Current collector, method of manufacturing, battery cell, battery device, and power using device

Abstract

The application provides a current collector, a preparation method thereof, a battery monomer, a battery device and a power utilization device. The current collector comprises at least one first metal foil layer; the first metal foil layer comprises a first element, the first element comprises one or more of Ni, Fe, Cu and Cr; and the average grain size of the first metal foil layer is 5 nm-50 nm.

Description

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. 2025101735709, filed on February 17, 2025, entitled "Battery cell, battery device, power supply device and current collector", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery cell technology, specifically to a current collector and its preparation method, a battery cell, a battery device, and an electrical device. Background Technology

[0004] In recent years, 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.

[0005] Current collectors are an important component of batteries. As the market demands higher energy density and cycle life for batteries, there is an urgent need to develop a new generation of current collectors to meet these needs. Summary of the Invention

[0006] This application is made in view of the above-mentioned issues, and its purpose is to provide a battery cell that has both high energy density and good cycle life.

[0007] A first aspect of this application provides a current collector comprising at least one first metal foil layer; the first metal foil layer comprises a first element, the first element comprising one or more of Ni, Fe, Cu, and Cr; the average grain size of the first metal foil layer is 5 nm to 50 nm.

[0008] By incorporating a first metal foil layer with an average grain size of 5nm-50nm and main elements including Ni, Fe, Cu, and Cr into the current collector, further fine-grain reinforcement of the high-strength metal is achieved, thereby improving the tensile strength of the current collector and thus improving the cell's resistance to expansion. At the same time, it reduces the risk of brittle fracture of the current collector due to excessively small grain size, takes into account the bending resistance of the current collector, reduces the risk of cracks appearing in the inner ring of the wound cell, delays the time of battery crack failure, and improves the cycle life of the battery cell.

[0009] In some embodiments, the average grain size of the first metal foil layer is 10nm-45nm, and optionally 15nm-40nm.

[0010] In some embodiments, the thickness of the current collector is 2μm-10μm; optionally, it is 3μm-9μm; optionally, it is 4μm-8μm.

[0011] In some embodiments, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane in the X-ray diffraction spectrum of the first metal foil layer is less than 0.5, and can be selected as 0-0.3.

[0012] In some implementations, the current collector satisfies one or more of the following conditions:

[0013] (1) The first metal foil layer comprises a nickel-based alloy;

[0014] (2) The first metal foil layer comprises a nickel-based alloy; the mass content of nickel in the first metal foil layer is greater than the mass content of the other metal elements, and the mass content of nickel in the first metal foil layer is less than or equal to 95%;

[0015] (3) The first metal foil layer comprises an iron-based alloy; the mass content of iron in the first metal foil layer is greater than the mass content of the other metal elements, and the mass content of iron in the first metal foil layer is greater than or equal to 30%;

[0016] (4) The first metal foil layer comprises a nickel-iron-based alloy; the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass content of nickel in the first metal foil layer is greater than or equal to 35%, and the mass content of iron in the first metal foil layer is less than 65%.

[0017] In some implementations, the current collector satisfies one or more of the following conditions:

[0018] (1) The first metal foil layer comprises a nickel-based alloy, wherein the mass percentage of nickel in the first metal foil layer is 40%-95%;

[0019] (2) The first metal foil layer includes a nickel-iron-based alloy, wherein the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass percentage of nickel in the first metal foil layer is greater than or equal to 35%, and the mass percentage of iron in the first metal foil layer is 10%-60%.

[0020] In some embodiments, the first metal foil layer includes nickel and iron, wherein the mass percentage of nickel in the first metal foil layer is greater than the mass percentage of iron in the first metal foil layer.

[0021] Optionally, the mass percentage of nickel in the first metal foil layer is 40%-85%;

[0022] Optionally, the mass percentage of nickel in the first metal foil layer is 55%-85%;

[0023] Optionally, the mass percentage of iron in the first metal foil layer is 10%-60%, and optionally 15%-40%.

[0024] In some embodiments, the texture coefficient of the (111) crystal plane is greater than that of the (200) crystal plane in the X-ray diffraction spectrum of the first metal foil layer.

[0025] Optionally, in the X-ray diffraction spectrum of the first metal foil layer, the texture coefficient of the (111) crystal plane accounts for 30%-80%; optionally, in the X-ray diffraction spectrum of the first metal foil layer, the texture coefficient of the (200) crystal plane accounts for 15%-50%, and can be 25%-40%.

[0026] In some embodiments, the total thickness of the first metal foil layer is 30%-100% based on the total thickness of the current collector, and can be selected as 30%-85%.

