Battery case, battery, and method for manufacturing battery case

Abstract

Provided is a battery case (1) including a lid body (11) and body (12), the battery case (1) being characterized in that: the lid body (11) and the body (12) are joined by seaming; the lid body (11) contains any of a stainless steel material, a plated steel material, a coated steel material, or an aluminum material; the body (12) includes a Ni-plated steel material having a base steel material and a Ni-based plating layer; the body (12) includes at least one weld metal (30) extending in a direction intersecting the lid body (11); and when the average Cr amount of the weld metal (30) is defined as [Cr] and the average Ni amount of the weld metal (30) is defined as [Ni], [Cr] + 4 × [Ni] ≥ 5.00 is satisfied.

Description

Battery case, battery, and method for manufacturing a battery case

[0001] This disclosure relates to a battery case, a battery, and a method for manufacturing a battery case. This disclosure claims priority under Japanese Patent Application No. 2024-180773, filed in Japan on October 16, 2024, the contents of which are incorporated herein by reference.

[0002] Lithium-ion batteries are widely used as batteries for electric vehicles. The battery cases that make up lithium-ion batteries come in various shapes, such as cylindrical, rectangular, and pouch-type. Among these, rectangular battery cases are often made of aluminum, as described in Patent Document 1. For example, Patent Document 1 discloses an aluminum can for secondary batteries, assembled by laser welding a lid and an outer casing made of aluminum alloy plates, and a method for manufacturing the same.

[0003] In recent years, there has been a trend towards larger battery cases. In electric vehicles, batteries are stored by covering the floor, but in order to reduce the height of the floor, there is a movement to change the position of the battery terminals from the current top terminals to side terminals, as seen in blade batteries.

[0004] Japanese Patent Application Publication No. 2013-097900

[0005] If a battery case with horizontal terminals as described above is adopted, the drawing height will be high with current deep drawing methods, making forming difficult. Therefore, the method may change to either creating a cylinder by bending a flat plate into a square shape and welding it, then welding the lid and bottom plate, or forming a pipe from a flat plate, expanding it into a square shape, and then welding the lid and bottom plate. Possible welding methods for the joints in this method include butt laser welding and seam welding. On the other hand, in the laser-welded parts of a battery case using plated steel sheet, it is thought that the improvement in corrosion resistance (electrolyte resistance) will be less pronounced compared to the base material that makes up the plated lid (and bottom plate) and body. Therefore, under very harsh conditions, there is a possibility that the welded parts on the inner surface of the battery case may corrode. Furthermore, it is difficult to apply corrosion-resistant treatment to the inner surface of the welded parts after laser welding the lid and body of the battery case.

[0006] The present invention has been made in view of the above, and aims to provide a battery case with high resistance to electrolytes.

[0007] (1) A battery case according to one aspect of the present invention is a battery case comprising a lid and a body, wherein the lid and the body are joined by crimping, the lid is made of any of stainless steel, plated steel, painted steel, or aluminum, the body comprises a Ni-plated steel having a base steel and a Ni-based plating layer, the body comprises at least one weld metal extending in a direction intersecting the lid, and when the average Cr amount of the weld metal is [Cr] and the average Ni amount of the weld metal is [Ni], the equation [Cr] + 4 × [Ni] ≥ 5.00 is satisfied. (2) In the battery case described in (1) above, the length of the body in a direction perpendicular to the lid may be 1.5 times or more the length of the lid in the longitudinal direction. (3) In the battery case described in (1) or (2) above, the lid may be made of a Ni-plated steel having a base steel and a Ni-based plating layer. (4) In the battery case described in any one of (1) to (3) above, the thickness of the Ni-plated steel material may be 0.1 to 1.4 mm. (5) In the battery case described in any one of (1) to (4) above, the thickness of the Ni-based plating layer may be 0.1 to 10.0 μm. (6) In the battery case described in any one of (1) to (5) above, the basis weight of the Ni-based plating layer may be 2.0 to 89.0 g / m ２(7) In the battery case described in any one of (1) to (6) above, there may be an Fe-Ni alloy layer between the Ni-based plating layer and the base steel material. (8) In the battery case described in any one of (1) to (7) above, the excess height of the weld metal may be 50% or less of the plate thickness of the Ni-plated steel material. (9) The battery case described in any one of (1) to (8) above may be a neutral can. (10) A battery according to one aspect of the present invention is a battery comprising the battery case described in any one of (1) to (9) above. (11) A method for manufacturing a battery case according to one aspect of the present invention is a method for manufacturing a battery case comprising a lid and a body, comprising: a lid forming step of forming the lid by processing any of stainless steel, plated steel, painted steel, or aluminum; a body forming step of forming the body comprising at least one weld metal by welding a base steel material and a plated steel material having a Ni-based plating layer; and a joining step of crimping the lid and the body together, wherein when the average amount of Cr in the weld metal is [Cr] and the average amount of Ni in the weld metal is [Ni], the equation [Cr] + 4 × [Ni] ≥ 5.00 is satisfied. (12) In the method for manufacturing a battery case according to (11) above, the weld metal may be formed using an austenitic filler wire. (13) In the method for manufacturing a battery case according to (11) or (12) above, the weld metal may be formed using a filler wire, and the supply speed of the filler wire may be 0.1 to 3.0 times the welding speed.

[0008] The battery case according to the present invention and the battery using the battery case according to the present invention have high electrolyte resistance. Furthermore, the manufacturing method of the battery case according to the present invention makes it possible to provide a battery case with high electrolyte resistance.

[0009] This is a schematic perspective view illustrating a battery case according to one embodiment of the present invention. This is a schematic cross-sectional view illustrating one embodiment of a welded portion formed on the body. This is a schematic cross-sectional view illustrating another embodiment of a welded portion formed on the body. This is a schematic cross-sectional view illustrating a crimping structure. This is a schematic perspective view illustrating a modified example of the battery case according to one embodiment of the present invention. This is a diagram illustrating an example of a method for manufacturing a battery case according to one embodiment of the present invention. This is a diagram illustrating another example of a method for manufacturing a battery case according to one embodiment of the present invention.

