Lead wire and power storage device

Abstract

A lead wire according to the present invention comprises a conductor and an insulating film that covers the outer circumferential surface of the conductor between both ends in a first direction of the conductor but exposes both ends of the conductor. The conductor includes a base material that comprises copper or a copper alloy and a nickel plating layer that is provided on the base material and is disposed between the base material and the insulating film. The nickel plating layer includes a first region that contacts the insulating film. The first region includes a second region, and the developed interfacial area ratio Sdr of the second region as defined in JIS B 0681-2:2018 is at least 0.5.

Description

Lead wire and energy storage device

[0001] The present disclosure relates to a lead and an electricity storage device.

[0002] 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. To achieve this, for example, a technique has been adopted in which a positive electrode, a negative electrode, and an electrolyte are enclosed in a bag-like sealed container.

[0003] Sealed containers are required to have properties that prevent gas permeation and moisture penetration from the outside. For this reason, laminated films, in which a metal layer such as aluminum foil is coated with resin, are used as materials for sealed containers. Sealed containers are formed by heat-sealing the edges of two sheets of laminated film.

[0004] One end of the sealed container is an opening, and the positive electrode, negative electrode, electrolyte, etc. are enclosed inside this opening. Furthermore, lead conductors (hereinafter also referred to as "conductors"), one end of which is connected to the positive electrode and the negative electrode, are arranged so as to extend from the inside to the outside of the sealed container. The opening is then closed by heat sealing (thermal fusion), and the sealed container and the conductor are bonded to seal the opening.

[0005] The surface of the enclosure is made of resin, while the conductor is made of metal, so the materials are different. As a result, the interface between the enclosure and the conductor has weak adhesion. For this reason, technologies to improve the adhesive strength between the enclosure and the conductor are being investigated.

[0006] Patent Document 1 discloses a lead wire for a nonaqueous electrolyte battery, which is characterized in that a composite coating layer is formed on the metal surface of the lead wire by applying a treatment liquid containing a resin component including polyacrylic acid and a metal salt, and an insulator is provided on the outside of the composite coating layer and sealed to an enclosure. Hereinafter, the insulator will also be referred to as an insulating film.

[0007] Japanese Patent Application Publication No. 2006-128096

[0008] The lead wire of the present disclosure includes a conductor and an insulating film that covers an outer surface of the conductor between both ends of the conductor while exposing both ends of the conductor in a first direction, wherein the conductor has: a base material made of copper or a copper alloy; and a nickel plating layer that is provided on the base material and disposed between the base material and the insulating film, the nickel plating layer including a first region that contacts the insulating film, the first region including a second region, and the second region has a developed interface area ratio Sdr defined in JIS B 0681-2:2018 of 0.5 or more.

[0009] Fig. 1 is a schematic overview of an example of a lead wire according to embodiment 1. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 1. Fig. 4 is a front view schematically showing an example of an electricity storage device according to embodiment 2. Fig. 5 is a partial cross-sectional view taken along line V-V in Fig. 4.

[0010] [Problem to be Solved by the Present Disclosure] In recent years, in response to demands for shorter charging times and longer driving ranges for electric vehicles, on-board power storage devices are required to have high output characteristics that enable them to charge and discharge large currents in a short time. As the power output of power storage devices increases, the environment in which the power storage devices are used becomes hotter, and the pressure inside the power storage device increases more than before when the power storage device is in use. In order to maintain the performance of the power storage device, it is necessary for the conductor and the insulating film to be bonded with high adhesive strength even when the pressure inside the power storage device increases. Therefore, there is a demand for lead wires that have excellent adhesive strength between the conductor and the insulating film at high temperatures.

[0011] Therefore, an object of the present disclosure is to provide a lead wire that has excellent adhesive strength between a conductor and an insulating film at high temperatures, and an electricity storage device including the lead wire.

[0012] Effect of the Present Disclosure According to the present disclosure, it is possible to provide a lead wire that has excellent adhesive strength between a conductor and an insulating film at high temperatures, and an electricity storage device that includes the lead wire.

[0013] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be described. (1) A lead wire of the present disclosure includes a conductor and an insulating film covering an outer peripheral surface of the conductor between both ends of the conductor while exposing both ends of the conductor in a first direction, wherein the conductor has a base material made of copper or a copper alloy and a nickel plating layer provided on the base material and disposed between the base material and the insulating film, the nickel plating layer including a first region in contact with the insulating film, the first region including a second region, and the second region having a developed interface area ratio Sdr of 0.5 or more as defined in JIS B 0681-2:2018.

[0014] According to the present disclosure, it is possible to provide a lead wire having excellent adhesive strength between a conductor and an insulating film even at high temperatures. The developed interfacial area ratio (Sdr) defined in JIS B 0681-2:2018 is a composite parameter indicating the ratio of the difference between the area of ​​the interface of a contoured surface and the area of ​​the reference region to the area of ​​the reference region. If the contoured surface within the reference region to be evaluated has no surface irregularities, the area of ​​the interface of the contoured surface is the same as the area of ​​the reference region, and therefore Sdr = 0%. The developed interfacial area ratio (Sdr) is also defined in ISO 25178-2:2022.

[0015] (2) In the above (1), the second region may have an arithmetic mean height Sa defined in JIS B 0681-2:2018 of 0.1 μm or more, and the second region may have a maximum height Sz defined in JIS B 0681-2:2018 of 1.0 μm or more.

[0016] This improves the adhesive strength between the conductor and the insulating film.

[0017] (3) In the above (1) or (2), the percentage (S2 / S1)×100 of the area S2 of the second region to the area S1 of the first region may be 40% or more.

[0018] This improves the adhesive strength between the conductor and the insulating film.

[0019] (4) In any one of the above (1) to (3), the nickel plating layer may be made of nickel metal whose crystal structure, as determined by X-ray diffraction, is a face-centered cubic lattice structure, and the nickel plating layer may include a region in which the ratio TC(111) / TC(200), of the orientation index TC(111) of the (111) plane to the orientation index TC(200) of the (200) plane calculated by Wilson's formula, is 0.2 or more and 2.0 or less.

[0020] This improves the adhesive strength between the conductor and the insulating film.

[0021] (5) In any one of the above (1) to (4), the nickel plating layer may have an average thickness of 0.5 μm or more and 10.0 μm or less, thereby improving the corrosion resistance of the nickel plating layer.

[0022] (6) In any one of the above (1) to (5), at least a portion of the surface of the nickel plating layer facing the insulating film may contain trivalent chromium, thereby improving the corrosion resistance of the nickel plating.

[0023] (7) In any one of the above (1) to (5), at least a portion of the surface of the nickel plating layer facing the insulating film may contain zirconium, thereby improving the corrosion resistance of the nickel plating layer.

[0024] (8) In any of the above (1) to (7), the insulating film may include a first insulating layer arranged in contact with the conductor and a second insulating layer provided on the surface of the first insulating layer opposite the conductor, the first insulating layer being an acid-modified polypropylene layer, and the second insulating layer being a heat-resistant resin layer.

[0025] This allows the insulating film to have good adhesiveness and sealing properties with the conductor.

[0026] (9) The presently disclosed electricity storage device is an electricity storage device comprising: an enclosed container; and the lead wire according to any one of (1) to (8) above, which is arranged so as to extend from the inside to the outside of the enclosed container; and the insulating film is fused to the enclosed container.

