Surface treated steel sheet, method for producing surface treated steel sheet, and method for producing battery component

Abstract

A surface treated steel sheet according to one embodiment of the present invention comprises: a base steel sheet; a Ni-containing layer disposed on the surface of the base steel sheet; and a Ni-W alloy layer disposed on the surface of the Ni-containing layer, wherein the Ni-containing layer has an Fe diffusion alloy layer and the Ni-W alloy layer is porous. A method for producing a surface treated steel sheet according to another embodiment of the present invention comprises: a step for performing Ni electroplating on a base steel sheet; a step for pickling the base steel sheet having the Ni plating layer; a step for performing Ni-W alloy electroplating on the base steel sheet having the Ni plating layer; and a step for annealing the base steel sheet having the Ni plating layer and the Ni-W alloy layer disposed thereon, wherein a 70-100 g / L sulfuric acid bath serves as a pickling bath during the pickling, the time for which the base steel sheet having the Ni plating layer is immersed in the bath during the pickling is 25-35 seconds, the annealing temperature during the annealing is 630-860 °C, and the annealing time during the annealing is 10-180 seconds.

Description

Surface-treated steel sheet, method for manufacturing surface-treated steel sheet, and method for manufacturing battery components

[0001] The present invention relates to a surface-treated steel sheet, a method for manufacturing a surface-treated steel sheet, and a method for manufacturing a battery component.

[0002] Ni-plated steel sheets have been used as surface-treated steel sheets for battery cans. Due to the excellent chemical stability of Ni, Ni-plated steel sheets are used for various battery containers, such as battery cans for alkaline manganese dry batteries, lithium ion batteries, and nickel-metal hydride batteries.

[0003] In recent years, Ni—W alloy-plated steel sheets, which are mainly composed of an alloy of Ni and W, have also begun to be used as materials for battery cans, etc. Examples of Ni—W alloy-plated steel sheets are the steel sheets described in Patent Documents 1 to 4.

[0004] Patent Document 1 discloses a plated steel sheet for battery containers, characterized in that an iron-nickel alloy layer, a nickel layer, and a nickel-tungsten alloy layer are formed in this order from below on the side of the steel sheet that will become the inner surface of the battery container.

[0005] Patent Document 2 discloses a Ni-containing surface-treated steel sheet for containers to be formed by press forming, which includes a steel sheet having a first surface that will become the outside of the container after the press forming, a Ni-containing layer disposed on the first surface of the steel sheet, and a Ni-W alloy plating layer disposed on the Ni-containing layer. The Ni-containing layer has an Fe-Ni diffusion alloy layer, and the amount of Ni contained in the Ni-containing layer is 5 g / m ２ More than 89g / m ２ the thickness of the Ni—W alloy plating layer is 0.02 μm or more and 2 μm or less; and the W concentration in the Ni—W alloy plating layer is, in mass %, 10% or more and 65% or less.

[0006] Patent Document 3 discloses a steel sheet for a non-aqueous electrolyte secondary battery case, which includes a steel sheet and a Ni—W—Fe alloy plating layer formed on the surface of the steel sheet, which contains a Ni—W—Fe alloy, and which becomes the inner surface of the non-aqueous electrolyte secondary battery case.

[0007] Patent Document 4 discloses a steel sheet for use in battery cans of inside-out alkaline batteries, characterized in that the steel sheet has a plating layer selected from nickel-tungsten (Ni-W) and nickel-cobalt-tungsten (Ni-Co-W) alloys on the surface of one main surface of a base material made of a plate-like steel material, and the plating layer has irregularities on the surface formed by elution of the tungsten.

[0008] JP 2007-51325 A International Publication No. 2012 / 137823 International Publication No. 2017 / 006834 Japanese Patent Application Laid-Open No. 2020-155202

[0009] A tab is resistance-welded to the battery can. The tab is typically a thin plate made of a material with low electrical resistance, such as nickel or copper. Because the tab has low electrical resistance and is thin, it is very difficult to resistance-weld the tab to the battery can. This is because resistance heating is unlikely to occur in the tab during resistance welding.

[0010] Increasing the welding current value can increase the amount of resistance heat generated. However, resistance welding using a large current can cause holes in thin tabs, rendering them unusable. Therefore, there is a strong demand for surface-treated steel sheets for battery cans that can reduce the appropriate current range when resistance welding tabs.

[0011] The appropriate current range is the range of welding current values ​​that allows resistance welding without causing welding defects. Normally, a welding current below the lower limit of the appropriate current range cannot melt the surface-treated steel sheet and the tab, which are the welding base material, and cannot form a nugget that joins the two. On the other hand, a welding current above the upper limit of the appropriate current range will damage the welding base material.

[0012] In Patent Document 1, suppression of contact resistance and improvement of discharge characteristics are addressed as issues, but no particular consideration is given to the weldability between the plated steel sheet and the tab.

[0013] In Patent Document 2, the improvement of corrosion resistance after press forming is considered to be an issue, but no particular consideration is given to the weldability between the plated steel sheet and the tab.

[0014] In Patent Document 3, the problem to be solved is to suppress deterioration of battery performance and corrosion of the case due to metal elution when the potential of the battery case increases, but no particular consideration is given to the weldability between the plated steel sheet and the tab.

[0015] In Patent Document 4, the improvement of the high-load discharge performance and long-term storage performance of the steel sheet is addressed as an issue, but no particular consideration is given to the weldability between the plated steel sheet and the tab.

[0016] In view of the above circumstances, an object of the present invention is to provide a surface-treated steel sheet that can reduce the appropriate current range when resistance welding battery tabs without impairing workability, and a manufacturing method thereof.

[0017] The gist of the present invention is as follows.

[0018] (1) A surface-treated steel sheet according to one aspect of the present invention comprises a base steel sheet, a Ni-containing layer disposed on a surface of the base steel sheet, and a Ni—W alloy layer disposed on the surface of the Ni-containing layer, wherein the Ni-containing layer has an Fe-diffused alloy layer, and the Ni—W alloy layer is porous. (2) Preferably, in the surface-treated steel sheet described in (1) above, the Ni—W alloy layer has an average W concentration of 10 to 45 mass%. (3) Preferably, in the surface-treated steel sheet described in (1) or (2) above, the Ni—W alloy layer has a thickness of 0.01 to 2.0 μm. (4) Preferably, in the surface-treated steel sheet described in any one of (1) to (3) above, the Ni coating weight contained in the Ni-containing layer and the Ni—W alloy layer is 1.8 to 35.6 g / m ２ (5) Preferably, in the surface-treated steel sheet according to any one of (1) to (4) above, the thickness of the Fe diffusion alloy layer is 0.1 to 3.0 μm. (6) Preferably, in the surface-treated steel sheet according to any one of (1) to (5) above, only a part of the Ni-containing layer is the Fe diffusion alloy layer. (7) Preferably, in the surface-treated steel sheet according to any one of (1) to (6) above, the entire Ni-containing layer is the Fe diffusion alloy layer, and only a part of the Ni-W alloy layer is the Fe diffusion alloy layer.

