Ferritic stainless steel foil, electrode, and battery

Abstract

Provided is a ferritic stainless steel foil exhibiting excellent corrosion resistance. A ferritic stainless steel foil according to the present disclosure is provided with a foil main body made of ferritic stainless steel, wherein the diffraction intensity I110 of the {110} plane, the diffraction intensity I200 of the {200} plane, and the diffraction intensity I211 of the {211} plane, which are obtained by concentration X-ray diffraction measurement in the foil main body, satisfy formula (1).　I110 / (I110 + I200 + I211) ≤ 0.16 (1)

Description

Ferritic stainless steel foil, electrode, and battery

[0001] The present disclosure relates to a ferritic stainless steel foil, an electrode using the ferritic stainless steel foil as a current collector, and a battery using the electrode, and more specifically to a ferritic stainless steel foil used as a current collector for a secondary battery.

[0002] Batteries such as primary batteries and secondary batteries have been used as power sources for various electronic devices. In recent years, secondary batteries, typified by lithium-ion batteries, have become increasingly popular due to the widespread use of small electronic devices such as home video cameras, laptops, and smartphones.

[0003] A secondary battery includes electrodes having a positive electrode and a negative electrode, and an electrolyte. Both the positive electrode and the negative electrode have an electrode mixture layer formed on a current collector. The electrode mixture layer is a layer containing an active material. The current collector has the function of supplying current to the active material and the function of serving as a substrate for supporting the electrode mixture layer.

[0004] Conventionally, electrolyte solutions have been used as electrolytes in secondary batteries. However, because electrolyte solutions contain flammable organic solvents, their usable temperature range is narrow. For this reason, in recent years, development of all-solid-state batteries using solid electrolytes instead of electrolyte solutions has been progressing. Because all-solid-state batteries do not contain organic solvents, stable battery performance can be obtained over a wide temperature range. Among the solid electrolytes used in all-solid-state batteries, sulfide-based solid electrolytes, including LPS (lithium phosphorus sulfide), have particularly high ionic conductivity. Therefore, the use of sulfide-based solid electrolytes can achieve high output in all-solid-state batteries.

[0005] On the other hand, when a sulfide-based solid electrolyte is used, the current collector may be corroded by sulfides. Corrosion of the current collector results in a decrease in battery performance. In other words, the current collector must have high corrosion resistance. For this reason, the use of highly corrosion-resistant stainless steel as the current collector material is being considered. Among stainless steels, ferritic stainless steel in particular has lower electrical resistance and higher conductivity than austenitic stainless steel. For this reason, ferritic stainless steel is suitable as a current collector material.

[0006] However, even when ferritic stainless steel is used as a current collector, corrosion reactions due to sulfide-based solid electrolytes still occur in all-solid-state batteries, so there is a need for technology to further improve the corrosion resistance of ferritic stainless steel.

[0007] A technology for improving the corrosion resistance of ferritic stainless steel for current collector applications is proposed in International Publication No. 2021 / 006089 (Patent Document 1).

[0008] The ferritic stainless steel sheet for use as a current collector in a sulfide-based solid battery disclosed in Patent Document 1 contains 0.001 to 0.050% C, 0.01 to 2.00% Si, 0.01 to 1.00% Mn, 0.050% or less P, 0.010% or less S, 18.00 to 32.00% Cr, 0.01 to 4.00% Ni, 0.001 to 0.150% Al, and 0.050% or less N, with the balance consisting of Fe and unavoidable impurities. Patent Document 1 states that this ferritic stainless steel sheet exhibits excellent sulfidation resistance by increasing the Cr content to 18.00% or more.

[0009] International Publication No. 2021 / 006089

[0010] However, the corrosion resistance of ferritic stainless steel may be improved by a means different from that of the ferritic stainless steel sheet disclosed in Patent Document 1.

[0011] An object of the present disclosure is to provide a ferritic stainless steel foil that can provide excellent corrosion resistance, an electrode that uses the ferritic stainless steel foil as a current collector, and a battery that uses the electrode.

[0012] The ferritic stainless steel foil of the present disclosure includes a foil body made of ferritic stainless steel, and a diffraction intensity I of the {110} plane obtained by focusing X-ray diffraction measurement of the foil body. １１０ and the diffraction intensity I of the {200} plane ２００ and the diffraction intensity I of the {211} plane ２１１ and satisfy the formula (1). １１０ / (I １１０ +I ２００ +I ２１１ ) ≦0.16 (1)

[0013] The electrode of the present disclosure comprises the ferritic stainless steel foil of the present disclosure and an electrode mixture layer formed on the surface of the ferritic stainless steel foil.

[0014] The battery of the present disclosure comprises: an electrode of the present disclosure; and an electrolyte.

[0015] The ferritic stainless steel foil of the present disclosure provides excellent corrosion resistance. The electrode of the present disclosure comprises the ferritic stainless steel foil of the present disclosure. The battery of the present disclosure comprises the electrode of the present disclosure.

[0016] The present inventors have investigated means for improving the corrosion resistance of ferritic stainless steel foil, and as a result, have made the following findings.

[0017] In Patent Document 1, the Cr content of ferritic stainless steel is increased to improve its corrosion resistance. Thus, the inclusion of alloying elements that improve corrosion resistance is effective for improving the corrosion resistance of ferritic stainless steel foil. However, increasing the content of alloying elements reduces the workability of the ferritic stainless steel foil and increases the manufacturing cost. Therefore, the inventors focused on the crystal orientation of the foil body rather than the chemical composition of the foil body in a ferritic stainless steel foil having a foil body made of ferritic stainless steel.

[0018] In the body-centered cubic lattice of the foil body made of ferritic stainless steel, the {110} plane is the lattice plane in which atoms are most densely arranged (close-packed atomic plane). Close-packed atomic planes such as the {110} plane serve as slip planes for dislocations.

[0019] In the manufacturing process of ferritic stainless steel foil and the manufacturing process of batteries using ferritic stainless steel foil as a current collector, processing involving deformation of the foil body is carried out. During such processing, microcracks may occur in the foil body due to cleavage fracture. The occurrence of cracks during processing is more likely when the {110} plane, which is both the close-packed atomic plane and the slip plane, is oriented parallel or perpendicular to the depth direction of the foil body (the normal direction to the surface of the foil body). Furthermore, corrosion of ferritic stainless steel foil preferentially progresses along these microcracks. In other words, the more the {110} plane is oriented parallel or perpendicular to the depth direction, the more likely microcracks are to occur during processing, which accelerates the progression of corrosion of the ferritic stainless steel foil.

