JP7052246B2 - Material for secondary battery negative electrode current collector - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act Publication date February 16, 2017 Publication address https: // doi. org / 10.1016 / j. jpowerour. 2017.02.014

The present invention relates to a material for a negative electrode current collector of a secondary battery, and relates to a material for a negative electrode current collector of a secondary battery including a layer (material) made of Cu (copper) or a Cu alloy.

Conventionally, a material for a secondary battery negative electrode current collector including a layer (material) made of Cu or a Cu alloy is known (see, for example, Patent Document 1).

Patent Document 1 discloses a negative electrode current collector (material for a secondary battery negative electrode current collector) made of Cu or a Cu alloy and whose surface is coated with Cu ₂ O.

Japanese Patent Application Laid-Open No. 2003-132894

However, the inventor of the present application has insufficient rust prevention in the negative electrode current collector described in Patent Document 1, and oxidation proceeds in the atmosphere, resulting in contact resistance between the negative electrode current collector and the active material. There is a problem that the resistance in the battery cell using the negative electrode current collector also increases.

Here, for rust prevention, a chromate treatment for forming a passivation film on the surface by immersing a material for a secondary battery negative electrode current collector made of Cu or a Cu alloy in a solution containing hexavalent Cr (chromium). It is conceivable to do. However, since hexavalent Cr contained in the treated solution has a large environmental load, it is not preferable to perform chromate treatment from the viewpoint of environmental load.

The present invention has been made to solve the above-mentioned problems, and one object of the present invention is a secondary having a sufficient rust preventive effect by a method other than the formation of a passivation film by chromate treatment. It is to provide a material for a battery negative electrode current collector.

As a result of diligent studies to solve the above problems, the inventor of the present application has a crystal phase of CuO (copper oxide (II) oxide) instead of Cu _2O (copper oxide (I)) on the surface layer of the Cu material (Cu layer). It was found that the progress of oxidation is suppressed and a rust-preventive effect is produced when the amount of copper is contained in a predetermined ratio or more. Based on such findings, the present invention has been completed.

That is, the material for the negative electrode current collector of the secondary battery according to the first aspect of the present invention includes a plate-shaped Cu material composed of Cu or a Cu alloy, and the Cu material has a CuO crystal phase and Cu ₂ on at least the plate surface. It has a surface layer containing a crystal phase of O and a crystal phase of Cu (OH) ₂ , and an area obtained by the area of the crystal phase of CuO in the surface layer / (area of the crystal phase of CuO + area of the crystal phase of Cu _2O ). The ratio (percentage) is 55.1% or more, depending on the area of the CuO crystal phase in the surface layer / (the area of the CuO crystal phase + the area of the Cu ₂ O crystal phase + the Cu (OH) ₂ crystal phase). The desired area ratio (percentage) is 15.0% or more . Here, "the area of the crystal phase of CuO" means CuO at the peak of Cu2p _3/2 when the narrow scan spectrum of Cu2p is acquired by using X-ray Photoelectron spectroscopy (XPS). And the ratio (area ratio) of the area of the CuO crystal phase to the total area of the CuO crystal phase and the Cu _2O crystal phase based on the Cu ₂ O peak. Similarly, the "area of the crystal phase of Cu ₂ O" is Cu ₂ with respect to the total area of the crystal phase of Cu O and the crystal phase of Cu ₂ O, which is obtained based on the above peaks of Cu O and Cu ₂ O by XPS. It is the ratio (area ratio) of the area of the crystal phase of O. Further, the "Cu alloy" means an alloy containing 50% by mass or more of Cu (copper).

In the material for the negative electrode current collector of the secondary battery according to the first aspect of the present invention, as described above, the surface layer containing the crystal phase of CuO having an area ratio of 55.1% or more is at least a plate of a plate-shaped Cu material. By having it on the surface, it is possible to suppress the progress of oxidation to the region inside the surface layer of the Cu material composed of Cu or Cu alloy. As a result, a sufficient rust preventive effect can be produced without forming a passivation film by chromate treatment. Therefore, a secondary method having a sufficient rust preventive effect can be obtained by a method other than the passivation film formation by chromate treatment. A material for a battery negative electrode current collector can be provided. As a result, oxidation progresses in the atmosphere, and a negative electrode current collector made of a material for a secondary battery negative electrode current collector provided with a plate-shaped Cu material and the surface of the negative electrode current collector (plate-shaped Cu material plate). It is possible to suppress an increase in contact resistance with the negative electrode active material layer bonded to the surface). It has been confirmed by an experiment described later that the crystal phase of CuO can suppress the progress of oxidation in the region inside the surface layer of the Cu material. Further, in the surface layer containing not only the crystal phase of CuO and the crystal phase of Cu 2O _but also the crystal phase of Cu (OH) ₂ , the surface layer has a crystal phase of CuO having an area ratio of 15.0% or more. , It is possible to suppress the progress of oxidation to the region inside the surface layer of the Cu material. Further, Cu (OH) ₂ (copper hydroxide) is relatively unstable, and is, for example, due to heat generated when a negative electrode active material is bound onto a secondary battery negative electrode current collector material via a resin material. , Cu (OH) ₂ can be changed to CuO. That is, by further containing the crystal phase of Cu (OH) ₂ in the surface layer, the area ratio of the crystal phase of CuO can be further increased by heating or the like.

Further, the material for the negative electrode current collector of the secondary battery according to the second aspect of the present invention includes a core material layer made of metal and a Cu layer bonded to the core material layer and made of Cu or a Cu alloy. Equipped with a plate-shaped clad material,
The clad material has a surface layer containing a CuO crystal phase, a Cu2O crystal phase , and a Cu (OH) ₂ crystal phase _on a surface opposite to the surface bonded to the core material layer of the Cu layer in the thickness direction. The area ratio (percentage) obtained by the area of the CuO crystal phase in the surface layer / (the area of the CuO crystal phase + the area of the Cu _2O crystal phase) is 55.1% or more, and is in the surface layer. The area ratio (percentage) obtained by the area of the crystal phase of CuO / (the area of the crystal phase of CuO + the area of the crystal phase of Cu ₂ O + the crystal phase of Cu (OH) ₂ ) is 15.0% or more.

In the secondary battery negative electrode current collector material according to the second aspect of the present invention, even when applied to the clad material of the core material layer and the Cu layer, the secondary battery negative electrode current collector material according to the first aspect is the same. Similarly, Cu or Cu is provided by having a surface layer containing a CuO crystal phase having an area ratio of 55.1% or more on a surface opposite to the surface bonded to the core material layer of the Cu layer in the thickness direction. It is possible to suppress the progress of oxidation to the region inside the surface layer of the Cu layer composed of the alloy. As a result, a sufficient rust preventive effect can be produced without forming a passivation film by chromate treatment. Therefore, a clad material having a sufficient rust preventive effect can be obtained by a method other than forming a passivation film by chromate treatment. It is possible to provide a material for a secondary battery negative current collector comprising the above. Further, in the surface layer containing not only the crystal phase of CuO and the crystal phase of Cu 2O _but also the crystal phase of Cu (OH) ₂ , the surface layer has a crystal phase of CuO having an area ratio of 15.0% or more. , It is possible to suppress the progress of oxidation to the region inside the surface layer of the Cu material. Further, Cu (OH) ₂ (copper hydroxide) is relatively unstable, and is, for example, due to heat generated when a negative electrode active material is bound onto a secondary battery negative electrode current collector material via a resin material. , Cu (OH) ₂ can be changed to CuO. That is, by further containing the crystal phase of Cu (OH) ₂ in the surface layer, the area ratio of the crystal phase of CuO can be further increased by heating or the like.

In the material for the negative electrode current collector of the secondary battery according to the second aspect, the core material layer is preferably made of Ni, Ni alloy, Fe or Fe alloy. With this configuration, in the clad material between the core material layer and the Cu layer, a core material layer having a mechanical strength higher than that of the Cu layer can be used. As a result, for example, when the material for the negative electrode current collector of the secondary battery is used as the negative electrode current collector of the lithium ion secondary battery, the stress caused by the expansion and contraction of the negative electrode active material arranged on the negative electrode current collector Can definitely resist. As a result, it is possible to suppress the occurrence of problems such as wrinkles and tears in the negative electrode current collector. The "Ni alloy" and "Fe alloy" mean alloys containing 50% by mass or more of Ni (nickel) and Fe (iron), respectively.

