Current collector, method for manufacturing a current collector, and battery

Abstract

To provide a current collector that is lightweight and has improved strength, a method for manufacturing a current collector, and a battery using a current collector that is lightweight and has improved strength. [Solution] A current collector having a first layer containing a light metal and a second layer containing the element Ni, wherein the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an X-ray diffraction (XRD) apparatus has diffraction peaks at the positions 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°, a method for manufacturing the current collector, and a battery using the current collector.

Description

[Technical Field]

[0001] This disclosure relates to a current collector, a method for manufacturing a current collector, and a battery. [Background technology]

[0002] The electrodes of a secondary battery, such as a lithium-ion secondary battery, generally include a metal-containing component called a current collector and an electrode layer containing an electrode active material placed on top of the current collector. In recent years, attempts have been made to replace copper, which is widely used as a material for the negative electrode current collector, with other metals in order to reduce the manufacturing cost of batteries and to make batteries lighter. For example, in a secondary battery using an electrolyte, a method for manufacturing a negative electrode current collector is known in which a coating film made of nickel or copper is formed on aluminum foil in order to suppress the alloying of lithium ions by the electrolyte (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-116910 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In the manufacture of lightweight current collectors and batteries, for example, when the transport speed of the current collector is increased, the strength of the current collector may become insufficient.

[0005] One of the problems that one embodiment of this disclosure aims to solve is to provide a current collector that is lightweight and has improved strength. Another of the problems that one embodiment of this disclosure aims to solve is to provide a method for manufacturing a current collector that is lightweight and has improved strength. Another of the problems that one embodiment of this disclosure aims to solve is to provide a battery that uses a current collector that is lightweight and has improved strength. [Means for solving the problem]

[0006] The means for solving the problem include the following: <1> A current collector having a first layer containing a light metal and a second layer containing the element Ni, the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an X-ray diffraction (XRD) apparatus has diffraction peaks at 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°. <2> The first layer contains Al element <1> The current collector described above. <3> The X-ray diffraction pattern also shows diffraction peaks originating from the element Al. <2> The current collector described above. <4> The first layer has a thickness of 7 μm to 50 μm, and the second layer has a thickness of 0.1 μm to 3 μm. <1> ~ <3> A current collector as described in any one of the following. <5> Tensile strength at room temperature is 21 kgf / mm² 2 That's all. <1> ~ <4> A current collector as described in any one of the following. <6> A method for manufacturing a current collector, comprising the step of forming a second layer containing Ni element on a first layer containing a light metal by electroplating. <7> The first layer contains Al element <6> A method for manufacturing a current collector as described above. <8> The process includes forming a second layer, with a thickness of 0.1 μm to 3 μm, on a first layer, with a thickness of 7 μm to 50 μm. <6> or <7> A method for manufacturing a current collector as described above. <9> The device comprises a first current collector, a first electrode layer, an electrolyte layer, a second electrode layer, and a second current collector, wherein the first current collector is <1> ~ <5> A battery that is a current collector as described in any one of the following. <10> The first electrode layer is the negative electrode layer. <9> The battery listed. <11> The negative electrode layer contains a negative electrode active material that reacts with Li ions at a voltage of 0.3V or less relative to Li. <10> The battery listed. <12> The electrolyte layer contains a solid electrolyte, making it a solid-state battery. <9> ~ <11> The battery listed in one of the following items. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, a current collector with reduced weight and improved strength can be provided. Further, according to one embodiment of the present disclosure, a method for manufacturing a current collector with reduced weight and improved strength can be provided. Further, according to one embodiment of the present disclosure, a battery using a current collector with reduced weight and improved strength can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] [Figure 1a] FIG. 1a is a schematic cross-sectional view of a current collector 10 according to an embodiment of the present disclosure, when the current collector 10 is cut along the stacking direction X, for explaining the configuration of the current collector 10. [Figure 1b] FIG. 1b is a schematic cross-sectional view of a current collector 20 according to an embodiment of the present disclosure, when the current collector 20 is cut along the stacking direction X, for explaining the configuration of the current collector 20. [Figure 2] FIG. 2 is a schematic cross-sectional view of an electrode laminate structure 30 included in a battery according to an embodiment of the present disclosure, when the electrode laminate structure 30 is cut along the stacking direction X, for explaining the configuration of the electrode laminate structure 30. [Figure 3] FIG. 3 is a graph showing X-ray analysis patterns measured by an XRD apparatus for each current collector obtained in Examples and Comparative Examples. [Figure 4] FIG. 4 is a graph showing X-ray analysis patterns measured by an XRD apparatus for the current collector obtained in the Comparative Example. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present disclosure, a numerical range indicated using "~" means a range including the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other stepwise descriptions. In the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the Examples. In this disclosure, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved. In this disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, unless otherwise specified, the amount of each component refers to the total amount of multiple substances if there are multiple substances corresponding to each component. When embodiments are described in this disclosure with reference to the drawings, the configuration of such embodiments is not limited to the configuration shown in the drawings. Furthermore, the sizes of the components in each figure are conceptual, and the relative relationships between the sizes of the components are not limited thereto. In this disclosure, "room temperature" means 25°C.