[0020] The crystal orientation of the foil body can be evaluated by focusing X-ray diffraction measurement. The three major lattice planes detected by focusing X-ray diffraction measurement of the foil body are the {110}, {200}, and {211} planes. The lower the ratio of the diffraction intensity of the {110} plane to the sum of the diffraction intensities of the three lattice planes, the lower the orientation of the {110} plane in the depth direction. In this case, the generation of fine cracks in the foil body during processing can be suppressed. Therefore, the progression of corrosion in the ferritic stainless steel foil is suppressed. As a result, the corrosion resistance of the ferritic stainless steel foil can be improved.

[0021] Based on the above findings, the inventors have investigated the relationship between the diffraction intensity of each lattice plane in the foil body, which is obtained by focusing X-ray diffraction measurement, and corrosion resistance. As a result, the diffraction intensity I of the {110} plane, which is obtained by focusing X-ray diffraction measurement of the foil body, １１０ and the diffraction intensity I of the {200} plane ２００ and the diffraction intensity I of the {211} plane ２１１ However, the present inventors have found that if formula (1) is satisfied, excellent corrosion resistance can be obtained in the ferritic stainless steel foil. １１０ / (I １１０ +I ２００ +I ２１１ ) ≦0.16 (1)

[0022] The ferritic stainless steel foil of this embodiment, the electrode of this embodiment, and the battery of this embodiment have been completed based on the above technical concept, and have the following configurations.

[0023] The ferritic stainless steel foil of the first configuration comprises a foil body made of ferritic stainless steel, and a diffraction intensity I of the {110} plane obtained by focusing X-ray diffraction measurement of the foil body. １１０ and the diffraction intensity I of the {200} plane ２００ and the diffraction intensity I of the {211} plane ２１１ and satisfy the formula (1). １１０ / (I １１０ +I ２００ +I ２１１ ) ≦0.16 (1)

[0024] The ferritic stainless steel foil of the second configuration is the ferritic stainless steel foil of the first configuration, further comprising: a thickness of I defined by formula (2) in a region from a depth of 0.38 μm to a depth of 2.82 μm starting from the surface of the foil body. Ｒ The maximum value of I ＭＡＸ is 15.0 or more. Ｒ = II １１０ / II ２１１ (2) Here, II in formula (2) １１０ is substituted with the integrated intensity of the {110} plane obtained by grazing incidence X-ray diffraction, and II ２１１ is substituted with the integrated intensity of the {211} plane obtained by grazing incidence X-ray diffraction.

[0025] A ferritic stainless steel foil of a third configuration is the ferritic stainless steel foil of the first or second configuration, wherein the chemical composition of the foil body contains, in mass%, C: 0.001 to 0.030%, Si: 0.01 to 1.00%, Mn: 0.01 to 1.00%, P: 0.050% or less, S: 0.030% or less, Ni: 0.01 to 0.50%, Cr: 12.00 to 20.00%, Mo: 0.01 to 2.50%, N: 0 to 0.100%, Ti: 0 to 0.80%, Nb: 0 to 0.80%, and Zr: 0 to 0.80%, with the balance consisting of Fe and impurities.

[0026] The electrode of the first configuration comprises a ferritic stainless steel foil of any one of the first to third configurations, and an electrode mixture layer formed on the surface of the ferritic stainless steel foil.

[0027] The battery of the first configuration comprises: electrodes of the first configuration; and an electrolyte.

[0028] The battery of the second configuration is the battery of the first configuration, wherein the electrolyte is a sulfide-based solid electrolyte.

[0029] The ferritic stainless steel foil of this embodiment, the electrode of this embodiment, and the battery of this embodiment will be described in detail below. Note that "%" regarding elements means mass % unless otherwise specified.

[0030] [Configuration of Ferritic Stainless Steel Foil] The ferritic stainless steel foil of this embodiment has a foil body made of ferritic stainless steel. That is, the ferritic stainless steel foil of this embodiment may be composed only of a foil body made of ferritic stainless steel. Here, ferritic stainless steel means a steel having a Cr content of 10.5% or more and a microstructure mainly composed of ferrite.

[0031] [Regarding Formula (1)] In the ferritic stainless steel foil of this embodiment, the diffraction intensity I of the {110} plane obtained by focusing X-ray diffraction measurement of the foil body is １１０ and the diffraction intensity I of the {200} plane ２００ and the diffraction intensity I of the {211} plane ２１１ and satisfy the formula (1). １１０ / (I １１０ +I ２００ +I ２１１ ) ≦0.16 (1)

[0032] F1 is defined as follows: F1=I １１０ / (I １１０ +I ２００ +I ２１１) F1 is an index of the orientation of the {110} plane in the depth direction. If F1 is 0.16 or less, the proportion of {110} planes oriented parallel or perpendicular to the depth direction within the foil body is sufficiently low. In this case, the occurrence of fine cracks in the foil body during processing can be sufficiently suppressed. As a result, the ferritic stainless steel foil exhibits excellent corrosion resistance.

[0033] The lower limit of F1 is not particularly limited. In consideration of normal industrial production, the lower limit of F1 is, for example, 0, more preferably 0.01. The upper limit of F1 is preferably 0.14, more preferably 0.12.

[0034] [Method for measuring the diffraction intensity of each lattice plane] Diffraction intensity I of {110} plane １１０ , the diffraction intensity I of the {200} plane ２００ , and the diffraction intensity I of the {211} plane ２１１ is calculated in the following way:

[0035] A test piece is taken from the surface of the foil body of the ferritic stainless steel foil as the observation surface. The size of the test piece is not particularly limited, but it is preferable that it is larger than the X-ray irradiation area. The location from which the test piece is taken is also not particularly limited, but for example, the center of the width of the foil body. Focused X-ray diffraction measurement is performed on the observation surface of the test piece using an X-ray diffractometer to obtain a diffraction profile. The incident direction of the X-rays is parallel to a plane containing the rolling direction and a direction perpendicular to the surface of the foil body. For example, an ULTIMA-III manufactured by Rigaku Corporation can be used for the measurement. The X-ray diffractometer uses a CuKα source for the measurement. The acceleration voltage, acceleration current, and sampling width for the X-ray diffraction measurement are 40 kV, 40 mA, 1 / 2° divergence slit, 0.2° / min scan speed, and 0.02° sampling width. A monochromator is placed in front of the detector. Peaks for the {110}, {200}, and {211} planes are identified from the obtained diffraction profile. From the peaks of each identified lattice plane, the diffraction intensity I of the {110} plane １１０ , the diffraction intensity I of the {200} plane ２００ , and the diffraction intensity I of the {211} plane ２１１ Ask for.

[0036] Obtained I １１０ , I２００ , and I ２１１ F1 is calculated based on the above formula. Note that F1 is a value rounded off to two decimal places.

[0037] [I Ｒ The maximum value of I ＭＡＸ Regarding] Preferably, in the ferritic stainless steel foil of the present embodiment, in a region from a depth of 0.38 μm to a depth of 2.82 μm starting from the surface of the foil body, I defined by formula (2) Ｒ The maximum value of I ＭＡＸ is 15.0 or more. Ｒ = II １１０ / II ２１１ (2) Here, II in formula (2) １１０ is substituted with the integrated intensity of the {110} plane obtained by grazing incidence X-ray diffraction, and II ２１１ is substituted with the integrated intensity of the {211} plane obtained by grazing incidence X-ray diffraction.

