyolefins may also be acid-modified polypropylene. Examples of acid-modified polyolefins include maleic acid-modified polypropylene, acrylic acid-modified polypropylene, maleic anhydride-modified polypropylene, acrylic acid-modified polyethylene, maleic anhydride-modified polyethylene, and acrylic acid-modified ethylene acrylate.

[0030] The first layer 6 may be an acid-modified polypropylene layer. This provides the first layer 6 with excellent adhesion and sealing properties to metals. The first layer 6 may be a maleic anhydride-modified polypropylene layer. This provides the first layer 6 with extremely excellent adhesion and sealing properties to metals.

[0031] The first layer 6 may contain an unmodified polyolefin together with the acid-modified polyolefin as a resin component, as long as the effects of the present disclosure are not impaired. Hereinafter, the acid-modified polyolefin and the unmodified polyolefin will also be collectively referred to as polyolefin.

[0032] The presence of the acid-modified group in the first layer 6 can be confirmed by subjecting the insulating film 5 to a transmitted light analysis using a Fourier transform infrared spectrophotometer (FT-IR).

[0033] The content of the acid-modified polyolefin in the first layer 6 may be 3% by mass or more. In terms of adhesion to the conductor, the content of the acid-modified polyolefin may be high. In terms of sufficient adhesion to the conductor, the acid-modified polyolefin may be contained in an amount of 60% by mass or more.

[0034] The acid-modified polyolefin layer may contain a rubber component. The acid-modified polyolefin layer may contain at least one selected from the group consisting of ethylene propylene rubber, ethylene butene rubber, ethylene octene rubber, and propylene butene rubber. Among these, ethylene propylene rubber has excellent dispersibility in acid-modified polyolefins, especially acid-modified polypropylene. When the acid-modified polyolefin layer contains ethylene propylene rubber, the adhesive strength between the insulating film 5 and the conductor is further improved.

[0035] The first layer 6 of embodiment 1 may contain one or more of a crystal 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.

[0036] <Melting Peak Temperature Tm and Crystallization Peak Temperature Tc of First Layer> The difference Tm - Tc between the melting peak temperature Tm [°C] obtained by heating the first layer 6 from 0°C to 250°C at 10°C / min using a differential scanning calorimeter and the crystallization peak temperature Tc [°C] obtained by cooling the first layer 6 from 250°C to 0°C at -10°C / min after heating is 34°C or less. The melting peak temperature Tm and the crystallization peak temperature Tc are each 80°C or higher and 170°C or lower. When the first layer 6 has two or more melting peaks in the range of 80°C or higher and 170°C or lower, the temperature of the melting peak with the largest peak height is taken as the melting peak temperature Tm. When the first layer 6 has two or more crystallization peaks in the range of 80°C or higher and 170°C or lower, the temperature of the crystallization peak with the largest peak height is taken as the crystallization peak temperature Tc.

[0037] The difference Tm-Tc between the melting peak temperature Tm and the crystallization peak temperature Tc is 34°C or less from the viewpoint of improving the adhesive strength between the insulating film 5 and the conductor 3. Since the first layer is polyolefin, the difference Tm-Tc is 25°C or more.

[0038] The melting peak temperature Tm may be 130° C. or higher. The melting peak temperature Tm may be 170° C. or lower.

[0039] The crystallization peak temperature Tc may be 80° C. or higher, or 130° C. or lower.

[0040] The first layer 6 may have a melting peak and a crystallization peak in the range of 80°C or higher and 170°C or lower, and may also have one or both of a melting peak and a crystallization peak outside the range of 80°C or higher and 170°C or lower.

[0041] From the viewpoint of improving the adhesive strength between the insulating film 5 and the conductor 3, the half width of the crystallization peak indicating the crystallization peak temperature Tc may be 5.0°C or higher, 5.5°C or higher, 6.0°C or higher, 6.5°C or higher, 6.6°C or higher, 6.7°C or higher, 6.8°C or higher, 7.0°C or higher, or 7.5°C or higher. The upper limit of the half width of the crystallization peak indicating the crystallization peak temperature Tc may be, for example, 10°C. In the present disclosure, the half width refers to the full width at half maximum (FWHM).

