Electrolytic foil and battery current collectors

Abstract

To provide an electrolytic foil and a battery current collector that can suppress breakage or tearing during manufacturing, which is a concern as the battery is made thinner, and that has sufficient strength to withstand repeated charging and discharging in a secondary battery.SOLUTION: An electrolytic foil includes a Ni-Fe alloy layer, has a thickness of 1.5 μm to 10 μm, and has a first surface and a second surface, and in each of the first surface and the second surface, a value obtained by dividing a three-dimensional surface texture parameter Sv by the thickness is 0.5 or less, and there is also provided a current collector for a battery.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrolytic foil that is particularly suitable for use as a current collector for secondary batteries and the like, and to a current collector for batteries. [Background technology]

[0002] Thinning the current collector is an effective way to increase the capacity of conventional batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries. However, thinning the current collector also reduces its strength, raising concerns about deformation and breakage of the current collector.

[0003] In response to this, a technique has been disclosed in which a thin electrolytic foil is used as a current collector. For example, Patent Document 1 proposes a technique for forming a hard nickel plating layer on the surface of an electrolytic foil by electroplating at least one surface of the electrolytic foil made of a metal material with low lithium compound forming ability using a plating bath containing a nickel salt and an ammonium salt.

[0004] Furthermore, for example, Patent Document 2 discloses a technique of providing a negative electrode current collector that suppresses the generation of copper sulfides and has excellent electrical conductivity by applying nickel plating with little residual stress to a copper foil used as a negative electrode current collector. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-197205 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-9526 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although the techniques described in the above-mentioned patent documents improve the strength of the current collector to a certain extent, it can be said that there is still room for improvement in at least the following points. That is, in recent years, demands for battery performance have become even higher, and since the amount of active material can be increased by making the current collector itself thinner, it is desired that the current collector have sufficient strength to prevent tearing and ripping during manufacturing and handling due to the thinning of the current collector. Furthermore, for example, there is a demand for negative electrode current collectors to have high strength that can accommodate the characteristics of new active materials such as silicon-based and tin-based negative electrode materials that can replace carbon. Furthermore, there is a demand for a material that, when used as a current collector in a secondary battery, can prevent wrinkles, tears, and ripping even after repeated charge and discharge, and can also prevent the active material applied to the surface of the current collector from peeling off. Furthermore, thin, high-strength electrolytic foils are desired for applications other than current collectors, such as heat dissipation materials and electromagnetic wave shielding materials.

[0007] However, the above-mentioned Patent Documents 1 and 2 only disclose the technical idea of ​​forming layers using a nickel coating, and do not disclose any specific structure for realizing high levels of handleability during battery assembly or strength during repeated charge and discharge in a secondary battery.

[0008] The present invention has been made in view of solving the above problems, and has an object to provide an electrolytic foil and a current collector for a battery that can suppress breakage or tearing during manufacturing, which is a concern as the foil is made thinner, and that has sufficient strength to withstand repeated charge and discharge in a secondary battery. [Means for solving the problem]

[0009] That is, the electrolytic foil of the present invention is an electrolytic foil containing a Ni-Fe alloy layer, characterized in that (1) it has a thickness of 1.5 μm to 10 μm, has a first side and a second side, and on the first side and the second side, the value obtained by dividing the three-dimensional surface texture parameter Sv by the thickness is 0.5 or less. In the electrolytic foil of the above (1), (2) the thickness is preferably 2 μm to 8 μm. In addition, in the electrolytic foil of (1) or (2) above, (3) it is preferable that at least one metal layer made of a metal species different from that of the Ni-Fe alloy layer is laminated on the Ni-Fe alloy layer. In the electrolytic foil of the above (3), (4) the thickness of the Ni—Fe alloy layer is preferably 2.0 μm to 9.9 μm. In the electrolytic foil of the above (3) or (4), (5) the total thickness of the metal layers is preferably 0.1 μm to 8.0 μm. In the electrolytic foil of any one of the above items (3) to (5), (6) it is preferable that the thickness ratio of the Ni—Fe alloy layer in the electrolytic foil is 18 to 95%. In the electrolytic foil according to any one of the above items (1) to (6), (7) the tensile strength is preferably more than 720 MPa. The current collector for a battery in the present invention is preferably (8) made of the electrolytic foil described in any one of (1) to (7) above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an electrolytic foil that can be prevented from tearing or breaking during handling even when the thickness is reduced, and also to provide an electrolytic foil and a current collector for a battery that have sufficient strength to withstand repeated charge and discharge when used as a current collector for a secondary battery. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing a cross section of an alloy electrolytic foil according to an embodiment of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing a test piece produced using the alloy electrolytic foil of the present embodiment. [Figure 3] FIG. 1 is a schematic diagram showing a laminated electrolytic foil according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] ≪Alloy electrolytic foil 10≫ Hereinafter, an embodiment for carrying out the electrolytic foil of the present invention will be described. 1 is a schematic diagram showing an alloy electrolytic foil according to one embodiment of the present invention. The alloy electrolytic foil of this embodiment can be used as a current collector for a battery negative electrode, as well as a current collector for a battery positive electrode. The type of battery may be a secondary battery or a primary battery.

[0013] As shown in Fig. 1, the alloy electrolytic foil 10 of this embodiment has a first surface 10a and a second surface 10b. The alloy electrolytic foil 10 of this embodiment is made of a Ni-Fe alloy. That is, the electrolytic foil of the present invention is characterized by containing a Ni-Fe alloy layer, but the alloy electrolytic foil 10 of this embodiment can be said to be entirely made of a Ni-Fe alloy layer. Furthermore, the electrolytic alloy foil 10 of this embodiment is formed by electrolytic plating. Specifically, the electrolytic alloy foil 10 can be formed using a known Ni—Fe alloy plating bath. The alloy electrolytic foil 10 of this embodiment has a first side and a second side. In the following description, the side (substrate side) that was in contact with the support (substrate) that supports the electrolytic foil during the production of the alloy electrolytic foil 10 will be referred to as the first side 10a, and the other side (electrolytic side) will be referred to as the second side 10b.