[0027] According to the present disclosure, even if the pressure inside the electricity storage device increases at high temperatures, the conductor and the insulating film can be bonded with high adhesive strength, and therefore the electricity storage device can maintain its performance even at high temperatures.

[0028] [Details of the embodiments of the present disclosure] Specific examples of the lead wire and the electricity storage device of the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been changed as appropriate for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0029] In the present disclosure, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and a unit is specified only for B, the units of A and B are the same.

[0030] In the present disclosure, when one or more numerical values ​​are recited as the lower limit and the upper limit of a numerical range, a combination of any one numerical value recited as the lower limit and any one numerical value recited as the upper limit is also considered to be disclosed. For example, when a1 or more, b1 or more, and c1 or more are recited as the lower limit and a2 or less, b2 or less, and c2 or less are recited as the upper limit, a1 or more and a2 or less, a1 or more and b2 or less, a1 or more and c2 or less, b1 or more and a2 or less, b1 or more and b2 or less, b1 or more and c2 or less, c1 or more and a2 or less, c1 or more and b2 or less, and c1 or more and c2 or less are considered to be disclosed.

[0031] [Embodiment 1: Lead Wire] A lead wire according to one embodiment of the present disclosure (hereinafter also referred to as "Embodiment 1") will be described with reference to FIGS. 1 to 3. FIG. 1 is a schematic overview of an example of a lead wire according to Embodiment 1. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. In this disclosure, the direction along line II-II is also referred to as the width direction of the lead wire. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. In this disclosure, the direction along line III-III is also referred to as the longitudinal direction of the lead wire.

[0032] As shown in FIG. 1 , the lead wire 10 according to the first embodiment includes a conductor 3 and an insulating film 1 that covers the outer surface of the conductor 3 between both ends of the conductor 3 while exposing both ends of the conductor 3 in a first direction, wherein the conductor 3 has a base material 4 made of copper or a copper alloy and a nickel plating layer 5 that is provided on the base material 4 and disposed between the base material 4 and the insulating film 1, the nickel plating layer 5 including a first region that contacts the insulating film 1, the first region including a second region, and the second region has a developed interface area ratio Sdr of 0.5 or more as defined in JIS B 0681-2:2018.

[0033] In the lead wire 10 of the present disclosure, the developed interface area ratio Sdr, as defined in JIS B 0681-2:2018, of the second region of the nickel plating layer 5 that contacts the insulating film 1 is 0.5 or more. This means that at least a portion of the outer surface of the conductor 3 that contacts the insulating film 1 is roughened, which improves the adhesive strength between the conductor 3 and the insulating film 1 due to the anchor effect. Therefore, the lead wire 10 of the present disclosure has excellent adhesive strength between the conductor 3 and the insulating film 1 even at high temperatures.

[0034] The lead wire 10 of the present disclosure may be a lead wire for a non-aqueous electrolyte battery or a lead wire for an all-solid-state battery.

[0035] <Conductor> In the lead wire 10 of the first embodiment, the conductor 3 includes a substrate 4 made of copper or a copper alloy and a nickel plating layer 5 disposed between the substrate 4 and the insulating film 1. The shape and dimensions of the conductor 3 are appropriately determined depending on the application. The conductor 3 may be, for example, strip-shaped. When the conductor 3 is strip-shaped, the length of the conductor 3 in the first direction may be 10 mm to 150 mm, 20 mm to 100 mm, or 30 mm to 50 mm. The length of the conductor 3 in a direction perpendicular to the first direction may be 5 mm to 200 mm, 15 mm to 140 mm, or 25 mm to 80 mm. The thickness of the conductor 3 may be 50 μm to 1500 μm, 100 μm to 1000 μm, or 150 μm to 500 μm.

[0036] <<Substrate>> In the lead wire 10 of the first embodiment, the substrate 4 is made of copper or a copper alloy. This improves the conductivity of the conductor 3. In the present disclosure, "the substrate is made of copper" means that the substrate is made of pure copper with a copper purity of 99.9% by mass or more. Examples of copper alloys include copper alloys made of copper and at least one element selected from the group consisting of phosphorus (P), zinc (Zn), and tin (Sn). Examples of copper alloys include phosphor bronze. As long as the effects of the present disclosure are not impaired, the substrate may contain impurity elements in addition to the copper or copper alloy. Examples of impurity elements include lead (Pb) and iron (Fe). The content of elements other than copper in the substrate 4 may be, for example, 7.0% by mass or less. When two or more elements other than copper are present in the substrate 4, the content of elements other than copper refers to the total content of all elements other than copper contained in the substrate 4. The content of elements other than copper in the base material 4 is measured by high-frequency inductively coupled plasma (ICP) emission spectroscopy.

[0037] The substrate 4 may have, for example, a first main surface, a second main surface opposite the first main surface, and two side surfaces, a first side surface and a second side surface, connecting the first main surface and the second main surface. The first main surface and the second main surface may have, for example, a rectangular planar shape. In embodiment 1, the direction in which a pair of parallel sides of the first main surface of the substrate 4 extend is defined as a first direction, the direction in which another pair of parallel sides extend is defined as a second direction, and the normal direction of the first main surface is defined as a third direction. The dimension of the substrate 4 in the first direction may be larger or smaller than the dimension in the second direction. The dimension of the substrate 4 in the first direction may be the same as the dimension in the second direction. The two side surfaces of the substrate 4 may be parallel to the third direction. In embodiment 1, the first and second main surfaces of the substrate 4 are each rectangular, but the shape of the substrate 4 is not limited thereto and any conventionally known shape may be employed. For example, the corners of the first and second main surfaces of the substrate 4 may be tapered, and the first and second main surfaces do not have to be completely rectangular.

[0038] The substrate 4 may have a strip-like shape. The dimensions of the substrate 4 are appropriately set depending on the application. For example, the length of the substrate 4 in the first direction may be 10 mm to 150 mm, 20 mm to 100 mm, or 30 mm to 50 mm. The length of the substrate 4 in the second direction may be 5 mm to 200 mm, 15 mm to 140 mm, or 25 mm to 80 mm. The thickness of the substrate 4 in the third direction may be 50 μm to 1500 μm, 100 μm to 1000 μm, or 150 μm to 500 μm.

[0039] The developed interface area ratio Sdr of the first and second main surfaces of the base material 4, as defined in JIS B 0681-2:2018, may be 0 or more and 0.2 or less, 0 or more and 0.1 or less, 0 or more and 0.05 or less, or 0 or more and 0.2 or less. According to the lead wire manufacturing method of Embodiment 1 described below, even if the developed interface area ratio Sdr of the first and second main surfaces of the base material 4 is 0.2 or less, 0.1 or less, 0.05 or less, or 0, the developed interface area ratio Sdr of the second region of the nickel plating layer 5 can be 0.5 or more.

[0040] The arithmetic mean height Sa of the first and second main surfaces of the substrate 4, as defined in JIS B 0681-2:2018, may be 0 μm or more and 0.3 μm or less, 0 μm or more and 0.2 μm or less, or 0 μm or more and 0.1 μm or less. According to the lead wire manufacturing method of Embodiment 1 described below, even if the arithmetic mean height Sa of the first and second main surfaces of the substrate 4 is 0.3 μm or less, 0.2 μm or less, 0.1 μm or less, or 0 μm, the developed interface area ratio Sdr of the nickel plating layer 5 can be 0.5 or more.