[0042] In the present disclosure, the melting peak temperature Tm, crystallization peak temperature Tc, and half-width of the crystallization peak of the first layer 6 are measured using a differential scanning calorimeter in accordance with JIS K 7121-1987, "Method for measuring transition temperatures of plastics." Specifically, the first layer 6 is removed from the insulating film 5, and the DSC (Differential Scanning Calorimetry) curve is obtained by heating from 0°C to 250°C at a rate of 10°C / min in a differential scanning calorimeter. The maximum melting peak temperature of 80°C or higher and 170°C or lower in the DSC curve obtained by heating and then cooling from 250°C to 0°C at a rate of -10°C / min corresponds to the crystallization peak temperature Tc of the first layer. In the present disclosure, the half-width of the peak indicating the crystallization peak temperature Tc corresponds to the half-width of the crystallization peak.

[0043] <Nucleating Agent> The first layer 6 may contain a nucleating agent. Examples of the nucleating agent include organic nucleating agents and inorganic nucleating agents. Examples of the organic nucleating agent include sorbitol nucleating agents, nonitol nucleating agents, amide nucleating agents, aromatic carboxylic acid metal salt nucleating agents, and phosphate ester metal salt nucleating agents.

[0044] Examples of sorbitol-based crystal nucleating agents include dibenzylidene sorbitol (DBS), monomethyldibenzylidene sorbitol (e.g., 1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol), and dimethyldibenzylidene sorbitol (e.g., 1,3:2,4-bis(3,4-dimethylbenzylidene)sorbitol (3,4-DMDBS)).

[0045] Examples of nonitol-based crystal nucleating agents include 1,2,3-trideoxy-4,6:5,7-bis-[(4-propylphenyl)methylene]-nonitol.

[0046] Examples of amide-based crystal nucleating agents include 1,3,5-tris(2,2-dimethylpropaneamino)benzene.

[0047] Examples of the aromatic carboxylic acid metal salt nucleating agent include sodium benzoate and calcium salt of 1,2-cyclohexanedicarboxylate.

[0048] Examples of the phosphate metal salt nucleating agent include sodium phosphate.

[0049] An example of an inorganic crystal nucleating agent is talc.

[0050] The nucleating agent contained in the first layer 6 may include at least one selected from the group consisting of a sorbitol-based nucleating agent, a nonitol-based nucleating agent, an amide-based nucleating agent, an aromatic carboxylic acid metal salt-based nucleating agent, a phosphate ester metal salt-based nucleating agent, and talc. The nucleating agent contained in the first layer 6 may be a sorbitol-based nucleating agent.

[0051] The inclusion of a nucleating agent in the first layer 6 can be confirmed by the following procedure. The first layer 6 is removed from the insulating film 5 to prepare a sample. Next, the sample formed from the first layer 6 is heated (e.g., at 120°C) and / or immersed (e.g., for 12 hours) in an organic solvent such as chloroform, N-methylpyrrolidone (NMP), or dimethyl sulfoxide (DMSO) to extract the nucleating agent. The freezing points of the sample before and after extraction are then measured by DSC. If the freezing point of the sample before the extraction of the nucleating agent is higher (e.g., by 4°C or more) than the freezing point of the sample after the extraction of the nucleating agent, it is confirmed that the first phase 6 contains a nucleating agent.

[0052] The content of the nucleating agent in the first layer 6 can be adjusted appropriately depending on the type of nucleating agent. For example, the lower limit of the mass percentage of the nucleating agent relative to the total mass of the acid-modified polyolefin may be 0.30 mass%, 0.40 mass%, 0.50 mass%, 0.60 mass%, or 1.0 mass%, from the viewpoint of improving the adhesive strength between the insulating film 5 and the conductor. The nucleating agent may be dispersed in the film so as not to be observed as a foreign substance, and the mass percentage of the nucleating agent relative to the total mass of the acid-modified polyolefin may be, for example, 3.0 mass% or less. The mass percentage of the nucleating agent relative to the total mass of the acid-modified polyolefin is measured by FT-IR or liquid chromatography.

[0053] <Storage Modulus and Loss Modulus> The storage modulus of the first layer 6 at 25° C. may be 1000 MPa or more and 1400 MPa or less, from the viewpoint of making the insulating film less likely to deform.

[0054] The loss modulus of the first layer 6 at 25° C. may be 70 MPa or more and 120 MPa or less, from the viewpoint of preventing the insulating film from peeling off the conductor.