[0010] <Current collector> An embodiment of the present disclosure of a current collector (hereinafter also referred to as the current collector) has a first layer containing a light metal and a second layer containing the element Ni. In the current collector, the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an X-ray diffraction (XRD) apparatus has diffraction peaks at the positions of 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°.

[0011] The inventors investigated how to improve the strength of lightweight current collectors and focused on the coating film (i.e., the second layer) placed on the base material layer (i.e., the first layer) of the current collector. They found that the strength of the current collector is improved when the coating film has a specific structure.

[0012] As shown in the examples described later, a current collector having a first layer containing a light metal and a second layer containing Ni, in which the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an X-ray diffraction (XRD) apparatus has diffraction peaks at all positions of 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°, showed improved tensile strength compared to a current collector in which such diffraction peaks were not observed.

[0013] Although the mechanism by which the above effects are achieved is not clear, it is presumed that the second layer, which is a coating film containing the element Ni, has a specific crystal structure when it has a specific X-ray diffraction pattern. Furthermore, it is presumed that this contributes to improving the strength of the current collector by improving the strength of the second layer, improving the adhesion between the second layer and the first layer, and the interaction between the second layer and the first layer.

[0014] (1st layer) The first layer contains light metals. The first layer is the base layer of the current collector. The first layer may contain one or more of these light metals. The proportion of light metal elements in the first layer may be 50% by mass or more, 60% by mass or more, or 70% by mass or more, relative to the total metal elements forming the first layer. For example, the proportion of light metals in the first layer may be 100% by mass, 90% by mass or less, or 80% by mass or less, relative to the total metal elements.

[0015] Light metals include metals with a specific gravity of 4.5 or less. Specifically, examples of light metals include elements such as Al, Mg, Ti, and Li. From the viewpoint of reducing the weight and improving the strength of the current collector, it is preferable that the first layer contains Al. The first layer is preferably Al foil containing Al. The Al foil may be pure aluminum or an alloy. For example, in addition to the 1000 series such as No. 1100, which is pure aluminum, an aluminum alloy system in which other metals are added as alloying elements may also be used. Specifically, the 3000 series such as No. 3003 and No. 3105, which are Al foils with added Mn, and the 5000 series such as No. 5052 and No. 5083, which have added Mg may also be used.

[0016] The thickness of the first layer is not particularly limited and can be selected considering the type and scale of the battery obtained using the current collector. For example, the thickness of the first layer may be 5 μm or more, 7 μm or more, 10 μm or more, or 20 μm or more. For example, the thickness of the first layer may be 100 μm or less, 70 μm or less, or 50 μm or less. From the viewpoint of reducing the weight and improving the strength of the current collector, the thickness of the first layer is preferably 7 μm to 100 μm, more preferably 7 μm to 50 μm, and even more preferably 7 μm to 20 μm.

[0017] (2nd layer) The second layer contains the element Ni. The second layer is a coating film formed on the substrate layer, which is the first layer. When a current collector containing the first and second layers is irradiated with CuKα rays on the second layer using an X-ray diffraction (XRD) apparatus, the resulting X-ray diffraction pattern has diffraction peaks at 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°. These diffraction peaks originate from the element Ni. As described above, the current collector has diffraction peaks at all of the following positions: 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°. This forms a specific structure with Ni in the second layer, improving the strength of the current collector. The second layer may contain elements other than Ni. Furthermore, the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an XRD device may have diffraction peaks other than those mentioned above.

[0018] Having a peak in an X-ray diffraction pattern means that, in XRD analysis using an XRD instrument, a peak can be detected regardless of the width of 2θ after processing such as background correction and noise component removal.

[0019] The measurement conditions using the XRD device are as follows: CuKα X-rays (i.e., 1.54 Å) are used, and 2θ = 5° to 100°. The measurement environment may be either air or an inert gas atmosphere. Examples of inert gases include argon or nitrogen. The step size is preferably 0.01° to 0.03°, and the scan speed is preferably 1° / min to 2° / min.

[0020] When the first layer contains Al, the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays, targeting the current collector, preferably has diffraction peaks originating from Al, from the viewpoint of reducing the weight and improving the strength of the current collector. The diffraction peaks originating from Al originate from the Al contained in the first layer. Considering the measurement conditions or the influence of background noise, the diffraction peaks originating from Al are typically located at 2θ = 38.5 ± 0.5°, 44.7° ± 0.5°, 65.1 ± 0.5°, 78.2 ± 0.5°, and 82.4 ± 0.5°. It is preferable that the diffraction peaks originating from Al have diffraction peaks at at least one of 2θ = 65.1 ± 0.5° and 78.2 ± 0.5°, and it is more preferable that they have diffraction peaks at both 2θ = 65.1 ± 0.5° and 78.2 ± 0.5°.