In the material for the negative electrode current collector of the secondary battery according to the first or second aspect, the ten-point average roughness in the surface layer is preferably 0.30 μm or more. With this configuration, the negative electrode active material can be reliably arranged on the surface layer which has been roughened to some extent and has irregularities.

In this case, preferably, a resin material for adhering the negative electrode active material is provided on the surface. With this configuration, the unevenness formed on the surface layer and the increase in the surface area of the surface layer make it possible to reliably adhere the resin material on the surface layer. This makes it possible to reliably bind the negative electrode active material on the surface of the secondary battery negative electrode current collector material by the resin material.

According to the present invention, as described above, it is possible to provide a material for a secondary battery negative electrode current collector having a sufficient rust preventive effect by a method other than forming a passivation film by chromate treatment.

It is a schematic cross-sectional perspective view which showed the lithium ion secondary battery which comprises the negative electrode using the material for the negative electrode current collector of the secondary battery by 1st Embodiment of this invention. It is sectional drawing which showed the negative electrode using the material for the secondary battery negative electrode current collector by 1st Embodiment of this invention. It is an enlarged cross-sectional view which showed the periphery of the surface layer of the material (negative electrode current collector) for the secondary battery negative electrode current collector according to 1st Embodiment of this invention. It is sectional drawing which showed the negative electrode using the material for the secondary battery negative electrode current collector by 2nd Embodiment of this invention. It is a graph which showed the spectrum of the test material 2 in the surface layer analysis performed for confirming the effect of this invention. It is a graph which showed the spectrum of the test material 7 in the surface layer analysis performed for confirming the effect of this invention. It is a schematic perspective view for demonstrating the peeling test performed in order to confirm the effect of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
First, with reference to FIGS. 1 to 3, a lithium ion secondary battery 100 (hereinafter referred to as a battery 100) using a material for a secondary battery negative electrode current collector (negative electrode current collector 50) according to the first embodiment of the present invention is used. The configuration of the negative electrode current collector 50 will be described.

(Lithium-ion secondary battery)
As shown in FIG. 1, the battery 100 includes a cylindrical housing 1, a lid material 2 for sealing the opening of the housing 1, and a storage element 3 arranged in the housing 1. The housing 1 is made of a Ni-plated steel plate and also serves as a negative electrode terminal of the battery 100.

The storage element 3 and the electrolytic solution (not shown) are housed in the housing 1. The lid material 2 is made of an aluminum alloy or the like, and also serves as a positive electrode terminal of the battery 100. The power storage element 3 is formed by winding a positive electrode 4, a negative electrode 5, and an insulating separator 6 arranged between the positive electrode 4 and the negative electrode 5. The positive electrode 4 includes a positive electrode current collector (not shown) made of aluminum foil and a positive electrode active material layer (not shown) arranged on the surface of the positive electrode current collector. The positive electrode active material layer has a positive electrode active material such as lithium manganate and a binder composed of a resin material.

The battery 100 includes a positive electrode lead material 7 for connecting the positive electrode 4 and the positive electrode terminal (cover material 2), and a negative electrode lead material 8 for connecting the negative electrode 5 and the negative electrode terminal (housing 1). Further prepare. The positive electrode lead material 7 is made of aluminum foil, and is joined to the positive electrode current collector of the positive electrode 4 and the lid material 2 by resistance welding or the like. The negative electrode lead material 8 is made of copper foil, and is joined to the negative electrode current collector 50 (see FIG. 2) of the negative electrode 5 and the housing 1 by resistance welding or the like.

(Negative electrode)
As shown in FIG. 2, the negative electrode 5 includes a negative electrode current collector 50 and a negative electrode active material layer 51 arranged on the surface 50a of the negative electrode current collector 50.

The negative electrode active material layer 51 is composed of a negative electrode active material (not shown) composed of C (carbon), Si (silicon), silicon oxide, Sn (tin), tin oxide, etc., and a negative electrode active material for collecting negative electrodes. It has a binder for adhering on the surface 50a of the body 50.

The volume of the negative electrode active material increases or decreases by occluding or releasing Li ⁺ (lithium ion) during charging and discharging. Therefore, stress is repeatedly applied to the negative electrode current collector 50 with charging and discharging.

The binder is made of a resin material. The binder is made of, for example, an acrylic resin, a polyimide resin or a fluororesin (for example, polyvinylidene fluoride (PVDF)). Here, as the binder composed of the acrylic resin, an aqueous slurry can be used, and a mixture layer (negative electrode active material layer 51) can be easily provided by coating. In addition, the binder made of polyimide resin has excellent mechanical properties and the mixture layer does not easily collapse.

The negative electrode current collector 50 is made of a material for a secondary battery negative electrode current collector including a plate-shaped (foil-shaped) Cu material 52 made of Cu or a Cu alloy. Examples of Cu (pure copper) include so-called C1000 series (JIS standard) oxygen-free copper, phosphorus deoxidized copper, and tough pitch copper. Further, as the Cu alloy, there are C2000 series (JIS standard) and the like. The thickness t1 of the negative electrode current collector 50 is preferably smaller because it is wound as a part of the power storage element 3 (see FIG. 1) in the battery 100.

Here, in the first embodiment, the Cu material 52 is a surface containing a CuO crystal phase, a Cu2O crystal phase, and a Cu _{(OH) 2 crystal} phase formed by an oxidation treatment as a rust preventive treatment. It has a layer 53. Then, the area ratio A1 obtained by the area ratio of the crystal phase of CuO in the surface layer 53 (referred to as the area ratio A1), that is, the area of the crystal phase of CuO / (the area of the crystal phase of CuO + the area of the crystal phase of Cu _2O ). (Percentage) is 22.0% or more. The area ratio A1 is preferably larger than 30.0%, more preferably 40.0% or more, and the area of the crystal phase of CuO is equal to or more than the area of the crystal phase of Cu _2O . It is more preferably 50.0% or more.

Further, in the surface layer 53, the area ratio of the crystal phase of CuO (referred to as the area ratio B1) from another viewpoint, that is, the area of the crystal phase of CuO / (the area of the crystal phase of CuO + the area of the crystal phase of Cu _2O + Cu). The area ratio B1 (percentage) obtained by (the area of the crystal phase of (OH) ₂ ) is preferably 15.0% or more. The area ratio B1 is more preferably 30.0% or more, more preferably 35.0% or more, and the area of the crystal phase of CuO is the crystal phase of Cu ₂ O and Cu (OH) ₂ . It is more preferably 50.0% or more, which is equal to or more than the total area with the crystal phase of.

The area ratio of the crystal phase of CuO in the surface layer 53, the area ratio of the crystal phase of Cu ₂ O, and the area ratio of the crystal phase of Cu (OH) ₂ are the XPS (also known as ESCA: Electron Specroscopic) with respect to the surface layer 53. It is obtained by performing for Chemical Analysis). Specifically, a narrow scan spectrum of Cu2p is acquired using XPS (ESCA). Then, from the spectrum around the peak of the binding energy of Cu 2p _3/2 , the peak of the crystal phase of CuO (933.6 eV), the peak of the crystal phase of Cu ₂ O (932.5 eV), and the crystal of Cu (OH) ₂ . The peak of the phase (935.1 eV) is separated, and the area ratio of _{each crystal phase of CuO, Cu2O, and Cu (OH) 2 is} obtained.

Then, the total area of the peaks of each of the crystal phases of Cu O and Cu ₂ O (referred to as the total area A0) is obtained. Then, the value (percentage) obtained by the ratio of the peak area of the CuO crystal phase to the total area A0, that is, the area of the CuO crystal phase / (the area of the CuO crystal phase + the area of the Cu _2O crystal phase) is obtained. The value is defined as the above area ratio A1. Similarly, the value obtained by the ratio of the peak area of the crystal phase of Cu ₂ O to the total area A0, that is, the area of the crystal phase of Cu ₂ O / (the area of the crystal phase of Cu O + the area of the crystal phase of Cu ₂ O) ( (Percentage) is calculated, and the value is defined as the area ratio A2.

