Lead wire for nonaqueous electrolyte battery, insulating film, and nonaqueous electrolyte battery

Abstract

A lead wire for a nonaqueous electrolyte battery according to the present disclosure comprises a tabular conductor, and an insulating film having one or a plurality of layers and covering the outer peripheral surface of the conductor. The insulating film has a surface layer including a thermoplastic resin, said surface layer having an elastic modulus at 23°C of 600 MPa or less, as measured using a nanoindenter.

Description

Lead wire for non-aqueous electrolyte battery, insulating film and non-aqueous electrolyte battery

[0001] This disclosure relates to a lead wire for a nonaqueous electrolyte battery, an insulating film, and a nonaqueous electrolyte battery. This application claims priority to Japanese Application No. 2022-018250, filed February 8, 2022, and incorporates by reference all of the contents of that application.

[0002] As electronic devices become smaller and lighter, the batteries, capacitors, and other electrical components used in these devices are also required to be smaller and lighter. To this end, for example, a pouch is used as an enclosed container. One end of the enclosed container is an opening, and a nonaqueous electrolyte, a positive electrode plate, a negative electrode plate, a separator, and the like are enclosed within the opening. Lead conductors, one end of which is connected to the positive electrode plate and the negative electrode plate, are arranged to extend from the inside to the outside of the enclosed container. Finally, the opening is heat-sealed (thermally fused) to close the opening of the enclosed container and to bond the enclosed container and the lead conductors together to seal the opening. The final heat-sealed portion is called the sealed portion.

[0003] The lead conductor is covered with an insulating film at the portion corresponding to the seal, and the combination of the insulating film and the lead conductor is called a lead for a nonaqueous electrolyte battery (tab lead). The sealed container and the lead conductor are bonded (thermally fused) via the insulating film.

[0004] As an example of such a tab lead wire, Patent Document 1 discloses a lead wire for a nonaqueous electrolyte battery in which a composite coating layer is formed by applying a treatment liquid containing a resin component including polyacrylic acid and polyacrylic acid amide and a metal salt to a lead wire conductor, and an insulator is provided on the outside of this composite coating layer.

[0005] Japanese Patent Application Laid-Open No. 2006-128096

[0006] A lead wire for a non-aqueous electrolyte battery according to one embodiment of the present disclosure includes a flat conductor and an insulating film having one or more layers and covering an outer peripheral surface of the conductor, the insulating film having a surface layer containing a thermoplastic resin, and the surface layer having a modulus of elasticity at 23° C. measured with a nanoindenter of 600 MPa or less. The insulating film according to one embodiment of the present disclosure is an insulating film constituting a part of a lead wire for a non-aqueous electrolyte battery, the insulating film having a first layer constituting a surface, the first layer containing a thermoplastic resin, and the first layer having a modulus of elasticity at 23° C. measured with a nanoindenter of 600 MPa or less.

[0007] Fig. 1 is a partial cross-sectional view of a lead wire for a nonaqueous electrolyte battery according to an embodiment of the present disclosure. Fig. 2 is a perspective view showing an example of a nonaqueous electrolyte battery including the lead wire for a nonaqueous electrolyte battery of Fig. 1. Fig. 3 is a longitudinal cross-sectional view of the nonaqueous electrolyte battery of Fig. 2. MODES FOR CARRYING OUT THE DISCLOSURE

[0008] [Problem to be Solved by the Present Disclosure] As electronic devices become smaller and lighter, there is a demand for smaller and lighter electrical components, such as batteries and capacitors, used in these devices. For this reason, for example, nonaqueous electrolyte batteries have been adopted, in which a bag is used as a sealed container and a nonaqueous electrolyte (electrolytic solution), a positive electrode, and a negative electrode are sealed inside the bag. The nonaqueous electrolyte is LiPF ６ , LiBF ４ An electrolyte solution in which a fluorine-containing lithium salt such as the above is dissolved in propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, or the like is used.

[0009] The sealed container is required to have properties that prevent the permeation of electrolyte and gas and the intrusion of moisture from the outside. For this reason, a laminate film made by covering a metal layer such as aluminum foil with a resin is used as the material for the sealed container, and the edges of two sheets of the laminate film are heat-sealed to form the sealed container.

[0010] The insulating film of a lead wire for a nonaqueous electrolyte battery is required to maintain adhesion between the lead conductor and the sealed container without causing a short circuit between the metal layer of the sealed container and the lead conductor. In recent years, the capacity of nonaqueous electrolyte batteries has increased, and the thickness of the conductor has tended to increase accordingly. However, with the lead wire for a nonaqueous electrolyte battery described in Patent Document 1, if the conductor is thick, the adhesion between the sealed container and the insulating film may be insufficient. Insufficient adhesion requires complex equipment to improve adhesion or requires a long thermal welding time. As a result, the productivity of nonaqueous electrolyte batteries may be reduced.

[0011] The present disclosure aims to provide a lead wire for a nonaqueous electrolyte battery that has excellent adhesion to an enclosed container and is capable of improving the productivity of nonaqueous electrolyte batteries.The present disclosure aims to provide an insulating film that constitutes a part of a lead wire for a nonaqueous electrolyte battery that has excellent adhesion to an enclosed container and is capable of improving the productivity of nonaqueous electrolyte batteries.

[0012] [Advantages of the Present Disclosure] According to the present disclosure, it is possible to provide a lead wire for a nonaqueous electrolyte battery that has excellent adhesion to an enclosed container and is capable of improving the productivity of nonaqueous electrolyte batteries. According to the present disclosure, it is possible to provide an insulating film that constitutes a part of a lead wire for a nonaqueous electrolyte battery that has excellent adhesion to an enclosed container and is capable of improving the productivity of nonaqueous electrolyte batteries.

