Ferritic stainless steel foil, electrode, and battery

Abstract

To provide ferritic stainless steel foil that offers excellent corrosion resistance.SOLUTION: The ferritic stainless steel foil disclosed in this invention comprises a foil main body made of ferritic stainless steel. The average half-width F110 of the peaks of the {110} plane in a region from a 0.38 μm depth position, starting from the surface of the foil main body, to a 2.82 μm depth position, obtained by the grazing incidence X-ray diffraction method, is 0.490° or more.SELECTED DRAWING: None

Description

[Technical Field]

[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. [Background technology]

[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] Traditionally, electrolyte solutions have been used as electrolytes in secondary batteries. However, because electrolyte solutions contain flammable organic solvents, the temperature range in which they can be used is narrow. For this reason, in recent years, development of all-solid-state batteries that use solid electrolytes instead of electrolyte solutions has been progressing. Because all-solid-state batteries do not contain organic solvents, stable battery performance can be achieved 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] Patent Document 1 discloses a ferritic stainless steel sheet for use as a current collector in a sulfide-based solid battery, which 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 being Fe and unavoidable impurities. Patent Document 1 also describes that this ferritic stainless steel sheet exhibits excellent sulfidation resistance when the Cr content is increased to 18.00% or more. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2021 / 006089 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0012] The ferritic stainless steel foil of the present disclosure is A foil body made of ferritic stainless steel, The average half-width F of the peak of the {110} plane in the region from the surface of the foil body to a depth of 0.38 μm to a depth of 2.82 μm, obtained by grazing incidence X-ray diffraction. 110 is 0.490° or more.

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

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

[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. DETAILED DESCRIPTION OF THE INVENTION

[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, adding 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 can reduce the workability of the ferritic stainless steel foil and increase manufacturing costs. Therefore, the present inventors focused on dislocations contained in a ferritic stainless steel foil having a foil body made of ferritic stainless steel, rather than the chemical composition of the foil body.

[0018] Many dislocations are introduced into the foil body of ferritic stainless steel foil to ensure sufficient strength. Furthermore, when ferritic stainless steel foil is used as a current collector, the electrode manufacturing process often involves pressing, which can introduce additional dislocations into the foil body. Dislocations that multiply within the foil body move within the crystal grains, forming cellular tangles (dislocation cells). Eventually, the dislocations within the cells annihilate each other, and the dislocations tangled at the cell walls rearrange to form subgrain boundaries.

[0019] Corrosion of ferritic stainless steel foil occurs preferentially at subgrain boundaries. At subgrain boundaries, the atomic arrangement is significantly more disordered than within the grains, resulting in a high-energy state. This allows the corrosion reaction to proceed more quickly. Furthermore, corrosion of ferritic stainless steel foil begins at the surface layer of the foil itself. In other words, if the formation of subgrain boundaries can be suppressed at the surface layer of the foil itself, the corrosion resistance of ferritic stainless steel foil can be improved.

[0020] As mentioned above, the formation of subgrain boundaries is caused by the formation of dislocation cells associated with dislocation movement. The formation of dislocation cells can be suppressed by uniformly distributing a sufficient number of dislocations within the grain. On the other hand, if too many dislocations are introduced, the dislocation distribution becomes non-uniform, which actually promotes the formation of dislocation cells. Here, if a sufficient number of dislocations are uniformly distributed within the grain, the dislocation density in the foil body will be high. On the other hand, if the number of dislocations is insufficient, or if the dislocations multiply and become non-uniform, forming subgrain boundaries, the dislocation density in the foil body will be low. Therefore, in order to suppress the formation of subgrain boundaries in the surface layer of the foil body, it is effective to increase the dislocation density in the surface layer of the foil body.

[0021] The dislocation density in the surface layer of the foil itself can be evaluated by quantifying the non-uniform lattice strain, an index of dislocation density, using Grazing Incidence X-ray Diffraction (GIXD). Grazing incidence X-ray diffraction allows for selective measurement of the magnitude of non-uniform lattice strain from the surface to any depth. The greater the non-uniform lattice strain in the surface layer, the larger the half-width of the peak for each lattice plane in the diffraction profile obtained by Grazing Incidence X-ray Diffraction. In other words, the larger the half-width of the peak obtained by Grazing Incidence X-ray Diffraction, the higher the dislocation density in the surface layer and the more suppressed the formation of subgrain boundaries. As a result, the progression of corrosion is suppressed, resulting in excellent corrosion resistance.

[0022] Based on the above findings, the inventors have investigated the relationship between the half-width of the peak of the {110} plane obtained by grazing incidence X-ray diffraction and corrosion resistance. The {110} plane is the closest-packed atomic plane in the body-centered cubic lattice of ferritic stainless steel. As a result, the average half-width F of the peak of the {110} plane in the region from the surface of the foil body to the depth of 0.38 μm to 2.82 μm obtained by grazing incidence X-ray diffraction was 110 The present inventors have found that when the angle is 0.490° or more, excellent corrosion resistance can be obtained in the ferritic stainless steel foil.