[0038] In the above-mentioned F1, the focus was on the {110} crystal orientation throughout the entire foil body. The inventors further focused on the {110} crystal orientation in the foil body, particularly in the surface layer, and investigated means for further improving the corrosion resistance of ferritic stainless steel foil. Here, the surface layer is defined as the region from the surface of the foil body to a depth of 2.82 μm.

[0039] Corrosion of ferritic stainless steel foil progresses from the surface of the foil body in the depth direction. Here, the {110} plane, which is a close-packed atomic plane, has a short interatomic distance within the plane, resulting in a strong interatomic bond. Therefore, the more perpendicularly oriented the {110} plane is to the depth direction at a certain depth, the slower the corrosion rate at that depth. In particular, by increasing the orientation of the {110} plane in the depth direction in the surface layer of the foil body, the progression of corrosion originating from the surface can be significantly suppressed. As described above, the higher the orientation of the {110} plane in the depth direction, the more likely cracks will occur during processing. However, in the surface layer, increasing the orientation of the {110} plane can actually suppress the progression of corrosion. In other words, if the {110} plane is oriented in the depth direction in the surface layer while the overall crystal orientation of the foil body can be adjusted to satisfy formula (1), the corrosion resistance of the ferritic stainless steel foil can be further improved.

[0040] The crystal orientation in the surface layer of the foil body can be evaluated by grazing incidence X-ray diffraction (GIXD). Unlike the focusing method, grazing incidence X-ray diffraction can selectively measure the crystal orientation up to any depth starting from the surface. Furthermore, in measuring the surface layer of the foil body using grazing incidence X-ray diffraction, peaks of the {110} plane and the {211} plane are mainly detected. At a certain depth, the greater the ratio of the integrated intensity of the {110} plane to the integrated intensity of the {211} plane, the more the {110} plane oriented perpendicular to the depth direction is present at that depth. In other words, to further improve the corrosion resistance of ferritic stainless steel foil, it is preferable that the ratio of the integrated intensity of the {110} plane to the integrated intensity of the {211} plane in the surface layer of the foil body is large.

[0041] Here, I Ｒ is an index that represents the ratio of the amount of {110} planes to the amount of {211} planes that constitute the crystal orientation in the depth direction at an arbitrary depth position starting from the surface of the foil body. Ｒ The maximum value of I ＭＡＸis the surface layer I Ｒ It is an index that represents the maximum value of

[0042] I in the region from the surface of the foil body at a depth of 0.38 μm to a depth of 2.82 μm Ｒ The maximum value of I ＭＡＸ If the ratio of the integrated intensity of the {110} plane to the integrated intensity of the {211} plane is 15.0 or more, the ratio of the integrated intensity of the {110} plane to the integrated intensity of the {211} plane is sufficiently large in the surface layer. In this case, the orientation of the {110} plane in the depth direction is sufficiently high in the surface layer, and the progression of corrosion originating from the surface layer can be sufficiently suppressed. As a result, the ferritic stainless steel foil can achieve even better corrosion resistance.

[0043] I ＭＡＸ The lower limit of I is more preferably 20.0, and even more preferably 30.0. ＭＡＸ Considering normal industrial production, the upper limit of I ＭＡＸ The upper limit is, for example, 120.0.

[0044] [Method for measuring the integrated intensity of each lattice plane] Integrated intensity II of {110} plane １１０ , and the integrated intensity of the {211} plane II ２１１ is calculated in the following way:

[0045] A test piece is taken from the surface of the foil body of the ferritic stainless steel foil as the observation surface. The size of the test piece is not particularly limited. The location from which the test piece is taken is also not particularly limited, but for example, the center of the width of the foil body. Measurement is performed on the observation surface of the test piece by grazing incidence X-ray diffraction. Specifically, the radiation source is CoKα radiation, the tube voltage is 40 kV, and the tube current is 135 mA. The X-ray beam is collimated using a mirror. For example, a SmartLab manufactured by Rigaku Corporation can be used for the measurement. For the measurement, a 5.0° Soller slit is installed on the incident side and a 5.0° Soller slit is installed on the receiving side, a parallel slit analyzer (PSA) is 0.5°, receiving slit 1 (RS1) = 1.0 mm, and receiving slit 2 (RS2) = open. The incident direction of the X-rays is parallel to a plane including the rolling direction and the direction perpendicular to the surface of the foil body.

[0046] The measurement depth from the observation surface at each incidence angle of grazing incidence X-ray diffraction can be calculated from the X-ray penetration depth t that satisfies μt = 1, where μ is the linear absorption coefficient. To calculate the linear absorption coefficient μ, the mass absorption coefficient of 19.11Cr-1.77Mo-78.38Fe (mass%), which corresponds to SUS444, is used, and the density is 7.75 g / cm. ３ is used. Based on this conversion method, when the incident angle is 2.0° to 15.0°, the measurement depth corresponds to a depth of 0.38 μm to a depth of 2.82 μm. Therefore, measurements are performed under nine conditions, with incident angles of 2.0°, 3.0°, 4.0°, 5.0°, 6.0°, 8.0°, 10.0°, 12.0°, and 15.0°. From the diffraction profiles obtained under each condition, the peaks of the {110} plane and the {211} plane are identified. From the peaks of each lattice plane, the integrated intensity II of the {110} plane is calculated. １１０ and the integrated intensity of the {211} plane II ２１１ Calculate.

[0047] Obtained II １１０ and II ２１１ Based on the formula (2), I under the conditions Ｒ Calculate the following. Ｒ is a value obtained by rounding off the first decimal place to the nearest tenth. I obtained under nine conditions corresponding to measurement depths of 0.38 to 2.82 μm Ｒ The maximum value of I ＭＡＸ Let's say.

[0048] [Chemical Composition] In the ferritic stainless steel foil of this embodiment, the chemical composition of the foil body may be the chemical composition of a known ferritic stainless steel.

[0049] The chemical composition of the foil body of the ferritic stainless steel foil of this embodiment may satisfy, for example, any one selected from the group consisting of SUS405, SUS410L, SUS429, SUS430, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS443J1, SUS444, SUS445J1, SUS445J2, SUS447J1, and SUSXM27 as specified in JIS G 4305 (2015).

[0050] The chemical composition of the foil body of the ferritic stainless steel foil of this embodiment may further satisfy, for example, any one selected from the group consisting of 403, 405, 409L, 410, 410L, 410S, 415, 420J1, 420J2, 420, 429, 429J1, 430, 430J1L, 430LX, 430Ti, 434, 436, 436J1L, 439, 441, 444, 445, 445J1, 445J2, 446, 447, and 448 as specified in ASTM A 240 (2006).

