Current collector, pole piece, secondary battery, and electric device

Abstract

The invention provides a current collector, a pole piece, a secondary battery and an electric device. The current collector comprises a nickel-iron-based alloy, the nickel-iron-based alloy comprises a first doping element, the first doping element is a non-metallic element, and the mass content of the first doping element is less than 10% based on the total mass of the nickel-iron-based alloy.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to a current collector, electrode, secondary battery, and electrical device. Background Technology

[0002] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0003] As the market demands higher energy density from rechargeable batteries, balancing energy density and cycle stability has become a critical technical challenge in this field. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a current collector, electrode, secondary battery and power supply device that balances the energy density and cycle stability of the secondary battery.

[0005] A first aspect of this application provides a current collector comprising a nickel-iron-based alloy, the nickel-iron-based alloy comprising a first doping element, the first doping element being a non-metallic element, and the mass content of the first doping element being less than 10% based on the total mass of the nickel-iron-based alloy.

[0006] Doping with non-metallic elements helps to increase the nucleation rate of nickel-iron-based alloys, reduce the grain size of nickel-iron-based alloys, improve the strength of current collectors, and delay the time of current collector fracture during cycling. At the same time, non-metallic elements are lightweight, which is beneficial for further reducing the mass of current collectors and increasing the energy density per unit mass of secondary batteries. However, the addition of non-metallic elements will reduce the conductivity of current collectors. Controlling the mass content of the first dopant element to less than 10% is beneficial for balancing the strength and conductivity of current collectors and comprehensively improving the cycle life of secondary batteries.

[0007] In any embodiment, the first doping element includes at least one of phosphorus and boron.

[0008] By adding phosphorus and / or boron to nickel-iron based alloys, the mechanical strength and corrosion resistance of current collectors can be improved, thereby comprehensively enhancing the cycle life of current collectors.

[0009] In any embodiment, based on the mass of the nickel-iron-based alloy, the mass content of the first dopant element is 0.1%-8%.

[0010] Controlling the mass content of the first dopant element within a suitable range is beneficial to improving the tensile strength of the current collector while maintaining its good conductivity, thereby comprehensively improving the cycle life of the battery.

[0011] In any embodiment, the first doping element includes phosphorus, and the mass content of phosphorus in the nickel-iron-based alloy is 0.5%-8% based on the mass of the nickel-iron-based alloy.

[0012] When the phosphorus content is within a suitable range, it can effectively improve the tensile strength and corrosion resistance of the current collector, reduce the risk of premature cracking of the electrode during cycling, and at the same time, the appropriate phosphorus content can also maintain the good conductivity of the current collector, thus comprehensively improving the cycle life of the battery.

[0013] In any embodiment, the first doping element includes phosphorus, and the mass content of phosphorus in the nickel-iron-based alloy is 0.5%-5% based on the mass of the nickel-iron-based alloy.

[0014] In any embodiment, the first doping element includes boron, and the mass content of boron in the nickel-iron-based alloy is 0.1%-6% based on the mass of the nickel-iron-based alloy.

[0015] When the boron content is within a suitable range, it can effectively improve the tensile strength and corrosion resistance of the current collector, reduce the risk of premature cracking of the electrode during cycling, and at the same time, the appropriate boron content can also effectively maintain the conductivity of the current collector, thus comprehensively improving the cycle life of the battery.

[0016] In any embodiment, the first doping element includes boron, and the boron content in the nickel-iron-based alloy is 3%-6% based on the mass of the alloy.

[0017] In any embodiment, based on the mass of the nickel-iron-based alloy, the mass content of iron in the nickel-iron-based alloy is 40%-50%, and the mass content of nickel in the nickel-iron-based alloy is 50%-60%.

[0018] When the mass content of iron and nickel is within the above range, the strength of the current collector can be improved while taking into account the plasticity and corrosion resistance of the current collector, thereby further improving the cycle stability of the secondary battery.

[0019] In any embodiment, the nickel-iron-based alloy is composed of 40%-50% iron by mass, 50%-60% nickel by mass, 0.1%-8% of a first dopant element by mass, and impurities, wherein the mass content of the impurities is less than 6%.

[0020] In any embodiment, the average grain size of the grains in the current collector is 2nm-17nm.

[0021] The current collector contains nanocrystalline structures with very small particle sizes. The nanocrystalline structure can improve the tensile strength and corrosion resistance of the current collector and reduce the possibility of premature cracking of the electrode during the cycle.

