JP2020057463A - Battery exterior material, battery, and manufacturing method thereof - Google Patents

Abstract

To provide a battery exterior material for occupying a small space, a battery, and a manufacturing method thereof.SOLUTION: A battery exterior material (1) is formed of joined stainless foils (1a, 1b), and has a battery chamber (2) and a flange unit (3a) including a laser welded unit (5). The laser welded unit (5) is formed so that, in a cross section when cut along a plane perpendicular to an extending direction, a plate gap G near the laser welded unit (5) satisfies G≤1t and a welding width W satisfies 1t≤W≤10t (t: a thickness of a stainless steel foil on a side irradiated with laser).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a battery exterior material, a battery, and a method for producing the same.

  2. Description of the Related Art In recent years, the development of electric vehicles has been energetically performed, and the rapid spread of electric vehicles worldwide is expected. A storage battery (secondary battery) mounted on an electric vehicle is required to both save space and further extend its life. In addition, there is a similar demand for secondary batteries mounted on various types of portable electronic devices that have advanced functions.

  Lithium-ion batteries are typical secondary batteries. As an example of a lithium-ion battery, a battery having a battery container formed by joining two metal foils to each other and a battery element sealed in the container is known. In this type of battery, a metal foil having one or both surfaces laminated with a resin is generally used as a battery exterior material. The battery container is formed by bringing the two metal foils into contact with each other and thermocompression bonding (heat sealing) each other.

  Patent Literature 1 describes a laminated battery manufactured using a laminated film formed by attaching a resin to both surfaces of an aluminum foil. In addition, Patent Document 2 describes a technique of heat-sealing two laminated metal foils to each other, and then laser welding a part (end face) of the heat-sealed portion to improve a gas barrier property of a bonded portion. .

JP-A-2005-103291 JP 2013-184290 A JP 2004-71290 A

  However, the technique described in Patent Literature 1 requires a length from the battery chamber to the outer edge of the battery (so-called flange length) of, for example, about 10 mm to 20 mm. Such a flange length is necessary for suppressing performance deterioration of the battery over a long period of time, that is, for suppressing moisture permeation in the heat seal portion (for example, see Patent Document 3). As a result, the dead space created by the battery container is inevitably increased.

  Similarly, in the technique described in Patent Literature 2, the dead space generated by the heat seal portion and the laser weld portion also increases. Therefore, there is a limit to improving the space efficiency (space use efficiency) in the space in which the battery is mounted, that is, to reducing the space of the battery.

  One aspect of the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a battery exterior material, a battery, and a method for manufacturing the same, which occupy a small space.

  In order to solve the above problem, a battery exterior material according to one embodiment of the present invention includes a battery chamber that houses a battery element and is formed of a bonded stainless steel foil, and at least a part of a periphery of the battery chamber. And a welded portion formed by laser welding the stainless steel foils to each other at least in part, and the stainless steel foil on the side irradiated with the laser is Assuming that the stainless steel foil is the first stainless steel foil and the opposite stainless steel foil is a second stainless steel foil, the welded portion has a cross section taken along a plane perpendicular to the extending direction of the welded portion, and has a vicinity of the welded portion. The gap G between the first stainless steel foil and the second stainless steel foil satisfies the following expression (1), and is perpendicular to the extending direction of the welded portion on the surface of the first stainless steel foil. What Weld width W of direction is formed so as to satisfy the following formula (2).

G ≦ 1t (1)
1t ≦ W ≦ 10t (2)
Here, t is the thickness of the first stainless steel foil.

  In order to solve the above-described problem, a battery according to one embodiment of the present invention includes the battery exterior material and the battery element housed in the battery chamber.

  In order to solve the above problems, a method for manufacturing a battery exterior material according to one embodiment of the present invention provides a battery chamber for housing a battery element by stacking a first stainless steel foil and a second stainless steel foil on each other. A space forming step of forming an internal space, and laser welding of the first and second stainless steel foils by irradiating the first stainless steel foil with a laser in at least a part of the periphery of the battery chamber. And a laser welding step of forming a portion, in the laser welding step, the first stainless steel foil at a location where the laser is irradiated, in a cross section when cut along a plane perpendicular to the extending direction of the welded portion The gap G between the plate and the second stainless steel foil satisfies the following expression (1), and the gap G in the direction perpendicular to the stretching direction of the welded portion on the surface of the first stainless steel foil. Contact width W to form the welded portion so as to satisfy the following formula (2).

G ≦ 1t (1)
1t ≦ W ≦ 10t (2)
Here, t is the thickness of the first stainless steel foil.

  In order to solve the above problems, a method for manufacturing a battery according to one embodiment of the present invention further includes a step of housing the battery element in the battery chamber in the method for manufacturing a battery exterior material.

  According to one embodiment of the present invention, it is possible to provide a battery exterior material, a battery, and a method for manufacturing the same, which occupy a small space.

It is a perspective view showing roughly composition of a battery exterior material or a battery in one embodiment of the present invention. It is a figure for explaining a laser welding test performed in the state where two stainless steel foils were fixed with a plate holding jig and the gap between plates was adjustable. It is a schematic diagram which shows the mode observed about the cross section of the laser welding part using the optical microscope, Comprising: (a)-(c) is a figure which shows the result at the time of 10 micrometers, 80 micrometers, and 40 micrometers of board gaps, respectively. FIG. 4A is a perspective view illustrating a state in which a battery exterior material or a battery is manufactured in Embodiment 1 of the present invention, in which a laser welded portion is formed and a heat seal portion is not formed. 4B is a side view showing a state in which the heat-sealing sheet is set in the next step after the state shown in FIG. 4A, and FIG. 4C is a side view after the state shown in FIG. It is a perspective view which shows the battery exterior material or the battery after unnecessary parts were removed from the flange part after heat sealing. It is sectional drawing which expands and shows the laser welding part in one Embodiment of this invention. It is a figure showing an example of a laser welding device used for a manufacturing method of a battery exterior material in one embodiment of the present invention. It is a schematic diagram which shows the mode observed about the cross section of the laser welding part in a reference example using an optical microscope.

  Hereinafter, a battery packaging material having a small occupied space and a battery having the battery packaging material, in which a stainless steel foil is overlapped with each other and laser welded to form a battery chamber in one embodiment of the present invention, will be described. The following description is for the purpose of better understanding the gist of the present invention, and does not limit the present invention unless otherwise specified. Unless otherwise specified in this specification, “A to B” representing a numerical range means “A or more and B or less”. The shapes and dimensions (length, depth, width, etc.) of the components described in the drawings in the present application do not necessarily reflect the actual shapes and dimensions, and may be appropriately changed for clarification and simplification of the drawings. doing.

  Hereinafter, first, the configuration of the battery exterior material or the battery in one embodiment of the present invention will be schematically described, and then, the outline of the findings of the present invention found by the present inventors will be described. Then, the battery exterior material or the battery will be described in detail.

<Outline of battery exterior material (battery)>
FIG. 1 is a perspective view schematically showing a configuration of a battery exterior material 1 or a battery 100 having the battery exterior material 1 in the present embodiment.

  As shown in FIG. 1, the battery exterior material 1 in the present embodiment has a battery chamber 2 and a flange portion (joining portion) 3. A battery 100 is formed by accommodating a battery element in the battery chamber 2 and electrically connecting the battery element and the electrode unit 4 so that power can be supplied to the outside of the battery chamber 2. You.

  Battery room 2 is an internal space for housing battery elements. For example, the battery chamber 2 is formed by two stainless steel foils 1a and 1b each having a rectangular projection when viewed in a plan view and having the projections facing each other. Space. The battery chamber 2 is sealed by a flange 3 formed by joining the stainless steel foil 1a and the stainless steel foil 1b.

