Current collector, electrode sheet, secondary battery and electric device

Abstract

The present application provides a current collector, an electrode sheet, 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 based on the total mass of the nickel-iron-based alloy, the mass content of the first doping element is less than 10%.

Description

Current collector, electrode sheet, secondary battery, and electric device

[0001] Related applications

[0002] The present application claims priority to the Chinese patent application No. 2024111240229 filed on August 15, 2024, and entitled "Current collector, electrode sheet, secondary battery, and electric device", the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present application belongs to the technical field of batteries, and specifically relates to a current collector, an electrode sheet, a secondary battery, and an electric device. BACKGROUND

[0004] In recent years, secondary batteries are widely used in energy storage power systems such as hydroelectric, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc.

[0005] With the increasing demand for energy density of secondary batteries, how to balance the energy density and cycle stability of secondary batteries has become a technical problem to be solved in the field. SUMMARY

[0006] The present application is made in view of the above-mentioned problem, and aims to provide a current collector, an electrode sheet, a secondary battery, and an electric device, so as to balance the energy density and cycle stability of the secondary battery.

[0007] The first aspect of the present application provides a current collector, the 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.

[0008] The doping of the non-metallic element helps to increase the nucleation rate of the nickel-iron-based alloy, reduce the grain size of the nickel-iron-based alloy, improve the strength of the current collector, and delay the time of fracture of the current collector during the cycle process. At the same time, the non-metallic element is light in quality, which is conducive to further reducing the mass of the current collector and improving the energy density per unit mass of the secondary battery. However, the addition of the non-metallic element will cause the conductivity of the current collector to decrease, and controlling the mass content of the first doping element to be less than 10% is conducive to balancing the strength and conductivity of the current collector, and comprehensively improving the cycle life of the secondary battery.

[0009] In any embodiment, the first doping element comprises at least one of phosphorus element and boron element.

[0010] By adding phosphorus element and / or boron element in the nickel-iron-based alloy, the mechanical strength and corrosion resistance of the current collector can be improved, and the cycle life of the current collector can be improved comprehensively.

[0011] In any embodiment, the mass content of the first doping element is 0.1%-8% based on the mass of the nickel-iron-based alloy.

[0012] Controlling the mass content of the first doping element within a suitable range is conducive to improving the tensile strength of the current collector while maintaining good electrical conductivity of the current collector, and comprehensively improving the cycle life of the battery.

[0013] In any embodiment, the first doping element includes phosphorus element, and the mass content of the phosphorus element in the nickel-iron-based alloy is 0.5%-8% based on the mass of the nickel-iron-based alloy.

[0014] The mass content of the phosphorus element within a suitable range can effectively improve the tensile strength and corrosion resistance of the current collector, reduce the risk of premature cracking of the pole piece during the cycle process, and the suitable mass content of the phosphorus element can also maintain good electrical conductivity of the current collector, thereby comprehensively improving the cycle life of the battery.

[0015] In any embodiment, the first doping element includes phosphorus element, and the mass content of the phosphorus element in the nickel-iron-based alloy is 0.5%-5% based on the mass of the nickel-iron-based alloy.

[0016] In any embodiment, the first doping element includes boron element, and the mass content of the boron element in the nickel-iron-based alloy is 0.1%-6% based on the mass of the nickel-iron-based alloy.

[0017] The mass content of the boron element within a suitable range can effectively improve the tensile strength and corrosion resistance of the current collector, reduce the risk of premature cracking of the pole piece during the cycle process, and the suitable mass content of the boron element can also effectively maintain the electrical conductivity of the current collector, thereby comprehensively improving the cycle life of the battery.

[0018] In any embodiment, the first doping element includes boron element, and the mass content of the boron element in the nickel-iron-based alloy is 3%-6% based on the mass of the nickel-iron-based alloy.

[0019] In any embodiment, the mass content of iron element in the nickel-iron-based alloy is 40%-49.9% based on the mass of the nickel-iron-based alloy, and the mass content of nickel element in the nickel-iron-based alloy is 50%-59.9% based on the mass of the nickel-iron-based alloy.

[0020] The mass content of iron element and nickel element within the above range can improve the strength of the current collector while taking into account the plasticity and corrosion resistance of the current collector, thereby further improving the cycle stability of the secondary battery.

[0021] In any embodiment, the ferronickel-based alloy consists of iron with a mass content of 40%-49.9%, nickel with a mass content of 50%-59.9%, the first doping element with a mass content of 0.1%-8%, and impurities with a mass content less than 6%.

[0022] In any embodiment, the average particle size of the crystal grains in the current collector is 2 nm-17 nm.

[0023] The crystal grains in the current collector are nano-crystalline structures with very small particle sizes, which can improve the tensile strength and corrosion resistance of the current collector and reduce the possibility of premature cracking of the pole piece during the cycle process.