[0023] 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.

[0024] The ferritic stainless steel foil of the first configuration is A foil body made of ferritic stainless steel, The average half-width F of the peak of the {110} plane in the region from the surface of the foil body to a depth of 0.38 μm to a depth of 2.82 μm, obtained by grazing incidence X-ray diffraction. 110 is 0.490° or more.

[0025] The ferritic stainless steel foil of the second configuration is A ferritic stainless steel foil of a first configuration, further comprising: The average lattice spacing D of the {110} plane in the region from the surface of the foil body to the depth of 0.38 μm to the depth of 2.82 μm is M (nm), and the average lattice spacing D of the {110} plane in the region deeper than 2.82 μm from the surface of the foil body. L (nm) satisfies formula (1). |D M -D L |≦0.0008 (1)

[0026] The ferritic stainless steel foil of the third configuration is A ferritic stainless steel foil having a first or second configuration, The chemical composition of the foil body is, 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: 12.00~20.00%, Mo: 0.01 to 2.50% N: 0~0.100%, Ti: 0 to 0.80% Nb: 0 to 0.80%, and Zr: 0 to 0.80%; The balance is Fe and impurities.

[0027] The electrodes of the first configuration are: A ferritic stainless steel foil having any one of the first to third configurations; and an electrode mixture layer formed on the surface of the ferritic stainless steel foil.

[0028] The battery of the first configuration comprises: a first configuration of electrodes; and an electrolyte.

[0029] The battery in the second configuration is 1. A battery of a first configuration, comprising: The electrolyte is a sulfide-based solid electrolyte.

[0030] 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 "%" for elements means mass % unless otherwise specified.

[0031] [Composition 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 refers to a steel having a Cr content of 10.5% or more and a microstructure mainly composed of ferrite. In this specification, a microstructure mainly composed of ferrite means that the volume fraction of ferrite in the microstructure is 95% or more.

[0032] [Average half-width F 110 About In the ferritic stainless steel foil of this embodiment, the average half-width F of the peak of the {110} plane in the region from the surface of the foil body to the depth position of 0.38 μm to the depth position of 2.82 μm, obtained by grazing incidence X-ray diffraction, is 110 is 0.490° or more.

[0033] Here, the region from the surface of the foil body to a depth of 2.82 μm is defined as the surface layer. The average half-width F of the peak of the {110} plane in the region from a depth of 0.38 μm to a depth of 2.82 μm starting from the surface of the foil body is 110 is an index of dislocation density in the surface layer. As mentioned above, in order to suppress the formation of subgrain boundaries, which promote the progression of corrosion, it is effective to distribute a sufficient number of dislocations uniformly within the grains. If a sufficient number of dislocations are distributed uniformly within the grains in the surface layer, the dislocation density in the surface layer will be high. On the other hand, if the number of dislocations contained within the grains is insufficient, or if the dislocations multiply and become non-uniform, forming subgrain boundaries, the dislocation density will be low.

[0034] Average half-width F 110 If the angle is 0.490° or more, the dislocation density in the surface layer is sufficiently high. In this case, a sufficient number of dislocations are uniformly distributed within the grains in the surface layer. As a result, the progression of corrosion starting from the surface is suppressed, resulting in excellent corrosion resistance. Therefore, the average half-width F 110 is 0.490° or more.

[0035] Average half-width F 110 The lower limit of is preferably 0.493°, and more preferably 0.495°. Average half-width F 110 Considering normal industrial production, the average half-width F 110 The upper limit is, for example, 0.550°.

[0036] [Average half-width F 110 Measurement method] The average half-width F of the {110} plane in the region from the 0.38 μm depth position to the 2.82 μm depth position 110 is calculated in the following way:

[0037] A test piece is taken from the surface of the ferritic stainless steel foil body 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 foil body width. The observation surface of the test piece is measured using grazing incidence X-ray diffraction. For the measurement, for example, a SmartLab (trade name) manufactured by Rigaku Corporation can be used. The measurement uses CoKα radiation as the radiation source, a tube voltage of 40 kV, and a tube current of 135 mA. The X-ray beam is collimated using a mirror. A 5.0° Soller slit is installed on the entrance side, and a 5.0° Soller slit is installed on the receiving side. A parallel slit analyzer (PSA) is installed at 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 containing the rolling direction and the direction perpendicular to the surface of the foil body.

[0038] The measurement depth from the observation surface at each incidence angle in the grazing incidence X-ray diffraction method can be calculated from the X-ray penetration depth t that satisfies μt = 1, where μ is the linear absorption coefficient. The linear absorption coefficient μ is calculated using the mass absorption coefficient of 19.11Cr-1.77Mo-78.38Fe (mass%), which is equivalent to SUS444, and the density is 7.75g / cm. 3 Based on this conversion method, when the angle of incidence 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 angles of incidence set to 2.0°, 3.0°, 4.0°, 5.0°, 6.0°, 8.0°, 10.0°, 12.0°, and 15.0°. The peak of the {110} plane is identified from the diffraction profile obtained under each condition, and the half-width is calculated. The arithmetic mean value of the half-widths obtained under the nine conditions corresponding to measurement depths of 0.38 to 2.82 μm is taken as the average half-width F of the {110} plane from the 0.38 μm to 2.82 μm depth position. 110 In addition, F 110 is the value rounded to three decimal places.