[0051] The chemical composition of the foil body of the ferritic stainless steel foil of this embodiment may contain, for example, the following elements.

[0052] C: 0.001 to 0.030% Carbon (C) increases the strength of ferritic stainless steel foil. When the C content is 0.001% or more, the above effect is sufficiently achieved. On the other hand, when the C content is 0.030% or less, the formation of a Cr-deficient layer due to the generation of Cr carbides can be suppressed. As a result, embrittlement of the oxide film is suppressed, and the corrosion resistance of the ferritic stainless steel foil is improved. Therefore, the preferred C content is 0.001 to 0.030%. A more preferred lower limit of the C content is 0.003%, and even more preferred is 0.005%. A more preferred upper limit of the C content is 0.025%, and even more preferred is 0.020%.

[0053] Si: 0.01 to 1.00% Silicon (Si) deoxidizes steel during the steelmaking process. If the Si content is 0.01% or more, the above effect is sufficiently obtained. On the other hand, if the Si content is 1.00% or less, the workability of the ferritic stainless steel foil is improved. Therefore, the preferred Si content is 0.01 to 1.00%. A more preferred lower limit of the Si content is 0.03%, and even more preferred is 0.05%. A more preferred upper limit of the Si content is 0.90%, and even more preferred is 0.80%.

[0054] Mn: 0.01 to 1.00% Manganese (Mn) increases the strength of ferritic stainless steel foil. If the Mn content is 0.01% or more, the above effect is sufficiently obtained. On the other hand, if the Mn content is 1.00% or less, the corrosion resistance of the ferritic stainless steel foil is improved. Therefore, the preferred Mn content is 0.01 to 1.00%. A more preferred lower limit of the Mn content is 0.03%, and even more preferred is 0.05%. A more preferred upper limit of the Mn content is 0.90%, and even more preferred is 0.80%.

[0055] P: 0.050% or less Phosphorus (P) is an impurity. If the P content is 0.050% or less, the workability and corrosion resistance of the ferritic stainless steel foil are improved. Therefore, the preferred P content is 0.050% or less. The lower the P content, the more preferable it is. However, if the P content is reduced too much, the manufacturing cost increases. Therefore, considering normal industrial production, the preferred lower limit of the P content is more than 0%, more preferably 0.001%, and even more preferably 0.010%. The more preferred upper limit of the P content is 0.045%, and even more preferably 0.040%.

[0056] S: 0.030% or less Sulfur (S) is an impurity. If the S content is 0.030% or less, the workability and corrosion resistance of the ferritic stainless steel foil are improved. Therefore, the preferred S content is 0.030% or less. The lower the S content, the more preferable it is. However, if the S content is reduced too much, the manufacturing cost increases. Therefore, considering normal industrial production, the preferred lower limit of the S content is more than 0%, more preferably 0.001%, and even more preferably 0.010%. The more preferred upper limit of the S content is 0.025%, and even more preferably 0.020%.

[0057] Ni: 0.01 to 0.50% Nickel (Ni) improves the corrosion resistance of ferritic stainless steel foil. If the Ni content is 0.01% or more, the above effect is sufficiently obtained. On the other hand, if the Ni content is 0.50% or less, the workability of the ferritic stainless steel foil is improved. Therefore, the Ni content is preferably 0.01 to 0.50%. A more preferable lower limit of the Ni content is 0.03%, and even more preferably 0.05%. A more preferable upper limit of the Ni content is 0.40%, and even more preferably 0.30%.

[0058] Cr: 12.00 to 20.00% Chromium (Cr) forms an oxide film and improves the corrosion resistance of ferritic stainless steel foil. When the Cr content is 12.00% or more, the above effect is sufficiently obtained. On the other hand, when the Cr content is 20.00% or less, the workability of the ferritic stainless steel foil is improved. Therefore, the preferred Cr content is 12.00 to 20.00%. A more preferred lower limit of the Cr content is 12.50%, and even more preferred is 13.00%. A more preferred upper limit of the Cr content is 19.00%, and even more preferred is 18.00%.

[0059] Mo: 0.01 to 2.50% Molybdenum (Mo) enhances the strength and corrosion resistance of ferritic stainless steel foil. When the Mo content is 0.01% or more, the above effects are sufficiently obtained. On the other hand, when the Mo content is 2.50% or less, the workability of the ferritic stainless steel foil is improved. Therefore, the preferred Mo content is 0.01 to 2.50%. A more preferred lower limit of the Mo content is 0.03%, and even more preferred is 0.05%. A more preferred upper limit of the Mo content is 2.40%, and even more preferred is 2.30%.

[0060] N: 0 to 0.100% Nitrogen (N) does not necessarily need to be contained. On the other hand, if the N content is 0.100% or less, the strength of the ferritic stainless steel foil is increased. Therefore, the N content is preferably 0 to 0.100%. A more preferable lower limit of the N content is more than 0%, even more preferably 0.001%, and even more preferably 0.003%. A more preferable upper limit of the N content is 0.090%, and even more preferably 0.080%.

[0061] Ti: 0 to 0.80% Titanium (Ti) does not necessarily need to be contained. On the other hand, if Ti is contained in an amount of 0.80% or less, it fixes C and suppresses the formation of Cr carbides. Therefore, the formation of a Cr-deficient layer is suppressed. As a result, embrittlement of the oxide film is suppressed, and the corrosion resistance of the ferritic stainless steel foil is improved. Therefore, the preferred Ti content is 0 to 0.80%. A more preferred lower limit of the Ti content is more than 0%, more preferably 0.01%, and even more preferably 0.03%. A more preferred upper limit of the Ti content is 0.70%, and even more preferably 0.60%.

[0062] Nb: 0 to 0.80% Niobium (Nb) does not necessarily have to be contained. On the other hand, if the Nb content is 0.80% or less, the corrosion resistance of the ferritic stainless steel foil is improved. Therefore, the preferred Nb content is 0 to 0.80%. A more preferred lower limit of the Nb content is over 0%, more preferably 0.01%, and even more preferably 0.03%. A more preferred upper limit of the Nb content is 0.70%, and even more preferably 0.60%.

[0063] Zr: 0 to 0.80% Zirconium (Zr) does not necessarily have to be contained. On the other hand, if the Zr content is 0.80% or less, the corrosion resistance of the ferritic stainless steel foil is improved. Therefore, the Zr content is preferably 0 to 0.80%. A more preferable lower limit of the Zr content is more than 0%, more preferably 0.01%, and even more preferably 0.03%. A more preferable upper limit of the Zr content is 0.70%, and even more preferably 0.60%.