[0021] Furthermore, if the first layer contains elements other than Al, it is preferable that the X-ray diffraction pattern obtained by irradiating the second layer of the current collector with CuKα rays has diffraction peaks derived from the elements contained in the first layer, in addition to the diffraction peaks based on the Ni element in the second layer, from the viewpoint of reducing the weight and improving the strength of the current collector.

[0022] The second layer may almost completely cover the surface of the first layer or partially cover it. From the viewpoint of reducing the weight and strength of the current collector and the type of electrode layer in contact with the current collector, it is preferable that the coverage rate of the surface of the first layer by the second layer is 50% or more, 70% or more, 80% or more, or 100%. The above coverage rate is a percentage of the value obtained by dividing the area of ​​the second layer in the current collector by the area of ​​the first layer. It is preferable that the coverage rate of the second layer is such that the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays has diffraction peaks originating from the second layer, such as Al elements.

[0023] The thickness of the second layer is not particularly limited and can be selected considering the type and scale of the battery obtained using the current collector. For example, the thickness of the second layer may be 0.1 μm or more, 0.5 μm or more, or 1 μm or more. For example, the thickness of the second layer may be 10 μm or less, 5 μm or less, or 3 μm or less. From the viewpoint of reducing the weight and improving the strength of the current collector, the thickness of the second layer is preferably 0.1 μm to 5 μm, and more preferably 0.1 μm to 3 μm. The thickness of the second layer is preferably such that, in the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays, diffraction peaks originating from the second layer, such as Al, are present.

[0024] From the viewpoint of reducing the weight and improving the strength of the current collector, the combination of coverage and thickness of the second layer is preferably such that the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays has diffraction peaks originating from the second layer, such as Al.

[0025] The tensile strength of the current collector at room temperature is set at 19 kgf / mm² to prevent breakage during transport and other similar processes. 2 Preferably, it is 21 kgf / mm² or higher.2 The above is more preferable. The tensile strength of the current collector is the value measured by the following method. That is, the current collector is punched out into a dumbbell shape using a Thomson die shaped to the shape of a No. 6 dumbbell as described in JIS K 6251, and a test specimen is prepared. The prepared test specimen is gripped on both sides using a tensile testing machine and pulled at a speed of 2 mm / min, and the strength at which it breaks is measured, and the measured value is taken as the tensile strength of the current collector.

[0026] The current collector may have one or more additional layers, in addition to the first and second layers, to provide desired properties such as conductivity and strength, as long as they do not hinder the reduction in weight and improvement of strength of the current collector.

[0027] (Layer structure of the current collector) An embodiment of the current collector described herein may have the second layer arranged on only one side of the first layer, or the second layer arranged on both sides of the first layer. In the former case, the layer configuration is first layer / second layer. In the latter case, the layer configuration is second layer / first layer / second layer. In either layer configuration, the current collector, when the second layer is irradiated with CuKα rays using an XRD device, has diffraction peaks in the X-ray diffraction pattern obtained at 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°.

[0028] As shown in Figure 1(a), a current collector 10, which is one embodiment of the present disclosure, has a first layer 11 and a second layer 12. Direction X is the stacking direction of the current collector 10. As shown in Figure 1(b), a current collector 20, which is one embodiment of the present disclosure, has a first layer 21, a second layer A22, and a second layer B22. The second layer A22 and the second layer B23 are arranged on both sides of the first layer 21, respectively. Direction X is the stacking direction of the current collector 20.

[0029] One embodiment of the current collector of this disclosure may have one side functioning as a positive electrode current collector and the other side functioning as a negative electrode current collector. Such a current collector can be used, for example, as a current collector in a battery having a bipolar structure.

[0030] The current collector of this disclosure may have electrode layers on one or both sides. When electrode layers are arranged on both sides of the current collector, the electrodes arranged on both sides of the current collector may be either positive or negative electrodes, or one electrode layer on both sides of the current collector may be positive and the other negative. A configuration in which the electrode layers arranged on both sides of the current collector are either positive or negative electrodes is applied, for example, to a battery having a monopolar structure. A configuration in which one electrode layer on both sides of a current collector is the positive electrode and the other is the negative electrode is applied, for example, to a battery having a bipolar structure.

[0031] The electrode layers arranged on one or both sides of the current collector may be in contact with the surface on which the second layer of the current collector is located. The electrode layer in contact with the surface on which the second layer of the current collector is located may be either a positive electrode layer or a negative electrode layer, but it is preferable that it be a negative electrode layer from the viewpoint that the effects of alloying lithium ions by the second layer of the current collector are more pronounced.