[0039] [Regarding formula (1)] Preferably, in the ferritic stainless steel foil of this embodiment, the average lattice spacing D of the {110} plane in the region from a depth of 0.38 μm to a depth of 2.82 μm starting from the surface of the foil body is M (nm), and the average lattice spacing D of the {110} plane in the region deeper than 2.82 μm from the surface of the foil body. L (nm) satisfies formula (1). |D M -D L |≦0.0008 (1)

[0040] The average lattice spacing D of the {110} plane in the region from the surface of the foil body to the depth of 0.38 μm to the depth of 2.82 μm M (nm) represents the average lattice spacing of the {110} planes in the surface layer. The region deeper than 2.82 μm from the surface of the foil body is defined as the interior. When the foil body thickness is less than 9.20 μm, the average lattice spacing D of the {110} planes in the region deeper than 2.82 μm from the surface of the foil body is L (nm) is the average lattice spacing (nm) of the {110} planes from the 2.82 μm depth position starting from the surface of the foil body to the center depth position of the thickness. The center depth position of the thickness corresponds to the t / 2 (μm) depth position starting from the surface of the foil body, where t (μm) is the thickness of the foil body. Here, the average lattice spacing of the {110} planes is almost constant inside the foil body. Therefore, when the foil body thickness is 9.20 μm or more, the average lattice spacing D of the {110} planes in the region deeper than the 2.82 μm depth position starting from the surface of the foil body is L (nm) is the average lattice spacing (nm) of the {110} planes from a depth of 2.82 μm to a depth of 4.60 μm from the surface of the foil body. The average lattice spacing D of the {110} planes in the region deeper than 2.82 μm from the surface of the foil body L (nm) represents the average lattice spacing of the {110} planes inside the crystal. ΔD is defined as follows: ΔD=|D M -D L |

[0041] In the ferritic stainless steel foil of this embodiment, dislocations are introduced into the foil body due to external stress such as rolling, and at the same time, residual stress accumulates. The residual stress accumulated in the foil body causes localized plastic deformation within the foil body. Furthermore, if this plastic deformation occurs in the surface layer, defects may occur in the passive film. Corrosion preferentially progresses in areas where such localized plastic deformation occurs and in areas where the passive film is defective, similar to the sub-grain boundaries described above.

[0042] Average half-width F 110 The dislocation density, adjusted by the lattice spacing, is expressed by non-uniform lattice strain, while the residual stress is expressed by uniform lattice strain. Uniform lattice strain is an elastic strain of the crystal lattice that involves a change in lattice spacing. The magnitude of uniform lattice strain is proportional to the magnitude of residual stress. If the spacing of any lattice plane differs significantly between the surface and the interior, a large imbalance in the distribution of uniform lattice strain occurs within the foil body. In this case, the distribution of accumulated residual stress also becomes significantly uneven. A large imbalance in the distribution of residual stress creates areas where large residual stress is locally applied, making the above-mentioned plastic deformation more likely to occur. On the other hand, if the difference in lattice spacing between the surface and the interior is small, the occurrence of localized plastic deformation due to accumulated residual stress can be suppressed. As a result, the corrosion resistance of ferritic stainless steel foil can be further improved.

[0043] ΔD is an index that represents the absolute value of the difference in the average lattice spacing of the {110} plane between the surface and the interior. If ΔD is 0.0008 or less, the difference in lattice spacing between the surface and the interior is sufficiently small. In this case, the distribution of uniform lattice strain, an index of residual stress, is less biased, and the occurrence of localized plastic deformation is suppressed. As a result, even better corrosion resistance is obtained. Therefore, it is preferable that ΔD satisfies the formula (1).

[0044] The lower limit of ΔD is not particularly limited. Considering normal industrial production, the lower limit of ΔD is, for example, 0.0001. A more preferable upper limit of ΔD is 0.0007, and even more preferably 0.0006.

[0045] [Method for measuring the average lattice spacing] The average lattice spacing D of the {110} plane in the region from the 0.38 μm depth position to the 2.82 μm depth position M (nm), and the average lattice spacing D of the {110} plane in the region deeper than 2.82 μm L (nm) is calculated as follows:

[0046] A test piece is taken from the surface of the ferritic stainless steel foil body 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 foil body width. The observation surface of the test piece is measured using grazing incidence X-ray diffraction. For the measurement, for example, a SmartLab (trade name) manufactured by Rigaku Corporation can be used. The measurement uses CoKα radiation as the radiation source, a tube voltage of 40 kV, and a tube current of 135 mA. The X-ray beam is collimated using a mirror. A 5.0° Soller slit is installed on the entrance side, and a 5.0° Soller slit is installed on the receiving side. A parallel slit analyzer (PSA) is installed at 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 containing the rolling direction and the direction perpendicular to the surface of the foil body.