[0022] In any embodiment, the current collector has a first surface and a second surface opposite to each other. The thickness of the current collector is denoted as H. The region from the first surface of the current collector to a thickness range of 0.2H is denoted as the first region of the current collector. The region from the first surface of the current collector to a thickness range of 0.4H-0.6H is denoted as the second region of the current collector. The region from the second surface of the current collector to a thickness range of 0.2H is denoted as the third region of the current collector. The range of the mass content of the first dopant element in the first region, the mass content of the first dopant element in the second region, and the mass content of the first dopant element in the third region is less than or equal to 3%.

[0023] The small range of mass content variation of the first dopant element in different regions of the current collector indicates that the distribution of phosphorus or boron elements in different regions of the current collector is highly uniform, which improves the overall mechanical strength of the current collector, reduces the possibility of electrode cracking during cycling, and helps to improve the reliability of the current collector during cycling.

[0024] In any embodiment, the thickness of the current collector is 2μm-13μm.

[0025] In any embodiment, the tensile strength of the current collector is 1050 MPa-1500 MPa. The high tensile strength of the current collector reduces the likelihood of electrode cracking during cycling, providing a material basis for simultaneously improving the energy density and cycle life of secondary batteries.

[0026] A second aspect of this application provides an electrode including the current collector provided in the first aspect of this application.

[0027] In any embodiment, the electrode is a negative electrode, the negative electrode includes a negative electrode film layer disposed on at least one side of the current collector, the negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material.

[0028] Silicon-based materials possess high specific capacity but also exhibit a large expansion rate during charge-discharge cycles. The secondary battery in this embodiment mitigates the problem of premature electrode breakage during cycling caused by silicon-based material expansion through a high-strength current collector, thus enabling the secondary battery to simultaneously achieve high energy density and good cycle stability.

[0029] In any embodiment, based on the total mass of the negative electrode film, the mass content of the silicon-based material is greater than or equal to 30%.

[0030] The secondary battery of this application embodiment is applicable to high-silicon systems, which helps to further improve the energy density per unit mass of the secondary battery.

[0031] In any embodiment, based on the total mass of the negative electrode film, the mass content of silicon element is greater than or equal to 15%.

[0032] A third aspect of this application provides a secondary battery, including the electrode provided in the second aspect of this application.

[0033] The fourth aspect of this application provides an electrical device, including the secondary battery provided in the third aspect of this application. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0035] Figure 1 This is a schematic cross-sectional view of the current collector according to an embodiment of this application;

[0036] Figure 2 This is a schematic diagram of one embodiment of the secondary battery of this application;

[0037] Figure 3 This is an exploded view of one embodiment of the secondary battery of this application;

[0038] Figure 4 This is a schematic diagram of one embodiment of the battery module of this application;

[0039] Figure 5 This is a schematic diagram of one embodiment of the battery pack of this application;

[0040] Figure 6 yes Figure 5 An exploded view of an embodiment of the battery pack shown;

[0041] Figure 7 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in this application.

[0042] In the accompanying drawings, the figures may not be drawn to scale. The reference numerals are explained as follows: 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Secondary battery, 51 Housing, 52 Electrode assembly, 53 Cover plate, 10 Current collector, 102a First surface of the current collector, 102b Second surface of the current collector, 1021 First region of the current collector, 1022 Second region of the current collector, 1023 Third region of the current collector. Detailed Implementation

[0043] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the current collector, electrode, secondary battery, and power supply device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0044] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0046] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0047] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0049] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0050] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0051] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, such as the testing methods provided in this application.

[0052] Unless otherwise specified, in this application, the term "active ion" refers to ions that can be inserted and extracted back and forth between the positive and negative electrodes of a secondary battery, including but not limited to lithium ions.

[0053] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0054] As market demands for higher energy density in rechargeable batteries increase, the need to improve the quality of high-specific-capacity electrode materials to enhance the energy density per unit mass of rechargeable batteries is becoming increasingly urgent. However, electrode materials with high specific capacity (such as silicon-based materials) often also have high expansion rates. Large expansion of the electrode material increases the stress on the current collector, causing premature electrode breakage during cycling and deteriorating battery life. Studies have shown that while the application of nickel-iron-based current collectors in rechargeable batteries can delay electrode breakage, it still falls short of meeting the needs of high-specific-energy batteries, especially for high-silicon systems, where achieving a balance between battery energy density and cycle life remains difficult.