[0064] The balance of the preferred chemical composition of the foil body of the ferritic stainless steel foil of this embodiment consists of Fe and impurities. Here, the impurities in the chemical composition refer to substances that are mixed in from raw materials or the manufacturing environment during industrial production of the ferritic stainless steel foil, and are acceptable within a range that does not adversely affect the ferritic stainless steel foil of this embodiment.

[0065] [Thickness] The thickness of the foil body of the ferritic stainless steel foil of this embodiment is not particularly limited, and is, for example, 6 to 20 μm.

[0066] [Uses of the Ferritic Stainless Steel Foil of the Present Embodiment] The ferritic stainless steel foil of the present embodiment has excellent corrosion resistance. Therefore, it is suitable for use as a current collector in an all-solid-state battery using a highly corrosive sulfide-based solid electrolyte. The ferritic stainless steel foil of the present embodiment can also be used for purposes other than as a current collector in a secondary battery.

[0067] [Method for manufacturing ferritic stainless steel foil of this embodiment] An example of a method for manufacturing the ferritic stainless steel foil of this embodiment will be described. The method for manufacturing the ferritic stainless steel foil described below is one example for manufacturing the ferritic stainless steel foil of this embodiment. Therefore, the ferritic stainless steel foil having the above-mentioned configuration may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferred example of a method for manufacturing the ferritic stainless steel foil of this embodiment.

[0068] An example of the method for producing the ferritic stainless steel foil of this embodiment includes the following steps: (Step 1) Material preparation step (Step 2) Intermediate cold rolling step (Step 3) Intermediate annealing step (Step 4) Final cold rolling step Each step will be described below.

[0069] [(Step 1) Material Preparation Step] In the material preparation step, a ferritic stainless steel sheet having a thickness of several hundred μm to several mm is prepared as the material for producing the ferritic stainless steel foil of this embodiment. The material is, for example, a cold-rolled coil obtained by cold-rolling a hot-rolled coil. The material may be prepared by manufacturing or by purchasing from a third party. In other words, the material preparation step is not particularly limited.

[0070] When manufacturing a raw material, for example, it is manufactured by the following method: Produce molten steel having a desired chemical composition. Produce a slab using the molten steel by continuous casting. Produce the slab by hot working and cold rolling to produce a steel plate with a thickness of several hundred μm to several mm. Through the above steps, the raw material for the ferritic stainless steel foil of this embodiment is prepared.

[0071] [(Step 2) Intermediate Cold Rolling Step] In the intermediate cold rolling step, cold rolling is performed on the prepared material to produce an intermediate steel plate having a thickness of several tens of μm to several hundreds of μm. In the intermediate cold rolling step, cold rolling may be performed using a continuous rolling mill equipped with a plurality of rolling stands arranged in a row, or cold rolling may be performed using a reverse rolling mill. The cumulative reduction rate in the intermediate cold rolling step is not particularly limited.

[0072] The intermediate cold rolling step satisfies the following conditions. As will be described later, the intermediate cold rolling step and the intermediate annealing step may be alternately repeated multiple times. In this case, it is sufficient that the following condition is satisfied in the final intermediate cold rolling step. (Condition 1) Maximum rolling reduction R1 in one pass ＭＡＸ The condition 1 is 10.0% or more. Condition 1 will be explained below.

[0073] [Maximum rolling reduction in one pass R1 ＭＡＸ Regarding the maximum rolling reduction R1 in one pass] Here, "pass" means an operation in which the material to be rolled passes through one rolling stand once. In the intermediate cold rolling process, cold rolling consisting of multiple passes is carried out. ＭＡＸ " means the reduction rate in the pass with the largest reduction rate in the intermediate cold rolling process. Maximum reduction rate R1 in one pass ＭＡＸThe larger the reduction ratio R1 in one pass, the larger the strain that can be accumulated inside the intermediate steel sheet after the intermediate cold rolling process. Here, the larger the amount of strain accumulated in the intermediate steel sheet after the intermediate cold rolling process, the more recrystallization is promoted in the subsequent intermediate annealing process. In addition, the more recrystallization is promoted, the lower the orientation of the {110} plane in the depth direction. ＭＡＸ If the maximum rolling reduction R1 in one pass is 10.0% or more, a sufficient amount of strain is introduced into the interior of the intermediate steel sheet. In this case, provided that the intermediate annealing process satisfies Condition 2 described below, the orientation of the {110} plane is sufficiently reduced even inside the intermediate steel sheet. As a result, F1 in the manufactured ferritic stainless steel foil satisfies Formula (1). ＭＡＸ Considering normal industrial production, the maximum rolling reduction rate R1 in one pass is ＭＡＸ The upper limit is, for example, 40.0%.

[0074] [(Step 3) Intermediate Annealing Step] In the intermediate annealing step, the intermediate steel sheet after the intermediate cold rolling step is subjected to bright annealing. Bright annealing is an annealing treatment carried out in an extremely low oxygen atmosphere. The intermediate steel sheet that has been subjected to bright annealing has its surface hardly oxidized and can maintain its surface gloss. The extremely low oxygen atmosphere in bright annealing is preferably an H ２ Gas and N ２ The atmosphere is a mixed gas of N and N gas. ２ The volume fraction is, for example, 35 to 65%.

[0075] In the bright annealing performed in the intermediate annealing step, the intermediate steel sheet is passed through a heat treatment furnace in an extremely low-oxygen atmosphere at a predetermined speed. The heat treatment furnace is divided into a heating chamber, an annealing chamber, and a rapid cooling chamber in the order in which the intermediate steel sheet passes through. In the heating chamber, the intermediate steel sheet is heated and held at a predetermined temperature. Here, the temperature in the heating chamber is defined as the heating temperature T (°C), and the time it takes for the intermediate steel sheet to pass through the heating chamber is defined as the holding time t (seconds). In the annealing chamber, the intermediate steel sheet is cooled from the heating temperature T (°C) to 400°C at a predetermined cooling rate. In the rapid cooling chamber, the intermediate steel sheet cooled to 400°C is rapidly cooled to room temperature. The rapid cooling method is not particularly limited, but may be, for example, air cooling.

[0076] The intermediate cold rolling step and the intermediate annealing step may be alternately repeated multiple times. For example, when the intermediate cold rolling step and the intermediate annealing step are alternately repeated twice, a first intermediate cold rolling step and a first intermediate annealing step are performed, and then a second intermediate cold rolling step and a second intermediate annealing step are performed.

[0077] The intermediate annealing step satisfies the following condition. When the intermediate annealing step is performed multiple times, the following condition should be satisfied in the final intermediate annealing step. (Condition 2) The heat treatment parameter FA defined by formula (A) is 2133 or more. FA = (T - 780) × (log １０ t+30) (A) Here, the heating temperature T (°C) is substituted for T in the formula (A), and the holding time t (seconds) is substituted for t.