[0014] In this embodiment, the ratio (wt %) of Ni to Fe in the Ni-Fe alloy of the alloy electrolytic foil 10 is preferably 95:5 to 40:60. In this case, in order to improve the overall strength of the alloy electrolytic foil 10, the ratio of Ni:Fe is preferably 95:5 to 40:60, and more preferably 90:10 to 70:30. On the other hand, when cost is important, the Ni:Fe ratio is preferably 80:20 to 50:50, and more preferably 70:30 to 53:47.

[0015] In this embodiment, the Ni-Fe alloy plating layer may be a Ni-Fe alloy plating layer to which no brightener is added (for convenience, also referred to as a "matt Ni-Fe alloy plating layer"), or a bright Ni-Fe alloy plating layer to which a brightener (including a semi-bright brightener) is added. The above-mentioned "glossy" and "matt" are based on visual evaluation of appearance, and it is difficult to categorize them with precise numerical values. Furthermore, the degree of gloss can also change depending on other parameters such as the bath temperature, which will be described later. Therefore, the terms "glossy" and "matt" used in this embodiment are defined solely based on the presence or absence of a glossing agent.

[0016] The alloy electrolytic foil 10 of this embodiment has a first surface 10a and a second surface 10b, and is characterized in that the value obtained by dividing the three-dimensional surface texture parameter Sv by the thickness of the alloy electrolytic foil 10 is 0.5 or less on both the first surface 10a and the second surface 10b. The reason for this is as follows.

[0017] That is, in accordance with the trend toward higher capacity secondary batteries, there is a demand for thinner electrolytic foils to be used as current collectors. To meet this demand, the alloy electrolytic foil 10 of this embodiment is manufactured as a high-strength alloy foil by electrolytic plating.

[0018] The inventors of the present invention have conducted extensive research to produce an electrolytic foil that can suppress tearing and ripping during manufacturing and handling (including during battery assembly), which is a concern as the foil becomes thinner, and that can suppress wrinkling and tearing even when an active material that undergoes large volume changes during repeated charge and discharge in a secondary battery is used. As a result, they found that when Ni-Fe alloy electrolytic foil is used as a high-strength electrolytic foil, the above-mentioned effects can be obtained by controlling the surface shape, and they arrived at the present invention.

[0019] Specifically, the parameter used to represent the surface shape of the Ni-Fe alloy electrolytic foil of this embodiment is the "maximum valley depth" (three-dimensional surface texture parameter Sv) of the surface roughness defined in ISO 25178-2:2012. In other words, the tensile strength of a metal foil is theoretically a value that is not affected by its thickness. However, the inventors have found through their research that in practice, when the thickness of a Ni-Fe alloy electrolytic foil is reduced (specifically, to 10 μm or less), the tensile strength may be significantly lower than the theoretical value. The inventors believe that one of the reasons for this is that the metal foil is more susceptible to the influence of surface irregularities, etc.

[0020] In particular, we discovered that the occurrence of significantly deep recesses or valleys may prevent the Ni-Fe alloy electrolytic foil from achieving its intended tensile strength. This is thought to be because, in the case of a Ni-Fe alloy, if the electrolytic foil has a location in the thickness direction where the distance t between the first surface 10a and the second surface 10b is particularly short, as shown in Figure 1(b), stress concentration at that location causes cracks to occur. In the case of Ni-Fe, which has high hardness, cracks originating from that location propagate throughout the entire alloy layer. As a result, the foil is more prone to tearing and ripping than other metals, resulting in a lower than intended strength. We also discovered that this phenomenon is particularly likely to occur in electrolytic foils of 8.0 μm or less. It was confirmed that the strength of Ni foils does not change significantly even when the foil is thinned.

[0021] As a result of repeated investigations based on the above assumption, it was found that by setting the Sv (maximum valley depth) on the surface of the Ni-Fe alloy electrolytic foil of this embodiment to a predetermined value in relation to the thickness of the electrolytic foil, it is possible to obtain an alloy electrolytic foil having a high tensile strength that has not been achieved before.

[0022] The alloy electrolytic foil 10 of this embodiment based on the above-mentioned purpose is characterized in that the value of "Sv (maximum valley depth) [μm] / thickness of alloy electrolytic foil 10 [μm]" on its surfaces (first surface 10a and second surface 10b) is 0.5 or less. If the value of Sv (maximum valley depth) / thickness of the alloy electrolytic foil 10 exceeds 0.5, it may be impossible to obtain the required value for the tensile strength of the alloy electrolytic foil, which is undesirable. From the viewpoint of more stabilizing the strength (easiness to maintain the original strength), the value is preferably 0.48 or less, and more preferably 0.46 or less.

[0023] The three-dimensional surface texture parameter Sv of the electrolytic alloy foil 10 of this embodiment can be determined by a known non-contact three-dimensional surface roughness measuring device or the like. In the alloy electrolytic foil 10 of this embodiment, it is preferable that the values ​​of Sku (peakiness of the histogram of the height distribution), Sv [μm] (maximum valley depth), Sz [μm] (maximum height), and Sa [μm] (arithmetic mean height) on the first surface 10a and the second surface 10b are as follows: Sku: Less than 7.2, preferably 6.0 or less Sv: Less than 2.2, preferably 2.0 or less Sz: Less than 4.7, preferably 4.0 or less Sa: Less than 0.3, preferably 0.25 or less In order to control the three-dimensional surface texture parameters Sku, Sv, Sz, and Sa of the alloy electrolytic foil 10 of this embodiment within the above-mentioned ranges, it is possible to employ methods such as controlling the plating conditions as described below, polishing the surface of the support, and smoothing the surface of the obtained alloy electrolytic foil by etching or electrolytic polishing.

[0024] Next, the thickness of the electrolytic alloy foil 10 in this embodiment will be described. The thickness of the alloy electrolytic foil 10 in this embodiment is characterized by being 1.5 μm to 10 μm. A thickness of 2.0 μm to 8.0 μm is more preferable, and a thickness of 2.5 μm to 6.0 μm is particularly preferable. A thickness exceeding 10 μm does not fit the design concept of achieving high capacity through thinning, and furthermore, the cost advantage over known rolled foils is diminished. On the other hand, a thickness less than 1.5 μm not only makes it difficult to provide sufficient strength against the effects of charge and discharge, but also increases the likelihood of tearing, ripping, wrinkling, etc. during battery manufacturing and handling.