[0010] Embodiments of the present invention will be described below with reference to examples, but it is obvious that the present invention is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of the present invention are obtained. In addition, each component of the following embodiments can be combined with one another. In this specification, numerical ranges expressed using "~" mean a range that includes the numerical values ​​written before and after "~" as the lower and upper limits. In this specification, the term "process" is included not only in the case of an independent process, but also in the case of a process that cannot be clearly distinguished from other processes, as long as the intended purpose of that process is achieved.

[0011] In the following embodiments, "steel material" includes steel plates, parts machined from steel plates into shapes other than flat plates, and steel plates formed by joining different types of steel plates. "Aluminum material" includes aluminum plates, parts machined from aluminum plates into shapes other than flat plates, and steel plates formed by joining different types of aluminum plates. "Battery case" refers to a case having a sealed structure to prevent the contents, such as electrolyte, contained within the case from leaking to the outside.

[0012] <Embodiment 1> First, Figure 1 shows an example of a battery case 1 according to this embodiment.

[0013] [Battery Case] ​​The battery case 1 shown in Figure 1 is a battery case 1 that includes a lid 11, a body 12, and weld metal 30. As will be described later, the battery case 1 shown in Figure 1 has a body 12 that is manufactured by bending and welding steel material. Therefore, there is a welded part in the body 12.

[0014] [Lid] The lid 11 is joined to the body 12 to form the battery case 1. The material that makes up the lid 11 is one of the following: stainless steel, plated steel, painted steel, or aluminum.

[0015] The stainless steel material constituting the lid 11 is preferably a stainless steel plate with a carbon content of more than 0% and 0.05% or less. Examples of stainless steel materials constituting the lid 11 include SUS304L, SUS316L, and SUS430LX.

[0016] The plated steel material constituting the lid 11 is preferably a Cr-plated steel material having a Cr-based plating layer on the surface of the base steel sheet, or a Ni-plated steel material having a Ni-based plating layer on the surface of the base steel material. As the Ni-plated steel material, the same Ni-plated steel material used for the body 12, as described later, may be used for the lid 11. The lid 11 may be composed of, for example, a single Ni-plated steel sheet. The plating layer is provided on at least the surface of the lid 11 that faces inward towards the battery case 1. The plating layer may be provided on both sides of the lid 11.

[0017] The painted steel material constituting the lid 11 is preferably one having a coating made of a fluororesin on the surface of the base steel material.

[0018] As the aluminum material constituting the lid 11, A1000 series or A3000 series is preferred. For example, A3003 can be used as the aluminum material constituting the lid 11.

[0019] The lid 11 may be provided with an injection port for injecting electrolyte after sealing the battery case 1, holes for passing electrodes, notches, protrusions, recesses, etc. In the example shown in Figure 1, the lid 11 is connected to the opening 15 of the body 12, which will be described later, and is positioned opposite the bottom lid 14.

[0020] Note that the X, Y, and Z coordinate axes in Figures 1 and 2 are orthogonal to each other. In the example in Figure 1, the plate surface of the lid 11 is shown to be parallel to the X and Y coordinate axes, but this is not the only example.

[0021] [Bottom Cover] The bottom cover 14 can adopt the same configuration as the lid 11. Here, for convenience, the lid 11 and the bottom cover 14 are described separately, but "lid" also includes the bottom cover 14. The shape of the bottom cover 14 may be the same as that of the lid 11. In the example in Figure 1, the bottom cover 14 is connected to an opening 16 provided on the opposite side of the opening 15 of the body 12, sandwiching the body 12, and the lid 11 and the bottom cover 14 are arranged so that their plate surfaces face each other.

[0022] [Body] The body 12 is composed of two opposing sides 12a and 12b, and two opposing sides 12c and 12d, as illustrated in Figure 1. One end of side 12a, which extends in a direction intersecting the plate surfaces of the lid 11 and bottom lid 14, is connected to the end of side 12c, and the other end is connected to the end of side 12d. One end of side 12b, which extends in a direction intersecting the plate surfaces of the lid 11 and bottom lid 14, is connected to the end of side 12c, and the other end is connected to the end of side 12d.

[0023] In the example shown in Figure 1, the plate surfaces of the lid 11 and bottom lid 14 are parallel to the X and Y coordinate axes, and the sides 12a, 12b, 12c, and 12d are parallel to the Z coordinate axis, but this is not limited to this. Also, in the example shown in Figure 1, the sides 12a and 12b are parallel to the Y and Z coordinate axes, and the sides 12c and 12d are parallel to the X and Z coordinate axes. Also, in the example shown in Figure 1, the ends connecting the sides 12a, 12b, 12c, and 12d are parallel to the Z coordinate axis. However, the shape of the body 12 is not limited to this, and opposing sides 12a and 12b, or sides 12c and 12d, do not have to be parallel.

[0024] As shown in Figure 1, the body 12 has an opening 15. The body 12 also has openings 16 on each side, opposite to the opening 15. The lid 11 is joined to the body 12 so as to close the opening 15 by a crimping method described later, and the bottom lid 14 is joined to the body 12 so as to close the opening 16.

[0025] As described above, since the battery case 1 is sealed, it is preferable that the outer shape of the lid 11 (end face of the lid 11) and the inner or outer shape of the opening 15 of the body 12 match to the extent that the battery case 1 can be sealed. Similarly, it is preferable that the outer shape of the bottom lid 14 (end face of the bottom lid 14) and the inner or outer shape of the opening 16 of the body 12 match to the extent that the battery case 1 can be sealed.

[0026] A welded joint containing weld metal 30 is formed in the body 12 of the battery case 1. This welded joint joins the end faces of the Ni-plated steel material that makes up the body 12. As shown in Figure 1, the welded joint is formed along the Z coordinate axis, from the end on the opening 15 side to the end on the opening 16 side of the side surface 12a of the body 12.

