Battery and evaluation method thereof

Abstract

To provide a battery excellent in sealing performance of an outer package at a part where a lead wire is positioned.SOLUTION: The battery 100 of the present disclosure includes an exterior body 13, a battery element 10, a lead wire 11, and an adhesive protective film 12. The sealing portion 30 is formed by the lead wire 11 being sandwiched between the adhesive protective film 12 and the exterior body 13, and the battery 100 includes the overlapping portion 21 of the heat-sealable resin layer of the exterior body 13, the lead wire 11, and the adhesive protective film 12, and when a force to peel off the exterior body 13 from the lead wire 11 is applied to the sealing portion 30, peeling occurs between the metal layer of the exterior body 13 and the adhesive protective film 12. When the exterior body 13 is peeled from the lead wire 11, the peeled surface on the lead wire 11 side corresponding to the overlapping portion 21 is whitened, and the ratio of the area of the whitened portion to the area of the overlapping portion 21 is 15% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a battery and a method for evaluating the same. [Background technology]

[0002] In recent years, lithium-ion batteries, which can be made smaller and lighter, have been developed as power storage devices for use in personal computers, mobile phones, video cameras, satellites, vehicles, and the like. As devices become more powerful, batteries are required to be made in a variety of shapes, and they are also required to be thinner and lighter. Laminate films have been proposed as an exterior material that can be easily processed into a variety of shapes and achieves thinner and lighter designs. Laminate films are packaging materials that include a metal layer and a heat-sealable resin layer provided on the inner surface of the metal layer.

[0003] When a laminate film exterior is used for a battery, the periphery of the exterior is heat-sealed with the heat-sealable resin layers facing each other so that the battery element is placed inside the exterior. The battery element is electrically connected to a load or power source via metal terminals (lead wires). That is, the metal terminals are sandwiched between the heat-sealable resin layers at the seal of the exterior and protrude outside the exterior.

[0004] In the sealing portion of the exterior body, the thickness of the heat-sealed resin layer is reduced in the area where the metal terminal is located due to the application of heat and pressure during welding, so an adhesive protective film is placed between the metal terminal and the exterior body in the area where the metal terminal is located.

[0005] The metal terminal is sandwiched between adhesive protective films and heat-sealed to adhere the adhesive protective films to the metal terminal. The adhesive protective films are then welded to the exterior body. This seals the area where the metal terminal is located (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-132538 Summary of the Invention [Problem to be solved by the invention]

[0007] The most important part of the sealing part of the exterior body is the part where the lead wires are located. If the sealing property in this part is poor, air or moisture will enter the interior of the exterior body, accelerating the deterioration of the battery element.

[0008] One object of the present disclosure is to provide a battery having an exterior body with excellent sealing properties in the area where the lead wires are located. Another object of the present disclosure is to provide a method for easily evaluating the sealing properties of the exterior body in the area where the lead wires are located. [Means for solving the problem]

[0009] The present disclosure provides: an exterior body including a metal layer and a heat-sealable resin layer; a battery element disposed inside the exterior body; a metal lead wire connected to the battery element and extending to the outside of the exterior body; an adhesive protective film disposed on the periphery of the exterior body so as to be positioned between the inner surface of the exterior body and the lead wire; A battery comprising: a seal portion is formed by sandwiching the lead wire between the adhesive protective film and the exterior body, the battery includes an overlapping portion of the heat-sealable resin layer of the exterior body, the lead wire, and the adhesive protective film, when a force is applied to the seal portion to peel the exterior body from the lead wire, peeling occurs between the metal layer of the exterior body and the adhesive protective film, When the outer casing is peeled from the lead wire, the peeled surface on the lead wire side corresponding to the overlapping portion turns white, The ratio of the area of ​​the whitened portion to the area of ​​the overlapping portion is 15% or more. Provide the battery. [Effects of the Invention]

[0010] According to the present disclosure, a battery can be provided that has an exterior body with excellent sealing properties in the area where the lead wires are located. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic plan view of a battery according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic cross-sectional view of the battery taken along line II-II shown in FIG. [Figure 3] FIG. 3 is a diagram showing the overlapping portion of the heat-sealable resin layer of the exterior body, the lead wires, and the adhesive protective film. [Figure 4] FIG. 4 is a flowchart showing a method for calculating the ratio (S1 / S0). [Figure 5] FIG. 5 is a schematic plan view of a test piece taken from a battery. [Figure 6] FIG. 6 is a diagram showing a method for producing samples of the example and comparative example. [Figure 7] 7(a) to (h) are images of the peeled surfaces of Example 1, Example 2, Comparative Example 1, Example 3, Example 4, Example 5, Example 6 and Comparative Example 3, respectively. [Figure 8A] FIG. 8A is a brightness histogram generated from an image of the peeled surface of the test specimen of Example 1. [Figure 8B] FIG. 8B is a brightness histogram generated from an image of the peeled surface of the test specimen of Example 3. [Figure 8C] FIG. 8C is a brightness histogram created from an image of the peeled surface of the test piece of Comparative Example 1. [Figure 9] FIG. 9 is a diagram showing the measurement positions of the 60-degree specular gloss. [Figure 10] FIG. 10 is a diagram showing the measurement results of 60-degree specular gloss. DETAILED DESCRIPTION OF THE INVENTION

[0012] (Findings that formed the basis of this disclosure) Exterior packaging is required to have various properties such as sealing ability, chemical resistance, draw formability, water vapor barrier property, heat resistance, and insulation. To provide an exterior packaging with good sealing ability, it is necessary to determine the heat welding conditions according to the thickness and materials of components such as laminate film, lead wires, and adhesive protective film. Heat welding conditions include temperature, pressure, and time.