  The flange portion 3 is arranged over the entire periphery of the battery chamber 2. The flange portion 3 is formed of a laser welded portion 5 formed by laser-welding the stainless steel foil 1a and the stainless steel foil 1b to each other, and a heat-fused sheet formed between the two stainless steel foils 1a and 1b. And a heat seal portion 6 formed by attachment. The end of the laser weld 5 is in close contact with or contained in the heat seal 6. The details of the laser weld 5 will be described later. In addition, before the battery exterior material 1 (battery 100) shown in FIG. 1 is used as a product, an unnecessary portion of the flange portion 3 (specifically, a peripheral portion of the laser welded portion 5) is deleted.

  The heat seal portion 6 is a part of the flange portion 3 and is a portion formed by heat fusion of a heat fusion sheet. Further, the heat seal portion 6 is a portion of the joining portion of the stainless steel foils 1a and 1b that sandwiches the electrode portion 4. The heat sealing portion 6 is formed, for example, by heat sealing a heat sealing sheet in which the electrode portion 4 is inserted into a slit portion of the heat sealing sheet. In addition, the specific aspect of the heat seal part 6 is not specifically limited.

  The electrode portion 4 is sandwiched by the flange portion 3, more specifically, by the heat seal portion 6. The electrode part 4 is a member for electrically connecting a battery element in the battery chamber 2 and the outside of the battery chamber 2.

<Knowledge of the present invention>
Since the stainless steel foils 1a and 1b (stainless steel thin plate) have higher strength and rigidity than aluminum, they can be suitably used as a material of a battery exterior material. On the other hand, stainless steel has a higher specific gravity than aluminum. Therefore, the thickness of the stainless steel foils 1a and 1b should be as thin as possible within a range having sufficient physical properties (for example, strength) as the battery exterior material 1 for reasons such as weight reduction, space saving, and cost reduction. Is required. For example, the stainless steel foils 1a and 1b may have a thickness of about 100 μm or less in practical use.

  In applying the stainless steel foils 1a and 1b to the battery exterior material, if the laser welded portion 5 can be formed on the flange portion 3 as described above, the flange length can be reduced. When laser welding is performed, the stainless steel foils 1a and 1b do not require surface coating with a laminate resin.

  Here, in the stainless steel foils 1a and 1b that have been subjected to press working or the like to form the above-described convex portions, wrinkles are generated around the convex portions (flanges). That is, the flange after the formation of the convex portion is not flat, but is wavy or twisted. Further, since the stainless steel foils 1a and 1b are thin, wrinkles are very likely to occur and are greatly affected by thermal distortion.

  It is not easy to form a laser-welded portion 5 that secures airtightness by overlapping such flanges of the stainless steel foils 1a and 1b and performing laser welding. Moreover, it has been very difficult to stably form such a laser weld around the battery chamber 2 (over a certain long distance).

  The present inventors have conducted intensive studies on conditions required for stably forming a laser welded portion when manufacturing a battery exterior material by laser welding thin stainless steel foils to each other. As a result, the present inventors have arrived at the present invention with the following ideas and findings.

  During laser welding, a molten metal formed by melting the stainless steel foil on the side irradiated with the laser fills the gap between the stainless steel foils. For this reason, if the gap between the plates is too wide, problems such as burn-through tend to occur. Here, when the stainless steel foils 1a and 1b each having a thickness of about 100 μm or less are laser-welded, wrinkles are likely to occur due to thermal strain, and the wrinkles increase the gap between the plates.

  Since stainless steel has a lower thermal conductivity than iron and aluminum, local temperature changes are likely to occur, and therefore wrinkles due to thermal strain are likely to occur. In particular, when an austenitic stainless steel such as SUS304 is used, for example, since the coefficient of thermal expansion is relatively large, thermal distortion when heated by a laser can be large.

  The present inventors conceived as follows. That is, if the width of a welded portion formed by laser welding (hereinafter, sometimes referred to as a weld width) is large, the amount of molten metal increases, and it becomes easy to prevent problems such as burn-through. On the other hand, if the welding width is too wide, wrinkles due to thermal strain are likely to be generated in the vicinity of the welded portion, which may be a factor to locally increase the inter-plate gap. In laser welding of the thin stainless steel foils 1a and 1b as described above, in order to prevent burn-through and perforation during welding, not only control the gap between the plates but also appropriately manage the welding width. I thought it was important.

(Verification test)
A verification test performed by the present inventors based on the above idea will be described below with reference to FIGS. FIG. 2 is a diagram for describing a laser welding test performed in a state where two stainless steel foils are fixed with a plate holding jig and the gap between the plates is adjustable. The verification test was performed using a thin stainless steel plate (stainless-foil without forming the convex portion) to facilitate interpretation of the result.

  As shown in FIG. 2, a lower plate holding jig 12b, a stainless steel foil 10b, a shim plate 13, a stainless steel foil 10a, and an upper plate holding jig 12a are placed on the support base 11 in this order to perform a verification test. went. The shim plate 13 is sandwiched between the stainless steel foils 10a and 10b, and the distance between the stainless steel foils 10a and 10b (the gap G1 between the plates) is adjusted by changing the thickness of the shim plate 13. can do. In this case, the gap G1 between the plates is substantially the same as the thickness of the shim plate 13.

  As the stainless steel foil 10a and the stainless steel foil 10b, a SUS304 BA material (a material having a surface finish having gloss close to a mirror surface) was used.

  A groove 14a for irradiating the stainless steel foil 10a with the laser beam LB1 is formed in the upper plate holding jig 12a. A groove 14b is formed in the lower plate holding jig 12b at a position corresponding to the groove 14a. The lower groove 14b prevents the lower plate holding jig 12b from melting due to heat transfer of the irradiation heat of the laser beam LB1. Note that the grooves 14a and 14b are actually formed continuously from the near side to the far side in the direction penetrating the paper surface (when viewed in a plan view as shown in FIG. 2, they are rectangular openings).

(Test 1: Conditions between sheet gaps)
Using the stainless steel foil 10a and the stainless steel foil 10b having a thickness of 40 μm, the thickness of the shim plate 13 (that is, the gap G1 between the plates) is changed from 10 μm to 80 μm, and the stainless steel foil 10a is inserted through the groove 14a. Was irradiated with a laser beam LB1 to perform laser welding. A fiber laser welder was used as the laser welder, and Ar gas was flowed at 20 L / min to obtain a shield gas. The laser beam LB1 had a focal position on the surface of the stainless steel foil 10a, a laser spot diameter of φ (diameter) of 100 μm, and a laser output of 150 W. The welding speed (laser sweep speed) was 12.5 m / min.

  The results of the above test will be described with reference to FIG. FIG. 3 is a schematic diagram illustrating a state in which the above-described cross section is observed using an optical microscope with respect to an observation sample that has been processed so that the cross section of the laser welded portion can be observed. FIGS. 3A to 3C are diagrams showing the results when the gap G1 between the plates is 10 μm, 80 μm, and 40 μm, respectively. Here, the cross section shown in FIG. 3 is a cross section taken along a plane perpendicular to the direction (extending direction) in which the laser welded portion extends.

  As shown in FIG. 3A, as a result of the test with the inter-plate gap G1 set to 10 μm, a laser welded portion 15a having a uniform shape was formed. Here, the width of the laser welded portion measured on the surface S1 on the laser irradiation side of the stainless steel foil 10a in the above section is defined as a welding width W1. The welding width W1 of the laser weld 15a was about 190 μm.

  On the other hand, as shown in FIG. 3 (b), as a result of the test in which the gap G1 between the plates was 80 μm, the stainless steel foil 10a was melted down by laser welding, and a laser welded portion could not be formed.