Further, the total area of the peaks of _{each of the crystal phases of CuO, Cu2O, and Cu (OH) 2 (} referred to as the total area B0) is obtained. Then, the ratio of the peak area of the CuO crystal phase to the total area B0, that is, the area of the CuO crystal phase / (the area of the CuO crystal phase + the area of the Cu ₂ O crystal phase + the area of the Cu (OH) ₂ crystal phase). ) Is obtained, and the value is taken as the above area ratio B1. Similarly, the ratio of the peak area of the Cu ₂ O crystal phase to the total area B0, that is, the area of the Cu ₂ O crystal phase / (the area of the Cu O crystal phase + the area of the Cu ₂ O crystal phase + Cu (OH) ₂ ). The value (percentage) obtained from the area of the crystal phase of the above is obtained, and the value is defined as the area ratio B2. Similarly, the ratio of the peak area of Cu (OH) ₂ to the total area B0, that is, the area of the crystal phase of Cu (OH) ₂ / (the area of the crystal phase of CuO + the area of the crystal phase of Cu _2O + Cu (OH)). The value (percentage) obtained from the area of the crystal phase of ₂ ) is obtained, and the value is defined as the area ratio B3.

It should be noted that Cu (OH) ₂ is relatively unstable and can be changed to CuO by heat when arranging the negative electrode active material on the negative electrode current collector 50 via a binder or the like. This makes it possible to further increase the area ratio of the crystal phase of CuO.

Further, the surface layer 53 may contain a crystal phase other than the crystal phase of CuO, the crystal phase of Cu ₂ O, and the crystal phase of Cu (OH) ₂ .

Further, the surface layer 53 is formed so as to cover substantially the entire surface of the Cu material 52. The surface layer 53 may be formed at least on the surface (plate surface) to which the negative electrode active material layer 51 of the Cu material 52 is bonded, and the end surface (FIG. 2) along the thickness direction (Z direction) of the Cu material. In, it does not have to be formed on the surface of the Cu material 52 (left surface and right surface). Further, the thickness t2 of the surface layer 53 is 50 nm or less, which is sufficiently smaller than that of the Cu material 52. As a result, it is possible to suppress an increase in contact resistance due to the surface layer 53 when the lead material 8 for the negative electrode is bonded. Further, the thickness t2 of the surface layer 53 is preferably 20 nm or less. As a result, since the thickness t2 of the surface layer 53 is very small, the appearance of the negative electrode current collector 50 is such that the color of the crystal phase constituting the surface layer 53 (for example, black of CuO or reddish brown of Cu _2O ) is The color of Cu or the Cu alloy (for example, in the case of Cu, red-orange) constituting the Cu material 52 is observed with little observation. In FIG. 2, the thickness t2 of the surface layer 53 is exaggerated for easy understanding.

Further, the surface 50a on the surface layer 53 side of the negative electrode current collector 50 (in FIG. 2, the portion where the negative electrode active material layer 51 of the surface layer 53 is fixed and the portion exposed to the outside) is roughened with respect to the Cu material 52. Fine irregularities are formed. Further, at least a part of the unevenness formed on the Cu material 52 becomes larger than the thickness t2 of the surface layer 53, so that the surface layer 53 is not actually a uniform layer as shown in FIG. As shown in an enlarged and exaggerated manner in FIG. 3, it is formed so as to cover each of the irregularities of the Cu material 52. Then, the negative electrode active material layer 51 penetrates into the unevenness formed on the Cu material 52, so that the adhesion between the negative electrode current collector 50 and the negative electrode active material layer 51 is improved.

In the negative electrode current collector 50 roughened by the roughening treatment, the arithmetic mean roughness Ra on the surface layer 53 side based on JIS B 0601: 1994 is preferably 0.06 μm or more, preferably 0.075 μm or more. It is more preferable to have it. Further, the ten-point average roughness Rz on the surface layer 53 side based on JIS B 0601: 1994 is preferably 0.30 μm or more, and more preferably 0.35 μm or more. Further, the ten-point average roughness Rz on the surface layer 53 side is particularly preferably 0.40 μm or more. As a result, the state in which the negative electrode active material layer 51 is fixed to the negative electrode current collector 50 becomes preferable.

(Manufacturing method of negative electrode current collector)
Next, a method for manufacturing the negative electrode current collector 50 (material for a secondary battery negative electrode current collector) according to the first embodiment of the present invention will be briefly described.

First, a foil-shaped Cu material 52 made of Cu or a Cu alloy is prepared. Then, the Cu material 52 is roughened. In the roughening treatment, so-called soft etching is performed using a weakly acidic aqueous solution containing potassium sulfate. As a result, fine irregularities are formed on the surface of the Cu material 52. By performing soft etching, etching (dissolution) can proceed slowly, so that it is possible to prevent the foil-shaped Cu material 52 having a small thickness from being rapidly etched and excessively dissolved. be.

Then, the Cu material 52 that has been roughened is neutralized and then oxidized as a rust preventive treatment. In the rust prevention treatment, the surface of the roughened Cu material 52 is oxidized using hydrogen peroxide solution. At this time, if the ratio (concentration) of hydrogen peroxide in the hydrogen peroxide solution is increased, the crystal phase of CuO is likely to be formed. Specifically, it is possible to make the area ratio of the crystal phase of CuO 15.0% or more by using a hydrogen peroxide solution having a mass percent concentration of 0.5% or more. In order to increase the area ratio of the crystal phase of CuO, it is preferable to use a hydrogen peroxide solution having a mass percent concentration of 1.0% or more. As a result, a surface layer 53 containing a CuO crystal phase and a Cu2O crystal phase and having an area ratio of the CuO crystal phase of 15.0% or _more is formed on the surface of the Cu material 52. As a result, the negative electrode current collector 50 is manufactured.

After that, the negative electrode active material layer 51 is formed on the surface layer 53 of the produced negative electrode current collector 50. Specifically, a slurry containing a negative electrode active material and a binder is applied onto both surface layers 53 in the thickness direction (Z direction) of the negative electrode current collector 50, dried and cured. As a result, the negative electrode active material layer 51 is fixed on the surface layer 53 of the negative electrode current collector 50, and the negative electrode 5 is manufactured.

<Effect of the first embodiment>
In the first embodiment, the following effects can be obtained.

In the first embodiment, as described above, the Cu material 52 made of Cu or a Cu alloy has an area ratio (area ratio A1) of the crystal phase of CuO in the surface layer 53 of 22.0% or more. It is possible to suppress the progress of oxidation to the region inside the surface layer 53. As a result, a sufficient rust preventive effect can be produced without forming a passivation film by chromate treatment. Therefore, a plate-like plate having a sufficient rust preventive effect can be obtained by a method other than the passivation film formation by chromate treatment. It is possible to provide a material for a secondary battery negative voltage collector (negative voltage collector 50) including a Cu material. As a result, oxidation progresses in the atmosphere, and the contact resistance between the negative electrode current collector 50 made of the material for the negative electrode current collector of the secondary battery and the negative electrode active material layer 51 bonded to the negative electrode current collector 50. Can be suppressed from increasing.

Further, in the first embodiment, preferably, the area ratio (area ratio A1) of the CuO crystal phase in the surface layer 53 is 50.0% or more, that is, the area of the CuO crystal phase in the surface layer 53 is Cu ₂ O. It is equal to or larger than the area of the crystal phase of. With this configuration, it is possible to have a surface layer 53 in which the area of the crystal phase of CuO is larger than the area of the crystal phase of Cu ₂ O. Therefore, the surface of the Cu material 52 is increased by the amount of the area of the crystal phase of CuO. It is possible to surely suppress the progress of oxidation to the region inside the layer 53.

Further, in the first embodiment, the area ratio (area ratio B1) of the crystal phase of CuO in the surface layer 53 is preferably 15.0% or more. With this configuration, in the surface layer 53 containing not only the crystal phase of CuO and the crystal phase of Cu _2O but also the crystal phase of Cu (OH) ₂ , the area ratio B1 of the surface layer 53 is 15.0% or more. By having the crystal phase of CuO, it is possible to suppress the progress of oxidation in the region inside the surface layer 53 of the Cu material 52. Further, by further including the crystal phase of Cu (OH) ₂ which can be changed to CuO by the heat when the surface layer 53 binds the negative electrode active material layer 51, the area ratio of the crystal phase of CuO ( Since the area ratio B1) can be made larger, it is possible to reliably suppress the progress of oxidation to the region inside the surface layer 53 of the Cu material 52.