[0013] In particular, the sealing portion of the exterior body where the lead wires are located requires precise control of welding conditions such as temperature, pressure, and time. This is because the area where the lead wires are located has different reasons from other areas, such as unevenness, heat dissipation through the lead wires during welding, and the need to maintain insulation between the lead wires and the metal layer of the laminate film. Therefore, the process of determining the heat welding conditions tends to be complicated.

[0014] The present inventors have conducted extensive research into the portion of the sealing portion of the exterior body where the lead wire is located, and have found that there is a correlation between the sealing performance of the portion where the lead wire is located and the appearance of the lead wire when the exterior body is peeled off, which has led to the completion of the present disclosure.

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0016] (Embodiment) Fig. 1 is a schematic plan view of a battery according to an embodiment of the present disclosure. Fig. 2 is a schematic cross-sectional view of the battery taken along line II-II shown in Fig. 1. As shown in Figs. 1 and 2, a battery 100 includes a battery element 10, lead wires 11, an adhesive protective film 12, and an exterior body 13.

[0017] The exterior body 13 may be a container made of a laminate film. The laminate film is a packaging material including a metal layer and a heat-sealable resin layer provided on the inner surface of the metal layer. The metal layer is, for example, a layer containing aluminum foil. The heat-sealable resin layer is, for example, a layer containing a thermoplastic resin such as polyolefin, acrylic, polyester, or polyurethane. The heat-sealable resin layer is also called a hot-melt resin layer. A resin layer may be provided on the outer surface of the metal layer. When the battery 100 is viewed from above, the peripheral portion 13a of the exterior body 13 may be a seal portion 30 formed by heat welding. The seal portion 30 may be a rectangular frame shape or a U-shape when viewed from above.

[0018] The battery element 10 is an electrode group including a positive electrode, a separator, and a negative electrode. The type of battery element 10 is not particularly limited. The battery element 10 may be a lithium battery, a nickel-metal hydride battery, or other battery element. The battery element 10 may be a battery element using a liquid electrolyte, a battery element using a gel electrolyte, a battery element using a solid electrolyte, or an all-solid-state battery. The battery element 10 may be a battery element for a primary battery or a battery element for a secondary battery.

[0019] When the battery element 10 is a battery element or all-solid-state battery using a solid electrolyte, the intrusion of air into the exterior can be suppressed, thereby suppressing denaturation of the solid electrolyte. Furthermore, if gas is generated due to denaturation of the solid electrolyte, leakage of the generated gas to the outside can be suppressed. The solid electrolyte contained in the battery element denatures when exposed to air, and the ion conductivity of the denatured portion may decrease, resulting in degradation of battery performance. Furthermore, when the solid electrolyte denatures, corrosive or harmful gases may be generated, causing corrosion of metals contained in the battery element and reducing the reliability of the battery. Furthermore, if the generated gas leaks outside the exterior, it may cause corrosion of metal components arranged around the battery or have adverse effects on living organisms or the environment. Therefore, the technology disclosed herein can solve problems specific to battery elements or all-solid-state batteries using a solid electrolyte.

[0020] The lead wire 11 is a strip-shaped member for extracting power from and / or supplying power to the battery element 10. The lead wire 11 is made of a metal material such as nickel, aluminum, or copper. One of the pair of lead wires 11 is electrically connected to the positive electrode of the battery element 10. The other of the pair of lead wires 11 is electrically connected to the negative electrode of the battery element 10. The lead wires 11 extend outside the exterior body 13. Multiple lead wires 11 may be arranged on only one side of the rectangular exterior body 13, or lead wires 11 may be arranged on each of multiple sides of the rectangular exterior body 13.

[0021] The adhesive protective film 12 is disposed on the peripheral edge 13a of the exterior package 13 so as to be located between the inner surface of the exterior package 13 and the lead wires 11. The adhesive protective film 12 is a resin member having a rectangular shape, and is also called a sealant film. The resin constituting the adhesive protective film 12 may be a thermoplastic resin such as polyolefin, acrylic, polyester, or polyurethane. The adhesive protective film 12 may have a multilayer structure. The adhesive protective film 12 is provided on each of the pair of lead wires 11. The adhesive protective film 12 may be provided across the pair of lead wires 11.

[0022] The lead wire 11 is covered with an adhesive protective film 12. This structure can be obtained, for example, by sandwiching the lead wire 11 between two adhesive protective films 12 and applying heat and pressure to the lead wire 11 and the adhesive protective films 12.

[0023] The seal portion 30 of the exterior body 13 includes a portion where the lead wire 11 and the adhesive protective film 12 are present and a portion where the lead wire 11 and the adhesive protective film 12 are not present. The portion where the lead wire 11 and the adhesive protective film 12 are present is formed by sandwiching the lead wire 11 between the adhesive protective film 12 and the exterior body 13 through a welding process. The portion where the lead wire 11 and the adhesive protective film 12 are not present is formed by joining the heat-sealable resin layers of the exterior body 13 together through a welding process.