[0041] The maximum height Sz of the first and second main surfaces of the substrate 4, as defined in JIS B 0681-2:2018, may be 0 μm or more and 10 μm or less, 0 μm or more and 3.2 μm or less, 0 μm or more and 2 μm or less, or 0 μm or more and 0.8 μm or less. According to the lead wire manufacturing method of Embodiment 1 described below, even if the maximum height Sz of the first and second main surfaces of the substrate 4 is 10 μm or less, 3.2 μm or less, 2 μm or less, or 0.8 μm or less, the developed interface area ratio Sdr of the nickel plating layer 5 can be 0.5 or more.

[0042] <Nickel Plating Layer> In the lead wire 10 of the first embodiment, the nickel plating layer 5 is provided on the base material 4 and is disposed between the base material 4 and the insulating film 1. The nickel plating layer 5 is provided so as to continuously cover the first main surface of the base material 4, the second main surface of the base material 4, the first side surface of the base material 4, and the second side surface of the base material 4 in at least a part of the region between the base material 4 and the insulating film 1. The nickel plating layer 5 may be provided so as to continuously cover the first main surface of the base material 4, the second main surface of the base material 4, the first side surface of the base material 4, and the second side surface of the base material 4 in the entire region between the base material 4 and the insulating film 1.

[0043] The nickel plating layer 5 may be provided in the region on the substrate 4 between the substrate 4 and the insulating film 1, as well as in a region on the substrate 4 other than between the substrate 4 and the insulating film 1. In this case, the percentage of the area of ​​the entire surface of the substrate 4 on which the nickel plating layer 5 is provided can be set appropriately depending on the application and shape of the lead wire 10. The percentage may be, for example, 50% or more, 80% or more, or 95% or more. There is no particular upper limit to the percentage, and it may be, for example, 100% or less. The percentage corresponds to the coverage of the surface of the substrate 4 by the nickel plating layer 5.

[0044] In the lead wire 10 of the first embodiment, the nickel plating layer 5 includes a first region that contacts the insulating film 1. That is, the insulating film 1 is provided on the first region, which is at least a part of the nickel plating layer 5.

[0045] In the nickel plating layer 5, the percentage of the area of ​​the first region relative to the area of ​​the entire nickel plating layer 5 is not particularly limited and can be set appropriately depending on the application and shape of the lead wire 10. The percentage may be, for example, 5% or more, 10% or more, or 20% or more. The percentage corresponds to the coverage of the nickel plating layer 5 by the insulating film 1.

[0046] The first region of the nickel plating layer 5 includes the second region. The developed interface area ratio Sdr of the second region, as defined in JIS B 0681-2:2018, is 0.5 or more, and may be 0.8 or more, 1.0 or more, 1.2 or more, 1.4 or more, 2.0 or more, or 2.4 or more. The higher the developed interface area ratio Sdr of the second region, the more improved the anchoring effect, so there is no particular upper limit. From a manufacturing standpoint, the upper limit of the developed interface area ratio Sdr of the second region can be, for example, 3.0 or less. The developed interface area ratio Sdr of the second region may be 0.5 or more and 3.0 or less, 0.8 or more and 3.0 or less, 1.2 or more and 3.0 or less, or 2.0 or more and 3.0 or less.

[0047] In the nickel plating layer 5, the percentage (S2 / S1) x 100 of the area S2 of the second region relative to the area S1 of the first region may be 40% or more. This means that the proportion of the area where the conductor 3 and the insulating film 1 are in contact with each other is sufficiently large. This further improves the adhesive strength between the conductor 3 and the insulating film 1. The larger the percentage (S2 / S1) x 100, the better the adhesive strength between the conductor 3 and the insulating film 1. The percentage (S2 / S1) x 100 may be 50% or more, 60% or more, 80% or more, 90% or more, or even 100%.

[0048] In the present disclosure, the developed interface area ratio Sdr of the second region and the percentage (S2 / S1)×100 are measured by the following procedure: First, in the state of the lead wire 10, the first region in the nickel plating layer 5 where the insulating film 1 is provided is identified.

[0049] The lead wire 10 is subjected to a 180° peel test at 25°C to separate the conductor 3 from the insulating film 1, thereby exposing the first region of the nickel plating layer 5. At this time, there is a possibility that a portion of the insulating film 1 remains in the first region of the nickel plating layer 5. To remove the remaining portion of the insulating film 1, the conductor 3 including the nickel plating layer 5 is immersed in a xylene solution at 120°C for 60 minutes.

[0050] The conductor 3 is removed from the xylene solution and dried, after which the developed interface area ratio Sdr of the first region of the nickel plating layer 5 is measured. For the measurement, a "VK-X100" (trademark) manufactured by Keyence Corporation is used. The arithmetic mean height Sa and maximum height Sz, which will be described later, are also measured using the same measuring device.

[0051] First, the first region is divided into rectangular unit regions of 0.2 mm x 0.2 mm, and the developed interface area ratio Sdr is measured for each unit region. Depending on the size and shape of the first region, the first region cannot be divided into an integral number of unit regions, and the unit region may include the first region and an area adjacent to the first region. In such cases, the unit region consisting only of the first region is measured, and the unit region including the first region and an area adjacent to the first region is excluded from the measurement.

[0052] The percentage (N2 / N1) of the number N2 of unit regions having a developed interface area ratio Sdr of 0.5 or more relative to the number N1 of all unit regions is calculated. In the present disclosure, the percentage (N2 / N1) x 100 corresponds to the percentage (S2 / S1) x 100.

[0053] The developed interface area ratio Sdr is measured for the entire region A, which consists of all unit regions having a developed interface area ratio Sdr of 0.5 or more. The unit regions included in region A may or may not be in contact with each other. In the present disclosure, region A corresponds to the second region, and the developed interface area ratio of region A corresponds to the developed interface area ratio of the second region.

[0054] In the lead wire 10 of the first embodiment, when the second region of the nickel plating layer 5 is divided into rectangular unit regions of 20 μm × 20 μm, the developed interface area ratio Sdr of all the unit regions may be 0.5 or more. This makes the developed interface area ratio Sdr uniform throughout the entire second region, further improving the adhesive strength between the conductor 3 and the insulating film 1.

[0055] The arithmetic mean height Sa of the second region of the nickel plating layer 5, as defined in JIS B 0681-2:2018, may be 0.1 μm or more. This further improves the adhesive strength between the conductor 3 and the insulating film 1. The larger the arithmetic mean height Sa of the second region, the more improved the adhesive strength between the conductor 3 and the insulating film 1. The lower limit of the arithmetic mean height Sa of the second region may be 0.2 μm or more, 0.4 μm or more, or 0.6 μm or more. The upper limit of the arithmetic mean height Sa of the second region is not particularly limited, but may be set to 2.0 μm or less from a manufacturing standpoint, for example. The arithmetic mean height Sa of the second region may be 0.1 μm or more and 2.0 μm or less, 0.4 μm or more and 2.0 μm or less, or 0.6 μm or more and 2.0 μm or more.