[0055] In the present disclosure, the storage modulus and loss modulus of the first layer 6 at 25°C are measured by the following procedure. A nanoindenter with a regular triangular pyramidal indenter (Berkovich indenter) with a diamond tip is used. The insulating film 5 is cut with a microtome or the like along the normal to the principal surface, which is the surface with the largest area among the outer peripheral surfaces of the insulating film 5, and the cross section of the insulating film 5 is exposed by Ar ion milling. Next, a nanoindenter (Hysitron TI 980 Nanoindenter, manufactured by Bruker) is used to press the indenter perpendicular to the cross section of the insulating film 5, and the storage modulus and loss modulus are calculated by dynamic viscoelasticity measurement. The dynamic viscoelasticity measurement is performed at a measurement frequency of 10 Hz and 25°C, with the displacement amplitude adjusted to 0.5 nm or more and 2 nm or less when the indenter is pressed with a force of 8 mN.

[0056] The above measurement is performed at three locations, and the average of the storage modulus values ​​at the three locations and the average of the loss modulus values ​​at the three locations are calculated. In the present disclosure, the average of the storage modulus values ​​at the three locations corresponds to the storage modulus of the first layer 6. In the present disclosure, the average of the loss modulus values ​​at the three locations corresponds to the loss modulus of the first layer 6.

[0057] As far as the applicant has measured, it has been confirmed that, as long as measurements are taken on the same sample, even if the cutting and measurement locations of the insulating film are arbitrarily set, the standard deviations of the storage modulus and loss modulus are 2% or less and 10% or less of the values, respectively, and there is almost no variation in the measurement results.

[0058] <Average Thickness of First Layer> The average thickness of the first layer 6 may be 10 μm or more. This allows the insulating film 5 to fill and fill the gap between the conductor and the sealed container 11 without creating any gaps. The upper limit of the average thickness of the first layer 6 may be 150 μm. This reduces the amount of moisture that permeates the insulating film 5 from the atmosphere and enters the interior of the nonaqueous electrolyte battery.

[0059] <Second Layer> The insulating film 5 may include a second layer 7 that is in contact with the surface of the first layer 6 and that sandwiches the first layer 6 between the conductor 3. In the insulating film 5 of the lead 1 of embodiment 1, the second layer 7 is a heat-resistant resin layer. The second layer 7 functions as a support for the insulating film 5.

[0060] Examples of the heat-resistant resin that forms the second layer 7 include cross-linked polyolefin and polyolefin having a melting point 10°C or more higher than that of the first layer 6. The second layer 7 is unlikely to melt at the heat-sealing temperature when the opening of the sealed container is heat-sealed, and can prevent a short circuit between the metal layer of the sealed container and the conductor 3.

[0061] The crosslinked polyolefin may be a crosslinked random polypropylene having a melting point of 130° C. or higher and 155° C. or lower and a melt flow rate (MFR) of 3 g / 10 min or higher and 15 g / 10 min or lower, which allows the second layer 7 to exhibit sufficient adhesion to the first layer 6, the third layer 8, or the enclosed container, and is unlikely to melt at heat sealing temperatures.

[0062] Examples of high-melting-point polyolefins include polypropylenes having a melting point of 155° C. or higher. Examples of high-melting-point polyolefins include homopolypropylene, block polypropylene, and thermoplastic olefin elastomers (TPO).

[0063] The fact that the second layer 7 contains polyolefin can be confirmed by performing transmission light analysis on only the second layer 7 of the insulating film 5 using a Fourier transform infrared spectrophotometer. The above-mentioned transmission light analysis may be performed on the second layer 7 removed from the insulating film 5. Alternatively, the second layer 7 may be analyzed using gas chromatography-mass spectrometry.

[0064] The lower limit of the content of the crosslinked polyolefin in the second layer 7 may be 60% by mass, which provides heat resistance sufficient for practical use. The upper limit of the content of the crosslinked polyolefin in the second layer 7 may be 100% by mass.

[0065] The second layer 7 may contain a thermoplastic resin other than the above-described crosslinked polyolefin and other known additives, such as antioxidants, flame retardants, tackifiers, lubricants, fillers, crystal nucleating agents, and colorants, as long as the effects of the present disclosure are not impaired.