[0027] In some embodiments, the current collector further includes at least one second metal layer, and the current collector satisfies one or more of the following conditions:

[0028] (1) The second metal layer includes a second element, which includes one or more of Cu, Ag, Au, Ni, Zn, and Cr, and the mass content of the second element in the second metal layer is greater than or equal to 90%;

[0029] (2) The average grain size of the second metal layer is greater than the average grain size of the first metal foil layer;

[0030] (3) The average grain size of the second metal layer is greater than or equal to 40 nm;

[0031] (4) The second metal layer includes copper, the mass content of Cu in the second metal layer is greater than or equal to 90%, and the average grain size of the second metal layer is 90nm-400nm, optionally 100-250nm;

[0032] (5) Based on the total thickness of the current collector, the total thickness of the second metal layer accounts for 15%-70%;

[0033] (6) At least a portion of the second metal layer is close to the surface of the current collector.

[0034] In some embodiments, the current collector further includes at least one second metal layer, and the current collector satisfies one or more of the following conditions:

[0035] (1) The second metal layer includes a second element, which includes one or more of Cu, Ag, Au, Ni, Zn, and Cr. The mass content of the second element in the second metal layer is greater than or equal to 99%, and the average grain size of the second metal layer is 90nm-400nm, optionally 100-250nm.

[0036] (2) The second metal layer includes copper, the mass content of Cu in the second metal layer is greater than or equal to 99%, and the average grain size of the second metal layer is 90nm-400nm, optionally 100-250nm.

[0037] In some embodiments, the current collector includes two second metal layers close to the surface of the current collector in the thickness direction and a first metal foil layer disposed between the two second metal layers in the thickness direction.

[0038] In some embodiments, the current collector includes the first metal foil layer, and the current collector satisfies one or more of the following conditions:

[0039] (1) The current collector comprises a nickel-based alloy, wherein the mass content of nickel in the current collector is 40%-95%;

[0040] (2) The current collector includes a nickel-iron based alloy, wherein the mass content of nickel and iron in the current collector is greater than that of the other metal elements, the mass content of nickel in the current collector is greater than or equal to 35%, and the mass content of iron in the current collector is 10%-60%;

[0041] (3) The range of iron content in the current collector is less than or equal to 6%;

[0042] (4) The current collector includes Ni, FeNi3, Fe3Ni2, and Ni 0.64 Fe 0.36 One or more of the Ni1Fe1 phase;

[0043] (5) The thickness range of the current collector is less than or equal to 0.5 μm.

[0044] In some embodiments, the current collector comprises at least one first metal foil layer and at least two second metal layers, and the current collector satisfies one or more of the following conditions:

[0045] (1) The first metal foil layer includes a nickel-based alloy, and the mass percentage of nickel in the first metal foil layer is 40%-95%; the second metal layer includes copper, and the mass percentage of Cu in the second metal layer is greater than or equal to 90%; the average grain size of the second metal layer is 90nm-400nm, and optionally 100-250nm;

[0046] (2) The first metal foil layer includes a nickel-iron-based alloy, wherein the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass percentage of nickel in the first metal foil layer is greater than or equal to 35%, and the mass percentage of iron in the first metal foil layer is 10%-60%; the second metal layer includes copper, wherein the mass percentage of Cu in the second metal layer is greater than or equal to 90%; the average grain size of the second metal layer is 90nm-400nm, optionally 100-250nm;

[0047] (3) Based on the total mass of the current collector, the mass percentage of nickel is 25%-70%, the mass percentage of iron is 1%-40%, and the mass percentage of copper is 15%-65%;

[0048] (4) The range of iron content in the current collector is less than or equal to 6%;

[0049] (5) The first metal foil layer includes Ni, FeNi3, Fe3Ni2, and Ni 0.64 Fe 0.36 One or more of the Ni1Fe1 phase;

[0050] (6) The total thickness of the current collector is 2μm-10μm;

[0051] (7) The thickness range of the current collector is less than or equal to 0.5 μm.

[0052] In some embodiments, under test conditions of room temperature and a tensile speed of 50±0.5 mm / min, the tensile strength of the current collector is 0.9 GPa-2 GPa, optionally 1.2 GPa-2 GPa, or optionally 1.4 GPa-2 GPa.

[0053] In some embodiments, fatigue testing is performed at room temperature and under 1% extended load, and the current collector undergoes fatigue cycles of 500 or more.

[0054] In some embodiments, fatigue testing is performed at room temperature and under 1% extended load, with the current collector undergoing 2000-4000 fatigue cycles.

