CN109390589B - Material for negative electrode collector of secondary battery - Google Patents

Material for negative electrode collector of secondary battery Download PDF

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Publication number
CN109390589B
CN109390589B CN201810869273.8A CN201810869273A CN109390589B CN 109390589 B CN109390589 B CN 109390589B CN 201810869273 A CN201810869273 A CN 201810869273A CN 109390589 B CN109390589 B CN 109390589B
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crystal phase
negative electrode
layer
area
cuo
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CN109390589A (en
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井上良二
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Bomeilicheng Co ltd
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Bomeilicheng Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Composite Materials (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Cell Electrode Carriers And Collectors (AREA)

Abstract

The material for a secondary battery negative electrode collector comprises a plate-like Cu material composed of Cu or a Cu alloy, wherein the Cu material has a CuO crystal phase and Cu on at least the plate surface 2 A surface layer of O crystal phase, the surface layer being composed of the area of CuO crystal phase/(the area of CuO crystal phase+Cu 2 Area of O crystal phase) is 22.0% or more.

Description

Material for negative electrode collector of secondary battery
Technical Field
The present application relates to a material for a secondary battery negative electrode collector, and relates to a material for a secondary battery negative electrode collector including a layer (material) composed of Cu (copper) or a Cu alloy.
Background
Conventionally, a secondary battery negative electrode current collector material including a layer (material) composed of Cu or a Cu alloy is known. Such a secondary battery negative electrode current collector material is disclosed in, for example, japanese patent application laid-open No. 2003-132894.
Japanese patent application laid-open No. 2003-132894 discloses that the alloy is composed of Cu or a Cu alloy and the surface is covered with Cu 2 An O-covered negative electrode collector (material for secondary battery negative electrode collector).
However, the present inventors have found that the negative electrode current collector described in japanese unexamined patent publication No. 2003-132894 has the following problems: the rust prevention is insufficient, oxidation progresses in the atmosphere, contact resistance between the negative electrode current collector and the active material increases, and resistance in the battery cell using the negative electrode current collector also increases.
Among them, it is generally considered that chromate treatment is performed for rust prevention: a material for a negative electrode collector of a secondary battery, which is composed of Cu or a Cu alloy, is immersed in a solution containing 6-valent Cr (chromium), whereby a passivation film is formed on the surface. However, since 6 valent Cr contained in the treated solution increases environmental load, it is not preferable to conduct chromate treatment from the viewpoint of environmental load.
Disclosure of Invention
The present application has been made to solve the above-described problems, and an object of the present application is to provide a material for a secondary battery negative electrode collector having a sufficient rust-preventing effect by a method other than forming a passivation film by chromate treatment.
The present inventors have conducted intensive studies in order to solve the above problems, and as a result, found that: a Cu material (Cu layer) having a surface layer containing CuO (copper (II) oxide) at a predetermined ratio or moreCrystalline phases other than Cu 2 O (cuprous oxide (I)), thereby suppressing progress of oxidation and producing an anti-rust effect. The present application has been completed based on such findings.
That is, the material for a secondary battery negative electrode collector according to the first aspect of the present application comprises a plate-like Cu material composed of Cu or a Cu alloy, the Cu material having a CuO crystal phase and Cu on at least the plate surface 2 A surface layer of O crystal phase, the surface layer being composed of the area of CuO crystal phase/(the area of CuO crystal phase+Cu 2 Area of O crystal phase) is 22.0% or more. Here, the "area of CuO crystal phase" refers to Cu2p when a narrow scanning spectrum of Cu2p is obtained by X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy) 3/2 Based on CuO and Cu in the peaks of (2) 2 Area of the CuO crystal phase relative to the CuO crystal phase and Cu of the peak of O 2 The ratio (area ratio) of the total area of the O crystal phases. Also, so-called "Cu 2 The area "of O crystal phase means the above CuO and Cu based on XPS 2 Cu as determined by the peak of O 2 Area of O crystal phase relative to CuO crystal phase and Cu 2 The ratio (area ratio) of the total area of the O crystal phases. The term "Cu alloy" refers to an alloy containing 50 mass% or more of Cu (copper).
In the material for a secondary battery negative electrode current collector according to the first aspect of the present invention, as described above, by providing at least the plate surface of the plate-like Cu material with a surface layer containing CuO crystal phase in an area ratio of 22.0% or more, progress of oxidation in a region of the Cu material composed of Cu or Cu alloy on the inner side of the surface layer can be suppressed. Thus, a sufficient rust preventing effect can be produced even if the passivation film is not formed by the chromate treatment, and therefore, a material for a secondary battery negative electrode current collector having a sufficient rust preventing effect can be provided by a method other than the formation of the passivation film by the chromate treatment. As a result, the progress of oxidation in the atmosphere can be suppressed, and an increase in contact resistance between the negative electrode current collector made of the material for the negative electrode current collector of the secondary battery including the plate-like Cu material and the negative electrode active material layer bonded to the surface of the negative electrode current collector (plate-like Cu material plate surface) can be suppressed. Further, it has been confirmed from experiments described below that the progress of oxidation in the region of the Cu material further inside than the surface layer can be suppressed by the CuO crystal phase.
The secondary battery negative electrode collector material according to the second aspect of the present invention comprises a plate-shaped clad material comprising a core layer made of a metal and a Cu layer joined to the core layer and made of Cu or a Cu alloy, wherein the clad material has a surface of at least one side of the Cu layer opposite to a surface to be joined to the core layer in the thickness direction, the surface comprising a CuO crystal phase and Cu 2 A surface layer of O crystal phase, the surface layer being composed of the area of CuO crystal phase/(the area of CuO crystal phase+Cu 2 Area of O crystal phase) is 22.0% or more.
In the secondary battery negative electrode collector material according to the second aspect of the present invention, even when applied to the clad material of the core layer and the Cu layer, the surface layer containing CuO crystal phase in an area ratio of 22.0% or more is provided on at least the surface of the Cu layer on the opposite side in the thickness direction from the surface where the core layer is bonded, as in the secondary battery negative electrode collector material according to the first aspect described above, whereby progress of oxidation can be suppressed in the region inside the surface layer of the Cu layer composed of Cu or Cu alloy. Thus, a sufficient rust preventing effect can be produced even if the passivation film is not formed by the chromate treatment, and therefore, a secondary battery negative electrode current collector material containing a clad material having a sufficient rust preventing effect can be provided by a method other than the formation of the passivation film by the chromate treatment.
In the secondary battery negative electrode collector material according to the second aspect, the core layer is preferably made of Ni, a Ni alloy, fe or an Fe alloy. With this structure, a core layer having a mechanical strength greater than that of the Cu layer can be used as the clad material for the core layer and the Cu layer. In this way, for example, when the material for the negative electrode collector of the secondary battery is used as the negative electrode collector of the lithium ion secondary battery, the stress caused by expansion and contraction of the negative electrode active material disposed on the negative electrode collector can be reliably counteracted. As a result, occurrence of defects such as wrinkles and breakage in the negative electrode current collector can be suppressed. The term "Ni alloy" and "Fe alloy" refer to alloys containing 50 mass% or more of Ni (nickel) and Fe (iron), respectively.
In the secondary battery anode current collector material according to the first or second aspect, it is preferable that the surface layer has a crystal phase of CuO/(crystal phase of cuo+cu) 2 Area of O crystal phase) is 30.0% or more. With this structure, since the area of the CuO crystal phase in the surface layer increases, the progress of oxidation can be reliably suppressed in the area of the Cu material further inside than the surface layer by only the amount by which the area of the CuO crystal phase increases.