[0066] The lower limit of the average thickness of the second layer 7 may be 10 μm, which ensures sufficient strength of the second layer 7. The upper limit of the average thickness of the second layer 7 may be 250 μm, which reduces the amount of moisture that permeates the second layer 7 from the atmosphere and enters the interior of the nonaqueous electrolyte battery.

[0067] <Third Layer> The insulating film 5 may include, in order from a first layer 6 in contact with the surface of the conductor 3, a second layer 7 in contact with the surface of the first layer 6, and a third layer 8 in contact with the surface of the second layer 7. The third layer 8 is a layer that serves to improve adhesion to the enclosed container.

[0068] Examples of resins that can form the third layer 8 include polyolefin resins, polyethylene terephthalate, and polyamide. These resins are easily melted at the heat-sealing temperature when the opening of the sealed container is heat-sealed (thermally fused). The resin that forms the third layer 8 may be a polyolefin resin. Polyolefin resins are particularly easily melted at the heat-sealing temperature.

[0069] Examples of polyolefins include polypropylene, polyethylene, and derivatives thereof. Examples of polypropylene include random polypropylene having a melting point of 120°C or higher and 155°C or lower and an MFR of 3 g / 10 min or higher and 15 g / 10 min or lower. The random polypropylene used as the polyolefin has the advantage of being able to fully exhibit adhesion between the second layer 7 and the innermost resin layer of the sealed container.

[0070] The content of polyolefin in the third layer 8 may be 60% by mass or more, which provides sufficient material properties for practical use.

[0071] The third layer 8 may contain a thermoplastic resin other than the polyolefin as long as the effects of the present disclosure are not impaired. More specifically, the third layer 8 may contain a plurality of resins, and examples of these plurality of resins include combinations of homopolypropylene, block polypropylene, random polypropylene, low-crystalline polypropylene, low-density polyethylene, linear low-density polyethylene, low-crystalline ethylene-propylene copolymer, low-crystalline ethylene-butylene copolymer, low-crystalline ethylene-octene copolymer, low-crystalline propylene-ethylene copolymer, ethylene-propylene rubber, ethylene-propylene diene rubber, and the like.

[0072] The third layer 8 may contain other known additives as long as they do not impair the effects of the present disclosure. Examples of known additives include antioxidants, flame retardants, tackifiers, lubricants, fillers, crystallization accelerators, and colorants.

[0073] The average thickness of the third layer 8 may be 10 μm or more, which provides sufficient mechanical strength in the usage environment. The upper limit of the average thickness of the third layer 8 may be 250 μm, which reduces the amount of moisture that permeates the third layer 8 from the atmosphere and enters the interior of the nonaqueous electrolyte battery.

[0074] <Other Layers> In the first embodiment, the insulating film 5 may include one or more other layers in addition to the first layer 6, the second layer 7, and the third layer 8. Examples of the other layers include a layer that serves to strengthen the adhesion between the second layer and the third layer. The average thickness of each of the one or more other layers may be 5 μm or more.

[0075] In the present disclosure, the other layers may contain various additives such as flame retardants, ultraviolet absorbers, light stabilizers, heat stabilizers, lubricants, and colorants.

[0076] <Method for Manufacturing Lead> An example of a method for manufacturing the lead 1 of the first embodiment will be described below.

[0077] Raw material compositions containing the resin components and additives for the first layer 6, second layer 7, and third layer 8 are mixed using a known mixer such as an open roll, pressure kneader, single-screw mixer, or twin-screw mixer. Next, when producing each layer, the raw material compositions for each layer are extrusion-molded using T-die molding, inflation molding, or other methods to produce film-like first layer 6, second layer 7, and third layer 8. The insulating film 5 is then produced by overlapping the first layer 6, second layer 7, and third layer 8 and thermally laminating them together using a heated roll. Methods for simultaneously forming multiple layers include co-extrusion inflation and T-die methods. Furthermore, an extrusion lamination method can be used in which a molten resin is laminated on a single-layer film.

[0078] [Embodiment 2: Nonaqueous Electrolyte Battery] A nonaqueous electrolyte battery according to an embodiment of the present disclosure (hereinafter also referred to as "Embodiment 2") includes the lead 1 of Embodiment 1. Examples of the nonaqueous electrolyte battery include secondary batteries such as lithium ion batteries.