[0055] In some embodiments, the elongation at break of the current collector is 1%-8% under test conditions of room temperature and tensile speed of 50±0.5 mm / min.

[0056] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the current collector is 2%-8%, optionally 3%-6%.

[0057] In some embodiments, the current collector has a bending resistance of 1 to 10 times under room temperature test conditions.

[0058] A second aspect of this application provides a method for preparing a current collector, comprising the following steps:

[0059] S10. Provide an anode, a first electroplating solution, and a cathode, and perform electroplating to form a first metal foil layer on the surface of the cathode; wherein, the first electroplating solution includes a first metal source, a primary brightener, a secondary brightener, a stress reliever, and a complexing agent; the primary brightener includes one or more of saccharin or sodium saccharin; the secondary brightener includes one or more of alkynyl alcohol compounds or alkynylamine compounds and their salts; the stress reliever contains unsaturated bonds and acid radicals, and the acid radicals include one or more of sulfate or sulfonate; the first metal source includes one or more of Ni, Fe, Cu, and Cr sources.

[0060] S20. Separate the first metal foil layer from the surface of the cathode to form a first metal foil layer.

[0061] In some implementations, S20 is followed by:

[0062] S30. Electroplating the first metal foil layer with a second electroplating solution to form a second metal layer on at least one side of the first metal foil layer;

[0063] Optionally, the second electroplating solution includes a second metal source, which includes at least one of Cu, Ag, Au, Ni, Zn, or Cr.

[0064] In some embodiments, the first electroplating solution satisfies one or more of the following characteristics:

[0065] (1) The concentration of the main brightener in the first electroplating solution is 1.5 g / L-5 g / L;

[0066] (2) The concentration of the secondary brightener in the first electroplating solution is 0.2 g / L-1 g / L;

[0067] (3) The total number of carbon and oxygen atoms on the main chain of the alkynol compound is ≥4; optionally, the alkynol compound includes one or more of butynediol, butynediol diethoxy ether or propynediol ethoxy compound;

[0068] (4) The concentration of stress reliever in the first electroplating solution is 0.1g / L-0.5g / L.

[0069] In some embodiments, the current density of the electroplating process for forming the first metal foil layer is 3 A / dm. 2 -10A / dm 2 .

[0070] A third aspect of this application provides a battery cell including an electrode assembly, the electrode assembly including a negative electrode sheet, the negative electrode sheet including a negative current collector, the negative current collector being the current collector of the first aspect.

[0071] In some embodiments, the negative electrode includes a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including a silicon-based material.

[0072] In some embodiments, the battery cell includes one or more wound cells.

[0073] In some embodiments, the battery cell satisfies one or more of the following conditions:

[0074] (1) The thickness of the wound battery cell is 10mm-50mm;

[0075] (2) The ratio of the length of the straight section to the length of the corner section of the wound cell is 1-10;

[0076] (3) The single-sided density of the negative electrode sheet is 20 mg / 1540.25 mm. 2 -200mg / 1540.25mm 2 The option is 50mg / 1540.25mm. 2 -200mg / 1540.25mm 2 ;

[0077] (4) The compaction density of the negative electrode sheet is 0.9 g / cm³. 3 -1.8g / cm 3 1.3g / cm³ is an optional value. 3 -1.8g / cm 3 ;

[0078] (5) The thickness of the single-sided film layer of the negative electrode sheet is 20μm-150μm, and can be selected as 40μm-80μm;

[0079] (6) The full discharge margin of the battery cell is 70%-105%.

[0080] In some embodiments, the battery cell includes a negative electrode sheet, the film layer of the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a silicon-based material, and based on the total mass of the negative electrode film layer, the mass content of silicon element is greater than or equal to 10%, and the thickness of the wound cell is 10mm-50mm.

[0081] In some embodiments, the battery cell includes a negative electrode sheet; the film layer of the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a silicon-based material, and based on the total mass of the negative electrode film layer, the mass content of silicon element is greater than or equal to 10%, and the thickness of the wound cell is 10mm-25mm.

[0082] A fourth aspect of this application provides a battery cell including an electrode assembly, the electrode assembly including a positive electrode, a solid electrolyte and a negative electrode, the solid electrolyte being located between the positive electrode and the negative electrode, the negative electrode including a negative current collector, the negative current collector being the current collector of the first aspect.

[0083] In some embodiments, the solid electrolyte comprises a sulfide.

[0084] The fifth aspect of this application provides a battery device, the battery device comprising a battery cell of the fourth aspect, and the battery device comprising at least one of a battery module, a battery pack, and an energy storage device.