Further, in the first embodiment, the ten-point average roughness of the surface layer 53 is preferably 0.30 μm or more. With this configuration, the negative electrode active material layer 51 can be reliably fixed on the surface layer 53 which has been roughened to some extent and has irregularities.

Further, in the first embodiment, a binder for adhering the negative electrode active material is arranged on the surface 50a. As a result, the unevenness formed on the surface layer 53 and the increase in the surface area of the surface layer 53 make it possible to reliably bind the binder on the surface layer 53. As a result, the binder can reliably bind the negative electrode active material on the surface 50a of the negative electrode current collector 50. Therefore, even when stress is repeatedly applied to the negative electrode current collector 50 due to charging and discharging, the generation of wrinkles is suppressed, and the negative electrode active material (negative electrode active material layer 51) is suppressed from above the surface 50a of the negative electrode current collector 50. Can be reliably suppressed from falling off.

[Second Embodiment]
Next, the negative electrode 105 according to the second embodiment of the present invention will be described with reference to FIG. In the negative electrode 105 according to the second embodiment, unlike the negative electrode 5 according to the first embodiment, an example in which the negative electrode current collector 150 is composed of the clad material 157 will be described. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

(Negative electrode)
As shown in FIG. 4, the negative electrode 105 includes a negative electrode current collector 150 and a negative electrode active material layer 51 arranged on the surface 150a of the negative electrode current collector 150.

The negative electrode current collector 150 is a plate having a three-layer structure including a core material layer 154 made of metal and a pair of Cu layers 155 and 156 bonded to the core material layer 154 and made of Cu or a Cu alloy, respectively. It is made of a material for a secondary battery negative electrode current collector provided with a clad material 157. The Cu layer 155 is joined to the Z1 side surface of the core material layer 154, and the Cu layer 156 is joined to the Z2 side surface of the core material layer 154. Then, in the clad material 157, at the interface between the core material layer 154 and the Cu layer 155 and the interface between the core material layer 154 and the Cu layer 156, the layers form an interatomic bond by diffusion annealing and are firmly bonded. ing. The thickness t11 of the negative electrode current collector 150 is preferably smaller because it is wound as a part of the power storage element in the battery.

The core material layer 154 is made of a metal having a higher mechanical strength than the Cu layers 155 and 156. For example, the core material layer 154 is preferably composed of Ni, Ni alloy, Fe or Fe alloy. As Ni (pure nickel), there is a so-called NW2200 series (JIS standard) and the like. Further, examples of the Ni alloy include a Ni—Nb alloy and a Ni—Ta alloy. As Fe (pure iron), there is a so-called SPCC (JIS standard) or the like. Further, examples of the Fe alloy include stainless steel (ferrite-based, austenitic-based, precipitation-hardened, and martensitic-based). For example, as a precipitation hardening stainless steel, SUS631 (JIS standard) composed of 17% by mass of Cr, 7% by mass of Ni, 1% by mass of Al, other additives and unavoidable impurities, and the balance Fe. ).

Here, in the second embodiment, the Cu layer 155 and the Cu layer 156 have surface layers 158 and 159, respectively. The surface layers 158 and 159 are _both a CuO crystal phase, a Cu2O crystal phase, and Cu (OH) formed by an oxidation treatment as a rust preventive treatment, similarly to the surface layer 53 of the first embodiment. ) Contains ₂ crystal phases. Then, the area ratio of the CuO crystal phase in the surface layers 158 and 159 (area ratio A1), that is, the area ratio A1 obtained by the area of the CuO crystal phase / (the area of the CuO crystal phase + the area of the Cu _2O crystal phase). (Percentage) is 22.0% or more. The area ratio A1 is preferably larger than 30.0%, more preferably 40.0% or more, and the area of the crystal phase of CuO is equal to or more than the area of the crystal phase of Cu _2O . It is more preferably 50.0% or more.

Further, in the surface layers 158 and 159, the area ratio of the crystal phase of CuO (area ratio B1) from another viewpoint, that is, the area of the crystal phase of CuO / (the area of the crystal phase of CuO + the area of the crystal phase of Cu (OH) ₂ ). The area ratio B1 (percentage) obtained from the area) is preferably 15.0% or more. The area ratio B1 is more preferably 30.0% or more, more preferably 35.0% or more, and the area of the crystal phase of CuO is the crystal phase of Cu ₂ O and Cu (OH) ₂ . It is more preferably 50.0% or more, which is equal to or more than the total area of.

Further, the surface layers 158 and 159 may contain a crystal phase other than the crystal phase of CuO, the crystal phase of Cu ₂ O, and the crystal phase of Cu (OH) ₂ .

Further, the surface layers 158 and 159 are formed on surfaces other than the surface to be joined to the core material layer 154 of the Cu layers 155 and 156, respectively. Specifically, the surface layer 158 is formed on the Z1 side surface and the side surface other than the Z2 side surface joined to the core material layer 154 of the Cu layer 155. Similarly, the surface layer 159 is formed on the Z2 side surface and the side surface other than the Z1 side surface joined to the core material layer 154 of the Cu layer 156. That is, the surface layers 158 and 159 are formed at positions not covered by the core material layers 154 of the Cu layers 155 and 156, respectively. The surface layers 158 and 159 may be formed at least on the surface to which the negative electrode active material layers 51 of the Cu layers 155 and 156 are bonded, and the clad material 157 (negative electrode current collector 150) may be formed in the thickness direction (Z). It does not have to be formed on the surface of the end faces (the left and right faces of the Cu layers 155 and 156 in FIG. 4) along the direction). Further, the thickness t12a of the surface layer 158 and the thickness t12b of the surface layer 159 are both 50 nm or less. As a result, since the thickness t12a of the surface layer 158 and the thickness t12b of the surface layer 159 are very small, the appearance of the negative electrode current collector 150 is the color of the crystal phase constituting the surface layers 158 and 159 (for example, black color of CuO). And Cu ₂ O reddish brown) is hardly observed, and the color of Cu or Cu alloy constituting Cu layers 155 and 156 (for example, reddish orange in the case of Cu) is observed. In FIG. 4, the thickness t12a of the surface layer 158 and the thickness t12b of the surface layer 159 are exaggerated for easy understanding.

Further, the surface 150a on the Z1 side located on the surface layer 158 side of the negative electrode current collector 150 (in FIG. 4, the portion where the negative electrode active material layer 51 of the surface layer 158 is fixed and the portion exposed to the outside) and the negative electrode current collector. The surface 150a on the Z2 side (the portion where the negative electrode active material layer 51 of the surface layer 159 is fixed and the portion exposed to the outside in FIG. 4) located on the surface layer 159 side of the body 150 are the Cu layers 155 and 156, respectively. Fine irregularities are formed by the roughening treatment. Specifically, the arithmetic mean roughness Ra on the surface 150a side based on JIS B 0601: 1994 is preferably 0.06 μm or more, and more preferably 0.075 μm or more. Further, the ten-point average roughness Rz on the surface 150a side based on JIS B 0601: 1994 is preferably 0.30 μm or more, and more preferably 0.35 μm or more. Further, the ten-point average roughness Rz on the surface 150a side is particularly preferably 0.40 μm or more.