  Then, the present inventors adjusted the inter-plate gap G1 and repeated the test, and as a result, it was found that when the inter-plate gap G1 was 40 μm or less, no burn-through occurred and a laser welded portion could be formed. As shown in FIG. 3C, the test was performed with the gap G1 between the plates set to 40 μm. As a result, a laser welded portion 15b was formed by laser welding. It is presumed that the laser weld 15b is formed roughly as follows. That is, the metal (molten metal) melted by the laser beam LB1 contacts the stainless steel foil 10b by hanging down by gravity. Heat generated by the irradiation of the laser beam LB1 propagates through the molten metal to the stainless steel foil 10b, and the stainless steel foil 10a and the stainless steel foil 10b are fused. Thereafter, the heat-affected zone is rapidly cooled and solidified and contracted, thereby forming the laser welded portion 15b. In the laser welded portion 15b, the width of the heat-affected zone in the stainless steel foil 10a is larger than the width of the heat-affected zone in the stainless steel foil 10b.

  In the cross section shown in FIG. 3C, the welding width W1 of the laser welded portion 15b is defined as follows. That is, two points in the cross section between the surface S1 of the stainless steel foil 10a and the laser welded portion 15b can be specified. One of these two points is a boundary point 16a, and the other is a boundary point 16b. The welding width W1 of the laser weld 15b was expressed as the distance between the boundary point 16a and the boundary point 16b, and was about 390 μm.

Further, the same test was performed by changing the thickness of the stainless steel foil to 10 μm to 100 μm. As a result, it has been found that the inter-plate gap G1 needs to satisfy the relationship of the following expression (3), where t is the plate thickness of the stainless steel foil;
G1 ≦ 1t (3)
Here, when the thicknesses of the stainless steel foil 10a and the stainless steel foil 10b are different from each other, the plate thickness t is the thickness of the stainless steel foil 10a. This is because the thickness of the stainless steel foil on the side receiving the laser irradiation is important.

  By satisfying the relationship of the above equation (3), it is possible to increase the stability of the phenomenon that the molten metal hangs downward and contacts the lower plate during laser welding.

(Test 2: Conditions for welding width)
Here, as described above, when manufacturing the battery packaging material 1, the gap between the plates may fluctuate due to the wrinkles existing in the flange. Even in such a case, it is required that the laser weld be formed stably. Then, the present inventors fixed the gap G1 between the plates to 1t which is the strictest condition based on the relationship of the above formula (3), changed the plate thickness t from 20 μm to 100 μm, and changed the welding width. The test was performed by changing W1.

  Adjustment of the welding width W1 was performed as follows. That is, the spot diameter of the laser beam LB1 was changed to φ30 μm, 100 μm, and 200 μm, and the laser output was adjusted to 300 W or less and the welding speed was varied to 12.5 m / min or less. Other conditions are the same as those in Test 1 described above.

  Table 1 summarizes the test results. In Table 1, the welding width W1 is represented by a multiple of the plate thickness t. For example, in the example in which the plate thickness t in Table 1 is 20 μm, the test was performed by changing the welding width W1 in the range of 10 μm to 400 μm, that is, 0.5 t to 20 t.

  In Table 1 above, conditions where holes or burn-through occurred in the stainless steel foil 10a, which is the plate (upper plate) on the laser irradiation side, are marked with a cross. In addition, the condition that a laser welded portion could be formed without opening a hole in the stainless steel foil 10a is marked with a circle.

  In any condition of the plate thickness t, the welding width W1 was inappropriate when the welding width W exceeded 10 t. This is considered to be due to the fact that deep wrinkles were generated due to the thermal strain, so that the gap between the plates became too large and the stainless steel foil 10a was perforated. Also, the case where the welding width W1 was less than 1 t was unsuitable. This is presumably because the laser beam was locally irradiated, so that the molten portion became too narrow, so that a molten metal for filling the interplate gap 1t could not be generated, and a hole was opened in the stainless steel foil 10a.

Therefore, it has been found that the welding width W1 needs to satisfy the relationship of the following equation (4);
1t ≦ W1 ≦ 10t (4).

  As described above, the present inventors satisfy the condition of the above equation (3) (the gap G1 between the plates is 1 t or less) and the condition of the above equation (4) so that an appropriate amount of melting can be achieved during laser welding. It has been found that the gap G1 between the plates can be filled with metal, and the laser weld can be formed stably.

<Detailed description of battery exterior material 1>
The battery exterior material 1 of the present embodiment conceived by the inventors based on the above findings will be described below in detail with reference to FIGS. 4 and 5. The battery package 1 of the present embodiment is manufactured by performing laser welding by a method based on the above knowledge (to be described in detail later as a method of manufacturing a battery package).

  4A and 4B show a manufacturing process of the battery outer packaging material 1 or the battery 100 according to the present embodiment. FIG. 4A shows a state after the laser welded part 5 is formed and before the heat seal part 6 is formed. FIG.

  As shown in FIG. 4A, the battery outer casing 1 has a laser weld 5 on the flange 3. The laser welding part 5 irradiates a laser beam to the flange of one of the stainless steel foils 1a in a state where the two stainless steel foils 1a and 1b on which the convex parts are formed are overlapped so that the convex parts face in different directions. Is formed by laser welding the overlapped portion.

(Stainless steel foil)
The stainless steel foils 1a and 1b may be ferritic stainless steel or other stainless steel types. The stainless steel foils 1a and 1b are preferably made of austenitic stainless steel such as SUS304 from the viewpoint of strength and formability.

  The thickness of the stainless steel foils 1a and 1b is preferably 20 μm or more, more preferably 30 μm or more, and further preferably 40 μm or more, from the viewpoint of the strength. Further, the thickness of the stainless steel foils 1a and 1b is preferably 100 μm or less, more preferably 70 μm or less, and still more preferably 50 μm or less, from the viewpoint of weight reduction and welding stability. For example, the thickness of the stainless steel foils 1a and 1b is preferably 20 μm or more and 100 μm or less.

  More specifically, the stainless steel foils 1a and 1b are austenitic stainless steels having a tensile strength of 700 MPa or more and an elongation of 45% or more from the viewpoints of strength, chemical stability, moldability and the like. Preferably, there is.

  The tensile strength of the stainless steel foils 1a and 1b is preferably 700 MPa or more, more preferably 750 MPa or more, from the viewpoint of the above strength. In addition, the upper limit of the tensile strength of the stainless steel foils 1a and 1b can be appropriately determined from the viewpoint of feasibility such as availability, and is, for example, preferably 900 MPa or less, and more preferably 800 MPa or less. More preferred. The tensile strength of the stainless steel foils 1a and 1b can be measured by a tensile test, and can be adjusted by, for example, annealing or temper rolling.

  The elongation of the stainless steel foils 1a and 1b is preferably 45% or more, more preferably 55% or more, from the viewpoint of the moldability. The upper limit of the elongation of the stainless steel foils 1a and 1b can be appropriately determined from the viewpoint of feasibility such as availability, and is preferably, for example, 75% or less, and more preferably 70% or less. . The elongation of the stainless steel foils 1a and 1b can be measured by a tensile test, and can be increased by, for example, rolling and then annealing in an atmosphere of a rare gas or a non-oxidizing gas (such as a hydrogen gas).

  Moreover, it is preferable that the stainless steel foils 1a and 1b do not have a resin layer such as a laminate on the surface from the viewpoint of welding stability.

  The convex portions of the stainless steel foils 1a and 1b can be formed by a normal processing method for forming the convex portions, such as a drawing process or an overhanging process. From the viewpoint of suppressing the occurrence of wrinkles in the flange, the projection is preferably formed by overhanging.