In the secondary battery negative electrode current collector material according to the first or second aspect, the surface layer preferably further contains Cu (OH) 2 The crystal phase, the area of the CuO crystal phase/(the area of the CuO crystal phase+cu) in the surface layer 2 Area of O Crystal phase+Cu (OH) 2 Area of crystal phase) is 15.0% or more. If so constructed, the composition contains not only CuO crystal phase and Cu 2 O crystal phase and further contains Cu (OH) 2 By having a CuO crystal phase in the surface layer in an area ratio of 15.0% or more in the surface layer of the crystal phase, progress of oxidation can be suppressed in a region of the Cu material further inside than the surface layer. And Cu (OH) 2 The (copper hydroxide) is relatively unstable, and Cu (OH) can be caused by, for example, heat generated when the negative electrode active material is bonded to the negative electrode current collector material of the secondary battery via the resin material 2 And is changed to CuO. That is, cu (OH) is also contained through the surface layer 2 The area ratio of the CuO crystal phase can be further increased by heating or the like.
In the secondary battery negative electrode current collector material according to the first or second aspect, the surface layer preferably has a ten-point average roughness of 0.30 μm or more. With this structure, the negative electrode active material can be reliably disposed on the surface layer roughened to some extent to form irregularities.
In this case, a resin material for adhering the anode active material is preferably provided on the surface. With this configuration, the resin material can be reliably adhered to the surface layer due to the irregularities formed on the surface layer and the increase in the surface area of the surface layer. Thus, the negative electrode active material can be reliably bonded to the surface of the secondary battery negative electrode current collector material by the resin material.
Drawings
Fig. 1 is a schematic cross-sectional perspective view showing a lithium ion secondary battery including a negative electrode using a secondary battery negative electrode current collector material according to a first embodiment of the present invention.
Fig. 2 is a cross-sectional view showing a negative electrode using a secondary battery negative electrode current collector material according to the first embodiment of the present invention.
Fig. 3 is an enlarged cross-sectional view showing the periphery of the surface layer of the material for a negative electrode collector (negative electrode collector) of a secondary battery according to the first embodiment of the present invention.
Fig. 4 is a cross-sectional view showing a negative electrode using a secondary battery negative electrode current collector material according to a second embodiment of the present invention.
Fig. 5 is a graph showing the spectrum of the test material 2 in the surface layer analysis performed to confirm the effect of the present invention.
Fig. 6 is a graph showing the spectrum of the test material 7 in the surface layer analysis performed to confirm the effect of the present invention.
Fig. 7 is a schematic perspective view for explaining a peeling test performed to confirm the effect of the present invention.
Detailed Description
Embodiments of the present invention will be described below with reference to the drawings.
First embodiment
First, the configuration of a lithium ion secondary battery 100 (hereinafter referred to as battery 100) and a negative electrode collector 50 using a material for a negative electrode collector (negative electrode collector 50) for a secondary battery according to a first embodiment of the present invention will be described with reference to fig. 1 to 3.
(lithium ion Secondary Battery)
As shown in fig. 1, battery 100 includes a cylindrical case 1, a lid 2 for sealing an opening of case 1, and a power storage element 3 disposed in case 1. The case 1 is made of a Ni-plated steel sheet and serves as a negative electrode terminal of the battery 100.
The case 1 accommodates the power storage element 3 and an electrolyte (not shown). The cover 2 is made of an aluminum alloy or the like and 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 disposed 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) disposed on the surface of the positive electrode current collector. The positive electrode active material layer has: positive electrode active materials such as lithium manganate; and an adhesive composed of a resin material.
The battery 100 further includes: a positive electrode lead wire 7 for connecting the positive electrode 4 and the positive electrode terminal (cap 2); and a negative electrode lead material 8 for connecting the negative electrode 5 and the negative electrode terminal (case 1). 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 cover material 2 by resistance welding or the like. The negative electrode lead wire 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 case 1 by resistance welding or the like.
(negative electrode)
As shown in fig. 2, the anode 5 includes an anode current collector 50 and an anode active material layer 51 disposed on a surface 50a of the anode current collector 50.
The anode active material layer 51 has: a negative electrode active material (not shown) composed of C (carbon), si (silicon), silicon oxide, sn (tin), tin oxide, or the like; and a binder for adhering the anode active material to the surface 50a of the anode current collector 50.
The negative electrode active material absorbs or releases Li with charge and discharge + (lithium ions), thereby increasing or decreasing the volume. Therefore, as charge and discharge are repeated, stress is applied to the negative electrode current collector 50.
The adhesive is composed of a resin material. The adhesive is composed of, for example, acrylic resin, polyimide resin, or fluororesin (for example, polyvinylidene fluoride (PVDF)). Among them, the binder made of acrylic resin can use an aqueous slurry, and can easily use a coating material layer (negative electrode active material layer 51). The adhesive agent comprising polyimide resin has excellent mechanical properties, and the mixture layer is less likely to collapse.
The negative electrode current collector 50 is composed of a secondary battery negative electrode current collector material including a plate-like (foil-like) Cu material 52 composed of Cu or a Cu alloy. Further, as Cu (pure copper), there are so-called C1000-series (JIS standard) oxygen-free copper, dephosphorized copper, annealed copper, and the like. Further, as Cu alloy, there is C2000 series (JIS standard) and the like. The thickness t1 of the negative electrode current collector 50 is preferably small in order to wind up as a part of the power storage element 3 (see fig. 1) in the battery 100.
In the first embodiment, the Cu material 52 has a surface layer 53, and the surface layer 53 is formed by oxidation treatment as rust-preventive treatment and contains CuO crystal phase and Cu 2 O crystal phase and Cu (OH) 2 A crystalline phase. Further, the area ratio of CuO crystal phase in the surface layer 53 (referred to as area ratio A1), that is, the area of CuO crystal phase/(area of CuO crystal phase+cu) 2 Area of O crystal phase) is 22.0% or more. The above area ratio A1 is preferably 30.0% or more, more preferably 40.0% or more, and even more preferably the area of CuO crystal phase is equal to or larger than Cu 2 The area of the O crystal phase is equal to or more than 50.0%.
In the surface layer 53, the area ratio of CuO crystal phase (referred to as area ratio B1) in another aspect is defined as the area of CuO crystal phase/(the area of CuO crystal phase+cu) 2 Area of O Crystal phase+Cu (OH) 2 The area of the crystal phase) is preferably 15.0% or more. The above area ratio B1 is more preferably 30.0% or more, still more preferably 35.0% or more, and still more preferably the area of CuO crystal phase is equal to or larger than Cu 2 O crystal phase and Cu (OH) 2 The total area of the crystal phases is equal to or more than 50.0%.
Furthermore, the area ratio of CuO crystal phase in the surface layer 53, cu 2 Area ratio of O crystal phase and Cu (OH) 2 The area ratio of the crystal phase was obtained by XPS (ESCA: electron Spectroscopy for Chemical Analysis (chemical analysis Electron Spectrometry)) for the surface layer 53. Specifically, a narrow scan spectrum of Cu2p was obtained using XPS (ESCA). Then according to Cu2p 3/2 Peak of binding energy of (2)The peak of CuO crystal phase (933.6 eV) and Cu are combined by the peripheral spectrum 2 Peak of O crystal phase (932.5 eV), cu (OH) 2 The peak of the crystal phase (935.1 eV) was separated to obtain CuO and Cu 2 O and Cu (OH) 2 Area ratio of each crystal phase.