[0032] (Manufacturing method for current collectors) One embodiment of the present disclosure, a method for manufacturing a current collector (hereinafter also referred to as the "current collector manufacturing method"), includes a step of forming a second layer containing Ni element on a first layer containing a light metal by electroplating (hereinafter referred to as the "second layer formation step"). By forming a second layer containing Ni element on a first layer containing a light metal by electroplating, a current collector can be obtained in which the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an XRD apparatus has diffraction peaks at positions 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°.

[0033] The method for manufacturing the current collector can be any method that allows for the formation of a second layer containing Ni element on the surface of a first layer containing a light metal by electroplating. The second layer formation step includes, for example, if the first layer is Al foil, a degreasing step for the first layer, an etching step for the first layer, a zincate treatment for the first layer, a preparation step for a plating bath containing electrodes and the prepared plating solution, an electroplating step for forming the second layer by immersing the first layer in the plating bath and applying a voltage, and a cleaning step for cleaning the first layer on which the second layer has been formed. Each of these steps may be performed once or multiple times. In addition, at the end of each step, the treated components may be removed by rinsing with water.

[0034] In the above processes, the conditions for electroplating vary depending on the type of plating solution used and cannot be determined in general terms. For example, a plating solution concentration of 0.2% to 80% by mass, a solution temperature of 5 to 70°C, and a current density of 0.5 A / dm². 2 ~60.0A / dm 2 Preferably 2.0 A / dm 2 ~14.0A / dm 2、 The voltage is set to 1V to 100V, and the processing time to 1 second to 20 minutes. The desired plating amount, second layer thickness, and second layer coverage can be adjusted.

[0035] In the method for manufacturing the current collector, the details of the first and second layers are the same as described above. Therefore, in the second layer formation step, it is preferable that the first layer contains the element Al. The thicknesses of the first and second layers are also the same as described above. Therefore, the second layer formation step preferably includes forming a second layer with a thickness of 0.1 μm to 3 μm on a first layer with a thickness of 7 μm to 50 μm.

[0036] A battery to which a current collector, which is one embodiment of the present disclosure, is applied may use a liquid electrolyte (electrolyte solution) as the electrolyte, a solid electrolyte as the electrolyte, or only a solid electrolyte as the electrolyte. In this disclosure, a battery that uses a solid electrolyte as at least part of its electrolyte may be referred to as a "solid-state battery," and a battery that uses only a solid electrolyte as its electrolyte may be referred to as an "all-solid-state battery."

[0037] <Battery> A battery according to one embodiment of the present disclosure (hereinafter also referred to as "battery") includes a structure (hereinafter also referred to as "electrode stacked structure") in which a first current collector, a first electrode layer, an electrolyte layer, a second electrode layer, and a second current collector are arranged in this order, the first current collector having a first layer containing a light metal and a second layer containing the element Ni, and the X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an X-ray diffraction (XRD) apparatus has diffraction peaks at positions 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°, which is a current collector (hereinafter also referred to as "specific current collector").

[0038] In this disclosure, the first current collector and the second current collector may be referred to as "current collector" without distinction, and the first electrode layer and the second electrode layer may be referred to as "electrode layer" without distinction.

[0039] In a battery, when the first current collector is the negative electrode current collector, the second current collector is the positive electrode current collector, and when the first current collector is the positive electrode current collector, the second current collector is the negative electrode current collector. In a battery, when the first electrode layer is the negative electrode layer, the second electrode is the positive electrode layer, and when the first electrode layer is the positive electrode layer, the second electrode layer is the negative electrode layer.

[0040] In a battery, the first current collector may be used as either a negative electrode current collector or a positive electrode current collector. When the first current collector, which is a specific current collector, is used as a negative electrode current collector, it is preferable to use the first current collector as a negative electrode current collector, from the viewpoint that the effects of alloying lithium ions by the second layer of the specific current collector are more pronounced.

[0041] In a battery, the first electrode layer may be either a negative electrode layer or a positive electrode layer. However, when the first electrode layer is a negative electrode layer, it is preferable that the first electrode layer is a negative electrode layer, from the viewpoint that the effects of alloying lithium ions by the second layer of the specific current collector are more pronounced.

[0042] When the first electrode layer, which is a specific current collector, is the negative electrode layer, from the viewpoint of battery performance, it is preferable that the negative electrode layer contains a negative electrode active material that reacts with Li ions at a voltage of 0.3V or less relative to Li. In a battery, the type of electrode active material included in the first electrode layer is not particularly limited. However, it is preferable that the first electrode layer contains Si or C as the electrode active material, from the viewpoint that the effect of suppressing the reaction between the electrode active material and the first layer by the second layer of the specific current collector is more pronounced when the electrode active material included in the first electrode layer contains at least one selected from the group consisting of Si or C. The electrode active material may have a coating layer. Various materials can be used for the coating layer depending on the purpose.

