Insulating resin film for leads, leads with insulating resin film, method for manufacturing insulating resin film for leads

Abstract

This invention provides an insulating resin film for leads that is less likely to be crushed when heat-pressed onto the outer casing. [Solution] A first layer having a first surface and a second surface located opposite the first surface, The first layer comprises a second layer laminated on the second surface of the first layer, The second layer is an insulating resin film for leads, comprising a polyolefin resin, wherein the residual heat deformation rate when heated at 200°C is 80% or more and less than 95%.

Description

Technical Field

[0001] The present disclosure relates to an insulating resin film for leads, a lead with an insulating resin film, and a method for manufacturing an insulating resin film for leads.

Background Art

[0002] Patent Document 1 discloses a power storage device including at least a power storage device element having a positive electrode, a negative electrode, and an electrolyte, an exterior material for a power storage device that seals the power storage device element, and metal terminals that are electrically connected to each of the positive electrode and the negative electrode and protrude outside the exterior material for the power storage device, wherein an adhesive film for a metal terminal is interposed between the metal terminal and the exterior material for the power storage device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A laminated battery in which a laminate including a positive electrode, a separator, and a negative electrode is sealed together with an electrolyte in an exterior body has been conventionally used. In the laminated battery, in order to connect the positive electrode and the negative electrode to an external device, leads with insulating resin films are arranged so as to cross the sealing portion of the exterior body.

[0005] The lead with an insulating resin film has a plate-shaped conductor and insulating resin films for leads disposed on the upper and lower surfaces of the conductor, respectively. The insulating resin film for leads has a function of adhering and sealing between the conductor and the exterior body by thermocompression bonding to the exterior body.

[0006] However, conventional insulating resin films for leads sometimes collapsed when heat or pressure was applied during the process of heat-pressing the insulating resin film-coated leads onto the outer casing after they had been heat-pressed onto the conductor. When the insulating resin film for leads collapsed, the conductor of the insulating resin film-coated lead and the outer casing came into close proximity, which could cause a short circuit between the metal layer of the outer casing and the conductor of the insulating resin film-coated lead. For this reason, there was a need for insulating resin films for leads that were less likely to collapse when heat-pressed onto the outer casing.

[0007] The purpose of this disclosure is to provide an insulating resin film for leads that is less likely to be crushed when heat-pressed onto an outer casing. [Means for solving the problem]

[0008] The insulating resin film for leads of the present disclosure comprises a first layer having a first surface and a second surface located opposite the first surface, and a second layer laminated on the second surface of the first layer, wherein the second layer contains a polyolefin resin and has a heat deformation retention rate of 80% or more and less than 95% when heated at 200°C. [Effects of the Invention]

[0009] According to this disclosure, it is possible to provide an insulating resin film for leads that is less likely to be crushed when heat-pressed onto an outer casing. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is an explanatory diagram of a battery to which an insulating resin film-coated lead is applied according to one aspect of the present disclosure. [Figure 2] Figure 2 is a top view of a lead with an insulating resin film according to one embodiment of the present disclosure. [Figure 3] Figure 3 is a schematic cross-sectional view along line AA in Figure 1. [Figure 4A] Figure 4A is a schematic cross-sectional view of an insulating resin film for a lead according to one aspect of the present disclosure. [Figure 4B]Figure 4B is a schematic cross-sectional view of an insulating resin film for a lead according to another aspect of the present disclosure. [Figure 5] Figure 5 is a table showing the evaluation results of the experimental examples. [Modes for carrying out the invention]

[0011] The implementation methods are described below.

[0012] [Description of Embodiments in this Disclosure] The embodiments of this disclosure are first listed and described. In the following description, the same or corresponding elements are denoted by the same reference numerals, and the same description of them is not repeated.

[0013] (1) An insulating resin film for a lead according to one aspect of the present disclosure comprises a first layer having a first surface and a second surface located opposite to the first surface, and a second layer laminated on the second surface of the first layer, wherein the second layer contains a polyolefin resin and has a heat deformation retention rate of 80% or more and less than 95% when heated at 200°C.

[0014] In this specification, the insulating resin film for leads may be referred to as "insulating resin film," and leads with insulating resin film attached may be referred to as "leads." In addition, the heat deformation retention rate when heated to 200°C may be simply referred to as "heat deformation retention rate."

[0015] With respect to the second layer, by setting the residual heat deformation rate when heated at 200°C to 80% or more, the entire insulating resin film can be made less susceptible to crushing when heat or pressure is applied. Therefore, when a lead having an insulating resin film according to one aspect of this disclosure is heat-pressed onto an outer casing, the insulating resin film is less likely to be crushed even when heat or pressure is applied, and a short circuit between the outer casing and the conductor of the lead can be prevented.