[0019] (8) A method for producing a surface-treated steel sheet according to another aspect of the present invention includes the steps of electrolytically Ni-plating a base steel sheet, pickling the base steel sheet having the Ni-plated layer, electrolytically Ni-W alloy-plating the base steel sheet having the Ni-plated layer, and annealing the base steel sheet having the Ni-plated layer and a Ni-W alloy layer disposed thereon, wherein the pickling bath is a 70 to 100 g / L sulfuric acid bath, the base steel sheet having the Ni-plated layer is immersed in the bath for 25 to 35 seconds, the annealing temperature is 630 to 860°C, and the annealing time is 10 to 180 seconds.

[0020] (9) A method for manufacturing a battery component according to another aspect of the present invention includes a step of resistance welding a tab and the surface-treated steel sheet according to (1) or (2). (10) Preferably, in the method for manufacturing a battery component according to (9), a welding voltage in the resistance welding is set to 2.0 V to 3.5 V, and a current application time in the resistance welding is set to 1.0 ms to 10.0 ms.

[0021] According to the present invention, it is possible to provide a surface-treated steel sheet and a manufacturing method thereof that can reduce the appropriate current range when resistance welding battery tabs without impairing workability.

[0022] 1 is a schematic cross-sectional view of an example of a surface-treated steel sheet according to an embodiment of the present invention, and an enlarged view of a Ni—W alloy layer. 2 is a schematic cross-sectional view of another example of a surface-treated steel sheet according to an embodiment of the present invention. 3 is a TEM observation photograph of an example of a Ni—W alloy layer of a surface-treated steel sheet according to an embodiment of the present invention. 4 is a TEM observation photograph of an example of a Ni—W alloy layer of a surface-treated steel sheet according to an embodiment of the present invention. 5 is a flowchart illustrating an example of a method for manufacturing a surface-treated steel sheet according to an embodiment of the present invention.

[0023] (1. Surface-treated steel sheet 1) As shown in FIG. 1 etc., a surface-treated steel sheet 1 according to one aspect of the present invention comprises a base steel sheet 11, a Ni-containing layer 12 disposed on the surface of the base steel sheet 11, and a Ni—W alloy layer 13 disposed on the surface of the Ni-containing layer 12, wherein the Ni-containing layer 12 has an Fe-diffused alloy layer 14, and the Ni—W alloy layer 13 is porous. The surface-treated steel sheet 1 according to this embodiment will be described in detail below. Note that the entire plating layer including the Ni-containing layer 12 and the Ni—W alloy layer 13 may be simply referred to as the "plating layer".

[0024] (Base steel plate 11) The surface-treated steel plate 1 has a base steel plate 11. The base steel plate 11 is a steel plate that serves as a substrate for the surface-treated steel plate 1. The components, plate thickness, metal structure, etc. of the base steel plate 11 are not particularly limited and can be appropriately selected depending on the application of the surface-treated steel plate 1.

[0025] (Ni-containing layer 12) The surface-treated steel sheet 1 has a Ni-containing layer 12 disposed on the surface of the base steel sheet 11. The Ni-containing layer 12 is a layer containing Ni provided on the surface of the base steel sheet 11. The Ni-containing layer 12 may be provided on only one surface of the base steel sheet 11, or on both surfaces.

[0026] (Ni—W alloy layer 13) The surface-treated steel sheet 1 further has a Ni—W alloy layer 13 disposed on the surface of the Ni-containing layer 12. The Ni—W alloy layer 13 is an alloy plating layer containing Ni as a main component and further containing W. The Ni—W alloy plating is harder than Ni. By analyzing the component distribution of the plating layer using glow discharge optical emission spectroscopy, which is an analytical method capable of measuring the distribution of chemical components in the depth direction from the surface of the plating layer, it is possible to distinguish between the Ni—W alloy layer 13 having a high W concentration and the Ni-containing layer 12 having a low W concentration.

[0027] The Ni—W alloy layer 13 may be provided on only one surface or on both surfaces of the base steel plate 11. A surface treatment layer such as a coating film may be further provided on the surface of the Ni—W alloy layer 13.

[0028] (Fe diffusion alloy layer 14) At least a portion of the Ni-containing layer 12 is an Fe diffusion alloy layer 14. That is, the Ni-containing layer 12 has an Fe diffusion alloy layer 14. The Fe diffusion alloy layer 14 is an alloy layer formed by diffusing Fe from the base steel sheet 11 into the interior of the plating layer. The Fe diffusion alloy layer 14 can be obtained, for example, by plating the surface of the base steel sheet 11 and then performing an alloying treatment such as annealing.

[0029] In the cross-sectional schematic view illustrated in Fig. 1, only a portion of the Ni-containing layer 12 is the Fe diffusion alloy layer 14 in contact with the base steel plate 11. On the other hand, as illustrated in Fig. 2, the entire Ni-containing layer 12 may be the Fe diffusion alloy layer 14. Also, as illustrated in Fig. 2, the Fe diffusion alloy layer 14 may extend to the Ni—W alloy layer 13. That is, the Ni—W alloy layer 13 may have the Fe diffusion alloy layer 14. Only a portion of the Ni—W alloy layer 13 may be the Fe diffusion alloy layer 14, or the entire Ni—W alloy layer 13 may be the Fe diffusion alloy layer 14. The Fe diffusion alloy layer 14 formed in the Ni-containing layer 12 may be referred to as a Ni—Fe alloy layer, and the Fe diffusion alloy layer 14 formed in the Ni—W alloy layer 13 may be referred to as a Ni—W—Fe alloy layer. Generally, a surface-treated steel sheet in which only a portion of the Ni-containing layer 12 is the Fe diffusion alloy layer 14, and a surface-treated steel sheet in which the entire Ni-containing layer 12 is the Fe diffusion alloy layer 14 and only a portion of the Ni—W alloy layer 13 is the Fe diffusion alloy layer 14, are referred to as a partial diffusion-plated steel sheet. Furthermore, a surface-treated steel sheet in which the entire Ni-containing layer 12 and the entire Ni—W alloy layer 13 are the Fe diffusion alloy layer 14 are referred to as a fully diffusion-plated steel sheet.