Then, cuO and Cu were obtained 2 The sum of the areas of the peaks of the respective crystal phases (referred to as the total area A0). Then, the ratio of the area of the peak of the CuO crystal phase to the total area A0, i.e., the ratio of the area of the CuO crystal phase/(the area of the CuO crystal phase+Cu) was obtained 2 The area of the O crystal phase) was determined as the above area ratio A1. Similarly, cu was obtained 2 The ratio of the area of the peak of the O crystal phase to the total area A0, namely Cu 2 Area of O crystal phase/(area of CuO crystal phase+Cu) 2 Area of O crystal phase) was determined, and this value was defined as an area ratio A2.
And, calculate CuO, cu 2 O and Cu (OH) 2 The sum of the areas of the peaks of the respective crystal phases (referred to as the total area B0). Then, the ratio of the area of the peak of the CuO crystal phase to the total area B0, that is, the ratio of the area of the CuO crystal phase/(the area of the CuO crystal phase+Cu) was obtained 2 Area of O Crystal phase+Cu (OH) 2 Area of crystal phase), and this value was defined as the above-mentioned area ratio B1. Similarly, cu was obtained 2 The ratio of the area of the peak of the O crystal phase to the total area B0, namely Cu 2 Area of O crystal phase/(area of CuO crystal phase+Cu) 2 Area of O Crystal phase+Cu (OH) 2 Area of crystal phase), and this value was defined as an area ratio B2. Similarly, cu (OH) was obtained 2 The ratio of the area of the peaks to the total area B0, i.e., cu (OH) 2 Area of crystal phase/(area of CuO crystal phase+Cu) 2 Area of O Crystal phase+Cu (OH) 2 Area of crystal phase), and this value was defined as an area ratio B3.
Furthermore, cu (OH) 2 Less stable, cuO can be changed due to heat or the like when the anode active material is disposed on the anode current collector 50 via the binder. This can further increase the area ratio of CuO crystal phase.
The surface layer 53 may contain CuO crystal phase and Cu 2 O crystal phase and Cu (OH) 2 A crystal phase other than the crystal phase.
The surface layer 53 is formed so as to cover the Cu material 52 over substantially the entire surface of the Cu material 52. The surface layer 53 may be formed on at least the surface (plate surface) of the Cu material 52 to which the negative electrode active material layer 51 is bonded, or may not be formed on the surface of the end face (left and right faces of the Cu material 52 in fig. 2) along the thickness direction (Z direction) of the Cu material. The thickness t2 of the surface layer 53 is 50nm or less, and is sufficiently smaller than the Cu material 52. As a result, when the conductive material 8 for negative electrode is bonded, an increase in contact resistance due to the surface layer 53 can be suppressed. The thickness t2 of the surface layer 53 is preferably 20nm or less. As a result, since the thickness t2 of the surface layer 53 is extremely small, almost no color of the crystal phase constituting the surface layer 53 (for example, black of CuO or Cu is observed as the appearance of the negative electrode current collector 50 2 O) and the color of Cu or Cu alloy constituting the Cu material 52 (for example, orange red in the case of Cu) is observed. In fig. 2, the thickness t2 of the surface layer 53 is shown exaggerated for easy understanding.
Further, the surface 50a of the negative electrode current collector 50 on the surface layer 53 side (in fig. 2, the portion of the surface layer 53 to which the negative electrode active material layer 51 is adhered and the portion exposed to the outside) is roughened with respect to the Cu material 52 to form fine irregularities. At least a part of the irregularities formed on the Cu material 52 is larger than the thickness t2 of the surface layer 53, whereby the surface layer 53 is formed so as to cover each of the irregularities of the Cu material 52 in practice, as shown in an enlarged and exaggerated manner in fig. 3, instead of being in a neat layer shape as shown in fig. 2. Then, the negative electrode active material layer 51 enters the irregularities formed in the Cu material 52, and thereby the adhesion between the negative electrode current collector 50 and the negative electrode active material layer 51 is improved.
In addition, in the negative electrode current collector 50 roughened by the roughening treatment, the arithmetic average roughness Ra on the surface layer 53 side in accordance with JIS B0601:1994 is preferably 0.06 μm or more, more preferably 0.075 μm or more. The ten-point average roughness Rz on the surface layer 53 side in accordance with JIS B0601:1994 is preferably 0.30 μm or more, more preferably 0.35 μm or more. The ten-point average roughness Rz of the surface layer 53 side is particularly preferably 0.40 μm or more. As a result, the state of adhesion of the anode active material layer 51 to the anode current collector 50 is good.
(method for producing negative electrode 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, roughening treatment is performed on the Cu material 52. In the roughening treatment, so-called soft etching is performed using a weakly acidic aqueous solution containing potassium sulfate. Thereby, fine irregularities are formed on the surface of the Cu material 52. Further, since the soft etching can be performed to slowly perform etching (dissolution), the foil-like Cu material 52 having a small thickness can be suppressed from being rapidly etched and excessively dissolved.
Then, after the neutralization treatment is performed on the Cu material 52 subjected to the roughening treatment, an oxidation treatment as a rust prevention treatment is performed. In the rust inhibitive treatment, the surface of the Cu material 52 which has been subjected to the roughening treatment is oxidized using hydrogen peroxide water. At this time, if the proportion (concentration) of hydrogen peroxide in the hydrogen peroxide water is increased, cuO crystal phase tends to be formed. Specifically, by using hydrogen peroxide water in a concentration of 0.5% by mass or more, the area ratio of CuO crystal phase can be set to 15.0% or more. In order to increase the area ratio of CuO crystal phase, hydrogen peroxide water having a mass percentage concentration of 1.0% or more is preferably used. Thereby, a Cu crystal phase containing CuO and Cu is formed on the surface of the Cu material 52 2 A surface layer 53 containing an O crystal phase and a CuO crystal phase in an area ratio of 15.0% or more. As a result, the negative electrode current collector 50 is produced.
Thereafter, the anode active material layer 51 is formed on the surface layer 53 of the fabricated anode current collector 50. Specifically, the slurry containing the negative electrode active material and the binder is applied to the two surface layers 53 in the thickness direction (Z direction) of the negative electrode current collector 50, and dried and cured. Thus, the negative electrode 5 was produced by adhering the negative electrode active material layer 51 to the surface layer 53 of the negative electrode current collector 50.
Effect of the first embodiment >
In the first embodiment, the following effects can be obtained.
In the first embodiment, as described above, by setting the area ratio (area ratio A1) of CuO crystal phase in the surface layer 53 to 22.0% or more, progress of oxidation can be suppressed in the region of the Cu material 52 made of Cu or Cu alloy that is further inside than the surface layer 53. Thus, a sufficient rust preventing effect can be produced even if the passivation film is not formed by the chromate treatment, and therefore, a material for a secondary battery negative electrode collector (negative electrode collector 50) including a plate-like Cu material having a sufficient rust preventing effect can be provided by a method other than forming the passivation film by the chromate treatment. As a result, the progress of oxidation in the atmosphere can be suppressed, and the increase in 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.
In the first embodiment, the area ratio (area ratio A1) of CuO crystal phase in the surface layer 53 is preferably 50.0% or more, that is, the area of CuO crystal phase in the surface layer 53 is preferably Cu 2 The area of the O crystal phase is equal to or more than that of the crystal phase. If so constructed, since the area capable of having CuO crystal phase is larger than Cu 2 Since the surface layer 53 has an area of the O crystal phase, the progress of oxidation can be reliably suppressed in the region of the Cu material 52 located inside the surface layer 53 only by an amount corresponding to the increase in the area of the CuO crystal phase.