[0016] By setting the heating deformation residual rate of the second layer to less than 95%, when thermocompression bonding the insulating resin film to the conductor, the insulating resin film can be deformed appropriately, and the adhesion between the insulating resin film and the conductor can be enhanced. The heating deformation residual rate of the second layer can be selected according to the degree of crosslinking of the second layer, etc. By setting the heating deformation residual rate of the second layer to less than 95%, the cost of manufacturing the second layer can be reduced.

[0017] Since the polyolefin resin has excellent crosslinkability, by including the polyolefin resin in the second layer, the heating deformation residual rate of the second layer can be easily controlled. In addition, the glass transition point and melting point of the polyolefin resin are sufficiently higher than the operating temperatures of various batteries such as lithium-ion secondary batteries where the application of leads having the insulating resin film according to one aspect of the present disclosure is assumed. Therefore, by including the polyolefin resin in the second layer, in a battery to which a lead having the insulating resin film according to one aspect of the present disclosure is applied, the adhesion between the exterior body and the lead can be enhanced. Also, a layer containing a polyolefin resin is often disposed on the surface of the exterior body that contacts the lead. Therefore, by including the polyolefin resin in the second layer, the adhesion between the lead having the insulating resin film according to one aspect of the present disclosure and the exterior body is also enhanced.

[0018] (2) In the above (1), the insulating resin film for the lead may have a heating deformation residual rate of 20% or more when heated at 200°C.

[0019] Regarding the insulating resin film according to one aspect of the present disclosure, by setting the heating deformation residual rate when heated at 200°C to 20% or more, the insulating resin film according to one aspect of the present disclosure can be made particularly difficult to be crushed when heat and pressure are applied. Therefore, when thermocompression bonding a lead having the insulating resin film according to one aspect of the present disclosure to an exterior body, etc., even when heat and pressure are applied, the insulating resin film is difficult to be crushed, and short circuit between the exterior body and the conductor of the lead can be prevented.

[0020] (3) The lead with an insulating resin film according to one aspect of the present disclosure includes a plate-like conductor having a rectangular shape on its upper and lower surfaces, a first insulating resin film disposed on the upper surface of the conductor, and a second insulating resin film disposed on the lower surface of the conductor. The first insulating resin film and the second insulating resin film are insulating resin films for leads described in (1) or (2), and are laminated in the order of the conductor, the first layer, and the second layer.

[0021] In the lead with an insulating resin film according to one aspect of the present disclosure, an insulating resin film according to one aspect of the present disclosure is thermocompression-bonded to the conductor.

[0022] According to the insulating resin film according to one aspect of the present disclosure, it can be made difficult to be crushed when thermocompression-bonded to an exterior body or the like. Therefore, when thermocompression-bonding the lead according to one aspect of the present disclosure to an exterior body or the like, even when heat or pressure is applied, the insulating resin film is difficult to be crushed, and it is possible to prevent a short circuit between the exterior body and the conductor included in the lead.

[0023] (4) The method for manufacturing an insulating resin film for a lead according to one aspect of the present disclosure includes a layer forming step of forming a first layer and a second layer, a laminating step of laminating and bonding the second layer to the first layer obtained in the layer forming step, and an electron beam irradiation step of irradiating the second layer with an electron beam of 20 kGy or more and 100 kGy or less to crosslink. The second layer contains a polyolefin resin.

[0024] According to the method for manufacturing an insulating resin film for a lead according to one aspect of the present disclosure, an insulating resin film that is difficult to be crushed even when heat or pressure is applied can be manufactured. Therefore, when manufacturing a battery using the insulating resin film manufactured by the method for manufacturing an insulating resin film for a lead according to one aspect of the present disclosure, even when heat or pressure is applied when thermocompression-bonding a lead having the insulating resin film to an exterior body or the like, the insulating resin film is difficult to be crushed. And it is also possible to prevent a short circuit between the exterior body and the conductor included in the lead.

[0025] [Details of Embodiments of the Present Disclosure] Specific examples of an insulating resin film for leads, a lead with an insulating resin film, and a method for manufacturing an insulating resin film for leads according to one embodiment of this disclosure (hereinafter referred to as "this embodiment") will be described below with reference to the drawings. However, the present invention is not limited to these examples and is intended to be shown in the claims, with all modifications within the meaning and scope of equivalence to the claims included.

[0026] In this specification, the names of components may be described with prefixes such as "1st," "2nd," etc., such as "1st layer," "2nd layer," "1st insulating resin film," and "2nd insulating resin film." These prefixes are merely used to identify each component and prevent confusion during explanation, and do not indicate arrangement, priority, or anything else. Therefore, when there is no particular risk of confusion, or when they are shown together, they can simply be described as "layer" or "insulating resin film." [Insulating resin film for leads] Figure 1 is an explanatory diagram of a battery to which an insulating resin film-coated lead having an insulating resin film for the lead of this embodiment is applied. Figure 2 is a top view of the insulating resin film-coated lead having an insulating resin film of this embodiment. Figure 3 is a schematic cross-sectional view along line AA in Figure 1.