[0030] (Porous Structure of Ni—W Alloy Layer 13) The Ni—W alloy layer 13 of the surface-treated steel sheet 1 according to this embodiment is porous. That is, as shown in the schematic diagram of FIG. 1 and the enlarged photographs of FIGS. 3A to 3C, the Ni—W alloy layer 13 has numerous voids B. The voids B are extremely small, with diameters of approximately 5 nm to 10 nm. Their presence can be identified by observing the cross section of the Ni—W alloy layer 13 with a high-resolution TEM. Note that the voids B contained in the Ni—W alloy layer 13 are conceptually different from pinholes. A pinhole is a fine, long hole that penetrates from the surface of the plating layer to the base steel sheet. On the other hand, the voids B present in the Ni—W alloy layer 13 of the surface-treated steel sheet 1 according to this embodiment are granular.

[0031] Examples of cross-sectional photographs of the Ni—W alloy layer 13 are shown in FIGS. 3A to 3C. The photographs in FIGS. 3A to 3C are a bright-field (BF) image, a high-angle annular dark field (HAADF) image, and elemental mapping images of Fe, Ni, O, and W of the same region. The white area present from the center to the top of the HAADF image is the Ni—W alloy layer 13. The gray area present at the bottom of the HAADF image is the Ni-containing layer 12. The HAADF image of the Ni—W alloy layer 13 contains many small dark dots. These dots are voids B. In the HAADF image, areas with low mass density in the direction perpendicular to the page are shown dark. The dark dots in the HAADF image in FIG. 3B have a lower mass density than their surroundings. Since no light elements are intentionally added to the Ni—W alloy layer 13, it is unlikely that light elements are segregated in the dark areas, and therefore the dark dots in the HAADF image of FIG.

[0032] In the HAADF image of Figure 3B, one of the many voids B is shown surrounded by a dashed line. As shown in the HAADF image of Figure 3B, in the surface-treated steel sheet 1 according to this embodiment, many voids B are formed throughout the entire cross section of the Ni-W alloy layer 13. On the other hand, if no voids B are present, the TEM photograph of the Ni-W alloy layer 13 will have a flat color tone. Therefore, by performing high-resolution TEM observation, it is possible to easily determine whether the Ni-W alloy layer 13 is porous.

[0033] (Effects) The surface-treated steel sheet 1 according to this embodiment has a Ni—W alloy layer 13. W has the function of increasing the electrical resistance of the plating layer. Therefore, the Ni—W alloy layer 13 increases the surface resistance of the surface-treated steel sheet 1 and improves weldability.

[0034] However, W hardens the Ni plating layer, impairing its workability. A plating layer with poor workability is prone to cracks during press forming and other processes. Cracks are breaks that extend from the surface of the plating layer to the base material. Cracks expose the base material to the outside of the plating, accelerating corrosion of the base material. Because Ni plating and Ni-W alloy plating do not have a sacrificial corrosion protection effect, Ni-plated steel sheets and Ni-W alloy-plated steel sheets are prone to corrosion, with cracks in the plating acting as the starting point.

[0035] In order to improve the workability of the plating layer, the inventors provided a Ni-containing layer 12 between the Ni—W alloy layer 13 and the base steel sheet 11. Furthermore, at least a portion of the Ni-containing layer 12 was alloyed. The Ni-containing layer 12 and the Fe-diffused alloy layer 14 prevent cracks from progressing to the base steel sheet 11, and thus prevent the base steel sheet 11 from being exposed to a corrosive environment.

[0036] However, the present inventors considered it more preferable to also improve the workability of the Ni—W alloy layer 13 itself. Therefore, they investigated a method for increasing the electrical resistance of the Ni—W alloy layer 13 while suppressing its W content. They then discovered that by making the Ni—W alloy layer 13 porous, it is possible to increase the electrical resistance of the Ni—W alloy layer 13 while suppressing its W content. The present inventors presume that the voids B have the effect of narrowing the cross-sectional area of ​​the current path and increasing the current density, thereby increasing the surface resistance of the surface-treated steel sheet 1. Therefore, when the electrical resistances of a porous Ni—W alloy layer 13 and a normal Ni—W alloy layer with the same W content are compared, the electrical resistance of the porous Ni—W alloy layer 13 is higher than that of the normal Ni—W alloy layer.

[0037] There are no particular limitations on the means for making the Ni—W alloy layer 13 porous. According to the findings of the present inventors, for example, the Ni-plated base layer can be subjected to an appropriate pickling treatment before the formation of the Ni—W alloy layer 13, and then the Ni—W alloy layer 13 can be subjected to an alloying treatment under specific conditions, thereby making the Ni—W alloy layer 13 porous.

[0038] As described above, the surface-treated steel sheet 1 according to this embodiment uses a porous Ni—W alloy layer 13 to improve surface resistance. While the W contained in the Ni—W alloy layer 13 reduces the workability of the surface-treated steel sheet, the Ni-containing layer 12 and the Fe-diffused alloy layer 14 compensate for this. Furthermore, since the Ni—W alloy layer 13 is porous in the surface-treated steel sheet 1 according to this embodiment, the W content of the Ni—W alloy layer 13 can be reduced to a low value while maintaining a high surface resistance. This allows the surface-treated steel sheet 1 according to this embodiment to reduce the appropriate current range when resistance-welding battery tabs without impairing workability.

[0039] The most basic aspect of the surface-treated steel sheet 1 according to this embodiment has been described above. Next, a more preferred aspect of the surface-treated steel sheet 1 according to this embodiment will be described.

[0040] (Average W Concentration in Ni—W Alloy Layer 13) The Ni—W alloy layer 13 contains Ni as a main component and further contains W. "The Ni—W alloy layer 13 contains Ni as a main component" means that Ni is the component with the highest mass concentration in the Ni—W alloy layer 13. The average W concentration in the Ni—W alloy layer 13 is not particularly limited, but may be, for example, within a range of 10 to 45 mass %.

[0041] W increases the electrical resistance of the Ni—W alloy layer 13. Furthermore, the inventors presume that W has the function of making the Ni—W alloy layer 13 porous under specific annealing conditions. By setting the average W concentration within the above-mentioned range, the electrical resistance of the Ni—W alloy layer 13 can be further increased. The average W concentration in the Ni—W alloy layer 13 may be 15 mass% or more, 20 mass% or more, 25 mass% or more, or 30 mass% or more. Furthermore, by reducing the W concentration in the Ni—W alloy layer 13, the workability of the Ni—W alloy layer 13 can be further improved. Therefore, the average W concentration in the Ni—W alloy layer 13 may be 45 mass% or less, 42 mass% or less, 40 mass% or less, or 38 mass% or less. For example, the Ni—W alloy layer 13 may contain Cr, Mo, or the like.