[0027] Figure 2 shows an example of a cross-sectional view of the battery case 1 taken from a plane perpendicular to the extension direction of the weld metal 30. Figure 2 shows the weld metal 30 and its vicinity in a cross-section perpendicular to the Z coordinate axis along line A-A in Figure 1. As shown in Figure 2, the end faces of the Ni-plated steel materials constituting the body 12 are joined together by the weld metal 30. Note that the end faces of the Ni-plated steel materials are molten and therefore not shown in Figure 2. With this configuration, the base steel material of the Ni-plated steel is not exposed on the inner surface of the battery case 1 (the surface located on the inside side of the battery case, which is the surface on the positive direction side of the X coordinate axis in Figure 2), thus ensuring the electrolyte resistance of the inner surface of the battery case 1.

[0028] Furthermore, as will be described later, the electrolyte resistance of the weld metal 30 can be improved by having a corrosion resistance index of 5.00 or higher.

[0029] The advantage of forming a welded area containing the weld metal 30 on the side surface of the body 12 is that deformation of the Ni-plated steel material due to the thermal history during welding is suppressed. In the example shown in Figure 1, the so-called weld bead formed by the weld metal 30 is formed in a straight line on the side surface 12a, but as long as the battery case 1 is sealed, the weld bead may include curved sections, and the entire weld bead may be curved. Furthermore, the weld metal 30 may be formed on any side surface of the body 12 as long as the battery case 1 can be sealed, and the weld metal 30 may be formed over multiple side surfaces.

[0030] In the example in Figure 1, the weld is located on the side surface 12a, and the Ni-plated steel material constituting the body 12 is joined thereto. However, the example is not limited to this, and the weld may be located at the end of the side surface. That is, adjacent side surfaces may be joined together at their ends by the weld metal 30.

[0031] Figure 3 shows an example in which the sides are joined together by weld metal 30. Figure 3 is a cross-sectional view of the battery case 1 taken with a plane perpendicular to the direction of extension of the weld metal 30 (parallel to the Z coordinate axis). In the example in Figure 3, the end face of the side surface 12a and the plate surface of the side surface 12c that constitute the body 12 are joined together by weld metal 30. Even with this configuration, the base steel material of the Ni-plated steel is not exposed on the inner surface of the battery case 1 (the surface located on the inside side of the battery case, which in Figure 3 is the surface on the X coordinate axis side and the surface on the positive direction side of the Y coordinate axis), so the electrolyte resistance of the inner surface of the battery case 2 can be ensured. In this way, by joining the sides of the body 12 at their ends, the amount of Ni-based plating layer components of the Ni-plated steel that dissolve into the weld metal 30 increases, which has the advantage of forming a weld metal 30 with high corrosion resistance.

[0032] The material constituting the fuselage 12 is a nickel-plated steel material having a nickel-based plating layer on the surface of the base steel material, as will be described later. The fuselage 12 may be made of, for example, a single nickel-plated steel sheet.

[0033] In the battery case 1, the lid 11 and the body 12, and the bottom lid 14 and the body 12 are joined by crimping at the connection points. The connection points are the places where the lid 11 (or bottom lid 14) and the body 12 come into contact. Figure 4 shows an example of when the lid 21 and the body 22 are joined by crimping. Figure 4 illustrates a cross-section of the end of the side surface 12a of the body 12 located on the lid 11 side, in a plane perpendicular to the direction of extension. As for the crimping structure, for example, a structure generally known as a double crimping structure can be adopted. The same crimping can be used to join the bottom lid 14 and the body 12. The crimping does not necessarily need to join the lid 11 (or bottom lid 14) and the body 12 over the entire range of the connection points; as long as the battery case 1 can be sealed, the joining by crimping may be applied to only a part of the connection points. Furthermore, the outer circumference of the lid 11 (or bottom lid 14) may be provided with a rising portion that extends from the plate surface of the lid 11, and this rising portion may be joined to the body 12 by crimping.

[0034] [Weld Metal] In the battery case 1 shown in Figure 1, a welded portion including weld metal 30 is formed on the body 12. In the battery case 1 of this embodiment, when the average Cr amount of the weld metal 30 is [Cr] and the average Ni amount is [Ni], the "corrosion resistance index" expressed as [Cr] + 4 × [Ni] is 5.00 or higher.

[0035] The average Cr content of the weld metal 30 is measured using ICP (Inductively Coupled Plasma) emission spectroscopy. The Cr content at five arbitrary points in the weld metal 30 is measured by ICP, and the arithmetic mean of these values ​​is taken as the average Cr content. The measurement points can be any part of the weld metal 30 excluding the end portion. The end portion of the weld metal is recessed compared to the steady portion excluding the end portion, so the area that is the end portion can be determined from its appearance. The average Ni content in the weld metal 30 is calculated using the same method as the average Cr content.

[0036] The weld metal 30 is the portion of the weld where filler, steel, etc., melt and solidify due to irradiation with a laser beam during laser welding. It is a part of the weld and is metal that melts and solidifies during welding. When filler is used during laser welding, the material sources for the weld metal 30 are the multiple steel materials being joined and the filler. If the steel materials to be welded are plated, the components of the plating also melt and become part of the material that makes up the weld metal 30. In addition to elements from these sources, the weld metal 30 may also contain oxygen and nitrogen from the air, as well as unavoidable impurities.

[0037] In the weld metal 30 of the battery case 1 according to this embodiment, the electrolyte resistance of the weld metal 30 can be improved by having a [Cr] + 4 × [Ni] (corrosion resistance index) of 5.00 or higher.