[0013] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0014] A lead wire for a nonaqueous electrolyte battery according to one embodiment of the present disclosure includes a flat conductor and an insulating film having one or more layers and covering an outer peripheral surface of the conductor, the insulating film having a surface layer containing a thermoplastic resin, and the surface layer having a modulus of elasticity at 23°C measured with a nanoindenter of 600 MPa or less.

[0015] When the surface layer of the insulating film has an elastic modulus of 600 MPa or less, the thermoplastic resin in the surface layer softens and is crushed before melting and flowing when the lead wire for a nonaqueous electrolyte battery is bonded to the sealed container by heat sealing, making it easier for the insulating film to fill the gap between the lead wire for a nonaqueous electrolyte battery and the sealed container. As a result, the lead wire for a nonaqueous electrolyte battery has excellent adhesion to the sealed container, and productivity of nonaqueous electrolyte batteries can be improved.

[0016] The insulating film may further include an inner layer that is disposed closest to the conductor and contains a thermoplastic resin. By disposing the insulating film closest to the conductor and further including an inner layer that contains a thermoplastic resin, it is possible to use a material different from that of the surface layer to share functions. Therefore, a material that is easily bonded to the conductor and can suppress delamination can be used for the inner layer.

[0017] The insulating film may have an intermediate layer between the surface layer and the inner layer, the intermediate layer containing crosslinked polyolefin, homopolypropylene, or block polypropylene. When the insulating film has an intermediate layer between the surface layer and the inner layer and the intermediate layer contains crosslinked polyolefin, homopolypropylene, or block polypropylene, the insulating film is less likely to melt at the heat-sealing temperature when the opening of the sealed container is heat-sealed (thermally fused), and short-circuiting between the metal layer of the sealed container and the conductor can be suppressed.

[0018] The surface layer may have a modulus of elasticity of 20 MPa or more and 150 MPa or less at 80° C., as measured with a nanoindenter. When the modulus of elasticity of the surface layer at 80° C., which is a temperature approximately halfway between room temperature and the melting point, is in the above range, the surface layer tends to soften as the temperature rises, and sealing can be achieved in a short time.

[0019] The thermoplastic resin contained in the surface layer may be an olefin-based thermoplastic resin, which improves adhesion to the adherend.

[0020] The olefin-based thermoplastic resin may be at least one of polypropylene, polyethylene, and derivatives thereof. This embodiment improves adhesion to the adherend.

[0021] The insulating film constitutes a part of the lead wire for a nonaqueous electrolyte battery of the present disclosure. By using the insulating film in the lead wire for a nonaqueous electrolyte battery, excellent adhesion to the sealing container of the nonaqueous electrolyte battery is achieved.

[0022] A nonaqueous electrolyte battery according to another aspect of the present disclosure includes the lead wire for a nonaqueous electrolyte battery described above.

[0023] The nonaqueous electrolyte battery includes the lead wire for a nonaqueous electrolyte battery described above, and therefore has excellent adhesion between the lead wire and the sealed container, thereby improving productivity.

[0024] [Details of Embodiments of the Present Disclosure] Hereinafter, a lead wire for a nonaqueous electrolyte battery, a nonaqueous electrolyte battery, and a method for manufacturing a lead wire for a nonaqueous electrolyte battery according to each embodiment of the present disclosure will be described in detail.

[0025] <Lead Wire for Non-Aqueous Electrolyte Battery> The lead wire 1 for a non-aqueous electrolyte battery in Fig. 1 includes a flat conductor 3 and an insulating film 5. The insulating film 5 has one or more layers and covers the outer peripheral surface of the conductor 3. The insulating film 5 has a surface layer 8 containing a thermoplastic resin. The conductor corresponds to the lead wire conductor. When the insulating film 5 includes one layer, the surface layer 8 is a layer that forms at least a part of the surface. When the insulating film 5 includes multiple layers, the surface layer 8 forms at least a part of the surface and is located furthest from the conductor 3.

[0026] (Conductor) The flat conductor 3 is connected to the electrodes of a nonaqueous electrolyte battery. The material of the conductor 3 is not particularly limited as long as it is a conductor that can be used to form a lead wire for a nonaqueous electrolyte battery, and examples thereof 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 material forming the conductor 3 connected to the positive electrode of the nonaqueous electrolyte battery may be one that does not dissolve during discharge, and specifically may be aluminum, titanium, an aluminum alloy, or a titanium alloy. On the other hand, the material forming the conductor 3 connected to the negative electrode may be nickel, copper, a nickel alloy, a copper alloy, nickel-plated copper, or gold-plated copper.

[0027] The lower limit of the average thickness of the conductor 3 may be 0.10 mm. When the average thickness of the conductor 3 is equal to or greater than the lower limit, a sufficient amount of current can flow for practical use as a battery. The lower limit of the average thickness of the conductor 3 may be 0.15 mm or even 0.20 mm. On the other hand, the upper limit of the average thickness of the conductor 3 is not particularly limited and may be appropriately set depending on, for example, the capacity of the nonaqueous electrolyte battery. For example, the upper limit of the average thickness may be 5 mm. When the average thickness of the conductor 3 is equal to or less than the upper limit, resistance heat generation in the lead wire portion can be suppressed even during rapid charging and discharging. The upper limit of the average thickness of the conductor 3 may be 3 mm. The "average thickness" of the conductor 3 is the average value of thickness measurements at 10 points. Hereinafter, "average thickness" has the same meaning.

