Current collectors and batteries

Abstract

This invention relates to current collectors and batteries. The current collector according to this disclosure comprises a substrate containing aluminum and a protective layer formed on the side of the substrate in contact with the electrode active material layer. The substrate has a strength of 200 MPa or higher.

Description

Technical Field

[0001] This disclosure relates to a current collector and a battery. Background Technology

[0002] Japanese Patent Application Publication No. 2018-116910 (JP 2018-116910 A) discloses a lithium-ion secondary battery. The lithium-ion secondary battery includes a positive electrode current collector, a separator, a negative electrode current collector (hereinafter also referred to as "negative electrode"), an electrolyte, and a battery casing. The negative electrode has a negative electrode precursor (hereinafter also referred to as "negative electrode current collector") and a conductive active material coating (hereinafter also referred to as "negative electrode active material layer") made of a carbon-based material formed on the negative electrode current collector. The negative electrode current collector has an aluminum foil and a coating covering the surface of the aluminum foil. The coating is made of nickel or copper. Summary of the Invention

[0003] However, in the lithium-ion battery disclosed in JP 2018-116910 A, there is a concern that the negative electrode current collector (aluminum foil) will deform when the negative electrode active material layer expands during charging. There is also a concern that this could lead to cracking of the negative electrode active material layer, thereby increasing resistance. Therefore, there is a need for a current collector that can be used to form a battery whose resistance does not easily increase even when the battery is charged and then discharged (hereinafter also referred to as "charge-discharge").

[0004] Furthermore, a current collector is needed to form batteries with excellent structural efficiency. This "structural efficiency" refers to the ratio of the volume of the power-generating elements contained within the battery to the volume of the battery itself.

[0005] One embodiment of this disclosure aims to address the problem of providing a current collector and a battery that "does not easily increase in resistance even during charging and discharging, and is also able to provide a battery with excellent structural efficiency".

[0006] The measures to address the above problems include the following aspects.

[0007] <1> A current collector comprising a substrate containing aluminum, and

[0008] A protective layer is formed on the side of the substrate that contacts the electrode active material layer, wherein

[0009] The tensile strength of the substrate at fracture is above 200 MPa.

[0010] <2> According to the above <1> The current collector, wherein the protective layer contains nickel.

[0011] <3> According to the above <1> or <2> The current collector, wherein the thickness of the protective layer is less than 2.0 μm.

[0012] <4> A battery includes, in sequence, a current collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector according to any one of <1> to <3> above, wherein

[0013] the electrode active material layer is the negative electrode active material layer, and

[0014] the reaction potential (relative to Li+ / Li) of the negative electrode active material contained in the negative electrode active material layer is 0.3 V or less.

[0015] <5> The battery according to <4> above, wherein the electrolyte layer contains a solid electrolyte.

[0016] According to an embodiment of the present disclosure, there are provided a current collector and a battery that "are not likely to increase in resistance even during charge and discharge and can also provide a battery with excellent structural efficiency". BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the drawings, in which the same reference numerals represent the same elements, wherein:

[0018] Figure 1 is a cross-sectional view of a battery according to a first embodiment of the present disclosure; and

[0019] Figure 2 is a cross-sectional view of a battery according to a second embodiment of the present disclosure.

[0020] DETAILED DESCRIPTION OF THE EMBODIMENTS c

[0021] In the present disclosure, a numerical range represented by "to" represents a range including the numerical values written before and after "to" as the minimum value and the maximum value, respectively.

[0022] In the present disclosure where numerical ranges are described in stages, the upper limit value or the lower limit value described in a certain numerical range can be replaced with the upper limit value or the lower limit value of another numerical range described in stages. In the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range can be replaced with the value shown in the examples.

[0023] In the present disclosure, a combination of two or more preferred forms is regarded as a more preferred form.

[0024] In the present disclosure, when describing an embodiment with reference to the drawings, the structure of the embodiment is not limited to the structure shown in the drawings. In addition, the dimensions of the components in the drawings are conceptual, and the relative relationships between the dimensions of the components are not limited thereto.

[0025] (1) Current Collector

[0026] The current collector according to this disclosure comprises a substrate containing aluminum (Al) and a protective layer formed on the side of the substrate in contact with the electrode active material layer. The tensile strength of the substrate at fracture is 200 MPa or higher.

