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

Abstract

The present invention provides a battery case (1) comprising a lid (11) and a body (12), wherein the lid (11) and the body (12) are joined by crimping, the lid (11) is made of any of stainless steel, plated steel, painted steel, or aluminum, the body (12) includes a base steel material and a Ni-plated steel material having a Ni-based plating layer, the body (12) includes at least one weld metal (30) extending in a direction intersecting the lid (11), and when the average Cr content of the weld metal (30) is [Cr] and the average Ni content of the weld metal (30) is [Ni], the equation [Cr] + 4 × [Ni] ≥ 5.00 is satisfied.

Description

[Technical Field]

[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, and the contents of that application are incorporated herein by reference. [Background technology]

[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. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-097900 [Overview of the project] [Problems that the invention aims to solve]

[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 the molding process 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 areas of battery cases using plated steel sheets, it is thought that the improvement in corrosion resistance (electrolyte resistance) is less pronounced compared to the base material that makes up the plated lid (and bottom plate) and body. Therefore, under extremely harsh conditions, there is a possibility that the welded areas 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 areas after the lid and body of the battery case have been laser-welded.

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

[0007] (1) A battery case according to one aspect of the present invention is A battery case including a lid and a body, The lid and the body are joined together by crimping, The aforementioned lid is made of one of the following materials: stainless steel, plated steel, painted steel, or aluminum. The fuselage includes a base steel material and a Ni-plated steel material having a Ni-based plating layer. The body includes at least one weld metal extending in a direction intersecting the lid, When the average Cr content of the weld metal is [Cr] and the average Ni content of the weld metal is [Ni], the following conditions are met: [Cr] + 4 × [Ni] ≥ 5.00. It is characterized by the following: (2) In the battery case described in (1) above, The length of the body in the 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 cover may be made of a nickel-plated steel material having a base steel material and a nickel-based plating layer. (4) In the battery case described in any one of the above items (1) to (3), 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 the above items (1) to (4), 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 the above items (1) to (5), The basis weight of the aforementioned Ni-based plating layer is 2.0 to 89.0 g / m². 2 That's fine. (7) In the battery case described in any one of the above items (1) to (6), An Fe-Ni alloy layer may be present between the Ni-based plating layer and the base steel material. (8) In the battery case described in any one of the above items (1) to (7), 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 the above items (1) to (8) is: A neutral can is also acceptable. (10) A battery according to one aspect of the present invention is a battery comprising the battery case described in any one of the above items (1) to (9). (11) A method for manufacturing a battery case according to one aspect of the present invention is: A method for manufacturing a battery case, which includes a lid and a body, A lid forming step involves processing one of the following materials—stainless steel, plated steel, painted steel, or aluminum—to form the lid, A fuselage forming step involves welding a plated steel material having a base steel material and a Ni-based plating layer to form the fuselage including at least one weld metal, A joining step of joining the lid and the body by crimping them together, Includes, When the average Cr content of the weld metal is [Cr] and the average Ni content of the weld metal is [Ni], the following conditions are met: [Cr] + 4 × [Ni] ≥ 5.00. It is characterized by the following. (12) In the method for manufacturing the battery case according to (11) above, The welding metal may be formed using an austenitic filler wire. (13) In the method for manufacturing the battery case according to (11) or (12) above, The welding metal is formed using a filler wire, The supply speed of the filler wire may be 0.1 to 3.0 times the welding speed.

Advantages of the Invention

[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. Further, according to the method for manufacturing the battery case according to the present invention, a battery case with high electrolyte resistance can be provided.

Brief Description of the Drawings

[0009] [Figure 1] It is a schematic perspective view for explaining a battery case according to an embodiment of the present invention. [Figure 2] It is a schematic cross-sectional view for explaining an embodiment of a welded portion formed on the body. [Figure 3] It is a schematic cross-sectional view for explaining another embodiment of a welded portion formed on the body. [Figure 4] It is a schematic cross-sectional view for explaining a winding structure. [Figure 5] It is a schematic perspective view for explaining a modified example of a battery case according to an embodiment of the present invention. [Figure 6] It is a diagram for explaining an example of a method for manufacturing a battery case according to an embodiment of the present invention. [Figure 7] It is a diagram for explaining another example of a method for manufacturing a battery case according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0010] The 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. Furthermore, in this specification, numerical ranges represented using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved.