Further, the ratio (t14: t13: t15) of the thickness t13 of the core material layer 154, the thickness t14 of the Cu layer 155, and the thickness t15 of the Cu layer 156 can be appropriately adjusted. For example, the thickness ratio (t14: t13: t15) is (1: 8) in order to ensure sufficient electrical conductivity in the Cu layers 155 and 156 and high mechanical strength in the core layer 154. It is preferably in the range of 1) to (3: 4: 3). That is, the thickness t13 of the core material layer 154 is preferably in the range of about 40% or more and 80% or less of the thickness t11 of the clad material 157 (negative electrode current collector 150), and the thickness t14 of the Cu layer 155 and the Cu layer 156. The thickness t15 of each is preferably in the range of about 10% or more and 30% or less of the thickness t11 of the clad material 157 (negative electrode current collector 150). Therefore, it is preferable that the thickness t13 of the core material layer 154 is larger than the thickness t14 of the Cu layer 155 and the thickness t15 of the Cu layer 156. In this case, in order to further improve the mechanical strength of the negative electrode current collector 150, it is preferable to increase the ratio of the thickness of the core material layer 154 having high mechanical strength. Further, in order to further improve the electric conductivity of the negative electrode current collector 150, it is preferable to increase the ratio of the thicknesses of the Cu layers 155 and 156 having a small volume resistivity.

Further, in order to enable easy rolling in clad rolling, it is preferable that the properties of the Cu layer 155 and the properties of the Cu layer 156 are brought close to each other. That is, it is preferable that the Cu layer 155 and the Cu layer 156 are made of Cu or a Cu alloy having the same composition, and the thickness t14 of the Cu layer 155 and the thickness t15 of the Cu layer 156 are substantially equal. The other configurations of the second embodiment are the same as the configurations of the first embodiment.

(Manufacturing method of negative electrode current collector)
Next, a method for manufacturing the negative electrode current collector 150 (material for a secondary battery negative electrode current collector) according to the second embodiment of the present invention will be briefly described.

First, a clad material 157 having a three-layer structure including a core material layer 154 formed through cold rolling (clad rolling) and diffusion annealing and a pair of Cu layers 155 and 156 bonded to the core material layer 154, respectively. prepare. Then, in the same manner as in the first embodiment, the clad material 157 (a pair of Cu layers 155 and 156) is roughened. In the roughening treatment, so-called soft etching is performed using a weakly acidic aqueous solution containing potassium sulfate. In this soft etching, the Cu layers 155 and 156 are selectively etched as compared with the core material layer 154. As a result, fine irregularities are formed on the surface other than the surface joined to the core material layer 154 of the pair of Cu layers 155 and 156.

Then, the clad material 157 that has been roughened is neutralized and then oxidized as a rust preventive treatment. In the rust-preventive treatment, as in the first embodiment, the surface other than the surface joined to the core material layer 154 of the pair of Cu layers 155 and 156 that have been roughened is treated with hydrogen peroxide solution. Oxidize. As a result, the surface of the _pair of Cu layers 155 and 156 other than the surface bonded to the core layer 154 contains the CuO crystal phase and the Cu2O crystal phase, and the area ratio of the CuO crystal phase (area ratio A1). ) Is 22.0% or more, the surface layers 158 and 159 are formed, respectively. From another viewpoint, the surface layers 158 and 159 having an area ratio (area ratio B1) of the crystal phase of CuO of 15.0% or more are formed, respectively. As a result, the negative electrode current collector 150 is manufactured.

Then, the negative electrode active material layer 51 is formed on the surface layers 158 and 159 of the produced negative electrode current collector 150. As a result, the negative electrode 105 is manufactured.

<Effect of the second embodiment>
In the second embodiment, the following effects can be obtained.

In the second embodiment, as described above, the area ratio (area ratio A1) of the crystal phase of CuO in the surface layers 158 and 159 is 22.0% or more, so that Cu is the same as in the first embodiment. Alternatively, it is possible to suppress the progress of oxidation to the region inside the surface layer 158 of the Cu layer 155 made of the Cu alloy and the surface layer 159 of the Cu layer 156. As a result, a sufficient rust preventive effect can be produced without forming a passivation film by chromate treatment. Therefore, a plate-like plate having a sufficient rust preventive effect can be obtained by a method other than the passivation film formation by chromate treatment. It is possible to provide a material for a secondary battery negative voltage collector (negative voltage collector 150) provided with a clad material 157. As a result, oxidation progresses in the atmosphere, and the contact resistance between the negative electrode current collector 150 made of the material for the negative electrode current collector of the secondary battery and the negative electrode active material layer 51 bonded to the negative electrode current collector 150. Can be suppressed from increasing.

Further, in the second embodiment, the core material layer 154 is preferably composed of a Ni, Ni alloy, Fe or Fe alloy. With this configuration, in the clad material 157 of the core material layer 154 and the Cu layers 155 and 156, the core material layer 154 having a mechanical strength higher than that of the Cu layers 155 and 156 can be used. This makes it possible to reliably resist the stress caused by the expansion and contraction of the negative electrode active material arranged on the negative electrode current collector 150. The other effects of the second embodiment are the same as those of the first embodiment.

[Example]
Next, an experiment (Example) conducted to confirm the effect of the present invention will be described. In the example of the present invention, a plurality of materials for the negative electrode current collector of the secondary battery were produced under different conditions of the rust preventive treatment (oxidation treatment). Then, surface layer analysis, corrosion test, surface roughness measurement, and peeling test were performed on the produced materials for the negative electrode current collector of the secondary battery.

(First Example)
In the first embodiment, as the material, the plate-shaped clad material 157 having a three-layer structure according to the second embodiment shown in FIG. 4 was used. At this time, a Ni—Nb alloy containing 5% by mass of Nb was used as the core material layer 154. In addition, oxygen-free copper (C1020, JIS standard) was used as the Cu layers 155 and 156. The thickness t11 of the clad material 157 was set to 10 μm. Further, the ratio (t14: t13: t15) of the thickness t14 of the Cu layer 155, the thickness t13 of the core material layer 154, and the thickness t15 of the Cu layer 156 was set to 1: 3: 1.

Then, the clad material 157 is subjected to a test material 1 which is not subjected to roughening treatment and rust prevention treatment (oxidation treatment), a test material 2 which is only roughened and is not subjected to rust prevention treatment, and a roughening treatment and Test materials 3 to 7 to be subjected to rust prevention treatment were prepared. In the roughening treatment, so-called soft etching was performed using a weakly acidic aqueous solution containing 5% of potassium sulfate at a mass percent concentration and maintained at a temperature of 30 ° C.

Further, in the rust prevention treatment, the roughened clad material 157 was subjected to the roughening treatment using hydrogen peroxide solution to form the Cu layer 155 of the clad material 157 and the core material layer 154 of the 156. The surfaces other than the surfaces to be joined were oxidized. Specifically, in the test material 3, the clad material 157 was immersed in hydrogen peroxide water containing 0.1% of H ₂ O ₂ (hydrogen peroxide) at a mass percent concentration for 15 seconds. At this time, the hydrogen peroxide solution was kept at a temperature condition of 20 ° C. The test material 4 had the same conditions as the test material 3 except that a hydrogen peroxide solution containing 0.5% of H ₂ O ₂ in a mass percent concentration was used. The test material 5 had the same conditions as the test material 3 except that a hydrogen peroxide solution containing 1.0% of H ₂ O ₂ in a mass percent concentration was used.

In the test material 6, the test material 5 was subjected to the roughening treatment in twice the time as in the test materials 2 to 5, and the hydrogen peroxide solution maintained at the temperature condition of 40 ° C. was used. The conditions were the same as above. The test material 7 had the same conditions as the test material 6 except that a hydrogen peroxide solution containing 5.0% of H ₂ O ₂ in a mass percent concentration was used. Table 1 shows the roughening treatment conditions and the rust prevention conditions. The concentration shown in Table 1 is a mass percent concentration.

(Surface layer analysis)
Then, in each of the test materials 1 to 7, the crystal phase of the surface layer on the surface excluding the end face along the thickness direction (Z direction) of the test material other than the surface bonded to the core material layer 154 of the Cu layers 155 and 156 is obtained. , XPS (ESCA) analysis. Then, the area ratio of the crystal phase of each CuO of the test materials 1 to 7 (area ratio A1, area ratio B1), the area ratio of the crystal phase of Cu _2O (area ratio A2, area ratio B2), and Cu (OH). ) The area ratio of the crystal phase of ₂ (area ratio A3, area ratio B3) was obtained. Specifically, as described in the first embodiment, a narrow scan spectrum of Cu2p was obtained using XPS (ESCA). After that, from the spectrum around the peak of the bond energy of Cu 2p _3/2 , the peak of the crystal phase of CuO (933.6 eV), the peak of the crystal phase of Cu ₂ O (932.5 eV), and the crystal of Cu (OH) ₂ The peak of the phase (935.1 eV) was separated. Then, the area ratios (area ratios A1 to A3 and area ratios B1 to B3) of _{each of the crystal phases of CuO, Cu2O, and Cu (OH) 2 were} obtained. As an example, the spectra of test material 2 and test material 7 are shown in FIGS. 5 and 6, respectively. In FIGS. 5 and 6, the horizontal axis is the bond energy (eV), the vertical axis is the count number per second (c / s), and the measured spectra, CuO, Cu ₂ O, and Cu (OH) are used. ) The spectra corresponding to each crystal phase of ₂ and their composite spectra are shown.