[0027] The “substrate” is a sheet-like material. The term “electrode active material layer” refers to at least one of the positive electrode active material layer and the negative electrode active material layer. The method for measuring the “tensile strength at fracture” is the same as that described in the examples.

[0028] The current collector disclosed herein has the above-described structure, thus providing a current collector and a battery that "does not easily exhibit an increase in resistance even during charging and discharging, and is also able to provide a battery with excellent structural efficiency".

[0029] This effect is presumably due to, but not limited to, the following reasons.

[0030] In this disclosure, the tensile strength at fracture of the substrate is 200 MPa or higher. A tensile strength of 200 MPa or higher at fracture indicates a high strength level of the substrate. Therefore, the current collector is not easily deformed even when the electrode active material layer expands or contracts due to charging and discharging. In other words, the current collector according to this disclosure makes the electrode active material layer less prone to breakage. Furthermore, in this disclosure, the "current collector thickness (%) relative to battery resistance" (described later) is relatively low. In other words, the current collector thickness is relatively thin when the battery resistance is a specific battery resistance. As a result, it is speculated that the current collector of this disclosure can be used to form batteries that do not easily exhibit an increase in resistance even during charging and discharging and also possess excellent structural efficiency.

[0031] When an electrode active material layer is formed on one side of the substrate, a protective layer may or may not be formed on the other side of the substrate.

[0032] The thickness of the current collector in this disclosure is not particularly limited and can be from 5.0 μm to 35.0 μm, from 15.2 μm to 19.0 μm, from 16.0 μm to 18.0 μm, or from 16.0 μm to 17.4 μm.

[0033] The current collector disclosed herein can be used as a negative current collector for a battery, or it can be used as a positive current collector for a battery.

[0034] (1.1) Substrate

[0035] There are no particular restrictions on the substrate material, as long as it contains Al and has a tensile strength at fracture of 200 MPa or higher. From the viewpoint of improving the tensile strength at fracture of the substrate, examples of substrate materials include Al-Mn alloys (alloy number 3000 series), Al-Mg alloys (alloy number 5000 series), and Al-Cu alloys (alloy number 1100 series).

[0036] The tensile strength at fracture of the substrate is above 200 MPa, and can range from 200 MPa to 500 MPa, from 200 MPa to 300 MPa, or from 220 MPa to 270 MPa. The tensile strength at fracture of the substrate can be adjusted by the material of the substrate.

[0037] There are no particular limitations on the thickness of the substrate; from the perspective of obtaining a cell with excellent structural efficiency, it can be 5 μm to 30 μm, or it can be 10 μm to 20 μm.

[0038] (1.2) Protective layer

[0039] The protective layer may contain metallic elements (such as Ni, Fe, Cr, Cu, Au, Ag, etc.). Ni is preferred, as it imparts greater strength to the current collector. The protective layer can be an electrolytic or non-electrolytic plating film.

[0040] The thickness of the protective layer is not particularly limited, but is preferably 2.0 μm or less. Setting the thickness of the protective layer to 2.0 μm or less reduces the amount of protective layer (e.g., electrolytic Ni coating) required for the current collector, while simultaneously creating a battery with excellent structural efficiency, where resistance does not easily increase even during charge and discharge. The thickness of the protective layer can be from 0.1 μm to 2.0 μm, from 0.5 μm to 1.5 μm, or from 0.5 μm to 1.2 μm. "Thickness of the protective layer" refers to the thickness of the protective layer on one side when the protective layer is formed on both sides of the substrate. The thickness of the protective layer is measured using the same measurement method as described in the embodiments.

[0041] (1.3) Resin coating

[0042] The current collector of this disclosure may also include a resin coating on the protective layer. This improves the adhesion between the current collector and the electrode active material layer. The resin coating may contain a resin and conductive additives. Examples of resins include vinyl resins (e.g., polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, etc.) and fluorine resins (e.g., polyvinylidene fluoride, polytetrafluoroethylene, etc.). Examples of conductive additives include carbon materials (e.g., vapor-grown carbon fibers, acetylene black, etc.) and metallic materials (nickel, aluminum, stainless steel, etc.).