[0024] 3 is a diagram showing an overlapping portion of the heat-sealable resin layer of the exterior body 13, the lead wire 11, and the adhesive protective film 12. The battery 100 includes an overlapping portion 21 indicated by diagonal lines. The overlapping portion 21 is a portion where the heat-sealable resin layer of the exterior body 13, the lead wire 11, and the adhesive protective film 12 are joined to one another.

[0025] According to this embodiment, when a force is applied to the seal portion 30 to peel the exterior body 13 from the lead wire 11, peeling occurs between the metal layer of the exterior body 13 and the adhesive protective film 12. The metal layer of the exterior body 13 is not transferred onto the surface of the lead wire 11. When the exterior body 13 is peeled from the lead wire 11, the peeled surface on the lead wire 11 side corresponding to the overlapping portion 21 whitens. In other words, the peeled surface includes a whitened portion. The ratio (S1 / S0) of the area S1 of the whitened portion to the area S0 of the overlapping portion 21 is 15% or more. This configuration provides sufficient strength and leak prevention to the portion of the seal portion 30 of the exterior body 13 where the lead wire 11 is located. The present disclosure provides a battery 100 with excellent sealing properties of the exterior body 13 in the portion where the lead wire 11 is located.

[0026] When the exterior body 13 is peeled off from the lead wire 11, the adhesive protective film 12 and the heat-sealable resin layer of the exterior body 13 whiten and remain on the peeled surface of the lead wire 11. With this configuration, the degree of whitening, that is, the above-mentioned ratio (S1 / S0), can be calculated. The calculated ratio (S1 / S0) can be used to evaluate the seal portion 30 of the exterior body 13.

[0027] When the battery 100 is completed, the heat-sealable resin layers of the adhesive protective film 12 and the exterior casing 13 may be transparent. The heat-sealable resin layers of the adhesive protective film 12 and the exterior casing 13 may contain colorants such as inorganic pigments and organic pigments, as long as it is possible to distinguish between whitened and non-whitened portions using the method described below. For example, the whitening phenomenon on the peeled surface can be detected if the visible light transmittance of the heat-sealable resin layers of the adhesive protective film 12 and the exterior casing 13 is 20% or higher before the battery 100 is assembled. Alternatively, the whitening phenomenon on the peeled surface can be detected if the 60-degree specular gloss of the overlapping portion 21 after the battery 100 is assembled is 35 or higher. These two requirements may be met. The visible light transmittance of the heat-sealable resin layers of the adhesive protective film 12 and the exterior casing 13 can be measured using standard light A according to the method specified in Japanese Industrial Standard JIS T 8141 (2016). The 60-degree specular gloss of the overlapping portion 21 can be measured by the method described below after removing the metal layer of the exterior body 13.

[0028] Whitening is presumed to be a phenomenon indicating that the resin has stretched and undergone plastic deformation. When the adhesive protective film 12 and the heat-sealable resin layer of the exterior body 13 are melted and strongly bonded to each other, whitening is likely to occur when the exterior body 13 is peeled off from the lead wire 11. Therefore, it is possible to evaluate the seal portion 30 of the exterior body 13 based on the ratio (S1 / S0).

[0029] The ratio (S1 / S0) may be 15% or more and 90% or less.

[0030] The ratio (S1 / S0) varies depending on the sealing device and sealing conditions used to form the seal portion 30. The sealing conditions include temperature, pressure, time, etc. By adjusting these sealing conditions depending on the sealing device, a battery 100 exhibiting a desired ratio (S1 / S0) can be manufactured.

[0031] The peeled surface on the lead wire 11 side may include an unwhitened portion. The portion other than the whitened portion is the unwhitened portion. The ratio (S2 / S0) of the area S2 of the unwhitened portion to the area S0 of the overlapping portion 21 is, for example, 10% or more and 85% or less in percentage.

[0032] If the metal layer of the exterior body 13 is thin, the strength of the metal layer will be lower than the adhesive strength between the exterior body 13 and the adhesive protective film 12, and the metal layer of the exterior body 13 may break and remain on the surface of the lead wire 11 when the exterior body 13 is peeled off from the lead wire 11. In order for the exterior body 13 to have sufficient strength and good draw formability, it is desirable that the metal layer of the exterior body 13 has a thickness that does not leave a metal layer on the surface of the lead wire 11 when the exterior body 13 is peeled off from the lead wire 11. In one example, the thickness of the metal layer of the exterior body 13 is 15 μm or more and 50 μm or less.

[0033] If the adhesive strength between the lead wire 11 and the adhesive protective film 12 is weak, peeling between the lead wire 11 and the adhesive protective film 12 is likely to occur when peeling the exterior body 13 from the lead wire 11. In this case, the adhesive protective film 12 is unlikely to remain on the peeled surface on the lead wire 11 side. In order for the seal portion 30 of the exterior body 13 to have sufficient strength and leak prevention properties, it is desirable that the adhesive strength between the lead wire 11 and the adhesive protective film 12 is strong enough that the adhesive protective film 12 remains on the peeled surface on the lead wire 11 side when the exterior body 13 is peeled from the lead wire 11.

[0034] The ratio (S1 / S0) of the area of ​​the whitened portion to the area of ​​the overlapping portion 21 (see FIG. 3) can be calculated by the following method. Fig. 4 is a flowchart showing the method for calculating the ratio (S1 / S0). Fig. 5 is a schematic plan view of a test piece taken from the battery 100.