  The stainless steel foil 1a and the stainless steel foil 1b may be made of the same material or different materials. For example, the plate thicknesses of the stainless steel foil 1a and the stainless steel foil 1b may be the same or different from each other.

(Electrode part)
The electrode part 4 may be a part of the battery element or may be included in the configuration of the battery exterior material 1. The position and number of the electrode units 4 are not particularly limited. The electrode portion 4 can be appropriately selected from members usable for electrodes of the battery. For example, examples of the shape of the electrode unit 4 include a plate shape, a columnar shape, and a linear shape. Examples of the material of the electrode unit 4 include aluminum, copper, and carbon.

(Battery element and battery)
FIG. 4B is a side view showing a state where the heat-sealing sheet is set in the next step after the state shown in FIG. As shown in FIG. 4B, the battery element 20 is housed in the battery chamber 2. The battery element 20 is configured by a combination of known members constituting a battery, is insulated by a film or the like, and is housed in the battery chamber 2. Examples of the components of the battery element 20 include a positive electrode, a negative electrode, a separator, and an electrolyte, and examples of the electrolyte include an electrolytic solution, a solid electrolyte, and a gel electrolyte. These are combined as appropriate according to the type of the battery element 20 to form the battery element 20. The type of the battery 100 configured by including the battery element 20 may be a primary battery or a secondary battery. Examples of the secondary battery include a lithium ion battery, a lithium polymer battery, a nickel metal hydride battery, and a nickel cadmium battery.

(Heat seal part)
As shown in FIGS. 4A and 4B, the heat-sealing sheet 7 has a bent portion and includes a slit opening along the fold line of the bent portion. By heat-sealing the heat-sealing sheet 7 with the part 4 inserted, the heat-sealing part 6 (see FIG. 1) can be formed.

  The heat sealing sheet 7 is composed of a continuous phase of a thermoplastic resin. The thermoplastic resin may be any thermoplastic resin that can be used as a resin material of a heat sealing sheet for heat sealing, and examples include polyolefins such as polyethylene and polypropylene, and polyethylene terephthalate.

  The thickness of the heat-sealing sheet 7 may be within a range in which heat sealing is possible, and may be, for example, 50 to 150 μm.

  The heat-sealing sheet 7 may further include an aggregate for reinforcing the heat-sealing sheet from the viewpoint of maintaining the shape of the heat-sealing sheet. Examples of the aggregate include a filler and a non-meltable sheet. Examples of such fillers include flexible short fibers. The non-fusible sheet is a sheet that remains without being melted by heat sealing of the heat-sealing sheet, and examples thereof include nonwoven fabrics and woven fabrics.

  The heat-sealing sheet having the non-fusible sheet may be a sheet obtained by laminating the heat-fusing sheet and the non-fusible sheet, or may be a commercially available product. Examples of the commercially available products include thermal fusion films PPa-F (72), PPa-F (100), PPa-N (72), PPa-N (100), and PPa-Y manufactured by Dai Nippon Printing Co., Ltd. Is included.

  The state of the heat-sealing sheet 7 in the heat seal portion 6 can be confirmed by observing the cross section of the heat seal portion 6 or by ultrasonic waves.

  The bent portion of the heat-sealed sheet 7 in the heat-sealed portion 6 is located at a position connected to the laser-welded portion 5 in the heat-sealed portion 6. That is, the heat-fused sheet 7 is arranged such that the ridge line formed by bending is located at the back of the flange portion 3. In addition, the heat sealing sheet 7 may be arranged so that the ridge line is directed to the direction of the outside of the battery exterior material 1.

(Laser weld)
The laser welded portion 5 is a portion formed by irradiating a laser to the stainless steel foil (first stainless steel foil) 1a and laser welding the stainless steel foil 1a and the stainless steel foil (second stainless steel foil) 1b. In this embodiment, the laser weld 5 is formed along two long sides and one short side of the stainless steel foils 1a and 1b. The laser welded portion 5 is formed on the long side from one short side of the stainless steel foil 1a to the other short side that is not welded to a position having an appropriate distance from the other short side. The interval on the other short side is substantially the same as the seal length of the heat seal portion 6.

  FIG. 4C is a perspective view showing the battery exterior material 1 or the battery 100 after removing unnecessary portions of the flange portion 3 after heat sealing in a process after the state shown in FIG. 4B. It is. As shown in FIG. 4 (c), after forming the laser welding portion 5 and the heat sealing portion 6, by removing unnecessary portions of the flange portion 3, the battery exterior material 1 having the flange portion 3a (the battery 100) are obtained.

  The protruding length (the distance from the side wall of the battery chamber 2 to the side edges of the stainless steel foils 1a and 1b) of the portion having the laser weld 5 in the flange 3a is in a range where the laser weld 5 can be formed. Thus, it is only necessary that the laser chamber 5 has a range in which the battery chamber 2 can be hermetically and liquid-tightly sealed. The smaller the protruding length, the smaller the battery occupation material 1 (battery 100) occupying space. The protrusion length is preferably 6 mm or less, more preferably 5 mm or less, and even more preferably 4 mm or less. The protrusion length is preferably 1 mm or more from the viewpoint of workability when forming the laser welded portion 5.

  The laser weld 5 will be described in more detail with reference to FIG. FIG. 5 is an enlarged cross-sectional view showing a cross section taken along a plane perpendicular to the direction in which the laser weld 5 extends (the direction in which the laser weld 5 extends).

  As shown in FIG. 5, in the cross section, two points of the boundary between the surface S11 of the stainless steel foil (first stainless steel foil) 1a on the side irradiated with the laser and the laser welded portion 5 can be specified. Of these two points, a point closer to the battery chamber 2 is defined as a boundary point 5a, and the other is defined as a boundary point 5b. The distance between the boundary point 5a and the boundary point 5b is defined as the welding width W of the laser welded portion 5.

  Here, in the cross section, as the inter-plate gap between the stainless steel foil 1a and the stainless steel foil 1b in the vicinity of the laser welded portion 5, there is an inter-plate gap G11 on the battery chamber 2 side and an inter-plate gap G12 on the other side. . The gaps G11 and G12 between the plates correspond to the gaps between the stainless steel foils 1a and 1b when performing the laser welding. In the present specification, the inter-plate gaps G11 and G12 are specified as the inter-plate gap G before laser welding in the laser welded portion 5. This is because the gap between the plates of the stainless steel foils 1a and 1b at the time of performing the laser welding can no longer be directly known after performing the laser welding. When the inter-plate gap G11 and the inter-plate gap G12 are different, the larger value is adopted as the inter-plate gap G before laser welding.

  The inter-plate gap in the vicinity of the laser weld 5 is, for example, an inter-plate gap at a position 40 to 80 μm away from the laser weld 5. The inter-plate gaps G11 and G12 may be measured directly by observing the cross section, or from a measurement value obtained by measuring the vicinity of the laser welded portion 5 using a non-contact optical thickness gauge. It may be measured by reducing the total thickness of the stainless steel foils 1a and 1b. The inter-plate gaps G11 and G12 may be an average value obtained by averaging the results obtained by measuring a plurality of locations within a range of 40 to 80 μm from the laser welded portion 5. Alternatively, the interplate gaps G11 and G12 may adopt the maximum value among the measurement results within the above range.

(Gap between plates and welding width)
The battery exterior material 1 of the present embodiment has a laser weld 5 satisfying the following formulas (1) and (2) in the above cross section;
G ≦ 1t (1)
1t ≦ W ≦ 10t (2)
In the above equation,
G: A value based on the inter-plate gaps G11 and G12, and the indirectly specified inter-plate gap before laser welding t: the thickness W of the stainless steel foil 1a: the welding width.