[0025] In this embodiment, the "thickness of the alloy electrolytic foil 10" is preferably measured by a gravimetric method. Alternatively, thickness measurement using a micrometer is also applicable. However, if the alloy electrolytic foil has an Sz of more than 4.0 μm, the thickness measured using a micrometer is likely to differ due to the influence of surface irregularities, so the gravimetric method is preferred. When a Ni layer is laminated in laminated electrolytic foil A described later, it is difficult to determine the density and film thickness by the gravimetric method, so it is preferable to measure the thickness with a micrometer.

[0026] The tensile strength of the Ni-Fe alloy electrolytic foil 10 of this embodiment is preferably a value exceeding 720 MPa. If the tensile strength of the Ni-Fe alloy electrolytic foil 10 is 720 MPa or less, the foil may tear or break during battery production, which is undesirable because it reduces handleability. Furthermore, when used as a current collector for a secondary battery, it may not be able to keep up with volume expansion due to repeated charge and discharge, which may cause breakage. In this embodiment, even if the thickness of the alloy electrolytic foil 10 is 4 μm or less, a tensile strength of 1000 MPa or more can be achieved.

[0027] In this embodiment, the tensile strength of the alloy electrolytic foil can be measured, for example, as follows: Using an SD-type lever-type specimen cutter (model: SDL-200) manufactured by Dumbbell Co., Ltd. and a cutter (model: SDK-400) conforming to JIS K6251, a metal piece in the dumbbell No. 4 shape of JIS K6251 shown in Fig. 2 is punched out. This test piece can then be subjected to a tensile test in accordance with the tensile test method conforming to JIS Z 2241, the JIS standard for metal test pieces.

[0028] The size of the crystal grains (crystal grain size) in the Ni-Fe alloy electrolytic foil 10 of this embodiment is not particularly limited as long as the value of "Sv (maximum valley depth) [μm] / thickness of the alloy electrolytic foil 10 [μm]" is 0.5 or less, but is preferably 0.01 μm to 1 μm, for example. The crystal grain size can be determined by a cutting method based on cross-sectional observation or by EBSD crystal orientation analysis.

[0029] In manufacturing the Ni-Fe alloy electrolytic foil 10 of this embodiment, a Ni-Fe alloy plating is formed on a support made of a titanium plate, a stainless steel plate, or the like, and then the plating layer is peeled off from the support by a known method to obtain the Ni-Fe alloy electrolytic foil 10. The specific material of the support is not limited to the titanium plate or stainless steel plate described above, and other known metal materials can be used as long as they do not deviate from the spirit of the present invention.

[0030] The conditions for the Ni-Fe alloy plating bath are as follows: [Ni-Fe alloy plating conditions] ·Bath composition Nickel sulfate hexahydrate: 150~250g / L Iron sulfate heptahydrate: 5~100g / L Nickel chloride hexahydrate: 20-50g / L Boric acid: 20-50g / L Sodium citrate (or trisodium citrate) 1-15g / L Sodium saccharin: 1 to 10 g / L ·Temperature: 25~70℃ pH: 2-4 Agitation: Air agitation or jet agitation ·Current density: 5~40A / dm 2

[0031] Regarding the bath temperature, if it is less than 25°C, the roughness of the foil will be significantly increased, which is not desirable. It is also undesirable because it may prevent the layer from being deposited. On the other hand, if it exceeds 70°C, the roughness of the foil will also increase, which is also undesirable. It is also undesirable because the tensile strength of the resulting layer cannot be ensured. A pH of less than 2 is undesirable because it significantly increases the roughness of the foil and reduces the plating deposition efficiency. On the other hand, a pH of more than 4 is undesirable because it increases the roughness of the foil and may also result in sludge being entrained in the resulting layer. Regarding current density, 5A / dm 2 If the current is less than 40A / dm, the roughness of the foil will increase, which is not desirable. In addition, there is a risk of a decrease in production efficiency, which is also not desirable. 2 If the temperature exceeds this range, plating fading may occur, which is not preferable. Also, an appropriate amount of a pitting inhibitor may be added.

[0032] The method for producing the Ni—Fe alloy electrolytic foil 10 of this embodiment generally includes the following steps. First, the support on which the plating layer is to be formed is subjected to pretreatments such as polishing, wiping, rinsing with water, degreasing, and pickling, and then the support is immersed in the plating bath exemplified above to form a Ni-Fe alloy plating layer on the support. The formed plating layer is dried and then peeled off to obtain Ni-Fe alloy electrolytic foil 10.

[0033] In the above process, polishing, which is one of the pretreatments performed on the support, will be described. When manufacturing the Ni-Fe alloy electrolytic foil 10 of this embodiment, the surface shape of the support on which the plating layer is formed is largely transferred to the plating layer, becoming one side (base surface) of the alloy electrolytic foil 10. Furthermore, the thinner the alloy electrolytic foil 10, the more likely it is that the shape of the surface (electrolytic surface) of the alloy electrolytic foil 10 will reflect the surface shape of the support.

[0034] Therefore, in order to set the value of the three-dimensional surface texture parameter Sv of the Ni—Fe alloy electrolytic foil 10 within the above-mentioned range, it is preferable to control the surface shape of the support, for example, the surface roughness Sa. Specifically, it is preferable that the surface roughness Sa of the support is 0.14 μm or less.

[0035] The surface roughness Sa of the support can be set to the above value, for example, by polishing the support surface using known means. The polishing direction is not particularly limited, and the support may be polished in a specific direction such as the width direction or length direction, or may be polished randomly.

[0036] Before or after peeling the Ni—Fe alloy electrolytic foil 10 from the support, the outermost surface of the Ni—Fe alloy electrolytic foil 10 may be subjected to a roughening treatment or anti-rust treatment within the scope of the claims of the present invention, or may be subjected to a known treatment for imparting conductivity, such as a carbon coating.

[0037] In this embodiment, the methods for controlling the surface roughness (three-dimensional surface texture) of the Ni-Fe alloy electrolytic foil 10 have been described above as controlling the plating conditions and polishing the support surface, but the methods are not limited thereto. For example, the desired three-dimensional surface texture can also be obtained by smoothing the surface of the Ni-Fe alloy electrolytic foil 10 itself by etching or electropolishing.