[0038] [Ni-plated Steel Material] The Ni-plated steel material used as the body 12 (and / or the lid 11, the bottom lid 14) is a steel material having a Ni-based plating layer on the surface of the base steel material. As the chemical composition of the base steel material, C (carbon): more than 0 mass% and 0.150 mass% or less, Si (silicon): more than 0 mass% and 0.800 mass% or less, Mn (manganese): more than 0 mass% and 1.00 mass% or less, P (phosphorus): more than 0 mass% and 0.05 mass% or less, S (sulfur): more than 0 mass% and 0.050 mass% or less, Mo (molybdenum): 0 to 0.300 mass%, Cu (copper): 0 to 1.00 mass%, Ti (titanium): 0 to 0.100 mass%, Al (aluminum): 0 to 0.10 mass%, Co (cobalt): 0 to 1.000 mass%, Nb (niobium): 0 to 0.100 mass%, N (nitrogen): 0 to 0.030 mass%, Sn (tin): 0 to 0.100 mass%, Cr (chromium): 0 to 0.40 mass%, Ni (nickel): 0 to 1.0000 mass%, B (boron): 0 to 0.0100 mass%, Mg (magnesium): 0 to 0.0500 mass%, Zr (zirconium): 0 to 0.5 mass%, W (tungsten): 0 to 0.200 mass%, Ca + REM: 0 to 0.1 mass%, are contained, and the balance preferably contains Fe (iron) and impurities. The balance may consist of Fe (iron) and impurities. Impurities refer to components contained in raw materials or components mixed in the manufacturing process, and are not components intentionally contained. Such a base steel sheet is preferable in terms of excellent formability.

[0039] The chemical composition of the base steel material of the plated steel material is measured in accordance with JIS G 1258-1:2014 using inductively coupled plasma (ICP) emission spectrometry. However, for C (carbon), S (sulfur), and N (nitrogen), they are measured by well-known gas analysis.

[0040] The C content of the base steel material (base material) is more preferably more than 0 mass% and 0.070 mass% or less. Thereby, the Ni-plated steel material has the advantage of being more excellent in formability. In addition, since the base steel material can obtain corrosion resistance by having a Ni-based plating layer on its surface, it may be a steel material other than stainless steel.

[0041] A Ni-based plating layer is provided on the surface of the base steel material constituting the Ni-plated steel material. The Ni-based plating layer is a plating layer mainly composed of Ni. Specifically, when measured using GDS (Glow discharge optical emission spectrometry), the range where the Ni concentration is 80% by mass or more is defined as the Ni-based plating layer. The Ni-based plating layer is provided at least on the surface of the body 12 facing the inside of the battery case 1. The Ni-based plating layer may be provided on both surfaces of the base steel material constituting the body 12.

[0042] From the viewpoint of corrosion resistance, the chemical composition of the Ni-based plating layer preferably includes a layer composed of Ni: 50 to 95% by mass, Fe: 5 to 50% by mass, and impurities. The chemical composition of the Ni-based plating layer can be measured by GDS. The Ni-based plating layer may contain a total of 30% by mass or less of any one or more alloy elements of Co, Sn, Zn, W, Mo, or Cr.

[0043] The thickness of the Ni-based plating layer is more preferably 0.1 to 10.0 μm. Increasing the thickness of the Ni-based plating layer improves the electrolytic solution resistance while increasing the cost. Setting the thickness of the Ni-based plating layer to 0.1 to 10.0 μm has the advantage of excellent balance between electrolytic solution resistance and cost. The thickness of the Ni-based plating layer can be measured using a GDS device. Using a GDS device, measure the thickness of any 5 points of the plating layer, and take the arithmetic mean value of these as the thickness of the Ni-based plating layer.

[0044] The weight per unit area of the Ni-based plating layer may be 2.0 to 89.0 g / m ２ The weight per unit area of the Ni-based plating layer is measured by ICP emission spectrometry (ICP-OES). First, dissolve the Ni-based plating layer with a predetermined area in acid. Next, quantitatively analyze the Total-Ni amount contained in the dissolved solution by ICP-OES. By dividing the Total-Ni amount quantified by ICP-OES by the above-mentioned predetermined area, the weight per unit area can be obtained. Thereby, while suppressing the cost increase due to Ni plating, the corrosion resistance of the base steel plate can be improved.

[0045] An Fe-Ni alloy layer may be present between the Ni-based plating layer and the base steel material. The Fe-Ni alloy layer is a layer in which the Ni concentration is 10% by mass or more and less than 80% by mass. The presence of the Fe-Ni alloy layer further improves corrosion resistance and formability. The Fe-Ni alloy layer can be measured using a GDS device. The Ni-based plating layer of the Ni-plated steel sheet may be an alloyed plating layer that is alloyed with the base steel sheet. In this case, the Ni-based plating layer may be a fully diffused plating layer in which the Fe from the base steel sheet is diffused to its surface, or a partially diffused plating layer in which the Fe from the base steel sheet is not diffused to its surface. On the other hand, the Ni-based plating layer may not be alloyed with the base steel sheet.

[0046] From the viewpoint of improving workability, the thickness of the Fe-Ni alloy layer is preferably 0.2 μm or more, and more preferably 0.5 μm or more. The thickness of the Fe-Ni alloy layer can be measured using a GDS device. Using a GDS device, the thickness of five arbitrary points on the cross-section of the Ni-plated steel material is measured, and the arithmetic mean of these measurements is taken as the thickness of the Fe-Ni alloy layer.

[0047] A Ni-W plating layer may be further provided on top of the Ni-based plating layer. Having a Ni-W plating layer on the surface improves corrosion resistance and formability. The Ni-W plating layer is defined as the range in which the W concentration is 10% by mass or more when measured using GDS. The thickness of the Ni-W plating layer can be measured using a GDS device. The thickness of five points is measured using a GDS device, and the arithmetic mean of these measurements is taken as the thickness of the Ni-W plating layer.

[0048] The thickness of the plated steel is more preferably 0.1 to 1.4 mm. This has the advantage of providing a battery case that is lightweight and has excellent mechanical strength. The thickness of the plated steel is determined by measuring the thickness at five points on a flat surface, excluding processed areas such as bent sections, using a micrometer, and taking the arithmetic mean of these measurements as the thickness of the plated steel.

[0049] Furthermore, in the Ni-plated steel material described above, various chemical conversion coating layers (not shown) may be present between the base steel material and the plating layer. The presence of such chemical conversion coating layers makes it possible to further improve the adhesion between the base steel material and the plating layer. In addition, the presence of such chemical conversion coating layers makes it possible to further improve the corrosion resistance of the Ni-plated steel material.