[0024] In any embodiment, the current collector has opposite first and second surfaces, the thickness of the current collector is denoted as H, the region within the thickness range of 0.2H from the first surface of the current collector is denoted as the first region of the current collector, the region within the thickness range of 0.4H-0.6H from the first surface of the current collector is denoted as the second region of the current collector, the region within the thickness range of 0.2H from the second surface of the current collector is denoted as the third region of the current collector, and the range of the mass content of the first doping element in the first region, the range of the mass content of the first doping element in the second region, and the range of the mass content of the first doping element in the third region is less than or equal to 3%.

[0025] The range of the mass content of the first doping element in different regions of the current collector within a smaller range indicates that the distribution of phosphorus or boron elements in different regions of the current collector has high uniformity, improves the overall mechanical strength of the current collector, reduces the possibility of cracking of the pole piece during the cycle process, and is beneficial to improve the reliability of the current collector during the cycle process.

[0026] In any embodiment, the thickness of the current collector is 2 μm-13 μm.

[0027] In any embodiment, the tensile strength of the current collector is 1050 MPa-1500 MPa. The current collector has high tensile strength, which can reduce the possibility of cracking of the pole piece during the cycle process, and provides a material basis for the synchronous improvement of the energy density and cycle life of the secondary battery.

[0028] The second aspect of the present application provides a pole piece comprising the current collector provided by the first aspect of the present application.

[0029] In any embodiment, the pole piece is a negative pole piece, the negative pole piece comprises a negative film layer arranged on at least one side of the current collector, the negative film layer comprises a negative active material, and the negative active material comprises a silicon-based material.

[0030] Silicon-based materials have high specific capacity, while having a large expansion rate during the cyclic charging and discharging process. The secondary battery in the embodiments of the present application can alleviate the problem of premature failure of the electrode sheet caused by the expansion of the silicon-based material during the cycle process by using a high-strength current collector, so that the secondary battery has both high energy density and good cycle stability.

[0031] In any embodiment, the mass content of the silicon-based material is greater than or equal to 30% based on the total mass of the negative electrode film layer.

[0032] The secondary battery of the embodiments of the present application can be applied to a high-silicon system, which helps to further improve the energy density per unit mass of the secondary battery.

[0033] In any embodiment, the mass content of the silicon-based material is greater than or equal to 30% based on the total mass of the negative electrode film layer.

[0034] The third aspect of the present application provides a secondary battery comprising the electrode sheet provided by the second aspect of the present application.

[0035] The fourth aspect of the present application provides an electrical device comprising the secondary battery provided by the third aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0037] FIG. 1 is a cross-sectional view of a current collector according to an embodiment of the present application;

[0038] FIG. 2 is a schematic view of an embodiment of a secondary battery according to the present application;

[0039] FIG. 3 is an exploded schematic view of an embodiment of a secondary battery according to the present application;

[0040] FIG. 4 is a schematic view of an embodiment of a battery module according to the present application;

[0041] FIG. 5 is a schematic view of an embodiment of a battery pack according to the present application;

[0042] FIG. 6 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 5;

[0043] FIG. 7 is a schematic view of an embodiment of an electrical device comprising a secondary battery according to the present application as a power supply.

[0044] In the drawings, the drawings are not necessarily drawn to scale. Reference numerals are explained below: 1, battery pack, 2, upper case, 3, lower case, 4, battery module, 5, secondary battery, 51, case, 52, electrode assembly, 53, cover plate, 10, current collector, 102a, first surface of current collector, 102b, second surface of current collector, 1021, first region of current collector, 1022, second region of current collector, 1023, third region of current collector, 6, electric device. DETAILED DESCRIPTION

[0045] Hereinafter, specific embodiments of the current collector, electrode sheet, secondary battery, and electric device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed descriptions are omitted. For example, there can be cases where detailed descriptions of matters well known in the art, repetitive descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0046] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., 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 particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every numerical value that is contained within the range, wherein a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shorthand manner of describing those numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0048] If not particularly specified, all the technical features and optional technical features in the present application can be combined with each other to form new technical solutions, and such technical solutions shall be considered to be included in the disclosure of the present application.

[0049] If not particularly specified, all the steps in the present application can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0050] If not particularly specified, the terms "comprise" and "include" mentioned in the present application are open-ended and can also be closed-ended. For example, the terms "comprise" and "include" can mean that other components not listed can also be included, or only the listed components can be included.

[0051] If not particularly specified, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any one of the following conditions satisfies the condition "A or B": 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).

[0052] If not particularly specified, the terms used in the present application have the commonly understood meanings understood by those skilled in the art.

[0053] If not particularly specified, the values of the parameters mentioned in the present application can be measured by various test methods commonly used in the art, for example, can be measured according to the test methods given in the present application.

[0054] If not particularly specified, in the present application, the term "active ion" refers to an ion that can be reversibly inserted and extracted between the positive and negative electrodes of a secondary battery, including but not limited to lithium ion.

[0055] In the present application, the terms "a plurality of" and "a plurality of" mean two or more.

[0056] With the increasing requirement of energy density of secondary batteries, it is more and more urgent to improve the quality of high specific capacity electrode materials in batteries to increase the unit mass energy density of secondary batteries. However, electrode materials with high specific capacity (such as silicon-based materials) often have high expansion rate at the same time, and the large expansion of electrode materials will increase the stress on the current collector, causing the electrode sheet to break prematurely during the cycle process, and deteriorating the battery life. Studies have shown that the application of nickel-iron-based current collector in secondary batteries can delay the time of electrode sheet fracture, but it is still difficult to meet the needs of high specific energy batteries, especially for high-silicon systems, it is still difficult to achieve the balance between battery energy density and cycle life.