[0043] (2) Battery

[0044] The battery disclosed herein sequentially comprises a current collector (hereinafter also referred to as "negative electrode current collector"), a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector, according to the present disclosure. The electrode active material layer is the negative electrode active material layer. The reaction potential (relative to Li+ / Li) of the negative electrode active material contained in the negative electrode active material layer is below 0.3 V.

[0045] The term "negative electrode active material layer" refers to a layer containing negative electrode active material. The term "positive electrode active material layer" refers to a layer containing positive electrode active material. The term "electrolyte layer" refers to a layer interposed between the positive and negative electrode active material layers that contains an electrolyte that conducts ion-carrying (i.e., lithium ions).

[0046] The battery according to this disclosure has the above-described structure, and therefore does not easily exhibit an increase in resistance even during charging and discharging, and has excellent structural efficiency.

[0047] The battery according to this disclosure may have at least one power generation unit. The power generation unit sequentially comprises a negative electrode current collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector. When the battery according to this disclosure includes multiple power generation units, the power generation units may be connected in parallel or in series.

[0048] (2.1) Negative electrode active material layer

[0049] The negative electrode active material layer contains a negative electrode active material with a reaction potential (relative to Li+ / Li) of less than 0.3 V, and may also contain at least one of a solid electrolyte, a conductive material, and a binder, if desired. The negative electrode active material layer is formed on at least one main surface of the negative electrode current collector.

[0050] Examples of negative electrode active materials with a reaction potential (relative to Li+ / Li) of 0.3 V or less include active materials containing Si and carbon materials. Examples of active materials containing Si include elemental silicon, silicon alloys (e.g., alloys of Si and one or more metals selected from the group consisting of Sn, Ti, Fe, Ni, Cu, Co, and Al), porous silicon, silicon clathrate compounds, and silicon oxides. Examples of carbon materials include graphite materials, amorphous carbon materials, carbon black, and activated carbon.

[0051] Examples of solid electrolytes include sulfide-based solid electrolytes (e.g., Li₂S-P₂S₅), oxide-based solid electrolytes, nitride-based solid electrolytes, and halide-based solid electrolytes. Examples of conductive materials include carbon materials (e.g., acetylene black, Ketjen black, vapor-grown carbon fiber (VGCF), etc.), metal particles, and conductive polymers. Examples of adhesives include fluoride-based adhesives (e.g., polyvinylidene fluoride (PVDF), etc.), polyimide-based adhesives, and rubber-based adhesives (e.g., acrylonitrile butadiene rubber (ABR)-based adhesives, etc.).

[0052] (2.2) Electrolyte layer

[0053] The electrolyte layer contains an electrolyte. Specific examples of electrolytes include solid electrolytes, non-aqueous electrolytes containing lithium salts (e.g., LiPF6), non-aqueous gel electrolytes, ion-conducting polymers, etc. The electrolyte layer can be a known electrolyte layer. The electrolyte layer preferably contains a solid electrolyte.

[0054] When the electrolyte layer contains a solid electrolyte, the electrolyte layer (hereinafter also referred to as the "solid electrolyte layer") may also contain a binder as needed. Examples of solid electrolytes and binders include the same solid electrolytes and binders exemplified as those that can be included in the negative electrode active material layer.

[0055] When the electrolyte layer contains a non-aqueous electrolyte, the electrolyte layer has a separator. The separator maintains the gap between the positive electrode active material layer and the negative electrode active material layer to suppress the occurrence of contact short circuits, and also allows lithium ions to pass through. Examples of separators include porous resin sheets and nonwoven fabrics. Examples of materials used for porous resin sheets include polyolefins (polypropylene, polyethylene, etc.). Examples of materials used for nonwoven fabrics include polypropylene, polyethylene terephthalate, methylcellulose, etc.

[0056] (2.3) Positive electrode active material layer

[0057] The positive electrode active material layer contains a positive electrode active material, and may also contain at least one of a solid electrolyte, a conductive material, and a binder, as needed. The positive electrode active material layer is formed on at least one main surface of the positive electrode current collector.

[0058] Examples of positive electrode active materials include oxide active materials. Examples of oxide active materials include layered rock salt active materials (e.g., LiNi). 0.80 Co 0.15 Al 0.05 O2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiCoO2, etc.), spinel active materials (e.g., LiMn2O4, Li4Ti5O4, etc.)12 , etc.), olivine active materials (e.g., LiFePO4, LiMnPO4, etc.).