  The laser welding portion 5 as described above can be formed using, for example, a laser welding device that can perform laser welding so as to reduce the gap G between the plates while controlling the welding width W. An example of such a laser welding apparatus will be described later as a method of manufacturing the battery outer package 1. Thereby, the protruding length (the distance from the side wall of the battery chamber 2 to the side edges of the stainless steel foils 1a and 1b) of the portion having the laser welded portion 5 in the flange portion 3a of the battery exterior material 1 (battery 100) is set to 6 mm or less. can do.

(Weld position)
Further, assuming that the side wall of the protrusion forming the battery chamber 2 in the stainless steel foil 1 a is the side wall 21, the laser welded portion 5 preferably further satisfies the following condition as a positional relationship from the side wall 21. This will be described below with reference to FIG.

  As shown in FIG. 5, a portion of the stainless steel foil 1 a forming a part of the battery chamber 2 around the protrusion 1 a 1 is defined as a peripheral portion 1 a 2, and the stainless steel foil 1 a has a curved line extending from the peripheral portion 1 a 2 toward the side wall 21. The portion that is drawn and rises is the rise portion 22. The starting end of the rising portion 22 on the surface S11 of the stainless steel foil 1a farther from the battery chamber 2 is defined as an R stop portion (R stop point) 23.

  In the laser welded portion 5, in the cross section shown in FIG. 5, it is preferable that the distance D between the center position of the welding width W and the R stop portion 23 is in the range of 1 mm or more and 5 mm or less. The reason is as follows. That is, after the laser welding, the flange portion 3 is cut short so that the space-saving and lightweight battery exterior material 1 is obtained. Therefore, the laser welding is preferably performed at a position as close as possible to the side wall portion 21. The vicinity of the side wall 21 has high rigidity due to the shape effect and has relatively few wrinkles (wavy) due to processing, so that it is suitable for laser welding. On the other hand, at the time of laser welding, it is necessary to arrange a jig near the side wall 21. Therefore, the distance D is preferably 1 mm or more from the R stop 23. Further, as the distance D becomes farther from the side wall portion 21, the gap G between the plates is inevitably increased due to the influence of the wrinkles of the flange, and it becomes difficult to satisfy the above condition (1). Therefore, when laser welding is performed such that the distance D is about 6 mm from the R stop portion 23, the stainless steel foil 1a may be burnt off.

  Note that at least a part of the laser weld 5 may be within the range of the distance D. In the present embodiment, when the battery exterior material 1 is viewed from above and viewed from above, the distance between the side walls of the four corners of the battery chamber 2 (projection 1a1) and the laser welded portion 5 is outside the above range. It may be. In another embodiment, even if the battery chamber has various shapes, the distance D between the center position of the welding width W and the R stop portion 23 is within the above range for at least a part of the laser welded portion 5. It just needs to be.

(shape)
Further, the laser welded portion 5 included in the battery exterior material 1 of the present embodiment has the following features on one side.

  The surface of the stainless steel foil 1b that is farther from the surface S11 of the stainless steel foil 1a is referred to as a surface S12.

  As shown in FIG. 5, the laser weld 5 is formed so as to be recessed from the surfaces S11 and S12 toward the center of the laser weld 5 in both the stainless steel foil 1a and the stainless steel foil 1b. In other words, the front bead and the back bead of the laser weld 5 are formed so as to be depressed toward the center of the laser weld 5. It is considered that this is because solidification shrinkage occurred due to rapid cooling immediately after laser welding. In this specification, such a laser welded portion 5 is referred to as a thin portion 25.

  In the battery package 1 of the present embodiment, at least a part of the laser weld 5 is the thin portion 25. Such a thin portion 25 can be formed by laser welding stainless steel foils having extremely small thicknesses under appropriate conditions. The thin portion 25 is a dense welded portion formed by laser welding, and has high airtightness and high strength. Therefore, the airtightness and strength of the laser weld 5 are improved.

(Other configurations)
Battery exterior material 1 may have a configuration other than the configuration described above as long as the effects of the present embodiment can be obtained. Examples of the other configuration include a safety valve in addition to the electrode unit 4 described above.

  In addition, the battery exterior material 1 or the battery 100 includes a portion where the laser welded portion 5 is formed and a portion around the portion, the surface of the stainless steel foil 1a facing the stainless steel foil 1b, and the surface of the stainless steel foil 1b. There is no resin layer on the surface facing the stainless steel foil 1a. The stainless steel foils 1a and 1b do not have a resin layer on the surface of the flange portion where the laser welding portion 5 is formed, and on the other hand, have a resin layer on the surface other than where the laser welding portion 5 is formed. It may have a coating layer such as a layer.

<Production method of battery exterior material>
A method for manufacturing the battery exterior material 1 in the present embodiment will be described below with reference to FIG. FIG. 6 is a diagram illustrating an example of a laser welding apparatus used in the method for manufacturing the battery exterior material 1 according to the present embodiment.

  First, the flanges of the stainless steel foils 1a and 1b on which the convex portions are formed by press working or the like are overlapped to form an internal space that becomes the battery chamber 2 for accommodating the battery element 20 (space forming step).

  Next, the stainless steel foil 1a and the stainless steel foil 1b are laser-welded to each other by irradiating a laser to the flange of the stainless steel foil 1a. Thereby, the laser welding part 5 is formed (laser welding process). In the manufacturing method according to the present embodiment, the laser welding portion 5 is formed by performing laser welding not by a plurality of laser irradiations but by one laser irradiation.

  In order to manufacture the battery exterior material 1 (battery 100), the laser welded portions 5 having a length of, for example, about 100 mm or more are hermetically sealed by laser welding stainless steel foils having a thickness of about 100 μm or less. It is required to form continuously. Such a laser welded portion 5 can be formed using, for example, a laser welding device as shown in FIG. 6 based on the above-described findings found by the present inventors. In addition, what is necessary is just to be able to perform laser welding so that conditions of the above-mentioned board gap and welding width may be satisfied, and the specific mode of a laser welding device is not specifically limited.

  As shown in FIG. 6, the laser welding apparatus 40 according to the present embodiment mounts a lower plate holding jig 42 on a support 41 and uses a lower plate holding jig 42 and plate holding rollers 43 and 44 to form a stainless steel plate. The laser beam LB2 is irradiated while the flanges of the foils 1a and 1b are sandwiched. Here, the battery element 20 is accommodated in the battery chamber 2 formed by the stainless steel foils 1a and 1b.

  The height of the lower plate holding jig 42 is the same as the forming height of the stainless steel foil 1b. When the stainless steel foil 1b is placed on the support 41, the flange is placed on the lower plate holding jig 42. You. The plate pressing roller 43 is arranged near the side wall 21. The flanges of the stainless steel foils 1a and 1b are pressed and fixed by the plate holding roller 43 and the lower plate holding jig 42.

  Further, the plate holding roller 44 is disposed on the side close to the outer edges of the stainless steel foils 1a and 1b so as to be separated from the plate holding roller 43 so as to form an optical path for irradiating the laser beam LB2 onto the stainless steel foil 1a. I have.

  The plate pressing rollers 43 and 44 are arranged so as to be in contact with the stainless steel foil 1a, and are rotatably supported by support members 45 and 46, respectively. Elastic bodies 47 are connected to the support members 45 and 46, respectively. The elastic body 47 is formed of, for example, a spring, rubber, or the like. The elastic body 47 applies a force to the plate pressing rollers 43 and 44 via the supporting members 45 and 46 so as to press the stainless steel foil 1a.