[0035] As shown in step S1, a strip-shaped test piece 15 including a seal portion 30 is taken from the battery 100. As shown in FIG. 5, the test piece 15 includes a lead wire 11, an adhesive protective film 12, and an exterior body 13. The width W of the test piece 15 is adjusted so that the entire lead wire 11 is included in the test piece 15. The width W is, for example, (W0 + 2 mm) or more and (W0 + 5 mm) or less, where W0 is the width of the lead wire 11.

[0036] Next, in step S2, force is applied to test piece 15 to peel exterior body 13 from lead wire 11. Specifically, each of the two laminate films that make up exterior body 13 is grasped, and the two laminate films are pulled in opposite directions at 180 degrees at a predetermined speed until exterior body 13 peels from lead wire 11. The series of operations in step S2 may be performed in accordance with the T-peel test specified in Japanese Industrial Standard JISK 6854-3 (1999).

[0037] Next, in step S3, the peeled surface on the lead wire 11 side is photographed with a digital camera. Specifically, an image of the peeled surface on the lead wire 11 side corresponding to the overlapping portion 21 is obtained. The image is, for example, an RGB image.

[0038] Next, in step S4, the obtained image is binarized to calculate the ratio (S1 / S0). Specifically, image processing software (e.g., ImageJ) is used to convert the RGB image (24-bit image) to an 8-bit image. In other words, the RGB image is converted to grayscale. The brightness and contrast of the grayscaled image may be automatically adjusted. Next, a luminance histogram of the grayscaled image is created. The horizontal axis of the luminance histogram represents luminance. The vertical axis of the luminance histogram represents the number of pixels having the corresponding luminance. The luminance histogram of the test piece 15 in which whitening has occurred shows two peaks. The peak on the right side of the luminance histogram (the peak on the high luminance side) is a peak based on the pixels in the whitened area. The peak on the left side of the luminance histogram (the peak on the low luminance side) is a peak based on the other pixels. Furthermore, the bottom position between the two peaks is set as a threshold, and each pixel in the image is binarized into a white area and another area. The ratio (S1 / S0) is calculated by dividing the number of pixels contained in the white region in the binarized image by the total number of pixels in the image. A single peak appears in the brightness histogram of a test piece 15 in which no whitening has occurred. In this case, the bottom position to the right of the peak is set as the threshold value, and the image is binarized. The threshold value between the two peaks can be determined by a method based on Otsu's binarization method, as described below.

[0039] The resolution of the RGB image of the peeled surface on the lead wire 11 side corresponding to the overlapping portion 21 is preferably, for example, 600 ppi or more. When the resolution of the RGB image of the peeled surface is sufficiently high, the two peaks tend to be clearly separated in the brightness histogram.

[0040] As will be described later, the tensile strength measured when peeling the outer casing 13 from the lead wire 11 of the test piece 15 correlates with the ratio (S1 / S0). When the ratio (S1 / S0) is large, the tensile strength also is large. Therefore, the ratio (S1 / S0) can be used to evaluate the sealing performance of the seal portion 30.

[0041] Alternatively, optical measurement of the peeled surface on the lead wire 11 side corresponding to the overlapping portion 21 can be performed by other methods. Specifically, the specular gloss of the peeled surface is measured. If the peeled surface includes a whitened portion, the 60-degree specular gloss of the whitened portion is, for example, 30 or less. The 60-degree specular gloss of the whitened portion may be 15 or less. With this configuration, it is possible to easily estimate that the seal portion 30 of the exterior body 13 has excellent sealing properties, and the accuracy of the estimation can be improved.

[0042] The lower limit of the 60-degree specular gloss of the whitened portion is not particularly limited, and is 2, for example.

[0043] The 60-degree specular gloss may be measured at multiple points on the peeled surface. For example, the rectangular peeled surface may be divided into nine rectangular sections with equal areas. The 60-degree specular gloss may be measured for each of the nine rectangular sections.

[0044] The 60-degree specular gloss can be measured using a glossmeter that can measure the specular gloss of an area smaller than the overlapping portion 21 shown in Figure 3. The 60-degree specular gloss can be measured according to the method specified in Japanese Industrial Standard JIS Z 8741 (1997).

[0045] (Other embodiments) (Addendum) The above description of the embodiments discloses the following techniques.

[0046] (Technology 1) an exterior body including a metal layer and a heat-sealable resin layer; a battery element disposed inside the exterior body; a metal lead wire connected to the battery element and extending to the outside of the exterior body; an adhesive protective film disposed on the periphery of the exterior body so as to be positioned between the inner surface of the exterior body and the lead wire; A battery comprising: a seal portion is formed by sandwiching the lead wire between the adhesive protective film and the exterior body, the battery includes an overlapping portion of the heat-sealable resin layer of the exterior body, the lead wire, and the adhesive protective film, when a force is applied to the seal portion to peel the exterior body from the lead wire, peeling occurs between the metal layer of the exterior body and the adhesive protective film, When the outer casing is peeled from the lead wire, the peeled surface on the lead wire side corresponding to the overlapping portion turns white, The ratio of the area of ​​the whitened portion to the area of ​​the overlapping portion is 15% or more. battery.

[0047] According to the present disclosure, a battery can be provided that has an exterior body with excellent sealing properties in the area where the lead wires are located.

[0048] (Technology 2) The battery according to Art. 1, wherein the whitened portion has a 60-degree specular gloss of 30 or less.