[0085] The sixth aspect of this application provides an electrical device, including a battery cell of the fourth aspect or a battery device of the fifth aspect. Attached Figure Description

[0086] 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.

[0087] Figure 1 Here are cross-sectional views (a) and (b) the morphology of the current collector according to one embodiment of this application;

[0088] Figure 2 This is an X-ray diffraction pattern of the first metal foil layer according to an embodiment of this application;

[0089] Figure 3 This is a schematic diagram of a wound battery cell according to one embodiment of this application;

[0090] Figure 4 These are the fatigue test curves of the current collectors in embodiments (a) and (b) of this application;

[0091] Figure 5 This is a schematic diagram of one embodiment of the battery cell of this application;

[0092] Figure 6 This is an exploded view of one embodiment of the battery cell of this application;

[0093] Figure 7 This is a schematic diagram of one embodiment of the battery module of this application;

[0094] Figure 8 This is a schematic diagram of one embodiment of the battery pack of this application;

[0095] Figure 9 yes Figure 8 An exploded view of an embodiment of the battery pack shown;

[0096] Figure 10 This is a schematic diagram of one embodiment of an electrical device that uses the battery cell of this application as a power source.

[0097] 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 Battery cell, 51 Housing, 52 Electrode assembly, 53 Cover plate, 6 Winded cell, 61 Electrode sheet, 10 Current collector, 101 First metal foil layer, 102 Second metal layer, 103 Passivation layer. Detailed Implementation

[0098] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, current collector, battery device, and power-consuming 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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 method may also include step (c), indicating 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.

[0103] 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.

[0104] 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).

[0105] Unless otherwise specified, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0106] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, according to the testing methods given in this application.

[0107] 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 battery cell, including but not limited to lithium ions.

[0108] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0109] As batteries age, some experience electrode breakage during long-cycle operation, leading to battery failure—a phenomenon known in the industry as "crack failure." Battery crack failure typically occurs at the corners of the outer electrode rings in the wound cell, especially in cells with high expansion forces, such as those using silicon-based anodes, thickly coated cells, or cells where the group margin has reached its design limit. Currently, common methods to address crack failure include creating gaps at the corners of the wound cell using techniques like pores in the separator to allow space for cell expansion; or delaying the onset or probability of crack failure by reducing the number of winding turns or increasing the number of cells. However, creating gaps at the corners of the wound cell can lead to lithium plating, and reducing the number of winding turns or increasing the number of cells reduces processing efficiency and production capacity.

[0110] Based on this, this application provides a current collector, which includes at least one first metal foil layer; the first metal foil layer includes a first element, which includes one or more of Ni, Fe, Cu, and Cr; the average grain size of the first metal foil layer is 5nm-50nm.

[0111] This application embodiment achieves further grain refinement of high-strength metal by including a first metal foil layer with an average grain size of 5nm-50nm and main elements including Ni, Fe, Cu, and Cr in the current collector. This improves the tensile strength of the current collector, thereby improving the cell's resistance to expansion. At the same time, it reduces the risk of brittle fracture of the current collector due to excessively low grain size, takes into account the bending resistance of the current collector, reduces the risk of cracks appearing in the inner ring of the wound cell, delays the time of battery crack failure, and improves the cycle life of the battery cell.

[0112] In addition, this application also provides a battery cell. The battery cell includes an electrode assembly, the electrode assembly includes a negative electrode sheet, the negative electrode sheet includes a negative current collector, and the negative current collector is the aforementioned current collector.

[0113] It is understood that the negative electrode current collector in a single battery cell is the aforementioned current collector. The single battery cell will be described below. It is also understood that the characteristics of the aforementioned current collector can be selected from those of the negative electrode current collector in the single battery cell described below. For the sake of brevity, the characteristics of the current collector will not be repeated here.

[0114] In some embodiments, the thickness of the current collector is 2μm-10μm. Optionally, the thickness of the current collector can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, or any value within the range of any two of the above values. Optionally, the thickness of the negative electrode current collector is 3μm-9μm, 4μm-8μm, etc.

[0115] In some embodiments, the negative electrode includes a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including a silicon-based material. The use of silicon-based materials is beneficial for improving the energy density of the battery cell.

[0116] In some embodiments, the battery cell includes one or more wound cells.

[0117] It is understood that the wound cell includes a corner region and a flat region; the wound cell includes an electrode, the electrode includes a current collector and a film layer disposed on at least one side of the current collector, the current collector includes at least one first metal foil layer; the first metal foil layer includes a first element, the first element including one or more of Ni, Fe, Cu, and Cr; the average grain size of the first metal foil layer is 5nm-50nm.