  Alternatively, a hydraulic cylinder or a pneumatic cylinder (not shown) may be connected to each of the support members 45 and 46 instead of or in combination with the elastic body 47. In this case, the hydraulic cylinder or the pneumatic cylinder applies a force to the plate pressing rollers 43 and 44 via the support members 45 and 46 so as to press the stainless steel foil 1a.

  The flanges of the stainless steel foils 1a and 1b are pressed and fixed by the plate holding rollers 43 and 44 and the lower plate holding jig 42. Thereby, a pressing force can be exerted on the flanges of the stainless steel foils 1a and 1b.

  In the cross section shown in FIG. 6, the distance X between the position where the plate pressing roller 43 contacts the stainless steel foil 1a and the position where the plate pressing roller 44 contacts the stainless steel foil 1a (inter-plate pressing distance) is appropriately set. May be, for example, 2.5 mm.

  The pressing force of the plate pressing roller 43 and the plate pressing roller 44 may be adjusted by changing the amount of pressing by the elastic body 47 and the spring constant. Alternatively, when a hydraulic cylinder or a pneumatic cylinder is provided, the pressing force by the hydraulic cylinder or the pneumatic cylinder may be adjusted using a pressure adjusting valve. Thereby, the pressing force changes according to the case where the convex portions of the stainless steel foils 1a and 1b are formed by draw forming and the case where they are formed by overhang forming (depending on the amount and depth of wrinkles). Thus, the inter-plate gap G can be adjusted.

  The laser welding process forms the laser welded portion 5 along three sides (a pair of long sides and a short side at one end) of the stainless steel foils 1a and 1b. Thereby, three sides (a pair of long sides and a short side on one end side) of the battery chamber 2 are liquid-tightly and air-tightly sealed by the laser weld 5.

  In the laser welding process of the present embodiment, three sides of the stainless steel foils 1a and 1b are welded, but a part to be the heat seal part 6 is left on the electrode part 4 side of the stainless steel foils 1a and 1b. Therefore, the two ends (weld ends) of the laser weld 5 do not reach the edges of the stainless steel foils 1a and 1b.

  Thereafter, the heat-sealing sheet 7 bent at the bending portion is sandwiched between the remaining portions of the peripheral portions of the stainless steel foils 1a and 1b (preparation step before fusion).

  Next, the remaining portion of the peripheral portion is heated to cause the heat-sealing sheet 7 to be heat-sealed and heat-sealed (sealing step). In the sealing step, a sealing method capable of heat-sealing the heat-sealing sheet 7 sandwiched between the stainless steel foils 1a and 1b can be used. Examples of the sealing method include a thermocompression bonding method in which pressing is performed by a pressing element that generates ultrasonic vibration or a pressing element that is heated. By the above sealing step, the heat-sealing sheet 7 is melted, and the resin component adheres tightly so as to wrap the end of the laser welded portion 5. Thus, the heat sealing portion 6 is formed, and the battery chamber 2 is completely liquid-tightly and air-tightly sealed.

  The above manufacturing method may further include other steps other than the above steps as long as the effects of the present embodiment can be obtained. For example, the above-described manufacturing method may further include a step of sandwiching the electrode portion 4 in the remaining portion of the peripheral portion that becomes the heat seal portion 6 (electrode sandwiching step).

  The electrode clamping step may be performed before the sealing step. For example, the electrode sandwiching step may be performed simultaneously with the space forming step, the laser welding step, or the preparation step before fusion. Further, it may be performed between the laser welding step and the pre-fusion preparation step or may be performed after the pre-fusion preparation step.

  More specifically, the electrode portion 4 may be arranged at the end of the stainless steel foils 1a and 1b at the peripheral portion of the stainless steel foil 1a and 1b while the battery element 20 is accommodated in the convex portion during the space forming step. Further, after the laser welded portion 5 is formed, the electrode portion 4 is inserted into an appropriate position of the battery element 20 housed in the battery chamber 2 in advance, so that the other end portion at the peripheral edge portion of the stainless steel foils 1a and 1b is formed. It may be arranged. Alternatively, the electrode section 4 is inserted into the battery chamber 2 together with the arrangement of the heat sealing sheet 7 in a state of being inserted through the slit section of the heat sealing sheet 7, and the other end portions at the peripheral edges of the stainless steel foils 1 a and 1 b. May be arranged. Alternatively, the electrode portion 4 is inserted into the battery chamber 2 from the outside of the battery chamber 2 through the slit portion of the heat-sealing sheet 7 disposed at the other end of the peripheral edge of the stainless steel foils 1a and 1b. The foils 1a and 1b may be arranged at the other end in the peripheral portion.

  As described above, the electrode sandwiching step is performed such that the electrode portion 4 is inserted through the slit portion when the heat sealing sheet 7 has the slit portion. By inserting the electrode portion 4 through the slit portion, the electrode portion 4 is easily arranged at a desired position in the short direction of the battery chamber 2, and is unlikely to be displaced in the short direction.

As described above, the manufacturing method of the battery exterior material in the present embodiment includes the above-described laser welding step. In the laser welding step, the laser beam is cut in a cross section taken along a plane perpendicular to the stretching direction of the laser welding portion 5. The inter-plate gap G between the stainless steel foil 1a and the stainless steel foil 1b at the location where the LB2 is irradiated satisfies the following expression (1), and the direction perpendicular to the stretching direction of the laser welded portion 5 on the surface of the stainless steel foil 1a. To form the laser welded portion 5 so that the welding width W of the following satisfies the following expression (2);
G ≦ 1t (1)
1t ≦ W ≦ 10t (2)
Here, t is the thickness of the stainless steel foil 1a.

  Thus, by laser welding stainless steel foils having a thickness of about 100 μm or less, a laser welded portion 5 having a length of about 100 mm or more can be continuously formed so as to ensure airtightness. After forming such a laser welded portion 5, an unnecessary portion of the flange portion 3 (specifically, a peripheral portion of the laser welded portion 5) is deleted, and the battery exterior material 1 occupying a small space can be manufactured. (See (c) of FIG. 4).

  Further, in the method for manufacturing a battery exterior material according to the present embodiment, the laser welding portion 5 can be formed by performing laser welding not by a plurality of laser irradiations but by one laser irradiation. Therefore, manufacturing efficiency can be improved.

  In the laser welding step, at least a part of the laser welded portion 5 is formed such that the distance between the center position of the welding width W and the R stop portion 23 is in the range of 1 mm or more and 5 mm or less as described above. Thereby, the possibility that the stainless steel foil 1a may be burnt off can be further suppressed. As a result, the laser weld 5 can be formed stably.

<Battery and its manufacturing method>
A battery 100 according to an embodiment of the present invention includes a battery exterior material 1 and a battery element 20 housed in a battery chamber 2 (see FIGS. 1, 4, and 6). The battery 100 is manufactured by the method for manufacturing the battery exterior material 1 described above, which further includes a step of housing the battery element 20 in an internal space (battery chamber 2) formed by the convex portions of the stainless steel foils 1a and 1b. Is possible.

(Modification)
Note that the shape of the stainless steel foils 1a and 1b in plan view may not be rectangular. Also, the shape of the above-mentioned convex portion in plan view may not be rectangular. These planar shapes may be circular, polygons other than rectangles such as triangles and hexagons, non-circles such as ellipses, and others. The shape may be as follows. Also, the cross-sectional shape of the convex portion need not be rectangular, but may be U-shaped or V-shaped, and may include other shapes.