[0049] (Technology 3) The battery according to Art 1, wherein the 60-degree specular gloss of the whitened portion is 15 or less.

[0050] According to Techniques 2 and 3, it is possible to easily estimate whether the seal portion of the exterior body has excellent sealing properties, and the accuracy of the estimation can be improved.

[0051] (Technology 4) The battery according to any one of the first to third aspects, wherein the ratio is 90% or less.

[0052] (Technology 5) The battery according to any one of Techniques 1 to 4, wherein the battery element includes a solid electrolyte. The technique of the present disclosure can solve problems specific to battery elements using a solid electrolyte.

[0053] (Technology 6) 6. The battery according to any one of Techniques 1 to 5, wherein the battery element is an all-solid-state battery. The technique of the present disclosure can solve problems specific to all-solid-state batteries.

[0054] (Technology 7) A method for evaluating a battery, comprising: The battery comprises: an exterior body including a metal layer and a heat-sealable resin layer; a battery element disposed inside the exterior body; a metal lead wire connected to the battery element and extending to the outside of the exterior body; an adhesive protective film disposed on the periphery of the exterior body so as to be positioned between the inner surface of the exterior body and the lead wire; Equipped with a seal portion is formed by sandwiching the lead wire between the adhesive protective film and the exterior body, the battery includes an overlapping portion of the heat-sealable resin layer of the exterior body, the lead wire, and the adhesive protective film, The evaluation method includes: taking a test piece including the seal portion from the battery; applying a force to the test piece to peel the outer casing from the lead wire; performing an optical measurement of the peeled surface on the lead wire side corresponding to the overlapping portion; Including, The optical measurement includes at least one selected from the group consisting of calculating a ratio of an area of ​​a whitened portion included in the peeled surface to an area of ​​the overlapping portion, and measuring a specular gloss of the peeled surface. Battery evaluation methods.

[0055] According to the present disclosure, it is possible to easily evaluate the sealing property of an exterior body in the portion where a lead wire is located. [Example]

[0056] The present disclosure will be described in more detail below with reference to examples, although the present disclosure is not limited to these examples.

[0057] [1] Preparation process A tab lead and an outer casing were prepared. The tab lead is a component obtained by welding a pair of adhesive protective films to a lead wire.

[0058] [1.1] Tab lead A tab lead (PLUS LEAD-0.2X10.0(ALF-O)X1X54.0-P14.0-PP(8.5)-COIL, manufactured by Sumitomo Electric Industries, Ltd.) was prepared. In the tab lead, the lead wire had dimensions of 10 mm width and 0.2 mm thickness. In the tab lead, each of a pair of adhesive protective films had dimensions of 14 mm width and 8.5 mm length. In the width direction, both ends of the adhesive protective film protruded 2 mm from the lead wire. The total thickness of the lead wire and the pair of adhesive protective films was 0.4 mm. The protrusion lengths of the lead wire from both ends of the adhesive protective film were 10 mm and 20 mm.

[0059] [1.2] Exterior body An aluminum laminate film (D-EL40H(3) manufactured by Dai Nippon Printing Co., Ltd.) was prepared as the exterior material. The aluminum laminate film had an outer layer with a thickness of approximately 23 μm, an aluminum foil with a thickness of approximately 40 μm, and an inner layer with a thickness of approximately 45 μm. The aluminum laminate film was cut into a size of 80 mm × 50 mm.

[0060] [2] Welding process FIG. 6 is a diagram showing a method for producing samples of the examples and comparative examples. As shown in FIG. 6, two tab leads 40 were placed between two laminate films 42 and welded. The distance between the lead wires 11 of the two tab leads 40 was 10 mm. The orientation of the tab leads 40 was determined so that the side of the lead wire 11 with the shorter protrusion length from the adhesive protective film 12 was positioned on the outside of the laminate film 42. The adhesive protective film 12 protruded 1 mm outside the laminate film 42. In the welding process, a 6 mm-wide portion 42a including the tip of the laminate film 42 was brought into contact with the heating part of a sealing device.

[0061] Welding to prepare test pieces for the Examples and Comparative Examples was carried out using the sealing devices and sealing conditions shown in Table 1. Sealing device A (manufactured by Fuji Impulse Co., Ltd., FCB-200) and sealing device B (manufactured by Fuji Impulse Co., Ltd., TK-230) were used as sealing devices.

[0062] For welding using sealing device A, the heating temperature (set temperature) of the sealing device was set to 200°C, 190°C, or 180°C. The heating time was 3 seconds. The chamber pressure was -50 kPa. The cooling temperature was 60°C.

[0063] For welding using sealing device B, the dials for adjusting the heating temperature and heating time of the sealing device were set to 10, 9, 8, 7, or 6. A braided heater was used as the heater wire for sealing device B.

[0064] Tab leads and laminated films were used in welding in Examples 1 to 6 and Comparative Examples 1 and 3. In welding in Comparative Examples 2 and 4, a polyethylene terephthalate (PET) film with a thickness of 38 μm was used instead of the laminated film.

[0065] [Table 1]

[0066] [3] Measurement of the temperature of the welded surface The temperature of the contact surface between the adhesive protective film and the laminate film during welding (temperature of the welded surface) was measured according to the method described below.