[0057] Therefore, in a first aspect, the present application provides a current collector, the 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.

[0058] In this document, the nickel-iron-based alloy refers to an alloy mainly composed of nickel and iron, and the elemental mass of nickel and iron accounts for more than 90% of the mass of the alloy, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 98.4%, 99%, 99.5%, 99.9%, or a range formed by any two of the above values, and optionally 90% to 99.9%.

[0059] The types and compositions of elements in the current collector can be tested by methods known in the art, for example, by X-ray diffractometer (XRD), inductively coupled plasma spectrometer (ICP) to determine the types of elements in the current collector, by inductively coupled plasma spectrometer (ICP) to quantitatively analyze the content of elements in the current collector, and by dividing the total mass of non-metallic elements by the sample mass of the nickel-iron-based alloy as the mass content of the first doping element.

[0060] The doping of non-metallic elements helps to improve the nucleation rate of the nickel-iron-based alloy, reduce the grain size of the nickel-iron-based alloy, improve the strength of the current collector, and delay the time of fracture of the current collector during the cycle process; at the same time, the non-metallic elements are light in quality, which is beneficial to further reduce the mass of the current collector and improve the unit mass energy density of the secondary battery. However, the addition of non-metallic elements will cause the conductivity of the current collector to decrease, and controlling the mass content of the first doping element to be less than 10% is beneficial to balance the strength and conductivity of the current collector, and comprehensively improve the cycle life of the secondary battery.

[0061] In some embodiments, the first doping element comprises at least one of phosphorus element and boron element.

[0062] By adding phosphorus element and / or boron element in the nickel-iron-based alloy, the mechanical strength and corrosion resistance of the current collector can be improved, and the cycle life of the current collector can be improved comprehensively.

[0063] In some embodiments, the mass content of the first doping element is 0.1%-8% based on the mass of the nickel-iron-based alloy.

[0064] In some embodiments, the mass content of the first doping element can be selected as 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or a numerical range between any two of them, based on the mass of the nickel-iron-based alloy.

[0065] Controlling the mass content of the first doping element within a suitable range is conducive to improving the tensile strength of the current collector while maintaining good electrical conductivity of the current collector, and comprehensively improving the cycle life of the battery.

[0066] In some embodiments, the current collector exists in the form of a foil or a sheet.

[0067] In some embodiments, the first doping element includes one or more of phosphorus element and boron element.

[0068] In some embodiments, the first doping element includes phosphorus element, and the mass content of the phosphorus element in the nickel-iron-based alloy is 0.5%-8% based on the mass of the nickel-iron-based alloy.

[0069] In some embodiments, the mass content of the phosphorus element in the nickel-iron-based alloy can be selected as 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, or a numerical range between any two of them, based on the mass of the nickel-iron-based alloy.

[0070] The mass content of the phosphorus element within a suitable range can effectively improve the tensile strength and corrosion resistance of the current collector, reduce the risk of premature cracking of the pole piece during the cycle process, and at the same time, the phosphorus element with a suitable mass content can also maintain good electrical conductivity of the current collector, and comprehensively improve the cycle life of the battery.

[0071] In some embodiments, the first doping element includes phosphorus element, and the mass content of the phosphorus element in the nickel-iron-based alloy is 0.5%-5% based on the mass of the nickel-iron-based alloy.

[0072] In some embodiments, the first doping element includes boron element, and the mass content of the boron element in the nickel-iron-based alloy is 0.1%-6% based on the mass of the nickel-iron-based alloy.

[0073] In some embodiments, the mass content of boron in the nickel-iron-based alloy is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 4.5%, 5%, 5.5%, 6%, or any numerical range between any two of the aforementioned values, based on the mass of the nickel-iron-based alloy.

[0074] The mass content of boron in the appropriate range can effectively improve the tensile strength and corrosion resistance of the current collector, reduce the risk of premature cracking of the pole piece during the cycle process, and the appropriate mass content of boron can also effectively maintain the electrical conductivity of the current collector, thereby improving the cycle life of the battery.

[0075] In some embodiments, the first doping element includes boron, and the mass content of boron in the nickel-iron-based alloy is 3%-6%, based on the mass of the nickel-iron-based alloy.

[0076] In some embodiments, the mass content of iron in the nickel-iron-based alloy is 40%-49.9%, and the mass content of nickel in the nickel-iron-based alloy is 50%-59.9%, based on the mass of the nickel-iron-based alloy.

[0077] In some embodiments, the mass content of iron in the nickel-iron-based alloy is 40%, 42%, 44%, 45%, 46%, 48%, 48.4%, 49%, 49.5%, 49.9%, or any numerical range between any two of the aforementioned values, based on the mass of the nickel-iron-based alloy. Further, the mass content of iron in the nickel-iron-based alloy is 40%-49%, based on the mass of the nickel-iron-based alloy; alternatively, the mass content of iron in the nickel-iron-based alloy is 40%-48.4%, based on the mass of the nickel-iron-based alloy.