  Further, the flange portion may not be arranged over the entire circumference of the battery chamber. For example, the battery chamber may be formed by bending, welding, and heat-sealing a single piece of stainless steel foil having two projections as necessary. In this case, the flange portion is formed at a portion other than the folded portion of the stainless steel foil in the peripheral portion of the stainless steel foil. As described above, in the present embodiment, the flange portion is arranged on at least a part of the peripheral portion of the battery chamber.

  Further, the positions of the electrode portion and the heat seal portion are not limited to one of the two end portions of the battery chamber. The electrode part and the heat seal part can be arranged at any positions of the flange part. For example, in the case where one electrode portion extends outside from each of both ends of the battery chamber, heat seal portions are formed at each of both ends of the stainless steel foil. In this case, the laser welded portion 5 is formed on each of both side edges (long sides) of the stainless steel foil while leaving the sealing length of the heat seal portion 6 at both ends of the stainless steel foil.

  The heat sealing sheet 7 does not have to have a slit portion. In this case, the electrode portion 4 may be inserted into the battery chamber 2 by breaking the heat-sealing sheet 7 inserted into the peripheral portion of the stainless steel foil. Alternatively, the heat-fused sheet 7 is folded on both sides of the electrode portion 4 in the laminating direction, that is, between the peripheral portion of the stainless steel foil and the electrode portion 4 in the thickness direction of the battery package 1. May be sandwiched.

  The stainless steel foils 1a and 1b are, for example, BA material of SUS304, but are not limited thereto. For example, it goes without saying that the present invention can be applied to a stainless steel type having a higher thermal conductivity than SUS304 or a stainless steel type having a lower thermal expansion coefficient than SUS304. This is because the thermal conductivity and the coefficient of thermal expansion are related to the susceptibility to thermal strain, that is, the perforation in the laser weld.

  In addition, the battery exterior material 1 (or the battery 100) only needs to be able to hold a part of the flange portion 3 while insulating the electrode portion 4. Therefore, a part of the flange portion 3 may be formed by a method other than heat sealing.

  The present invention is not limited to the above-described embodiment, and various changes can be made within the scope shown in the claims. The present invention also relates to an embodiment obtained by appropriately combining the technical means disclosed in the above description. Included in the technical scope of the invention.

  Hereinafter, the battery exterior material (battery) according to one embodiment of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

  As the stainless steel foil, a SUS304 BA material having dimensions of 165 mm × 220 mm and plate thicknesses of 20, 40, 60, 80, and 100 μm was used. The stainless steel foil was subjected to press molding to produce a stainless steel foil outer packaging material as a molded product. The stainless steel foil outer wrapping material, when viewed in a plan view, is constituted by a rectangular molded portion and a peripheral flange portion. The conditions of the press molding are as follows: the punch R is 1 mm, the die R is 1 mm, and the dimensions of the molded portion are a molding height of 4 mm, a size in a planar view of 140 mm × 190 mm square, and a corner R of 5 mm. . The length of the three sides of the flange at the time of laser welding was set to 10 mm from the side wall of the molded portion. The length of the flange on the side to which the electrode terminal was attached and heat-sealed was 15 mm from the side wall.

  The stainless steel foil outer packaging materials having the same plate thickness were overlaid so that the formed portions faced in opposite directions. The battery element was housed in the internal space (battery compartment) formed by the above-mentioned molded part. The battery element includes a laminated positive electrode, negative electrode, and separator, and is covered with a film to be insulated. The battery element was housed in the battery chamber with electrode terminals (electrode portions) attached. The electrode unit is connected to each of the positive electrode and the negative electrode. The electrode portion was a thin rectangular aluminum plate member having a thickness of about 0.4 mm, and was disposed so as to extend to the outside of the battery chamber through a flange portion on the side to be heat-sealed.

  A laser weld was formed by laser welding using the above-described laser welding apparatus (see FIG. 6). The laser spot diameter was φ30, 100, 200 μm, the laser output was 300 W or less, and the welding speed was 12.5 m / min at the maximum. The distance between the plate holders was 2.5 mm.

(Example 1: welding position)
The laser welding position on the flange was set at 1 mm from the R stop point of the side wall portion, and the laser welding was performed under various position conditions while sequentially changing the distance from the R stopping point to a position of 6 mm. In the case of welding along the longitudinal direction of the formed portion, the non-welded portion was left 13 mm from the end of the side to which the electrode terminal was attached. Then, the welding line welded along the longitudinal direction of the formed portion and the welding line welded along the shorter direction of the formed portion intersect with each other, and the three sides of the flange of the stainless steel foil outer packaging material are laser-welded. did. In this way, a laser weld was formed in a portion where the electrode portion was not arranged.

  Table 2 shows the results of the laser welds formed as described above.

  In Table 2 above, conditions where burn-through occurred on the stainless steel foil (upper plate) on the laser irradiation side are marked with a cross. In addition, the condition that the laser welded portion could be formed without making a hole in the upper plate is marked with a circle.

  As shown in Table 2, at any thickness t, when the distance between the center position of the laser welded portion and the R stop point of the side wall portion is 6 mm or more, it can be seen that burn-through occurs in the upper plate. This is because, as the distance from the side wall increases, the gap between the plates becomes larger under the influence of the wrinkles of the flange.

(Example 2: gap between plates)
Next, laser welding was performed by setting the laser welding position on the flange within a range of 1 mm or more and 5 mm or less from the R stopping point of the side wall, and adjusting the laser welding conditions so that the welding width W was 10 t. A non-contact optical thickness gauge (THS-10 manufactured by Union Optical Co., Ltd.) was used to measure the gap between the plates after laser welding. For a laser weld having no defect, the thickness was measured at a position 40 to 80 μm away from the end of the laser weld in a direction perpendicular to the direction in which the laser weld extended, and two stainless steels were measured from the measured values. The gap between the plates was determined by reducing the thickness of the foil. On the other hand, for a portion where a hole has been opened due to burn-through, the thickness is measured at a position near the portion (a position apart from 40 to 80 μm), and the thickness of the two stainless steel foils is subtracted from the obtained measurement value. Thereby, the gap between the plates was obtained.

  With respect to the above-mentioned stainless steel foil outer wrapping materials having plate thicknesses t of 20, 40, 60, 80, and 100 μm, the gaps G between the plates at various positions of the laser welded portion were measured and the presence or absence of perforations was examined. Further, as a reference example, the above stainless steel foil outer packaging material having a plate thickness t of 400 μm was prepared, and a test was also performed on the stainless steel foil outer packaging material. Table 3 summarizes the results.

  As shown in Table 3, when the gap G between the plates was 1 t or less, there was no burn-through of the upper plate, and therefore no perforation occurred (Example of the present invention). On the other hand, when the gap G between the plates exceeded 1 t, burnout of the upper plate occurred, resulting in perforation (comparative example).

  Further, in the case of the stainless steel foil outer packaging material having a plate thickness t of 400 μm (Reference Examples of Nos. 22 and 23), even when the gap G between the plates was 0.8 t, a hole was sometimes formed. This is a different result from the case of the stainless steel foil outer packaging material having a plate thickness t of 20 to 100 μm which is an example of the present invention. In the example of the present invention, welding can be performed normally even when the gap G between the plates is 0.8 t.

  The reason is that when the plate thickness is large as in the reference example, the heat capacity is large and it is difficult to remove heat during laser welding. It is thought that this is because it is easy.

(Reference example)
In addition, for comparison with the present invention example, a test was conducted for investigating the presence or absence of perforations in the laser welded portion when the inter-plate gap G was smaller than 0.8 t for a reference example having a plate thickness t of 400 μm. . Specifically, the test was performed under the condition that the welding width W was 3.5 t and the gap G between the plates was 110 μm to 200 μm, that is, the plate thickness ratio was 0.28 t to 0.5 t. Table 4 shows the results.