[0055] Based on this, the first aspect of this application provides a current collector comprising a nickel-iron-based alloy, the nickel-iron-based alloy comprising a first doping element, the first doping element being a non-metallic element, and the mass content of the first doping element being less than 10% based on the total mass of the nickel-iron-based alloy.

[0056] In this article, nickel-iron-based alloys refer to alloys whose main components are nickel and iron, with nickel and iron accounting for more than 90% of the alloy's mass.

[0057] The types and composition of elements in the current collector can be tested using methods known in the art, such as X-ray diffraction (XRD) and inductively coupled plasma spectroscopy (ICP) to determine the types of elements in the current collector, quantitative analysis of the element content in the current collector using ICP, and the mass content of the first dopant element is obtained by dividing the total mass of non-metallic elements by the mass of the nickel-iron-based alloy sample.

[0058] Doping with non-metallic elements helps to increase the nucleation rate of nickel-iron-based alloys, reduce the grain size of nickel-iron-based alloys, improve the strength of current collectors, and delay the time of current collector fracture during cycling. At the same time, non-metallic elements are lightweight, which is beneficial for further reducing the mass of current collectors and increasing the energy density per unit mass of secondary batteries. However, the addition of non-metallic elements will reduce the conductivity of current collectors. Controlling the mass content of the first dopant element to less than 10% is beneficial for balancing the strength and conductivity of current collectors and comprehensively improving the cycle life of secondary batteries.

[0059] In some embodiments, the first doping element includes at least one of phosphorus and boron.

[0060] By adding phosphorus and / or boron to nickel-iron based alloys, the mechanical strength and corrosion resistance of current collectors can be improved, thereby comprehensively enhancing the cycle life of current collectors.

[0061] In some embodiments, the mass content of the first dopant element is 0.1%-8% based on the mass of the nickel-iron-based alloy.

[0062] In some embodiments, based on the mass of the nickel-iron-based alloy, the mass content of the first dopant element can be selected as 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or any value range between the two.

[0063] Controlling the mass content of the first dopant element within a suitable range is beneficial to improving the tensile strength of the current collector while maintaining its good conductivity, thereby comprehensively improving the cycle life of the battery.

[0064] In some implementations, the current collector is in the form of a foil or sheet.

[0065] In some embodiments, the first doping element includes phosphorus, and the phosphorus content in the nickel-iron-based alloy is 0.5%-8% based on the mass of the alloy.

[0066] In some embodiments, based on the mass of the nickel-iron-based alloy, the mass content of phosphorus in the nickel-iron-based alloy can be selected as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or any value range between the two.

[0067] When the phosphorus content is within a suitable range, it can effectively improve the tensile strength and corrosion resistance of the current collector, reduce the risk of premature cracking of the electrode during cycling, and at the same time, the appropriate phosphorus content can also maintain the good conductivity of the current collector, thus comprehensively improving the cycle life of the battery.

[0068] In some embodiments, the first doping element includes phosphorus, and the phosphorus content in the nickel-iron-based alloy is 0.5%-5% based on the mass of the alloy.

[0069] In some embodiments, the first doping element includes boron, and the boron content in the nickel-iron-based alloy is 0.1%-6% based on the mass of the alloy.

[0070] In some embodiments, based on the mass of the nickel-iron-based alloy, the mass content of boron in the nickel-iron-based alloy can be selected as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 4.5%, 5%, 5.5%, 6%, or any value range between the two.

[0071] When the boron content is within a suitable range, it can effectively improve the tensile strength and corrosion resistance of the current collector, reduce the risk of premature cracking of the electrode during cycling, and at the same time, the appropriate boron content can also effectively maintain the conductivity of the current collector, thus comprehensively improving the cycle life of the battery.

[0072] In some embodiments, the first doping element includes boron, and the boron content in the nickel-iron-based alloy is 3%-6% based on the mass of the alloy.

[0073] In some embodiments, based on the mass of the nickel-iron-based alloy, the mass content of iron in the nickel-iron-based alloy is 40%-50%, and the mass content of nickel in the nickel-iron-based alloy is 50%-60%.

[0074] In some embodiments, based on the mass of the nickel-iron-based alloy, the mass content of iron in the nickel-iron-based alloy is 40%, 42%, 44%, 45%, 46%, 48%, 50%, or any value between the two.