[0078] In some embodiments, the mass content of nickel in the nickel-iron-based alloy is 50%, 52%, 54%, 55%, 56%, 58%, 59%, 59.5%, 59.9%, or any numerical range between any two of the aforementioned values, based on the mass of the nickel-iron-based alloy. Further, the mass content of nickel in the nickel-iron-based alloy is 50%-58%, based on the mass of the nickel-iron-based alloy.

[0079] The mass content of iron and nickel in the above range can improve the strength of the current collector while taking into account the plasticity and corrosion resistance of the current collector, thereby further improving the cycle stability of the secondary battery.

[0080] In some embodiments, the nickel-iron-based alloy is composed of iron with a mass content of 40%-49.9%, nickel with a mass content of 50%-59.9%, a first doping element with a mass content of 0.1%-8%, and impurities with a mass content of less than 6%.

[0081] In some embodiments, the mass content of impurities in the nickel-iron based alloy can be selected from 0.1%, 0.5%, 1%, 2%, 3%, 4%, 4.5%, 5%, 5.5%, 5.9%, or any numerical range between any two of the aforementioned values, based on the mass of the nickel-iron based alloy.

[0082] In some embodiments, the average particle size of the crystal grains in the current collector is 2-17 nm.

[0083] The crystal size of the current collector is characterized by XRD, and the grain size is calculated by the following formula: D=kλ / (βcosθ)

[0084] wherein k is the Scherrer constant; λ is the X-ray wavelength; θ is the Bragg angle, rad; and β is the half-peak width. Since the (111) crystal plane diffraction peak has the highest intensity in the nickel-iron based alloy, the grain size of the current collector is calculated based on the (111) crystal plane.

[0085] In some embodiments, the average particle size of the crystal grains in the current collector can be selected from 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 15 nm, 17 nm, or any numerical range between any two of the aforementioned values.

[0086] The crystal grains in the current collector are nano-crystalline structures with very small particle sizes, which can improve the tensile strength and corrosion resistance of the current collector and reduce the possibility of premature cracking of the electrode sheet during the cycle process.

[0087] In some embodiments, as shown in FIG. 1, the current collector 10 has opposite first and second surfaces 102a and 102b, and the thickness of the current collector is denoted as H. The region within the thickness range of 0.2H from the first surface 102a of the current collector is denoted as the first region 1021 of the current collector, the region within the thickness range of 0.4H-0.6H from the first surface 102a of the current collector is denoted as the second region 1022 of the current collector, and the region within the thickness range of 0.2H from the second surface 102b of the current collector is denoted as the third region 1023 of the current collector. The absolute difference between the mass content of the first doping element in the first region, the mass content of the first doping element in the second region, and the mass content of the first doping element in the third region is less than or equal to 3%.

[0088] The range of the mass content of the first doping element in different regions can be tested by methods known in the art. For example, the current collector is cut under plasma in a direction perpendicular to the surface of the current collector to obtain a cross section of the current collector, and the mass content of the first doping element in different regions is tested under a scanning electron microscope (SEM) using an energy dispersive spectrometer (EDS), and then the mass content of the first doping element in different regions is determined, and the maximum minus the minimum of the mass content of the same doping element in each region obtained by testing is taken as the range of the mass content of the first doping element.

[0089] In some embodiments, the range of the mass content of the first doping element in the first region, the mass content of the first doping element in the second region, and the mass content of the first doping element in the third region can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, or any numerical range between any two of them.

[0090] The range of the mass content of the first doping element in different regions of the current collector indicates that the distribution of phosphorus or boron elements in different regions of the current collector has high uniformity, improves the overall mechanical strength of the current collector, reduces the possibility of cracking of the pole piece during the cycle process, and is beneficial to improve the reliability of the current collector during the cycle process.

[0091] In some embodiments, the thickness of the current collector is 2 μm-13 μm.

[0092] In some embodiments, the thickness of the current collector can be 2 μm, 5 μm, 6 μm, 7 μm, 10 μm, 12 μm, 13 μm, or any numerical range between any two of them.

[0093] In some embodiments, the tensile strength of the current collector is 1050 MPa-1500 MPa.

[0094] In this paper, the term "tensile strength" refers to the maximum bearing strength of the sample when continuously loaded until the sample is pulled apart.

[0095] In some embodiments, the tensile strength of the current collector can be 1050 MPa, 1100 MPa, 1200 MPa, 1300 MPa, 1400 MPa, 1500 MPa, or any numerical range between any two of them.

[0096] In the present application, the tensile strength of the current collector can be tested by methods known in the art, for example: using an INSTRON 3343 tensile testing machine, stretching the current collector sample with a length of 150 mm and a width of 15 mm at a tensile speed of 2 mm / min under a gauge length of 50 mm, measuring the tensile curve, and calculating the tensile strength of the current collector based on the maximum tensile force in the tensile curve; each sample is measured in parallel for 10 times, and the average value is calculated as the tensile strength of the sample.