[0056] The second region of the nickel plating layer 5 may have a maximum height Sz of 1.0 μm or more as defined in JIS B 0681-2:2018. This further improves the adhesive strength between the conductor 3 and the insulating film 1. The greater the maximum height Sz of the second region, the more improved the adhesive strength between the conductor 3 and the insulating film 1. The lower limit of the maximum height Sz of the second region may be 3.0 μm or more, or 6.0 μm or more. The upper limit of the maximum height Sz of the first B region is not particularly limited, but may be set to 10.0 μm or less from a manufacturing standpoint, for example. The maximum height Sz of the first B region may be 1.0 μm or more and 10.0 μm or less, 3.0 μm or more and 10.0 μm or less, or 6.0 μm or more and 10.0 μm or less.

[0057] In the present disclosure, the arithmetic mean height Sa and maximum height Sz of the second region are measured by the following procedure: The second region is identified in the nickel plating layer 5 using the same method as the method for measuring the developed interface area ratio Sdr of the second region described above. The arithmetic mean height Sa and maximum height Sz of the second region are measured.

[0058] The nickel plating layer 5 may be a single layer or may be composed of multiple layers. When the nickel plating layer 5 is composed of multiple layers, the layers may have different crystal grain sizes. Whether the conductor 3 contains the nickel plating layer 5 can be confirmed by X-ray diffraction. Whether the nickel plating layer 5 is composed of a single layer or multiple layers can be confirmed by observing and analyzing the cross-sectional structure of the conductor 3 with a scanning electron microscope.

[0059] The nickel plating layer 5 may be composed of nickel metal whose crystal structure, as determined by X-ray diffraction, is a face-centered cubic lattice structure. The nickel plating layer 5 may include a region in which the ratio TC(111) / TC(200), of the orientation index TC(111) of the (111) plane to the orientation index TC(200) of the (200) plane calculated by Wilson's equation, is 0.2 or more and 2.0 or less. This facilitates an increase in the developed interface area ratio Sdr of the region of the nickel plating layer 5 in contact with the insulating film 1. The region in which the ratio TC(111) / TC(200) is 0.2 or more and 2.0 or less may be a region of the nickel plating layer 5 sandwiched between a second region on its surface and the surface of the substrate 4.

[0060] In the conventional conductor 3, the nickel plating layer 5 provided on the substrate 4 predominantly had a (200) orientation, which allows for the formation of a dense structure with excellent corrosion resistance, and the TC(111) / TC(200) ratio was less than 0.2. The nickel plating layer 5 with a predominant (200) orientation has a smooth surface, and therefore the surface of the conventional plating layer is smooth and the developed interface area ratio Sdr is less than 0.5. The nickel plating layer 5 with a (111) orientation has a rough surface, but compared to the (200) orientation, it has more defects and is more likely to reduce corrosion resistance, the nickel plating layer 5 becomes hard and is more likely to crack, and residual stress is more likely to occur, reducing adhesion to the substrate 4. For these reasons, a nickel plating layer 5 with a predominant (111) orientation has not been formed on a substrate 4 in the past. As a result of extensive research, the inventors have newly discovered that the adhesion between the conductor 3 and the insulating film 1 can be further improved by adjusting the balance between the (111) orientation and the (200) orientation in the nickel plating layer 5 so that the ratio TC(111) / TC(200) is 0.2 or more and 2.0 or less.

[0061] From the viewpoint of increasing the developed interface area ratio of the region of the nickel plating layer 5 in contact with the insulating film 1, the nickel plating layer 5 may include a region where TC(111) / TC(200) is 0.2 or more, a region where TC(111) / TC(200) is 0.5 or more, or a region where TC(111) / TC(200) is 0.8 or more. In these regions, the upper limit of TC(111) / TC(200) may be 2.0 or less, 1.5 or less, or 1.2 or less, from the viewpoint of densifying the structure of the nickel plating layer 5. The nickel plating layer 5 may include a region where TC(111) / TC(200) is 0.2 or more and 2.0 or less, a region where TC(111) / TC(200) is 0.5 or more and 1.5 or less, or a region where TC(111) / TC(200) is 0.8 or more and 1.2 or less.

[0062] The orientation index TC(111) may be 0.3 or more and 2.0 or less, or 0.5 or more and 1.5 or less, and the TC(200) may be 0.5 or more and 3.5 or less, or 0.8 or more and 2.5 or less.

[0063] In the present disclosure, the orientation index TC(hkl) is calculated by Wilson's formula shown in the following formula (1).

[0064]

[0065] In the formula (1), I(hkl) represents the X-ray diffraction intensity of the (hkl) reflection plane, and I ０ (hkl) indicates the standard intensity according to ICDD PDF card number 00-004-0850. Furthermore, n in formula (1) indicates the number of reflections used in the calculation, which is 3 in this embodiment. The (hkl) planes used for reflection are (111), (200), and (220).

[0066] ICDD (registered trademark) is an abbreviation for International Centre for Diffraction Data, and PDF (registered trademark) is an abbreviation for Powder Diffraction File.

[0067] TC(hkl) is calculated using Wilson's formula based on the results of X-ray diffraction measurement of the first C region. The conditions for the X-ray diffraction measurement are as follows: Measuring instrument: "Empyrean" (trademark) manufactured by Malvern Panalytical Characteristic X-rays: Cu-Kα Tube voltage: 45 kV Tube current: 40 mA Filter: multilayer mirror Optical system: focusing method X-ray diffraction method: θ-2θ method Scan speed: 1.8° / min Step: 0.03° Scan range: 5 to 40° When measuring X-ray diffraction, the insulating film 1 is peeled off from the conductor 3, and the surface exposing the nickel plating layer 5 is irradiated with X-rays.

[0068] In the lead wire 10 of embodiment 1, the average thickness of the nickel plating layer 5 may be 0.5 μm or more and 10.0 μm or less. From the viewpoint of forming the nickel plating layer 5 without any gaps, the lower limit of the average thickness of the nickel plating layer 5 may be 0.5 μm or more, 0.8 μm or more, 1.0 μm or more, or 2.0 μm or more. The upper limit of the average thickness of the nickel plating layer 5 is not particularly limited, but from the viewpoint of manufacturing, it may be 10.0 μm or less, 5.0 μm or less, or 2.5 μm or less. The average thickness of the nickel plating layer 5 may be 1.0 μm or more and 10.0 μm or less, or 2.0 μm or more and 5.0 μm or less.

[0069] In the present disclosure, the average thickness of the nickel plating layer 5 is measured as follows. The lead wire 10 is embedded in resin and polished to expose its cross section along the normal direction of the main surface exposed to the outside of the insulating film 1. The cross section is observed at 20,000x magnification using a scanning electron microscope, and the distance between the apex of the nickel plating layer 5 on the insulating film 1 side and the interface between the nickel plating layer 5 and the substrate 4 is measured at five points along the normal direction of the surface of the substrate 4. The average of the distances at the five points corresponds to the average thickness of the nickel plating layer 5.

[0070] As far as the applicant has measured, it has been confirmed that, as long as measurements are taken on the same sample, there is almost no variation in the measurement results even if the cut point of the lead wire 10 and the measurement point for the thickness of the nickel plating layer 5 on the cross section are arbitrarily set.