[0042] (Thickness of Ni—W Alloy Layer 13) The thickness of the Ni—W alloy layer 13 is not particularly limited. Even a small thickness of the Ni—W alloy layer 13 increases the surface resistance of the surface-treated steel sheet 1. Furthermore, from the viewpoint of further improving the workability of the Ni—W alloy layer 13, a smaller thickness of the Ni—W alloy layer 13 is advantageous. On the other hand, from the viewpoint of further increasing the surface resistance of the Ni—W alloy layer 13, a larger thickness of the Ni—W alloy layer 13 is advantageous. Therefore, the thickness of the Ni—W alloy layer 13 may be, for example, 0.01 μm or more. This can further increase the surface resistance of the surface-treated steel sheet 1. The thickness of the Ni—W alloy layer 13 may be 0.05 μm or more, 0.08 μm or more, or 0.10 μm or more. The upper limit of the thickness of the Ni—W alloy layer 13 is not particularly specified. For example, the Ni—W alloy layer 13 may be 2.0 μm or less, 1.5 μm or less, or 1.0 μm or less.

[0043] (Thickness of Ni-containing layer 12) The thickness of the Ni-containing layer 12 is not particularly limited. Even a small thickness of the Ni-containing layer 12 is effective in suppressing crack propagation. On the other hand, from the viewpoint of further improving the workability of the surface-treated steel sheet 1, a larger thickness of the Ni-containing layer 12 is advantageous. Therefore, the thickness of the Ni-containing layer 12 may be, for example, 0.2 μm or more. This further improves the workability of the surface-treated steel sheet 1. The thickness of the Ni-containing layer 12 may be 0.7 μm or more, 1.0 μm or more, or 1.5 μm or more. The upper limit of the thickness of the Ni-containing layer 12 is not particularly specified. For example, the Ni-containing layer 12 may be 4.0 μm or less, 3.0 μm or less, or 2.0 μm or less.

[0044] (Ni deposition weight) The deposition weight of Ni contained in the plating layer (i.e., the Ni-containing layer 12 and the Ni—W alloy layer 13) is not particularly limited, but is, for example, 1.8 to 35.6 g / m ２ The Ni deposition amount may be in the range of 1.8 g / m ２ Setting the Ni deposition amount to 35.6 g / m or more further improves the corrosion resistance of the surface-treated steel sheet 1. ２ By setting the Ni deposition amount to 4.5 g / m or less, it is possible to reduce the manufacturing cost of the surface-treated steel sheet 1. ２ Above, 6.2g / m ２ or more, or 8.9 g / m ２ The Ni deposition amount may be 26.7 g / m or more. ２ Below, 17.8g / m ２ or less, or 13.4 g / m ２ It may be the following:

[0045] The thickness of the plating layer (i.e., the total thickness of the Ni-containing layer 12 and the Ni—W alloy layer 13) is not particularly limited. For example, the thickness of the plating layer may be in the range of 0.2 μm to 4.0 μm.

[0046] (Thickness of Fe Diffusion Alloy Layer 14) The thickness of the Fe diffusion alloy layer 14 is not particularly limited. Even if the thickness is small, the Fe diffusion alloy layer 14 can suppress crack propagation, improve the workability of the surface-treated steel sheet 1, and improve the corrosion resistance of the processed portion. On the other hand, the thickness of the Fe diffusion alloy layer 14 may be, for example, 0.1 μm or more. This can further improve the workability of the surface-treated steel sheet 1. The thickness of the Fe diffusion alloy layer 14 may be 0.2 μm or more, 0.5 μm or more, or 1.0 μm or more. There is no particular upper limit for the thickness of the Fe diffusion alloy layer 14. For example, the entire plating layer may be the Fe diffusion alloy layer 14. On the other hand, the Fe diffusion alloy layer 14 may be 3.0 μm or less, 2.5 μm or less, or 2.0 μm or less.

[0047] (Components of Ni-Containing Layer 12) The Ni-containing layer 12 is a layer containing Ni and Fe diffused from the base steel sheet 11 as its main components. For example, the total content of Ni and Fe in the Ni-containing layer 12 may be 98.0 mass% or more, 98.5 mass% or more, or 99.0 mass% or more. The total content of Ni and Fe in the Ni-containing layer 12 may be 100 mass% or less, 99.5 mass% or less, or 99.0 mass% or less. Note that the ratio of Ni to Fe in the Ni-containing layer 12 is not uniform in the thickness direction of the Ni-containing layer 12 (thickness direction of the surface-treated steel sheet). This is because, as described above, part or all of the Ni-containing layer 12 is the Fe-diffusion alloy layer 14, and the amount of Fe diffused from the base steel sheet 11 in the Fe-diffusion alloy layer 14 varies in the thickness direction of the Fe-diffusion alloy layer 14. In the Fe diffusion alloy layer 14, the Fe content increases toward the base steel plate 11. The thickness of the Fe diffusion alloy layer 14 can be selected appropriately.

[0048] The Ni-containing layer 12 may contain elements other than Ni and Fe. For example, the Ni-containing layer 12 may contain Cr and Mo. For example, the Ni-containing layer 12 may contain one or more of Cr and Mo, with the total content being more than 0 mass% and not more than 0.1 mass%. Furthermore, various alloy elements contained in the base steel plate 11 may diffuse into the Ni-containing layer 12 during the alloying treatment. Therefore, the Ni-containing layer 12 may contain various impurity elements. In addition, W may diffuse into the Ni-containing layer 12 from the Ni-W alloy layer 13. However, the W content of the Ni-containing layer 12 is usually less than 1.0%.

[0049] (Components of Ni—W Alloy Layer 13) As described above, the Ni—W alloy layer 13 contains Ni as a main component and further contains W. As illustrated in FIG. 2 , when a part or all of the Ni—W alloy layer 13 is an Fe-diffusion alloy layer 14, the Ni—W alloy layer 13 may further contain Fe. When the Ni—W alloy layer 13 does not have the Fe-diffusion alloy layer 14, the total content of Ni and W in the Ni—W alloy layer 13 may be 95.0 mass% or more, 96.0 mass% or more, or 97.0 mass% or more. When the Ni—W alloy layer 13 does not have the Fe-diffusion alloy layer 14, the total content of Ni and W in the Ni—W alloy layer 13 may be 100 mass% or less, 99.0 mass% or less, or 98.0 mass% or less. When the Ni—W alloy layer 13 has the Fe-diffusion alloy layer 14, the total content of Ni, W, and Fe in the Ni—W alloy layer 13 may be 95.0 mass% or more, 96.0 mass% or more, or 97.0 mass% or more. When the Ni—W alloy layer 13 has the Fe-diffusion alloy layer 14, the total content of Ni, W, and Fe in the Ni—W alloy layer 13 may be 100 mass% or less, 99.0 mass% or less, or 98.0 mass% or less.