[0027] Figure 4A is a schematic cross-sectional view of an insulating resin film according to one aspect of the present disclosure. Figure 4B is a schematic cross-sectional view of an insulating resin film according to another aspect of the present disclosure.

[0028] First, we will describe the lead with an insulating resin film equipped with the insulating resin film of this embodiment, and the battery using the lead. (1) About batteries As shown in Figure 1, the battery 10 may have an outer casing 11, an electrode stack 12 in which a positive electrode, a separator, and a negative electrode are stacked and impregnated with an electrolyte, and leads 13 connected to the electrode stack 12. (Exterior) The outer casing 11 is a container that houses and seals the electrode stack 12 and the electrolyte. The outer casing 11 may have at least one resin layer on the surface facing the electrode stack 12 so that it can be heat-sealed.

[0029] The exterior body 11 can have a structure in which a first resin layer 111, a metal layer 112, and a second resin layer 113 are laminated, as shown in Figure 3, for example.

[0030] As shown by the dashed line in Figure 1, a sealing portion 110 is formed around the periphery of the outer casing 11, and the electrode stack 12 and electrolyte are sealed by the sealing portion 110. The area enclosed by the sealing portion 110 is the area sealed by the outer casing 11. (2) Regarding leads with insulating resin film As shown in Figures 1, 2, and 3, the insulating resin film-equipped lead 13 of this embodiment may have a plate-shaped conductor 14 having a rectangular upper surface 141 and a lower surface 142, and an insulating resin film 15 for the lead. The insulating resin film 15 includes a first insulating resin film 151 disposed on the upper surface 141 of the conductor 14, and a second insulating resin film 152 disposed on the lower surface 142 of the conductor 14.

[0031] The conductor 14 and insulating resin film 15, which are components of the lead 13, will now be described. (2-1) Conductor The conductor 14 is a component for connecting the electrode stack 12, which is placed inside the outer casing 11, with the equipment placed outside the outer casing 11. The conductor 14 can be plate-shaped, and its upper surface 141 and lower surface 142 (see Figure 3) may have a rectangular shape. As shown in Figure 2, the upper surface 141 of the conductor 14 has two opposing sides, sides 21 and 22, and sides 23 and 24 that intersect sides 21 and 22. However, the rectangular shape does not mean a geometrically strict shape, and the conductor 14 may have rounded corners.

[0032] In the following explanation, the conductor 14 is viewed from above along the vertical direction of the top surface 141, and the axis along the two selected opposing sides, sides 21 and 22, is defined as the X-axis. The axis perpendicular to the X-axis is defined as the Y-axis.

[0033] The material of the conductor 14 is not particularly limited, and various materials used for lead conductors can be used, for example. Examples of materials for the conductor 14 include metallic materials such as aluminum, titanium, nickel, copper, aluminum alloys, titanium alloys, nickel alloys, and copper alloys, as well as materials made by plating these metallic materials with nickel, gold, etc. (2-2) Insulating resin film As shown in Figure 3, the insulating resin film 15 may include a first insulating resin film 151 positioned on the upper surface 141 of the conductor 14, and a second insulating resin film 152 positioned on the lower surface 142 of the conductor 14. As shown in Figures 2 and 3, on the upper surface 141 and the lower surface 142, the first insulating resin film 151 and the second insulating resin film 152 are positioned so that they do not cover the ends of the conductor 14 along the Y-axis, i.e., the ends including sides 21 and 22, but leave them exposed. Therefore, on the upper surface 141 and the lower surface 142 of the conductor 14, the first insulating resin film 151 and the second insulating resin film 152 are positioned to cover the intermediate portion of the conductor 14, which is the portion of the conductor 14 other than the ends along the Y-axis, crossing the conductor 14 along the X-axis.

[0034] The upper surface 141 and lower surface 142 of the conductor 14 refer to the surfaces that face the outer casing 11 of the battery 10 when the battery 10 is manufactured.

[0035] Of the conductor 14, the ends along the Y-axis refer to the first end region 25 including side 21 and the second end region 26 including side 22, as shown in Figure 2. The intermediate portion is the part located between the first end region 25 and the second end region 26.

[0036] The first end region 25 is the part that is exposed to the outside of the casing 11 when the lead 13 is applied to the battery, and its size can be selected to allow connection to external equipment. The second end region 26 is the part that is located inside the casing 11 when the lead 13 is applied to the battery, and is connected to the electrode stack 12, and its size can be selected to allow connection to the electrode stack 12. The first end region 25 and the second end region 26 may have the same area or different dimensions.

[0037] Therefore, the length L14 of the conductor 14 along the Y-axis may be longer than the length L15 of the insulating resin film 15. Also, the length W15 of the insulating resin film 15 may be longer than the length W14 of the conductor 14 along the X-axis.