(Corrosion test)
In addition, corrosion tests were performed on each of the test materials 1 to 7. Specifically, each of the test materials 1 to 7 was placed in a constant temperature and humidity chamber maintained at a temperature of 60 ° C. and a relative humidity of 85%, and held for 40 hours. Then, by observing the degree of corrosion of the surface excluding the end surface along the thickness direction (Z direction) of the test material other than the surface bonded to the Cu layer 155 and the core material layer 154 of the test materials 1 to 156, the degree of corrosion is prevented. Rust evaluation was performed.

The rust prevention evaluation was carried out by visually observing the change in the color tone of the surface of the test material. Specifically, the surface color (red-orange) of the Cu material (oxygen-free copper) that has not been roughened and rust-proofed, and the Cu material that has been roughened and rust-proofed with hydrogen peroxide solution. The surface color (pink) of (anoxic-free copper) was used as the evaluation reference color, and the color of the CuO crystal phase (black) and the color of the Cu _2O crystal phase (reddish brown) were focused on. By visually observing the test material, if there is no substantial change in the color tone equivalent to the evaluation standard color, it is judged that substantial corrosion (oxidation) has not progressed, and a higher rust preventive effect than desired is obtained. A circle (○) is added to indicate that it will be played. In addition, if a slight change is observed in the shade of reddish brown from the evaluation standard color, it is judged that corrosion (oxidation) has progressed slightly but there is no practical effect, and the desired rust preventive effect is exhibited. A triangle mark (△) was added. In addition, if there is a clear change in the shade of black-brown from the evaluation standard color, it is judged that corrosion (oxidation) is progressing, and a cross mark (x) is added as the color does not meet the desired rust prevention effect. .. In addition, if there is a significant change in the shade of black-brown from the evaluation standard color, it is judged that corrosion (oxidation) has progressed remarkably, and it is judged that the rust preventive effect is not exhibited, and a double cross mark (XX). ) Was added.

Table 2 shows the results of surface layer analysis and corrosion test.

As a result of the surface layer analysis and the corrosion test, the area ratio A1 of the crystal phase of CuO in the surface layer subjected to the roughening treatment and the rust prevention treatment is 22.0% or more with respect to the area ratio A1 in the surface layer. It was confirmed that the desired rust preventive effect was exhibited in 4 (55.1%) to 7 (90.5%) of the test material. In particular, it was confirmed that the test material 6 (74.8%) and the test material 7 (90.5%) having an area ratio A1 of the crystal phase of CuO of 62.0% or more exert a high rust preventive effect. .. On the other hand, the test material 3 (21.9%) in which the area ratio A1 of the crystal phase of CuO in the surface layer subjected to the roughening treatment and the rust prevention treatment is less than 22.0% satisfies the desired rust prevention effect. I was able to confirm that there was no such thing. In particular, it was confirmed that the test material 2 (9.9%), which has a small area ratio A1 of the crystal phase of CuO, does not exert a rust preventive effect.

Further, regarding the area ratio B1 in the surface layer, the test material 4 (32.9%) to the test material 4 (32.9%) in which the area ratio B1 of the crystal phase of CuO in the surface layer subjected to the roughening treatment and the rust prevention treatment is 15.0% or more. It was confirmed that the material 7 (49.4%) had a desired rust preventive effect. In particular, it was confirmed that the test material 6 (46.4%) and the test material 7 (49.4%) in which the area ratio B1 of the crystal phase of CuO was 39.0% or more exerted a high rust preventive effect. .. On the other hand, the test material 3 (14.9%) in which the area ratio B1 of the crystal phase of CuO in the surface layer subjected to the roughening treatment and the rust prevention treatment is less than 15.0% satisfies the desired rust prevention effect. I was able to confirm that there was no such thing. In particular, it was confirmed that the test material 2 (8.3%) having a small area ratio B1 of the crystal phase of CuO did not exert a rust preventive effect.

Further, the area ratio A1 of the crystal phase of CuO in the surface layer is set to 22.0% or more, preferably the area ratio B1 of the crystal phase of CuO in the surface layer is set to 15.0% or more, and the test materials 4 to 7 are used. In order to obtain the above-mentioned rust-preventive effect, in the rust-preventive treatment, a hydrogen peroxide solution containing 0.5% or more of H ₂ O ₂ at a mass percent concentration is used under temperature conditions of room temperature (20 ° C.) or higher. It was found that it was necessary to perform the test for a predetermined time (15 seconds) or longer.

The test material 1 that had not been roughened or rust-proofed exhibited a rust-preventive effect. This is because the test material 1 does not undergo the strong degreasing that is generally performed in the roughening treatment and the rust prevention treatment, so that the lubricating oil at the time of rolling remains on the surface, and the lubricating oil remaining on the surface causes it. It is considered that the progress of corrosion (oxidation) was suppressed.

Further, from the results of the test materials 3 to 5, it is possible to increase the area ratio A1 and the area ratio B1 of the crystal phase of CuO in the surface layer by increasing the concentration of hydrogen peroxide during the rust prevention treatment. It could be confirmed. Furthermore, from the results of the test materials 5 and 6, it was confirmed that the area ratio A1 and the area ratio B1 of the crystal phase of CuO in the surface layer can be further increased by increasing the temperature during the rust prevention treatment. By lengthening the test time, the area ratio A1 of the crystal phase of CuO in the surface layer is 22 even if the concentration is low to some extent (for example, the concentration is 0.5% at the mass percent concentration of the test material 3). Although it is considered possible to make the area ratio B1 of the crystal phase of CuO in the surface layer 15.0% or more, it is considered possible to make it 0.0% or more, but the negative voltage collection of the secondary battery is considered to be possible. It is not preferable to increase the time (tact time) required for manufacturing the body material.

Further, with respect to the area ratios A1 and A2 and the area ratios B1 and B2 in the surface layer, the test materials 4 to 4 in which the area ratio A1 (B1) of the crystal phase of CuO is larger than the area ratio A2 (B2) of the crystal phase of Cu _2O . In No. 7, a higher rust-preventing effect is exhibited as compared with the test materials 2 and 3 in which the area ratio A1 (B1) of the crystal phase of CuO in the surface layer is less than the area ratio A2 (B2) of the crystal phase of Cu _2O . I was able to confirm that. Regarding the area ratios B1 and B3 in the surface layer, in the test materials 5 to 7 in which the area ratio B1 of the crystal phase of CuO is larger than the area ratio B3 of the crystal phase of Cu (OH) ₂ , the crystal phase of CuO in the surface layer It was confirmed that the area ratio B1 of C2O was less than the area ratio B3 of the crystal phase of Cu _2O , and that the test materials 2 and 3 had a higher rust-preventive effect.

Further, it is considered that Cu (OH) ₂ can be changed to CuO by heat when the negative electrode active material is arranged on the material for the negative electrode current collector of the secondary battery via the binder. Therefore, it is considered that the area ratio of the crystal phase of CuO becomes larger after the negative electrode current collector is formed, and the rust preventive effect is enhanced.

(Measurement of surface roughness)
Next, in each of the test materials 1 to 7, the surface roughness is measured on the surface excluding the end face along the thickness direction of the test material other than the surface bonded to the core material layer 154 of the Cu layers 155 and 156. Measured using a machine. As the surface roughness, the arithmetic average roughness Ra and the ten-point average roughness Rz based on JIS B 0601: 1994 were measured. Using a surface roughness measuring device (Surfcom 480A, stylus radius 2 μm, scanning speed 0.3 mm / sec) of Tokyo Seimitsu Co., Ltd., the cutoff value is 0.25 mm, and the scanning distance (measurement length) is 1. It was set to .25 mm.