[0047] The measurement depth from the observation surface at each incidence angle in the grazing incidence X-ray diffraction method can be calculated from the X-ray penetration depth t that satisfies μt = 1, where μ is the linear absorption coefficient. The linear absorption coefficient μ is calculated using the mass absorption coefficient of 19.11Cr-1.77Mo-78.38Fe (mass%), which is equivalent to SUS444, and the density is 7.75g / cm. 3Based 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°. The peak of the {110} plane is identified from the diffraction profile obtained for each incident angle, and the lattice spacing D (nm) is calculated based on Bragg's law. The arithmetic mean value of the lattice spacing D for the nine incident angles in the range of 2.0° to 15.0° is used as the average lattice spacing D of the {110} plane in the region from a depth of 0.38 μm to a depth of 2.82 μm. M (nm).

[0048] Furthermore, when the thickness of the foil body is less than 9.20 μm, the incident angle α corresponding to the center depth position of the thickness is calculated based on the above-mentioned method for converting the measurement depth. MAX (°). The angle of incidence is 15.0° to α MAX The angle of incidence is changed arbitrarily within the range of 15.0° to α (°), and measurements are performed under a total of five conditions. The peak of the {110} plane is identified from the diffraction profile obtained for each incident angle, and the lattice spacing D (nm) is calculated based on Bragg's law. MAX The arithmetic mean value of the lattice spacing D under five conditions of the incident angle in the range of (°) is calculated as the average lattice spacing D of the {110} plane in the region of depth of 2.82 μm or more. L (nm).

[0049] On the other hand, when the foil thickness is 9.20 μm or more, the incident angle is arbitrarily changed within the range of 15.0° to 25.0°, and measurements are performed under a total of five conditions. Based on the above-mentioned method for converting measurement depth, the incident angle corresponding to the 4.60 μm depth position, which corresponds to the center depth position of the foil thickness for a 9.20 μm foil, is 25.0°. The peak of the {110} plane is identified from the diffraction profile obtained for each incident angle, and the lattice spacing D (nm) is calculated based on Bragg's law. The arithmetic mean value of the lattice spacing D for the five incident angles in the range of 15.0° to 25.0° is used as the average lattice spacing D of the {110} plane in the region of depth 2.82 μm or more. L (nm).

[0050] Obtained D M and D L ΔD is calculated based on the above. Note that ΔD is a value rounded off to the fourth decimal place.

[0051] [Chemical composition] In the ferritic stainless steel foil of this embodiment, the chemical composition of the foil body may be that of a known ferritic stainless steel.

[0052] 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).

[0053] 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).

[0054] The chemical composition of the foil body of the ferritic stainless steel foil of this embodiment may contain, for example, the following elements.

[0055] C: 0.001 to 0.030% Carbon (C) increases the strength of the ferritic stainless steel foil. If the C content is 0.001% or more, this effect can be sufficiently obtained. On the other hand, if 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, which in turn suppresses the embrittlement of the oxide film and improves the corrosion resistance of the ferritic stainless steel foil. Therefore, the preferred C content is 0.001 to 0.030%. A more preferable lower limit of the C content is 0.003%, and even more preferably 0.005%. The upper limit of the C content is more preferably 0.025%, and even more preferably 0.020%.

[0056] Si: 0.01 to 1.00% Silicon (Si) deoxidizes steel during the steelmaking process, and if the Si content is 0.01% or more, this effect can be 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%. The lower limit of the Si content is more preferably 0.03%, and even more preferably 0.05%. The upper limit of the Si content is more preferably 0.90%, and even more preferably 0.80%.

[0057] Mn: 0.01 to 1.00% Manganese (Mn) increases the strength of the ferritic stainless steel foil, and if the Mn content is 0.01% or more, this effect can be 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 preferable lower limit of the Mn content is 0.03%, and even more preferably 0.05%. A more preferable upper limit of the Mn content is 0.90%, and even more preferably 0.80%.

[0058] 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 better. However, excessively reducing the P content increases the production cost. Therefore, in consideration of normal industrial production, the lower limit of the P content is preferably more than 0%, more preferably 0.001%, and even more preferably 0.010%. A more preferable upper limit of the P content is 0.045%, and even more preferably 0.040%.

[0059] 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 S content is preferably as low as possible. However, excessively reducing the S content increases the production cost. Therefore, in consideration of normal industrial production, the lower limit of the S content is preferably more than 0%, more preferably 0.001%, and even more preferably 0.010%. The upper limit of the S content is more preferably 0.025%, and even more preferably 0.020%.

[0060] Ni: 0.01 to 0.50% Nickel (Ni) improves the corrosion resistance of the ferritic stainless steel foil, and if the Ni content is 0.01% or more, this effect can be 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%.

[0061] Cr: 12.00~20.00% Chromium (Cr) forms an oxide film and improves the corrosion resistance of the ferritic stainless steel foil. If the Cr content is 12.00% or more, this effect can be sufficiently obtained. On the other hand, if 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%. The lower limit of the Cr content is more preferably 12.50%, and even more preferably 13.00%. The upper limit of the Cr content is more preferably 19.00%, and even more preferably 18.00%.