[0067] A thermocouple (KFT-50-200-200, manufactured by Ambesmt Co., Ltd.) with a tip diameter of 50 μm was placed between the adhesive protective film and the laminate film so that the temperature measurement junction was located at the center of the overlapping portion 21 shown in Figure 3. The thermocouple was connected to a data logger (GL240, manufactured by Graphtec Corporation), and the temperature during welding was measured at a sampling interval of 100 ms. The welding process was carried out according to the method described in section [2], and the maximum temperature measured during welding was considered to be the temperature of the welded surface. The temperature of the welded surface was measured when the thermocouple was placed on the top side of the lead wire and when the thermocouple was placed on the bottom side of the lead wire. The results are shown in Table 1.

[0068] As shown in Table 1, the temperatures of the welding surfaces in the examples and comparative examples using sealing device A ranged from 121°C to 136°C. These temperatures were 59°C to 66°C lower than the set temperature of sealing device A. This is presumably due to heat dissipation through the lead wires during welding. The temperatures of the welding surfaces in the examples and comparative examples using sealing device B ranged from 109°C to 151°C.

[0069] For Comparative Examples 2 and 4, in which PET film was used instead of laminate film, the temperature of the welding surface was not measured because the PET film was not adhered to the tab lead. The thickness of the PET film was less than the thickness of the inner layer of the laminate film shown in item [1.2]. Therefore, it is presumed that the temperature of the welding surface in Comparative Examples 2 and 4 reached a temperature higher than that measured when the laminate film was welded under the same sealing conditions.

[0070] [4] Evaluation of sealing performance The sealing properties of the seal portions of the samples of the example and comparative example described with reference to Fig. 6 were evaluated according to the method described below. No thermocouple was placed.

[0071] First, the two left and right sides of the welded sample (Fig. 6) were welded using sealing device B (temperature setting 7). After that, a seal inspection liquid (Fuji Impulse Perfect Seal Checker) was sprayed onto the inside of the seal on the side where the lead wire was located.

[0072] Next, the unwelded side of the sample was welded using sealing device B (temperature setting 7). After leaving it to stand for more than 2 hours, the sealability was evaluated by visually checking whether the seal inspection liquid had leaked out. The results are shown in Table 1.

[0073] When no seepage of the seal inspection liquid was confirmed, the result was evaluated as ◯ (good seal). When seepage of the seal inspection liquid was confirmed, the result was evaluated as × (poor seal). For Comparative Examples 2 and 4, the PET film and the tab lead were not bonded, so the evaluation of the sealability was omitted.

[0074] As shown in Table 1, sealing device A was used to produce the samples of Example 1, Example 2, and Comparative Example 1. Poor sealing occurred when the set temperature was 180°C. However, no poor sealing occurred when the set temperatures were 190°C and 200°C. Sealing device B was used to produce Examples 3 to 6 and Comparative Example 3. Poor sealing occurred when the set temperature was 6. However, no poor sealing occurred when the set temperatures were 7 to 10. It is presumed that under the conditions where poor sealing occurred, the temperature of the welding surface was too low, resulting in insufficient deformation of the inner layer of the laminate film and the adhesive resin film during welding, making it impossible to seal the irregularities in the tab lead and leaving pinholes.

[0075] [5] Measurement of weld strength The welding strength (tensile strength) of the sealed portion was measured according to the method described below.

[0076] First, two test pieces for measuring tensile strength were taken from the welded sample (Figure 6). The test pieces for measuring tensile strength were as described with reference to Figure 5. The width (W) of the test piece was 14 mm. Next, each end of the two laminate films included in the test piece was attached to the grips of a tensile testing machine (A&D, MCT-2150) with a grip distance of 30 mm. A tensile load was then applied to the test piece at a relative movement speed of 300 mm / min until the seal broke. The maximum load (N) from the start of the test to the test piece breaking was measured. The tensile strength (N / 15 mm) was calculated according to the following formula (1). The results are shown in Table 1.

[0077] Tensile strength = Maximum load / (Width of test piece / 15 mm) (1)

[0078] The "width of the test piece" in formula (1) was 14 mm. Based on the assumption that the width of the test piece and the maximum load are proportional to each other, formula (1) can be used to calculate the maximum load when the width of the test piece is 15 mm.

[0079] The tensile strength shown in Table 1 is the average value of the tensile strength of two test pieces. For Comparative Examples 2 and 4, the PET film was not adhered to the tab lead, so measurement of the tensile strength was omitted.

[0080] After measuring the tensile strength, the peeled surfaces of the test pieces with the remaining lead wires were observed visually and microscopically. As a result, in all test pieces, the aluminum layer of the laminate film was absent on the peeled surface on the lead wire side, and only the adhesive protective film remained. In other words, the test pieces had peeled between the metal layer of the laminate film and the adhesive protective film.

[0081] As shown in Table 1, regardless of the sealing device used, the tensile strength increased as the temperature of the welding surface increased. This result suggests that as the temperature of the welding surface increased, the inner layer of the laminate film (thermal adhesive resin layer) and the adhesive protective film were firmly heat-sealed. If PET film were used instead of the laminate film, heat fusion would not occur at the welding surface temperatures shown in Table 1 due to the high softening point of PET, among other reasons.

[0082] [6] Observation of the peeling surface on the lead wire side After measuring the tensile strength, the peeled surface of the test piece with the remaining lead wire was observed. Specifically, the presence or absence of whitened areas was visually checked in the area corresponding to the overlapping portion 21 described with reference to Figure 3. The results are shown in Table 1.