[0075] In some embodiments, based on the mass of the nickel-iron-based alloy, the mass content of nickel in the nickel-iron-based alloy is 50%, 52%, 54%, 55%, 56%, 58%, 60%, or any value between the two.

[0076] When the mass content of iron and nickel is within the above range, the strength of the current collector can be improved while taking into account the plasticity and corrosion resistance of the current collector, thereby further improving the cycle stability of the secondary battery.

[0077] In some embodiments, the nickel-iron-based alloy comprises 40%-50% iron by mass, 50%-60% nickel by mass, 0.1%-8% of a first dopant element by mass, and impurities, wherein the mass content of the impurities is less than 6%.

[0078] In some embodiments, based on the mass of the nickel-iron-based alloy, the mass content of impurities in the nickel-iron-based alloy can be selected as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 4.5%, 5%, 5.5%, 5.9%, or any value range between the two.

[0079] In some embodiments, the average grain size of the grains in the current collector is 2nm-17nm.

[0080] The crystal size of the current collector was characterized by XRD, and the grain size was calculated using the following formula:

[0081] D = kλ / (βcosθ)

[0082] Where k is the Scherrer constant; λ is the X-ray wavelength; θ is the Bragg angle in rad; and β is the half-maximum width at half maximum. Since the (111) crystal plane has the highest diffraction peak intensity in nickel-iron alloys, the grain size of the current collector is calculated based on the (111) crystal plane.

[0083] In some embodiments, the average grain size of the grains in the current collector can be selected as 2nm, 4nm, 6nm, 8nm, 10nm, 12nm, 14nm, 15nm, 17nm or any value range between the two.

[0084] The current collector contains nanocrystalline structures with very small particle sizes. The nanocrystalline structure can improve the tensile strength and corrosion resistance of the current collector and reduce the possibility of premature cracking of the electrode during the cycle.

[0085] In some implementations, such as Figure 1 As shown, the current collector 10 has a first surface 102a and a second surface 102b opposite to each other. The thickness of the current collector is denoted as H. The region from the first surface 102a to a thickness of 0.2H is denoted as the first region 1021 of the current collector. The region from the first surface 102a to a thickness of 0.4H-0.6H is denoted as the second region 1022 of the current collector. The region from the second surface 102b to a thickness of 0.2H is denoted as the third region 1023 of the current collector. The range of the mass content of the first dopant element in the first region, the mass content of the first dopant element in the second region, and the mass content of the first dopant element in the third region is less than or equal to 3%.

[0086] The range of mass content of the first dopant element phosphorus and / or boron in different regions can be tested by methods known in the art. As an example, the current collector is cut under plasma along a direction perpendicular to the surface of the current collector to obtain a cross-section of the current collector. The mass content of the first dopant element in different regions is tested using energy dispersive spectroscopy (EDS) under a scanning electron microscope (SEM) to determine the mass content of the first dopant element in different regions. The maximum value minus the minimum value of the mass content of the same dopant element in each region obtained by the test is taken as the range of the mass content of the first dopant element.

[0087] In some embodiments, the range of the mass content of the first doped element in the first region, the mass content of the first doped element in the second region, and the mass content of the first doped element in the third region can be selected as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or any value range between the two.

[0088] The small range of mass content variation of the first dopant element in different regions of the current collector indicates that the distribution of phosphorus or boron elements in different regions of the current collector is highly uniform, which improves the overall mechanical strength of the current collector, reduces the possibility of electrode cracking during cycling, and helps to improve the reliability of the current collector during cycling.

[0089] In some embodiments, the thickness of the current collector is 2 μm-13 μm.

[0090] In some embodiments, the thickness of the current collector can be selected as 2μm, 5μm, 6μm, 7μm, 10μm, 12μm, 13μm or any value range between the two.

[0091] In some embodiments, the tensile strength of the current collector is 1050 MPa-1500 MPa.

[0092] In this paper, the term "tensile strength" refers to the maximum load-bearing capacity of a specimen when it is subjected to continuous loading until it breaks.

[0093] In some embodiments, the tensile strength of the current collector can be selected as 1050MPa, 1100MPa, 1200MPa, 1300MPa, 1400MPa, 1500MPa or any value range between the two.