[0028] (Insulating Film) The insulating film 5 constitutes a part of the lead wire 1 for a nonaqueous electrolyte battery. The insulating film 5 has one or more layers and is laminated on the outer peripheral surface of the conductor 3 so as to cover the outer peripheral surface of the conductor 3. The lower limit of the average thickness of the insulating film 5 may be 0.05 mm. If the average thickness of the insulating film 5 is less than the lower limit, a gap may be formed between the insulating film 5 covering the surface of the conductor 3 in the thickness direction and the sealed container 11. The lower limit of the average thickness of the insulating film 5 may be 0.08 mm or 0.10 mm. On the other hand, the upper limit of the average thickness of the insulating film 5 may be 0.30 mm. If the average thickness of the insulating film 5 exceeds the upper limit, the amount of moisture that permeates the insulating film 5 from the atmosphere and enters the nonaqueous electrolyte battery 10 may increase, which may accelerate deterioration of the nonaqueous electrolyte battery 10. The upper limit of the average thickness of the insulating film 5 may be 0.2 mm or 0.15 mm.

[0029] The insulating film 5 may have a single-layer structure consisting of only the surface layer 8. Alternatively, the insulating film 5 may have a two-layer structure having an additional layer inside the surface layer 8. Alternatively, the insulating film 5 may have a three-layer or more structure (e.g., a five-layer structure) having two or more additional layers inside the surface layer 8. In the present embodiment, the insulating film 5 will be described in detail below using as an example an embodiment in which the insulating film 5 has three layers, specifically, a case in which the insulating film 5 has an inner layer 6 covering the outer peripheral surface of the conductor 3, an intermediate layer 7 laminated on the surface of the inner layer 6 opposite the conductor 3 (the outer peripheral surface of the inner layer 6), and a surface layer 8 laminated on the surface of the intermediate layer 7 opposite the inner layer 6 (the outer peripheral surface of the intermediate layer 7).

[0030] (Surface Layer) The surface layer 8 is a layer that constitutes at least a portion of the surface and contains a thermoplastic resin. Alternatively, the surface layer 8 is a layer that is disposed farthest from the conductor 3 and contains a thermoplastic resin. The surface layer 8 may contain only a thermoplastic resin, or may contain a thermoplastic resin as a main component. The surface layer 8 is laminated on the surface of the intermediate layer 7 opposite the inner layer 6. The surface layer 8 may contain, as a main component, a resin that is easily melted at the heat-sealing temperature when the opening of the sealed container is heat-sealed (thermally fused), or may contain, as a main component, an olefin-based thermoplastic resin. In the present disclosure, the term "main component" refers to the component that has the largest content by mass.

[0031] Examples of the olefin-based thermoplastic resin include polypropylene, polyethylene, and derivatives thereof. The polypropylene may be a random polypropylene having a melting point of 120°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. The random polypropylene used as the olefin-based thermoplastic resin has the advantage of being able to fully exhibit adhesion to the polypropylene layer that constitutes the intermediate layer 7 and the inner layer of the enclosed container 11.

[0032] The lower limit of the content of the olefin-based thermoplastic resin in the surface layer 8 may be 70% by mass. If the content of the olefin-based thermoplastic resin is less than this lower limit, it may be difficult to obtain practically sufficient material properties. Furthermore, the lower limit of the content of the olefin-based thermoplastic resin in the surface layer 8 may be 80% by mass, 90% by mass, or 100% by mass.

[0033] More specifically, the surface layer 8 may contain a plurality of resins, and examples of these plurality of resins include combinations of homopolypropylene, block polypropylene, random 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, low-crystalline polypropylene, etc. In this case, among the plurality of resins to be combined, the content of low-crystalline, flexible resins having a crystallinity of 50% or less may be 1% by mass or more and 50% by mass or less.

[0034] The surface layer 8 may contain a thermoplastic resin other than the above-mentioned olefin-based thermoplastic resin and other known additives, such as antioxidants, flame retardants, tackifiers, lubricants, fillers, crystallization accelerators, and colorants, as long as the effects of the present disclosure are not impaired.

[0035] The lower limit of the average thickness of the surface layer 8 may be 0.02 mm. If the average thickness of the surface layer 8 is less than the above-mentioned lower limit, the gap between the lead wire 1 for a nonaqueous electrolyte battery and the sealed container may not be sufficiently filled, which may result in reduced adhesion between them. The lower limit of the average thickness of the surface layer 8 may be 0.04 mm or 0.06 mm. On the other hand, the upper limit of the average thickness of the surface layer 8 may be 0.11 mm. If the average thickness of the surface layer 8 exceeds the above-mentioned upper limit, the amount of moisture that penetrates from the atmosphere through the insulating film 5 and enters the nonaqueous electrolyte battery 10 may increase, which may accelerate battery degradation. The upper limit of the average thickness of the surface layer 8 may be 0.09 mm or 0.07 mm. The average thickness is measured by solidifying the surface layer 8 with an epoxy resin, polishing the cross section of the solidified surface layer 8, and observing the cross section of the surface layer 8 with a digital microscope to measure the thickness.

[0036] The upper limit of the elastic modulus of the surface layer 8 at 23°C measured with a nanoindenter is 600 MPa. If the elastic modulus of the surface layer 8 at 23°C exceeds this upper limit, when the lead wire 1 for a nonaqueous electrolyte battery and the sealed container are bonded by heat sealing, the thermoplastic resin in the surface layer 8 is unlikely to soften before melting and flowing, which may make it difficult to fill the gap between the lead wire 1 for a nonaqueous electrolyte battery and the sealed container with an insulating film. Furthermore, the upper limit of the elastic modulus of the surface layer 8 at 23°C may be 400 MPa or 200 MPa. On the other hand, the lower limit of the elastic modulus of the surface layer 8 at 23°C may be 50 MPa. If the elastic modulus of the surface layer 8 is less than the above lower limit, the material strength of the insulating film 5 is significantly reduced when the lead wire 1 for a nonaqueous electrolyte battery and the sealed container are bonded by heat sealing, which may cause scratches when rubbed during handling and reduce sealing performance. The lower limit of the elastic modulus of the surface layer 8 may be 70 MPa or 100 MPa.