[0038] In this embodiment, an example of producing a Ni-Fe alloy using a continuous production method (e.g., a drum method or a roll-to-roll method) using a support body has been described, but the present invention is not limited to this mode, and production using a batch method using, for example, a cut plate is also possible.

[0039] Furthermore, the alloy electrolytic foil of this embodiment, having the above-described configuration, exhibits the following effects. Specifically, during the process of manufacturing the metal foil as a current collector, the drying temperature may reach 200°C or higher (400°C or lower). The Ni-Fe alloy electrolytic foil of this embodiment maintains a certain strength even within the above heating temperature range, thereby preventing a decrease in strength due to heating during manufacturing and handling (such as during battery assembly or use as a current collector).

[0040] <Laminated electrolytic foil A> Next, laminated electrolytic foil A will be described as another embodiment of the present invention. As shown in Fig. 3, the laminated electrolytic foil A in this embodiment has a Ni-Fe alloy electrolytic layer 10' and at least one metal layer 20 made of a metal species different from that of the Ni-Fe alloy electrolytic layer 10'. That is, in this embodiment, it is preferable that the metal layer 20 is laminated on one or both sides of the Ni-Fe alloy electrolytic layer 10'. Examples of the metal layer 20 include Cu, Ni, Co, and Fe. These metals do not react with Li at the operating potential of the negative electrode of a lithium ion secondary battery, and therefore can be suitably used as electrolytic foils for current collectors in lithium ion secondary batteries.

[0041] The advantages of using Cu as the metal layer 20 include that Cu is widely used as a material for existing lithium ion secondary batteries, and is highly reliable as a negative electrode current collector material for lithium ion secondary batteries, and Cu has good electrical conductivity. Furthermore, the use of Ni as the metal layer 20 has the advantage that Ni has excellent sulfur resistance and strength.

[0042] Furthermore, the laminated electrolytic foil A has a first surface 10c and a second surface 10d as shown in Fig. 3. The laminated electrolytic foil A is characterized in that the value obtained by dividing the three-dimensional surface texture parameter Sv by the thickness of the laminated electrolytic foil A is 0.5 or less on both the first surface 10c and the second surface 10d.

[0043] That is, laminated electrolytic foil A of this embodiment includes a Ni-Fe alloy electrolytic layer 10' and a metal layer 20 made of a metal species different from that of the Ni-Fe alloy electrolytic layer 10'. Depending on the metal species, the electrical conductivity, sulfur resistance, strength, etc. of the laminated electrolytic foil as a whole can be adjusted, making it possible to produce a laminated electrolytic foil with desired properties as a negative electrode current collector material for lithium ion secondary batteries.

[0044] In this embodiment, the overall thickness of the laminated electrolytic foil A is 10 μm or less. If the thickness of the laminated electrolytic foil A exceeds 10 μm, as with alloy electrolytic foils, it will not be in line with the design concept of achieving high capacity through thinning, and the cost advantage over known rolled foils will be diminished. While there is no particular lower limit on the overall thickness of the laminated electrolytic foil A, a thickness of 2 μm or more is more preferable from the viewpoint of preventing tearing and wrinkling during battery production. The metal layer 20 in the laminated electrolytic foil A may be formed on both sides of the Ni-Fe alloy electrolytic layer 10' as shown in Fig. 3(a) or on only one side as shown in Fig. 3(b). The thickness of the metal layer 20 may be uniform on both sides of the Ni-Fe alloy electrolytic layer 10' or may vary. The total thickness of the metal layer 20 in the laminated electrolytic foil A is preferably 0.1 μm to 8.0 μm, while the thickness of the Ni—Fe alloy electrolytic layer 10′ in the laminated electrolytic foil A is preferably 2.0 μm to 9.9 μm. The thickness ratio of the Ni-Fe alloy electrolytic layer 10' in the laminated electrolytic foil A is preferably 18 to 95%, and more preferably 35 to 90%. In particular, when the overall thickness of the laminated electrolytic foil A is 8.0 μm or less, the thickness ratio of the Ni-Fe alloy electrolytic layer 10' is preferably 40% or more, and more preferably 48% or more.

[0045] In this embodiment, the "thickness of the laminated electrolytic foil A" is preferably measured by a gravimetric method, as with the "thickness of the alloy electrolytic foil 10" described above. Alternatively, thickness measurement using a micrometer is also applicable. However, when a Ni layer is laminated as the metal layer 20, it is difficult to determine the density and film thickness using a gravimetric method, so thickness measurement using a micrometer is preferred.

[0046] The metal layer 20 may be formed on the first surface 10c of the Ni-Fe alloy electrolytic layer 10' and on the second surface 10d of the Ni-Fe alloy electrolytic layer 10' using the same metal or different metals.

[0047] When laminated electrolytic foil A is produced, metal layer 20, Ni-Fe alloy electrolytic layer 10', and metal layer 20 are laminated in this order on a support made of a titanium plate or a stainless steel plate by plating, and then the entire plating layer (laminated electrolytic foil A) is peeled off from the support to obtain laminated electrolytic foil A. Alternatively, metal layer 20 and Ni-Fe alloy electrolytic layer 10' may be laminated in this order on a support by plating, and then the entire plating layer (laminated electrolytic foil A) may be peeled off from the support to obtain laminated electrolytic foil A. Alternatively, Ni-Fe alloy electrolytic layer 10' and metal layer 20 may be laminated in this order on a support by plating, and then the entire plating layer (laminated electrolytic foil A) may be peeled off from the support to obtain laminated electrolytic foil A.

[0048] The laminated electrolytic foil A is not limited to a three-layer structure, and may have, for example, a four-layer structure, a five-layer structure, or a laminated electrolytic foil having more layers, as long as it includes the Ni-Fe alloy electrolytic layer 10'. However, in terms of cost and ease of production, laminated electrolytic foils having a structure such as "Cu / Ni-Fe alloy / Cu" or "Ni / Ni-Fe alloy / Ni" are preferred.