[0097] The current collector has high tensile strength, which can reduce the possibility of cracking of the pole piece during the cycle process, and provides a material basis for the synchronous improvement of the energy density and cycle life of the secondary battery.

[0098] In some embodiments, the current collector can be obtained by calendering, metallurgical sintering or electrodeposition.

[0099] In some embodiments, the current collector is prepared by electrodeposition.

[0100] Pole piece

[0101] The second aspect of the present application provides a pole piece, which comprises the current collector in any of the embodiments.

[0102] In some embodiments, the pole piece is a positive pole piece, and the current collector is a positive current collector.

[0103] In some embodiments, the pole piece is a negative pole piece, and the current collector is a negative current collector.

[0104] In some embodiments, the pole piece is a negative pole piece, and the negative pole piece comprises a negative film layer arranged on at least one side of the current collector, the negative film layer comprises a negative active material, and the negative active material comprises a silicon-based material.

[0105] In some embodiments, the silicon-based material can include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite and silicon alloy material.

[0106] The silicon-based material has high specific capacity, and at the same time has a large expansion rate during the cycle charging and discharging process. The secondary battery in the embodiments of the present application can slow down the problem of premature failure of the pole piece in the cycle process caused by the expansion of the silicon-based material through the high-strength current collector, so that the secondary battery has high energy density and good cycle stability at the same time.

[0107] In some embodiments, the mass content of the silicon-based material is greater than or equal to 30% based on the total mass of the negative film layer.

[0108] In some embodiments, the mass content of the silicon-based material can be selected from 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or any range between any two of the aforementioned values, based on the total mass of the negative electrode film layer.

[0109] The secondary battery according to the embodiments of the present application can be applied to a high-silicon system, which helps to further improve the energy density per unit mass of the secondary battery.

[0110] In some embodiments, the mass content of the silicon element can be greater than or equal to 15%, based on the total mass of the negative electrode film layer.

[0111] In some embodiments, the mass content of the silicon element can be selected from 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or any range between any two of the aforementioned values, based on the total mass of the negative electrode film layer.

[0112] The mass content of the silicon element, based on the total mass of the negative electrode film layer, can be determined by any known method in the art. For example, the inductively coupled plasma spectrometer (ICP) can be used to test the elements of the negative electrode film layer.

[0113] Secondary battery

[0114] The third aspect of the present application also provides a secondary battery, which comprises the electrode sheet according to the second aspect of the present application.

[0115] The secondary battery can be in the form of a battery cell, a battery module, or a battery pack.

[0116] The secondary battery according to the present application is not particularly limited, and can be, for example, a lithium-ion battery. Generally, the secondary battery comprises a positive electrode sheet, a negative electrode sheet, and an electrolyte. During the charging and discharging of the secondary battery, active ions are inserted into and extracted from the positive electrode sheet and the negative electrode sheet, and the electrolyte serves to conduct the active ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not particularly limited, and can be selected according to actual needs. For example, the electrolyte can be selected from at least one of a solid-state electrolyte and a liquid electrolyte (i.e., electrolyte solution). The secondary battery using the electrolyte solution, and some secondary batteries using the solid-state electrolyte, can further comprise a separator film, which is arranged between the positive electrode sheet and the negative electrode sheet, and serves to separate the positive electrode sheet and the negative electrode sheet.

[0117] [Positive electrode sheet]

[0118] In some embodiments, the positive electrode tab includes a positive current collector and a positive film layer disposed on at least one surface of the positive current collector. For example, the positive current collector has two surfaces opposite in the thickness direction of itself, and the positive film layer is disposed on either one or both of the two opposite surfaces of the positive current collector.

[0119] The positive film layer generally includes a positive active material, an optional binder, and an optional conductive agent. The positive film layer is generally formed by coating a positive slurry on the positive current collector, drying, and cold-pressing. The positive slurry is generally formed by dispersing and uniformly stirring a positive active material, an optional conductive agent, an optional binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto. As an example, the binder used in the positive film layer can include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. As an example, the conductive agent used in the positive film layer includes one or more of super P, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0120] The positive active material can employ a positive active material for a secondary battery known in the art.

[0121] When the secondary battery of the present application is a lithium ion battery, the positive active material can include, but is not limited to, one or more of a lithium-containing transition metal oxide, a lithium-containing phosphate, and a modified compound of each thereof. Examples of the lithium-containing transition metal oxide can 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 a modified compound of each thereof. Examples of the lithium-containing phosphate can include, but are not limited to, one or more of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and a modified compound of each thereof.

[0122] In some embodiments, in order to further improve the energy density of the secondary battery, the positive active material for a lithium ion battery can include a compound represented by the general formula Li a Ni b Co c M d O e A fOne or more of lithium transition metal oxides and their 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.

[0123] In some embodiments, by way of example, the positive electrode active material for a 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 0.1 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0124] In the present application, the modified compounds of the above positive electrode active materials may be doping modification and / or surface coating modification of the positive electrode active materials.