[0078] It is preferable that the intermediate annealing step further satisfies the following condition: When the intermediate annealing step is performed multiple times, the following condition should be satisfied in the last intermediate annealing step: (Preferred condition 1) The heat treatment parameter FA defined by formula (A) is 8418 or less. Condition 2 and preferred condition 1 will be explained below.

[0079] [Regarding the heat treatment parameter FA] In the intermediate annealing step, the higher the heating temperature T or the longer the holding time t, the more recrystallization is promoted, and the lower the orientation of the {110} plane in the depth direction. If FA is 2133 or more, the orientation of the {110} plane in the foil body in the depth direction can be sufficiently reduced. In this case, assuming that the intermediate cold rolling step satisfies condition 1, F1 in the manufactured ferritic stainless steel foil satisfies formula (1). Therefore, FA is set to 2133 or more.

[0080] On the other hand, if the FA is 8418 or less, excessive deterioration of the {110} plane orientation in the surface layer of the foil body can be suppressed. In this case, on the premise that the final cold rolling step satisfies the preferred condition 2 described later, the I in the manufactured ferritic stainless steel foil can be ＭＡＸ Therefore, it is preferable that FA is 8418 or less.

[0081] [(Step 4) Final Cold Rolling Step] In the final cold rolling step, the intermediate steel sheet after the intermediate annealing step is cold rolled again to obtain a ferritic stainless steel foil having a foil body of a predetermined thickness. In the final cold rolling step, a well-known cold rolling mill may be used. For example, cold rolling may be performed using a continuous rolling mill equipped with multiple rolling stands arranged in a row, or cold rolling may be performed using a reverse rolling mill. The cumulative reduction ratio in the final cold rolling step is not particularly limited.

[0082] In the final cold rolling process, the following condition is satisfied: (Preferred condition 2) Maximum rolling reduction R2 in one pass ＭＡＸ is 26% or less. Condition 2 will be explained below.

[0083] [Maximum reduction rate in one pass R2 ＭＡＸ In the final cold rolling process, cold rolling consisting of multiple passes is carried out. ＭＡＸ " means the reduction rate in the pass with the largest reduction rate in the final cold rolling process. If there is even one pass with an excessively large reduction rate, intense processing heat will occur. As a result, the temperature will rise excessively in the surface layer of the intermediate steel sheet, and the orientation of the {110} plane in the depth direction will decrease. The maximum reduction rate in one pass, R2 ＭＡＸ When the rolling reduction is 26% or less, it means that there is no pass with a rolling reduction exceeding 26%. In this case, the heat generated by working in the surface layer is sufficiently suppressed, and the excessive decrease in the orientation of the {110} plane in the depth direction is also suppressed. As a result, assuming that the intermediate annealing step satisfies the preferred condition 1, the I in the manufactured ferritic stainless steel foil can be reduced. ＭＡＸ Therefore, the maximum rolling reduction rate R2 in one pass is ＭＡＸ It is preferable that the maximum rolling reduction rate R2 in one pass is 26% or less. ＭＡＸ The lower limit of is not particularly limited. Considering normal industrial production, the maximum rolling reduction rate R2 ＭＡＸ The lower limit is, for example, 5%.

[0084] The ferritic stainless steel foil of this embodiment is manufactured by the above-described manufacturing method.

[0085] [Electrode] The electrode of this embodiment comprises the ferritic stainless steel foil of this embodiment and an electrode mixture layer formed on the surface of the ferritic stainless steel foil. That is, in the electrode of this embodiment, the ferritic stainless steel foil of this embodiment is used as a current collector. The electrode of this embodiment may be a positive electrode or a negative electrode. That is, the configuration of the electrode of this embodiment is not particularly limited as long as it comprises the ferritic stainless steel foil of this embodiment and an electrode mixture layer.

[0086] [Electrode Mixture Layer] In the electrode of this embodiment, the electrode mixture layer is not particularly limited as long as it has a known configuration. The electrode mixture layer contains an active material. Note that the electrode mixture layer may contain materials other than the active material. The electrode mixture layer may contain, for example, a binder and a conductive additive. Furthermore, the electrode mixture layer used in an all-solid-state battery may contain, for example, a solid electrolyte.

[0087] [Active Material] In the electrode of this embodiment, the active material contained in the electrode mixture layer is not particularly limited, and a well-known active material can be used. When the electrode is a positive electrode, the positive electrode active material is, for example, LiCoO ２ And LiNi １／３ Co １／３ Mn １／３ O ２ and ternary systems such as LiFePO ４ Olivine system represented by S, Fe ２ S, Mo ３ S ４ When the electrode is a negative electrode, the negative electrode active material may be, for example, a carbon-based material represented by graphite, an alloy material represented by CuSn alloy and NiTiSi alloy, an Si-based material represented by Si and SiO, or Li ４ Ti ５ O １２ and oxide-based materials represented by the following.

[0088] [Binder] In the electrode of this embodiment, the binder contained in the electrode mixture layer is not particularly limited, and well-known binders can be used. The binder may be any one or more selected from the group consisting of rubbery polymers represented by styrene-butadiene rubber and isoprene rubber, synthetic resins represented by polyethylene, polyimide, polyacrylic acid, and polyamide, styrene-butadiene-styrene block copolymers or hydrogenated products thereof, thermoplastic elastomers such as styrene-ethylene-butadiene, styrene copolymers, styrene-isoprene, or styrene block copolymers or hydrogenated products thereof, soft resinous polymers represented by syndiotactic-1,2-polybutadiene, ethylene-vinyl acetate copolymers, and copolymers of ethylene and an α-olefin having 3 to 12 carbon atoms, and fluorinated polymers represented by polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymers, polyvinylidene fluoride, polypentafluoropropylene, and polyhexafluoropropylene.

[0089] [Conductive additive] In the electrode of this embodiment, the conductive additive contained in the electrode mixture layer is not particularly limited, and any known conductive additive may be used. The conductive additive may be, for example, one or more selected from the group consisting of graphite material, acetylene black, carbon black, ketjen black, carbon fiber, carbon nanotube, and graphene.

[0090] [Electrode Manufacturing Method] The electrode manufacturing method of this embodiment is not particularly limited. The electrode of this embodiment is manufactured by a well-known method using the ferritic stainless steel foil of this embodiment as a current collector. The electrode manufacturing method of this embodiment includes, for example, an electrode slurry preparation step and an electrode mixture layer formation step.

[0091] [Electrode Slurry Preparation Step] In the electrode slurry preparation step, a composition (electrode slurry) for forming an electrode mixture layer is prepared. The electrode slurry may be prepared according to the electrode mixture layer to be obtained. For example, the electrode slurry may be prepared by kneading an active material, a binder, and a solvent. For example, the electrode slurry may be prepared by further kneading an active material, a conductive additive, a binder, and a solvent. Furthermore, when preparing an electrode slurry to be used in an all-solid-state battery, the electrode slurry may be prepared by kneading an active material, a solvent, a solid electrolyte, and a binder. The kneading method is adjusted appropriately depending on the active material, the conductive additive, the binder, the solid electrolyte, and the solvent. That is, the electrode slurry preparation step may be performed by a known method.