[0079] FIG. 3 is a perspective view showing an example of a nonaqueous electrolyte battery including the lead 1 of the first embodiment. FIG. 4 is a partial cross-sectional view schematically showing one embodiment of the nonaqueous electrolyte battery. The nonaqueous electrolyte battery 10 shown in FIGS. 3 and 4 is a secondary battery and includes a plate-shaped positive electrode, a plate-shaped negative electrode, and a nonaqueous electrolyte (e.g., a nonaqueous electrolyte solution), not shown, an enclosed container 11, and multiple, specifically, two, leads 1. The nonaqueous electrolyte battery 10 includes the substantially rectangular enclosed container 11 and the two leads 1 extending from the inside to the outside of the enclosed container 11. The conductor 3 and the enclosed container 11 are connected to a seal portion 13 of the enclosed container 11 via an insulating film 5. The enclosed container 11 is a container that accommodates the positive electrode, the negative electrode, the separator, and the nonaqueous electrolyte solution in a sealed state.

[0080] The sealed container 11 is made of two sheets or a folded sheet that are heat-sealed around the periphery to form a seal portion 13, thereby creating a sealed state.

[0081] One of the two leads 1 is arranged so that a first end 4a of the conductor 3 thereof is exposed from the sealed container 11 and a second end 4b opposite to the first end 4a is connected to the positive electrode inside the sealed container 11. The other lead 1 is arranged so that the first end 4a of the conductor 3 thereof is exposed from the sealed container 11 and the second end 4b is connected to the negative electrode inside the sealed container 11.

[0082] The innermost resin layer 27 of the sealed container 11 is not provided at both end portions of the conductor 3, i.e., the first end 4a and the second end 4b. An internal connection lead 14 is connected to the second end 4b of the conductor 3 of the lead 1, which connects to the positive electrode, via a solder portion 15, and the second end 4b is electrically connected to a positive electrode (not shown) via this internal connection lead 14. Also, an internal connection lead 14 is connected to the second end 4b of the conductor 3 of the lead 1, which connects to the negative electrode, via a solder portion 15, and the second end 4b is electrically connected to a negative electrode (not shown) via this internal connection lead 14. As shown in FIG. 4 , the conductor 3 and the insulating film 5 are sandwiched between the sheet body, which is the sealed container 11, in the middle portion of the lead 1, and the innermost resin layer 27 of the sealed container 11 and the third layer 8 of the lead 1 are heat-sealed in this portion.

[0083] As shown in Fig. 4, the sealed container 11 is formed from 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. Two sheets are then overlapped, and the three sides other than the side through which the conductor 3 passes are heat-sealed to form a sealed portion 13. In the sealed portion 13, the innermost resin layers 27 of the sheets are welded together. In addition, in the sealed portion 13 where the lead 1 is located, the insulating film 5 and the sealed container 11 are bonded. In this portion, the innermost resin layer 27 of the sealed container 11 and the third layer 8 of the lead 1 are heat-sealed.

[0084] The innermost resin layer 27 is laminated directly on the inner surface of the metal layer 25 or via an adhesive layer or the like. The innermost resin layer 27 may be made of an insulating resin that does not dissolve in the electrolyte in the battery and that melts when heated. For example, polyolefin, acid-modified polyolefin, acid-modified styrene-based elastomer, etc. may be used for the innermost resin layer 27. Among these, polypropylene may be used for the innermost resin layer 27. The average thickness of the innermost resin layer 27 may be approximately 10 μm to 500 μm. In other words, the lower limit of the average thickness of the innermost resin layer 27 may be approximately 10 μm and the upper limit may be approximately 500 μm.

[0085] The nonaqueous electrolyte battery 10 of the second embodiment uses the lead 1 of the first embodiment, and therefore has excellent adhesive strength between the insulating film 5 and the conductor 3 even when in contact with the electrolyte.

[0086] [Method for Manufacturing Nonaqueous Electrolyte Battery] A method for manufacturing the nonaqueous electrolyte battery 10 includes, for example, a step of preparing a lead 1, a step of preparing a stacked electrode group, a step of preparing a nonaqueous electrolyte, and a step of housing the stacked electrode group to which the lead 1 is connected and the nonaqueous electrolyte in an enclosed container 11.