[0050] The chemical conversion coating layer is not particularly limited and can be formed using various chemical conversion treatments. Examples of such chemical conversion treatments include chromate-based chemical conversion treatments and non-chromate-based chemical conversion treatments. Examples of non-chromate-based chemical conversion treatments include chemical conversion treatments using inorganic compounds such as vanadium compounds, titanium compounds, zirconium compounds, and phosphate compounds, as well as silica-based chemical conversion treatments.

[0051] In the battery case 1 according to this embodiment, the length L of the body 12 in the direction perpendicular to the lid 11 may be 1.5 times or more the length W of the lid 11 in the longitudinal direction. This has the advantage that even in a space with limited height, the lid 11 equipped with terminals can be positioned laterally to increase the battery's space utilization. For example, by using a battery with terminals arranged on a laterally positioned lid 11 as the battery for an electric vehicle, the thickness of the electric vehicle's floor can be reduced, and the passenger space of the electric vehicle can be expanded.

[0052] Figure 5 illustrates a battery case 1 in which the length L of the body 12 in the direction perpendicular to the lid 11 is 1.5 times or more the length W of the lid 11 in the longitudinal direction. The direction perpendicular to the lid 11 means the direction perpendicular to the plate surface of the lid 11.

[0053] In the example shown in Figure 5, the length L of the body 12 in the direction perpendicular to the lid 11 is the length in the direction parallel to the Z coordinate axis of the body 12. The longitudinal length W of the lid 11 means the maximum length of the lid 11 in the direction parallel to the plate surface of the lid 11. In the example shown in Figure 5, the longitudinal length W of the lid 11 is the length in the direction parallel to the X coordinate axis of the lid 11.

[0054] In the above embodiment, the weld metal 30 overlay height may be 50% or less of the plate thickness of the Ni-plated steel material. Overlay refers to the portion that protrudes extra from the surface of the Ni-plated steel material, and its definition is as disclosed in JIS Z 3001. The weld metal 30 overlay height is as disclosed in JASS 6-20011. The weld metal 30 overlay height is determined by cutting out three cross-sections of the steady portion excluding the end portion of the weld metal 30, observing these cross-sections, and taking the arithmetic mean of the measured values.

[0055] The excess reinforcement height is 50% or less of the thickness of the Ni-plated steel sheet, preferably 30% or less, and more preferably 10% or less. This reduces the external dimensions and improves the battery loading efficiency. In the case of contact surfaces with cooling plates, it also reduces gap fillers and lowers manufacturing costs.

[0056] The following describes a method for manufacturing a battery case according to the present invention. These manufacturing methods allow for the suitability of producing battery cases with high electrolyte resistance. However, it is obvious that battery cases obtained by methods other than those described below can also be considered as battery cases of the present invention, as long as they satisfy the requirements of the present invention.

[0057] The battery case 1 according to this embodiment may be used as a battery case for stationary applications such as backup power for solar power generation equipment or power supply equipment during power outages, or as a storage battery installed on the wall of an ordinary house.

[0058] <Embodiment 2> The method for manufacturing a battery case according to this embodiment is a method for manufacturing a battery case including a lid and a body, comprising: a lid forming step of forming a lid by processing one of stainless steel material, plated steel material, painted steel material, or aluminum material; a body forming step of welding a base steel material and plated steel material having a Ni-based plating layer to form a body including at least one weld metal; and a joining step of crimping the lid and the body together. Furthermore, in the method for manufacturing a battery case according to this embodiment, when the average amount of Cr in the weld metal is [Cr] and the average amount of Ni in the weld metal is [Ni], the condition [Cr] + 4 × [Ni] ≥ 5.00 is satisfied.

[0059] The battery case manufacturing method according to this embodiment can be used to manufacture the battery case 1 according to Embodiment 1. Below, the manufacturing method for the battery case will be described using the steps for manufacturing the battery case 1 as an example.

[0060] (Lid Forming Process) The lid 11 is formed by processing stainless steel, plated steel, painted steel, or aluminum into a predetermined shape. The outer circumference of the lid 11 may be provided with a raised portion or the like, as described in the above embodiment, for connection to the body 12. The lid 11 may also have an inlet for injecting electrolyte after sealing the battery case 1, holes for passing electrodes, notches, protrusions, recesses, etc.

[0061] (Body Forming Process) In the battery case manufacturing method according to this embodiment, a Ni-plated steel material having a Ni-based plating layer on the surface of a base steel material is bent, and the ends of the bent Ni-plated steel material are joined by laser welding to form the body 12. This forms the body 12 having sides 12a, 12b, 12c and 12d as described in the above embodiment.

[0062] An example of the fuselage formation process is shown in Figure 6. For the bending process, a Ni-plated steel material S as shown in Figure 6(a) is bent into the shape shown in Figure 6(b) to obtain the shape shown in Figure 6(c). Then, the weld metal 30 is formed by laser welding to form the fuselage 12.

[0063] Another example of the fuselage formation process is shown in Figure 7. A Ni-plated steel material S, as shown in Figure 7(a), is bent into a cylindrical shape as shown in Figure 7(b), and the ends of the Ni-plated steel material are joined together by laser welding with weld metal 30. In this way, a cylindrical intermediate material as shown in Figure 7(b) is created. Then, this cylindrical intermediate material is expanded into a rectangular shape to obtain the shape shown in Figure 7(c).