[0011] In the following embodiments, "steel material" includes steel plates, parts obtained by machining 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 obtained by machining aluminum plates into shapes other than flat plates, and steel plates formed by joining different types of aluminum plates. A battery case refers to a case that has a sealed structure to prevent the contents, such as electrolyte, contained within the case from leaking out of the battery case.

[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 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. 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 used to make 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 Ni-plated steel material used for the body 12, as described later, may also 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 into 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 that makes up the lid 11, A1000 series or A3000 series is preferred. For example, A3003 can be used as the aluminum material that makes up 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 lid] 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" 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, with the body 12 in between, and the lid 11 and the bottom cover 14 are arranged so that their plate surfaces face each other.

[0022] [body] As illustrated in Figure 1, the body 12 is composed of opposing sides 12a and 12b, and opposing sides 12c and 12d. 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 AA 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 formation of a welded section containing the weld metal 30 on the side surface of the body 12 has the advantage of suppressing deformation of the Ni-plated steel material due to the thermal history during welding. 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. However, 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, as long as the battery case 1 can be sealed, the weld metal 30 may be formed on any side surface of the body 12, and the weld metal 30 may be formed across multiple sides.

[0030] In the example in Figure 1, the weld is located on the side surface 12a, and the Ni-plated steel material constituting the fuselage 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 fuselage 12 at their ends, the amount of Ni-based plating layer components of the Ni-plated steel material that dissolves into the weld metal 30 increases, which has the advantage of forming a highly corrosion-resistant weld metal 30.

[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 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 extent of the connection; as long as the battery case 1 can be sealed, the joining by crimping may be applied to only a portion of the connection. In addition, the outer circumference of the lid 11 (or bottom lid 14) may be provided with a raised portion that rises from the plate surface of the lid 11, and this raised portion may be joined to the body 12 by crimping.

[0034] [Weld metal] In the battery case 1 shown in Figure 1, a welded section containing weld metal 30 is formed on the body 12. In the battery case 1 of this embodiment, when the average amount of Cr in the weld metal 30 is [Cr] and the average amount of Ni 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 any five 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 end portion can be identified by its appearance. The average Ni content in the weld metal 30 is calculated using the same method as the average Cr content.

[0036] Weld metal 30 is the part 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 the metal that melted and solidified during welding. When filler is used during laser welding, the source of material for weld metal 30 is 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, oxygen and nitrogen from the air are incorporated into the weld metal 30, and unavoidable impurities may also be incorporated.

[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] 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): more than 0% by mass and 0.150% by mass or less, Si (silicon): greater than 0% by mass and less than or equal to 0.800% by mass. Mn (manganese): more than 0% by mass and not more than 1.00% by mass, P (phosphorus): more than 0% by mass and 0.05% by mass or less, S (sulfur): more than 0% by mass and 0.050% by mass or less, Mo (Molybdenum): 0-0.300 mass%, Cu (copper): 0~1.00% by mass, Ti (Titanium): 0-0.100 mass%, Al (aluminum): 0-0.10% by mass, Co (cobalt): 0-1,000 mass%, Nb (niobium): 0-0.100 mass%, N (nitrogen): 0~0.030% by mass, Sn (tin): 0~0.100% by mass, Cr (chromium): 0-0.40 mass%, Ni (nickel): 0-1.0000 mass%, B (Boron): 0-0.0100% by mass, Mg (Magnesium): 0-0.0500 mass%, Zr (Zirconium): 0-0.5% by mass, W (Tungsten): 0-0.200 mass%, Ca+REM: 0~0.1% by mass, Preferably, it contains [a certain substance], with the remainder being Fe (iron) and impurities. The remainder may consist of Fe (iron) and impurities. Impurities refer to components present in the raw materials or components that are introduced during the manufacturing process, and not components that were intentionally included. Steel sheets with such a chemical composition are preferable in that they have excellent formability.