[0038] The first insulating resin film 151 and the second insulating resin film 152 may be arranged so as shown in Figure 2, that they extend beyond both ends of the conductor along the X-axis and overlap. In the portions that extend beyond the conductor 14, the first insulating resin film 151 and the second insulating resin film 152 may be in direct contact and bonded together. (3) Regarding insulating resin film for leads The insulating resin film 15 is placed on the portion of the lead 13 that contacts the outer casing 11, and is bonded to the conductor 14 by heat compression to form the lead 13. The lead 13 can be tightly attached to the sealing portion 110 (see Figure 1) of the outer casing 11 at the insulating resin film 15 portion.

[0039] Conventional insulating resin films 15 sometimes collapsed when heat or pressure was applied, such as when the lead 13 was heat-pressed onto the outer casing 11. When the insulating resin film 15 collapsed, the outer casing 11 and the conductor 14 of the lead 13 came into close proximity, which could cause a short circuit between the metal layer 112 of the outer casing 11 and the conductor 14 of the lead 13. For this reason, there was a need for an insulating resin film 15 that was less likely to collapse when heat-pressed onto the outer casing 11.

[0040] As shown in Figures 4A and 4B, the insulating resin film 15 of this embodiment can have a structure in which multiple layers containing resin are laminated. For example, as shown in Figure 4A, the insulating resin film 15 can have a structure in which a first layer 31 and a second layer 32 are laminated. Also, as shown in Figure 4B, the insulating resin film 15 can have a third layer 33 in addition to the first layer 31 and the second layer 32. The insulating resin film 15 can also have a structure in which four or more layers are laminated.

[0041] If the insulating resin film 15 has multiple layers, each layer can be functionally separated. If the insulating resin film 15 contains two layers, for example, the first layer 31 may be an adhesive layer that adheres to the conductor 14. The second layer 32 may be a heat-resistant layer that makes the lead 13 less likely to be crushed when heat-pressed to the outer casing 11 and increases its mechanical strength. As shown in Figure 4B, if the insulating resin film 15 further has a third layer 33, the third layer 33 may be an adhesion layer that improves adhesion to the outer casing 11.

[0042] When the insulating resin film 15 has multiple layers, the second layer 32 can be made into a heat-resistant layer that makes it less likely to be crushed when the lead 13 is heat-pressed to the outer casing 11 and increases its mechanical strength. Therefore, by sufficiently increasing the heat deformation retention rate of the second layer 32, it is possible to make the insulating resin film 15 less likely to be crushed when heat-pressed to the outer casing 11, and thus the present invention was completed.

[0043] As shown in Figures 4A and 4B, the insulating resin film 15 of this embodiment may have a first layer 31 having a first surface 400 exposed to the outside and a second surface 401 located opposite the first surface 400, and a second layer 32 laminated on the second surface 401 of the first layer 31.

[0044] The first surface 400 of the first layer 31 is the surface that is thermocompressed onto the conductor 14. The second surface 401 of the first layer 31 is the interface with the second layer 32. (3-1) Characteristics and materials of each layer The following explains each layer. (3-1-1)Second layer (3-1-1-1) Heat deformation residual rate of the second layer The second layer 32 can achieve a heat deformation retention rate of 80% or more when heated at 200°C.

[0045] The residual deformation after heating can be measured using Thermal Mechanical Analysis (TMA). The residual deformation after heating can be calculated from the initial thickness and the thickness after heating of the second layer 32, which is the object being measured, using the following formula (1).

[0046] (Remaining deformation rate after heating) = [(Thickness after heating) / (Initial thickness)] × 100 ... (1) The initial thickness refers to the thickness of the second layer 32, which is the object being measured, before heating.

[0047] The post-heating thickness refers to the thickness at 200°C when the second layer 32, the object being measured, is heated from room temperature (30°C) to 250°C at a heating rate of 20°C / min while applying a pressure of 0.1 MPa.

[0048] When manufacturing a battery using the lead 13 equipped with the insulating resin film 15 of this embodiment, the lead 13 is heat-pressed onto the outer casing 11. This heating is performed to a temperature such that a portion of the resin contained in the insulating resin film 15 softens, for example, around 200°C. Therefore, the thickness after heating is the thickness obtained when heated at 200°C.

[0049] As is clear from equation (1) above, a higher residual heat deformation rate means that the change from the initial thickness when heated is sufficiently reduced, and that the material is less likely to collapse when heat or pressure is applied.

[0050] Furthermore, according to the inventors' research, by setting the heat deformation retention rate of the second layer 32, which functions as a heat-resistant layer, to 80% or more when heated at 200°C, the entire insulating resin film 15 can be made less susceptible to crushing when heat or pressure is applied. Therefore, when heat-pressing the lead 13 having the insulating resin film 15 of this embodiment to the outer casing 11, the insulating resin film 15 is less likely to be crushed even when heat or pressure is applied, thus preventing a short circuit between the outer casing 11 and the conductor 14 of the lead 13.