[0083] The peeled surfaces of the test pieces of Examples 1 to 6 had whitened areas. In other words, whitening had occurred. The peeled surfaces of the test pieces of Comparative Examples 1 and 3 did not have whitened areas. In other words, whitening had not occurred. As can be seen from the results shown in Table 1, there was a correlation between sealing property, tensile strength, and the presence or absence of whitened areas. As shown by the results of Examples 1 to 6, under the conditions of the Examples, high tensile strength of 52 N / 10 mm or more and good sealing property were achieved. Under the conditions of the Comparative Examples, poor sealing occurred and the tensile strength was also low.

[0084] The peeled surfaces of the test pieces of Comparative Examples 2 and 4 also had no whitened areas. This result indicates that the peeled surface may not whiten even if the welding temperature is increased. It is presumed that the whitening occurs because, when the laminate film is peeled from the lead wire, the lead wire stretches and deforms, and the heat-sealed resin in the inner layer of the laminate film stretches, deforms, and breaks, remaining on the lead wire side.

[0085] [7] Area ratio of whitened areas After measuring the tensile strength, RGB images of the peeled surface of the test specimen were taken with a digital camera. The image of the peeled surface corresponding to the overlapping portion 21 (Figure 3) was extracted. The dimensions of the peeled surface corresponding to the overlapping portion 21 were 10 mm × 8.5 mm. The number of pixels contained in the image of the peeled surface corresponding to the overlapping portion 21 was between 46,000 and 53,000.

[0086] 7(a) to (h) are images of the peeled surfaces of Example 1, Example 2, Comparative Example 1, Example 3, Example 4, Example 5, Example 6 and Comparative Example 3, respectively.

[0087] Next, the resulting RGB images were converted to 8-bit grayscale using image processing software (ImageJ). The brightness and contrast of the grayscale images were automatically adjusted using the image processing software.

[0088] Next, image processing software was used to create brightness histograms of the grayscaled images. Figures 8A, 8B, and 8C are brightness histograms created from images of the peeled surfaces of the test pieces of Example 1, Example 3, and Comparative Example 1, respectively. The vertical axis represents frequency (%). The horizontal axis represents brightness. The right side of the graph represents the high brightness side. Each figure shows the degree of separation used in Otsu's binarization method, which will be described later, and the threshold value set when binarizing the pixels contained in the image.

[0089] A threshold value was determined from these luminance histograms using Otsu's binarization method, and all pixels in the image were binarized as white or black. The ratio of the number of white pixels to the total number of pixels in the image was calculated as the "area ratio of the whitened portion." Note that if three peaks appear in the luminance histogram as shown in Figure 8B, or if one peak appears in the luminance histogram as shown in Figure 8C, applying Otsu's binarization method directly will not accurately determine the area ratio of the whitened portion. Therefore, in this example, the luminance range used to determine the threshold value was adjusted. The procedure for adjusting the luminance range used to determine the threshold value is described below.

[0090] As shown in Figure 8A, when two peaks appear in the brightness histogram, Otsu's binarization method was applied as is. In Figure 8A, the peak on the right corresponds to the whitened part of the image, and the peak on the left corresponds to the other part. Specifically, the point where the degree of separation is maximum was set as the threshold.

[0091] In Examples 2, 5, and 6, the threshold value was set using the same procedure as in Example 1.

[0092] When three peaks (left, center, and right) appeared in the brightness histogram, as shown in Figure 8B, image processing software was used to confirm whether the center peak corresponded to the whitened portion of the image or the rest of the image. In Figure 8B, the center peak and the right peak corresponded to the whitened portion of the image, and the left peak corresponded to the rest of the image.

[0093] The curve showing the degree of separation in Figure 8B shows four convex portions, convex portion P1 to convex portion P4. Convex portion P1 is a convex portion located to the left of the peak top of the left peak. Convex portion P2 is a convex portion located between the peak top of the left peak and the peak top of the central peak. Convex portion P3 is a convex portion located between the peak top of the central peak and the peak top of the right peak. Convex portion P4 is a convex portion located to the right of the peak top of the right peak. The threshold value for determining the accurate area ratio of the whitened portion is between the peak top of the left peak and the peak top of the central peak. Therefore, the point where the degree of separation is maximum in this region (convex portion P2) was set as the threshold value.

[0094] In the fourth embodiment, the threshold value was set in the same manner as in the third embodiment.

[0095] When only one peak appeared in the brightness histogram, as shown in Figure 8C, image processing software was used to determine whether the peak corresponded to a whitened area or to a non-whitened area in the image. In Figure 8C, the peak corresponded to a non-whitened area in the image.

[0096] The curve showing the degree of resolution in FIG. 8C shows two convex portions, convex portion P1 and convex portion P2. Convex portion P1 is a convex portion located to the left of the peak top. Convex portion P2 is a peak located to the right of the peak top. The threshold value for determining the accurate area ratio of the whitened portion is located to the right of the peak top. Therefore, the point where the degree of resolution is maximum in this region (convex portion P2) was set as the threshold value.

[0097] In Comparative Example 3, the threshold value was set in the same manner as in Comparative Example 1.

[0098] The "area ratio of whitened portions" shown in Table 1 means the "ratio of the area of ​​whitened portions to the area of ​​the overlapping portions (S1 / S0)." The area ratio of whitened portions in the test pieces of Examples 1 to 6 was 19% to 81%. The area ratio of whitened portions tended to increase as the temperature of the welded surface increased.