[0087] The nonaqueous electrolyte battery 10 of Embodiment 2 includes the lead 1 described above, and therefore has excellent adhesion between the conductor 3 and the insulating film 5, which can prevent moisture from entering the battery through this portion (between the conductor and the sealed container) and prevent the nonaqueous electrolyte from leaking from the battery.

[0088] [Other embodiments] In embodiments 1 and 2, the lead 1 has an insulating film 5 with a three-layer structure having a first layer 6, a second layer 7, and a third layer 8, but the lead 1 may have a two-layer structure having a first layer 6 and a second layer 7, or may have an insulating film 5 with a multi-layer structure having one or more intermediate layers between the first layer 6 and the second layer 7.

[0089] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0090] [Preparation of First Layer Raw Material Composition] An aluminum plate having a length of 50 mm, a width of 50 mm and a thickness of 0.5 mm was prepared as a conductor.

[0091] A first layer raw material composition was prepared by adding and kneading a sorbitol-based nucleating agent, 1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol (referred to as "nucleating agent" in Table 1), to an acid-modified polypropylene containing 30% by mass of rubber (referred to as "acid-modified polypropylene" in Table 1). The first layer raw material composition was a mixture of acid-modified polypropylene and the nucleating agent. The blending amount of the sorbitol-based nucleating agent relative to 100% by mass of acid-modified polypropylene in each of Samples 1 to 6 is shown in the "Nucleating Agent" column of the "First Layer Raw Material" in Table 1. For example, in Sample 3, 0.3% by mass of the nucleating agent was added relative to 100% by mass of acid-modified polypropylene.

[0092] [Evaluation of First Layer] <Melting Peak Temperature Tm, Crystallization Peak Temperature Tc, and Half-Width of Crystallization Peak> For film samples consisting only of the first layer raw material composition (each of Samples 1 to 6 listed in Table 1), the melting peak temperature Tm, crystallization peak temperature Tc, and half-width of the crystallization peak temperature Tm were measured using a differential scanning calorimeter. Here, "consisting only of" may include inevitable impurities, and the same applies to "consisting only of" hereinafter. Specific measurement methods are as described in Embodiment 1. The results are shown in the "Tm," "Tc," and "Crystallization Peak Half-Width" columns of "First Layer" in Table 1. The difference Tm - Tc between the melting peak temperature Tm and the crystallization peak temperature Tc is shown in the "Tm - Tc" column in Table 1.

[0093] The following film samples 7 to 9 were prepared, and their Tm-Tc values ​​were measured. The composition and Tm-Tc of each film sample are shown below. Film sample 7: A film sample consisting solely of a composition in which 1.0% by mass of the nucleating agent was added to 100% by mass of the acid-modified polypropylene. The Tm-Tc was 29.5°C. Film sample 8: A film sample consisting solely of a composition in which 3.0% by mass of the nucleating agent was added to 100% by mass of the acid-modified polypropylene. The Tm-Tc was 29.3°C. Film sample 9: A film sample consisting solely of a composition in which 5.0% by mass of the nucleating agent was added to 100% by mass of the acid-modified polypropylene. The Tm-Tc was 30.0°C.

[0094]

[0095] <Storage Modulus and Loss Modulus> The storage modulus and loss modulus at 25°C were measured using a nanoindenter for film samples consisting only of the first layer raw material composition of Sample 1 and Sample 5. The specific measurement method is as described in embodiment 1.

[0096] The storage modulus was 1256 MPa for Sample 1 and 1305 MPa for Sample 5. The loss modulus was 97 MPa for Sample 1 and 107 MPa for Sample 5.

[0097] [Preparation of Peel Strength Test Samples] The first and second layers were each formed by extrusion molding. The second layer was a cross-linked insulating film primarily composed of polypropylene. The first and second layers were bonded together to obtain an insulating film. The insulating film had a thickness of 100 μm.

[0098] The insulating film was cut to prepare two insulating films (a first insulating film and a second insulating film) measuring 70 mm in length and 10 mm in width. The conductor was sandwiched between the first insulating film and the second insulating film, and heat-sealed at a mold temperature of 220°C and a surface pressure of 0.3 MPa. The first layer of the insulating film was positioned so as to contact the conductor. This resulted in a peel strength test sample for each sample, in which at least a portion of the outer periphery of the conductor was covered with the insulating film.