[0125] The positive electrode film layer is usually formed by coating a positive electrode paste on a negative electrode current collector and drying and cold pressing. The positive electrode paste is usually formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0126] The positive electrode sheet does not exclude other additional functional layers in addition to the positive electrode film layer. For example, in some embodiments, the positive electrode sheet described in the present application further includes a conductive bottom coating sandwiched between the positive electrode current collector and the positive electrode film layer and provided on the surface of the positive electrode current collector. For example, the conductive bottom coating is composed of a conductive agent and a binder; in some embodiments, the positive electrode sheet described in the present application further includes a protective layer covering the surface of the positive electrode film layer.

[0127] [Negative electrode sheet]

[0128] The negative electrode sheet includes a negative electrode current collector and, optionally, a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer includes a negative electrode active material.

[0129] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either one or both of the two surfaces of the negative electrode current collector.

[0130] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0131] In some embodiments, the negative electrode film layer includes 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 material, tin-based material, and lithium titanate. The tin-based material can include one or more of elemental tin, tin oxide, and tin alloy material.

[0132] In some embodiments, the negative electrode film layer can also optionally include a negative electrode conductive agent. The present application does not have a particular limitation on the type of the negative electrode conductive agent. As an example, the negative electrode conductive agent can include one or more of super P, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0133] In some embodiments, the negative electrode film layer can also optionally include a negative electrode binder. The present application does not have a particular limitation on the type of the negative electrode binder. As an example, the negative electrode binder can include one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0134] In some embodiments, the negative electrode film layer can also optionally include other auxiliary agents. As an example, the other auxiliary agents can include a thickening agent, such as sodium carboxymethyl cellulose (CMC), PTC thermistor material, etc.

[0135] The negative electrode film layer is generally formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0136] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab described in the present application further includes a conductive primer layer disposed on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer, for example, the conductive primer layer is composed of a conductive agent and a binder; in some embodiments, the negative electrode tab described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0137] [Electrolyte]

[0138] In some embodiments, the electrolyte adopts an electrolyte solution, and the electrolyte solution includes an electrolyte salt and a solvent.

[0139] The type of the electrolyte salt is not particularly limited and can be selected according to actual needs.

[0140] When the secondary battery of the present application is a lithium ion battery, as an example, the electrolyte salt can include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0141] The type of the solvent is not particularly limited and can be selected according to actual needs. In some embodiments, as an example, the solvent can include one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene 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).

[0142] In some embodiments, the electrolyte solution can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive capable of improving certain performance of the secondary battery, such as an additive capable of improving overcharge performance of the secondary battery, an additive capable of improving high-temperature performance of the secondary battery, an additive capable of improving low-temperature power performance of the secondary battery, and the like.

[0143] [Separator]

[0144] The type of the separator is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be used.

[0145] In some embodiments, the material of the separator can include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of the layers can be the same or different.

[0146] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly by a winding process or a stacking process.

[0147] In some embodiments, the secondary battery can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte solution.

[0148] In some embodiments, the outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package can also be a soft package, such as a pouch. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0149] The shape of the secondary battery is not particularly limited in the present application, and the secondary battery can be cylindrical, square, or any other shape. FIG. 2 shows a square structure secondary battery 5 as an example.

[0150] In some embodiments, as shown in FIG. 3, the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can 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. The electrolyte solution is impregnated in the electrode assembly 52. The number of the electrode assemblies 52 contained in the secondary battery 5 can be one or several, which can be adjusted according to requirements.

[0151] The preparation method of the secondary battery of the present application is known. In some embodiments, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte can be assembled to form the secondary battery. As an example, the positive electrode sheet, the separator, the negative electrode sheet can be formed into an electrode assembly through a winding process or a stacking process, the electrode assembly is placed in an outer package, the electrolyte is injected after drying, and the secondary battery is obtained through processes such as vacuum packaging, standing, formation, shaping, etc.

[0152] In some embodiments of the present application, the secondary battery according to the present application can be assembled into a battery module, and 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.

[0153] FIG. 4 is a schematic diagram of a battery module 4 as an example. As shown in FIG. 4, in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, other arbitrary arrangements can also be used. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0154] Optionally, the battery module 4 can further include a housing having an accommodation space, and the plurality of secondary batteries 5 are accommodated in the accommodation space.

[0155] In some embodiments, the above-mentioned battery module 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.

[0156] FIGS. 5 and 6 are schematic diagrams of a battery pack 1 as an example. As shown in FIGS. 5 and 6, the battery pack 1 can include a battery box and a plurality of battery modules 4 arranged in the battery box. The battery box includes an upper box body 2 and a lower box body 3, the upper box body 2 is used to cover the lower box body 3, and forms a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0157] Electric device

[0158] The present application also provides an electric device, which includes at least one of the secondary battery, the battery module or the battery pack provided by the third aspect of the present application. The secondary battery, the battery module or the battery pack can be used as a power source of the electric device, or can be used as an energy storage unit of the electric device. The electric device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.

[0159] The electric device can select a secondary battery, a battery module or a battery pack according to its use requirements.

[0160] FIG. 7 is a schematic view of an electric device as one example. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the demand of the electric device for high power and high energy density, a battery pack or a battery module can be used.