[0099] The area ratios of the whitened areas were 6.4% and 12% in the test pieces of Comparative Examples 1 and 3. The reason why the area ratios of the whitened areas were not zero may be due to the influence of the edges of the test pieces reflecting the light when the peeled surface was photographed.

[0100] [8] Specular gloss of the whitened area After measuring the tensile strength, the 60-degree specular gloss of the peeled surface of the test piece with the remaining lead wire was measured using a glossmeter (Rhopoint Instruments, NOVO-CURVE, measurement spot 2mm x 2mm).

[0101] First, the 60-degree specular gloss was measured at the center of the peeled surface corresponding to overlapping portion 21. Then, the test piece was moved to measure the 60-degree specular gloss at multiple points. Figure 9 shows the measurement positions for the 60-degree specular gloss. As shown in Figure 9, the 60-degree specular gloss was measured at nine points on the peeled surface. The intervals between measurement points were 3 mm in the x direction, which is the width direction of the lead wire, and 1.8 mm in the y direction, which is the longitudinal direction of the lead wire.

[0102] FIG. 10 shows the measurement results of 60-degree specular gloss. In detail, FIGS. 10(a) to 10(h) show the measurement results of 60-degree specular gloss of the peeled surfaces of Example 1, Example 2, Comparative Example 1, Example 3, Example 4, Example 5, Example 6, and Comparative Example 3, respectively. FIG. 10(i) shows the measurement results of 60-degree specular gloss of a tab lead (reference example) including a lead wire and an adhesive protective film. The nine blocks included in each diagram in FIG. 10 correspond to the nine measurement points shown in FIG. 9. The shaded blocks indicate that part or all of the measurement spots overlapped with the whitened portion.

[0103] As shown in Figure 10, the 60-degree specular gloss of the whitened areas (hatched blocks) ranged from 2.4 to 29.5. The 60-degree specular gloss of other areas ranged from 36.8 to 73.7. The 60-degree specular gloss of the whitened areas was significantly lower than that of other areas. Furthermore, the 60-degree specular gloss of the measurement points where the entire measurement spot overlapped the whitened area ranged from 2.4 to 12.5.

[0104] A low measured value of the 60-degree specular gloss indicates good sealing at the position where the measurement was obtained. Therefore, the 60-degree specular gloss measured at one point, or preferably at multiple points, on the peeled surface can be used as an index for evaluating whether the seal portion of the exterior body has excellent sealing properties.

[0105] The results above indicate that the batteries having the seals formed under the conditions of the examples exhibit excellent sealing properties and leakage prevention. The measurement results of the area ratio of the whitened area and the 60-degree specular gloss are useful as indicators for easily evaluating the sealing properties of the exterior body in the area where the lead wires are located. [Industrial Applicability]

[0106] The technology of the present disclosure is useful for various batteries such as lithium secondary batteries. [Explanation of symbols]

[0107] 10 Battery element 11 Lead wire 12 Adhesive protective film 13 Exterior body 13a Periphery 15 test specimens 21 Overlap 30 Seal part 40 Tab Lead 42 Laminating film 100 batteries

Claims

1. an exterior body including a metal layer and a heat-sealable resin layer; a battery element disposed inside the exterior body; a metal lead wire connected to the battery element and extending to the outside of the exterior body; an adhesive protective film disposed on the periphery of the exterior body so as to be positioned between the inner surface of the exterior body and the lead wire; A battery comprising: a seal portion is formed by sandwiching the lead wire between the adhesive protective film and the exterior body, the battery includes an overlapping portion of the heat-sealable resin layer of the exterior body, the lead wire, and the adhesive protective film, when a force is applied to the seal portion to peel the exterior body from the lead wire, peeling occurs between the metal layer of the exterior body and the adhesive protective film, When the outer casing is peeled from the lead wire, the peeled surface on the lead wire side corresponding to the overlapping portion turns white, The ratio of the area of ​​the whitened portion to the area of ​​the overlapping portion is 15% or more. battery.

2. The 60-degree specular gloss of the whitened portion is 30 or less. The battery of claim 1 .

3. The 60-degree specular gloss of the whitened portion is 15 or less. The battery of claim 1 .

4. The ratio is 90% or less. The battery of claim 1 .

5. The battery element includes a solid electrolyte. The battery of claim 1 .

6. The battery element is an all-solid-state battery. The battery of claim 1 .

7. A method for evaluating a battery, comprising: The battery comprises: an exterior body including a metal layer and a heat-sealable resin layer; a battery element disposed inside the exterior body; a metal lead wire connected to the battery element and extending to the outside of the exterior body; an adhesive protective film disposed on the periphery of the exterior body so as to be positioned between the inner surface of the exterior body and the lead wire; Equipped with a seal portion is formed by sandwiching the lead wire between the adhesive protective film and the exterior body, the battery includes an overlapping portion of the heat-sealable resin layer of the exterior body, the lead wire, and the adhesive protective film, The evaluation method includes: taking a test piece including the seal portion from the battery; applying a force to the test piece to peel the outer casing from the lead wire; performing an optical measurement of the peeled surface on the lead wire side corresponding to the overlapping portion; Including, The optical measurement includes at least one selected from the group consisting of calculating a ratio of an area of ​​a whitened portion included in the peeled surface to an area of ​​the overlapping portion, and measuring a specular gloss of the peeled surface. Battery evaluation methods.

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