[0037] The upper limit of the elastic modulus of the surface layer 8 at 80°C measured with a nanoindenter may be 150 MPa. It may further be 140 MPa or 130 MPa. On the other hand, the lower limit of the elastic modulus of the surface layer 8 at 80°C may be 20 MPa. It may further be 25 MPa or 30 MPa. When the elastic modulus of the surface layer 8 at 80°C, which is a temperature approximately halfway between room temperature and the melting point, is within the above range, the surface layer 8 tends to soften as the temperature rises, and sealing can be achieved in a short time.

[0038] The elastic modulus of an insulating film is measured using a nanoindenter (nanoindentation method) according to the following procedure. When measuring the elastic modulus at 23°C, a TriboIndenter TI980 manufactured by HYSITRON can be used as the nanoindenter. When measuring the elastic modulus at 80°C, a Bruker "xSol Hesting" resistance heater heating system can be used as the nanoindenter. The nanoindenter uses a regular triangular pyramid indenter (Berkovich indenter) with a diamond tip. The insulating film of the measurement sample is measured while covered by a conductor. The insulating film covering a region within 4 mm from both ends of the conductor in the width direction is cut in the thickness direction of the conductor. The cross section of the insulating film is then exposed by Ar ion milling. Next, using a nanoindenter, the indenter is pressed perpendicularly against the center of the thickness direction of the cross section of the insulating film under the following measurement conditions, and the load-displacement curve is measured to calculate the elastic modulus. The indentation load is adjusted appropriately so that the size of the indentation is about 10 μm to 20 μm. (Measurement conditions) Measurement temperature: 23° C. and 80° C. Measurement humidity: 40% Indentation load: 0.5 mN to 5.0 mN Indentation depth reaching time: 5 seconds Load holding time: 0 seconds Indentation depth unloading time: 5 seconds

[0039] The elastic modulus of the surface layer 8 can be adjusted, for example, by mixing two or more resins with different elastic moduli. Specifically, the target elastic modulus can be achieved by adding a resin with a low elastic modulus of 5 MPa to 100 MPa, such as low-crystalline polypropylene, to a resin with a high elastic modulus of about 1000 MPa, such as random polypropylene, in an appropriate mass ratio.

[0040] The lower limit of the MFR of the surface layer 8 may be 3 g / 10 min. If the MFR of the surface layer 8 is less than the above lower limit, the fluidity of the surface layer 8 after melting and flowing by heating when bonding the insulating film 5 to the sealed container 11 may be poor, making it difficult for the insulating film 5 to fill the gap between the lead wire 1 for a nonaqueous electrolyte battery and the sealed container 11. The lower limit of the MFR of the surface layer 8 may be 5 g / 10 min or 6 g / 10 min. On the other hand, the upper limit of the MFR of the surface layer 8 may be 15 g / 10 min. If the MFR of the surface layer 8 exceeds the above upper limit, the surface layer 8 of the insulating film 5 may flow out when bonding the insulating film 5 to the sealed container 11, potentially reducing the adhesion between the insulating film 5 and the sealed container 11. The upper limit of the MFR of the surface layer 8 may be 10 g / 10 min or 9 g / 10 min.

[0041] (Inner Layer) The insulating film 5 may have an inner layer 6 disposed closest to the conductor 3 and containing a thermoplastic resin. The inner layer 6 may contain only a thermoplastic resin, or may contain a thermoplastic resin as a main component. The insulating film 5 having the inner layer 6 can suppress corrosion of the conductor 3 and peeling of the insulating film 5. The inner layer 6 covers the outer peripheral surface of the conductor 3. The thermoplastic resin used for the inner layer 6 may be a resin that is difficult to melt at the heat-sealing temperature when the opening of the sealed container 11 is heat-sealed (thermally fused), and may be mainly composed of an olefin-based thermoplastic resin. Here, in the present disclosure, the term "main component" refers to the component with the largest content in terms of mass, and for example, refers to a component whose content in the inner layer 6 is 50 mass% or more.

[0042] Examples of olefin-based thermoplastic resins include polypropylene, polyethylene, and derivatives thereof. Derivatives include acid-modified products. The olefin-based thermoplastic resin may be polypropylene or acid-modified polypropylene. The olefin-based thermoplastic resin is advantageously polypropylene or acid-modified polypropylene, which provides adhesion to the conductor 3 and sufficient adhesion to the intermediate layer 7. Furthermore, the polypropylene or acid-modified polypropylene may be 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. Examples of such random polypropylene include copolymers of propylene and ethylene or α-olefins having 4 to 20 carbon atoms. The MFR is an index representing the fluidity of the resin. The MFR is measured using a melt indexer at a temperature of 230°C and a load of 2.16 kg, in accordance with JIS-K7210-1:2014 (Method A: Mass Measurement Method).

[0043] The lower limit of the content of the olefin-based thermoplastic resin in the inner layer 6 may be 70% by mass. If the content of the olefin-based thermoplastic resin is less than this lower limit, it may be difficult to obtain practically sufficient material properties. Furthermore, the lower limit of the content of the olefin-based thermoplastic resin in the inner layer 6 may be 80% by mass, 90% by mass, or 100% by mass.