[0051] The upper limit of the heat deformation residual rate of the second layer 32 is not particularly limited, but may be less than 95%, for example. By setting the heat deformation residual rate of the second layer 32 to less than 95%, the insulating resin film 15 can be appropriately deformed when it is heat-pressed onto the conductor 14, thereby improving the adhesion between the insulating resin film 15 and the conductor 14. The heat deformation residual rate of the second layer 32 can be selected depending on the degree of crosslinking of the second layer 32, but by setting the heat deformation residual rate of the second layer 32 to less than 95%, the cost of manufacturing the second layer 32 can be reduced.

[0052] The residual heat deformation rate of the second layer 32 may be 80% or more but less than 95%, or 80% or more but 90% or less.

[0053] The residual heat deformation of the second layer 32 can be selected depending on the type of resin contained in the second layer 32, the additives, and the degree of crosslinking. (3-1-1-2) Materials contained in the second layer (thermoplastic resin) The second layer 32 may contain a thermoplastic resin so that it can be heat-pressed to the conductor 14 or the outer casing 11. As the thermoplastic resin, one or more types selected from, for example, polyolefin resin, polyester resin, polystyrene resin, polyvinyl chloride resin, etc., can be used. Examples of polyolefin resins include polyethylene, polypropylene, acid-modified polyethylene, acid-modified polypropylene, and other acid-modified polyolefin resins. Examples of polyester resins include polyethylene terephthalate resin. Examples of acid-modified polyolefins include maleic anhydride-modified polyolefins.

[0054] The second layer 32 may contain a polyolefin resin. Since polyolefin resins have excellent crosslinking properties, the inclusion of a polyolefin resin in the second layer 32 makes it easy to control the residual heat deformation of the second layer 32. Furthermore, the glass transition temperature and melting point of polyolefin resins are sufficiently high compared to the operating temperatures of various batteries, such as lithium-ion secondary batteries, to which the leads having the insulating resin film 15 of this embodiment are expected to be applied. For this reason, the inclusion of a polyolefin resin in the second layer 32 improves the adhesion between the casing and the leads in batteries using the leads having the insulating resin film 15 of this embodiment. In addition, since a layer containing a polyolefin resin is often arranged on the surface of the casing 11 that contacts the leads 13, the inclusion of a polyolefin resin in the second layer 32 also improves the adhesion between the leads having the insulating resin film 15 of this embodiment and the casing 11. (Crosslinking agent) The second layer 32 can also be crosslinked to increase the heat deformation retention rate. Therefore, the second layer 32 may contain a crosslinking agent.

[0055] The second layer 32 contains a crosslinking agent, which allows the second layer 32 to be crosslinked, and the degree of crosslinking of the second layer 32 can be easily controlled by adjusting the proportion of the crosslinking agent used.

[0056] The crosslinking agent contained in the second layer 32 is not particularly limited and can be selected according to the crosslinking method, etc. The crosslinking agent may include, for example, a compound containing at least two unsaturated groups in its molecule. As the crosslinking agent, one or more selected from, for example, triallyl isocyanurate (TAIC®), trimethylolpropane trimethacrylate, tris(2-acryloyloxyethyl) isocyanurate, etc., may be used. The blending ratio of the crosslinking agent in the second layer 32 is not particularly limited, but may be more than 0 parts by mass and 10 parts by mass or less, or 0.1 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the resin component.

[0057] The method for crosslinking the second layer 32 is not particularly limited, and crosslinking may be performed, for example, by irradiation with ionizing radiation such as accelerated electron beams or gamma rays. (Additives) The second layer 32 may also contain any additives other than thermoplastic resin and crosslinking agent. Examples of additives include one or more selected from flame retardants, ultraviolet absorbers, light stabilizers, heat stabilizers, lubricants, colorants, etc. (3-1-2) 1st layer, 3rd layer The first layer 31 and the third layer 33 may also contain thermoplastic resins, crosslinking agents, and additives. Since the thermoplastic resins, crosslinking agents, and additives described in the second layer 32 can be used, a further explanation is omitted.

[0058] The first layer 31, the second layer 32, and the third layer 33 may have the same composition or different compositions. When functional separation is performed between the first layer 31, the second layer 32, and the third layer 33, for example, the second layer 32 can be used as a heat-resistant layer, and therefore the degree of crosslinking can be made equal to or greater than that of the first layer 31. For this reason, the blending ratio of the crosslinking agent contained in the second layer 32 and the degree of irradiation with ionizing radiation during crosslinking can be selected. For the third layer 33 as well, for example, the composition and degree of crosslinking can be selected to improve adhesion with the outer casing 11. (3-1-3) Thickness of each layer The thicknesses T31 of the first layer 31, T32 of the second layer 32, and T33 of the third layer 33 may be the same or different. The thicknesses T31 of the first layer 31, T32 of the second layer 32, and T33 of the third layer 33 may each be, for example, between 30 μm and 200 μm.