[0094] In this application, the tensile strength of the current collector can be tested using methods known in the art, for example as follows: using an Instron tensile testing machine (INSTRON 3343), a current collector specimen with a length of 150 mm and a width of 15 mm is stretched at a tensile speed of 2 mm / min under a gauge length of 50 mm, and the tensile curve is measured. The tensile strength of the current collector is calculated based on the maximum tensile force in the tensile curve. Each specimen is measured in parallel 10 times, and the average value is calculated as the tensile strength of the specimen.

[0095] The current collector has high tensile strength, which can reduce the possibility of electrode cracking during cycling, providing a material basis for the simultaneous improvement of energy density and cycle life of secondary batteries.

[0096] In some implementations, the current collector can be obtained by rolling, metallurgical sintering or electrodeposition.

[0097] In some embodiments, the current collector is prepared by electrodeposition.

[0098] Polaroid

[0099] A second aspect of this application provides an electrode, which includes a current collector in any embodiment.

[0100] In some implementations, the electrode is a positive electrode and the current collector is a positive current collector.

[0101] In some implementations, the electrode is a negative electrode and the current collector is a negative current collector.

[0102] In some embodiments, the electrode is a negative electrode, which includes a negative electrode film layer disposed on at least one side of the current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including a silicon-based material.

[0103] In some embodiments, the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials.

[0104] Silicon-based materials possess high specific capacity but also exhibit a large expansion rate during charge-discharge cycles. The secondary battery in this embodiment mitigates the problem of premature electrode breakage during cycling caused by silicon-based material expansion through a high-strength current collector, thus enabling the secondary battery to simultaneously achieve high energy density and good cycle stability.

[0105] In some embodiments, the silicon-based material accounts for more than or equal to 30% of the total mass of the negative electrode film.

[0106] In some embodiments, based on the total mass of the negative electrode film, the mass content of the silicon-based material can be selected as 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or any value range between the two.

[0107] The secondary battery of this application embodiment is applicable to high-silicon systems, which helps to further improve the energy density per unit mass of the secondary battery.

[0108] In some embodiments, the silicon content is greater than or equal to 15% based on the total mass of the negative electrode film.

[0109] In some embodiments, based on the total mass of the negative electrode film, the mass content of silicon can be selected as 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or any value between the two.

[0110] Based on the total mass of the negative electrode film, the mass content of silicon can be tested using any method known in the art. As an example, inductively coupled plasma spectrometry (ICP) is used to test the elements in the negative electrode film.

[0111] Secondary batteries

[0112] A third aspect of this application also provides a secondary battery, including the electrode provided in the second aspect of this application.

[0113] The secondary battery can be in the form of a single battery cell, a battery module, or a battery pack.

[0114] This application does not impose any particular limitation on the type of secondary battery; for example, the secondary battery can be a lithium-ion battery. Typically, a secondary battery includes a positive electrode, a negative electrode, and an electrolyte. During the charging and discharging process of the secondary battery, active ions repeatedly insert and extract between the positive and negative electrode, and the electrolyte acts as a conductor for these active ions. This application does not impose any particular limitation on the type of electrolyte, which can be selected according to actual needs. For example, the electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions). Secondary batteries using electrolyte solutions, and some secondary batteries using solid electrolytes, may also include a separator membrane disposed between the positive and negative electrode to provide isolation.

[0115] [Positive electrode plate]

[0116] In some embodiments, the positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0117] The positive electrode film typically comprises a positive electrode active material, an optional binder, and an optional conductive agent. The positive electrode film is typically formed by coating a positive electrode slurry onto the positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP), but is not limited to this. As an example, the binder used for the positive electrode film may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. As an example, the conductive agent used for the positive electrode film includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0118] The positive electrode active material may be a positive electrode active material known in the art for use in secondary batteries.

[0119] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of the lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of the lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds.

[0120] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material for the lithium-ion battery may include a lithium transition metal oxide having a general formula of Li 0.2 , 0.5 Ni b Co c M d O e A f and one or more of its modified compounds. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0121] In some embodiments, by way of example, the positive electrode active material for the lithium-ion battery may include one or more of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0122] In this application, the modified compounds of the above-mentioned positive electrode active materials may be those that have undergone doping modification and / or surface coating modification of the positive electrode active materials.

[0123] The positive electrode film is typically formed by coating a positive electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing positive electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0124] The positive electrode sheet does not exclude other additional functional layers besides the positive electrode film layer. For example, in some embodiments, the positive electrode sheet of this application further includes a conductive undercoating layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the positive current collector and the positive electrode film layer and disposed on the surface of the positive current collector; in some embodiments, the positive electrode sheet of this application further includes a protective layer covering the surface of the positive electrode film layer.