(Peeling test)
Further, in each of the test materials 1 to 7, the adhesion to the binder is measured by targeting the surface to which the negative electrode active material layer 51 other than the surface bonded to the core material layer 154 of the Cu layers 155 and 156 is bonded. bottom. Specifically, as shown in FIG. 7, an acrylic resin as a binder (resin material) is arranged on a surface other than the surface of each of the test materials 1 to 7 to be joined to the core material layer 154 of the Cu layer 155. .. Specifically, a polyacrylic acid aqueous solution is placed on the surface on the Z2 side to be joined to the core material layer 154 of each Cu layer 155 of the test materials 1 to 7 and the surface on the Z1 side opposite in the thickness direction (Z direction). Was applied to a thickness of 200 μm using a coating device. Then, the test materials 1 to 7 after coating were dried and cured by holding them in a dryer set to a temperature condition of 150 ° C. for 5 minutes. As a result, an acrylic resin layer having a thickness of 5 μm was formed on the surface on the Z1 side other than the surface to be joined to the core material layer 154 of the Cu layer 155.

Then, a resin tape was attached on the surface of the acrylic resin layer. Then, the resin tape was pulled vertically using a tensile tester (not shown), that is, in the thickness direction (Z direction) of the clad material 157. Then, the load applied by the tensile tester when the test materials 1 to 7 are peeled off is acquired, and the load (N) is divided by the width L (mm) of the resin tape to obtain the test material 1 The adhesion strength (N / mm) in ~ 7 was determined.

Table 3 shows the results of the surface roughness measurement and the peeling test. The "foil / resin" shown in Table 3 means between the clad material and the acrylic resin layer, and the "resin / tape" means between the acrylic resin layer and the resin tape.

As a result of the surface roughness measurement and the peeling test, in the test material 1 which was not subjected to the roughening treatment, peeling occurred between the clad material and the acrylic resin layer. The adhesion strength was also small, 0.03 N / mm. This is because the test material 1 was not roughened, so that the arithmetic average roughness Ra and the ten-point average roughness Rz were both small on the surface layer side where the acrylic resin layer of the clad material was arranged. It is believed that there is. On the other hand, in the test materials 2 to 7 subjected to the roughening treatment, peeling occurred between the acrylic resin layer and the resin tape. That is, the adhesion strength between the clad material and the acrylic resin layer was larger than the adhesion strength between the acrylic resin layer and the resin tape (about 0.24 N / mm). This is because the arithmetic mean roughness Ra and the ten-point average roughness Rz on the surface on which the acrylic resin layer of the clad material is arranged were sufficiently large due to the roughening treatment of the test materials 2 to 7. it is conceivable that. In particular, in the test materials 2 to 7 having a ten-point average roughness Rz of 0.30 μm or more on the surface layer side of the clad material, it is considered that the adhesion strength between the clad material and the acrylic resin layer is sufficiently high. Further, it is considered that the adhesion strength between the clad material and the acrylic resin layer is sufficiently higher in the test materials 4 to 7 in which the ten-point average roughness Rz on the surface layer side of the clad material is 0.35 μm or more.

(Second Example)
In the second embodiment, the same clad material 157 as in the first embodiment was used except that SUS631 was used as the core material layer 154. Then, the test material 11 which is not roughened and rust-proofed (oxidized) and the test materials 12 to 14 which are roughened and rust-proofed are prepared for the clad material 157. In the roughening treatment, soft etching was performed under the same conditions as those of the test materials 1 to 5 of the first embodiment.

Further, in the rust prevention treatment, the Cu layer of the clad material 157 that has been roughened by using hydrogen peroxide solution with respect to the clad material 157 that has been roughened, as in the first embodiment. Surfaces other than the surface bonded to the core layer 154 of 155 and 156 were oxidized. Specifically, in the test material 12, the clad material 157 was immersed in hydrogen peroxide water containing 1.0% of H ₂ O ₂ (hydrogen peroxide) at a mass percent concentration for 15 seconds. At this time, the hydrogen peroxide solution was kept at a temperature condition of 15 ° C. The test material 12 had the same conditions as the test material 11 except that a hydrogen peroxide solution containing 3.0% of H ₂ O ₂ in a mass percent concentration was used. The test material 14 had the same conditions as the test material 11 except that a hydrogen peroxide solution containing 5.0% of H ₂ O ₂ in a mass percent concentration was used. Table 4 shows the roughening treatment conditions and the rust prevention conditions. The concentration shown in Table 4 is a mass percent concentration.

Then, the surface layer analysis and the corrosion test were performed in the same manner as in the first embodiment. The results of surface layer analysis and corrosion test are shown in Table 5.

As a result of the surface layer analysis and the corrosion test, the area ratio A1 of the crystal phase of CuO in the surface layer subjected to the roughening treatment and the rust prevention treatment is 22.0% or more with respect to the area ratio A1 in the surface layer. It was confirmed that the desired rust preventive effect was exhibited in 12 (22.3%) to 14 (64.8%) of the test material. In particular, the test material 14 (60.0% or more) in which the area ratio A1 of the crystal phase of CuO is 30.0% or more is 30.0% or more as compared with the test material 13 (23.8%) in which the area ratio A1 is not 25.0% or more. It was confirmed that a high rust preventive effect was exhibited at 64.8%).

Further, regarding the area ratio B1 in the surface layer, the test material 12 (19.6%) to the test material 12 (19.6%) in which the area ratio B1 of the crystal phase of CuO in the surface layer subjected to the roughening treatment and the rust prevention treatment is 15.0% or more. It was confirmed that the material 14 (43.4%) had a desired rust preventive effect. In particular, it was confirmed that the test material 14 (43.4% of 40.0% or more) having an area ratio B1 of the crystal phase of CuO of 21.0% or more exerts a high rust preventive effect.

The test material 11 which had not been roughened or rust-proofed exhibited a rust-preventive effect. This is because, as in the first embodiment, the test material 11 does not undergo the strong degreasing generally performed in the roughening treatment and the rust prevention treatment, so that the lubricating oil during rolling remains on the surface. It is considered that the progress of corrosion (oxidation) was suppressed by the lubricating oil remaining on the surface.

Further, from the results of the test materials 12 to 14, the area ratio A1 and the area ratio of the crystal phase of CuO in the surface layer were increased by increasing the concentration of hydrogen peroxide during the rust prevention treatment, as in the first embodiment. It was confirmed that B1 can be made larger.

Further, with respect to the area ratios A1 and 2 and the area ratios B1 and B2 in the surface layer, in the test material 14, the area ratio A1 (B1) of the crystal phase of CuO is larger than the area ratio A2 (B2) of the crystal phase of Cu _2O . Compared with the test materials 12 and 13 in which the area ratio A1 (B1) of the crystal phase of CuO in the surface layer is less than the area ratio A2 (B2) of the crystal phase of Cu _2O , a higher rust prevention effect can be obtained. It could be confirmed. Further, regarding the area ratios B1 and B3 in the surface layer, in the test material 14 in which the area ratio B1 of the crystal phase of CuO is larger than the area ratio B3 of the crystal phase of Cu (OH) ₂ , the area of the crystal phase of CuO in the surface layer It was confirmed that a higher rust-preventing effect was exhibited as compared with the test materials 12 and 13 in which the ratio B1 was less than the area ratio B3 of the crystal phase of Cu ₂ O.

Moreover, the surface roughness measurement and the peeling test were carried out in the same manner as in the 1st Example. The results of the surface roughness measurement and the peeling test are shown in Table 6. The "foil / resin" shown in Table 6 means between the clad material and the acrylic resin layer, and the "resin / tape" means between the acrylic resin layer and the resin tape.