[0050] Like the Ni-containing layer 12, the Ni—W alloy layer 13 may contain elements other than Ni, W, and Fe. For example, the Ni—W alloy layer 13 may contain Cr, Mo, etc. For example, the Ni—W alloy layer 13 may contain one or more of Cr, Co, and Mo, with the total content being more than 0 mass % and not more than 5 mass %. The Ni—W alloy layer 13 may also contain various impurity elements.

[0051] (Types of base steel plate 11, etc.) The components and metal structure of the base steel plate 11 are not particularly limited. The components and metal structure of the base steel plate 11 can be selected appropriately depending on the application of the surface-treated steel plate 1. For example, the chemical components of the base steel plate 11 may contain, in mass%, C: 0.0001 to 0.08, Si: 0.001 to 0.03, Mn: 0.01 to 0.4, P: 0.001 to 0.03, and S: 0.000 to 0.03, with the balance containing iron and impurities. The base steel plate 11 may contain elements other than C, Si, Mn, P, and S.

[0052] When the surface-treated steel sheet 1 is used as a material for a battery container, for example, the base steel sheet 11 is preferably low-carbon aluminum-killed steel, IF steel (Interstitial Free Steel / ultra-low carbon steel), etc. Specific examples of the chemical composition (unit: mass %) of the base steel sheet 11 are as follows: (Example 1) Low carbon aluminum killed steel C: 0.057, Si: 0.004, Mn: 0.29, P: 0.014, S: 0.007, Al: 0.050, Cu: 0.034, Ni: 0.021, balance: iron and impurities included (Example 2) IF steel C: 0.004, Si: 0.01, Mn: 0.16, P: 0.013, S: 0.006, Al: 0.029, Cu: 0.027, Ni: 0.022, Ti: 0.013, balance: iron and impurities included (Example 3) IF steel C: 0.0012, Si: less than 0.01, Mn: 0.16, P: 0.013, S: 0.006, Al: 0.029, Cu: 0.027, Ni: 0.022, Ti: 0.020, balance: iron and impurities

[0053] There is also no particular limitation on the thickness of the base steel sheet 11. When the surface-treated steel sheet 1 is used as a material for a battery container, for example, the thickness of the base steel sheet 11 is preferably, for example, 0.15 to 2.00 mm.

[0054] (Measurement Method) Whether or not the Ni—W alloy layer 13 is porous is determined by the following procedure. First, the surface-treated steel sheet 1 is processed into a foil piece using a focused ion beam (FIB) so that a cross section can be observed along the sheet thickness direction. The sample obtained in this manner is analyzed using a field-emission scanning electron microscope (FE-SEM) with a scanning transmission electron microscope (STEM) mode capable of elemental analysis by EDS. The instrument model is Titan (Thermo Fischer Scientific). The acceleration voltage was 300 kV. The measurement magnification was 140,000 times. When observing an HAADF image, the smaller the mass in the transmission direction, the darker the image; therefore, the black areas are considered to be elements lighter than Ni and W, or voids. However, the presence of elements lighter than Ni is unlikely, and they can be determined to be voids. If a large number of voids are formed throughout the entire cross section of the Ni—W alloy layer 13, the Ni—W alloy layer 13 is determined to be porous. Specifically, five random 100 nm × 100 nm regions are observed from the Ni—W alloy layer 13 region in the obtained HAADF image, and the number of voids with a diameter of 5 nm or more is counted. The number of voids with a diameter of 5 nm or more identified in the five 100 nm × 100 nm regions is added up and divided by 5 to determine the average number of voids with a diameter of 5 nm or more per region. If the average number of voids with a diameter of 5 nm or more per region in the five regions is 5 or more, the Ni—W alloy layer 13 is determined to be porous.

[0055] The average W concentration in the Ni—W alloy layer 13 is measured as follows. Measurement is performed using XPS (X-ray photoelectron spectroscopy). First, the surface of the surface-treated steel sheet 1 is sputtered using argon and / or xenon. Next, the components of the Ni—W alloy layer 13 of the surface-treated steel sheet 1 are measured from the surface toward the inside. After the measurement is completed, sputtering is performed again, followed by measurement, and this cycle is repeated. The analysis results of the W concentration along the depth direction are plotted on a graph in which the horizontal axis represents the depth from the surface of the Ni—W alloy layer 13 and the vertical axis represents the W concentration. The value obtained by integrating the W concentration graph is then divided by the width of the interval (i.e., the thickness of the Ni—W alloy layer 13), and this value is considered to be the average W concentration. By applying the above calculation performed on the W concentration to the Ni and Fe analysis results, the average Ni concentration and average Fe concentration in the Ni—W alloy layer 13 can be determined. Note that the component measurement of the plating layer using XPS is performed using a Mg radiation source. In the analysis using the Mg radiation source, there are no Auger peaks that overlap with the photoelectron peaks of Ni, W, and Fe. Peaks observed were those of the 2p orbital for Fe, the 2p orbital for Ni, and the 4f orbital for W.

[0056] The Ni deposition mass is measured by inductively coupled plasma (ICP) optical emission spectroscopy (ICP-OES). First, a predetermined area of ​​the plating layer is dissolved in acid. Next, the total Ni amount contained in the solution is quantitatively analyzed by ICP-OES. The total Ni amount determined by ICP-OES is divided by the predetermined area to determine the Ni deposition mass per unit area.

[0057] The thickness of the Ni-containing layer 12, the Ni—W alloy layer 13, and the Fe-diffused alloy layer 14 are measured by Glow Discharge Optical Emission Spectrometry (GDS). By using GDS, the distribution of element concentrations in the Ni-containing layer 12 and the Ni—W alloy layer 13 in the depth direction from the plating layer surface can be measured, thereby obtaining element concentration curves.

[0058] A high-frequency glow discharge optical emission surface analyzer (manufactured by Horiba, Ltd., model number: GD-Profiler2) was used for the measurement. The GDS measurement conditions were as follows: anode diameter: φ4 mm, gas: Ar, gas pressure: 600 Pa, output: 35 W.