[0118] This application embodiment achieves further grain refinement of high-strength metal by including a first metal foil layer with an average grain size of 5nm-50nm and main elements including Ni, Fe, Cu, and Cr in the current collector. This improves the tensile strength of the current collector, thereby improving the cell's resistance to expansion. At the same time, it reduces the risk of brittle fracture of the current collector due to excessively low grain size, takes into account the bending resistance of the current collector, reduces the risk of cracks appearing in the inner ring of the wound cell, delays the time of battery crack failure, and improves the cycle life of the battery cell.

[0119] In some embodiments, the wound cell is formed by winding a positive electrode, a negative electrode, and a separator. The wound cell includes a corner area and a straight area. The straight area refers to the straight section formed after the positive and negative electrode and the separator are wound into a roll, which is the main working area of ​​the cell. The corner area refers to the arc-shaped section formed after the positive and negative electrode and the separator are wound into a roll.

[0120] In some implementations, the battery cell includes a wound cell.

[0121] In some embodiments, a single battery cell includes multiple wound cells connected in parallel, series, or a combination of both. In some embodiments, the current collector is a single layer consisting only of a first metal foil layer. In other words, based on the total thickness of the current collector, the total thickness of the first metal foil layer accounts for 100%, meaning that there is no obvious delamination along the thickness direction of the current collector.

[0122] In some implementations, such as Figure 1 As shown, the current collector has a multilayer structure. That is, the current collector is composed of two, three, four or more metal layers. In multilayer current collectors, one or more of the following characteristics—composition, composition ratio, crystal structure, and grain morphology—exhibit significant differences in different regions along the thickness direction, causing the current collector to exhibit layered characteristics under at least some specific characterization. It is understood that the multilayer structure of the current collector is not limited to the morphological layering shown under a microscope or scanning electron microscope, but may also be revealed through compositional characterization (such as obtaining the current collector cross-section through argon ion polishing, or characterization through energy dispersive spectroscopy combined with scanning electron microscopy), phase characterization (metallography), or grain characterization (backscattered electron diffraction).

[0123] In some embodiments, the first metal foil layer includes a first element, which includes one or more of Ni, Fe, Cu, and Cr.

[0124] The aforementioned metallic elements possess both high strength and plasticity, which helps improve the current collector's resistance to expansion during long-term cycling and increase the cycle life of the battery cell.

[0125] In some embodiments, the first metal foil layer mainly comprises any one of the first elements, that is, the first metal foil layer is a pure metal layer.

[0126] In some embodiments, the first metal foil layer primarily comprises at least two of the first elements, i.e., the first metal foil layer is an alloy layer. It is understood that the alloy layer may include any one of a solid solution, eutectoid, eutectic, or compound (intermetallic compound), or these may coexist.

[0127] The elemental composition of the first metal foil layer can be obtained by energy dispersive spectroscopy (EDS) or plasma atomic emission spectrometry (PISA). The mass percentage of the first element in the first metal foil layer can be obtained by separating the first metal foil layer from the current collector and analyzing it using PISA.

[0128] Metals or alloys containing the aforementioned metallic elements readily form face-centered cubic cell structures, which helps to balance the strength and plasticity of the current collector and improve the cycle life of the battery cell.

[0129] In some embodiments, the average grain size of the metal layer can be tested using any method known in the art. For example, X-ray diffraction (XRD) tests can be performed on different metal layers in a current collector to analyze the average grain size of the metal layers. As an example, at room temperature, using CuKα rays as the X-ray source, a scanning speed of 2º / min, and a scanning range of 10º-100º, an X-ray diffraction pattern is measured using an X-ray diffractometer. The peak with the highest diffraction intensity in the X-ray diffraction pattern is used as a reference, and the average grain size is calculated using the Scherrer formula D=Kλ / (βcosθ), where D is the average grain size, K is the Scherrer constant (0.89), λ is the X-ray wavelength (selectably 0.154 nm), β is the full width at half maximum (FWHM) of the diffraction peak, and θ is the diffraction angle. Figure 2 Taking the metal layer shown as an example, Figure 2 The peak with the highest diffraction intensity is located between 43.5º and 44.8º at a diffraction angle 2θ. Therefore, this peak is used to calculate the average grain size of the metal layer. It is understandable that X-ray diffraction (XRD) tests on different metal layers in the current collector can be achieved by selectively testing different metal layers in the current collector, or by etching other metal layers in the current collector to obtain the corresponding metal layer for XRD testing.

[0130] In some embodiments, the average grain size of the first metal foil layer can be selected as 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 20nm, 30nm, 40nm, 50nm or any value range between the two.