[0099] <Peel Strength Test> Pure water was added to a lithium ion battery electrolyte solution to a concentration of 100 ppm by mass to obtain a test solution. Each peel strength test specimen was immersed in the test solution and maintained for 48 hours. The temperature of the test solution was maintained at 60°C. After 48 hours, each peel strength test specimen was removed from the test solution, washed with lithium ion battery electrolyte, and dried at room temperature for 1 hour. A peel strength test was then performed according to the following procedure.

[0100] The second insulating film and the conductor were cut along the normal direction of the main surface of the insulating film of the peel strength test sample, without cutting the first insulating film. At the position where the second insulating film and the conductor were cut, the peel strength test sample was folded back so that the first insulating films faced each other.

[0101] The tensile tester's chuck spacing was set to 20 mm. A metal flat chuck with file marks was used. The upper chuck gripped the folded end of the conductor, while the lower chuck gripped the remaining end. The upper chuck was operated to achieve a 180° peel. The peel test was performed at a peel speed of 50 mm / min and a pulling distance of 30 mm, and the relationship between displacement and peel strength was measured. The average peel strength was calculated within the range of displacement where the tensile strength readings stabilized (approximately 5 mm to 30 mm). The relative values ​​of the average peel strengths of the peel strength test specimens for each sample, relative to the average peel strength of the peel strength test specimen for Sample 1 (= 1.00), are shown in the "Relative Peel Strength Value" column under "Insulating Film" in Table 1. A higher relative value indicates a stronger adhesive strength between the conductor and the insulating film (first insulating film).

[0102] [Discussion] Peel strength test samples 3 to 6 correspond to examples. Peel strength test samples 1 and 2 correspond to comparative examples. Peel strength test samples 3 to 6 have a difference Tm - Tc between the melting peak temperature Tm and the crystallization peak temperature Tc of the first layer of 34°C or less. It was confirmed that peel strength test samples 3 to 6 have a higher adhesive strength between the conductor and the insulating film than peel strength test samples 1 and 2, even when in contact with an electrolyte.

[0103] It is believed that the larger the storage modulus or loss modulus of an insulating film, the stronger the adhesive strength.

[0104] Although the embodiments and examples of the present disclosure have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined and modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0105] REFERENCE SIGNS LIST 1 Lead 3 Conductor 4a First end 4b Second end 5 Insulating film 6 First layer 7 Second layer 8 Third layer 10 Non-aqueous electrolyte battery 11 Enclosure 13 Sealing portion 14 Internal connection lead 15 Solder portion 25 Metal layer 26 Outermost resin layer 27 Innermost resin layer

Claims

1. A lead comprising a conductor and an insulating film covering at least a portion of the outer surface of the conductor, The insulating film has a plurality of layers, including a first layer that is in contact with the surface of the conductor. The aforementioned layer is an acid-modified polyolefin layer, The difference between the melting peak temperature obtained by heating the aforementioned first layer from 0°C to 250°C at a rate of 10°C / min using a differential scanning calorimeter and the crystallization peak temperature obtained by cooling from 250°C to 0°C at a rate of -10°C / min is 34°C or less. The melting peak temperature and the crystallization peak temperature are, respectively, 80°C to 170°C.

2. The lead according to claim 1, wherein the crystallization peak temperature is 100°C or higher and 120°C or lower.

3. The lead according to claim 1 or claim 2, wherein the first layer comprises a crystal nucleating agent.

4. The lead according to claim 3, wherein the nucleating agent comprises at least one selected from the group consisting of sorbitol-based nucleating agents, nonitol-based nucleating agents, amide-based nucleating agents, aromatic carboxylic acid metal salt-based nucleating agents, phosphate ester metal salt-based nucleating agents, and talc.

5. The lead according to claim 1 or 2, wherein the storage modulus of the first layer at 25°C is 1000 MPa or more and 1400 MPa or less.

6. The lead according to claim 1 or claim 2, wherein the loss modulus of the first layer at 25°C is 70 MPa or more and 120 MPa or less.

7. A non-aqueous electrolyte battery comprising a sealed container and a plurality of leads according to claim 1 or 2 arranged to extend from the inside to the outside of the sealed container, The aforementioned sealed container is formed from a sheet body in which the innermost resin layer, the metal layer, and the outermost resin layer are laminated in that order. A non-aqueous electrolyte battery in which the innermost resin layer and the insulating film are fused together.