[0049] The three-dimensional surface texture parameter Sv of the laminated electrolytic foil A of this embodiment can be determined using a known non-contact three-dimensional surface roughness measuring device or the like. In the laminated electrolytic foil A of this embodiment, it is preferable that the values ​​of Sku (peakiness of the histogram of the height distribution), Sv [μm] (maximum valley depth), Sz [μm] (maximum height), and Sa [μm] (arithmetic mean height) on the first surface 10c and the second surface 10d be as follows: Sku: Less than 7.2, preferably 6.0 or less Sv: Less than 2.2, preferably 2.0 or less Sz: Less than 4.7, preferably 4.0 or less Sa: Less than 0.3, preferably 0.25 or less In order to control the three-dimensional surface texture parameters Sku, Sv, Sz, and Sa of the laminated electrolytic foil A of this embodiment within the above-mentioned ranges, it is possible to employ methods such as controlling the plating conditions as described below, polishing the surface of the support, and smoothing the surface of the obtained alloy electrolytic foil by etching or electrolytic polishing.

[0050] Next, the laminated electrolytic foil A of this embodiment can be produced, for example, by the following method. First, the support on which the plating layer is to be formed is subjected to pretreatments such as polishing, wiping, rinsing with water, degreasing, and pickling, and then the support is immersed in a plating bath to form a plating layer for forming metal layer 20 on the support. Next, the support is immersed in a plating bath for forming Ni-Fe alloy electrolytic layer 10' thereon, and then in a plating bath for forming metal layer 20. After the formed plating layer is dried, the entire plating layer is peeled off from the support by a known method, thereby obtaining laminated electrolytic foil A. The surface roughness Sa of the support is preferably 0.14 μm or less, as in the case of producing the Ni—Fe alloy electrolytic layer 10′ described above.

[0051] Furthermore, before or after peeling the laminated electrolytic foil A from the support, the outermost surface of the laminated electrolytic foil A may be subjected to a roughening treatment or anti-rust treatment within the scope of the claims of the present invention, as long as the value obtained by dividing the three-dimensional surface texture parameter Sv by the thickness is 0.5 or less. Alternatively, the outermost surface of the laminated electrolytic foil A may be subjected to a known treatment for imparting conductivity, such as carbon coating. As a method for controlling the surface roughness (three-dimensional surface texture) of the laminated electrolytic foil A of this embodiment, it is possible to adopt a method for controlling plating conditions or a method for polishing the surface of the support, as in the case of the above-mentioned alloy electrolytic foil. Alternatively, it is also possible to obtain the desired three-dimensional surface texture by smoothing the surface of the laminated electrolytic foil A itself by etching or electrolytic polishing.

[0052] When the metal layer 20 is a matte Cu plating layer, the plating conditions are as follows: [Matte Cu plating conditions] Bath composition: A known copper sulfate bath with copper sulfate as the main component (an example is shown below) Copper sulfate pentahydrate: 150~250g / L Sulfuric acid: 30~60g / L Hydrochloric acid (35%): 0.1-0.5 ml / L ·Temperature: 25~70℃ ·pH: 1 or less Agitation: Air agitation or jet agitation ·Current density: 1~30A / dm 2

[0053] The preferable relationship between the bath temperature and the current density is as follows: First, when the bath temperature is between 25°C and 70°C, the current density is 1 A / dm 2 In this case, the current density is preferably 1 A / dm or more. 2If the thickness is less than 1000 nm, the resulting Cu layer may have a high surface roughness on the deposition surface, and sufficient tensile strength may not be obtained.

[0054] When the bath temperature is below 25°C, the current density is 5 to 40 A / dm 2 Even if the thickness is within the appropriate range, it is not preferable because it may result in problems such as a decrease in plating deposition efficiency and difficulty in obtaining a sufficient tensile strength in the resulting Cu layer. On the other hand, when the bath temperature exceeds 70°C, the current density is 5 to 40 A / dm 2 Even if the thickness is within the appropriate range, it is not preferable because there are problems such as high surface roughness on the deposition surface of the obtained Cu layer and difficulty in obtaining sufficient tensile strength.

[0055] If the pH exceeds 1, the surface roughness of the deposition surface of the resulting Cu layer increases, and sufficient tensile strength is difficult to obtain, which is undesirable.

[0056] The above-mentioned matte Cu plating bath can be converted into a bright Cu plating bath by adding 1 to 20 ml / L of a brightener. Known brighteners can be used as brighteners for bright Cu plating, and are not particularly limited. Examples include organic sulfur compounds such as saccharin and sodium naphthalene sulfonate, aliphatic unsaturated alcohols such as polyoxyethylene adducts, unsaturated carboxylic acids, formaldehyde, and coumarin.

[0057] When the metal layer 20 is to be a matte Ni plating layer, examples of plating conditions are as follows: For matte Ni plating, the following known Watts bath or sulfamic acid bath can be used.

[0058] [Matte Ni plating (Watts bath) conditions] Bath composition: Known Watts bath (an example is given below) Nickel sulfate hexahydrate: 200~350g / L Nickel chloride hexahydrate: 20-50g / L Boric acid (or citric acid): 20-50g / L Temperature: 25-70°C (preferably 30-40°C) pH: 3-5 Agitation: Air agitation or jet agitation ·Current density: 1~40A / dm 2 (Preferably 8 to 20 A / dm 2 )

[0059] The preferable relationship between the bath temperature and the current density is as follows: First, when the bath temperature is between 25°C and 45°C, the current density is 5 to 20 A / dm 2 In this case, the current density is preferably 20 A / dm because the tensile strength of the Ni layer can be increased. 2 If the current density exceeds 5A / dm, the problem of the Ni plating film not being formed occurs. 2 If the thickness is less than this, the surface roughness of the deposition surface of the resulting Ni layer will be so high that it is more likely to break, and sufficient strength will be difficult to obtain.

[0060] When the bath temperature is above 45°C and below 70°C, the current density is 3 to 10 A / dm 2 It is preferable that the tensile strength of the Ni layer is increased, and the range is 3 to 6 A / dm 2 For the same reasons as above, it is more preferable that the current density is 3 A / dm 2 If the current density is less than 10 A / dm, the surface roughness of the deposited surface of the resulting Ni layer increases, which is undesirable because it increases the possibility of foil breakage and drastically reduces productivity. 2 If the temperature exceeds this range, it may be difficult to obtain sufficient strength for the Ni layer to be formed.