[0043] As shown in Figure 2, the electrode stack structure 30 included in the battery has a structure in which a first current collector 31, a first electrode layer 32, an electrolyte layer 33, a second electrode layer 34, and a second current collector 35 are arranged in this order. The first current collector 31 has a first layer 11 containing a light metal and a second layer 12 containing the element Ni. The X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an X-ray diffraction (XRD) apparatus has diffraction peaks at 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°.

[0044] (Current collector) The type of current collector constituting the electrode stacked structure is not particularly limited as long as at least the first current collector is the specified current collector described above, and can be selected and used from known current collectors. Specifically, the material of the current collector can be a metal selected from Ag, Cu, Au, Al, Ni, Fe, and Ti, or an alloy containing these metals. The thickness of each current collector is not particularly limited and can be selected considering the type and scale of the battery obtained using the current collector. The total thickness of each current collector may be, for example, 5 μm or more, 10 μm or more, or 20 μm or more. The total thickness of each current collector may be, for example, 120 μm or less, 80 μm or less, or 60 μm or less. The details and preferred embodiments of the first current collector, which is the specified current collector, are the same as the details and preferred embodiments of the current collector, which is one embodiment of the present disclosure described above.

[0045] (electrode layer) The type of electrode layer constituting the electrode stacking structure is not particularly limited and can be selected and used from known electrode layers. The electrode layer contains at least an electrode active material and may optionally contain a binder, conductive material, solid electrolyte, etc. If the electrolyte layer contains a solid electrolyte, at least one of the first electrode layer and the second electrode layer, which are arranged on both sides of the electrolyte layer, may also contain a solid electrolyte. In this disclosure, the electrode active material contained in the first electrode layer is also referred to as the first electrode active material, and the electrode active material contained in the second electrode layer is also referred to as the second electrode active material. When the first electrode layer is the negative electrode layer, the first electrode active material is the negative electrode active material, and when the first electrode layer is the positive electrode layer, the first electrode active material is the positive electrode active material. When the second electrode layer is the negative electrode layer, the second electrode active material is the negative electrode active material, and when the second electrode layer is the positive electrode layer, the second electrode active material is the positive electrode active material.

[0046] Examples of negative electrode active materials include carbon materials, active materials containing Si elements, metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides, and transition metal nitrides. Examples of carbon materials include graphite materials, amorphous carbon materials, carbon black, and activated carbon. Examples of graphite materials include natural graphite and artificial graphite. Examples of amorphous carbon materials include hard carbon, soft carbon, coke, mesocarbon microbeads (MCMB), and mesophase pitch carbon fiber (MCF). Graphite materials may be coated with metal or amorphous carbon. Active materials containing the Si element include elemental silicon, silicon alloys (for example, alloys of Si with one or more metals selected from the group consisting of Sn, Ti, Fe, Ni, Cu, Co, and Al), porous silicon, silicon clathrate compounds, silicon oxides, and the like.

[0047] Specifically, examples of positive electrode active materials include composite oxides containing lithium and transition metals (hereinafter also referred to as composite oxides). Examples of composite oxides include composite oxides having a layered crystal structure, composite oxides having a spinel-type crystal structure, and composite oxides having an olivine-type crystal structure. Specific examples of composite oxides having a layered crystal structure include compounds represented as LiMO2 (where M is at least one transition metal selected from the group consisting of Ni, Co, and Mn), and compounds to which heterogeneous elements are added. Representative examples of composite oxides having a layered crystal structure include LCO (lithium cobaltate), NCM (lithium nickel-cobalt-manganate), and NCA (lithium nickelate or lithium nickel-cobalt-aluminate). LiMn2O4 is a specific example of a composite oxide having a spinel-type crystal structure. A specific example of a composite oxide having an olivine-type crystal structure is LiMPO4 (where M is Fe, Co, Ni, or Mn).

[0048] The electrode active material contained in the electrode layer may be a single type or a combination of two or more types. The morphology of the electrode active material may be, for example, fibrous, spherical, or flake-like. The volume-average particle size of the electrode active material may be selected from, for example, a range of 5 μm to 50 μm. The volume-average particle size of the electrode active material is defined as the value (D50) at which the cumulative amount from the smaller diameter side in the volume-based particle size distribution obtained using the laser diffraction-scattering method becomes 50%.

[0049] Examples of binders include polyvinylidene fluoride (PVdF), polyethylene, polypropylene, polyethylene terephthalate, cellulose, nitrocellulose, carboxymethylcellulose, polyethylene oxide, polyepichlorohydrin, polyacrylonitrile, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), polyacrylate, polymethacrylate, and polytetrafluoroethylene (PTFE).