[0064] The Ni-plated steel material used as the fuselage 12 (and / or lid 11, bottom lid 14) is a steel material having a Ni-based plating layer on the surface of the base steel material. The chemical composition of the base steel material is as follows: C (carbon): greater than 0% by mass and 0.150% by mass or less, Si (silicon): greater than 0% by mass and 0.800% by mass or less, Mn (manganese): greater than 0% by mass and 1.00% by mass or less, P (phosphorus): greater than 0% by mass and 0.05% by mass or less, S (sulfur): greater than 0% by mass and 0.050% by mass or less, Mo (molybdenum): 0 to 0.300% by mass, Cu (copper): 0 to 1.00% by mass, Ti (titanium): 0 to 0.100% by mass, Al (aluminum): 0 to 0.10% by mass, Co (cobalt): 0 to 1.000% by mass, Nb (niobium): 0 to 0.100% by mass, N (nitrogen): 0 to 0.030% by mass, Sn (tin): 0 to 0.100% by mass, Cr (chromium): 0 to 0.40% by mass, Preferably, the base steel sheet contains Ni (nickel): 0 to 1.0000 mass%, B (boron): 0 to 0.0100 mass%, Mg (magnesium): 0 to 0.0500 mass%, Zr (zirconium): 0 to 0.5 mass%, W (tungsten): 0 to 0.200 mass%, and Ca + REM: 0 to 0.1 mass%, with the remainder being Fe (iron) and impurities. The remainder may consist of Fe (iron) and impurities. Impurities refer to components contained in the raw materials or components mixed in during the manufacturing process, and not components that were intentionally included. Base steel sheets having such a chemical composition are preferable in that they have excellent formability.

[0065] In laser welding, it is preferable to form the weld metal 30 using an austenitic filler wire. Using an austenitic filler wire has the advantage of improving corrosion resistance compared to using a ferritic filler wire.

[0066] The chemical composition of austenitic filler wires is as follows: C (carbon): greater than 0% by mass and 0.090% by mass or less, Si (silicon): greater than 0% by mass and 2.0% by mass or less, Mn (manganese): greater than 0% by mass and 3.0% by mass or less, P (phosphorus): greater than 0% by mass and 0.05% by mass or less, S (sulfur): greater than 0% by mass and 0.050% by mass or less, Cr (chromium): 11.00 to 30.00% by mass, Ti (titanium): greater than 0% by mass and 0.100% by mass or less, V (vanadium): greater than 0% by mass and 0.10% by mass or less, W (tungsten): greater than 0% by mass and 0.20% by mass or less, Mo (molybdenum): greater than 0% by mass and 5.00% by mass or less, Nb (niobium): greater than 0% by mass and 1.000% by mass or less, Ni (nickel): 6.00 to 30.00% by mass. Preferably, the mixture contains Cu (copper): greater than 0% by mass and 5,000% by mass or less, Sn (tin): greater than 0% by mass and 0.100% by mass or less, Co (cobalt): greater than 0% by mass and 3,000% by mass or less, Al (aluminum): greater than 0% by mass and 0.100% by mass or less, Mg (magnesium): greater than 0% by mass and 0.0500% by mass or less, B (boron): greater than 0% by mass and 0.0100% by mass or less, N (nitrogen): greater than 0% by mass and 0.1000% by mass or less, and O (oxygen): greater than 0% by mass and 0.1000% by mass or less, with the remainder being Fe (iron) and impurities. The remainder may consist of Fe (iron) and impurities.

[0067] Furthermore, the chemical composition of the filler wire may include As, Zr, Hf, Sb, Sr, or REM in an amount of 1.0% by mass or less.

[0068] The chemical composition of the filler wire is measured using ICP (Inductively Coupled Plasma) emission spectroscopy in accordance with JIS G 1258-1:2014. However, carbon (C), sulfur (S), and nitrogen (N) are measured by well-known gas analysis methods.

[0069] In the joining process, the supply rate of the filler wire is preferably 0.1 to 3.0 times the welding rate. If there is too much filler, the excess will be high. If there is too little filler, corrosion resistance cannot be ensured. Therefore, the supply rate of the filler wire is preferably 0.1 to 3.0 times the welding rate. More preferably, the supply rate of the filler wire is 0.3 to 1 times the welding rate.

[0070] In addition, if the welding rate is too slow, the cycle time will be extended, resulting in cost increase. If the welding rate is too fast, spatter will increase, and the cost of spatter removal will be high. Therefore, the welding rate is preferably 0.5 to 20 m / min. More preferably, the welding rate is 2 to 10 m / min.

[0071] If the diameter of the filler wire is too thin, the tip of the wire may shake during welding and the laser light may not hit it, resulting in some filler remaining unmolten. If the diameter of the filler wire is too thick, the heat capacity of the wire will be large, and some may remain unmolten even when the laser light hits it. Therefore, the diameter of the filler wire is more preferably 0.6 to 2 mm in diameter. More preferably, the diameter of the filler wire is 0.8 to 1.2 mm in diameter.

[0072] The dilution rate of the Ni-plated steel sheet and the filler wire is the ratio of the volume of the filler in the volume of the weld metal. That is, the dilution rate can be expressed by the following formula. Dilution rate = volume of filler (mm ３ ) / volume of weld metal (mm ３ ) Here, each item is as follows. Volume of weld metal (mm ３ / s) = volume of filler supplied (mm ３ / s) + volume of steel sheet melted (mm ３ / s) Volume of filler supplied (mm ３ / s) = (diameter of filler wire (mm) / 2) ２ × π × supply rate of filler wire (mm / s) Supply rate ratio = supply rate of filler wire (mm / s) / welding rate (mm / s)

[0073] The laser welding described above forms a weld metal 30 that joins the lid 11 and the body 12. In this embodiment, the weld metal 30 satisfies [Cr] + 4 × [Ni] ≥ 5.00, where [Cr] is the average amount of Cr and [Ni] is the average amount of Ni in the weld metal. Therefore, the electrolyte resistance of the weld metal 30 can be improved.

[0074] The above method makes it possible to manufacture a battery case 1 in which the length of the body 12 in the direction perpendicular to the lid 11 is long. For example, when manufacturing a battery case that is long in the pressing direction by deep drawing using a press, it is necessary to use a dedicated mold for each pressing process. However, according to the manufacturing method of this embodiment, this is not necessary, and the radius of the corners of the body 22 can be made smaller by bending and welding. Such a battery case has the advantage of having a larger volume. When the body 12 is formed by the above method, there is at least one welded joint in the body 12.

[0075] (Joining Process) In the joining process, the lid 11 and the body 12 are joined by crimping. Specifically, the lid 11 and the body 12 are placed in predetermined positions, and the ends of the lid 11 and the body 12 are crimped. A common double crimping method can be used for crimping. That is, the crimped structure can be formed by wrapping the portion near the end of the lid 11 around the portion near the end of the body 12 and pressing them together. Double crimping allows the materials constituting the lid 11 and the materials constituting the body 12 to overlap, creating a sealed structure.