[0059] In the surface-treated steel sheet 1 according to this embodiment, a region in the coating layer containing an Fe concentration of 5.0 mass % or more is considered to be the Fe-diffused alloy layer 14. When component analysis is performed continuously from the surface of the coating layer in the depth direction, the Fe concentration increases toward the base steel sheet 11. A location with an Fe concentration of 5.0 mass %, identified by continuous component analysis from the surface of the coating layer in the depth direction, is considered to be the interface between the Fe-diffused alloy layer 14 and a coating layer that is not the Fe-diffused alloy layer 14.

[0060] Furthermore, in the surface-treated steel sheet 1 according to this embodiment, the region where the Ni concentration is 1.0 mass % or more is regarded as the plating layer, and the other region is regarded as the base steel sheet 11. In the plating layer of the surface-treated steel sheet 1 manufactured by alloying treatment, the Ni concentration decreases toward the base steel sheet 11. A location where the Ni concentration is 1.0 mass %, which is identified by continuously analyzing the components along the depth direction from the surface of the plating layer, is regarded as the interface between the plating layer and the base steel sheet 11 (i.e., the interface between the Fe-diffused alloy layer 14 and the base steel sheet 11).

[0061] The distance between these interfaces is regarded as the thickness of the Fe-diffused alloy layer 14 in the sample obtained by the above-described procedure. This measurement is performed on five samples, and the average value is calculated. This average value is regarded as the thickness of the Fe-diffused alloy layer 14 of the surface-treated steel sheet 1.

[0062] Furthermore, in the surface-treated steel sheet 1 according to this embodiment, a region in the plating layer where the W concentration is 1.0 mass % or more is regarded as the Ni—W alloy layer 13, and a region where the W concentration is less than 1.0 mass % is regarded as the Ni-containing layer 12. A location where the W concentration is 1.0 mass %, which is identified by continuously performing component analysis from the surface of the plating layer in the depth direction, is regarded as the interface between the Ni—W alloy layer 13 and the Ni-containing layer 12.

[0063] The distance from the interface between the Ni—W alloy layer 13 and the Ni-containing layer 12 to the interface between the plating layer and the base steel sheet 11 is regarded as the thickness of the Ni-containing layer 12 in the sample obtained by the above-mentioned procedure. This measurement is performed on five samples, and the average value is calculated. This average value is regarded as the thickness of the Ni-containing layer 12 in the surface-treated steel sheet 1. In addition, the distance from the surface of the plating layer to the interface between the Ni—W alloy layer 13 and the Ni-containing layer 12 is regarded as the thickness of the Ni—W alloy layer 13 in the sample obtained by the above-mentioned procedure. This measurement is performed on five samples, and the average value is calculated. This average value is regarded as the thickness of the Ni—W alloy layer 13 in the surface-treated steel sheet 1.

[0064] (2. Manufacturing Method of Surface-Treated Steel Sheet 1) Next, a manufacturing method of the surface-treated steel sheet according to the present embodiment will be described. For example, the manufacturing method according to the present embodiment can suitably obtain the surface-treated steel sheet 1 having the above-described components.

[0065] As illustrated in FIG. 4 , a method for producing a surface-treated steel sheet according to another embodiment of the present invention includes: (S1) a step of electrolytically Ni-plating a base steel sheet 11; (S2) a step of pickling the base steel sheet 11 having the Ni-plated layer; (S3) a step of electrolytically Ni—W alloy-plating the base steel sheet 11 having the Ni-plated layer; and (S4) a step of annealing the base steel sheet 11 having the Ni-plated layer and the Ni—W alloy layer 13 disposed thereon, wherein the pickling bath is a 70 to 100 g / L sulfuric acid bath, the time for which the base steel sheet having the Ni-plated layer is immersed in the bath (immersion time) is 25 to 35 seconds, the annealing temperature is 630 to 860° C., and the annealing time is 10 to 180 seconds.

[0066] (S1: Ni electroplating) First, the base steel sheet 11 is Ni electroplated. The base material for plating is the same as the base steel sheet 11 of the surface-treated steel sheet 1 according to this embodiment described above. As a result, a Ni-containing layer 12 is provided on the surface of the base steel sheet 11, as shown in Fig. 4 . The plated steel sheet obtained by Ni electroplating will hereinafter be referred to as a Ni-plated steel sheet.

[0067] (S2 Pickling) Next, the Ni-plated steel sheet is pickled. The pickling conditions are as follows: Pickling bath: 70 to 100 g / L sulfuric acid bath Immersion time: 25 to 35 seconds Furthermore, following the pickling, it is desirable to rinse the Ni-plated steel sheet with water in the rinse section and then drain the water. This prevents the pickling bath from mixing with the electric Ni—W alloy plating bath described below. Note that the pickling must be carried out before the electric Ni—W alloy plating.

[0068] (S3 Electrical Ni—W alloy plating) Next, the Ni-plated steel sheet that has been pickled under the above-mentioned conditions is subjected to electrical Ni—W alloy plating. As a result, a Ni—W alloy layer 13 is provided on the surface of the Ni-plated steel sheet, as shown in Fig. 4. The plated steel sheet obtained by electrical Ni—W alloy plating is hereinafter referred to as a multi-layer plated steel sheet.

[0069] (S4 Annealing) Next, the multi-layer plated steel sheet (i.e., the base steel sheet 11 having the Ni plating layer and the Ni—W alloy layer 13 disposed thereon) is annealed. As a result, as shown in Fig. 4 , Fe in the base steel sheet 11 is diffused into a part of the plating layer to form an Fe diffusion alloy layer 14. In this way, a surface-treated steel sheet 1 can be obtained that includes the base steel sheet 11, the Ni-containing layer 12 disposed on the surface of the base steel sheet 11, and the Ni—W alloy layer 13 disposed on the surface of the Ni-containing layer 12, wherein the Ni-containing layer 12 has the Fe diffusion alloy layer 14.

[0070] The annealing temperature is set to 630 to 860° C., and the annealing time is set to 10 to 180 seconds, thereby making the Ni—W alloy layer 13 porous.

[0071] The present inventors believe that the reason why the Ni—W alloy layer 13 can be made porous by setting the pickling conditions and annealing conditions within the above-mentioned ranges is as follows: During electroplating, metal ions contained in the plating bath are electrodeposited on the substrate surface, and at the same time, hydrogen ions contained in the plating bath are incorporated into the plating layer. The present inventors believe that this hydrogen forms voids B during annealing.