[0161] The electric device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The electric device generally requires thin and light, and a secondary battery can be used as a power source.

[0162] The following examples more specifically describe the present disclosure, which are merely illustrative and not limiting, as various modifications and changes in the examples will be obvious to those skilled in the art within the scope of the present disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further purification, and the instruments used in the examples are commercially available.

[0163] Example 1

[0164] (1) Preparation of the negative current collector

[0165] The negative current collector is prepared by electrodeposition.

[0166] The content of NiSO4·6H2O in the plating solution is 100 g / L; the content of FeSO4·7H2O is 105 g / L; the content of C2H 10 The content of BN is 0.25 g / L; the content of ammonium citrate is 100 g / L; the surfactant is sodium dodecyl sulfate, and the content is 2.0 g / L; the pH value of the plating solution is 3.1, and the temperature of electrodeposition is 45°C. The deposition current is 0.4 A / cm 2 The anode material used in plating is a foil mainly composed of iron and nickel, and the cathode material is titanium alloy. During plating, nickel, iron, and boron elements are deposited on the surface of the titanium alloy. After deposition, the plating layer is separated from the titanium alloy to obtain the negative current collector, which is 7 μm thick.

[0167] (2) Preparation of the battery

[0168] The positive active material NCM (811), the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methyl pyrrolidone (NMP) at a weight ratio of 96%:2%:2%, and after being fully stirred and mixed uniformly, a positive slurry is obtained. Then, the positive slurry is uniformly coated on the front and back surfaces of the positive current collector aluminum foil, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0169] The negative active material artificial silicon-carbon material, graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), thickening agent sodium carboxymethyl cellulose (CMC) are dissolved in solvent deionized water according to a weight ratio of 43.5:50:1.8:3.5:1.2, uniformly mixed to prepare a negative electrode slurry; then the negative electrode slurry is uniformly coated on the negative electrode current collector one or more times, and the negative electrode film is obtained after drying, and then cold-pressing and slitting to obtain the negative electrode sheet.

[0170] In an argon atmosphere glove box (H2O <0.1 ppm, O2 <0.1 ppm), the organic solvents ethylene carbonate, diethyl carbonate and dimethyl carbonate are mixed uniformly according to a mass ratio of 1:1:1, and then LiPF6 lithium salt and the mixed solvent are mixed to configure an electrolyte with a lithium salt concentration of 1 mol / L.

[0171] A polyethylene film with a thickness of 13 μm is used as the separator film.

[0172] The above positive electrode sheet, separator film and negative electrode sheet are stacked in order, with the separator film between the positive electrode sheet and the negative electrode sheet to play a separating role, and 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, and then subjected to processes such as vacuum packaging, standing, formation, shaping, etc. to obtain a lithium ion battery.

[0173] Example 2-5

[0174] The preparation method of Example 2-5 is basically the same as that of Example 1, except that the C2H 10 The BN content is changed, and thus the mass content of boron element is changed, as follows:

[0175] Example 2: C2H 10 The BN content is 1.5 g / L.

[0176] Example 3: C2H 10 The BN content is 7.5 g / L.

[0177] Example 4: C2H 10 The BN content is 10.5 g / L.

[0178] Example 5: C2H 10 The BN content is 14.5 g / L.

[0179] Example 6

[0180] 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:

[0181] The content of NiSO4·6H2O in the electroplating solution is 100 g / L; the content of FeSO4·7H2O is 105 g / L; the content of NaH2PO2·H2O is 0.15 g / L; the content of ammonium citrate is 100 g / L; and the content of the surfactant, sodium dodecyl sulfate, is 2.0 g / L.

[0182] Examples 7-10

[0183] The preparation method of Examples 7-10 is basically the same as that of Example 6, except that the content of NaH2PO2·H2O in the electroplating solution is adjusted, and the details are as follows:

[0184] Example 7: The content of NaH2PO2·H2O in the electroplating solution is 0.8 g / L.

[0185] Example 8: The content of NaH2PO2·H2O in the electroplating solution is 4.0 g / L.

[0186] Example 9: The content of NaH2PO2·H2O in the electroplating solution is 7.5 g / L.

[0187] Example 10: The content of NaH2PO2·H2O in the electroplating solution is 12.5 g / L.

[0188] Example 11

[0189] The preparation method of Example 11 is basically the same as that of Example 1, except that the mass content of nickel element, boron element and iron element is changed by adjusting the content of each component in the electroplating solution, and the details are as follows:

[0190] Example 11: The content of NiSO4·6H2O in the electroplating solution is 100 g / L, the content of FeSO4·7H2O is 97 g / L, the content of C2H 10 The content of BN is 7 g / L, and the remaining parameters are the same as those of Example 1.

[0191] Example 12

[0192] The preparation method of Example 12 is basically the same as that of Example 11, except that the preparation method of the negative current collector is changed, and the details are as follows:

[0193] The current collector obtained in Example 11 is high-temperature treated at 500℃ for 2h to obtain the current collector of Example 12.

[0194] Comparative Example 1

[0195] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the negative current collector is a nickel-iron alloy, and the details are shown in Table 1.