[0050] Examples of conductive materials include carbon materials, metals, conductive oxides, and conductive nitrides. Specific examples of carbon materials include graphite, carbon black (acetylene black, thermal black, furnace black, etc.), carbon nanotubes (CNTs), carbon nanofibers (CNFs), and vapor-grown carbon fibers (VGCFTMs). The conductive material may be of one type only, or two or more types may be used in combination.

[0051] Examples of solid electrolytes include sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes. From the viewpoint of battery performance, sulfide solid electrolytes and polymer solid electrolytes are preferred as solid electrolytes, and from the viewpoint of thermal stability, sulfide solid electrolytes are more preferred. Solid electrolytes may be used individually or in combination of two or more types.

[0052] Examples of sulfide solid electrolytes include compounds containing a metal element that acts as a conductive ion and sulfur (S). Examples of metallic elements include Li, Na, K, Mg, and Ca. Among these, Li is preferred as a metallic element. The sulfide solid electrolyte may contain Li and S, and at least one selected from the group consisting of P, Si, Ge, Al, and B. Among them, a sulfide solid electrolyte containing Li, S, and P (hereinafter, also referred to as an LPS-type sulfide solid electrolyte) is preferable. From the viewpoint of ionic conductivity, the sulfide solid electrolyte may contain halogen elements such as Cl, Br, and I. From the viewpoint of chemical stability, the sulfide solid electrolyte may contain oxygen (O).

[0053] Specific examples of the LPS-type sulfide solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, LiBr-LiI-Li2S-P2S5, Li2S-P2S5-ZmSn (where m and n are positive numbers respectively, and Z is Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-LixMOy (where x and y are positive numbers respectively, and M is P, Si, Ge, B, Al, Ga, or In), etc.

[0054] In the above, the description of "Li2S-P2S5" means a sulfide solid electrolyte obtained by using Li2S and P2S5 as raw materials, and the same applies to other descriptions.

[0055] Among the LPS-type sulfide solid electrolytes, a sulfide solid electrolyte obtained by using Li2S and P2S5 is preferable, and a sulfide solid electrolyte satisfying the following formula is more preferable. Li 3+x+5y P 1-y S4 (0 < x ≦ 0.6, 0 < y ≦ 0.2)

[0056] Examples of the oxide solid electrolyte include NASICON (Na3Zr2PSi2O 12Examples include compounds having a ) type crystal structure. Compounds having a NASICON type crystal structure have high ionic conductivity and excellent stability in air. Examples of compounds having a NASICON-type crystal structure include lithium-containing phosphates. Examples of phosphates include lithium phosphate complexes with Ti (e.g., Li 1+x Al x Ti 2-x (PO4)3) Examples include compounds in which all or part of the Ti in the above-mentioned composite lithium phosphate salt is replaced with a tetravalent transition metal such as Ge, Sn, Hf, or Zr, or a trivalent transition metal such as Al, Ga, In, Y, or La. Specifically, examples of compounds having a NASICON-type crystal structure include Li-Al-Ge-PO-based materials (Li 1+x Al x Ge 2-x (PO4)3), Li-Al-Zr-PO material (Li 1+x Al x Zr 2-x (PO4)3), Li-Al-Ti-PO material (Li 1+x Al x Ti 2-x (PO4)3) are examples.

[0057] Examples of polymeric solid electrolytes include mixtures (complexes) of polymer compounds and electrolyte salts. Specific examples of polymer compounds include polyether-based polymer compounds such as polyethylene oxide (PEO) and polypropylene oxide (PPO), polyamine-based polymer compounds such as polyethyleneimine (PEI), and polysulfide-based polymer compounds such as polyalkylene sulfide (PAS). Among these, polyether-based polymer compounds are preferred.

[0058] (electrolyte layer) Examples of electrolyte layers used in batteries include separators used in batteries that use electrolyte solutions, and electrolyte layers used in all-solid-state batteries. The thickness of the electrolyte layer is not particularly limited and can be selected from a range of, for example, 1 μm to 30 μm.

[0059] When the electrolyte layer is a separator, the type of separator is not particularly limited and can be selected and used from known separators. Specifically, examples of separators include porous sheets made from resins such as polyethylene, polypropylene, polymethylpentene, polyester, cellulose, and polyamide.

[0060] If the electrolyte layer contains a solid electrolyte, the type of solid electrolyte included in the electrolyte layer is not particularly limited. For example, it may be selected and used from the solid electrolytes that may be included in the electrode layer as described above. If the electrolyte layer contains a solid electrolyte, the first electrode layer and the second electrode layer may each contain a solid electrolyte. In this case, the types of solid electrolytes contained in each layer may be the same or different.