In the first embodiment, the area ratio (area ratio B1) of CuO crystal phase in the surface layer 53 is preferably 15.0% or more. If so constructed, the composition contains not only CuO crystal phase and Cu 2 O crystal phase and Cu (OH) 2 The surface layer 53 of the crystal phase has a CuO crystal phase having an area ratio B1 of 15.0% or more in the surface layer 53, whereby progress of oxidation can be suppressed in a region of the Cu material 52 further inside than the surface layer 53. The surface layer 53 also contains heat or the like generated by bonding the negative electrode active material layer 51Cu (OH) capable of being changed into CuO 2 Since the area ratio (area ratio B1) of the CuO crystal phase can be further increased, progress of oxidation can be reliably suppressed in the region of the Cu material 52 on the inner side of the surface layer 53.
In the first embodiment, the ten-point average roughness of the surface layer 53 is preferably 0.30 μm or more. With this structure, the negative electrode active material layer 51 can be reliably adhered to the surface layer 53 roughened to some extent to form irregularities.
In the first embodiment, a binder for binding the negative electrode active material is disposed on the surface 50 a. Thus, the adhesive can be reliably bonded to the surface layer 53 by the irregularities formed on the surface layer 53 and the increase in the surface area of the surface layer 53. As a result, the negative electrode active material can be reliably bonded to the surface 50a of the negative electrode current collector 50 by the binder. Therefore, even when a stress is repeatedly applied to the negative electrode current collector 50 in association with charge and discharge, occurrence of wrinkles is suppressed, and the negative electrode active material (negative electrode active material layer 51) can be reliably prevented from falling off from the surface 50a of the negative electrode current collector 50.
Second embodiment
Next, a negative electrode 105 according to a second embodiment of the present invention will be described with reference to fig. 4. In the negative electrode 105 according to the second embodiment, an example in which the negative electrode current collector 150 is made of the clad 157 is described, unlike the negative electrode 5 according to the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is 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 disposed on a surface 150a of the negative electrode current collector 150.
The negative electrode current collector 150 is composed of a secondary battery negative electrode current collector material including a plate-shaped clad material 157 having a 3-layer structure, and the clad material 157 includes: a core layer 154 composed of metal; and a pair of Cu layers 155 and 156 respectively bonded to the core layer 154 and composed of Cu or a Cu alloy. The Cu layer 155 is bonded to the Z1 side surface of the core layer 154, and the Cu layer 156 is bonded to the Z2 side surface of the core layer 154. Then, in the clad material 157, the layers are bonded firmly to each other by diffusion annealing at the interface between the core layer 154 and the Cu layer 155 and the interface between the core layer 154 and the Cu layer 156. The thickness t11 of the negative electrode current collector 150 is preferably small in order to wind up as a part of the power storage element in the battery.
The core layer 154 is composed of a metal having a mechanical strength greater than that of the Cu layers 155 and 156. For example, the core layer 154 is preferably made of Ni, a Ni alloy, fe, or a Fe alloy. As Ni (pure nickel), there are the NW2200 system (JIS standard) and the like. As the Ni alloy, there are ni—nb alloy, ni—ta alloy, and the like. Further, as Fe (pure iron), there are so-called SPCC (JIS standard) and the like. As Fe alloys, there are stainless steel (ferrite-based, austenite-based, precipitation-solidified, and martensite-based) and the like. For example, as precipitation-hardening stainless steel, SUS631 (JIS standard) composed of 17 mass% Cr, 7 mass% Ni, 1 mass% Al, other additives, unavoidable impurities, and the balance Fe is present.
In the second embodiment, the Cu layer 155 and the Cu layer 156 have surface layers 158 and 159, respectively. Both the surface layers 158 and 159 contain CuO crystal phase formed by oxidation treatment as rust-preventive treatment and Cu, similarly to the surface layer 53 of the first embodiment described above 2 O crystal phase and Cu (OH) 2 A crystalline phase. Further, the area ratio (area ratio A1) of CuO crystal phase in the surface layers 158 and 159, that is, the area ratio of CuO crystal phase/(area of CuO crystal phase+cu) 2 Area of O crystal phase) is 22.0% or more. The area ratio A1 is preferably 30.0% or more, more preferably 40.0% or more, and even more preferably the area of CuO crystal phase is equal to or larger than Cu 2 The area of the O crystal phase is equal to or more than 50.0%.
In the surface layers 158 and 159, the area ratio of CuO crystal phase (area ratio B1) in another point of view, that is, the area of CuO crystal phase/(area of CuO crystal phase+cu (OH)) 2 Area of crystal phase) is preferably 15.0% or moreAnd (3) upper part. The above area ratio B1 is more preferably 30.0% or more, still more preferably 35.0% or more, and even more preferably the area of CuO crystal phase is equal to or larger than Cu 2 O and Cu (OH) 2 The total area of the crystal phases is equal to or more than 50.0%.
And, cuO crystal phase, cu may be contained in the surface layers 158 and 159 2 O crystal phase and Cu (OH) 2 A crystal phase other than the crystal phase.
The surface layers 158 and 159 are formed on surfaces of the Cu layers 155 and 156 other than the surfaces bonded to the core layer 154, respectively. Specifically, the surface layer 158 is formed on the surface and the side surface on the Z1 side other than the surface on the Z2 side of the Cu layer 155 bonded to the core layer 154. In the same manner, the surface layer 159 is formed on the surface and the side surface on the Z2 side other than the surface on the Z1 side of the Cu layer 156 bonded to the core layer 154. That is, the surface layers 158 and 159 are formed at positions of the Cu layers 155 and 156, respectively, which do not cover the core layer 154. The surface layers 158 and 159 may be formed at least on the surfaces of the Cu layers 155 and 156 that adhere to the anode active material layer 51, and may not be formed on the surfaces of the end surfaces (left and right surfaces of the Cu layers 155 and 156 in fig. 4) of the clad member 157 (anode current collector 150) in the thickness direction (Z direction). The thickness t12a of the surface layer 158 and the thickness t12b of the surface layer 159 are 50nm or less. As a result, the thickness t12a of the surface layer 158 and the thickness t12b of the surface layer 159 are extremely small, and therefore, as the appearance of the negative electrode current collector 150, almost no color of crystal phases constituting the surface layers 158 and 159 (for example, black of CuO or Cu 2 O) and the color of Cu or Cu alloy constituting Cu layers 155 and 156 (e.g., orange-red in the case of Cu) is observed. Also, in fig. 4, the thickness t12a of the surface layer 158 and the thickness t12b of the surface layer 159 are illustrated in an exaggerated manner for ease of presentation.
Further, the surface 150a of the negative electrode current collector 150 on the Z1 side on the surface layer 158 side (in fig. 4, the portion of the surface layer 158 to which the negative electrode active material layer 51 is adhered and the portion exposed to the outside) and the surface 150a of the negative electrode current collector 150 on the Z2 side on the surface layer 159 side (in fig. 4, the portion of the surface layer 159 to which the negative electrode active material layer 51 is adhered and the portion exposed to the outside) are formed into fine irregularities by roughening treatment with respect to the Cu layers 155 and 156, respectively. Specifically, the arithmetic average roughness Ra on the surface 150a side based on JIS B0601:1994 is preferably 0.06 μm or more, more preferably 0.075 μm or more. The ten-point average roughness Rz on the surface 150a side in accordance with JIS B0601:1994 is preferably 0.30 μm or more, more preferably 0.35 μm or more. The ten-point average roughness Rz of the surface 150a side is particularly preferably 0.40 μm or more.
The ratio (t14:t13:t15) of the thickness t13 of the core 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, in order to ensure both sufficient electrical conductivity of the Cu layers 155 and 156 and high mechanical strength of the core material layer 154, the ratio of the thickness (t14:t13:t15) is preferably in the range of about (1:8:1) to (3:4:3). That is, the thickness t13 of the core layer 154 is preferably in the range of 40% to 80% inclusive 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 thickness t15 of the Cu layer 156 are preferably in the range of 10% to 30% inclusive of the thickness t11 of the clad material 157 (negative electrode current collector 150), respectively. Therefore, the thickness t13 of the core layer 154 is preferably greater 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 negative electrode current collector 150, the ratio of the thickness of core layer 154 having high mechanical strength is preferably increased. Further, in the case of further improving the 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.