[0072] However, the present inventors have found that the Ni-containing layer 12 must be pickled under the above-mentioned conditions before electric Ni—W alloy plating. The present inventors presume that pickling under appropriate conditions removes the oxide film on the surface of the Ni-containing layer 12, facilitating the diffusion of hydrogen contained in the Ni-containing layer 12 into the Ni—W alloy layer 13. On the other hand, if the sulfuric acid concentration in the pickling is insufficient or the immersion time is short, the oxide film on the surface of the Ni-containing layer 12 is not sufficiently removed, and the present inventors presume that this inhibits the diffusion of hydrogen contained in the Ni-containing layer 12 into the Ni—W alloy layer 13.

[0073] The present inventors also presume that when the Ni plating contains W, the W affects the behavior of hydrogen. Furthermore, the present inventors presume that by making the Ni plating contain W and setting the annealing conditions within the above-mentioned ranges, hydrogen supplied from the Ni-containing layer 12 to the Ni—W alloy layer 13 forms a large number of voids B in the Ni—W alloy layer 13, thereby making the Ni—W alloy layer 13 porous.

[0074] The above has described the most basic aspect of the method for manufacturing the surface-treated steel sheet 1 according to this embodiment. Next, a more preferred aspect of the method for manufacturing the surface-treated steel sheet 1 according to this embodiment will be described.

[0075] (Bath Components) The Ni plating bath used in electrolytic Ni plating contains Ni as a main component. For example, the proportion of Ni element contained in the plating bath to all metal elements contained in the plating bath may be 95 mass % or more, 96 mass % or more, or 97 mass % or more. In addition to Ni, the Ni plating bath may contain Cr, Mo, etc.

[0076] The Ni—W plating bath used in electric Ni—W alloy plating contains Ni and W as its main components. For example, the proportion of W element contained in the plating bath relative to all metal elements contained in the plating bath may be within a range of 10 to 60 mass %. Furthermore, for example, the proportion of the total of Ni element and W element contained in the plating bath relative to all metal elements contained in the plating bath may be 95 mass % or more, 96 mass % or more, or 97 mass % or more. In addition to Ni and W, the Ni—W plating bath may also contain Cr, Mo, etc.

[0077] (Ni deposition weight) In the electrolytic Ni plating and electrolytic Ni-W alloy plating, the Ni deposition weight is not particularly limited, but is, for example, 1.8 to 35.6 g / m ２ As a result, the Ni deposition amount contained in the Ni-containing layer 12 and the Ni—W alloy layer 13 is set to 1.8 to 35.6 g / m ２ The more preferable Ni coating weight may be the same as the more preferable Ni coating weight in the surface-treated steel sheet 1 according to this embodiment described above. The Ni coating weight can be controlled via the components of the coating bath and the amount of current.

[0078] In addition, the various aspects described with respect to the surface-treated steel sheet 1 according to this embodiment can be applied to the method for manufacturing the surface-treated steel sheet according to this embodiment. For example, it goes without saying that the preferred aspects of the base steel sheet 11 in the surface-treated steel sheet 1 according to this embodiment can be applied to the method for manufacturing the surface-treated steel sheet according to this embodiment.

[0079] (3. Manufacturing Method of Battery Component) Next, a manufacturing method of a battery component according to another aspect of the present invention will be described. The manufacturing method of a battery component according to this embodiment includes a step of resistance welding a tab and a surface-treated steel sheet 1, and this surface-treated steel sheet 1 is the surface-treated steel sheet 1 according to this embodiment. The resistance welding is, for example, spot welding.

[0080] The surface-treated steel sheet 1 according to this embodiment has a high surface resistance and a low appropriate current value for resistance welding to the tab. Therefore, there is little risk of damage to the tab due to an overcurrent when resistance welding the surface-treated steel sheet 1 according to this embodiment. Therefore, the battery component manufacturing method according to this embodiment can suitably manufacture the battery component.

[0081] Although the resistance welding conditions are not particularly limited, it is preferable that the welding voltage in the resistance welding be 2.0 V to 3.5 V and the current application time be 1.0 ms to 10.0 ms, for example. This can further suppress poor bonding between the tab and the surface-treated steel sheet 1 and breakage of the tab.

[0082] The effects of one embodiment of the present invention will be explained in more detail using examples. However, the conditions in the examples are merely examples adopted to confirm the feasibility and effects of the present invention. The present invention is not limited to these examples. Various conditions may be adopted in the present invention as long as they do not deviate from the gist of the present invention and achieve the object of the present invention.

[0083] (Experiment 1) Various surface-treated steel sheets were produced by subjecting a base steel sheet to Ni electroplating, pickling, Ni—W alloy electroplating, and annealing. The components of the base steel sheet are shown in Table 1. The components of the plating bath used in the Ni—W alloy electroplating are shown in Table 2. The manufacturing conditions of the surface-treated steel sheets are shown in Table 3. The evaluation results of the surface-treated steel sheets are shown in Table 4. In Tables 3 and 4, values ​​outside the range of this embodiment are underlined. Note that conditions not listed in the tables were the same in all examples, and their details are as follows:

[0084] The components of the plating bath for electroplating Ni are NiSO ４ ・6H ２ O: 230 g / L, and H ３ BO ３ The pH of the plating bath for electroplating was 4, and the temperature was 50°C. The current density in electroplating was 30 A / dm ２ The plating weight in the Ni electroplating was controlled by controlling the current application time.

[0085] In the pickling after the Ni electroplating, the Ni-plated steel sheet was immersed in a 85 g / L sulfuric acid bath for 30 seconds, then rinsed with water, and then drained.

[0086] The Ni ion source in electric Ni-W alloy plating is NiSO ４ ・6H ２ O, and the W ion source is Na ２ WO ４ ・2H ２The composition (W content) of the Ni-W alloy plating was adjusted by changing the ratio of Ni ion concentration and W ion concentration. In addition, 0.5 mol / L of citric acid was added to the plating bath for electric Ni-W alloy plating to stabilize the W ions in the bath. The pH of the plating bath for electric Ni-W alloy plating was set to 6, and the temperature was set to 50°C. The current density in electric Ni-W alloy plating was 20 A / dm ２ The plating weight in the electric Ni—W alloy plating was controlled by controlling the current application time.

[0087] The presence or absence of porosity in the Ni—W alloy layer was determined by the above-mentioned method using an FE-SEM equipped with an STEM mode capable of elemental analysis by EDS. The determination results are shown in Table 4.

[0088] The average W concentration in the Ni—W alloy layer was measured by the above-mentioned method using XPS. The measurement results are shown in Table 4.

[0089] The thickness of the Ni—W alloy layer and the thickness of the Fe-diffused alloy layer were measured by the method using GDS described above. The measurement results are shown in Table 4.