[0196] Comparative Example 2

[0197] The preparation method of Comparative Example 2 is basically the same as that of Example 6, except that the mass content of phosphorus element is changed by adjusting the content of FeSO4·7H2O and NaH2PO2·H2O in the electroplating solution, as follows:

[0198] Comparative Example 2: the content of FeSO4·7H2O in the electroplating solution is 85 g / L, and the content of NaH2PO2·H2O is 15 g / L.

[0199] Performance test

[0200] (1) Cycle number test of the battery

[0201] At 25℃, the secondary battery prepared in each example and comparative example is charged at a constant current of 0.5C rate to a charging cut-off voltage of 4.25V, then charged at a constant voltage until the current is 0.05C, and then rested for 5 min, then discharged at a constant current of 0.5C rate to a discharge cut-off voltage of 2.5V, and then rested for 5 min, which is one charge-discharge cycle. The capacity of the first discharge process is recorded as C1. The battery is tested by the above method for cycle charge-discharge test until the capacity of the nth discharge process is 0.8C1, the cycle cut-off is recorded, and the cycle number at 25℃ is recorded as the cycle life of the battery.

[0202] (2) Corrosion current density

[0203] The test is characterized by Tafel polarization curve analysis method. The polarization curve test adopts a standard three-electrode system, the sample to be tested (working area 1 cm 2 ) as the working electrode, platinum sheet as the auxiliary electrode, saturated calomel electrode as the reference electrode, and 3.5% NaCl solution as the electrolyte. The sample to be tested is immersed in the electrolyte for 2h, and then the polarization curve of the sample is tested at a scanning speed of 1.5mV / s after the open circuit potential is stable. The corrosion current density of the sample is calculated by fitting the Tafel curve on the electrochemical workstation.

[0204] (3) Room temperature resistivity of the current collector

[0205] The room temperature resistivity of the current collector is mainly tested by four-probe method. The current collector to be tested is cut into a size of 10mm×60mm and placed on the four-probe resistivity tester for testing to obtain the room temperature resistivity of the current collector.

[0206] Test results

[0207] Table 1

[0208] The current collector in embodiments 1-12 of the present application 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%.

[0209] As can be seen from the comparison of embodiments 1-12 and comparative example 1, compared with the conventional nickel-iron-based alloy current collector, the current collector in the embodiments of the present application has better cycle life.

[0210] As can be seen from the comparison of embodiments 1-12 and comparative example 2, controlling the mass content of the first doping element in the current collector to be 0.1%-8% can take into account the tensile strength of the current collector and the resistivity of the current collector, and comprehensively improve the service life of the battery.

[0211] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and playing the same role and effect within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments that can be thought of by those skilled in the art, and other ways constructed by combining part of the constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A current collector, wherein, 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 a mass content of the first doping element is less than 10% based on a total mass of the nickel-iron-based alloy.

2. The current collector of claim 1, wherein, The first doping element comprises at least one of a phosphorus element and a boron element.

3. The current collector of claim 1 or 2, wherein The mass content of the first doping element is 0.1%-8% based on the mass of the nickel-iron-based alloy.

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

5. The current collector of any one of claims 1-3, wherein, The first doping element comprises a phosphorus element, and a mass content of the phosphorus element in the nickel-iron-based alloy is 0.5%-5% based on the mass of the nickel-iron-based alloy.

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

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

8. The current collector of any one of claims 1 to 7, wherein, A mass content of an iron element in the nickel-iron-based alloy is 40%-49.9% based on the mass of the nickel-iron-based alloy, and a mass content of a nickel element in the nickel-iron-based alloy is 50%-59.9% based on the mass of the nickel-iron-based alloy.

9. The current collector of any one of claims 1-8, wherein, The nickel-iron-based alloy comprises an iron element with a mass content of 40%-49.9%, a nickel element with a mass content of 50%-59.9%, a first doping element with a mass content of 0.1%-8%, and impurities with a mass content of less than 6%.

10. The current collector of any one of claims 1-9, wherein, An average grain size of the grains in the current collector is 2 nm-17 nm.

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

12. The current collector of any one of claims 1-11, wherein, The thickness of the current collector is 2 μm-13 μm.

13. The current collector of any one of claims 1-12, wherein, The tensile strength of the current collector is 1050 MPa-1500 MPa.

14. A pole piece, wherein, The pole piece comprises the current collector according to any one of claims 1-13.

15. The pole piece of claim 14, wherein, The pole piece is a negative pole piece, the negative pole piece comprises a negative film layer arranged on at least one side of the current collector, the negative film layer comprises a negative active material, and the negative active material comprises a silicon-based material.

16. The pole piece of claim 15, wherein, A mass content of the silicon-based material accounts for more than or equal to 30% based on a total mass of the negative film layer.

17. The pole piece of any one of claims 15-16, wherein, A mass content of a silicon element accounts for more than or equal to 15% based on the total mass of the negative film layer.

18. A secondary battery, wherein, The pole piece according to any one of claims 14-17 is provided.

19. An electrical device, comprising: The secondary battery according to claim 18 is provided.

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