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

[0040] It is more preferable that the carbon content of the base steel material (substrate) is greater than 0% by mass and less than or equal to 0.070% by mass. This has the advantage of further improving the formability of the nickel-plated steel material. Furthermore, since corrosion resistance is obtained by having a nickel-based plating layer on its surface, the base steel material may be made of a material other than stainless steel.

[0041] A nickel-based plating layer is provided on the surface of the base steel material that constitutes the nickel-plated steel material. The nickel-based plating layer is a plating layer whose main component is nickel. Specifically, the nickel-based plating layer is defined as the range in which the nickel concentration is 80% by mass or more when measured using GDS (Glow discharge optical emission spectrometry). The nickel-based plating layer is provided on at least the surface of the body 12 that faces inward into the battery case 1. The nickel-based plating layer may also be provided on both sides of the base steel material that constitutes the body 12.

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

[0043] A thickness of 0.1 to 10.0 μm is more preferable for the Ni-based plating layer. Increasing the thickness of the Ni-based plating layer improves electrolyte resistance but also increases costs. A thickness of 0.1 to 10.0 μm for the Ni-based plating layer offers the advantage of a good balance between electrolyte resistance and cost. The thickness of the Ni-based plating layer can be measured using a GDS device. Using the GDS device, the thickness of any five points on the plating layer is measured, and the arithmetic mean of these measurements is taken as the thickness of the Ni-based plating layer.

[0044] The basis weight of the Ni-based plating layer is 2.0 to 89.0 g / m². 2Alternatively, the basis weight of the Ni-based plating layer is measured by ICP emission spectrometry (ICP-OES). First, a predetermined area of ​​the Ni-based plating layer is dissolved in acid. Next, the total amount of Ni contained in the solution is quantitatively analyzed by ICP-OES. By dividing the total amount of Ni quantified by ICP-OES by the predetermined area, the basis weight per unit area can be determined. This makes it possible to improve the corrosion resistance of the base steel sheet while suppressing the cost increase caused by Ni plating.

[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 has a Ni concentration of 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. Furthermore, 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 it may be 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 any five 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 is measured at five points using the 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 producing a battery case that is lightweight and has excellent mechanical strength. The thickness of 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 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 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 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 addition, in the case of contact surfaces with cooling plates, the gap filler is reduced, which can lower 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, and includes 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 battery case manufacturing method 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 formation process) The lid 11 is formed by processing one of the following materials—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 formation process) In the battery case manufacturing method according to this embodiment, a nickel-plated steel material having a nickel-based plating layer on the surface of a base steel material is bent, and the ends of the bent nickel-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 with weld metal 30 by laser welding. 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): more than 0% by mass and 0.150% by mass or less, Si (silicon): greater than 0% by mass and less than or equal to 0.800% by mass. Mn (manganese): more than 0% by mass and not more than 1.00% by mass, P (phosphorus): more than 0% by mass and 0.05% by mass or less, S (sulfur): more than 0% by mass and 0.050% by mass or less, Mo (Molybdenum): 0-0.300 mass%, Cu (copper): 0~1.00% by mass, Ti (Titanium): 0-0.100 mass%, Al (aluminum): 0-0.10% by mass, Co (cobalt): 0-1,000 mass%, Nb (niobium): 0-0.100 mass%, N (nitrogen): 0~0.030% by mass, Sn (tin): 0~0.100% by mass, Cr (chromium): 0-0.40 mass%, Ni (nickel): 0-1.0000 mass%, B (Boron): 0-0.0100% by mass, Mg (Magnesium): 0-0.0500 mass%, Zr (Zirconium): 0-0.5% by mass, W (Tungsten): 0-0.200 mass%, Ca+REM: 0~0.1% by mass, Preferably, it contains [a certain component], 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 that are introduced during the manufacturing process and are not intentionally included. Steel sheets with 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): more than 0% by mass and 0.090% by mass or less, Si (silicon): greater than 0% by mass and less than or equal to 2.0% by mass. Mn (manganese): more than 0% by mass and 3.0% by mass or less, P (phosphorus): more than 0% by mass and 0.05% by mass or less, S (sulfur): more than 0% by mass and 0.050% by mass or less, Cr (chromium): 11.00~30.00 mass%, Ti (Titanium): More than 0% by mass and less than or equal to 0.100% by mass. V (Vanadium): Greater than 0% by mass and less than or equal to 0.10% by mass. W (Tungsten): More than 0% by mass and less than or equal to 0.20% by mass. Mo (Molybdenum): Greater than 0% by mass and 5.00% by mass or less. Nb (niobium): more than 0% by mass and not more than 1.000% by mass, Ni (Nickel): 6.00~30.00 mass%, Cu (copper): more than 0% by mass and 5.000% by mass or less, Sn (tin): more than 0% by mass and 0.100% by mass or less, Co (cobalt): greater than 0% by mass and less than or equal to 3,000% by mass. Al (aluminum): greater than 0% by mass and less than or equal to 0.100% by mass. Mg (Magnesium): Greater than 0% by mass and less than or equal to 0.0500% by mass. B (boron): more than 0% by mass and 0.0100% by mass or less, N (nitrogen): more than 0% by mass and 0.1000% by mass or less, It is preferable that the mixture contains more than 0% by mass of oxygen (O) and 0.1000% by mass or less, with the remainder being iron (Fe) and impurities. The remainder may consist of iron (Fe) 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 shall be measured using ICP (Inductively Coupled Plasma) emission spectroscopy in accordance with JIS G 1258-1:2014. However, carbon (C), sulfur (S), and nitrogen (N) shall be measured by well-known gas analysis methods.