In order to facilitate rolling in clad rolling, the properties of Cu layer 155 are preferably similar to those of Cu layer 156. That is, it is preferable that the thickness t14 of the Cu layer 155 is substantially equal to the thickness t15 of the Cu layer 156, while the Cu layer 155 and the Cu layer 156 are made of Cu or a Cu alloy having the same composition. The other constitution of the second embodiment is the same as that of the first embodiment.
(method for producing negative electrode 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 of a 3-layer structure is prepared, and the clad material 157 includes a core layer 154 formed by cold rolling (clad rolling) and diffusion annealing, and a pair of Cu layers 155 and 156 bonded to the core layer 154, respectively. Then, as in the first embodiment described above, the clad material 157 (the 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. Also, in this soft etching, cu layers 155 and 156 are selectively etched as compared with core layer 154. Thus, fine irregularities are formed on surfaces of the pair of Cu layers 155 and 156 other than the surfaces bonded to the core layer 154.
Then, after the roughening-treated clad material 157 is subjected to a neutralization treatment, an oxidation treatment as a rust-preventing treatment is performed. In the rust inhibitive treatment, as in the first embodiment described above, the roughened surfaces of the pair of Cu layers 155 and 156 other than the surface to be bonded to the core layer 154 are oxidized using hydrogen peroxide water. Thus, on the surfaces of the pair of Cu layers 155 and 156 other than the surface bonded to the core layer 154, a CuO crystal phase and Cu are formed 2 And surface layers 158 and 159 in which the area ratio (area ratio A1) of the O crystal phase and the CuO crystal phase is 22.0% or more. In another viewpoint, the surface layers 158 and 159 are formed so that the area ratio (area ratio B1) of CuO crystal phase is 15.0% or more, respectively. As a result, the negative electrode current collector 150 is produced.
After that, the anode active material layer 51 is formed on the surface layers 158 and 159 of the fabricated anode current collector 150. Thus, the negative electrode 105 was produced.
Effect of the second embodiment >
In the second embodiment, the following effects can be obtained.
In the second embodiment, as described above, by setting the area ratio (area ratio A1) of CuO crystal phases in the surface layers 158 and 159 to 22.0% or more, the progress of oxidation can be suppressed in the region of the Cu layer 155 inside the surface layer 158 and the region of the Cu layer 156 inside the surface layer 159, which are composed of Cu or a Cu alloy, as in the first embodiment described above. Thus, a sufficient rust preventing effect can be produced even if the passivation film is not formed by the chromate treatment, and therefore, a material for a secondary battery negative electrode collector (negative electrode collector 150) including the plate-like clad material 157 having a sufficient rust preventing effect can be provided by a method other than the formation of the passivation film by the chromate treatment. As a result, the progress of oxidation in the atmosphere can be suppressed, and the increase in 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 to which the negative electrode current collector 150 is bonded can be suppressed.
In the second embodiment, the core layer 154 is preferably made of Ni, a Ni alloy, fe, or an Fe alloy. If so constructed, a core layer 154 having a mechanical strength greater than that of the Cu layers 155 and 156 can be used in the clad material 157 of the core layer 154 and the Cu layers 155 and 156. This can reliably resist the stress caused by expansion and contraction of the negative electrode active material disposed on the negative electrode current collector 150. The other effects of the second embodiment are similar to those of the first embodiment.
Examples (example)
Next, experiments (examples) performed to confirm the effects of the present invention will be described. In the present example, a plurality of secondary battery negative electrode current collector materials were produced by changing the conditions of the rust prevention treatment (oxidation treatment). Then, surface layer analysis, corrosion test, surface roughness measurement, and peeling test were performed on the plurality of secondary battery negative electrode current collector materials produced.
(example 1)
In example 1, a plate-like clad material 157 having a 3-layer structure according to the second embodiment shown in fig. 4 was used as a raw material. In this case, as the core layer 154, a ni—nb alloy containing 5 mass% Nb is used. Further, as the Cu layers 155 and 156, oxygen-free copper (C1020, JIS standard) is used. The thickness t11 of the clad material 157 was set to 10. Mu.m. The ratio (t14:t13:t15) of the thickness t14 of the Cu layer 155, the thickness t13 of the core layer 154, and the thickness t15 of the Cu layer 156 was set to 1:3:1.
Then, with respect to the clad member 157, a test member 1 not subjected to roughening treatment and rust inhibitive treatment (oxidation treatment), a test member 2 subjected to roughening treatment alone without rust inhibitive treatment, and test members 3 to 7 subjected to roughening treatment and rust inhibitive treatment were produced. In the roughening treatment, a so-called soft etching was performed using a weakly acidic aqueous solution containing 5% potassium sulfate by mass percentage and maintained at a temperature of 30 ℃.
In the rust prevention treatment, the roughened clad material 157 is oxidized by hydrogen peroxide water on the surface of the roughened clad material 157 other than the surface of the Cu layers 155 and 156 bonded to the core layer 154. Specifically, the test material 3 contained 0.1% by mass of H 2 O 2 (hydrogen peroxide) the clad 157 was immersed in hydrogen peroxide water for 15 seconds. At this time, the hydrogen peroxide water was maintained at a temperature condition of 20 ℃. In the test material 4, a material containing 0.5% by mass of H was used 2 O 2 Except for the hydrogen peroxide water, the conditions were the same as those of the test material 3. In the test material 5, H was contained at a concentration of 1.0% by mass 2 O 2 Except for the hydrogen peroxide water, the conditions were the same as those of the test material 3.
The test material 6 was the same as the test material 5 except for the points where roughening treatment was performed for 2 times the time of the test materials 2 to 5 and the point where hydrogen peroxide water maintained at a temperature of 40 ℃ was used. In the test material 7, a material containing 5.0% by mass of H was used 2 O 2 Except for the hydrogen peroxide water, the conditions were the same as those of the test material 6. The roughening treatment conditions and rust inhibitive conditions are shown in Table 1. The concentrations shown in table 1 are mass percent concentrations.
TABLE 1
(surface layer analysis)
Then, XPS (ESCA) was used for the core material layers and the Cu layers 155 and 156 in each of the test materials 1 to 7154, the surface layer excluding the surface along the end face in the thickness direction (Z direction) of the test material was analyzed for crystal phase. Then, the area ratios (area ratio A1, area ratio B1) and Cu of the CuO crystal phases of the test materials 1 to 7 were obtained 2 Area ratio of O crystal phase (area ratio A2, area ratio B2) and Cu (OH) 2 Area ratio of crystal phase (area ratio A3, area ratio B3). Specifically, as described in the first embodiment, a narrow scan spectrum of Cu2p was obtained using XPS (ESCA). Thereafter, from Cu2p 3/2 Peak around the binding energy of (a) is a peak (933.6 eV) of CuO crystal phase and Cu 2 Peak of O crystal phase (932.5 eV) and Cu (OH) 2 The peak of the crystalline phase (935.1 eV) was isolated. Then, cuO, cu is obtained 2 O and Cu (OH) 2 The area ratio (area ratio A1 to A3, area ratio B1 to B3) of the respective crystal phases. As an example, the spectra of the test material 2 and the test material 7 are shown in fig. 5 and 6, respectively. In FIGS. 5 and 6, the binding energy (eV) is shown on the horizontal axis and the counts per 1 second (c/s) are shown on the vertical axis, showing the measured spectrum, cuO and Cu 2 O and Cu (OH) 2 Corresponding to the respective crystalline phases of (a) and their synthesis spectra.