[0062] Mo: 0.01 to 2.50% Molybdenum (Mo) enhances the strength and corrosion resistance of ferritic stainless steel foil, and if the Mo content is 0.01% or more, these effects can be sufficiently obtained. On the other hand, if 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 preferable lower limit of the Mo content is 0.03%, and even more preferably 0.05%. A more preferable upper limit of the Mo content is 2.40%, and even more preferably 2.30%.

[0063] N: 0 to 0.100% Nitrogen (N) may not be contained. On the other hand, if the N content is 0.100% or less, the strength of the ferritic stainless steel foil increases. Therefore, the preferred N content is 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%. The upper limit of the N content is more preferably 0.090%, and even more preferably 0.080%.

[0064] Ti: 0 to 0.80% Titanium (Ti) may not be contained. On the other hand, if the Ti content is 0.80% or less, it fixes C and suppresses the formation of Cr carbides, thereby suppressing the formation of a Cr-depleted layer. 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 preferable lower limit of the Ti content is more than 0%, even more preferably 0.01%, and even more preferably 0.03%. A more preferable upper limit of the Ti content is 0.70%, and even more preferably 0.60%.

[0065] Nb: 0 to 0.80% Niobium (Nb) may not 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 Nb content is preferably 0 to 0.80%. A more preferable lower limit of the Nb content is more than 0%, even more preferably 0.01%, and even more preferably 0.03%. The upper limit of the Nb content is more preferably 0.70%, and even more preferably 0.60%.

[0066] Zr: 0 to 0.80% Zirconium (Zr) may not 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 preferred Zr content is 0 to 0.80%. A more preferable lower limit of the Zr content is more than 0%, even 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%.

[0067] 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.

[0068] Plate 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.

[0069] [Uses of the ferritic stainless steel foil of this embodiment] The ferritic stainless steel foil of this 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 this embodiment can also be used for applications other than as a current collector in a secondary battery.

[0070] [Method for producing ferritic stainless steel foil according to the present embodiment] An example of a method for producing the ferritic stainless steel foil of this embodiment will be described. The method for producing the ferritic stainless steel foil described below is one example for producing the ferritic stainless steel foil of this embodiment. Therefore, the ferritic stainless steel foil having the above-mentioned configuration may be produced by a production method other than the production method described below. However, the production method described below is a preferred example of a method for producing the ferritic stainless steel foil of this embodiment.

[0071] An example of a method for producing the ferritic stainless steel foil of this embodiment includes the following steps. (Process 1) Material preparation process (Process 2) Intermediate cold rolling process (Process 3) Intermediate annealing process (Process 4) Final cold rolling process Each step will be described below.

[0072] [(Process 1) Material preparation process] In the material preparation step, a ferritic stainless steel sheet having a thickness of several hundred μm to several mm is prepared as a 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 process for preparing the material is not particularly limited.

[0073] When manufacturing a raw material, for example, it is manufactured by the following method. Molten steel having a desired chemical composition is manufactured. A slab is manufactured using the molten steel by continuous casting. The manufactured slab is hot worked and cold rolled to manufacture a steel plate having 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.

[0074] [(Process 2) Intermediate cold rolling process] In the intermediate cold rolling process, 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 process, for example, cold rolling may be performed using a continuous rolling mill equipped with multiple rolling stands, or cold rolling may be performed using a reversing rolling mill. There is no particular limitation on the cumulative reduction ratio in the intermediate cold rolling process.

[0075] [(Process 3) Intermediate annealing process] In the intermediate annealing step, bright annealing is performed on the intermediate steel sheet after the intermediate cold rolling step. Bright annealing is an annealing treatment performed in an extremely low oxygen atmosphere. The surface of the intermediate steel sheet that has been subjected to bright annealing is hardly oxidized, and the surface gloss can be maintained. The extremely low oxygen atmosphere in bright annealing is preferably a mixed gas atmosphere of H2 gas and N2 gas. The N2 fraction in the atmospheric gas is, for example, 35 to 65% by volume.

[0076] In the bright annealing performed in the intermediate annealing process, 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 maintained at a predetermined temperature. Here, the temperature in the heating chamber is the heating temperature T (°C), and the time it takes for the intermediate steel sheet to pass through the heating chamber is 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 air cooling, for example.

[0077] 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, followed by a second intermediate cold rolling step and a second intermediate annealing step.

[0078] The intermediate annealing step satisfies the following conditions: When the intermediate annealing step is performed multiple times, it is sufficient that the following conditions are satisfied in the intermediate annealing step that is performed last. (Condition 1) The heating temperature T (° C.) and the holding time t (seconds) satisfy the formula (A). (T-800)×(log 10 t+25)≦6544 (A) Condition 1 will be explained below.