[0059] Examples of solid electrolytes, conductive materials, and binders include the same solid electrolytes, conductive materials, and binders that are exemplified as being contained in the negative electrode active material layer.

[0060] (2.4) Positive current collector

[0061] A positive current collector is a layer that collects current from a layer of positive active material. Positive current collectors can be sheet-like. Examples of materials used in positive current collectors include stainless steel, aluminum, nickel, iron, titanium, and carbon.

[0062] (2.5) Outer shell

[0063] Batteries according to this disclosure typically include a casing. The casing houses a negative electrode current collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector. Examples of casings include laminated casings, metal cans, etc.

[0064] (2.6) Implementation Method

[0065] like Figure 1 As shown, the battery 1A according to the first embodiment of this disclosure has a power generation unit 1AU and a casing 60. The casing 60 houses the power generation unit 1AU. The power generation unit 1AU comprises a negative electrode current collector 10, a negative electrode active material layer 20, a solid electrolyte layer 30, a positive electrode active material layer 40, and a positive electrode current collector 50, which are sequentially laminated. The negative electrode current collector 10 comprises a substrate 11 and protective layers 12 formed on two main surfaces of the substrate 11. The substrate 11 contains Al. The tensile strength of the substrate 11 at fracture is 200 MPa or more. The reaction potential (relative to Li+ / Li) of the negative electrode active material contained in the negative electrode active material layer 20 is 0.3 V or less.

[0066] like Figure 2 As shown, the battery 1B according to the second embodiment of this disclosure has a power generation unit 1BU, a non-aqueous electrolyte (not shown), and a casing 60. The casing 60 houses the power generation unit 1BU and the non-aqueous electrolyte. The power generation unit 1BU has a negative electrode current collector 10, a negative electrode active material layer 20, a separator 70, a positive electrode active material layer 40, and a positive electrode current collector 50 laminated sequentially. The negative electrode current collector 10 includes a substrate 11 and protective layers 12 formed on two main surfaces of the substrate 11. The substrate 11 contains Al. The tensile strength of the substrate 11 at fracture is 200 MPa or more. The reaction potential (relative to Li+ / Li) of the negative electrode active material contained in the negative electrode active material layer 20 is 0.3 V or less.

[0067] In the following description, implementation of the present disclosure will be described with reference to embodiments. However, it should be noted that the present disclosure is not limited to these embodiments.

[0068] 1. Examples and Comparative Examples

[0069] 1.1 Comparative Example 4

[0070] Prepare a current collector made from a substrate (alloy number A3003, thickness 15 μm).

[0071] Using a Thompson blade shaped as a dumbbell (No. 6) as described in JIS K6251, a substrate (alloy number A3003, thickness 15 μm) was stamped into a dumbbell-shaped test piece. The two ends of the test piece were attached to a tensile testing machine. The tensile testing machine stretched the test piece at a tensile speed of 2 mm / min until it fractured. The measured tensile strength at fracture of the test piece was taken as the "tensile strength at fracture of the substrate". The tensile strength at fracture of Comparative Example 4 was 243 MPa.

[0072] 1.2 Comparative Example 5

[0073] Prepare a current collector made from a substrate (alloy number A1N30, thickness 15 μm).

[0074] The tensile strength at fracture of the test piece was measured in the same manner as in Comparative Example 4, but the substrate was changed to a different substrate (alloy number A1N30, thickness 15 μm). The tensile strength at fracture of Comparative Example 5 was 180 MPa.

[0075] 1.3 Example 1

[0076] A current collector was prepared, which has a substrate (alloy number A3003, thickness 15 μm) and protective layers (made of electrolytic Ni plating, thickness 1.0 μm on each side) formed on both sides of the substrate. The substrate of Example 1 is the same as that of Comparative Example 4. The tensile strength at fracture of Example 1 is 243 MPa.

[0077] 1.4 Example 2

[0078] A current collector was prepared, which had a substrate (alloy number A3003, thickness 15 μm) and protective layers (made of electrolytic Ni plating, thickness 1.4 μm on each side) formed on both sides of the substrate. The substrate of Example 2 was the same as that of Comparative Example 4. The tensile strength at fracture of Example 2 was 243 MPa.