[0069] In the joining process, the filler wire supply rate is preferably 0.1 to 3.0 times the welding rate. Too much filler results in excessive weld bead. Too little filler prevents proper corrosion resistance. Therefore, the filler wire supply rate should be 0.1 to 3.0 times the welding rate. More preferably, the filler wire supply rate should be 0.3 to 1 time the welding rate.

[0070] In addition, if the welding speed is too slow, the cycle time will be extended, resulting in increased costs. If the welding speed is too fast, spatter will increase, and costs will be incurred for spatter removal. Therefore, a welding speed of 0.5 to 20 m / min is preferable. More preferably, the welding speed is 2 to 10 m / min.

[0071] If the diameter of the filler wire is too thin, the tip of the wire may vibrate during welding and the laser light may not hit it, resulting in some of the filler remaining unmelted. If the diameter of the filler wire is too thick, the heat capacity of the wire will increase, and some of it may remain unmelted 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) = (Filler wire diameter (mm) / 2) 2 × π × Supply speed of filler wire (mm / s) Supply speed ratio = Supply speed of filler wire (mm / s) / Welding speed (mm / s)

[0073] By the laser welding described above, a weld metal 30 that joins the lid body 11 and the body 12 is formed. The weld metal 30 according to the present embodiment satisfies [Cr] + 4 × [Ni] ≥ 5.00 when the average Cr amount is [Cr] and the average Ni amount of the weld metal is [Ni]. Therefore, the electrolytic solution 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. As for the crimping method, a common double crimping method can be used. 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. With double crimping, the materials constituting the lid 11 and the materials constituting the body 12 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 embodiment can be preferably used as a battery cell case. In particular, the battery case according to the above embodiment can be preferably used as a prismatic lithium-ion battery cell case. When used as a battery cell case, the battery case contains the positive electrode active material, separator, negative electrode active material, and electrolyte.

[0078] Furthermore, when using the battery case according to the above embodiment as a battery cell case, positive lead, negative lead, positive terminal, negative terminal, etc. may be provided. When using the battery case according to the above embodiment as a battery cell case, the battery cell case body may be used as a negative electrode case with the negative electrode terminal. When using the battery case according to the above embodiment as a battery cell case, it may be used as a neutral case (neutral can) insulated from the positive electrode terminal and the negative electrode terminal. A neutral case (neutral can) means a case (can) that has no potential applied to it.

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

[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, in which the body has welded metal and the lid and body are 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 (substrate) for the Ni-plated steel sheets. For the lid and body, we prepared aluminum-killed steel with a plate thickness of 0.3 mm (manufactured by Nippon Steel Corporation, S6 in Table 1), general cold-rolled steel sheet SPCC with a plate 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 plate thickness of 0.2 to 1.4 mm (manufactured by Nippon Steel Corporation, S1 to S5 and W1 in Table 1).