[0061] If the battery contains a solid electrolyte, it may also contain an electrolyte solution at a concentration of less than 10% by mass relative to the total amount of electrolyte. If the battery contains a solid electrolyte, the solid electrolyte may be a composite solid electrolyte containing an inorganic solid electrolyte and a polymer electrolyte.

[0062] If the battery contains an electrolyte solution, the type of electrolyte solution is not particularly limited, and any known electrolyte solution can be used. Specific examples of electrolytes include liquids obtained by dissolving lithium salts such as LiPF6 and LiFSi in an organic solvent. Specific examples of organic solvents include cyclic or linear carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The solvent may be a mixture of two or more solvents, or a mixture containing both cyclic and linear carbonates. The solvent may contain additives such as vinylene carbonate (VC).

[0063] From the viewpoint of suppressing the reaction between the electrode active material and the first layer by the second layer of the specific current collector, it is preferable that the battery is a solid-state battery in which the electrolyte layer contains a solid electrolyte.

[0064] (Exterior) The battery may further include an outer casing. The outer casing at least houses the electrode laminate described above. Examples of outer casings include laminate-type outer casings and case-type outer casings. A laminate-type outer casing may be formed from a laminate (laminate film) having a metal layer containing a metal such as aluminum and a heat-seal layer containing a resin that melts when heated.

[0065] (Restraining member) The battery may further include a restraining member. The restraining member applies restraining pressure to the electrode stack described above in the thickness direction. The restraining pressure applied in the thickness direction of the electrode stack may be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. The restraining pressure applied in the thickness direction of the electrode stack may be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0066] <Battery Uses> The applications of the battery are not particularly limited. Typical applications include power sources for vehicles, electronic equipment, and electric storage systems. Of these, the battery of this disclosure is preferably used as a power source for vehicles, and more preferably as a power source for hybrid vehicles, plug-in hybrid vehicles, or electric vehicles. Examples of vehicles include electric four-wheeled vehicles, electric two-wheeled vehicles, gasoline-powered vehicles, and diesel-powered vehicles. Examples of electric four-wheeled vehicles include battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs). Examples of electric two-wheeled vehicles include electric motorcycles and electric-assist bicycles. [Examples]

[0067] Embodiments of this disclosure will be described below with reference to examples. However, this disclosure is not limited to these embodiments.

[0068] <Example 1> (Base material layer (1st layer)) A 15 μm thick 1N30-H material was used as the base layer (i.e., the first layer). The 1N30-H material is a material based on the description in JIS H 4000. The 1N30-H material is a pure aluminum alloy with an aluminum purity of 99.3% or higher, and is an aluminum foil that has been hardened by thermal rolling.

[0069] (Electrolytic plating) Ni was deposited on both sides of this substrate layer by electroplating. The electroplating was carried out on the Al foil of the substrate layer by following the steps 1 to 7 below in order. 1. Add sodium carbonate, sodium metasilicate, sodium tripolyphosphate, and a surfactant, adjust the pH to approximately 10, immerse the aluminum foil in the 50°C solution, and then wash it with water. The substrate layer after step 2.1 was immersed in a sodium hydroxide solution with a pH of approximately 14, and then washed with water. The substrate layer after step 3.2 was immersed in a nitric acid solution and then washed with water. The substrate layer after step 4.3 was immersed in a solution of zinc oxide dissolved in sodium hydroxide solution, and then washed with water. The substrate layer after step 5.4 was immersed in a nitric acid solution and then washed with water. The substrate layer after step 6.5 was immersed in a solution of zinc oxide dissolved in sodium oxide solution, and then washed with water. The substrate layer after step 7.6 was prepared by dissolving boric acid, nickel sulfate, and nickel chloride in water to adjust the pH to approximately 4.0-4.5 and the temperature to 50°C. Holes were made in the aluminum foil, copper wire was wrapped around the holes, and the foil was immersed in the solution. Subsequently, a current of 5 A / dm was applied to the copper wire. 2 Electroplating was performed so that a 2 μm thick coating layer made of Ni was formed on the surface of the substrate layer. As described above, a current collector foil (current collector foil 1) was obtained in which a coating layer containing Ni, 2 μm thick on each side (i.e., a second layer), was formed on the surface of the base layer by electroplating, on each of the two sides of the base layer. The thickness of current collector foil 1 was 16 μm. In the examples and comparative examples, the thickness of the current collector foil and the thickness of the coating layer were measured using images obtained with a scanning electron microscope (SEM) after cross-sectional processing of the surface of the obtained current collector foil cut along the lamination direction using a cross-section polisher.

[0070] <Comparative Example 1> A current collector foil (current collector foil 2) was obtained in the same manner as in Example 1, except that a coating layer containing Ni (i.e., the second layer) was formed on the base layer (1N30-H material) using a plating solution for electroless plating without passing an electric current. The thickness of current collector foil 2 was 16 μm.