[0079] 1.5 Comparative Example 1

[0080] A current collector was prepared, the current collector having a substrate (alloy number A1N30, thickness 15 μm) and protective layers (material is electrolytic Ni plating, thickness 1.2 μm on each side) formed on both sides of the substrate. The substrate of Comparative Example 1 was the same as that of Comparative Example 5. The tensile strength at fracture of Comparative Example 1 was 180 MPa.

[0081] 1.6 Comparative Example 2

[0082] A current collector was prepared, the current collector having a substrate (alloy number A1N30, thickness 15 μm) and protective layers (material is electrolytic Ni plating, thickness 1.6 μm on each side) formed on both sides of the substrate. The substrate of Comparative Example 2 was the same as that of Comparative Example 5. The tensile strength at fracture of Comparative Example 2 was 180 MPa.

[0083] 1.7 Comparative Example 3

[0084] A current collector was prepared, the current collector having a substrate (alloy number A1N30, thickness 15 μm) and protective layers (material is electrolytic Ni plating, thickness 2.2 μm on each side) formed on both sides of the substrate. The substrate of Comparative Example 3 was the same as that of Comparative Example 5. The tensile strength at fracture of Comparative Example 3 was 180 MPa.

[0085] 2. Measurement Method

[0086] 2.1 Thickness of the protective layer

[0087] The current collector was cross-sectioned using a section polisher (CP) to obtain a test piece. The thickness of the protective layer was measured using scanning electron microscopy (SEM) images of the test piece. The measured value of the protective layer thickness was recorded as the "protective layer thickness".

[0088] 2.2 Tensile strength at fracture of the current collector (%)

[0089] The current collector is stamped into a dumbbell-shaped test piece. Both ends of the test piece are attached to a tensile testing machine. The tensile testing machine stretches the test piece at a tensile speed of 2 mm / min until it breaks. The tensile strength of the test piece at fracture is measured.

[0090] According to the following formula (i), with the measured value of the tensile strength at fracture of the test piece of Comparative Example 1 as 100, the relative value of the measured value of the tensile strength at fracture of the test piece of each example is defined as "tensile strength at fracture of current collector (%)".

[0091] Equation (i): Tensile strength at fracture of the current collector (%) = (Measured tensile strength at fracture of the test piece in each example / Measured tensile strength at fracture of the test piece in Comparative Example 1) × 100

[0092] Regarding Comparative Examples 4 and 5, the tensile strength at fracture of the substrate was divided by the substrate thickness measured by a film thickness gauge to obtain a calculated value, which was used as the "measured value of the tensile strength at fracture of the test piece", and thus the tensile strength (%) at fracture of the current collector was obtained.

[0093] 2.3 Current collector stiffness (%)

[0094] The stiffness values ​​for each example are calculated according to the following formula (ii). The Young's modulus of aluminum and nickel are obtained from the table of physical properties of metals.

[0095] Equation (ii): Stiffness value = Substrate film thickness × Young's modulus of Al (68 GPa) + Protective layer (Ni coating) film thickness × Young's modulus of Ni (204 GPa)

[0096] According to the following formula (iii), with the stiffness value of Comparative Example 1 being 100, the relative value of the stiffness value of each example is calculated as "stiffness (%)".

[0097] Equation (iii): Stiffness (%) = (Calculated stiffness value of each example / Calculated stiffness value of Comparative Example 1) × 100

[0098] 2.4 Battery Resistance

[0099] As described below, a current collector is used to manufacture the battery laminate, and the battery resistance is measured.

[0100] 2.4.1 Solid Electrolyte Layer

[0101] A slurry containing a sulfide-based solid electrolyte (SE) (SE:Li2S-P2S5), an acrylonitrile-butadiene rubber (ABR) binder, heptane, and butyl butyrate was stirred using an ultrasonic dispersion device. The mass ratio (SE:ABR binder) was adjusted to 99.4:0.6. This yielded the SE slurry. The SE slurry was applied to a stainless steel (SUS) foil using a doctor blade method, dried on a hot plate at 50°C for 1 minute, and then further dried on a hot plate at 150°C for 30 minutes. This resulted in a solid electrolyte layer with the stainless steel foil attached. The solid electrolyte layer with the stainless steel foil has the stainless steel foil and the solid electrolyte layer formed on the stainless steel foil.