[0059] Here, we have described the cases in which the insulating resin film 15 includes a first layer 31 and a second layer 32, and the cases in which it includes a first layer 31, a second layer 32, and a third layer 33. However, the number of layers in the insulating resin film 15 is not limited to two or three layers, and may be four or more layers. (3-2) Characteristics of insulating resin film The insulating resin film 15 of this embodiment may have a heat deformation retention rate of 20% or more when heated at 200°C.

[0060] The method for measuring and calculating the residual heat deformation rate is the same as that for the residual heat deformation rate of the second layer 32, as explained in "(3-1-1-1) Residual Heat Deformation Rate of the Second Layer," except that the object being measured is the insulating resin film 15 instead of the second layer 32. Therefore, the explanation is omitted.

[0061] In this embodiment, by setting the residual deformation rate of the insulating resin film 15 when heated at 200°C to 20% or more, the insulating resin film 15 of this embodiment can be made particularly resistant to crushing when heat or pressure is applied. Therefore, when heat-pressing the lead 13 having the insulating resin film 15 of this embodiment to the outer casing 11, the insulating resin film 15 is less likely to be crushed even when heat or pressure is applied, and a short circuit between the outer casing 11 and the conductor 14 of the lead 13 can be prevented.

[0062] The upper limit of the heat deformation residual rate of the insulating resin film 15 in this embodiment is not particularly limited, but may be, for example, 50% or less. By setting the heat deformation residual rate of the insulating resin film 15 in this embodiment to 50% or less, the insulating resin film 15 can be appropriately deformed when it is heat-pressed onto the conductor 14. This can also improve the adhesion between the insulating resin film 15 and the conductor 14. The heat deformation residual rate of the insulating resin film 15 can be selected depending on the degree of crosslinking of the second layer 32, but by setting the heat deformation residual rate of the insulating resin film 15 to 50% or less, the cost of manufacturing the second layer 32 and the insulating resin film 15 can be reduced.

[0063] The residual heat deformation rate of the insulating resin film 15 in this embodiment may be 20% or more and 50% or less, or 25% or more and 40% or less. (4) Method for manufacturing insulating resin film for leads The method for manufacturing the insulating resin film 15 in this embodiment is not particularly limited, and it can be manufactured so that the second layer 32 and the heat deformation residual rate of the insulating resin film 15 have predetermined characteristics.

[0064] For example, the method for manufacturing the insulating resin film of this embodiment may include a layer forming step, a bonding step, and an electron beam irradiation step. (4-1) Layer formation process In the layer formation process, each layer of the insulating resin film 15, namely at least the first layer 31 and the second layer 32, can be formed. If the insulating resin film to be manufactured has three or more layers, the layer formation process can also form layers other than the first layer 31 and the second layer 32, such as the third layer 33.

[0065] The specific method for forming each layer of the insulating resin film 15 is not particularly limited, but each layer can be formed by kneading the thermoplastic resin, crosslinking agent, etc. contained in each layer and then extruding it.

[0066] Since the second layer 32 can contain polyolefin resin, when forming the second layer 32 in the layer formation process, the second layer 32 can be formed by mixing polyolefin resin with a crosslinking agent or additive as needed, and then extruding the mixture. (4-2) Bonding process In the lamination process, each layer of the insulating resin film 15 obtained in the layer formation process can be laminated and bonded together by heat pressing or the like. Specifically, in the lamination process, for example, the second layer 32 can be laminated onto the first layer 31 and then bonded together.

[0067] As shown in Figure 4A, the first layer 31 may have a first surface 400 and a second surface 401 located opposite the first surface 400. In the structure shown in Figure 4A, the second layer 32 can be laminated onto the second surface 401 of the first layer 31, and the first layer 31 and the second layer 32 can be bonded together. If the insulating resin film 15 has a third layer 33 as shown in Figure 4B, the third layer 33 may be further bonded to the first layer 31 and the second layer 32 during the bonding process. (4-3) Electron beam irradiation process In the electron beam irradiation process, the second layer 32 can be crosslinked by irradiating it with an electron beam of 20 kGy to 100 kGy.

[0068] By irradiating the second layer 32 with an electron beam of 20 kGy or more during the electron beam irradiation process, the crosslinking of the resin contained in the second layer 32 can be promoted, and the residual heat deformation rate of the second layer 32 can be increased.

[0069] By irradiating the second layer 32 with an electron beam of 100 kGy or less, the cost of manufacturing the second layer 32 can be reduced and productivity can be increased. In addition, the decomposition of the resin contained in the second layer 32 can be reduced, thereby improving the strength and durability of the insulating resin film 15.

[0070] The timing of the electron beam irradiation process is not particularly limited and may be performed on the layer to be crosslinked after the completion of the layer formation process and before the bonding process.

[0071] Alternatively, after the bonding process, an electron beam irradiation process may be performed on each of the laminated layers simultaneously.