[0061] A pH of less than 3 is undesirable because it reduces the plating deposition efficiency, while a pH of more than 5 is undesirable because it can cause sludge to be entrained in the resulting layer.

[0062] The above-mentioned matte Ni plating bath can be converted into a bright Ni plating bath by adding 0.1 to 20 ml / L of a brightener. Known brighteners can be used as brighteners for bright Ni plating, and are not particularly limited. Examples include organic sulfur compounds such as saccharin and sodium naphthalene sulfonate, aliphatic unsaturated alcohols such as polyoxyethylene adducts, unsaturated carboxylic acids, formaldehyde, and coumarin. A suitable amount of a pitting inhibitor may also be added to the matte Ni plating bath or a bath containing a brightener. In the case of bright Ni plating, the plating conditions are as follows: bath temperature 30 to 60°C, current density 5 to 40 A / dm 2 The reason for this is the same as in the case of the above-mentioned matte Ni plating bath.

[0063] [Matte Ni plating (sulfamic acid bath) conditions] Bath composition: Known sulfamate nickel plating bath (an example is shown below) Nickel sulfamate: 150-300g / L Nickel chloride hexahydrate: 1 to 10 g / L Boric acid: 5~40g / L ·Temperature: 25~70℃ pH: 3-5 Agitation: Air agitation or jet agitation ·Current density: 5~30A / dm 2 Furthermore, the above-mentioned known brighteners may be added to the plating bath to form bright Ni plating or semi-bright Ni plating. An appropriate amount of a pit prevention agent may also be added.

[0064] In this embodiment, an example of producing laminated electrolytic foil A by a continuous production method using a support (for example, a drum method or a roll-to-roll method) has been described, but the present invention is not limited to this embodiment, and production by a batch method using, for example, a cut sheet is also possible. Furthermore, the method of producing Ni-Fe alloy electrolytic layer 10' in laminated electrolytic foil A of this embodiment is the same as that of Ni-Fe alloy electrolytic foil 10 described above, and therefore a detailed description thereof will be omitted here.

[0065] Example The present invention will be described in more detail below with reference to examples. Note that the thicknesses described in the examples are target values, and the actual measured values ​​of the thickness (total thickness) are shown in the tables. First, the measurement methods used in the examples will be described.

[0066] [Measurement of tensile strength] The tensile strength of the obtained alloy electrolytic foil or laminated electrolytic foil was measured as follows. First, metal pieces were punched out using an SD-type lever-type sample cutter (model: SDL-200) manufactured by Dumbbell Co., Ltd., with a cutter (model: SDK-400) conforming to JIS K6251-4. Next, a tensile test was performed on these test pieces in accordance with the tensile test method conforming to JIS Z 2241, the JIS standard for metal test pieces. A schematic diagram of the test piece is shown in Figure 2. The mechanical strength (tensile strength) was measured by a tensile test using a tensile testing machine (ORIENTEC Universal Material Testing Machine Tensilon RTC-1350A) at room temperature and a tensile speed of 10 mm / min.

[0067] [Thickness measurement] The thickness of the obtained alloy electrolytic foils or laminated electrolytic foils was measured by gravimetry in Examples 1 to 17 and Comparative Example, and by a micrometer in Examples 18 to 25. The thickness was measured by the gravimetric method as follows. The obtained alloy electrolytic foil was punched out to a diameter of 49 mm. The punched alloy electrolytic foil was then quantified using an ICP optical emission spectrometer ICPE-9000 manufactured by Shimadzu Corporation to measure the weight of each metal per unit area, and the film thickness was calculated by comparing this with the density of each metal. The layer structure of the laminated electrolytic foil was confirmed by a cross-sectional image.

[0068] [Surface shape measurement] The surface of the obtained alloy electrolytic foil or laminated electrolytic foil that was in contact with the support (substrate surface) was designated 10a, and the other surface (electrolytic surface) was designated 10b. The surface shape of each surface was measured. Specifically, using an Olympus OLS5000 laser microscope, the following values ​​were measured: Sku (peakiness of the height distribution histogram), Sv [μm] (maximum valley depth), Sz [μm] (maximum height), and Sa [μm] (arithmetic mean height). The Sv [μm] / total thickness [μm] ratio was calculated, and the results are shown in Table 2.

[0069] Example 1 A Ni-Fe alloy plating was formed on a support. Specifically, a Ti material was used as the support on which the alloy electrolytic foil was formed, and the surface of the Ti material was polished until the surface roughness Sa of the Ti material reached the values ​​shown in Table 1. The polishing direction was approximately parallel to the longitudinal direction of the Ti material (the direction of travel during continuous production, the longitudinal direction). This Ti material underwent known pretreatments such as pickling with 7 wt% sulfuric acid and rinsing with water. The pretreated Ti material was then immersed in the Ni-Fe alloy plating bath described below and electrodeposited, forming a 2.0 μm-thick Ni-Fe alloy electrolytic plating layer on the Ti material as an electrolytic foil.

[0070] [Ni-Fe alloy plating conditions] ·Bath composition Nickel sulfate hexahydrate: 230g / L Iron sulfate heptahydrate: 20g / L Nickel chloride hexahydrate: 45g / L Boric acid: 30g / L Trisodium citrate: 10g / L Sodium saccharin: 5g / L Anti-pitting agent: 1ml / L ·Temperature: 60℃ pH: 2.5 Agitation: Air agitation ·Current density: 30A / dm 2 The Ni content in the Ni-Fe alloy plating was 86.9 wt%, and the Fe content was 13.1 wt%. The Ni content and the Fe content for determining the Fe content were measured by dissolving the Ni-Fe alloy layer of Example 1 and performing ICP optical emission spectrometry (measuring device: Shimadzu Corporation, inductively coupled plasma optical emission spectrometer ICPE-9000). For the sake of convenience, the above ratio is expressed as "86.9NiFe" in Table 1. The same applies to the following examples.

[0071] Next, the plated layer formed as described above was thoroughly dried, and then the plated layer was peeled off from the Ti material to obtain an electrolytic alloy foil.