[0071] <Comparative Example 2> A current collector foil (current collector foil 3) was obtained by forming a Ni-containing coating layer (i.e., the second layer) on a base layer (1N30-H material) without passing an electric current, in the same manner as in Comparative Example 1, except that a different plating solution was used. The thickness of current collector foil 3 was 14 μm.

[0072] <Comparative Example 3> A current collector foil (current collector foil 4) was obtained by forming a coating layer containing Ni (i.e., the second layer) on a base layer (1N30-H material) without passing an electric current, in the same manner as in Comparative Example 1, except that the plating conditions were different. The thickness of current collector foil 4 was 17 μm.

[0073] <Comparative Example 4> A current collector foil 5 was created by placing a 10 μm thick Ni foil on the upper surface of a base layer (1N30-H material).

[0074] <Rating> (strength) The breaking strength was measured for each of the current collector foils 1 to 4 obtained in Example 1 and Comparative Examples 1 to 3. The breaking strength was determined by punching out the obtained current collector into a dumbbell shape using a Thomson die molded into a dumbbell shape No. 6 as described in JIS K6251, and using the punched-out pieces as test specimens. Using a tensile testing machine, both sides of the punched-out test specimen were grasped and pulled at a speed of 2 mm / min to determine the strength at which it broke. The strength obtained was calculated using the following formula, with the breaking strength of Example 1 set to 100. The calculated breaking strengths for each example are listed in Table 1. Calculation formula: Measured breaking strength / Breaking strength of Example 1 × 100

[0075] (X-ray diffraction pattern) X-ray diffraction patterns were obtained using an XRD apparatus for each of the current collector foils 1 to 5 obtained in Example 1 and Comparative Examples 1 to 4. Each of the current collector foils 1 to 4 was cut into a 2cm square rectangle, and the X-ray diffraction pattern was acquired using an XRD device (manufactured by Rigaku Corporation). The measurement conditions were: CuKα irradiation, 2θ = 5° to 100°, atmospheric environment, scan speed 5° / min, and scan step 0.02°. Figure 3 shows the X-ray diffraction patterns of current collector foils 1 through 4, and Figure 4 shows the X-ray diffraction pattern of current collector foil 5.

[0076] [Table 1]

[0077] As shown in Table 1, Figures 3 and 4, the current collector 1, which has a first layer containing Al foil and a second layer containing Ni element, and whose X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an XRD apparatus has diffraction peaks at 2θ = 44.0°~45.0°, 51.0°~52.0°, 76.0°~77.0°, 92.5°~93.5°, and 98.0°~99.0°, was found to be lightweight and to have improved strength due to the use of Al foil. [Explanation of symbols]

[0078] 10, 20 Current collectors 11, 21 1st layer 12, 22, 23 2nd layer 30 electrode stack structure 31. First current collector 32 1st electrode layer 33 Electrolyte layer 34 Second electrode layer 35. Second current collector X direction

Claims

1. It has a first layer containing a light metal and a second layer containing Ni element, The X-ray diffraction pattern obtained by irradiating the second layer with CuKα rays using an X-ray diffraction (XRD) apparatus is a current collector having diffraction peaks at the positions 2θ = 44.0° to 45.0°, 51.0° to 52.0°, 76.0° to 77.0°, 92.5° to 93.5°, and 98.0° to 99.0°.

2. The current collector according to claim 1, wherein the first layer comprises the element Al.

3. The current collector according to claim 2, wherein the X-ray diffraction pattern further has diffraction peaks originating from the element Al.

4. The current collector according to claim 1, wherein the first layer has a thickness of 7 μm to 50 μm, and the second layer has a thickness of 0.1 μm to 3 μm.

5. Tensile strength at room temperature: 19 kgf / mm ２ The current collector according to claim 1, wherein the above is true.

6. A method for manufacturing a current collector, comprising the step of forming a second layer containing Ni element on a first layer containing a light metal by electroplating.

7. The method for manufacturing a current collector according to claim 6, wherein the first layer contains the element Al.

8. The method for manufacturing a current collector according to claim 6, further comprising the step of forming the second layer having a thickness of 0.1 μm to 3 μm on the first layer having a thickness of 7 μm to 50 μm.

9. The device comprises a first current collector, a first electrode layer, an electrolyte layer, a second electrode layer, and a second current collector. The first current collector is a battery that is a current collector according to any one of claims 1 to 5.

10. The battery according to claim 9, wherein the first electrode layer is a negative electrode layer.

11. The battery according to claim 10, wherein the negative electrode layer comprises a negative electrode active material that reacts with Li ions at a voltage of 0.3 V or less relative to Li.

12. The battery according to claim 9, wherein the electrolyte layer contains a solid electrolyte, and is a solid battery.

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