  As shown in Table 4, when a stainless steel foil outer packaging material having a thickness t of 400 μm was used, no hole was formed at a thickness ratio of 0.28 t (No. 31), but a thickness ratio larger than 0.28 t. Then, perforations occurred (Nos. 32-34).

  Further, as a result of the test performed with the gap G between the plates set to 120 μm (0.3 t), holes were formed in the laser welded portion as shown in FIG. FIG. 7 is a schematic view showing a state in which a cross section of the laser welded portion in the reference example is observed using an optical microscope.

  As shown in FIG. 7, each of the stainless steel foil 100a and the stainless steel foil 100b has a plate thickness t of 400 μm, and a gap G between the plates is 120 μm (plate thickness ratio 0.3t). The welding width W is 1.4 mm (3.5 t in thickness ratio). In this reference example, since the plate thickness t is as thick as 400 μm, the heat capacity of the stainless steel foil is large. Therefore, even if the inter-plate gap G is within the range of the present invention, it is considered that the molten state continues for a relatively long time during the laser welding, and the molten metal drips and holes are formed. On the other hand, as shown in the above-described embodiment of the present invention, a sound weld portion can be formed without causing burn-through when the plate thickness is small at the same plate thickness ratio.

  Summarizing the above results, the present invention is directed to a thin material having a plate thickness of 20 to 100 μm, and has a small heat capacity in a molten state, so that the molten metal is cooled quickly and the heat-affected zone is accompanied by shrinkage. Solidifies to form a laser weld. Therefore, even when the thickness ratio of the gap G between the plates is as large as 1.0 t, and even when the welding width W is as large as 10 t, it is possible to form the laser welded portion without forming a hole. it can. In other words, in the example of the present invention, a phenomenon that is clearly different from the case where a stainless steel foil having a thickness of, for example, 400 μm is used occurs because the heat capacity is small due to the small thickness. Therefore, based on the conventional technology, it can be understood that the condition range (technical idea) of the gap between plates and the welding width of the present invention cannot be easily reached.

(Evaluation of sealing performance)
In the above-mentioned test, a sample having no problem (no perforation) in the appearance inspection was used as a test material. A slit portion was formed in a 165 mm × 26 mm × 0.1 mm polyolefin-based heat sealing film (manufactured by Dai Nippon Printing Co., Ltd.), and the film was bent at a center line including the slit portion. Then, the obtained heat-sealed sheet was inserted from the unwelded portion of the test material until it reached the ends of two laser welds. The electrode portion extending from the battery chamber was inserted into the slit of the heat-sealing sheet, and the electrode portion was sandwiched between the heat-sealing sheets. Then, the electrode portion and the heat-sealing sheet were sandwiched between flanges of the non-welded portion of the stainless steel foil outer packaging material, and the portion was pressed with a heat sealer at 190 ° C. for 10 seconds and joined by heat sealing. Then, unnecessary portions of the laser welds were cut and removed. Thus, a battery was produced (see FIG. 4C).

  A hole was made in a part of the battery exterior material of the manufactured battery, and a negative pressure was created by evacuating the inside of the battery chamber, and a He leak test was performed to check the airtightness. As a result, a battery manufactured using a test material having no problem in appearance observation had no problem in the He leak test and had sufficient airtightness.

  INDUSTRIAL APPLICATION This invention can be utilized suitably for secondary batteries, such as a lithium ion battery. For example, it can be used for a secondary battery mounted on a vehicle such as an electric vehicle, a secondary battery mounted on various electronic devices, and the like.

DESCRIPTION OF SYMBOLS 1 Battery exterior material 1a ・ 1b Stainless steel foil 2 Battery room 3 Flange part (joining part)
5 Laser welds (welds)
20 battery element 100 battery

Claims (10)

A battery chamber that houses the battery element, which is formed by the joined stainless steel foil,
A joint disposed at least at a part of the periphery of the battery chamber,
The joining portion includes at least a welded portion formed by laser welding the stainless steel foils to each other,
When the stainless steel foil on the side irradiated with the laser is a first stainless steel foil and the stainless steel foil on the opposite side is a second stainless steel foil,
In the cross section when the welded portion is cut along a plane perpendicular to the extension direction of the welded portion,
The gap G between the first stainless steel foil and the second stainless steel foil in the vicinity of the welded portion satisfies the following expression (1),
A battery exterior material, wherein a welding width W of the surface of the first stainless steel foil in a direction perpendicular to the stretching direction of the welded portion satisfies the following expression (2).
G ≦ 1t (1)
1t ≦ W ≦ 10t (2)
(here,
t: thickness of the first stainless steel foil)   2. The battery packaging material according to claim 1, wherein the first and second stainless steel foils have a thickness of 20 μm or more and 100 μm or less. 3. Part of the battery chamber is formed by the first stainless steel foil,
A peripheral portion of the first stainless steel foil around the convex portion forming the battery chamber,
In the cross section of the battery exterior material, a portion where the first stainless steel foil rises in a curved line from the peripheral portion toward the side wall portion of the convex portion is defined as a rising portion, and the portion on the surface of the first stainless steel foil is formed. If the starting point of the rising portion is the R stop point,
The at least one part of the said welding part is formed so that the distance of the center position of the said welding width W and the said R stopping point may be in the range of 1 mm or more and 5 mm or less. Battery exterior material according to 1. Assuming that the surface of the first stainless steel foil on the side irradiated with the laser is a first surface, and the surface of the second stainless steel foil on the side far from the first surface is a second surface,
The welded portion includes a thin portion formed in the cross section so as to be recessed from an outer edge of the welded portion toward a center of the welded portion on both the first surface and the second surface. The battery exterior material according to any one of claims 1 to 3, wherein:   The battery according to any one of claims 1 to 4, wherein the first and second stainless steel foils do not have a resin layer on surfaces facing each other in a portion where a weld is formed. Exterior materials.   A battery comprising: the battery exterior material according to claim 1; and the battery element housed in the battery chamber. A space forming step of superimposing the first stainless steel foil and the second stainless steel foil on each other to form an internal space serving as a battery chamber for housing the battery element;
A laser welding step of irradiating the first stainless steel foil with a laser to form a weld by laser-irradiating the first and second stainless steel foils with at least a part of the periphery of the battery chamber. Including
In the laser welding step, in a cross section when cut along a plane perpendicular to the stretching direction of the welded portion,
The gap G between the first stainless steel foil and the second stainless steel foil at the position where the laser is irradiated satisfies the following expression (1),
A battery exterior, wherein the welding portion is formed such that a welding width W of the surface of the first stainless steel foil in a direction perpendicular to the stretching direction of the welding portion satisfies the following expression (2). The method of manufacturing the material.
G ≦ 1t (1)
1t ≦ W ≦ 10t (2)
(here,
t: thickness of the first stainless steel foil)   The method of claim 7, wherein the first and second stainless steel foils have a thickness of 20 μm or more and 100 μm or less. Part of the battery chamber is formed by the first stainless steel foil,
A peripheral portion of the first stainless steel foil around the convex portion forming the battery chamber,
In the cross section of the battery exterior material, a portion where the first stainless steel foil rises in a curved line from the peripheral portion toward the side wall portion of the convex portion is defined as a rising portion, and the portion on the surface of the first stainless steel foil is formed. If the starting point of the rising portion is the R stop point,
The laser welding step, wherein at least a part of the welding portion is formed such that a distance between a center position of the welding width W and the R stopping point is within a range of 1 mm or more and 5 mm or less. 9. The method for producing a battery exterior material according to 7 or 8.   The method for manufacturing a battery exterior material according to any one of claims 7 to 9, further comprising a step of housing the battery element in the battery chamber.

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