[0076] The battery according to the above embodiment may be a battery cell. A battery cell is the smallest unit of a battery in a battery module. A battery module is constructed by electrically connecting multiple battery cells. Multiple battery modules can be further electrically connected to form a battery pack. A battery pack can also be constructed by electrically connecting a large number of battery cells without constructing a battery module. Battery modules or battery packs are used, for example, as a power source for electric vehicles. However, the use of battery modules or battery packs in electric vehicles is not essential. It is also possible to mount a large number of battery cells in an electric vehicle without constructing a module or pack.

[0077] In other words, the battery case according to the above-described embodiment can be preferably used as a battery cell case. In particular, the battery case according to the above-described embodiment can be preferably used as a prismatic lithium-ion battery cell case. When used as a battery cell case, the battery case contains a positive electrode active material, a separator, a negative electrode active material, and an electrolyte.

[0078] Furthermore, when the battery case according to the above embodiment is used as a battery cell case, positive lead, negative lead, positive terminal, negative terminal, etc. may be provided. When the battery case according to the above embodiment is used as a battery cell case, the battery cell case body may be used as a negative terminal case. When the battery case according to the above embodiment is used as a battery cell case, it may be a neutral case (neutral can) insulated from the positive terminal and negative terminal. A neutral case (neutral can) means a case (can) that is not subjected to any potential.

[0079] A battery case can be manufactured by the battery case manufacturing method according to the embodiment described above.

[0080] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

[0081] In this embodiment, a battery was created using a battery case as a battery cell case, which had welded metal on the body and whose lid and body were joined by crimping, and its performance was evaluated.

[0082] In the following examples, the following steel sheets (base steel sheets) were prepared as the base material for the Ni-plated steel sheets. For the lid and body, aluminum-killed steel with a thickness of 0.3 mm (manufactured by Nippon Steel Corporation, S6 in Table 1), general cold-rolled steel sheet SPCC with a thickness of 0.2 to 0.3 mm (manufactured by Nippon Steel Corporation, S7 and S8 in Table 1), and Nb-SULC steel with a thickness of 0.2 to 1.4 mm (manufactured by Nippon Steel Corporation, S1 to S5 and W1 in Table 1) were prepared.

[0083] The above-mentioned base steel sheet was subjected to Ni-based plating or Ni-W-based plating to produce Ni-plated steel sheet for use as the fuselage material. The plating conditions for each plating are as follows. Separately, the main constituent components of the plating layer for the following two types of Ni-based plating were identified using the method described above, and it was confirmed that they were Ni.

[0084] [Ni-based plating] A Ni-based plating layer was formed on a steel sheet by electroplating using a plating bath containing the following components. After plating, heat treatment was performed under the following conditions: Ni plating bath: Watts bath containing 250 g / L nickel sulfate, 50 g / L nickel chloride, and 30 g / L boric acid (pH = 3.0) Plating bath temperature: 50°C Current density: 20 A / dm ２ Heat treatment conditions: 750-800°C x 20 seconds

[0085] [Ni-W Plating] Using the Ni plating bath described above and the Ni-W alloy plating bath described below, a Ni-W plating layer was formed on a base steel sheet by electroplating Ni followed by Ni-W alloy plating. After plating, heat treatment was performed under the following conditions: Ni-W alloy plating bath: sodium tungstate 65 g / L, nickel sulfate 50 g / L, diammonium hydrogen citrate 100 g / L, sodium formate 13 g / L Plating bath temperature: 50°C Current density: 20 A / dm ２ Heat treatment conditions: 750-800°C x 20 seconds

[0086] The battery case body was created by bending and welding each of the Ni-plated steel sheets shown in Table 1. The Ni-plated steel sheet before bending had dimensions of 240 mm x 300 mm. The formed shape of the body was 300 mm (depth) x 20 mm (width) x 100 mm (height). The opening of the body was 20 mm x 100 mm. Table 1 also shows the chemical composition of the base steel sheet of the Ni-plated steel sheet (the remainder includes Fe and impurities).

[0087] In Table 1, the notation S-Ni in the plating type column means that the plating layer has an Fe-Ni alloy layer between the Ni-based plating layer and the base steel material. The notation Ni-W in the plating type column means that the plating layer has a Ni-W-based plating layer on top of the S-Ni layer.

[0088] The plating thickness was measured on both the front and back surfaces of the Ni-plated steel sheet using the method described above.

[0089]

[0090] For the bent Ni-plated steel sheets, the ends of the sheets were joined together by laser welding along the direction of the depth of the fuselage. The laser welding of the fuselage was adjusted to the following conditions to ensure complete penetration: Continuous wave power: 0.8 to 6.4.0 kW Speed: 0.250 to 20.05.0 m / min Focus shift: 0 to 10 mm (focus diameter at JF: 0.6 mm) Shielding gas: Ar

[0091] A filler was used for laser welding. The steel grade of the filler is shown in Table 2. The remainder of the chemical composition in Table 2 includes Fe and impurities. The diameter of the filler wire was 1.2 mm.

[0092] The dilution ratios for the Ni-plated steel sheet and filler wire were as shown in Tables 4A and 4B.

[0093]

[0094] The SUS1 and SUS2 sheet materials shown in Table 3 were processed into predetermined shapes to create the battery case lid.

[0095]

[0096] Using the above-mentioned lid and body, each battery case was fabricated using the combinations of body and filler steel grades shown in Tables 4A and 4B. SUS1 was used for Experimental Examples 1-30, and SUS2 was used for Experimental Examples 31-58. A battery cell case was created by housing a battery inside the battery case. The battery fabrication method is as follows.