[0072] When the electron beam irradiation process is performed after the layer formation process but before the bonding process, and crosslinking is not performed on some of the layers, the electron beam irradiation process does not need to be performed on the layers that are not crosslinked. When the electron beam irradiation process is performed on multiple layers, the electron beam irradiation conditions may differ for each layer.

[0073] The electron beam irradiation process can be performed multiple times, and may be performed after the layer formation process is completed, before the bonding process, and after the bonding process. After the layer formation process and before the bonding process, the electron beam irradiation process may be performed only on the second layer 32, for example.

[0074] According to the method for manufacturing an insulating resin film for leads of this embodiment, an insulating resin film 15 that is resistant to crushing even when heat or pressure is applied can be manufactured. When a battery is manufactured using the insulating resin film 15 manufactured by the method for manufacturing an insulating resin film for leads of this embodiment, the insulating resin film 15 will be resistant to crushing even when heat or pressure is applied when heat or pressure is applied, such as when heat-pressing the leads 13 having the insulating resin film to the outer casing 11. Furthermore, it is possible to prevent short circuits between the outer casing 11 and the conductors 14 of the leads 13. [Leads with insulating resin film] The insulating resin film-covered lead 13 of this embodiment may have a plate-shaped conductor 14 having a rectangular upper surface 141 and a lower surface 142, and an insulating resin film 15. The insulating resin film 15 has a first insulating resin film 151 disposed on the upper surface 141 of the conductor 14, and a second insulating resin film 152 disposed on the lower surface 142 of the conductor 14.

[0075] The insulating resin film 15 is an insulating resin film for a lead according to one aspect of the present disclosure, and is laminated in the order of conductor 14, first layer 31, and second layer 32, for example, as shown in Figure 3. That is, the insulating resin film 15 can be arranged on the conductor 14 so that it is laminated in the order of first layer 31 and second layer 32, starting from a position close to the conductor 14.

[0076] In this embodiment, the lead with an insulating resin film has an insulating resin film 15 according to one aspect of the present disclosure heat-pressed onto the conductor 14.

[0077] According to one aspect of the present disclosure, the insulating resin film 15 is less likely to be crushed when heat-pressed onto the outer casing 11, etc. Therefore, when heat or pressure is applied when heat-pressing the lead 13 of this embodiment onto the outer casing 11, etc., the insulating resin film 15 is less likely to be crushed, and a short circuit between the outer casing 11 and the conductor 14 of the lead 13 can be prevented.

[0078] The lead with insulating resin film of this embodiment has been described in "(2) Lead with insulating resin film" for leads, so the explanation will be omitted here. [Examples]

[0079] The present invention will be described below with specific examples, but it is not limited to these examples and includes equivalents and modifications within the scope that achieve the effects of the present invention. 1. Evaluation Method The insulating resin films prepared in each of the following experimental examples were evaluated as follows. (1) Heat deformation remaining The heat deformation residual rates of the second layer 32 and the insulating resin film, which were the objects under test, were measured and calculated.

[0080] The method for measuring and calculating the residual heat deformation rate was explained in "(3-1-1-1) Residual Heat Deformation Rate of the Second Layer," so the explanation is omitted here.

[0081] A TMA (TA Instruments, model: TMA450) was used to measure the residual deformation rate due to heat. (2) Evaluation of cost and processability (2-1) Cost The evaluation was based on the cost of irradiating layer 2 32 with an electron beam.

[0082] Based on an electron beam irradiation dose of 125 kGy, a cost reduction of 20% or more was evaluated as A. Based on an electron beam irradiation dose of 125 kGy, a cost reduction of less than 20% was evaluated as B.

[0083] A rating of A means that the cost of electron beam irradiation for crosslinking has been reduced compared to a rating of B. (2-2) Processability Leads were fabricated by placing two layers of insulating resin film (9 mm wide), prepared in the following experimental example, above and below a plate-shaped conductor made of aluminum, sandwiching the aluminum plate, and then heat-pressing (sealing) the insulating resin film to the plate-shaped conductor. The heat-pressing of the insulating resin film was performed under conditions of a pressure of 1500 N, a temperature of 260 °C, and a time of 8.5 seconds. After heat-pressing, compared to before heat-pressing, the elongation of the insulating resin film was evaluated as B if it was 5% or more, and as A if it was less than 5%. An A rating means that the insulating resin film elongated less and was less likely to be crushed compared to a B rating. In the processability evaluation, the elongation, which corresponds to the amount of deformation when the insulating resin film is heat-pressed to the plate-shaped conductor, was evaluated. It was confirmed that samples with a processability rating of A were less likely to be crushed when the fabricated lead was heat-pressed to the outer casing compared to samples with a rating of B. 2. Conditions for manufacturing insulating resin film The insulating resin films prepared in each experimental example are described below.

[0084] Experimental Examples 2, 3, and 4 are examples, while Experimental Examples 1 and 5 are comparative examples. [Experimental Example 1] (1) Layer formation process (1-1) First layer formation process The first layer 31 was fabricated using the following procedure.