[0079] [Regarding formula (A)] FA is defined by the following formula: FA = (T-800) × (log 10 t+25) In the intermediate annealing step, the higher the heating temperature T or the longer the holding time t, the more the dislocations contained in the foil body are reduced by pair annihilation. If FA exceeds 6544, the dislocations contained in the foil body are excessively reduced. In this case, even if the condition 2 described later is satisfied in the final cold rolling step, a sufficient amount of dislocations cannot be introduced. Therefore, the average half-width F 110 is less than 0.490°.

[0080] On the other hand, if the FA is 6544 or less, the average half-width F of the ferritic stainless steel foil to be manufactured will be 1.0, provided that the final cold rolling process satisfies the condition 2 described below. 110 is 0.490° or more. Therefore, FA should satisfy formula (A). The lower limit of FA is not particularly limited. Taking into consideration normal industrial production, the lower limit of FA is, for example, 1,000.

[0081] In the intermediate annealing step, the following conditions are preferably satisfied: When the intermediate annealing step is performed a plurality of times, it is sufficient that the following conditions are satisfied in the intermediate annealing step that is performed last. (Preferable condition 1) The average cooling rate CR from the heating temperature T (°C) to 400°C is 195°C / sec or less. The preferred condition 1 will be explained below.

[0082] [About the average cooling rate CR] In the intermediate annealing process, residual stress imparted in the intermediate cold rolling process is also released by heat. However, if the average cooling rate CR from the heating temperature T (°C) to 400°C is fast, there will be a difference in the degree of release of residual stress between the surface and the interior of the intermediate steel sheet. If the average cooling rate CR is 195°C / s or less, the bias in the distribution of residual stress that occurs in the intermediate annealing process can be reduced. In this case, assuming that the final cold rolling process satisfies the preferred condition 2 described below, the ΔD of the ferritic stainless steel foil produced will satisfy formula (1). Therefore, it is preferable that the average cooling rate CR from the heating temperature T (°C) to 400°C be 195°C / s or less. There is no particular limitation on the lower limit of the average cooling rate CR. In consideration of normal industrial production, the lower limit of the average cooling rate CR is, for example, 20°C / sec.

[0083] [(Process 4) Final cold rolling process] 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. A well-known cold rolling mill may be used in the final cold rolling step. 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.

[0084] The final cold rolling process satisfies the following conditions: (Condition 2) Reduction rate R in the final pass L and the reduction rate R in the pass immediately before the final pass. L-1 and satisfy the formula (B). R L / R L-1 ≧0.15 (B) Condition 2 will be explained below.

[0085] [Regarding formula (B)] FB is defined by the following formula: FB=R L / R L-1 Here, "pass" means the operation of the material passing through one rolling stand once. In the final cold rolling process, cold rolling consisting of multiple passes is carried out. The "reduction ratio R L " means the reduction rate in the last pass (final pass) among multiple passes performed in the final cold rolling process. "The reduction rate R in the pass immediately before the final pass L-1 " means the reduction rate in the pass immediately before the final pass among the multiple passes performed in the final cold rolling process.

[0086] In the final cold rolling process, the reduction rate R L-1 Reduction rate R in the final pass LThe larger FB is, the more uniform the distribution of dislocations introduced into the foil body will be. If FB is 0.15 or more, the distribution of dislocations introduced into the surface layer will be sufficiently uniform. In this case, the dislocation density in the surface layer will also be sufficiently large. As a result, assuming that the intermediate annealing process satisfies condition 1, the average half-width F of the ferritic stainless steel foil manufactured will be 110 is 0.490° or more. Therefore, FB must be 0.15 or more. The upper limit of FB is not particularly limited. Taking into consideration normal industrial production, the upper limit of FB is, for example, 0.60.

[0087] In the final cold rolling step, the following conditions are preferably satisfied: (Preferred condition 2) Maximum rolling reduction rate R in one pass MAX is less than 30%. The second preferable condition will now be described.

[0088] [Maximum rolling reduction in one pass R MAX About Maximum rolling reduction in one pass R MAX " refers to the reduction rate in the pass with the largest reduction rate in the final cold rolling process. The residual stress imparted to the intermediate steel plate in a pass with a too large reduction rate has a large imbalance in distribution between the surface and the interior. The maximum reduction rate R in one pass MAX When the maximum rolling reduction R in one pass is 30% or less, it means that there are no passes with a rolling reduction exceeding 30%. In this case, the distribution of residual stress accumulated in the foil body is sufficiently small. As a result, assuming that the intermediate annealing process satisfies the preferred condition 1, the ΔD of the manufactured ferritic stainless steel foil satisfies the formula (1). Therefore, the maximum rolling reduction R in one pass is MAX is preferably 30% or less. Maximum reduction rate in one pass R MAX There is no particular lower limit for the maximum rolling reduction R in one pass, considering normal industrial production. MAX The lower limit is, for example, 5%.

[0089] The ferritic stainless steel foil of this embodiment is manufactured by the above-described manufacturing method.

[0090] [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.

[0091] [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. 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.