[0125] [Negative electrode plate]

[0126] The negative electrode includes a negative current collector and a negative electrode film layer optionally disposed on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material.

[0127] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0128] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0129] In some embodiments, the negative electrode film layer comprises a negative electrode active material. In some embodiments, the negative electrode active material includes, but is not limited to, one or more of conventional natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.

[0130] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0131] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0132] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0133] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0134] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector; in some embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0135] [Electrolytes]

[0136] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0137] The type of electrolyte salt is not specifically limited and can be selected according to actual needs.

[0138] When the secondary battery of this application is a lithium-ion battery, as an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0139] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl ester carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0140] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance characteristics of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high-temperature performance of the secondary battery, and additives that improve the low-temperature power performance of the secondary battery.

[0141] [Isolation membrane]

[0142] This application does not impose any particular restrictions on the type of separator membrane; any known porous separator membrane with good chemical and mechanical stability can be selected.

[0143] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0144] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process or a stacking process.

[0145] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0146] In some embodiments, the outer packaging may be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging may also be a flexible package, such as a pouch. The material of the flexible package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0147] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. Figure 2 This is an example of a square-structured secondary battery 5.

[0148] In some embodiments, such as Figure 3 As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be adjusted according to requirements.

[0149] The method for preparing the secondary battery described in this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a secondary battery. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding or stacking process. The electrode assembly is then placed in an outer packaging, dried, and injected with an electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0150] In some embodiments of this application, the secondary battery according to this application can be assembled into a battery module. The number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0151] Figure 4 This is a schematic diagram of battery module 4 as an example. Figure 4 As shown, in battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0152] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0153] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0154] Figure 5 and Figure 6 This is a schematic diagram of battery pack 1 as an example. Figure 5 and Figure 6 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0155] Electrical appliances

[0156] This application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the third aspect of this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, mobile devices (e.g., mobile phones, tablets, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0157] The electrical device can be equipped with a secondary battery, battery module, or battery pack according to its usage requirements.

[0158] Figure 7 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0159] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0160] Example

[0161] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0162] Example 1

[0163] (1) Preparation of negative electrode current collector

[0164] The negative electrode current collector is prepared by electrodeposition.

[0165] The electroplating solution contains 100 g / L NiSO4·6H2O; 105 g / L FeSO4·7H2O; and C2H 10 The BN content is 0.25 g / L; the ammonium citrate content is 100 g / L; the surfactant is sodium dodecyl sulfate, with a content of 2.0 g / L; the pH value of the electroplating solution is 3.1, and the electrodeposition temperature is 45℃. The deposition current is 0.4 A / cm. 2 The electrodeposition time is 30 minutes. The anode material used for electroplating is foil mainly composed of iron and nickel, and the cathode material is titanium alloy. During the electroplating process, nickel, iron, and boron elements will be deposited on the surface of the titanium alloy. After the deposition is completed, the coating is peeled off from the titanium alloy to obtain the negative electrode current collector, which is 7 μm in diameter.

[0166] (2) Battery manufacturing

[0167] The positive electrode active material NCM (811), conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) were dissolved in the solvent N-methylpyrrolidone (NMP) at a weight ratio of 96%:2%:2% and thoroughly mixed to obtain a positive electrode slurry. The positive electrode slurry was then uniformly coated on both sides of the positive electrode current collector aluminum foil, and then dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0168] The negative electrode active material, artificial silicon carbide, graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water in a weight ratio of 43.5:50:1.8:3.5:1.2 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is then uniformly coated onto the negative electrode current collector once or multiple times, dried to obtain a negative electrode film, and then cold-pressed and slit to obtain a negative electrode sheet.

[0169] In an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), organic solvents ethylene carbonate, diethyl carbonate, and dimethyl carbonate were mixed uniformly in a mass ratio of 1:1:1. Then, LiPF6 lithium salt was mixed with the mixed solvents to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0170] A polyethylene film with a thickness of 13 μm was used as the isolation membrane.

[0171] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The cells are then wound to obtain a wound battery cell. The wound battery cell is placed in an outer packaging shell, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium-ion battery is obtained.