[0085] A first layer 31 in the form of a film with a thickness of 100 μm was fabricated by extruding polypropylene resin, which is a thermoplastic resin.

[0086] The film obtained after extrusion molding is designated as the first layer 31, and no crosslinking is performed. (1-2) Second layer formation process, electron beam irradiation process The second layer 32 was fabricated using the following procedure.

[0087] A second layer 32 in film shape was produced by kneading a thermoplastic resin, polypropylene resin, with a crosslinking agent, triallyl isocyanurate, and extruding the mixture (second layer formation step). Triallyl isocyanurate was added in a ratio of 5.0 parts by mass per 100 parts by mass of polypropylene resin.

[0088] A second layer 32 with a thickness of 50 μm was fabricated by crosslinking the film obtained after extrusion molding with an electron beam under the conditions of an acceleration voltage of 200 kV and an irradiation dose of 10 kGy (electron beam irradiation process). The residual heat deformation rate was measured for a portion of the obtained second layer 32.

[0089] The electron beam irradiation dose used to form the second layer is shown in the "Irradiation Dose (kGy)" column of Figure 5, and the measured and calculated residual heat deformation of the second layer is shown in the "Second Layer" column of the "Residual Heat Deformation (%)" column of Figure 5. (2) Bonding process The first layer 31 obtained in the layer formation process and the second layer 32 were bonded together by heat compression to form the insulating resin film of Experimental Example 1, which has the cross-sectional structure shown in Figure 4A.

[0090] The measured and calculated residual heat deformation rate of the insulating resin film is shown in the "Insulating resin film for leads" column within the "Residual Heat Deformation Rate (%)" section of Figure 5.

[0091] Furthermore, the evaluation results regarding cost and processability are shown in the "Cost" and "Processability" columns of Figure 5. [Experimental Examples 2 to 5] After the second layer formation process, in the electron beam irradiation process, the film obtained after extrusion molding was irradiated with an electron beam under the conditions shown in the "Irradiation amount (kGy)" column of Figure 5 to perform crosslinking.

[0092] Except for the points mentioned above, the insulating resin film was prepared under the same conditions as in Experimental Example 1.

[0093] The evaluation results are shown in Figure 5.

[0094] As shown in Figure 5, it was confirmed that the insulating resin films in Experimental Examples 2 to 5, which had a heat deformation retention rate of 80% or more when heated at 200°C in the second layer, also had a heat deformation retention rate of 20% or more. In other words, it was confirmed that the insulating resin films in Experimental Examples 2 to 5 are insulating resin films that are less likely to be crushed when heat-pressed onto the outer casing 11. This can also be confirmed by the fact that the processability evaluation result for the insulating resin films in Experimental Examples 2 to 5 was A.

[0095] Furthermore, for the insulating resin films in Experimental Examples 2 through 4, the cost evaluation was improved to A by reducing the amount of electron beam irradiation used to form the second layer compared to Experimental Example 5. [Explanation of Symbols]

[0096] 10 batteries 11 Exterior 110 Seal part 111 1st resin layer 112 Metal layer 113 Second resin layer 12 Electrode Stack 13. Leads (leads with insulating resin film) 14 Conductors 141 Top surface 142 Bottom surface 14A End 15 Insulating resin film 151 First insulating resin film 152 Second insulating resin film 16 test specimens 21 sides 22 sides 23 sides 24 sides 25 First end area 26 Second end area L14 Length W14 Length L15 Length W15 Length 31 1st layer 32 2nd layer 33 3rd layer 400 Page 1 401 2nd page T31 Thickness T32 Thickness T33 Thickness XX axis YY axis ZZ axis

Claims

1. A first layer having a first surface and a second surface located opposite the first surface, The first layer comprises a second layer laminated on the second surface of the first layer, The second layer is an insulating resin film for leads, comprising a polyolefin resin, wherein the residual heat deformation rate when heated at 200°C is 80% or more and less than 95%.

2. The insulating resin film for the lead according to claim 1, wherein the insulating resin film for the lead has a heat deformation retention rate of 20% or more when heated at 200°C.

3. A plate-shaped conductor having a rectangular shape on its upper and lower surfaces, The conductor comprises a first insulating resin film disposed on the upper surface and a second insulating resin film disposed on the lower surface of the conductor. The first insulating resin film and the second insulating resin film are insulating resin films for leads according to claim 1 or claim 2, and the conductor, the first layer, and the second layer are laminated in that order to form an insulating resin film lead.

4. A layer formation process for forming the first and second layers, A bonding step is performed in which the second layer is laminated onto the first layer obtained in the layer formation step, The process includes an electron beam irradiation step of irradiating the second layer with an electron beam of 20 kGy to 100 kGy to crosslink it, The method for manufacturing an insulating resin film for leads, wherein the second layer contains a polyolefin resin.

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