[0092] [Active material] In the electrode of this embodiment, the active material contained in the electrode mixture layer is not particularly limited, and well-known active materials can be used. When the electrode is a positive electrode, the positive electrode active material may be, for example, LiCoO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 The negative electrode active material may be, for example, a carbon-based material such as graphite, an alloy material such as CuSn alloy and NiTiSi alloy, a Si-based material such as Si and SiO, or Li4Ti5O 12 It may also be an oxide-based material represented by the following.

[0093] [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, for example, a rubbery polymer such as styrene-butadiene rubber or isoprene rubber, a synthetic resin such as polyethylene, polyimide, polyacrylic acid, or polyamide, a styrene-butadiene-styrene block copolymer or its hydrogenated product, a thermoplastic elastomer such as styrene-ethylene-butadiene, styrene copolymer, styrene-isoprene, or styrene block copolymer or their hydrogenated products, a soft resinous polymer such as syndiotactic 1,2-polybutadiene, ethylene-vinyl acetate copolymer, or copolymer of ethylene with an α-olefin having 3 to 12 carbon atoms, or a fluorinated polymer such as polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, polypentafluoropropylene, or polyhexafluoropropylene.

[0094] [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 can be used. The conductive additive may be, for example, acetylene black, carbon black, or ketjen black.

[0095] [Electrode manufacturing method] The method for producing the electrode of this embodiment is not particularly limited. The electrode of this embodiment is produced by a well-known method using the ferritic stainless steel foil of this embodiment as a current collector. The method for producing the electrode of this embodiment includes, for example, an electrode slurry preparation step and an electrode mixture layer formation step.

[0096] [Electrode slurry preparation process] 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. In other words, the electrode slurry preparation step may be performed by a known method.

[0097] [Electrode mixture layer formation process] 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.

[0098] The electrode of this embodiment can be manufactured by the above steps.

[0099] [battery] The battery of this embodiment includes the electrode of this embodiment and an electrolyte. The battery of this embodiment may have any known configuration other than the electrode of this embodiment, and is 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.

[0100] [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.

[0101] 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. Examples of sulfide-based solid electrolytes include Li3PS4 and Li7P3S 11 It may be an LPS system represented by Li6PS5Cl x Br (1-x) (0≦x≦1) may be an argyrodite type, 10 GeP2S 12 and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The thiolicon represented by the following may also be used.

[0102] [Battery manufacturing method] The method for manufacturing the battery of the present embodiment is not particularly limited. For example, the battery of the present embodiment is manufactured 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. [Example]

[0103] 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.

[0104] 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.

[0105] [Table 1]

[0106] 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.

[0107] The intermediate steel sheets after the intermediate cold rolling process were subjected to a single intermediate annealing process. Specifically, the intermediate steel sheets of each test number were bright annealed in a mixed gas atmosphere of 35 to 65 volume % N2 gas and the remainder H2 gas. In the bright annealing, the intermediate steel sheets were held at a heating temperature T (°C) for a holding time t (seconds), and then cooled to 400°C at an average cooling rate CR (°C / second). They were then rapidly cooled to room temperature by air cooling. Table 2 shows the heating temperature T (°C), holding time t (seconds), and average cooling rate CR (°C / second) from the heating temperature T (°C) to 400°C for each test number.

[0108] [Table 2]

[0109] The intermediate steel sheets after the intermediate annealing process were subjected to a final cold rolling process. In the final cold rolling process, the intermediate steel sheets of each test number were subjected to cold rolling using a reverse rolling mill to produce ferritic stainless steel foils having a foil body with a thickness of 10 μm. The FB and the maximum rolling reduction R in one pass for each test number were MAX (%) are shown in Table 2.

[0110] By the above manufacturing process, ferritic stainless steel foils with each test number were manufactured.

[0111] [About the evaluation test] The following evaluation tests were carried out on the produced ferritic stainless steel foils with each test number. (Test 1) Average half-width measurement test (Test 2) Average lattice spacing measurement test (Test 3) Corrosion resistance evaluation test Each test will be explained below.

[0112] [(Test 1) Average half-width measurement test] The above-mentioned [average half-width F 110 Based on the method described in [Measurement method for the average half-value F of the {110} plane in the region 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], 110 The average half-width F 110 is shown in Table 3.

[0113] [Table 3]

[0114] [(Test 2) Average lattice spacing measurement test] Based on the method described in the above [Method for measuring average lattice spacing], the average lattice spacing D of the {110} plane in the region 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. M (nm), and the average lattice spacing D of the {110} plane in the region deeper than 2.82 μm L (nm) was measured. M and D L ΔD was calculated based on the above. ΔD for each test number is shown in Table 3.

[0115] [(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 ferritic stainless steel foil. One surface of the test piece was used as the evaluation surface. The developed area ratio Sdr, as specified in ISO25178-2:2012, was measured on the evaluation surface of the test piece. The developed area ratio Sdr is an index that represents the rate of increase in the surface area of ​​the measured surface compared to a flat surface. Since the corrosion reaction begins on the surface of the foil itself, the greater the developed area ratio Sdr of the test piece, the faster the corrosion progresses.