[0131] In some embodiments, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane in the X-ray diffraction spectrum of the first metal foil layer is less than 0.5, and can be selected as 0-0.3.

[0132] The diffraction peak intensities of the (110) and (111) crystal planes can be obtained by X-ray diffraction testing of the first metal foil layer. The X-ray diffraction spectrum of the first metal foil layer is compared with the standard XRD spectrum of the standard sample specified by the Joint Committee on Powder Diffraction Standards (JCPDS) to analyze the phase and crystal planes corresponding to the diffraction peaks of the first metal foil layer. The diffraction peak intensity of the (110) crystal plane in the X-ray diffraction pattern of the first metal foil layer is calculated and divided by the diffraction peak intensity of the (111) crystal plane.

[0133] In some embodiments, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane in the X-ray diffraction spectrum of the first metal foil layer can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.49 or any value range between the two.

[0134] Please continue to refer to this. Figure 2 In some embodiments of this application, the X-ray diffraction spectrum of the first metal foil layer of the current collector mainly includes diffraction peaks located at 44.0º±0.8º, 51.2º±0.8º, 76.0º±0.5º, and 92.0º±1.0º, respectively. Phase analysis shows that these diffraction peaks correspond to the (111) crystal plane, (200) crystal plane, (220) crystal plane, and (311) crystal plane, respectively, but do not show the diffraction peak of the (110) crystal plane.

[0135] The (111) crystal plane is a close-packed plane of a face-centered cubic unit cell structure. Therefore, in the X-ray diffraction pattern, a high intensity of the diffraction peak of the (111) crystal plane indicates that the current collector has a high content of face-centered cubic unit cell structure. The (110) crystal plane is a close-packed plane of a body-centered cubic unit cell structure. In the X-ray diffraction pattern, a high intensity of the diffraction peak of the (110) crystal plane indicates that the current collector has a high content of body-centered cubic unit cell structure.

[0136] In a face-centered cubic (FCC) cell structure, atoms are more densely packed, resulting in a higher packing density (approximately 74%), higher than the 68% packing density of a body-centered cubic (BCC) cell. Furthermore, the (111) plane in the FCC structure is both its close-packed plane and its slip plane. This means that during plastic deformation of the foil layer, dislocations in the FCC structure are more likely to move on the (111) plane; because these planes have the highest atomic packing density, larger interplanar spacing, and relatively weaker atomic bonding forces between planes, resulting in less resistance during slip. This makes FCC materials more prone to plastic deformation rather than fracture when subjected to external forces.

[0137] Based on the X-ray diffraction spectrum of the first metal foil layer, the ratio of the diffraction peak intensity of the (110) crystal plane to that of the (111) crystal plane is less than 0.5, which means that the current collector is mainly composed of face-centered cubic cell structure, which is beneficial to improving the plasticity of the current collector.

[0138] The preferred orientation of the (111) crystal plane in the first metal foil layer makes it easier for the current collector to undergo plastic deformation rather than brittle fracture when subjected to force. This is beneficial for the current collector to further balance tensile strength and plasticity, delays the time when the wound cell will produce crack failure, and helps to improve the cycle life of the battery cell.

[0139] In some embodiments, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane in the X-ray diffraction spectrum of the first metal foil layer is 0-0.3.

[0140] In the X-ray diffraction spectrum of the first metal foil layer, the ratio of the diffraction peak intensity of the (110) crystal plane to that of the (111) crystal plane is within the above range, which means that the first metal foil layer has the (111) crystal plane as the preferred orientation plane, which is beneficial to improve the slip characteristics of the grains, improve the plasticity of the current collector, improve the ability of the current collector to withstand repeated expansion and contraction during the cycle, and delay the timing of the cell crack failure.

[0141] In some embodiments, the first metal foil layer comprises a nickel-based alloy.

[0142] In this application, nickel-based alloys refer to alloys whose main constituent element is nickel, and the Ni content in nickel-based alloys generally exceeds 30 wt%. Nickel-based alloys combine high tensile strength, good structural stability, and material plasticity, which is beneficial for balancing the strength and plasticity of current collectors and improving the cycle life of battery cells.

[0143] In some embodiments, the first metal foil layer comprises a nickel-based alloy, wherein the mass content of nickel in the first metal foil layer is greater than the mass content of the other metal elements, and the mass content of nickel in the first metal foil layer is less than or equal to 95%.

[0144] In some embodiments, the mass content of nickel in the first metal foil layer can be selected as 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or any value range between the two.