[0092] [Electrode Mixture Layer Forming Step] In the electrode mixture layer forming step, an electrode mixture layer is formed on the surface of the ferritic stainless steel foil of this embodiment. Specifically, the kneaded electrode slurry is applied to the ferritic stainless steel foil of this embodiment. The application method is not particularly limited and may be a well-known method. For example, application may be performed using an applicator with a gap. Furthermore, application may be performed by spraying using a sprayer.

[0093] The electrode of this embodiment can be manufactured by the above steps.

[0094] [Battery] The battery of this embodiment includes the electrode of this embodiment and an electrolyte. As long as the battery of this embodiment includes the electrode of this embodiment, other configurations may be well-known and are not particularly limited. The battery of this embodiment may further include, for example, a separator. The shape of the battery of this embodiment is not particularly limited, and may be cylindrical, prismatic, coin-shaped, or sheet-shaped. Furthermore, the battery of this embodiment may be a secondary battery or a primary battery. When the battery according to this embodiment is a secondary battery, it may be, for example, a non-aqueous electrolyte secondary battery, an aqueous electrolyte secondary battery, or an all-solid-state secondary battery.

[0095] [Electrolyte] The electrolyte conducts ions between the positive electrode and the negative electrode. In the battery of this embodiment, the electrolyte is not particularly limited, and a well-known electrolyte can be used. The electrolyte may be a liquid electrolytic solution or a solid electrolyte.

[0096] The electrodes of the battery of this embodiment use the ferritic stainless steel foil of this embodiment as a current collector. Therefore, the current collector has excellent corrosion resistance. Therefore, the electrolyte of the battery of this embodiment can be a sulfide-based solid electrolyte, which is highly corrosive to the current collector. The sulfide-based solid electrolyte can be, for example, Li ３ P.S. ４ and Li ７ P ３ S １１ LPS systems, such as Li ６ P.S. ５ Cl ｘ Br （１－ｘ） Argyrodite type represented by (0≦x≦1) and Li １０ GeP ２ S １２ and Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ and thiolisicones represented by the following:

[0097] [Method for Manufacturing Battery] The method for manufacturing the battery of the present embodiment is not particularly limited. The battery of the present embodiment is manufactured, for example, by a well-known method, by placing a laminate of the electrode of the present embodiment, an electrolyte, and a counter electrode in a battery case.

[0098] The effects of the ferritic stainless steel foil of this embodiment will be explained more specifically using examples. The conditions in the following examples are one example of conditions adopted to confirm the feasibility and effects of the ferritic stainless steel foil of this embodiment. Therefore, the ferritic stainless steel foil of this embodiment is not limited to this one example of conditions.

[0099] As a material for producing ferritic stainless steel foil, a steel plate having the chemical composition shown in Table 1 was prepared. The thickness of the steel plate was 300 μm.

[0100]

[0101] The material of each test number was subjected to an intermediate cold rolling process once to produce an intermediate steel plate. Specifically, the material of each test number was cold rolled using a reverse rolling mill. The maximum rolling reduction R1 in one pass for each test number was ＭＡＸ (%) is shown in Table 2.

[0102]

[0103] The intermediate steel sheets after the intermediate cold rolling process were subjected to one intermediate annealing process. Specifically, the intermediate steel sheets of each test number were subjected to 35 to 65 volume % N ２ gas and the remainder is H ２ The heating temperature T (°C), holding time t (seconds), and calculated heat treatment parameter FA for each test number are shown in Table 2.

[0104] The intermediate steel sheet after the intermediate annealing step was subjected to a final cold rolling step. In the final cold rolling step, the intermediate steel sheet of each test number was subjected to cold rolling using a reverse rolling mill to produce a ferritic stainless steel foil having a foil body with a sheet thickness of 10 μm. The maximum rolling reduction R2 in one pass for each test number was ＭＡＸ (%) is shown in Table 2.

[0105] By the above manufacturing process, ferritic stainless steel foils with each test number were manufactured.

[0106] [Regarding Evaluation Tests] The following evaluation tests were carried out on the produced ferritic stainless steel foils of each test number: (Test 1) Diffraction intensity measurement test (Test 2) Integrated intensity measurement test (Test 3) Corrosion resistance evaluation test Each test will be described below.

[0107] [(Test 1) Diffraction Intensity Measurement Test] Based on the method described in the above [Method for Measuring Diffraction Intensity of Each Lattice Plane], the diffraction intensity I of the {110} plane in the foil body of the ferritic stainless steel foil of each test number was measured. １１０ , the diffraction intensity I of the {200} plane ２００ , and the diffraction intensity I of the {211} plane ２１１The obtained I １１０ , I ２００ , and I ２１１ F1 was calculated based on the above. F1 for each test number is shown in Table 3.

[0108]

[0109] [(Test 2) Integrated Intensity Measurement Test] Based on the method described in the above [Method for Measuring Integrated Intensity of Each Lattice Plane], the integrated intensity II of the {110} plane from the 0.38 μm depth position to the 2.82 μm depth position in the foil body of the ferritic stainless steel foil of each test number was measured. １１０ , and the integrated intensity of the {211} plane II ２１１ The obtained II １１０ and II ２１１ From the above, based on the equation (1), I Ｒ is calculated, and I Ｒ The maximum value of I ＭＡＸ The I of each test number was calculated. ＭＡＸ is shown in Table 3.

[0110] [(Test 3) Corrosion Resistance Evaluation Test] The corrosion resistance of the ferritic stainless steel foil of each test number was evaluated by the following method. First, a circular test piece with a diameter of 11 mm was taken from the foil body of the ferritic stainless steel foil. One surface of the test piece was used as the evaluation surface. The developed area ratio Sdr defined in ISO 25178-2:2012 was measured for the evaluation surface of the test piece. The developed area ratio Sdr is an index representing the rate of increase in the surface area of ​​the measured surface compared to a flat surface. Since the corrosion reaction proceeds from the surface of the foil body as the starting point, the greater the developed area ratio Sdr of the test piece, the faster the corrosion progresses.

[0111] The developed area ratio Sdr of the evaluation surface of the test piece was measured using a laser microscope. The laser microscope used was a Keyence Corporation product name: VK-X100. The observation magnification was set to 2000 times, and a measurement area of ​​280 μm × 200 μm was measured. Specifically, four points within the measurement area were measured with an observation field of 145 μm × 109 μm so that the entire range within the measurement area could be measured, and a surface image was obtained. The four obtained surface images were linked using the attached image linking software to obtain a surface image of a measurement area of ​​280 μm × 200 μm. From the surface shape profile obtained by analyzing the surface image of the measurement area, a reference plane was set by cutting 0.3% of the area from the low brightness side, and a three-dimensional image was generated. At this time, filtering was performed using a high-pass filter with a cutoff wavelength of 50 μm. A Gaussian filter was used as the filtering method. The developed area ratio Sdr defined in ISO25178-2:2012 was determined in a 200 μm × 150 μm region of the obtained three-dimensional image.