[0083] The above-mentioned base steel sheet was subjected to either a Ni-based plating or a Ni-W-based plating to produce a 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 nickel-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 conditions described below. 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℃ Current density: 20A / 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, the base steel sheet was plated in the order of electroplating Ni followed by Ni-W alloy plating to form a Ni-W plating layer. After plating, heat treatment was performed under the conditions described below. Ni-W alloy plating bath: Sodium tungstate 65g / L, nickel sulfate 50g / L, diammonium hydrogen citrate 100g / L, sodium formate 13g / L Plating bath temperature: 50℃ Current density: 20A / 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 for the Ni-plated steel sheet (the remainder being 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] [Table 1]

[0090] For the bent nickel-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 Output: 0.8~6.4.0kW Speed: 02.50~20.05.0m / min Focus shift: 0-10mm (Gathering diameter with JF: 0.6mm) 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] [Table 2]

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

[0095] [Table 3]

[0096] Using the lid and body described above, 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. The battery was placed inside the battery case to create a battery cell case. The battery was created as follows:

[0097] (Battery construction) • Positive plate Lithium cobalt oxide was used as the positive electrode active material. Acetylene black and polyvinylidene fluoride (PVDF) were mixed with this in a mass ratio of 10:10:1, and then coated onto aluminum 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 plate Amorphous carbon was used as the negative electrode active material. This was dry-mixed with acetylene black, 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 paste 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 (1M-LiPF6 EC / DEC(1 / 1)) prepared by mixing ethylene carbonate and diethyl carbonate in a 1:1 volume ratio and adding 1 mol / L of lithium hexafluorophosphate.

[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] [Table 4A]

[0102] [Table 4B]

[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 using 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], [Cr] + 4 × [Ni] ... Equation 1 This value was used as the corrosion resistance index for 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 tool. The amount of metal leached from the electrolyte was analyzed using an ICP-MS (model: Agilent 7700x, manufactured by Agilent Technologies, Inc.). A score of ○ (Good) was given if the Fe component in the solution was 75 ppm or less, and × (Bad) if it was greater than 75 ppm.

[0107] As can be seen from the results in Tables 4A and 4B, in the examples that met 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. [Industrial applicability]

[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. [Explanation of Symbols]

[0109] 1 Battery case 11 Lid 12 Torso 12a, 12b, 12c, 12d side 30 Weld metal

Claims

1. A battery case including a lid and a body, The lid and the body are joined together by crimping, The aforementioned lid is made of one of the following materials: stainless steel, plated steel, painted steel, or aluminum. The fuselage includes a Ni-plated steel material 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, When the average Cr content of the weld metal is [Cr] and the average Ni content of the weld metal is [Ni], the following conditions are met: [Cr] + 4 × [Ni] ≥ 5.

00. A battery case characterized by the following features.

2. 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. The battery case according to feature 1.

3. The cover is made of Ni-plated steel material having a base steel material and a Ni-based plating layer. The battery case according to feature 1.

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

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

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

7. A Fe-Ni alloy layer is provided between the Ni-based plating layer and the base steel material. A battery case according to any one of claims 1 to 3.

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

9. It is a neutral can. A battery case according to any one of claims 1 to 3.

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

11. A method for manufacturing a battery case, which includes a lid and a body, A lid forming step involves processing one of the following materials—stainless steel, plated steel, painted steel, or aluminum—to form the lid, A fuselage forming step involves welding a plated steel material having a base steel material and a Ni-based plating layer to form the fuselage including at least one weld metal, A joining step of joining the lid and the body by crimping them together, Includes, When the average Cr content of the weld metal is [Cr] and the average Ni content of the weld metal is [Ni], the following conditions are met: [Cr] + 4 × [Ni] ≥ 5.

00. A method for manufacturing a battery case, characterized by the following features.

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

13. The weld metal is formed using a filler wire. The feed rate of the filler wire is 0.1 to 3.0 times the welding rate. A method for manufacturing a battery case according to claim 11 or 12, characterized by the above.

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