[0172] Examples 2-5

[0173] The preparation methods of Examples 2-5 are basically the same as those of Example 1, except that the C2H content in the electroplating solution is adjusted. 10 The BN content, in turn, alters the mass content of boron, as follows:

[0174] Example 2: C2H in electroplating solution 10 The BN content is 1.5 g / L.

[0175] Example 3: C2H in electroplating solution 10 The BN content is 7.5 g / L.

[0176] Example 4: C2H in electroplating solution 10 The BN content is 10.5 g / L.

[0177] Example 5: C2H in electroplating solution 10 The BN content is 14.5 g / L.

[0178] Example 6

[0179] The preparation method of Example 6 is basically the same as that of Example 1, except that the composition of the electroplating solution is changed, as follows:

[0180] The electroplating solution contains 100 g / L NiSO4·6H2O, 105 g / L FeSO4·7H2O, 0.15 g / L NaH2PO2·H2O, 100 g / L ammonium citrate, and sodium dodecyl sulfate as the surfactant at 2.0 g / L.

[0181] Examples 7-10

[0182] The preparation methods of Examples 7-10 are basically the same as those of Example 6, except that the content of NaH2PO2·H2O in the electroplating solution is adjusted, as follows:

[0183] Example 7: The content of NaH2PO2·H2O in the electroplating solution is 0.8 g / L.

[0184] Example 8: The content of NaH2PO2·H2O in the electroplating solution is 4.0 g / L.

[0185] Example 9: The content of NaH2PO2·H2O in the electroplating solution is 7.5 g / L.

[0186] Example 10: The content of NaH2PO2·H2O in the electroplating solution is 12.5 g / L.

[0187] Example 11

[0188] The preparation method of Example 11 is basically the same as that of Example 1, except that the content of each component in the electroplating solution is adjusted, thereby changing the mass content of nickel, boron and iron, as detailed below:

[0189] Example 11: The electroplating solution contained 100 g / L NiSO4·6H2O, 97 g / L FeSO4·7H2O, and C2H 10 The BN content is 7 g / L, and the other parameters are the same as in Example 1.

[0190] Example 12

[0191] The preparation method of Example 12 is basically the same as that of Example 11, except that the preparation method of the negative electrode current collector is changed, as follows:

[0192] The current collector obtained in Example 11 was subjected to high-temperature treatment at 500°C for 2 hours to obtain the current collector of Example 12.

[0193] Comparative Example 1

[0194] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the negative electrode current collector is an iron-nickel alloy, as shown in Table 1.

[0195] Comparative Example 2

[0196] The preparation method of Comparative Example 2 is basically the same as that of Example 6, except that the content of FeSO4·7H2O and NaH2PO2·H2O in the electroplating solution is adjusted, thereby changing the mass content of phosphorus, as detailed below:

[0197] Comparative Example 2: The content of FeSO4·7H2O in the electroplating solution was 85 g / L, and the content of NaH2PO2·H2O was 15 g / L.

[0198] Performance testing

[0199] (1) Battery cycle count test

[0200] At 25°C, the secondary batteries prepared in each embodiment and comparative example were charged at a constant current rate of 0.5C to the charging cutoff voltage of 4.25V, then charged at a constant voltage rate to a current of 0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.5C to the discharge cutoff voltage of 2.5V, allowed to stand for 5 minutes. This constitutes one charge-discharge cycle. The capacity of the first discharge process is recorded as C1. The batteries were then subjected to cyclic charge-discharge tests in this manner until the capacity of the nth discharge process reached 0.8C1, at which point the cycle was terminated, and the number of cycles at this point was recorded as the cycle life of the battery at 25°C.

[0201] (2) Corrosion current density

[0202] Characterization was performed using Tafel polarization curve analysis. The polarization curves were measured using a standard three-electrode system with the sample under test (working area 1 cm²). 2 The electrode used was a platinum sheet as the working electrode, a saturated calomel electrode as the auxiliary electrode, and a saturated calomel electrode as the reference electrode. The electrolyte was a 3.5% NaCl solution. The sample was immersed in the electrolyte for 2 hours. After the open-circuit potential stabilized, the polarization curve of the sample was measured at a scan rate of 1.5 mV / s. The corrosion current density of the sample was calculated by fitting the Tafel curve using an electrochemical workstation.

[0203] (3) Room temperature resistivity of the current collector

[0204] The room temperature resistivity of the current collector is mainly tested using the four-probe method. The current collector to be tested is cut into 10mm × 60mm pieces and placed on a four-probe resistivity meter to obtain the room temperature resistivity of the current collector.