[0102] 2.4.2 Positive electrode

[0103] Stirring the material containing the positive electrode active material (LiNi) using an ultrasonic dispersion device 0.80 Co 0.15 Al 0.05A slurry consisting of O2 (lithium nickel cobalt aluminum oxide (NCA)), a sulfide-based solid electrolyte (SE:Li2S-P2S5), vapor-grown carbon fiber (VGCF), polyvinylidene fluoride (PVdF) binder, and butyl butyrate was prepared. The mass ratio (NCA:SE:VGCF:PVdF binder) was adjusted to 78.3:18.8:2.9:2.8. This yielded the positive electrode slurry. The positive electrode slurry was applied to an aluminum (Al) foil using a doctor blade method, dried on a hot plate at 50°C for 20 minutes, and then further dried on a hot plate at 150°C for 30 minutes. This yielded the positive electrode. The positive electrode has a positive electrode current collector (Al foil) and a layer of positive electrode active material formed on the positive electrode current collector.

[0104] 2.4.3 Negative electrode

[0105] Vinyl resin was mixed with carbon, and then a solvent was mixed to obtain a resin slurry. The mass ratio (vinyl resin: carbon) was adjusted to 4:1. The resin slurry was applied to the current collectors (current collectors of Examples 1 and 2, and Comparative Examples 1 to 5) by a doctor blade method, dried on a hot plate at 50°C for 20 minutes, and then dried on a hot plate at 150°C for another 30 minutes. As a result, a current collector with a resin coating was obtained. It should be noted that the resistance of the film formed solely by the resin slurry was measured by a four-terminal test, and the measured resistance value was found to be 10 Ω·cm.

[0106] A slurry containing a negative electrode active material (silicon), a sulfide-based solid electrolyte (SE:Li2S-P2S5), vapor-grown carbon fiber (VGCF), polyvinylidene fluoride (PVdF) binder, and butyl butyrate was stirred using an ultrasonic dispersion device. This yielded a negative electrode slurry. The mass ratio (silicon:SE:VGCF:PVdF binder) was adjusted to 49.0:41.2:7.5:6.6. The negative electrode slurry was applied to a resin-coated current collector using a doctor blade method, dried on a hot plate at 50°C for 20 minutes, and then further dried on a hot plate at 150°C for 30 minutes. This yielded a negative electrode. The negative electrode comprises a negative electrode current collector (with a resin coating attached) and a layer of negative electrode active material formed on the negative electrode current collector.

[0107] 2.4.4 Electrode Laminate

[0108] A first laminate is obtained by laminating (decorreling) the negative electrode and a solid electrolyte layer with attached stainless steel foil, bringing the negative electrode active material layer and the solid electrolyte layer into contact with each other. The laminate is then pressed using a roller press at a pressure of 50 kN / cm and a temperature of 160°C. The stainless steel foil is peeled off from the pressed laminate to obtain the negative electrode laminate. Furthermore, the negative electrode laminate and the solid electrolyte layer with attached stainless steel foil are laminated, bringing the solid electrolyte into contact with each other, to obtain a second laminate. The second laminate is pre-pressed in a planar uniaxial press at a pressure of 100 MPa and a temperature of 25°C. After pre-pressing, the stainless steel foil is peeled off from the second laminate, and then it is stamped to 1.08 cm. 2 The dimensions were determined. This resulted in a negative electrode laminate with an attached solid electrolyte layer.

[0109] A positive electrode and a solid electrolyte layer with attached stainless steel foil are laminated to bring the positive electrode active material layer and the solid electrolyte layer into contact, thereby obtaining a laminate. The laminate is pressed using a roller press at a pressure of 50 kN / cm and a temperature of 160°C. The stainless steel foil is peeled off from the pressed laminate, and the laminate is punched into 1 cm thick pieces. 2 The dimensions were determined. This resulted in the positive electrode laminate.

[0110] A positive electrode laminate and a negative electrode laminate with an attached solid electrolyte layer are laminated together to bring the solid electrolyte layers into contact with each other, thereby obtaining a laminate. This laminate is then pressed in a planar uniaxial press at a pressure of 500 MPa and a temperature of 160°C to obtain a battery laminate.