[0071] In the lead wire 10 of the first embodiment, the conductor 3 may be subjected to a surface treatment such as a chromate treatment, a trivalent chromium treatment, a non-chromate treatment, or a roughening treatment in order to improve resistance to an electrolyte solution, etc. Such a surface treatment can improve the resistance of the conductor 3 to an electrolyte solution.

[0072] In the lead wire 10 of the first embodiment, at least a portion of the surface of the nickel plating layer 5 facing the insulating film 1 may contain trivalent chromium. This improves the electrolytic solution resistance of the conductor 3 and suppresses corrosion. In the present disclosure, the presence of trivalent chromium on the surface of the nickel plating layer 5 can be confirmed by performing X-ray photoelectron spectroscopy on the nickel plating layer 5 that is exposed to the outside and not provided with the insulating film 1 in the lead wire 10.

[0073] In the lead wire 10 of the first embodiment, at least a portion of the surface of the nickel plating layer 5 facing the insulating film 1 may contain zirconium. This improves the electrolytic solution resistance of the conductor 3 and suppresses corrosion. In the present disclosure, the presence of zirconium on the surface of the nickel plating layer 5 can be confirmed by performing X-ray photoelectron spectroscopy on the nickel plating layer 5 that is exposed to the outside and not covered by the insulating film 1 in the lead wire 10.

[0074] 1 , the insulating film 1 covers the entire outer peripheral surface of the conductor 3 between both ends of the conductor 3 in a first direction while exposing both ends of the conductor 3. For example, the insulating film 1 covers the first main surface, the second main surface, and the first and second side surfaces connecting the first and second main surfaces of the conductor 3 between both ends of the conductor 3 in the first direction while exposing both ends of the conductor 3 in the first direction. The insulating film 1 is provided so as to cover the outer peripheral surface of a portion of the region in the first direction, excluding the region including both ends of the conductor 3 in the first direction. Therefore, the nickel plating layer 5 is provided at least between the substrate 4 and the insulating film 1.

[0075] 1 and 2 , the width of the insulating film 1 in the second direction of the conductor 3 is wider than the width of the conductor 3 in the second direction. The insulating film 1 is attached by adhesion or fusion to the outer peripheral surface of the conductor 3 so as to protrude beyond both ends of the conductor 3 in the second direction, and the insulating films 1 protruding from both ends of the conductor 3 are attached to each other by adhesion or fusion. The length of the conductor 3 in the first direction of the insulating film 1 is shorter than the length of the conductor 3 in the first direction. The insulating film 1 is not attached to both ends of the conductor 3 in the first direction.

[0076] The lower limit of the average thickness of the insulating film 1 may be 40 μm or more, 50 μm or more, 70 μm or more, 80 μm or more, 100 μm or more, or 120 μm or more. The upper limit of the average thickness may be 500 μm or less, 300 μm or less, or 250 μm or less. The average thickness may be 40 μm or more and 500 μm or less, 80 μm or more and 500 μm or less, 100 μm or more and 300 μm or less, or 120 μm or more and 250 μm or less.

[0077] In the present disclosure, the average thickness of the insulating film 1 is measured as follows. The lead wire 10 is embedded in resin and polished to expose a cross section along the normal direction of the main surface exposed to the outside of the insulating film 1. The cross section is observed at 500x magnification using a microscope, and the thickness of the insulating film 1 is measured at five points along the normal direction of the surface of the substrate 4. The average distance between the five points corresponds to the average thickness of the insulating film 1. In the present disclosure, the average thicknesses of the first insulating layer 1a, the second insulating layer 1b, and other layers described below are also measured in a similar manner.

[0078] <<First Insulating Layer>> In the lead wire 10 of embodiment 1, the insulating film 1 may include a first insulating layer 1a disposed in contact with the conductor 3. The first insulating layer 1a may be made of an acid-modified polypropylene layer. Examples of acid-modified groups include maleic anhydride. When the first insulating layer 1a is an acid-modified polypropylene layer, the first insulating layer 1a has good adhesion and sealing properties with the conductor 3. The acid-modified polypropylene layer may contain unmodified polypropylene as well as acid-modified polypropylene as a resin component, as long as the effects of the present disclosure are not impaired. Hereinafter, acid-modified polypropylene and unmodified polypropylene will also be collectively referred to as polypropylene.

[0079] The fact that the first insulating layer 1a contains an acid-modified group and that the first insulating layer 1a contains polypropylene can be confirmed by removing only the first insulating layer 1a from the lead wire 10 and performing transmission light analysis on the first insulating layer 1a using a Fourier transform infrared spectrophotometer.

[0080] In the insulating film 1 of embodiment 1, the average thickness of the first insulating layer 1a may be 20 μm or more and 150 μm or less. When the average thickness of the first insulating layer 1a is 20 μm or more, the first insulating layer 1a is less likely to be too thin and break, and good adhesion to the conductor 3 can be ensured. When the average thickness of the first insulating layer 1a is 150 μm or less, the insulating film 1 can be made thinner, and an electricity storage device including the insulating film 1 can be made smaller.

[0081] The lower limit of the average thickness of the first insulating layer 1a may be 20 μm or more, 25 μm or more, or 30 μm or more, from the viewpoint of ensuring good adhesion to the conductor 3. The upper limit of the average thickness of the first insulating layer 1a may be 150 μm or less, 120 μm or less, or 100 μm or less, from the viewpoint of miniaturizing the electricity storage device including the insulating film 1. The average thickness of the first insulating layer 1a may be 20 μm or more and 150 μm or less, 25 μm or more and 120 μm or less, or 30 μm or more and 100 μm or less.

[0082] In the lead wire 10 of the first embodiment, the first insulating layer 1a may contain various additives such as a flame retardant, an ultraviolet absorber, a light stabilizer, a heat stabilizer, a lubricant, a colorant, etc. The types and amounts of these additives may be similar to those used in conventionally known acid-modified polypropylene layers.

[0083] <Second Insulating Layer> In the lead wire 10 of the first embodiment, the insulating film 1 may further include a second insulating layer 1b provided on the main surface of the first insulating layer 1a opposite to the main surface in contact with the conductor 3. The second insulating layer 1b may be made of a heat-resistant resin layer. If the second insulating layer 1b is a heat-resistant resin layer, the second insulating layer 1b will not melt during thermocompression bonding between the insulating film 1 and the conductor 3, making the second insulating layer 1b an excellent support.

[0084] Examples of heat-resistant resins constituting the second insulating layer 1b include polyolefin resins, polyethylene terephthalate, polyamide, and fluororesin. Among these, polyolefin resins have good adhesion to the acid-modified polypropylene layer constituting the first insulating layer 1a. Examples of polyolefin resins include polyethylene, polypropylene, cross-linked polypropylene, ionomer resin, and acid-modified polyolefin. In particular, the second insulating layer 1b may contain homopolypropylene, a type of polypropylene. Homopolypropylene does not melt during thermocompression bonding between the adhesive film and the conductor 3, and therefore functions well as a support. The second insulating layer 1b may also contain polyester nonwoven fabric.

[0085] The fact that the second insulating layer 1b contains a heat-resistant resin can be confirmed by removing only the second insulating layer 1b from the lead wire 10 and performing transmission light analysis on the second insulating layer 1b using a Fourier transform infrared spectrophotometer.