[0090] Weldability was evaluated using the following procedure. Each sample was welded to a tab (material and size: nickel thin film 10 x 100 x 0.01 mm). The welding voltage was 2.5 V and the current time was 5.0 ms. After welding, the degree of bonding between the tab and the steel sheet was evaluated visually. The evaluation criteria were as follows: 1: No poor bonding or tab damage 2: No poor bonding or tab damage, but discoloration of the sample or tab was observed 3: Poor bonding or tab damage was observed

[0091]

[0092]

[0093]

[0094]

[0095] In the test specimens of Examples 4, 5, and 8, the Ni—W alloy layer was not porous. The weldability of these test specimens was poor. In the production of Example 4, the annealing time was insufficient. In the production of Example 5, the annealing temperature was excessive and the annealing time was insufficient. In the production of Example 8, pickling was not performed. The inventors presume that in Examples 4, 5, and 8, a porous Ni—W alloy layer was not obtained due to inappropriate production conditions.

[0096] On the other hand, the Ni-W alloy layer of the test pieces obtained by the proper manufacturing method was porous.The weldability of these test pieces was good.

[0097] (Experiment 2) Various surface-treated steel sheets were prepared by subjecting a base steel sheet to Ni electroplating, pickling, Ni-W alloy electroplating, and annealing. The pickling conditions were as shown in Table 5. The manufacturing conditions other than the pickling conditions were the same as those in Example 1 disclosed in Tables 3 and 4.

[0098]

[0099] The surface-treated steel sheets manufactured by the above-described procedure were evaluated in the same manner as in Experiment 1. The evaluation results are shown in Table 6.

[0100]

[0101] The manufacturing conditions of Examples 101 to 105 were the same as those of Example 1, except for the pickling conditions. However, unlike Example 1, the Ni—W alloy layers of the test specimens of Examples 101 to 105 were not porous. Unlike Example 1, the weldability of the test specimens of Examples 101 to 105 was inferior.

[0102] In Examples 101 and 103, the sulfuric acid concentration in the pickling bath was insufficient. It is presumed that this resulted in insufficient removal of the oxide film on the surface of the Ni-containing layer in Examples 101 and 103, and the Ni—W alloy layer was not made porous. In Example 103, instead of lowering the sulfuric acid concentration in the pickling bath, hydrochloric acid was added to the bath. However, even when a bath containing hydrochloric acid was used, it was not possible to obtain a surface-treated steel sheet with good weldability like that of Example 1. It is presumed that this is because hydrochloric acid has a less effective pickling effect than sulfuric acid.

[0103] In Example 102, the sulfuric acid concentration in the pickling bath was excessive, and the Ni—W alloy layer in Example 102 was not made porous.

[0104] The effect of excessive sulfuric acid concentration on the Ni—W alloy layer is unclear, but the inventors speculate as follows: When the sulfuric acid concentration is excessive, the surface of the Ni-containing layer becomes minutely uneven. When a Ni—W alloy layer is provided on top of this, the area of ​​the interface between the Ni-containing layer and the Ni—W alloy layer increases. It is generally believed that diffusible hydrogen is easily trapped at the interface of a plating layer. The inventors speculate that the increase in the area of ​​the interface reduces the amount of diffusible hydrogen in the Ni—W alloy layer, preventing the Ni—W alloy layer from becoming porous due to diffusible hydrogen.

[0105] In Example 104, the base steel sheet having the Ni-plated layer was immersed in the pickling bath for an insufficient time, which is presumably why the oxide film on the surface of the Ni-containing layer was not sufficiently removed in Example 104, and the Ni—W alloy layer was not made porous.

[0106] In Example 105, the base steel sheet having a Ni-plated layer was immersed in the pickling bath for an excessively long time. Consequently, the Ni—W alloy layer was not rendered porous in Example 105. The effect of excessive pickling time on the Ni—W alloy layer is unclear, but the inventors presume that a phenomenon similar to that observed in the example in which the sulfuric acid concentration was excessive occurred. In other words, it is presumed that excessive pickling expanded the area of ​​the interface between the Ni-containing layer and the Ni—W alloy layer, preventing the Ni—W alloy layer from becoming porous due to diffusible hydrogen.

[0107] REFERENCE SIGNS LIST 1 surface-treated steel sheet 11 base steel sheet 12 Ni-containing layer 13 Ni-W alloy layer 14 Fe-diffused alloy layer B void

Claims

1. A surface-treated steel sheet comprising: a base steel sheet; a Ni-containing layer disposed on the surface of the base steel sheet; and a Ni-W alloy layer disposed on the surface of the Ni-containing layer, wherein the Ni-containing layer has an Fe-diffused alloy layer, and the Ni-W alloy layer is porous.

2. The surface-treated steel sheet according to claim 1, wherein the average W concentration in the Ni-W alloy layer is 10 to 45 mass %.

3. The surface-treated steel sheet according to claim 1 or 2, wherein the thickness of the Ni-W alloy layer is 0.01 to 2.0 μm.

4. The Ni deposition amount contained in the Ni-containing layer and the Ni-W alloy layer is 1.8 to 35.6 g / m ２ The surface-treated steel sheet according to claim 1 or 2, characterized in that 5. The surface-treated steel sheet according to claim 1 or 2, characterized in that the thickness of the Fe diffusion alloy layer is 0.1 to 3.0 μm.

6. The surface-treated steel sheet according to claim 1 or 2, characterized in that only a part of the Ni-containing layer is the Fe-diffused alloy layer.

7. The surface-treated steel sheet according to claim 1 or 2, wherein the entire Ni-containing layer is the Fe-diffused alloy layer, and a portion of the Ni-W alloy layer is the Fe-diffused alloy layer.

8. A method for producing a surface-treated steel sheet, comprising: a step of electrolytically Ni-plating a base steel sheet; a step of pickling the base steel sheet having the Ni-plated layer; a step of electrolytically Ni-W alloy-plating the base steel sheet having the Ni-plated layer; and a step of annealing the base steel sheet having the Ni-plated layer and a Ni-W alloy layer disposed thereon; wherein in the pickling, a pickling bath is a 70 to 100 g / L sulfuric acid bath; in the pickling, the base steel sheet having the Ni-plated layer is immersed in the bath for 25 to 35 seconds; in the annealing, an annealing temperature is 630 to 860°C; and in the annealing, an annealing time is 10 to 180 seconds.

9. A method for manufacturing battery components, comprising a step of resistance welding a tab and the surface-treated steel sheet according to claim 1 or 2.

10. The method for manufacturing a battery component according to claim 9, wherein the welding voltage in the resistance welding is set to 2.0 V to 3.5 V, and the current application time in the resistance welding is set to 1.0 ms to 10.0 ms.

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