[0111] 2.4.5 Initial charging and discharging

[0112] The battery laminate is sandwiched between two constraint plates. The two constraint plates are fastened with fasteners at a constraint pressure of 1 MPa to fix the distance between them. This yields a battery laminate with the constraint plates attached. The battery laminate with the constraint plates is charged at a constant current of 1 / 10 C to 4.05 V, then charged at a constant voltage at 4.05 V to a final current of 1 / 100 C, then discharged at a constant current of 1 / 10 C to 2.5 V, and finally discharged at a constant voltage at 2.5 V to a final current of 1 / 100 C.

[0113] 2.4.6 Battery resistance (%)

[0114] The battery was charged at a constant current of 1 / 3 C to 4.05 V, then charged at a constant voltage to 1 / 100 C, and then discharged at a constant current of 1 / 3 C to 3.29 V. The state of charge (SOC) was then adjusted at 1 / 100 C. After adjusting the SOC, it was discharged at a constant current of 6 C for 5 seconds. The battery resistance was calculated from the voltage drop at this point.

[0115] According to the following formula (iv), with the calculated value of the battery resistance in Comparative Example 1 as 100, the relative value of the calculated battery resistance for each example is calculated as "Battery Resistance (%)". An acceptable battery resistance (%) is 90% or less.

[0116] Equation (iv): Battery resistance (%) = (Calculated battery resistance in each example / Calculated battery resistance in Comparative Example 1) × 100

[0117] 2.4.7 Current collector thickness (%) relative to battery resistance

[0118] For Examples 1, 2, and Comparative Example 3, where the battery resistance (%) is 90% or less, the current collector thickness relative to the battery resistance was calculated. According to the following formula (v), with the calculated value of the current collector thickness relative to the battery resistance in Comparative Example 3 as 100, the relative value of the calculated value of the current collector thickness relative to the battery resistance in each example is defined as "current collector thickness (%) relative to battery resistance". The lower the current collector thickness (%) relative to the battery resistance, the more efficient the battery structure can be. An acceptable current collector thickness (%) relative to the battery resistance is 99% or less.

[0119] Equation (v): Current collector thickness relative to battery resistance (%) = (Calculated value of current collector thickness relative to battery resistance in each example / Calculated value of current collector thickness relative to battery resistance in Comparative Example 3) × 100

[0120] Table 1

[0121]

[0122] In Comparative Examples 1 to 3, the current collector has an Al-containing substrate and a protective layer. The strength of the substrate is not more than 200 MPa. Therefore, in Comparative Examples 1 and 2, the battery resistance (%) is not more than 90%. In Comparative Example 3, the battery resistance (%) is less than 90%, but the current collector thickness (%) relative to the battery resistance is not more than 99%.

[0123] In Comparative Examples 4 and 5, the current collector was not provided with a protective layer. Therefore, in Comparative Examples 4 and 5, the battery resistance (%) was not below 90%.

[0124] As a result, it was found that the current collectors of Comparative Examples 1 to 5 were not "current collectors that can manufacture batteries whose resistance does not easily increase even during charging and discharging and which also have excellent structural efficiency".

[0125] In Examples 1 and 2, the current collector has an Al-containing substrate and a protective layer. The strength of the substrate is 200 MPa or more. Therefore, in Examples 1 and 2, the battery resistance (%) is 90% or less, but the current collector thickness (%) relative to the battery resistance is 99% or less. As a result, the current collectors of Examples 1 and 2 were found to be "current collectors capable of manufacturing batteries with resistance that does not easily increase even during charging and discharging and also have excellent structural efficiency."

Claims

1. A current collector, comprising: Aluminum-containing substrates; and A protective layer is formed on the side of the substrate that contacts the electrode active material layer, wherein The tensile strength of the substrate at fracture is above 200 MPa.

2. The current collector according to claim 1, wherein the protective layer contains nickel.

3. The current collector according to claim 2, wherein the thickness of the protective layer is less than 2.0 μm.

4. A battery, comprising, in sequence: According to claim 1, the current collector, negative electrode active material layer, electrolyte layer, positive electrode active material layer, and positive electrode current collector, wherein... The electrode active material layer is the negative electrode active material layer, and The reaction potential (relative to Li+ / Li) of the negative electrode active material contained in the negative electrode active material layer is below 0.3 V.

5. The battery according to claim 4, wherein the electrolyte layer contains a solid electrolyte.

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