[0086] In the insulating film 1 of embodiment 1, the average thickness of the second insulating layer 1b may be 20 μm or more and 150 μm or less. When the average thickness of the second insulating layer 1b is 20 μm or more, the second insulating layer 1b is less likely to be too thin and break, and good adhesion to the conductor 3 can be ensured. When the average thickness of the second insulating layer 1b is 150 μm or less, the insulating film 1 can be made thinner, and an electricity storage device including the insulating film 1 can be made smaller.

[0087] The lower limit of the average thickness of second insulating layer 1b may be 20 μm or more, 25 μm or more, or 30 μm or more from the viewpoint of ensuring good adhesion to conductor 3. The upper limit of the average thickness of second insulating layer 1b may be 150 μm or less, 120 μm or less, or 100 μm or less from the viewpoint of miniaturizing the electricity storage device including insulating film 1. The average thickness of second insulating layer 1b may be 20 μm or more and 150 μm or less, 25 μm or more and 120 μm or less, or 30 μm or more and 100 μm or less.

[0088] In the present disclosure, the second insulating layer 1b may contain various additives such as a flame retardant, an ultraviolet absorber, a light stabilizer, a heat stabilizer, a lubricant, a colorant, etc. The types and amounts of these additives may be the same as those used in conventionally known homopolypropylene layers.

[0089] <Other Layers> The insulating film 1 of embodiment 1 may include other layers in addition to the first insulating layer 1a and the second insulating layer 1b. Examples of the other layers include a layer (hereinafter also referred to as a "third insulating layer") that serves to improve adhesion to the sealed container 2 containing aluminum foil. The other layers may be a single layer or a combination of two or more layers. The positions of the other layers are appropriately selected depending on the types of the other layers.

[0090] The insulating film 1 may include a first insulating layer 1a, a second insulating layer 1b provided on one of the main surfaces of the first insulating layer 1a, and a third insulating layer provided on the main surface of the second insulating layer 1b opposite to the main surface facing the first insulating layer 1a.

[0091] In the insulating film 1 of embodiment 1, the average thickness of the third insulating layer may be 20 μm or more and 100 μm or less, 30 μm or more and 70 μm or less, or 35 μm or more and 60 μm or less.

[0092] In the present disclosure, the other layers may contain various additives such as flame retardants, ultraviolet absorbers, light stabilizers, heat stabilizers, lubricants, colorants, etc. The types and amounts of these additives may be similar to those used in other conventionally known layers.

[0093] <Method for Manufacturing Lead Wire> The lead wire of the first embodiment can be manufactured, for example, by the following method.

[0094] <<Preparation of Conductor>> A substrate made of copper or a copper alloy is prepared as the substrate. The size of the substrate is not particularly limited and can be appropriately set depending on the application of the lead wire. As a pretreatment, the substrate is immersed in a sodium hydroxide aqueous solution (concentration: 40 g / L) at 25°C, and a current density of 1.0 A / dm ２ After degreasing, the substrate is washed with running water.

[0095] Next, the washed substrate is immersed for 30 seconds in an aqueous sulfuric acid solution (concentration: 10% by mass) at 25° C. to perform acid activation. After acid activation, the substrate is washed with running water.

[0096] Next, nickel sulfate tetrahydrate (concentration: 500 g / L), nickel chloride hexahydrate (concentration: 30 g / L), and boric acid (concentration: 30 g / L) are mixed to obtain a first nickel plating solution. The acid-activated substrate is immersed in the first nickel plating solution at 50°C, and a current density of 5.0 A / dm ２ The substrate is plated with 0.1% ammonium hydroxide for 60 seconds (hereinafter also referred to as "first nickel plating"). After the first nickel plating, the substrate is washed with running water.

[0097] Next, nickel chloride hexahydrate (concentration: 200 g / L), ethylenediamine dihydrochloride (concentration: 200 g / L), and boric acid (concentration: 40 g / L) are mixed, and the pH is adjusted to 4.0 using an aqueous ammonia solution to obtain a second nickel plating solution. The substrate after the first nickel plating is immersed in the second nickel plating solution at 60°C, and a current density of 1.0 to 4.0 A / dm ２The substrate is then plated with a nickel plating layer on the surface of the substrate for 60 to 150 seconds (hereinafter also referred to as "second nickel plating"). After the second nickel plating, the substrate is washed with running water. This allows a conductor to be obtained in which a nickel plating layer is formed on the surface of the substrate.

[0098] The surface of the nickel plating layer can be subjected to a surface treatment. Chromium chloride hexahydrate (5.0 g / L) and potassium formate (170 g / L) are mixed with pure water to obtain a surface treatment solution. The substrate after the second nickel plating is immersed in the surface treatment solution at 45°C, and a current density of 10 A / dm ２ After the cathodic electrolysis, the substrate is washed with running water. This allows at least a portion of the surface of the nickel plating layer to contain trivalent chromium.

[0099] Another example of surface treatment is described below. 0.5 parts by mass of ammonium zirconium carbonate is added to an aqueous solution prepared by dissolving 1 part by mass of polyacrylic acid (manufactured by Nippon Shokubai Co., Ltd., molecular weight (Mw) 10,000) in 87.77 parts by mass of pure water, and 0.01 parts by mass of 25% aqueous ammonia is further added as a pH adjuster to obtain a mixed solution. The mixed solution is applied to the surface of the nickel plating layer and then dried at 120°C for 5 minutes. This allows at least a portion of the surface of the nickel plating layer to contain zirconium.

[0100] <<Preparation of Insulating Film>> Prepare an acid-modified polypropylene as the raw material for the first insulating layer and a heat-resistant resin as the raw material for the second insulating layer. If at least one of the first insulating layer and the second insulating layer contains an additive, prepare the additive. Mix the raw materials for the first insulating layer and the second insulating layer using a known mixing device such as an open roll, pressure kneader, single-screw kneader, or twin-screw kneader to obtain a mixed raw material.

[0101] The mixed raw materials for the first insulating layer and the second insulating layer are extruded using a co-extrusion T-die extruder to obtain an insulating film 1 in which the first insulating layer and the second insulating layer are laminated.

[0102] If the insulating film 1 includes other layers, a coat hanger-type three-type three-layer T-die film forming machine equipped with three single-screw extruders can be used to feed the mixed raw materials for the first insulating layer into the first extruder, the mixed raw materials for the second insulating layer into the second extruder, and the mixed raw materials for the other layers into the third extruder, and co-extrude to obtain the insulating film 1.

[0103] <<Fabrication of Lead Wire>> Next, the obtained insulating film 1 is cut to a predetermined size and heat-sealed to the main surface of the conductor at a mold temperature of 220° C. and a surface pressure of 0.3 MPa, thereby obtaining a lead wire.

[0104] [Embodiment 2: Electricity storage device] An electricity storage device according to one embodiment of the present disclosure (hereinafter also referred to as "embodiment 2") will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a front view schematically illustrating an example of an electricity storage device according to embodiment 2. Fig. 5 is a partial cross-sectional view taken along line V-V in Fig. 4.

[0105] The electricity storage device 30 according to the second embodiment includes an enclosed container 2 and the lead wire of the first embodiment arranged to extend from the inside to the outside of the enclosed container 2. The insulating film 1 is fused to the enclosed container 2. The lead wire 10 of the electricity storage device 30 according to the second embodiment has improved adhesion strength between the conductor 3 and the insulating film 1. Therefore, the electricity storage device 30 according to the second embodiment can maintain its performance even at high temperatures and has high reliability.