[0145] In this embodiment, the first metal foil layer is alloyed with nickel and other metal elements to further improve the elongation at break and plasticity of the current collector, so that the wound cell can maintain a high elongation at break during the expansion and contraction process, thus delaying the occurrence of the wound cell crack.

[0146] In some embodiments, the first metal foil layer comprises an iron-based alloy; the mass content of iron in the first metal foil layer is greater than the mass content of the other metal elements, and the mass content of iron in the first metal foil layer is greater than or equal to 30%.

[0147] In some embodiments, the mass content of iron in the first metal foil layer can be selected as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or any value range between the two.

[0148] In this application, iron-based alloys refer to alloys whose main constituent element is iron. Iron-based alloys combine high plasticity and low cost, which is beneficial for the electrode to maintain a high residual elongation at break after stretching and delaying the appearance of cracks on the outer ring of the wound cell.

[0149] In some embodiments, the first metal foil layer includes a nickel-iron-based alloy, wherein the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass content of nickel in the first metal foil layer is greater than or equal to 35%, and the mass content of iron in the first metal foil layer is less than 65%.

[0150] In this application, nickel-iron-based alloys refer to alloys whose main constituent elements include nickel and iron.

[0151] In some embodiments, the nickel-iron-based alloy also contains impurity elements or dopants such as Cr, Si, S, P, and C.

[0152] In some embodiments, the first metal foil layer includes a nickel-iron-based alloy, and the mass content of nickel in the first metal foil layer can be selected as 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95% or any range between the two; the mass content of iron in the first metal foil layer can be selected as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 62% or any range between the two.

[0153] Nickel-iron based alloys exhibit high stability in electrochemical environments, are not prone to corrosion, and possess both high tensile strength and plasticity. This allows the electrode to maintain high resistance to external shell pressure during cycling and retain high residual elongation at break after stretching.

[0154] In some embodiments, the first metal foil layer includes a nickel-based alloy, wherein the mass percentage of nickel in the first metal foil layer is 40%-95%.

[0155] Nickel-based alloys with a nickel content within the above range have both high tensile strength and good plasticity, which helps to balance the strength and elongation at break of the current collector, delay the time when the wound cell will crack during long cycles, and improve the cycle life of the battery cell.

[0156] In some embodiments, the first metal foil layer includes a nickel-iron-based alloy, wherein the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass percentage of nickel in the first metal foil layer is greater than or equal to 35%, and the mass percentage of iron in the first metal foil layer is 10%-60%.

[0157] Nickel-iron based alloys with nickel-iron element mass ratios within the above ranges combine high tensile strength, good plasticity, and low cost. This helps to balance the strength and elongation at break of the current collector, delays the time when the wound cell will crack during long cycles, and improves the cycle life of the battery cell.

[0158] In some embodiments, the first metal foil layer includes nickel and iron, wherein the mass percentage of nickel in the first metal foil layer is greater than the mass percentage of iron in the first metal foil layer.

[0159] In some embodiments, the nickel element comprises 40%-85% by mass in the first metal foil layer.

[0160] In some embodiments, the nickel element comprises 55%-85% by mass in the first metal foil layer.

[0161] In some embodiments, the iron element has a mass percentage of 10%-60% in the first metal foil layer, and may be 15%-40%.

[0162] In some embodiments, the electrode is a negative electrode; the film layer of the negative electrode includes a negative electrode active material, which includes at least one of a carbon-based material or a silicon-based material.

[0163] In some embodiments, the carbon-based material includes one or more of graphite, hard carbon, soft carbon, and graphene.

[0164] In some embodiments, the silicon-based material includes one or more of nano-silicon, silicon-carbon materials, silicon-oxygen materials, silicon-nitrogen materials, and silicon alloys.

[0165] As lithium ions intercalate and deintercalate, the negative electrode often exhibits a high expansion rate. Therefore, crack failure frequently occurs in the negative electrode.

[0166] In some embodiments, the thickness H of the wound cell 6 is 10mm-50mm.

[0167] like Figure 3 As shown, the thickness H of the wound cell 6 can be tested using any method known in the art. For example, a wound cell sample is placed on a flat surface, and a micrometer is used to measure the thickness at the center of the sample. At least 10 wound cell samples are tested, and the average value of the test results is taken as the thickness of the wound cell. It is understood that the wound cell sample can be a freshly prepared wound cell or a wound cell obtained from disassembling a battery cell.

[0168] In some embodiments, the thickness of the wound cell can be selected as 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm, 50mm or any value range between the two.