(Corrosion test)
Further, each of the test materials 1 to 7 was subjected to corrosion test. Specifically, each of the test materials 1 to 7 was placed in a constant temperature/humidity apparatus maintained at a temperature of 60℃and a relative humidity of 85%, and the test materials were kept for 40 hours. Then, the corrosion degree of the surface of the test materials 1 to 7 except the surface bonded to the core layer 154 of the Cu layers 155 and 156 was observed, and the corrosion degree of the surface of the end face in the thickness direction (Z direction) of the test materials was evaluated for rust prevention.
The rust inhibitive evaluation was performed by visually observing the change in the color tone of the surface of the test material. Specifically, the color (orange red) of the surface of the Cu material (oxygen-free copper) which was not subjected to roughening treatment and rust-proofing treatment and the color (pink) of the surface of the Cu material (oxygen-free copper) which was subjected to roughening treatment and rust-proofing treatment with hydrogen peroxide water were taken as evaluation reference colors, focusing on the color (black) of CuO crystal phase and Cu 2 Color of O crystal phase (reddish brown). Visual observation of test material and evaluation criterionThe case where the color was equal in color tone and no substantial change was observed, and it was determined that no substantial corrosion (oxidation) was performed, and the case where the desired high anti-rust effect or more was obtained was marked with a circle mark (o). Further, when a slight change in the color tone from the evaluation reference color to reddish brown was confirmed, it was judged that corrosion (oxidation) was slightly progressed but practical use was not affected, and a triangle (Δ) was marked as a case where a desired rust preventive effect was obtained. Further, the case where a marked change from the evaluation reference color to a black brown color tone was confirmed, and it was determined that corrosion (oxidation) was performed, and the case where the desired rust inhibitive effect was not satisfied was marked with a cross (x). Further, when a marked change from the evaluation reference color to a black brown color tone was confirmed, it was determined that corrosion (oxidation) was significantly progressed, and when the rust-preventing effect was not exhibited, it was marked with a double-fork mark (×).
The results of the surface layer analysis and corrosion test are shown in table 2.
TABLE 2
As a result of the analysis of the surface layer and the corrosion test, it was confirmed that the desired anticorrosive effect was obtained in the test materials 4 (55.1%) to 7 (90.5%) in which the area ratio A1 of CuO crystal phase in the surface layer subjected to the roughening treatment and the anticorrosive treatment was 22.0% or more with respect to the area ratio A1 of the surface layer. In particular, in the test material 6 (74.8%) and the test material 7 (90.5%) in which the area ratio A1 of CuO crystal phase was 62.0% or more, it was confirmed that a high rust preventing effect was obtained. On the other hand, in the test material 3 (21.9%) in which the area ratio A1 of CuO crystal phase in the surface layer subjected to the roughening treatment and the rust inhibitive treatment was less than 22.0%, it was confirmed that the desired rust inhibitive effect was not satisfied. In particular, in the test material 2 (9.9%) having the CuO crystal phase area smaller than A1, it was confirmed that the rust preventing effect was not obtained.
Further, regarding the area ratio B1 in the surface layer, it was confirmed that the desired rust inhibitive effect was obtained in the test materials 4 (32.9%) to 7 (49.4%) in which the area ratio B1 of CuO crystal phase in the surface layer subjected to the roughening treatment and the rust inhibitive treatment was 15.0% or more. In particular, in the test material 6 (46.4%) and the test material 7 (49.4%) in which the area ratio B1 of CuO crystal phase was 39.0% or more, it was confirmed that a high rust preventing effect was obtained. On the other hand, in the test material 3 (14.9%) in which the area ratio B1 of CuO crystal phase in the surface layer subjected to the roughening treatment and the rust inhibitive treatment was less than 15.0%, it was confirmed that the desired rust inhibitive effect was not satisfied. In particular, in the test material 2 (8.3%) having the CuO crystal phase area smaller than that of B1, it was confirmed that the rust preventive effect was not obtained.
In order to set the area ratio A1 of CuO crystal phase in the surface layer to 22.0% or more, and preferably set the area ratio B1 of CuO crystal phase in the surface layer to 15.0% or more, it was found that the rust preventive effect of the test materials 4 to 7 was obtained: in the rust inhibitive treatment, it is necessary to use a rust inhibitive treatment containing H at a concentration of 0.5% by mass or more 2 O 2 The hydrogen peroxide solution is subjected to a predetermined test for a predetermined test time (15 seconds) or longer at a temperature of room temperature (20 ℃ C.) or higher.
Further, the test material 1, which was not subjected to roughening treatment and rust inhibitive treatment, was obtained with a rust inhibitive effect. This is thought to be because: in the test material 1, since the strong degreasing that is generally performed in association with the roughening treatment and the rust prevention treatment is not performed, the lubricant remains on the surface during rolling, and the progress of corrosion (oxidation) is suppressed by the lubricant remaining on the surface.
From the results of the test materials 3 to 5, it was confirmed that: by increasing the concentration of hydrogen peroxide at the time of the rust inhibitive treatment, the area ratio A1 and the area ratio B1 of CuO crystal phases in the surface layer can be further increased. Moreover, from the results of the test materials 5 and 6, it was confirmed that: by increasing the temperature at the time of the rust inhibitive treatment, the area ratio A1 and the area ratio B1 of the CuO crystal phase in the surface layer can be further increased. Further, it is considered that even if the concentration of the test material 3 is low to some extent (for example, the concentration of the test material 3 is 0.5% by mass), the area ratio A1 of CuO crystal phase in the surface layer can be 22.0% or more and the area ratio B1 of CuO crystal phase in the surface layer can be 15.0% or more, but it is not preferable that the time (tact time) required for manufacturing the material for the secondary battery negative electrode collector is increased.
Regarding the area ratios A1, A2, and the area ratios B1 and B2 in the surface layer, it was confirmed that the area ratio A1 (B1) to Cu in the CuO crystal phase was 2 In the test materials 4 to 7 having the larger area ratio of the O crystal phase than A2 (B2), the area ratio A1 (B1) with respect to the CuO crystal phase in the surface layer did not reach Cu 2 The test materials 2 and 3, in which the area ratio of the O crystal phase was A2 (B2), exhibited higher rust-preventing effect. Further, regarding the area ratios B1 and B3 in the surface layer, it was confirmed that the area ratio B1 in the CuO crystal phase was larger than Cu (OH) 2 In the test materials 5 to 7 having the crystal phase area ratio B3, the area ratio B1 with respect to the CuO crystal phase in the surface layer did not reach Cu 2 The test materials 2 and 3, in which the area ratio of the O crystal phase was B3, exhibited a higher rust-preventing effect.
And, it can be considered that: cu (OH) is generated due to heat or the like generated when a negative electrode active material is disposed on a secondary battery negative electrode current collector material via a binder 2 Can be changed to CuO. Thus, it can be considered that: after the negative electrode current collector is formed, the area ratio of CuO crystal phase is larger, and the rust preventing effect is improved.
(measurement of surface roughness)
Next, in each of the test materials 1 to 7, the surface roughness of the surfaces of the Cu layers 155 and 156 excluding the end surfaces in the thickness direction of the test material was measured with a surface roughness measuring machine, except for the surface bonded to the core layer 154. As the surface roughness, an arithmetic average roughness Ra and a ten-point average roughness Rz based on JIS B0601:1994 were measured. Further, a surface roughness measuring device (Surfcom 480A, stylus radius 2 μm, scanning speed 0.3 mm/sec) manufactured by tokyo precision corporation was used, the cut-off value was set to 0.25mm, and the scanning distance (measurement length) was set to 1.25mm.