[0106] The electricity storage device 30 of the second embodiment includes a battery cell 15 including a positive electrode 20, a negative electrode 14, and an electrolyte 13 sandwiched between the positive electrode 20 and the negative electrode 14, conductors electrically connected to the positive electrode 20 and the negative electrode 14, and an enclosure 2 that seals the battery cell 15. A portion of the conductor is exposed to the outside of the enclosure 2, and the insulating film 1 of the first embodiment is disposed between the conductor and the enclosure 2. The first insulating layer of the insulating film 1 is disposed in contact with the conductor.

[0107] As shown in FIG. 5 , the sealed container 2 is made of a three-layer laminate film 8 consisting of a metal layer 16 and first and second resin layers 17 and 18 that coat the metal layer 16. The metal layer 16 is formed from a metal such as aluminum foil. The second resin layer 18, located on the exterior side of the sealed container 2, can be made of polyamide resins such as 6,6-nylon or 6-nylon, polyester resins, polyimide resins, etc. Furthermore, the first resin layer 17, located on the interior side of the sealed container 2, is preferably made of an insulating resin that is insoluble in nonaqueous electrolytes and melts when heated. Examples of insulating resins include polyolefin resins, acid-modified polyolefin resins, and acid-modified styrene-based elastomers. The sealed container 2 is fabricated by overlapping two laminate films 8 and heat-sealing the three edges excluding the edge through which the conductor passes. At the outer periphery of the sealed container 2, the two metal layers 16 are bonded via the first resin layer 17.

[0108] The conductor is bonded (thermally fused) to the sealed container 2 (laminate film 8) via the insulating film 1 at a seal portion 9. Further enclosed inside the electricity storage device 30 are a positive electrode 20, a negative electrode 14, and an electrolyte 13 connected to the ends of the conductor.

[0109] The electricity storage device 30 of the second embodiment may be an all-solid-state battery in which the electrolyte 13 is a solid electrolyte. This allows the insulating film 1 to maintain a high adhesive strength to the conductor for a long period of time, further improving the reliability of the electricity storage device 30.

[0110] The electricity storage device 30 of the second embodiment may be a non-aqueous electrolyte battery in which the electrolyte 13 is a non-aqueous electrolyte. Examples of the non-aqueous electrolyte include LiPF ６ , LiBF ４ Examples of suitable lithium salts include those obtained by dissolving fluorine-containing lithium salts such as those mentioned above in diethyl carbonate (DEC), dimethyl carbonate (DMC), propylene carbonate (PC), or the like.

[0111] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0112] <Preparation of Test Samples> <Preparation of Conductor> An oxygen-free copper plate (C1020) measuring 100 mm in length, 45 mm in width, and 0.2 mm in thickness was used as the substrate. Two types of substrates (substrate A and substrate B) with different surface roughness parameters of the main surface were prepared. Substrate A had a developed interface area ratio Sdr of 0.0 on the main surface, an arithmetic mean height Sa of 0.0 μm, and a maximum height Sz of 0.8 μm. Substrate B had a developed interface area ratio Sdr of 0.2 on the main surface, an arithmetic mean height Sa of 0.3 μm, and a maximum height Sz of 3.2 μm. The type of substrate used for each sample is shown in the "Substrate" column of Table 1.

[0113] As a pretreatment, the substrate was immersed in a sodium hydroxide aqueous solution (concentration: 40 g / L) at 25°C, and the current density was 1.0 A / dm ２ After the degreasing, the substrate was washed with running water.

[0114] Next, the washed substrate was immersed for 30 seconds in an aqueous sulfuric acid solution (concentration: 10% by mass) at 25° C. to perform acid activation. After acid activation, the substrate was washed with running water.

[0115] Next, nickel sulfate tetrahydrate (concentration: 500 g / L), nickel chloride hexahydrate (concentration: 30 g / L), and boric acid (concentration: 30 g / L) were mixed to obtain a first nickel plating solution. The acid-activated substrate was immersed in the first nickel plating solution at 50°C, and a current density of 5.0 A / dm ２ The first nickel plating was carried out at 400° C. for 60 seconds. After the first nickel plating, the substrate was washed with running water.

[0116] Next, nickel chloride hexahydrate (concentration: 200 g / L), ethylenediamine dihydrochloride (concentration: 200 g / L), and boric acid (concentration: 40 g / L) were mixed, and the pH was adjusted to 4.0 using an aqueous ammonia solution to obtain a second nickel plating solution. The substrate after the first nickel plating was immersed in the second nickel plating solution at 60°C to perform second nickel plating. The current density and time for the second nickel plating are shown in the "Current Density" and "Time" columns under "Second Nickel Plating Conditions" in Table 1. As a result, a nickel plating layer was formed on the substrate. The notation "-" in the "Current Density" and "Time" columns under "Second Nickel Plating Conditions" in Table 1 indicates that second nickel plating was not performed.

[0117] The values ​​in the "A2 / A1" column of the "Second Nickel Plating Conditions" section of Table 1 indicate the percentage (A2 / A1) × 100 of the area A2 of the region to be plated with second nickel relative to the total area A1, where A1 (corresponding to the area S1 of the first region) on one main surface of the substrate is 100% for the test samples described below. For samples with a value in the "A2 / A1" column of less than 100%, the second nickel plating was performed with a portion of the main surface of the substrate masked with a vinyl chloride plate to achieve the value in the "A2 / A1" column. For example, in Sample 2, the second nickel plating was performed with 40% of the total area A1 of the region to be plated with second nickel relative to the total area A1 on one main surface of the substrate in contact with the insulating film masked. As a result, the percentage (A2 / A1) × 100 of the area A2 of the region to be plated with second nickel relative to the total area A1 on one main surface of the substrate in contact with the insulating film was 60%. In sample 2, all unit areas provided in the area where the second nickel plating was performed have Sdr of 0.5 or more, so (S2 / S1) is 60%. Note that in the sample where no masking was performed, the percentage (A2 / A1)×100 of the area A2 of the area where the second nickel plating was performed to the total area A1 was 100%.

[0118] For samples with "Cr" in the "Cr / Zr" column in Table 2, surface treatment was carried out in the following manner. Chromium chloride hexahydrate (5.0 g / L) and potassium formate (170 g / L) were mixed with pure water to obtain a surface treatment solution. The substrate after the second nickel plating was immersed in the surface treatment solution at 45°C, and a current density of 10 A / dm ２ Cathodic electrolysis was performed at 100°C for 30 seconds. After cathodic electrolysis, the substrate was washed with running water. As a result, at least a portion of the surface of the nickel plating layer contained trivalent chromium.

[0119] The samples with "Zr" in the "Cr / Zr" column in Table 2 were surface treated using the following procedure. 0.5 parts by mass of ammonium zirconium carbonate was added to an aqueous solution prepared by dissolving 1 part by mass of polyacrylic acid (manufactured by Nippon Shokubai Co., Ltd., molecular weight (Mw) 10,000) in 87.77 parts by mass of pure water, and 0.01 parts by mass of 25% aqueous ammonia was further added as a pH adjuster to obtain a mixed solution. The mixed solution was applied to the surface of the nickel plating layer and then dried at 120°C for 5 minutes. This resulted in at least a portion of the surface of the nickel plating layer containing zirconium.