[0205] Test Results

[0206] Table 1

[0207]

[0208]

[0209] The current collector in Embodiments 1-12 of this application includes a nickel-iron-based alloy, wherein the nickel-iron-based alloy includes a first doping element, the first doping element is a non-metallic element, and the mass content of the first doping element is less than 10%.

[0210] As can be seen from the comparison between Examples 1-12 and Comparative Example 1, the current collector in the embodiments of this application has a better cycle life compared with the traditional nickel-iron-based alloy current collector.

[0211] As can be seen from the comparison between Examples 1-12 and Comparative Example 2, controlling the mass content of the first dopant element in the current collector to be 0.1%-8% can take into account both the tensile strength and resistivity of the current collector, thereby comprehensively improving the battery life.

[0212] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A current collector, characterized in that, The current collector comprises a nickel-iron-based alloy, the nickel-iron-based alloy comprising a first doping element, the first doping element being a non-metallic element, and the mass content of the first doping element being less than 10% based on the total mass of the nickel-iron-based alloy.

2. The current collector according to claim 1, characterized in that, The first doping element includes at least one of phosphorus and boron.

3. The current collector according to claim 1 or 2, characterized in that, Based on the mass of the nickel-iron-based alloy, the mass content of the first dopant element is 0.1%-8%.

4. The current collector according to any one of claims 1 to 3, characterized in that, The first doping element includes phosphorus, and the mass content of phosphorus in the nickel-iron-based alloy is 0.5%-8% based on the mass of the nickel-iron-based alloy.

5. The current collector according to any one of claims 1 to 3, characterized in that, The first doping element includes phosphorus, and the mass content of phosphorus in the nickel-iron-based alloy is 0.5%-5% based on the mass of the nickel-iron-based alloy.

6. The current collector according to any one of claims 1 to 5, characterized in that, The first doping element includes boron, and the mass content of boron in the nickel-iron-based alloy is 0.1%-6% based on the mass of the alloy.

7. The current collector according to any one of claims 1 to 5, characterized in that, The first doping element includes boron, and the boron content in the nickel-iron-based alloy is 3%-6% based on the mass of the alloy.

8. The current collector according to any one of claims 1 to 7, characterized in that, Based on the mass of the nickel-iron-based alloy, the mass content of iron in the nickel-iron-based alloy is 40%-50%, and the mass content of nickel in the nickel-iron-based alloy is 50%-60%.

9. The current collector according to any one of claims 1 to 8, characterized in that, The nickel-iron-based alloy consists of 40%-50% iron, 50%-60% nickel, 0.1%-8% of a first dopant element, and impurities, wherein the mass content of the impurities is less than 6%.

10. The current collector according to any one of claims 1 to 9, characterized in that, The average grain size of the crystals in the current collector is 2nm-17nm.

11. The current collector according to any one of claims 1 to 10, characterized in that, The current collector has a first surface and a second surface, the thickness of the current collector is denoted as H, the region from the first surface of the current collector to a thickness of 0.2H is denoted as the first region of the current collector, the region from the first surface of the current collector to a thickness of 0.4H-0.6H is denoted as the second region of the current collector, and the region from the second surface of the current collector to a thickness of 0.2H is denoted as the third region of the current collector. The range of the mass content of the first dopant element in the first region, the mass content of the first dopant element in the second region, and the mass content of the first dopant element in the third region is less than or equal to 3%.

12. The current collector according to any one of claims 1 to 11, characterized in that, The thickness of the current collector is 2μm-13μm.

13. The current collector according to any one of claims 1 to 12, characterized in that, The tensile strength of the current collector is 1050MPa-1500MPa.

14. An electrode sheet, characterized in that, The electrode comprises the current collector according to any one of claims 1 to 13.

15. The electrode sheet according to claim 14, characterized in that, The electrode is a negative electrode, and the negative electrode includes a negative electrode film layer disposed on at least one side of the current collector. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material.

16. The electrode sheet according to claim 15, characterized in that, Based on the total mass of the negative electrode film, the mass content of the silicon-based material is greater than or equal to 30%.

17. The electrode sheet according to any one of claims 14 to 16, characterized in that, Based on the total mass of the negative electrode film, the mass content of silicon is greater than or equal to 15%.

18. A secondary battery, characterized in that, Includes the electrode sheet according to any one of claims 14-17.

19. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 18.

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