[0044] The inner layer 6 may contain a thermoplastic resin other than the above-mentioned olefin-based thermoplastic resin and other known additives, such as antioxidants, flame retardants, tackifiers, lubricants, fillers, crystallization accelerators, and colorants, as long as the effects of the present disclosure are not impaired.

[0045] The lower limit of the average thickness of the inner layer 6 may be 0.02 mm. If the average thickness of the inner layer 6 is less than this lower limit, sufficient adhesion to the conductor may be insufficient. The lower limit of the average thickness of the inner layer 6 may be 0.03 mm or 0.04 mm. On the other hand, the upper limit of the average thickness of the inner layer 6 may be 0.15 mm. If the average thickness of the inner layer 6 exceeds this upper limit, the amount of moisture that permeates the insulating film 5 from the atmosphere and enters the nonaqueous electrolyte battery 10 may increase, which may accelerate battery degradation. The upper limit of the average thickness of the inner layer 6 may be 0.12 mm or 0.1 mm.

[0046] (Intermediate Layer) The insulating film may have an intermediate layer between the surface layer and the inner layer. The intermediate layer 7 is laminated on the surface of the inner layer 6 opposite the conductor 3. The intermediate layer 7 may contain the above-mentioned olefin-based thermoplastic resin. By containing an olefin-based thermoplastic resin, the intermediate layer can exhibit sufficient adhesion to the inner layer 6 and the surface layer 8 and be less likely to melt at heat-sealing temperatures. Among olefin-based thermoplastic resins, the intermediate layer may be any of cross-linked polyolefin, homopolypropylene, and block polypropylene having a melting point of 150°C or higher and 170°C or lower and an MFR of 3 g / 10 min or higher and 15 g / 10 min or lower. By containing cross-linked polyolefin, homopolypropylene, or block polypropylene, the intermediate layer can further suppress melting when the opening of the sealed container is heat-sealed, thereby suppressing short-circuiting between the metal layer of the sealed container and the conductor.

[0047] The lower limit of the content of the olefin-based thermoplastic resin in the mid layer 7 may be 70% by mass. If the content of the olefin-based thermoplastic resin is less than this lower limit, it may be difficult to obtain practically sufficient material properties. Furthermore, the lower limit of the content of the olefin-based thermoplastic resin in the mid layer 7 may be 80% by mass, 90% by mass, or 100% by mass.

[0048] The intermediate layer 7 may contain a thermoplastic resin other than the above-described olefin-based thermoplastic resin and other known additives, such as antioxidants, flame retardants, tackifiers, lubricants, fillers, crystallization accelerators, and colorants, as long as the effects of the present disclosure are not impaired.

[0049] The lower limit of the average thickness of the intermediate layer 7 may be 0.02 mm. If the average thickness of the intermediate layer 7 is less than this lower limit, the insulating film 5 may flow excessively due to heat when bonding the insulating film 5 to the sealed container 11, which may result in a short circuit between the conductor 3 and the metal layer of the sealed container 11. The lower limit of the average thickness of the intermediate layer 7 may be 0.03 mm or even 0.04 mm. On the other hand, the upper limit of the average thickness of the intermediate layer 7 may be 0.15 mm. If the average thickness of the intermediate layer 7 exceeds this upper limit, the amount of moisture that permeates the insulating film 5 from the atmosphere and enters the nonaqueous electrolyte battery 10 may increase, increasing the amount of moisture that penetrates into the battery, which may accelerate battery degradation. The upper limit of the average thickness of the intermediate layer 7 may be 0.12 mm or even 0.10 mm.

[0050] The insulating film 5 only needs to have the surface layer 8, and may have layers other than the above-mentioned layers.

[0051] [Method for Producing Insulating Film] The method for producing an insulating film according to the present disclosure is not particularly limited. For example, a resin composition for forming the inner layer, intermediate layer, and surface layer, each containing the resin components and additives, is mixed using a known mixing device such as an open roll, a pressure kneader, a single-screw mixer, or a twin-screw mixer. Next, when producing a single-layer film, the film-like inner layer, intermediate layer, and surface layer can be produced by extrusion molding such as T-die molding or inflation molding. The inner layer, intermediate layer, and surface layer are then superimposed and thermally laminated with a heated roll to form the film. Alternatively, a co-extrusion inflation method or a T-die method can be used to simultaneously form multiple layers. Furthermore, an extrusion lamination method can be used in which a molten resin is laminated on a single-layer film.

[0052] By forming a portion of the lead wire for a nonaqueous electrolyte battery using the insulating film, the lead wire has excellent adhesion to the sealed container of the nonaqueous electrolyte battery. The "surface layer" and "inner layer" of the insulating film are described based on the positional relationship of the insulating film with respect to the conductor, with the "surface layer" referring to the layer that constitutes at least a portion of the surface or the layer farthest from the conductor, and the "inner layer" referring to the layer closest to the conductor. Therefore, in an insulating film that does not cover the outer peripheral surface of the conductor, the surface layer can be referred to as the "first layer" and the inner layer as the "second layer," without taking into account the positional relationship between the two.

[0053] [Method for Manufacturing Lead Wire for Non-Aqueous Electrolyte Battery] The method for manufacturing the lead wire 1 for a non-aqueous electrolyte battery is not particularly limited, and the lead wire 1 for a non-aqueous electrolyte battery can be manufactured by a known method.

[0054] <Advantages> The lead wire 1 for a nonaqueous electrolyte battery has excellent adhesiveness to the sealed container, and can improve the productivity of nonaqueous electrolyte batteries.