[0072] <Example 2> The same procedure as in Example 1 was carried out, except that the Ni-Fe alloy plating conditions were as follows. [Ni-Fe alloy plating conditions] ·Bath composition Nickel sulfate hexahydrate: 200g / L Iron sulfate heptahydrate: 50g / L Nickel chloride hexahydrate: 45g / L Boric acid: 30g / L Trisodium citrate: 10g / L Sodium saccharin: 5g / L Anti-pitting agent: 1ml / L ·Temperature: 60℃ pH: 2.5 Agitation: Air agitation ·Current density: 10A / dm 2 The Ni content in the Ni-Fe alloy plating was 60.8 wt%, and the Fe content was 39.2 wt%. The Ni content and the Fe content for determining the Fe content were measured by dissolving the Ni-Fe alloy layer of Example 2 and performing ICP optical emission spectrometry (measuring device: Shimadzu Corporation, inductively coupled plasma optical emission spectrometer ICPE-9000). For the sake of convenience, the above ratio is expressed as "60.8NiFe" in Table 1. The same applies to the following examples.

[0073] Example 3 The same procedure as in Example 1 was carried out except that the thickness of the alloy electrolytic foil was set to 4 μm.

[0074] Example 4 The same procedure as in Example 2 was carried out except that the thickness of the alloy electrolytic foil was set to 4 μm.

[0075] <Example 5> The same procedure as in Example 3 was carried out except that the surface roughness Sa of the Ti material serving as the support on which the alloy electrolytic foil was formed was set as shown in Table 1.

[0076] Example 6 The same procedure as in Example 3 was carried out except that the support on which the alloy electrolytic foil was formed was made of SUS316L material having a surface roughness Sa as shown in Table 1.

[0077] Example 7 The same procedure as in Example 6 was carried out except that the surface roughness Sa of the SUS316L material serving as the support on which the alloy electrolytic foil was formed was set as shown in Table 1, and the polishing direction of the surface of the SUS316L material was set to the horizontal direction.

[0078] Example 8 The same procedure as in Example 1 was carried out except that the thickness of the alloy electrolytic foil was set to 10 μm.

[0079] Example 9 The same procedure as in Example 2 was carried out except that the thickness of the alloy electrolytic foil was set to 10 μm.

[0080] Example 10 Three plating layers were formed on the support in this order: a matte Cu plating layer, a Ni-Fe alloy plating layer, and a matte Cu plating layer, to prepare a laminated electrolytic foil. Specifically, first, a Ti material as a support prepared in the same manner as in the example was immersed in a matte Cu plating bath shown below, and a matte Cu plating layer having a thickness of 1 μm was formed on the Ti material as an electrolytic foil.

[0081] [Matte Cu plating conditions] Bath composition: Copper sulfate plating bath with 200g / L of copper sulfate as the main component Copper sulfate pentahydrate: 200g / L Sulfuric acid: 45g / L ·Temperature: 35℃ ·pH: 1 or less Agitation: Air agitation ·Current density: 10A / dm 2

[0082] Next, the Ti material on which the matte Cu plating layer was formed was immersed in the Ni-Fe alloy plating bath shown below, similar to that in Example 1, to form a Ni-Fe alloy plating layer having a thickness of 2 μm on the matte Cu plating layer.

[0083] Next, the Ti material with the matte Cu plating layer and Ni-Fe alloy plating layer formed thereon was further immersed in a matte Cu plating bath, and a 1 μm-thick matte Cu plating layer was formed as the third metal layer. Next, the three plating layers formed as described above were thoroughly dried, and then the plating layers were peeled off from the Ti material to obtain a laminated metal foil.

[0084] Example 11 The same procedure as in Example 10 was carried out except that the Ni—Fe alloy plating conditions were the same as in Example 2.

[0085] Example 12 The same procedure as in Example 10 was carried out, except that the thickness of the Ni-Fe alloy plating layer was set to 8 μm.

[0086] Example 13 The same procedure as in Example 10 was carried out, except that the thickness of the matte Cu plating layer was set to 3 μm and the thickness of the Ni—Fe alloy plating layer was set to 4 μm.

[0087] Example 14 The same procedure as in Example 10 was carried out, except that the thickness of the matte Cu plating layer was set to 4 μm and the thickness of the Ni—Fe alloy plating layer was set to 2 μm.

[0088] Example 15 The same procedure as in Example 11 was carried out, except that the thickness of the Ni-Fe alloy plating layer was set to 8 μm.

[0089] Example 16 The same procedure as in Example 11 was carried out, except that the thickness of the matte Cu plating layer was set to 3 μm and the thickness of the Ni—Fe alloy plating layer was set to 4 μm.

[0090] Example 17 The same procedure as in Example 11 was carried out, except that the thickness of the matte Cu plating layer was set to 4 μm and the thickness of the Ni—Fe alloy plating layer was set to 2 μm.

[0091] Example 18 Three plating layers were formed on the support in this order: a matte Ni plating layer, a Ni-Fe alloy plating layer, and a matte Ni plating layer, to create a laminated electrolytic foil. Specifically, first, a Ti material as a support prepared in the same manner as in Example 1 was immersed in a matte Ni plating bath shown below, and a matte Ni plating layer having a thickness of 1 μm was formed on the Ti material as an electrolytic foil.

[0092] [Matte Ni plating conditions] Bath composition: Watts bath Nickel sulfate hexahydrate: 250g / L Nickel chloride hexahydrate: 45g / L Boric acid: 30g / L Anti-pitting agent: 1ml / L ·Temperature: 60℃ pH: 4.5 Agitation: Air agitation ·Current density: 10A / dm 2

[0093] Next, the Ti material on which the matte Ni plating layer was formed was immersed in the Ni-Fe alloy plating bath shown below, which was the same as in Example 1, to form a Ni-Fe alloy plating layer with a thickness of 2 μm on the matte Ni plating layer.

[0094] Next, the Ti material with the matte Ni plating layer and Ni-Fe alloy plating layer formed thereon was further immersed in a matte Ni plating bath, and a 1 μm-thick matte Ni plating layer was formed as the third metal layer. Next, the three plating layers formed as described above were thoroughly dried, and then the plating layers were peeled off from the Ti material to obtain a laminated metal foil.