[0112] Using the test pieces with the respective test numbers for which the developed area ratio Sdr was measured, evaluation cells simulating sulfide-based all-solid-state batteries were fabricated. Specifically, 0.12 g of the sulfide-based solid electrolyte was placed in a mold with an inner diameter of 11 mm, and then pressurized at 300 MPa to form a cylindrical sulfide-based solid electrolyte pellet with a thickness of 700 μm and a bottom diameter of 11 mm. The sulfide-based solid electrolyte contained β-Li ３ P.S. ４ The prepared pellet was placed on the evaluation surface of the test piece of each test number. Furthermore, a cylindrical metal Li foil having a thickness of 1.2 mm and a bottom diameter of 11 mm was placed on top of the sulfide-based solid electrolyte pellet. These were placed in a measurement cell with an inner diameter of 11 mm that could block the outside air, and a pressure of 5 MPa was applied by tightening bolts. The measurement cell was then sealed. Note that the process from preparing the sulfide-based solid electrolyte pellet to sealing the evaluation cell was carried out in a glove box in an Ar atmosphere. Through the above process, an evaluation cell of each test number was prepared.

[0113] Cyclic voltammetry (CV) measurements were performed using the evaluation cells of each test number. In the cyclic voltammetry measurements, the test piece was used as the working electrode, and metal Li foil was used as the counter electrode and reference electrode. Specifically, the voltage was measured for the evaluation cell held at 60 ° C for 24 hours, and the open-circuit voltage V ＯＣ After sweeping from (V) to 3.0 V, it was swept to 0.005 V, and then the open circuit voltage V ＯＣ (V), and the current density (μA / cm ２ The open-circuit voltage V was measured at a sweep rate of 5 mV / sec. A series of voltage sweep processes was counted as one cycle, and this cycle was repeated five times. ＯＣ was 2.0 to 2.5 V for all evaluation cells of all test numbers.

[0114] Based on the measurement results, the open circuit voltage V ＯＣ The current density (μA / cm) flowing during the sweep from 0.0 V to 3.0 V ２ ) was integrated by the time (seconds) it took to sweep. Furthermore, the integrated value was divided by the developed area ratio Sdr to eliminate the influence of minute irregularities on the evaluation surface of the test piece, and the result was calculated as C ｎ (μC / cm ２ ) was defined as follows. ｎ (μC / cm ２ ) is the open circuit voltage V ＯＣ The time elapsed from the start of the sweep from (V) to 3.0 V is defined as the test time t (seconds), and the time when 3.0 V is reached is defined as t ３．０ (seconds), and the current density flowing through the evaluation cell at test time t (seconds) is I(t) (μA / cm ２ ) and the developed area ratio of the test piece is Sdr, it can be calculated by the following formula.

[0115] C １ ~C ５ The sum of these is the integrated current value C (μC / cm ２ ) and was used as an index representing the progress of the corrosion reaction in the test piece. ２ ) can be calculated using the following formula: C = C １ +C２ +C ３ +C ４ +C ５ The integrated current value C (μC / cm ２ ) are shown in Table 3. When the integrated current value C is 7500 μC / cm ２ Super ~8500μC / cm ２ When the integrated current value C was 7,500 μC / cm ２ When the integrated current value C was 8,500 μC / cm or less, it was determined that even better corrosion resistance was obtained. ２ When the value exceeded this, it was determined that excellent corrosion resistance was not obtained.

[0116] [Evaluation Results] Referring to Tables 1 to 3, in the ferritic stainless steel foils of test numbers 1 to 9, F1 satisfied formula (1), and therefore excellent corrosion resistance was obtained.

[0117] In the ferritic stainless steel foils of test numbers 1 to 6, I ＭＡＸ Therefore, even better corrosion resistance was obtained.

[0118] On the other hand, in test number 10, the maximum reduction rate R1 in one pass in the intermediate cold rolling process ＭＡＸ (%) was too small. Therefore, F1 did not satisfy formula (1). As a result, excellent corrosion resistance was not obtained.

[0119] In test number 11, FA in the intermediate annealing step was too low, so F1 did not satisfy formula (1), and as a result, excellent corrosion resistance was not obtained.

[0120] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

Claims

1. A foil body made of ferritic stainless steel, wherein the diffraction intensity I of the {110} plane obtained by focusing X-ray diffraction measurement of the foil body is １１０ and the diffraction intensity I of the {200} plane ２００ and the diffraction intensity I of the {211} plane ２１１ and a ferritic stainless steel foil, which satisfies formula (1). １１０ / (I １１０ +I ２００ +I ２１１ ) ≦0.16 (1) 2. The ferritic stainless steel foil according to claim 1, further comprising: a region extending from a depth of 0.38 μm to a depth of 2.82 μm from the surface of the foil body; Ｒ The maximum value of I ＭＡＸ A ferritic stainless steel foil having a surface roughness of 15.0 or more. Ｒ = II １１０ / II ２１１ (2) Here, II in formula (2) １１０ is substituted with the integrated intensity of the {110} plane obtained by grazing incidence X-ray diffraction, and II ２１１ is substituted with the integrated intensity of the {211} plane obtained by grazing incidence X-ray diffraction.

3. A ferritic stainless steel foil according to claim 1, wherein the chemical composition of the foil body contains, in mass%, C: 0.001-0.030%, Si: 0.01-1.00%, Mn: 0.01-1.00%, P: 0.050% or less, S: 0.030% or less, Ni: 0.01-0.50%, Cr: 12.00-20.00%, Mo: 0.01-2.50%, N: 0-0.100%, Ti: 0-0.80%, Nb: 0-0.80%, and Zr: 0-0.80%, with the balance being Fe and impurities.

4. A ferritic stainless steel foil according to claim 2, wherein the chemical composition of the foil body contains, in mass%, C: 0.001-0.030%, Si: 0.01-1.00%, Mn: 0.01-1.00%, P: 0.050% or less, S: 0.030% or less, Ni: 0.01-0.50%, Cr: 12.00-20.00%, Mo: 0.01-2.50%, N: 0-0.100%, Ti: 0-0.80%, Nb: 0-0.80%, and Zr: 0-0.80%, with the balance being Fe and impurities.

5. An electrode comprising the ferritic stainless steel foil according to any one of claims 1 to 4 and an electrode mixture layer formed on the surface of the ferritic stainless steel foil.

6. A battery comprising the electrode according to claim 5 and an electrolyte.

7. The battery according to claim 6, wherein the electrolyte is a sulfide-based solid electrolyte.

Images