[0055] <Non-aqueous electrolyte battery> The non-aqueous electrolyte battery 10 includes the above-described non-aqueous electrolyte battery lead wire 1. Examples of non-aqueous electrolyte batteries include secondary batteries such as lithium ion batteries.

[0056] The nonaqueous electrolyte battery (secondary battery) 10 shown in FIGS. 2 and 3 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, nonaqueous electrolyte battery lead wires 1. The nonaqueous electrolyte battery lead wire 1 is the nonaqueous electrolyte battery lead wire described above. Hereinafter, the nonaqueous electrolyte battery lead wire 1 will be described as including the insulating film 5 described above, i.e., an insulating film 5 having a three-layer structure including an inner layer 6, an intermediate layer 7, and a surface layer 8. However, the nonaqueous electrolyte battery lead wire 1 may also include an insulating film having a single-layer structure including only the surface layer 8, or an insulating film having a multilayer structure including one or more layers inside the surface layer 8. The nonaqueous electrolyte battery 10 includes a substantially square enclosed container 11 and two nonaqueous electrolyte battery lead wires 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 the insulating film 5.

[0057] Positive and negative electrodes (not shown) are stacked with a separator interposed therebetween to form a laminated electrode group. This laminated electrode group and a nonaqueous electrolyte are housed in a sealed container 11 in a sealed state. In this sealed container 11, the laminated electrode group is immersed in an electrolytic solution. The sealed container 11 is formed from a laminated film, as described below. The sealed state is achieved by heat-sealing two laminated films or a single folded laminated film at a seal portion 13 around the periphery. One of the nonaqueous electrolyte battery lead wires 1 is arranged so that one end 4a of its conductor 3 is exposed from the sealed container 11 and the other end 4b is connected to the positive electrode in the sealed container 11. The other nonaqueous electrolyte battery lead wire 1 is arranged so that one end 4a of its conductor 3 is exposed from the sealed container 11 and the other end 4b is connected to the negative electrode in the sealed container 11. The intermediate portions of these nonaqueous electrolyte battery lead wires 1 are sandwiched between a laminated film that is an encapsulation container 11 via an insulating film 5, and at this portion, the encapsulation container 11 and the multiple nonaqueous electrolyte battery lead wires 1 are heat-sealed.

[0058] The positive electrode and the negative electrode are typically laminates in which an active material layer containing an active material is laminated on the surface of a current collector such as a metal foil. The positive electrode and the negative electrode are usually in the form of a plate, but may have a shape other than a plate.

[0059] The separator is typically an insulating, porous sheet that allows the electrolyte to flow between the positive and negative electrodes.

[0060] When the non-aqueous electrolyte is a non-aqueous electrolytic solution, a non-aqueous solvent in which an electrolyte salt is dissolved can be used as the non-aqueous electrolytic solution.

[0061] (Enclosed Container) The enclosed container 11 includes, for example, a metal substrate, a resin layer laminated on the inner surface of the substrate, and an outer layer laminated on the outer surface of the substrate. That is, for example, a laminated film in which the resin layer, substrate, and outer layer are laminated in this order can be used as the enclosed container 11. As described above, the enclosed container 11 is a container that accommodates the positive electrode, negative electrode, separator, and non-aqueous electrolyte in a sealed state.

[0062] The substrate has functions such as improving the strength of the sealed container 11 and preventing the intrusion of water vapor, oxygen, light, etc. into the battery. The substrate is mainly composed of a metal. Examples of this metal include aluminum, copper, stainless steel, and titanium, and aluminum is particularly suitable. The substrate is substantially made of a metal, but may contain additives other than metals. The substrate is in the form of a film, and may be made of a metal foil or an aluminum alloy foil. The average thickness of the substrate may be approximately 10 μm to 50 μm.

[0063] The resin layer corresponds to the innermost layer and is directly laminated on the inner surface of the substrate. The resin layer is not particularly limited as long as it is heat-sealable, but examples thereof include polyolefins and acid-modified polyolefins, and polypropylene is particularly suitable. The average thickness of the resin layer may be about 10 to 500 μm.

[0064] The outer layer has functions such as protecting the outer surface of the substrate and providing insulation. The outer layer is typically made primarily of a resin as an insulating material. Examples of resins that form the outer layer include polyethylene terephthalate (PET), polyamide, polyester, polyamide, polyolefin, epoxy resin, acrylic resin, fluororesin, polyurethane, silicone resin, phenolic resin, polyetherimide, polyimide, and mixtures or copolymers thereof. The average thickness of the outer layer may be approximately 10 to 50 μm.

[0065] No resin layer (i.e., sealed container 11) is laminated on either end portion of conductor 3, i.e., one end 4a and the other end 4b. One end 4a of conductor 3 is exposed from sealed container 11. Meanwhile, an internal connection lead wire 14 is connected to the other end 4b of conductor 3 of lead wire 1 for a nonaqueous electrolyte battery on the positive electrode side via a solder portion 15, and is connected to a positive electrode (not shown) via this internal connection lead wire 14. Similarly, an internal connection lead wire 14 is connected to the other end 4b of conductor 3 of lead wire 1 for a nonaqueous electrolyte battery on the negative electrode side via a solder portion 15, and is connected to a negative electrode (not shown) via this internal connection lead wire 14.