As a result of the surface roughness measurement and the peeling test, as in the first embodiment, in the test material 11 which was not roughened, peeling occurred between the clad material and the acrylic resin layer. The adhesion strength was also small, 0.02 N / mm. On the other hand, in the roughened test materials 12 to 14, peeling occurred between the acrylic resin layer and the resin tape. That is, the adhesion strength between the clad material and the acrylic resin layer was larger than the adhesion strength between the acrylic resin layer and the resin tape (about 0.24 N / mm). In particular, in the test materials 12 to 14 having a ten-point average roughness Rz of 0.35 μm or more on the surface layer side of the clad material, it is considered that the adhesion strength between the clad material and the acrylic resin layer is sufficiently high.

From the results of the first and second embodiments, a clad material having an area ratio A1 of the crystal phase of CuO in the surface layer of 22.0% or more, regardless of the material of the core material layer, has a sufficient rust preventive effect. It was confirmed that it plays. Further, it was confirmed that a clad material having an area ratio B1 of the crystal phase of CuO in the surface layer of 15.0% or more, regardless of the material of the core material layer, exerts a sufficient rust preventive effect. As a result, even in the secondary battery negative electrode current collector material composed of the Cu material 52 of the first embodiment having no core material layer, the area ratio A1 of the crystal phase of CuO in the surface layer is 22. If it is 0% or more, it can be estimated that a sufficient rust preventive effect is exhibited. Further, even in the material for a secondary battery negative electrode current collector composed of the Cu material 52 of the first embodiment having no core material layer, the area ratio B1 of the crystal phase of CuO in the surface layer is 15.0. If it is% or more, it can be inferred that a sufficient rust preventive effect is exhibited.

Further, in the first embodiment, a Ni—Nb alloy was used as the core material layer, and in the second embodiment, SUS631 was used as the core material layer, but the core material layer was other than the Ni and Ni—Nb alloys. Even if an Fe alloy other than Ni alloy, Fe or SUS631 is used, if the area ratio A1 of the crystal phase of CuO in the surface layer of the secondary battery negative electrode current collector is 22.0% or more, a sufficient rust preventive effect is obtained. Can be inferred to play. Further, even if a Ni alloy other than Ni and Ni—Nb alloys and an Fe alloy other than Fe or SUS631 are used as the core material layer, the area ratio B1 of the crystal phase of CuO in the surface layer of the material for the negative electrode current collector of the secondary battery is B1. If it is 15.0% or more, it can be estimated that a sufficient rust preventive effect is exhibited.

Further, although oxygen-free copper is used as the Cu layer in the first and second embodiments, even if Cu or a Cu alloy other than oxygen-free copper is used, CuO in the surface layer of the secondary battery negative electrode current collector material is used. If the area ratio A1 of the crystal phase of the above is 22.0% or more, it can be presumed that a sufficient rust preventive effect is exhibited. Even if Cu or a Cu alloy other than oxygen-free copper is used, if the area ratio B1 of the crystal phase of CuO in the surface layer of the negative electrode current collector of the secondary battery is 15.0% or more, sufficient rust prevention is sufficient. It can be inferred that it will be effective.

Further, in the first and second embodiments, although the acrylic resin is used as the binder, other resin materials (for example, polyimide resin or fluororesin) can be used as the clad of the present invention in the same manner as the acrylic resin. It is considered that the adhesion strength with the material is increased. In particular, since the polyimide resin tends to have a higher adhesion strength with the clad material than the acrylic resin, it is considered that the adhesion strength with the clad material of the present invention is sufficiently high.

[Modification example]
It should be noted that the embodiments and examples disclosed this time are exemplary in all respects and are not considered to be restrictive. The scope of the present invention is shown by the scope of claims rather than the description of the embodiments and examples described above, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims.

For example, in the above first embodiment, an example is shown in which the material for the negative electrode current collector of the secondary battery is composed of the Cu material 52 on which the surface layer 53 is formed, but the present invention is not limited to this. In the present invention, the material for the negative electrode current collector of the secondary battery may include a layer (plating layer or the like) other than the Cu material.

Further, in the second embodiment, an example is shown in which the material for the negative electrode current collector of the secondary battery is composed of the clad material 157 having a three-layer structure in which the surface layers 158 and 159 are formed. Not limited. For example, the material for the negative electrode current collector of the secondary battery may be composed of a clad material having a two-layer structure composed of only one core material layer and one Cu layer having a surface layer. Further, it may be composed of a clad material including a core material layer and a layer other than the Cu layer having a surface layer.

Further, in the first and second embodiments, examples of performing soft etching using potassium sulfate as a roughening treatment are shown, but the present invention is not limited to this. In the present invention, if the surface can be roughened, the roughening treatment may be performed by a method other than soft etching using potassium sulfate. Since the negative electrode current collector of the secondary battery is sufficiently small in thickness, the thickness of the Cu material and the Cu layer tends to be excessively small when an etching solution that rapidly corrodes the Cu material and the Cu layer is used. Therefore, in the roughening treatment, it is preferable not to use an etching solution that rapidly corrodes the Cu material and the Cu layer.

Further, in the first embodiment, an example is shown in which the surface layer 53 is formed so as to cover substantially the entire surface of the Cu material 52, but the present invention is not limited to this. In the present invention, the surface layer does not have to be formed over substantially the entire surface of the Cu material. For example, the surface layer may be formed only on both sides in the thickness direction of the Cu material, which tends to cause inconveniences such as deterioration of weldability due to the generation (oxidation) of rust.

Further, in the second embodiment, in the clad material 157, the surface layer 158 is formed on the Z1 side surface (the surface opposite to the surface to be joined) and the side surface of the Cu layer 155, and the surface layer 159 is formed. Although examples are shown which are formed on the Z2 side surface (the surface opposite to the surface to be joined) and the side surface of the Cu layer 156, the present invention is not limited to this. In the present invention, in the clad material, the surface layer does not have to be formed on the side surface of the Cu layer.

Further, in the first and second embodiments, the example in which the material for the negative electrode current collector of the secondary battery is used for the cylindrical lithium ion secondary battery (battery 100) is shown, but the present invention is not limited to this. .. In the present invention, the material for the negative electrode current collector of the secondary battery may be used for a secondary battery other than the lithium ion secondary battery. Further, instead of the can type using the cylindrical housing 1 as shown in FIG. 1, a material for a secondary battery negative electrode current collector may be used for, for example, a laminated type secondary battery.

52 Cu material 53, 158, 159 Surface layer 154 Core material layer 155, 156 Cu layer 157 Clad material

Claims (5)

It is equipped with a plate-shaped Cu material composed of Cu or Cu alloy.
The Cu material has a surface layer containing at least a CuO crystal phase, a Cu2O crystal phase , and a Cu (OH) ₂ crystal phase _on the plate surface, and the area of the CuO crystal phase in the surface layer / (CuO). The area ratio (percentage) obtained by (the area of the crystal phase + the area of the crystal phase of Cu ₂ O) is 55.1% or more, and the area of the crystal phase of CuO in the surface layer / (the area of the crystal phase of CuO + Cu). The area ratio (percentage) obtained by the area of the crystal phase of 2O + the crystal phase of Cu (OH) 2) is 15.0% or more, which is _a material _for a secondary battery negative electrode current collector. A plate-shaped clad material including a core material layer made of metal and a Cu layer joined to the core material layer and made of Cu or a Cu alloy.
The clad material contains at least a CuO crystal phase, a Cu2O crystal phase , and a Cu (OH) ₂ crystal phase _on a surface of the Cu layer opposite to the surface bonded to the core material layer in the thickness direction. The area ratio (percentage) obtained by having a surface layer and the area of the crystal phase of CuO in the surface layer / (the area of the crystal phase of CuO + the area of the crystal phase of Cu _2O ) is 55.1% or more . The area ratio (percentage) obtained by the area of the crystal phase of CuO in the surface layer / (the area of the crystal phase of CuO + the area of the crystal phase of Cu 2O ₊ the crystal phase of Cu (OH) ₂ ) is 15.0% or more. A material for a secondary battery negative electrode current collector. The material for a secondary battery negative electrode current collector according to claim 2, wherein the core material layer is made of Ni, Ni alloy, Fe or Fe alloy. The material for a secondary battery negative electrode current collector according to any one of claims 1 to 3 , wherein the ten-point average roughness on the surface layer side is 0.30 μm or more. The material for a negative electrode current collector for a secondary battery according to claim 4 , wherein a resin material for adhering a negative electrode active material is provided on the surface.

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