(peel test)
In each of the test materials 1 to 7, the adhesion to the binder was measured with respect to the surface of the negative electrode active material layer 51 bonded to the surface other than the surface of the Cu layers 155 and 156 bonded to the core layer 154. Specifically, as shown in fig. 7, an acrylic resin is disposed as a binder (resin material) on the surface of each of the test materials 1 to 7 other than the surface of the Cu layer 155 bonded to the core layer 154. Specifically, the surface on the Z2 side of the Cu layer 155 of each of the test materials 1 to 7 joined to the core layer 154 and the surface on the Z1 side opposite to the thickness direction (Z direction) were coated with an aqueous polyacrylic acid solution at a thickness of 200 μm using an applicator. Then, the coated test materials 1 to 7 were dried and cured by holding them in a dryer set at a temperature of 150 ℃ for 5 minutes. Thus, an acrylic resin layer having a thickness of 5 μm was formed on the surface of the Cu layer 155 on the Z1 side other than the surface bonded to the core layer 154.
Thereafter, a resin tape is attached to the surface of the acrylic resin layer. Then, the resin tape is stretched vertically, that is, in the thickness direction (Z direction) of the clad material 157 using a tensile tester (not shown). Then, the load applied by the tensile tester when peeling was generated in the test materials 1 to 7 was obtained, and the adhesion strength (N/mm) of the test materials 1 to 7 was obtained by dividing the load (N) by the width L (mm) of the resin tape.
The results of the surface roughness measurement and the peeling test are shown in table 3. The "foil/resin" shown in table 3 means between the clad and the acrylic layer, and the "resin/tape" means between the acrylic layer and the resin tape.
TABLE 3
As a result of the surface roughness measurement and the peeling test, peeling was generated between the clad material and the acrylic resin layer in the test material 1 which was not subjected to the roughening treatment. The adhesion strength was also as low as 0.03N/mm. This is considered to be because: in the test material 1, no roughening treatment was performed, and the arithmetic average roughness Ra and the ten-point average roughness Rz were both small on the surface layer side of the clad material where the acrylic resin layer was disposed. On the other hand, in the roughened test materials 2 to 7, 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 is greater than the adhesion strength between the acrylic resin layer and the resin tape (about 0.24N/mm). This is considered to be because: the test materials 2 to 7 were roughened, whereby the arithmetic average roughness Ra and the ten-point average roughness Rz of the surfaces of the clad materials on which the acrylic resin layers were disposed were sufficiently large. In particular, it can be considered that: in the test materials 2 to 7 having the ten-point average roughness Rz of 0.30 μm or more on the surface layer side of the clad material, the adhesion strength between the clad material and the acrylic resin layer was sufficiently high. Moreover, it can be considered that: in the test materials 4 to 7 having the ten-point average roughness Rz of 0.35 μm or more on the surface layer side of the clad material, the adhesion strength between the clad material and the acrylic resin layer was further sufficiently high.
(example 2)
In embodiment 2, the same cladding material 157 as in embodiment 1 above is used, except that SUS631 is used as the core material layer 154. Further, test material 11 and test materials 12 to 14 were produced, in which roughening treatment and rust-preventing treatment (oxidation treatment) were not performed on clad material 157. In the roughening treatment, soft etching was performed under the same conditions as those for the test materials 1 to 5 of example 1.
In the rust inhibitive treatment, the roughened clad material 157 was oxidized by using hydrogen peroxide water, as in the case of example 1, except for the surface of the roughened clad material 157 where the Cu layers 155 and 156 were bonded to the core layer 154. Specifically, the test material 12 contains 1.0% by mass of H 2 O 2 (hydrogen peroxide) the clad 157 was immersed in hydrogen peroxide water for 15 seconds. At this time, the hydrogen peroxide water was kept at a temperature of 15 ℃. In the test material 12, a material containing 3.0% by mass of H was used 2 O 2 Except for the hydrogen peroxide water, the same conditions as those of the test material 11 were used. In the test material 14, a material containing 5.0% by mass of H was used 2 O 2 Hydrogen peroxide of (2)Except for water, the same conditions as those of the test material 11 were used. The roughening treatment conditions and rust inhibitive conditions are shown in Table 4. The concentrations shown in table 4 are mass percent concentrations.
TABLE 4
Then, as in example 1, surface layer analysis and corrosion test were performed. The results of the surface layer analysis and corrosion test are shown in table 5.
TABLE 5
As a result of the analysis of the surface layer and the corrosion test, it was confirmed that the desired anticorrosive effect was obtained in the test materials 12 (22.3%) to 14 (64.8%) in which the area ratio A1 of CuO crystal phase in the surface layer subjected to the roughening treatment and the anticorrosive treatment was 22.0% or more in the area ratio A1 of the surface layer. In particular, it was confirmed that a high rust preventive effect was obtained in the test material 14 (64.8% or more of 60.0%) in which the area ratio A1 of CuO crystal phase was 30.0% or more, compared with the test material 13 (23.8%) in which the area ratio A1 of CuO crystal phase was less than 25.0%.
Further, regarding the area ratio B1 in the surface layer, it was confirmed that the desired rust inhibitive effect was obtained in the test materials 12 (19.6%) to 14 (43.4%) in which the area ratio B1 of CuO crystal phase in the surface layer subjected to the roughening treatment and the rust inhibitive treatment was 15.0% or more. In particular, in the test material 14 (40.0% or more, 43.4%) in which the area ratio B1 of CuO crystal phase was 21.0% or more, it was confirmed that a high rust preventing effect was obtained.
Further, the test material 11 which was not subjected to the roughening treatment and the rust-preventing treatment had a rust-preventing effect. This is considered to be because: in the test piece 11, as in example 1, since the strong degreasing that is usually performed with the roughening treatment and the rust prevention treatment is not performed, the lubricant remains on the surface during rolling, and the progress of corrosion (oxidation) is suppressed by the lubricant remaining on the surface.
From the results of the test materials 12 to 14, it was confirmed that: as in example 1 above, by increasing the concentration of hydrogen peroxide at the time of the rust inhibitive treatment, the area ratio A1 and the area ratio B1 of CuO crystal phases in the surface layer can be further increased.
Also, regarding the area ratios A1, 2, and the area ratios B1 and B2 in the surface layer, it can be confirmed that: the area ratio A1 (B1) of CuO crystal phase is larger than Cu 2 In the test material 14 having the area ratio A2 (B2) of the O crystal phase, the area ratio A1 (B1) of the O crystal phase to the CuO crystal phase in the surface layer is smaller than Cu 2 The test materials 12 and 13, which had the area ratio of the O crystal phase to A2 (B2), obtained higher rust inhibitive effect. And, it can be confirmed that: regarding the area ratios B1 and B3 in the surface layer, the area ratio B1 in the CuO crystal phase is larger than Cu (OH) 2 In the test material 14 having the crystal phase area ratio B3, the area ratio B1 of the crystal phase to CuO in the surface layer is smaller than Cu 2 The area ratio of the O crystal phase was higher than that of the test materials 12 and 13 of B3.
In addition, as in example 1, surface roughness measurement and peel test were performed. 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 and the acrylic layer, and the "resin/tape" means between the acrylic layer and the resin tape.
TABLE 6
As a result of the surface roughness measurement and the peeling test, peeling was generated between the clad material and the acrylic resin layer in the test material 11 which was not subjected to the roughening treatment, as in example 1 described above. The adhesion strength was also small and was 0.02N/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 is greater than the adhesion strength between the acrylic resin layer and the resin tape (about 0.24N/mm). In particular, it can be considered that: in the test materials 12 to 14 having the ten-point average roughness Rz of 0.35 μm or more on the surface layer side of the clad material, the adhesion strength between the clad material and the acrylic resin layer was sufficiently high.