[0066] As described above, in the nonaqueous electrolyte battery 10, one end of the lead wire 1 for a nonaqueous electrolyte battery, i.e., one end 4 a of the conductor 3, is arranged in a state where it is exposed from the sealed container 11, and is sealed by the sealed container 11. Specifically, the lead wire 1 for a nonaqueous electrolyte battery is arranged so that the resin layer of the sealed container 11 and the insulating film 5 of the lead wire 1 for a nonaqueous electrolyte battery are in direct contact with each other. Furthermore, with the lead wire 1 for a nonaqueous electrolyte battery arranged in this manner, the resin layers in the seal portion 13 of the sealed container 11 are heat-sealed to each other, and the resin layer of the sealed container 11 is heat-sealed to the insulating film 5 of the lead wire 1 for a nonaqueous electrolyte battery. This allows the nonaqueous electrolyte and the positive electrode, negative electrode, and separator, which are the stacked electrode group, to be hermetically sealed within the sealed container 11.

[0067] <Advantages> The nonaqueous electrolyte battery 10 of this embodiment includes the lead wire 1 for a nonaqueous electrolyte battery described above, and therefore has excellent adhesion between the lead wire 1 for a nonaqueous electrolyte battery and the sealed container 11, thereby improving productivity.

[0068] [Other Embodiments] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is not limited to the configurations of the above-described embodiments, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope of the claims.

[0069] [Examples] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0070] The materials used are as follows: (Conductor) ALS Aluminum plate (average thickness: 0.4 mm)

[0071] (First resin composition: material for forming inner layer) PP1: acid-modified random polypropylene, Admer QE060 (MFR 7, melting point 140°C) manufactured by Mitsui Chemicals, Inc.

[0072] (Second resin composition: material for forming intermediate layer) (1) PP21 Block polypropylene: Novatec BC3AV (MFR 10, melting point 165°C) manufactured by Japan Polypropylene Corporation (2) PP22 Homopolypropylene: Novatec MA3H (MFR 10, melting point 165°C) manufactured by Japan Polypropylene Corporation (3) PP23 Block polypropylene: Novatec BC3AV (MFR 10, melting point 165°C) manufactured by Japan Polypropylene Corporation and a crystalline propylene-based polymer: Tafmer PN2070 (MFR 7, melting point 140°C) manufactured by Mitsui Chemicals Co., Ltd. were mixed to adjust the elastic modulus. (4) PP24 Random polypropylene: Noblen S131 (MFR 1.3, melting point 130°C) manufactured by Sumitomo Chemical Co., Ltd. was added with an appropriate acrylic cross-linking coagent and cross-linked by irradiation cross-linking treatment.

[0073] (Third resin composition: material for forming surface layer) (1) PP31 Random polypropylene: Prime Polypropylene F227D (MFR 7, melting point 140°C) manufactured by Prime Polypropylene Co., Ltd. (2) PP32 Random polypropylene: Prime Polypropylene F227D (MFR 7, melting point 140°C) manufactured by Prime Polypropylene Co., Ltd. mixed with random polypropylene: Tafmer P280 (MFR 6, melting point 50°C or less) manufactured by Mitsui Chemicals Co., Ltd. to adjust the elastic modulus (3) PP33 Random polypropylene: Prime Polypropylene F227D (MFR 7, melting point 140°C) manufactured by Prime Polypropylene Co., Ltd. mixed with random polypropylene: Tafmer P280 (MFR 6, melting point 50°C or less) manufactured by Mitsui Chemicals Co., Ltd. to adjust the elastic modulus (4) PP34 Random polypropylene: Prime Polypro F227D (MFR 7, melting point 140°C) manufactured by Prime Polypro Co., Ltd., mixed with random polypropylene: Tafmer P280 (MFR 6, melting point 50°C or less) manufactured by Mitsui Chemicals, Ltd., to adjust the elastic modulus. (5) PP35 Random polypropylene: Prime Polypro F227D (MFR 7, melting point 140°C) manufactured by Prime Polypro Co., Ltd., mixed with crystalline propylene polymer: Tafmer PN2070 (MFR 7, melting point 140°C) manufactured by Mitsui Chemicals, Ltd., to adjust the elastic modulus.

[0074] (Sealed container) ALP: Aluminum packaging material manufactured by DNP (408PH(3))

[0075] [Test No. 3] Using a coat hanger-type three-type, three-layer T-die film-forming machine equipped with three single-screw extruders, the PP1 resin was loaded into the first extruder, the PP21 resin into the second extruder, and the PP33 resin into the third extruder, and co-extruded to obtain a three-layer insulating film laminated in the order PP1 / PP21 / PP33. Of the three insulating films obtained, the layer made of PP1 was the inner layer, the layer made of PP21 was the middle layer, and the layer made of PP33 was the surface layer. At this time, the average thickness of each layer was 50 μm for the inner layer (PP1), 50 μm for the middle layer (PP21), and 50 μm for the surface layer (PP33). Next, the obtained three-layer insulating film was cut to a predetermined size and placed on both sides of a conductor with the inner layer facing the conductor. Heat and pressure were applied to bond the conductor / insulating film and insulating film / insulating film together, thereby obtaining a lead wire for a nonaqueous electrolyte battery.

[0076] (Method of Producing Insulating Film) Using the mixing device of a twin-screw mixer, resin compositions for the inner layer, intermediate layer, and surface layer were produced, each having the composition shown in Table 1. Next, using a coat hanger-type three-type three-layer T-die film-forming machine equipped with three single-screw extruders, insulating film 5 was formed to have a predetermined laminated form and average thickness. Thereafter, the insulating film was cut to a predetermined size and bonded to both sides of a conductor by heating and pressure.

[0077] [Test No. 4] A lead wire for a nonaqueous electrolyte battery was obtained in the same manner as in Test No. 3, except that PP33 in the surface layer of Test No. 3 was changed to PP34.

[0078] [Test No. 5] A lead wire for a nonaqueous electrolyte battery was obtained in the same manner as in Test No. 3, except that the PP33 in the surface layer of Test No. 3 was changed to PP35.