[0116] The developed area ratio Sdr of the evaluation surface of the test specimen was measured using a laser microscope. The laser microscope used was a Keyence VK-X100. A measurement area of ​​280 μm × 200 μm was measured at a magnification of 2000x. Specifically, four locations within the measurement area were measured with a 145 μm × 109 μm field of view to measure the entire area, and a surface image was obtained. The four surface images were linked using the accompanying image linking software to obtain a surface image of the 280 μm × 200 μm measurement area. A reference plane was set by cutting 0.3% of the area from the low-brightness side from the surface shape profile obtained by analyzing the surface image of the measurement area, and a three-dimensional image was generated. Filtering was performed using a high-pass filter with a cutoff wavelength of 50 μm. A Gaussian filter was used for filtering. The developed area ratio Sdr, as defined in ISO25178-2:2012, was calculated in a 200 μm × 150 μm region of the obtained three-dimensional image.

[0117] Using the test specimens with the measured developed area ratio (Sdr), evaluation cells simulating sulfide-based all-solid-state batteries were fabricated. Specifically, 0.12 g of 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. β-Li3PS4 was used as the sulfide-based solid electrolyte. The resulting pellet was placed on the evaluation surface of each test specimen. Furthermore, a cylindrical Li foil with 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, which was sealed from the outside air, and then bolted to a pressure of 5 MPa. The process from preparing the sulfide-based solid electrolyte pellet to sealing the evaluation cell was carried out in a glove box with an Ar atmosphere. The evaluation cells for each test specimen were fabricated using the above process.

[0118] Cyclic voltammetry (CV) measurements were carried out 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 (V) to 3.0V, then to 0.005V, and again to the open circuit voltage V OC (V), and the current density (μA / cm 2 The open-circuit voltage V OC was 2.0 to 2.5 V for the evaluation cells of all test numbers.

[0119] Based on the measurement results, the open circuit voltage V OC The current density (μA / cm) flowing during the sweep from (V) to 3.0 V 2 ) was integrated over the time (seconds) required for the sweep. Furthermore, this integrated value was divided by the developed area ratio Sdr to determine a value in order to eliminate the influence of minute irregularities on the evaluation surface of the test piece. The obtained value was used as the integrated current value C (μC / cm 2 ) and was used as an index to represent the progress of the corrosion reaction on the test piece. 2 ) is the open circuit voltage V OC The time elapsed from the start of the sweep from (V) to 3.0V is defined as the test time t (seconds), and the time it takes to reach 3.0V 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 using the following formula.

number

[0120] Accumulated current value C (μC / cm 2 ) are shown in Table 3. When the integrated current value C is 800 μC / cm 2 Super~1000μC / cm 2 When the integrated current value C was 800 μC / cm, it was judged that excellent corrosion resistance was obtained.2 When the integrated current value C was 1000 μC / cm or less, it was judged that even better corrosion resistance was obtained. 2 When the value exceeded this, it was determined that excellent corrosion resistance was not obtained.

[0121] [Evaluation results] Referring to Tables 1 to 3, for the ferritic stainless steel foils of test numbers 1 to 9, the average half-width F 110 The angle was 0.490° or more, which resulted in excellent corrosion resistance.

[0122] Furthermore, in the ferritic stainless steel foils of test numbers 1 to 6, ΔD satisfied formula (1), and therefore even better corrosion resistance was obtained.

[0123] On the other hand, in test number 10, the FA in the intermediate annealing process was too high. 110 As a result, excellent corrosion resistance was not obtained.

[0124] In test number 11, the F value in the final cold rolling process was too low. 110 As a result, excellent corrosion resistance was not obtained.

[0125] 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, The average half-width F of the peak of the {110} plane in the region from the surface of the foil body to a depth of 0.38 μm to a depth of 2.82 μm, obtained by grazing incidence X-ray diffraction. １１０ is 0.490° or more, Ferritic stainless steel foil.

2. The ferritic stainless steel foil according to claim 1, further comprising: The average lattice spacing D of the {110} plane in the region from a depth of 0.38 μm to a depth of 2.82 μm starting from the surface of the foil body Ｍ (nm), and the average lattice spacing D of the {110} plane in the region at a depth of 2.82 μm or more from the surface of the foil body. Ｌ (nm) satisfies formula (1), Ferritic stainless steel foil. |D Ｍ -D Ｌ |≦0.0008 (1)

3. The ferritic stainless steel foil according to claim 1, The chemical composition of the foil body is, 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 to 0.80%, Nb: 0 to 0.80%, and Zr: 0 to 0.80%; The balance consists of Fe and impurities. Ferritic stainless steel foil.

4. The ferritic stainless steel foil according to claim 2, The chemical composition of the foil body is, 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 to 0.80%, Nb: 0 to 0.80%, and Zr: 0 to 0.80%; The balance consists of Fe and impurities. Ferritic stainless steel foil.

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

6. The electrode according to claim 5; an electrolyte; battery.

7. 7. The battery of claim 6, The electrolyte is a sulfide-based solid electrolyte. battery.

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