[0095] Example 19 The same procedure as in Example 18 was carried out except that the Ni—Fe alloy plating conditions were the same as in Example 2.

[0096] Example 20 The same procedure as in Example 18 was carried out, except that the thickness of the Ni-Fe alloy plating layer was set to 8 μm.

[0097] Example 21 The same procedure as in Example 18 was carried out except that the thickness of the matte Ni plating layer was set to 3 μm and the thickness of the Ni—Fe alloy plating layer was set to 4 μm.

[0098] Example 22 The same procedure as in Example 18 was carried out except that the thickness of the matte Ni plating layer was set to 4 μm and the thickness of the Ni—Fe alloy plating layer was set to 2 μm.

[0099] Example 23 The same procedure as in Example 19 was carried out, except that the thickness of the Ni-Fe alloy plating layer was set to 8 μm.

[0100] Example 24 The same procedure as in Example 19 was carried out, except that the thickness of the matte Ni plating layer was set to 3 μm and the thickness of the Ni—Fe alloy plating layer was set to 4 μm.

[0101] Example 25 The same procedure as in Example 19 was carried out, except that the thickness of the matte Ni plating layer was set to 4 μm and the thickness of the Ni—Fe alloy plating layer was set to 2 μm.

[0102] Example 26 The electrolytic alloy foil obtained under the same conditions as in Example 9 was subjected to a heat treatment under the annealing conditions (temperature and time) shown in Table 1A to obtain an annealed material of the electrolytic alloy foil.

[0103] Example 27 The electrolytic alloy foil obtained under the same conditions as in Example 9 was subjected to a heat treatment under the annealing conditions (temperature and time) shown in Table 1A to obtain an annealed material of the electrolytic alloy foil.

[0104] Example 28 The current density for Ni-Fe alloy plating was 5A / dm 2 The same procedure as in Example 9 was carried out except that:

[0105] Example 29 The current density for Ni-Fe alloy plating was 20 A / dm 2 The same procedure as in Example 9 was carried out except that:

[0106] Example 30 The current density for Ni-Fe alloy plating was 30A / dm 2 The same procedure as in Example 9 was carried out except that:

[0107] <Comparative Example 1> The same procedure as in Example 1 was carried out except that the surface roughness Sa of the Ti material serving as the support on which the alloy electrolytic foil was formed was set as shown in Table 1.

[0108] <Comparative Example 2> A Ti material as a support prepared in the same manner as in Example 1 was immersed in a matte Ni plating bath similar to that in Example 19, and a matte Ni plating layer having a thickness of 4 μm was formed on the Ti material as an electrolytic foil. After the formed matte Ni plating layer was thoroughly dried, the plating layer was peeled off from the Ti material to obtain an electrolytic metal foil.

[0109] <Comparative Example 3> The same procedure as in Comparative Example 2 was carried out, except that the thickness of the matte Ni plating layer was set to 10 μm.

[0110] <Comparative Example 4> A Ti material as a support prepared in the same manner as in Example 1 was immersed in the same matte Cu plating bath as in Example 11, and a matte Cu plating layer having a thickness of 10 μm was formed on the Ti material as an electrolytic foil. After the formed matte Cu plating layer was thoroughly dried, the plating layer was peeled off from the Ti material to obtain an electrolytic metal foil.

[0111] <Comparative Example 5> The electrodeposited metal foil obtained under the same conditions as in Comparative Example 4 was subjected to heat treatment under the annealing conditions (temperature and time) shown in Table 1A to obtain an annealed electrodeposited metal foil.

[0112] [Table 1A]

[0113] [Table 1B]

[0114] [Table 2]

[0115] It was confirmed that each example had desirable properties such as tensile strength, etc. On the other hand, it was confirmed that Comparative Example 1 could not achieve the objective in terms of tensile strength.

[0116] Furthermore, according to Comparative Examples 2 to 4, when compared with the results of the Examples using Ni-Fe alloy electrolytic foils of the same thickness, it was confirmed that the Ni-Fe alloy electrolytic foils were preferable in terms of tensile strength. Furthermore, a comparison of the results of Examples 26 to 27 and Comparative Example 5 confirmed that the alloy electrolytic foil of the present embodiment can maintain a preferable tensile strength even when subjected to a heat treatment step for drying purposes, for example, during secondary battery production.

[0117] The above-described embodiment and examples can be modified in various ways without departing from the spirit of the present invention. Furthermore, the alloy electrolytic foils and laminated electrolytic foils in the above-described embodiments and examples have been described as being used primarily as current collectors for batteries. However, the alloy electrolytic foils and laminated metal foils of the present invention are not limited to current collectors and can also be used for other purposes, such as heat dissipation materials and electromagnetic wave shielding materials. [Industrial Applicability]

[0118] As explained above, the laminated metal foil, battery current collector, and battery of the present invention can be applied to a wide range of industrial fields, including automobiles and electronic devices. [Explanation of symbols]

[0119] 10 Ni-Fe alloy electrolytic foil 10' Ni-Fe alloy electrolytic layer 10a 1st page 10b 2nd side 10c page 1 10d 2nd side 20 metal layer A. Laminated electrolytic foil

Claims

1. An electrolytic foil comprising a Ni-Fe alloy layer and at least one metal layer made of a metal species different from that of the Ni-Fe alloy layer, The thickness of the electrolytic foil is 1.5 μm to 10 μm, The thickness ratio of the Ni—Fe alloy layer in the electrolytic foil is 18 to 95%, the electrolytic foil has a first surface and a second surface, and a value obtained by dividing a three-dimensional surface texture parameter Sv by the thickness of the first surface and the second surface is 0.5 or less. An electrolytic foil containing a Ni—Fe alloy layer.

2. 2. The electrolytic foil according to claim 1, wherein the Ni—Fe alloy layer has a thickness of 2.0 μm to 9.9 μm.

3. The electrolytic foil according to claim 1 or 2, wherein the total thickness of the metal layers is 0.1 μm to 8.0 μm.

4. The electrolytic foil according to any one of claims 1 to 3, having a tensile strength of more than 720 MPa.

5. A current collector for a battery, comprising the electrolytic foil according to any one of claims 1 to 4.

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