From the results of examples 1 and 2, it can be confirmed that: the clad material having a CuO crystal phase area ratio A1 of 22.0% or more in the surface layer provides a sufficient rust preventing effect regardless of the material of the core layer. And, it can be confirmed that: the clad material having a CuO crystal phase area ratio B1 of 15.0% or more in the surface layer provides a sufficient rust preventing effect regardless of the material of the core layer. As a result, it can be presumed that: even in the case of the secondary battery negative electrode current collector material composed of the Cu material 52 of the first embodiment having no core layer, a sufficient rust preventing effect can be obtained if the area ratio A1 of CuO crystal phase in the surface layer is 22.0% or more. And, it can be presumed that: even in the case of the secondary battery negative electrode current collector material composed of the Cu material 52 of the first embodiment having no core layer, a sufficient rust preventing effect can be obtained if the area ratio B1 of CuO crystal phase in the surface layer is 15.0% or more.
In addition, although in the above embodiment 1, a ni—nb alloy was used as the core layer, and in the above embodiment 2, SUS631 was used as the core layer, even if Ni, a Ni alloy other than the ni—nb alloy, fe, or an Fe alloy other than the SUS631 was used as the core layer, if the area ratio A1 of CuO crystal phase in the surface layer of the secondary battery negative electrode current collector material was 22.0% or more, a sufficient rust preventing effect could be obtained. Further, as the core layer, ni alloy other than Ni, ni—nb alloy, fe or Fe alloy other than SUS631 may be used, and if the area ratio B1 of CuO crystal phase in the surface layer of the secondary battery negative electrode current collector is 15.0% or more, a sufficient rust preventing effect can be obtained.
And, it can be presumed that: although in examples 1 and 2 described above, oxygen-free copper was used as the Cu layer, even if Cu or a Cu alloy other than oxygen-free copper was used, a sufficient rust-preventing effect could be obtained if the area ratio A1 of CuO crystal phase in the surface layer of the secondary battery negative electrode current collector was 22.0% or more. And, it can be presumed that: even if Cu or a Cu alloy other than oxygen-free copper is used, a sufficient rust preventing effect can be obtained if the area ratio B1 of CuO crystal phase in the surface layer of the secondary battery negative electrode current collector is 15.0% or more.
And, it can be considered that: in the above examples 1 and 2, acrylic resin was used as the binder, but even with other resin materials (for example, polyimide resin, fluororesin, etc.), the adhesion strength to the clad material of the present invention was increased similarly to the acrylic resin. In particular, polyimide resins tend to have an increased adhesion strength to the clad material compared to acrylic resins, and therefore, it is considered that: the adhesion strength with the clad material of the present invention is sufficiently increased.
Modification example
Moreover, it should be considered that: the embodiments and examples disclosed herein are illustrative in all respects and are not intended to be limiting. The scope of the present invention is not limited to the description of the embodiments and examples described above, but is defined by the scope of the claims, and includes all modifications (variations) within the meaning and scope equivalent to the claims.
For example, in the first embodiment described above, an example was shown in which the secondary battery negative electrode current collector material is composed of the Cu material 52 having the surface layer 53 formed thereon, but the present invention is not limited to this. In the present invention, the secondary battery negative electrode current collector material may include a layer (plating layer or the like) other than the Cu material.
In the second embodiment, an example was shown in which the secondary battery negative electrode current collector material is constituted by the clad material 157 having a 3-layer structure in which the surface layers 158 and 159 are formed, but the present invention is not limited to this. For example, the secondary battery negative electrode current collector material may be composed of only a clad material having a 2-layer structure composed of 1 core layer and 1 Cu layer having a surface layer. The clad material may be composed of a clad material including a core layer and a layer other than a Cu layer having a surface layer.
In the first and second embodiments, the soft etching using potassium sulfate is performed as the roughening treatment, 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. Further, since the thickness of the secondary battery negative electrode collector is sufficiently small, when an etching solution that rapidly etches the Cu material and the Cu layer is used, the thicknesses of the Cu material and the Cu layer tend to be excessively small. Therefore, it is preferable that an etching solution that rapidly etches the Cu material and the Cu layer is not used in the roughening treatment.
In the first embodiment, the surface layer 53 is formed so as to cover the Cu material 52 substantially over the entire surface of the Cu material 52, but the present invention is not limited to this. In the present invention, the surface layer may be formed so as not to substantially entirely cover the Cu material. For example, the surface layer may be formed only on both surfaces in the thickness direction of the Cu material, which is prone to defects such as a decrease in weldability due to the occurrence of rust (oxidation).
In the second embodiment described above, the surface layer 158 is formed on the surface (surface opposite to the bonded surface) of the Z1 side and the side surface of the Cu layer 155, and the surface layer 159 is formed on the surface (surface opposite to the bonded surface) of the Z2 side and the side surface of the Cu layer 156 in the clad member 157, but the present invention is not limited to this. In the present invention, the surface layer may not be formed on the side surface of the Cu layer in the clad material.
In the first and second embodiments, the example in which the secondary battery negative electrode current collector material is used for the cylindrical lithium ion secondary battery (battery 100) has been described, but the present invention is not limited to this. In the present invention, the material for the negative electrode collector of the secondary battery may be used for secondary batteries other than lithium ion secondary batteries. The secondary battery negative electrode current collector material may be used for, for example, a laminated secondary battery, instead of the cylindrical case 1 shown in fig. 1.

Claims (7)

1. A material for a negative electrode collector of a secondary battery, characterized in that:
comprises a plate-like Cu material composed of Cu or a Cu alloy,
the Cu material has a CuO crystal phase and Cu at least on the surface of the plate 2 O crystal phase and Cu (OH) 2 A surface layer of a crystal phase, in which the surface layer consists of the area of the CuO crystal phase/(the area of the CuO crystal phase+Cu) 2 Area of O crystal phase) is 55.1% or more in percentage, and the surface layer is formed by the area of CuO crystal phase/(the area of CuO crystal phase+cu) 2 Area of O Crystal phase+Cu (OH) 2 Area of crystal phase) is 30.0% or more in percentage.
2. The secondary battery negative electrode collector material according to claim 1, wherein:
the ten-point average roughness of the surface layer side is 0.30 [ mu ] m or more.
3. The secondary battery negative electrode collector material according to claim 2, wherein:
a resin material for bonding the anode active material is provided on the surface.
4. A material for a negative electrode collector of a secondary battery, characterized in that:
comprises a plate-shaped cladding material comprising a core layer made of metal and a Cu layer bonded to the core layer and made of Cu or a Cu alloy,
The clad material has a Cu crystal phase and Cu on at least the surface of the Cu layer opposite to the surface bonded with the core material layer in the thickness direction 2 O crystal phase and Cu (OH) 2 A surface layer of a crystal phase, in which the surface layer consists of the area of the CuO crystal phase/(the area of the CuO crystal phase+Cu) 2 Area of O crystal phase) is 55.1% or more in percentage, and the surface layer is formed by the area of CuO crystal phase/(the area of CuO crystal phase+cu) 2 Area of O Crystal phase+Cu (OH) 2 Crystalline phaseArea) is 30.0% or more in percentage.
5. The secondary battery negative electrode collector material according to claim 4, wherein:
the core material layer is composed of Ni, ni alloy, fe or Fe alloy.
6. The secondary battery negative electrode collector material according to claim 4 or 5, wherein:
the ten-point average roughness of the surface layer side is 0.30 [ mu ] m or more.
7. The secondary battery negative electrode collector material according to claim 6, wherein:
a resin material for bonding the anode active material is provided on the surface.
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