[0097] (Battery Fabrication) ・Positive electrode plate Lithium cobalt oxide was used as the positive electrode active material. This was mixed with acetylene black and polyvinylidene fluoride (PVDF) in a mass ratio of 10:10:1, then applied to an Al foil as an aqueous dispersion and dried. This was rolled to a predetermined thickness and cut to a predetermined size to form the positive electrode plate. ・Negative electrode plate Amorphous carbon was used as the negative electrode active material. This was dry-mixed with acetylene black, which is a conductive material, and then N-methyl-2-pyrrolidone (NMP), which is polyvinylidene fluoride dissolved in it, was uniformly dispersed in the mixture to create a paste with a mass ratio of carbon:acetylene black:PVDF = 88:5:7. This was applied to a Cu foil, dried, rolled to a predetermined thickness, and then cut to a predetermined size to form the negative electrode plate. ・Separator A polyethylene microporous membrane was used as the separator. - Electrolyte: The electrolyte used was a solution prepared by mixing ethylene carbonate and diethyl carbonate in a 1:1 volume ratio, to which 1 mol / L of lithium hexafluorophosphate was added (1M-LiPF6 EC / DEC (1 / 1)).

[0098] The electrode group, wound with a separator in between the positive and negative electrode plates, was flattened to fit into the body of the battery cell case. The positive electrode plate was welded to an Al lead, and the negative electrode plate to a Ni lead. The Al lead was welded to the positive terminal on the cover, and the Ni lead was welded to the negative terminal on the cover.

[0099] The lid and body were joined using a double seam method.

[0100] The inside of the battery was dried in an atmosphere with a dew point of -76°C to remove moisture. The electrolyte was then injected through the injection port in the same atmosphere. The battery was then charged to 3.6-4.2V in the same atmosphere. This procedure electrolyzed any remaining moisture inside the battery. After that, the injection port was closed with a stopper.

[0101]

[0102]

[0103] The following evaluations were performed on each of the obtained battery cases. The results are shown in Tables 4A and 4B.

[0104] (Composition of Weld Metal) The average Cr content and average Ni content of the weld metal were measured by the following method. From the battery cell case, weld metal used to join the lid and the body, and weld metal used to form the body were cut out, and samples of each weld metal were taken. Using an emission spectrometer (Shimadzu Corporation: ICPS-8100), the components of these samples were measured at five points, and the arithmetic mean was taken as the average Cr content or average Ni content.

[0105] When the average Cr content of the weld metal is [Cr] and the average Ni content is [Ni], the value of [Cr] + 4 × [Ni] ...Equation 1 was used as the corrosion resistance index of the weld metal.

[0106] (Leaching Test) After sealing the injection port, the battery cell case was held at 80°C for 750 hours. After holding, a portion of the battery case was disassembled in an atmosphere with a dew point of -76°C, and the electrolyte was collected using a pipette or similar instrument. The amount of metal leached from the electrolyte was analyzed using ICP-MS (model: Agilent 7700x, manufactured by Agilent Technologies, Inc.). If the Fe component in the solution was 75 ppm or less, it was marked as ○ (Good), and if it was greater than 75 ppm, it was marked as × (Bad).

[0107] As can be seen from the results in Tables 4A and 4B, in the examples that satisfy the requirements of the present invention, the amount of Fe component dissolved in the solution was trace, less than 75 ppm, and the electrolyte resistance was good.

[0108] The battery case according to the present invention and the battery using the battery case according to the present invention have high electrolyte resistance. Furthermore, the method for manufacturing the battery case according to the present invention can provide a battery case with high electrolyte resistance. For this reason, the present invention is extremely useful in industry.

[0109] 1 Battery case 11 Lid 12 Body 12a, 12b, 12c, 12d Side 30 Welded metal

Claims

1. A battery case comprising a lid and a body, wherein the lid and the body are joined by crimping, the lid is made of any of stainless steel, plated steel, painted steel, or aluminum, the body includes a Ni-plated steel having a base steel material and a Ni-based plating layer, the body includes at least one weld metal extending in a direction intersecting the lid, and when the average Cr amount of the weld metal is [Cr] and the average Ni amount of the weld metal is [Ni], the equation [Cr] + 4 × [Ni] ≥ 5.00 is satisfied.

2. The battery case according to claim 1, characterized in that the length of the body in the direction perpendicular to the lid is 1.5 times or more the length of the lid in the longitudinal direction.

3. The battery case according to claim 1, characterized in that the lid is made of a nickel-plated steel material having a base steel material and a nickel-based plating layer.

4. The battery case according to any one of claims 1 to 3, characterized in that the thickness of the Ni-plated steel material is 0.1 to 1.4 mm.

5. The battery case according to any one of claims 1 to 3, characterized in that the thickness of the Ni-based plating layer is 0.1 to 10.0 μm.

6. The basis weight of the Ni-based plating layer is 2.0 to 89.0 g / m². ２ The battery case according to any one of claims 1 to 3, characterized in that it is the battery case according to any one of claims 1 to 3.

7. The battery case according to any one of claims 1 to 3, characterized in that it has an Fe-Ni alloy layer between the Ni-based plating layer and the base steel material.

8. The battery case according to any one of claims 1 to 3, characterized in that the excess height of the weld metal is 50% or less of the thickness of the Ni-plated steel material.

9. The battery case according to any one of claims 1 to 3, characterized in that it is a neutral can.

10. A battery comprising the battery case described in any one of claims 1 to 3.

11. A method for manufacturing a battery case comprising a lid and a body, comprising: a lid forming step of forming the lid by processing one of stainless steel, plated steel, painted steel, or aluminum; a body forming step of forming the body comprising at least one weld metal by welding a base steel material and plated steel material having a Ni-based plating layer; and a joining step of crimping the lid and the body together, wherein when the average Cr amount of the weld metal is [Cr] and the average Ni amount of the weld metal is [Ni], the formula [Cr] + 4 × [Ni] ≥ 5.00 is satisfied.

12. The method for manufacturing a battery case according to claim 11, characterized in that the weld metal is formed using an austenitic filler wire.

13. The method for manufacturing a battery case according to claim 11 or 12, characterized in that the weld metal is formed using a filler wire, and the supply speed of the filler wire is 0.1 to 3.0 times the welding speed.

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