[0120] Through the above steps, each sample conductor was obtained, in which a nickel plating layer was formed on a substrate.

[0121] <<Preparation of insulating film>> Acid-modified polypropylene was prepared as the raw material for the first insulating layer, homopolypropylene as the raw material for the second insulating layer, and random polypropylene as the raw material for the other layers. The raw materials for the first insulating layer, the second insulating layer, and the other layers were each mixed using a mixer to obtain a mixed raw material.

[0122] Using a coat hanger-type three-kind, three-layer T-die film-forming machine equipped with three single-screw extruders, the mixed raw materials for the first insulating layer were fed into the first extruder, the mixed raw materials for the second insulating layer into the second extruder, and the mixed raw materials for the other layers into the third extruder, and co-extruded to obtain an insulating film in which an acid-modified polypropylene layer (corresponding to the first insulating layer), a homopolypropylene layer (corresponding to the second insulating layer), and a random polypropylene layer (corresponding to the other layers) were laminated in the above order. The average thickness of the acid-modified polypropylene layer was 50 μm, the average thickness of the homopolypropylene layer was 50 μm, and the average thickness of the other layers was 50 μm.

[0123] <<Preparation of Test Samples>> Next, the obtained insulating film was cut into a size of 55 mm in length and 10 mm in width, and heat-sealed to one of the main surfaces of the conductor at a mold temperature of 220°C and a surface pressure of 0.3 MPa, thereby obtaining test samples for each sample.

[0124]

[0125]

[0126] <Evaluation> <Measurement of surface roughness of nickel plating layer> For each test sample, the conductor and insulating film were separated by a 180° peel test at 25° C. to expose the nickel plating layer. The conductor including the nickel plating layer was immersed in a xylene solution at 120° C. for 60 minutes to remove part of the insulating film remaining on the exposed nickel plating layer.

[0127] The conductor was removed from the xylene solution and dried. The developed interface area ratio Sdr, percentage (S2 / S1) × 100, arithmetic mean height Sa of the second nickel-plated region of the nickel plating layer, maximum height Sz of the second nickel-plated region of the nickel plating layer, TC(111) / TC(200), and average thickness of the nickel plating layer were measured for the region where the second nickel plating was performed (if all unit regions in the region had an Sdr of 0.5 or greater, this corresponds to the second region). Specific measurement methods were as described in Example 1. The results are shown in Table 2. In Samples 1 to 10, all unit regions in the region where the second nickel plating was performed had an Sdr of 0.5 or greater. Samples 101 to 103 did not include any unit regions with an Sdr of 0.5 or greater, so Table 2 lists the Sdr of the region where the second nickel plating was performed.

[0128] Evaluation of Initial Adhesion One hour after the preparation of the test specimens for each sample, the adhesion between the conductor and the insulating film was measured by a 180° peel test at 25°C and 120°C. The pulling speed was 50 mm / min. In the present disclosure, 120°C is considered a high temperature. The results are shown in the "Initial 25°C" and "Initial 120°C" columns under "Peel Strength" in Table 3.

[0129] <Evaluation of adhesive strength after aging> A mixed solution was prepared by mixing ethylene carbonate, diethyl carbonate, and dimethyl carbonate in a volume ratio of 1:1:1. Lithium hexafluorophosphate (LiPF ６) was dissolved to a concentration of 1.0 mol / L, and water was added to a moisture content of 1000 ppm to prepare a test solution. Each test specimen was immersed in the test solution and left in a thermostatic chamber at 80°C for four weeks. The test specimen was then removed from the test solution, and the adhesive strength between the conductor and the insulating film was measured by a 180° peel test at 25°C. The tensile speed was 50 mm / min. The results are shown in the "After 25°C Aging" column of "Peel Strength" in Table 3.

[0130]

[0131] <Discussion> Samples 1 to 10 correspond to Examples, as the developed interface area ratio Sdr of the region of the nickel plating layer where the second nickel plating was performed (corresponding to the second region) is 0.5 or more. Samples 101 to 103 correspond to Comparative Examples, as the nickel plating layer does not include a region where the developed interface area ratio Sdr is 0.5 or more. It was confirmed that Samples 1 to 10 have superior adhesive strength between the conductor and the insulating film at high temperatures compared to Samples 101 to 103.

[0132] Although the embodiments and examples of the present disclosure have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined and modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0133] REFERENCE SIGNS LIST 1 insulating film, 1a first insulating layer, 1b second insulating layer, 2 encapsulation container, 3 conductor, 4 substrate, 5 nickel plating layer, 8 laminate film, 9 sealing portion, 10 lead wire, 13 electrolyte, 14 negative electrode, 15 battery cell, 16 metal layer, 17 first resin layer, 18 second resin layer, 20 positive electrode, 30 electricity storage device.

Claims

1. A lead wire comprising a conductor and an insulating film covering an outer peripheral surface of the conductor between both ends of the conductor while exposing both ends of the conductor in a first direction, wherein the conductor has: a base material made of copper or a copper alloy; and a nickel plating layer provided on the base material and disposed between the base material and the insulating film, the nickel plating layer including a first region in contact with the insulating film, the first region including a second region, and the developed interface area ratio Sdr of the second region as defined in JIS B 0681-2:2018 is 0.5 or more.

2. The lead wire as described in claim 1, wherein the arithmetic mean height Sa of the second region as defined in JIS B 0681-2:2018 is 0.1 μm or more, and the maximum height Sz of the second region as defined in JIS B 0681-2:2018 is 1.0 μm or more.

3. A lead wire as described in claim 1 or claim 2, wherein the percentage (S2 / S1) x 100 of the area S2 of the second region to the area S1 of the first region is 40% or more.

4. The lead wire according to any one of claims 1 to 3, wherein the nickel plating layer is composed of nickel metal whose crystal structure, as identified by X-ray diffraction, is a face-centered cubic lattice structure, and the nickel plating layer includes a region in which the ratio TC(111) / TC(200) of the orientation index TC(111) of the (111) plane to the orientation index TC(200) of the (200) plane, calculated by Wilson's formula, is 0.2 or more and 2.0 or less.

5. A lead wire according to any one of claims 1 to 4, wherein the average thickness of the nickel plating layer is 0.5 μm or more and 10.0 μm or less.

6. The lead wire according to any one of claims 1 to 5, wherein at least a portion of the surface of the nickel plating layer facing the insulating film contains trivalent chromium.

7. The lead wire according to any one of claims 1 to 5, wherein at least a portion of the surface of the nickel plating layer facing the insulating film contains zirconium.

8. A lead wire as described in any one of claims 1 to 7, wherein the insulating film includes a first insulating layer arranged in contact with the conductor and a second insulating layer provided on the surface of the first insulating layer opposite the conductor, the first insulating layer being an acid-modified polypropylene layer, and the second insulating layer being a heat-resistant resin layer.

9. An electricity storage device comprising: an enclosed container; and a lead wire described in any one of claims 1 to 8 arranged to extend from the inside to the outside of the enclosed container, wherein the insulating film is fused to the enclosed container.

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