[0079] [Test No. 6] A lead wire for a nonaqueous electrolyte battery was obtained in the same manner as in Test No. 3, except that the PP21 in the intermediate layer of Test No. 3 was changed to PP22.

[0080] [Test No. 7] A lead wire for a nonaqueous electrolyte battery was obtained in the same manner as in Test No. 3, except that the PP21 in the intermediate layer of Test No. 3 was changed to PP23.

[0081] [Test No. 8] A lead wire for a nonaqueous electrolyte battery was obtained in the same manner as in Test No. 3, except that the PP21 in the intermediate layer of Test No. 3 was changed to PP24.

[0082] [Test No. 9] A lead wire for a nonaqueous electrolyte battery was obtained in the same manner as in Test No. 3, except that the PP33 in the surface layer was changed to PP34 and the PP21 in the intermediate layer was changed to PP23.

[0083] [Test No. 1] A lead wire for a nonaqueous electrolyte battery was obtained in the same manner as in Test No. 3, except that the PP33 of the surface layer of Test No. 3 was changed to PP31.

[0084] [Test No. 2] A lead wire for a nonaqueous electrolyte battery was obtained in the same manner as in Test No. 3, except that the PP33 of the surface layer of Test No. 3 was changed to PP32.

[0085] (Measurement of Elastic Modulus) The elastic modulus of the surface layer of each of the obtained lead wires for nonaqueous electrolyte batteries of Test No. 1 to Test No. 9 was measured using a nanoindenter by the method described above. The indentation load was measured under the condition of an indentation load of 5.0 mN for each of the lead wires for nonaqueous electrolyte batteries of Test No. 1 to Test No. 9. The results are shown in Table 1.

[0086] (Measurement of Sealing Time) The material for forming the sealed container was 408PH (3) manufactured by DNP, a sheet in which an inner layer of a polypropylene film and an outer layer of a polyamide film were laminated on aluminum foil (A1085, thickness 50 μm). The obtained lead wires for nonaqueous electrolyte batteries of Test No. 1 to Test No. 9 were overlapped with the inner layer of the sheet, and heat-sealed under conditions of a mold temperature of 190°C and a surface pressure of 1.5 MPa, and the time until the seal was complete was measured. The results are shown in Table 1. A time until the seal was completed was evaluated as A (good), and a time until the seal was completed was evaluated as B (poor). The results are shown in Table 1.

[0087]

[0088] As shown in Table 1, Test No. 3 to Test No. 9, in which the elastic modulus of the surface layer at 23°C measured with a nanoindenter was 600 MPa or less, were shown to be able to seal with a sealed container without gaps in a shorter time than Test No. 1 and Test No. 2, in which the elastic modulus exceeded 600 MPa.

[0089] The lead wire for a nonaqueous electrolyte battery and the nonaqueous electrolyte battery according to the present disclosure have excellent adhesion to an enclosed container and can improve the productivity of nonaqueous electrolyte batteries, and therefore can be suitably used in energy storage elements such as secondary batteries and capacitors.

[0090] REFERENCE SIGNS LIST 1 Lead wire for non-aqueous electrolyte battery 3 Conductor 4a One end 4b Other end 5 Insulating film 6 Inner layer 7 Intermediate layer 8 Surface layer 10 Non-aqueous electrolyte battery 11 Enclosure 13 Sealed portion 14 Lead wire 15 Solder portion

Claims

1. a flat conductor; an insulating film having a plurality of layers and covering the outer surface of the conductor; Equipped with the insulating film has a surface layer containing a thermoplastic resin and an inner layer disposed closest to the conductor; The lead wire for a non-aqueous electrolyte battery has an elastic modulus of the surface layer at 23° C. of 600 MPa or less as measured with a nanoindenter.

2. 2. The lead wire for a non-aqueous electrolyte battery according to claim 1, wherein the inner layer contains a thermoplastic resin.

3. the insulating film has an intermediate layer between the surface layer and the inner layer, 3. The lead wire for a non-aqueous electrolyte battery according to claim 2, wherein the intermediate layer contains a crosslinked polyolefin, homopolypropylene, or block polypropylene.

4. 4. The lead wire for a nonaqueous electrolyte battery according to claim 1, wherein the surface layer has a modulus of elasticity at 80° C. measured with a nanoindenter of 20 MPa or more and 150 MPa or less.

5. 4. The lead wire for a non-aqueous electrolyte battery according to claim 1, wherein the thermoplastic resin contained in the surface layer is an olefin-based thermoplastic resin.

6. 6. The lead wire for a non-aqueous electrolyte battery according to claim 5, wherein the olefin thermoplastic resin is at least one of polypropylene, polyethylene, and derivatives thereof.

7. An insulating film constituting a part of a lead wire for a nonaqueous electrolyte battery, the insulating film has a first layer constituting a surface and a second layer indirectly or directly stacked on the first layer; the first layer comprises a thermoplastic resin; An insulating film in which the first layer has an elastic modulus of 600 MPa or less at 23° C. as measured with a nanoindenter.

8. The insulating film according to claim 7 , wherein the second layer comprises a thermoplastic resin.

9. the insulating film has an intermediate layer between the first layer and the second layer, The insulating film of claim 8 , wherein the intermediate layer comprises a cross-linked polyolefin, a homopolypropylene, or a block polypropylene.

10. 10. The insulating film according to claim 7, wherein the first layer has a modulus of elasticity at 80° C. measured with a nanoindenter of 20 MPa or more and 150 MPa or less.

11. A nonaqueous electrolyte battery comprising the lead wire for a nonaqueous electrolyte battery according to any one of claims 1 to 3.