[0169] Wound cells with thicknesses within the aforementioned range have high energy density, but they also need to withstand high expansion forces during cycling, making the current collector prone to cracking and leading to cell failure. The battery cell provided in this application embodiment can have both high energy density and reduce the probability of current collector cracking and delay crack initiation time, thus balancing the battery's energy density and cycle life.

[0170] In some embodiments, the ratio of the length of the straight section to the length of the corner section of the wound cell is 1-10.

[0171] In some embodiments, the ratio of the straight section length L1 to the corner section length L2 of the wound cell can be selected as 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or any value range between the two.

[0172] Please refer to Figure 3 The length of the straight section refers to the length of the straight section formed after the positive and negative electrode plates and the separator are wound into a coil in the wound cell, i.e., L1; the length of the winding section refers to the normal distance from the intersection of the straight section and the winding section to the tangential plane at the farthest end of the winding section, i.e., L2.

[0173] Battery cells with a straight section length to corner section length ratio within the aforementioned range have smaller corner radii. While this improves the space utilization of the battery casing, it also makes the inner ring of the cell prone to significant bending, leading to cracking of the inner ring electrode. The battery cells in this application embodiment are suitable for this cell design, achieving a balance between high energy density and cycle life.

[0174] In some embodiments, the density of the negative electrode sheet on one side is 20 mg / 1540.25 mm². 2 -200mg / 1540.25mm 2 The option is 50mg / 1540.25mm. 2 -200mg / 1540.25mm 2 .

[0175] In some embodiments, the density of the negative electrode sheet on one side is 20 mg / 1540.25 mm². 2 30mg / 1540.25mm 2 40mg / 1540.25mm 2 50mg / 1540.25mm 2 60mg / 1540.25mm 2 70mg / 1540.25mm 2 80mg / 1540.25mm 2 90mg / 1540.25mm 2 100mg / 1540.25mm 2 110mg / 1540.25mm 2 120mg / 1540.25mm 2 130mg / 1540.25mm 2 140mg / 1540.25mm 2 150mg / 1540.25mm 2 160mg / 1540.25mm 2 170mg / 1540.25mm2 180mg / 1540.25mm 2 190mg / 1540.25mm 2 200mg / 1540.25mm 2 Or the range of values ​​between any two.

[0176] In this application, the unilateral density of the electrode sheet has a well-known meaning in the art and can be tested using the following method. For example, the battery is placed in a 25°C oven and left to stand for 2 hours. Once the battery temperature is maintained at 25°C, the battery is discharged at a constant current of 1 / 3C to 2.0V. The battery is then disassembled to obtain the electrode sheet. The residual electrolyte is treated with dimethyl carbonate solvent, the electrode sheet is dried, and it is cut into small circular pieces with an area of ​​S1. The mass of these pieces is weighed and recorded as M1. Then, the film layer of the weighed electrode sheet is removed, and the weight of the current collector is weighed and recorded as M0. The unilateral density of a single-sided coated electrode sheet is (M1-M0) / S1, and the unilateral density of a double-sided coated electrode sheet is (M1-M0) / (2×S1). To ensure the accuracy of the test results, multiple groups (e.g., 10 groups) of samples can be tested, and the average value can be calculated as the test result.

[0177] The electrode in this embodiment has high tensile strength and can withstand the large expansion force of high areal density electrode (i.e., thick coated electrode), which is beneficial to further improve the energy density of the battery.

[0178] In some embodiments, the compaction density of the negative electrode sheet is 0.9 g / cm³. 3 -1.8g / cm 3 1.3g / cm³ is an optional value. 3 -1.8g / cm 3 .

[0179] The compaction density of the negative electrode sheet can be tested using the following method. As an example, place the battery in a 25°C oven environment and let it stand for 2 hours. After the battery temperature is maintained at 25°C, discharge the battery at a constant current of 1 / 3C to 2.0V. Disassemble the battery to obtain the electrode sheet. Treat the residual electrolyte with dimethyl carbonate solvent, dry the electrode sheet, cut it into small circular pieces with an area of ​​S, weigh it as W1, and measure the thickness T1 of the electrode sheet using a micrometer. Then wipe off the film layer of the weighed electrode sheet, weigh the current collector and record it as W2, and measure the thickness T2 of the current collector using a micrometer. Then the compaction density of the electrode sheet PD = (W1-W2) / [(T1-T2)×S].

[0180] In some embodiments, the compaction density of the negative electrode sheet can be selected as 0.9 g / cm³. 3 1.0g / cm 3 1.1g / cm 3 1.2g / cm3 1.3g / cm 3 1.35g / cm 3 1.4g / cm 3 1.45g / cm 3 1.5g / cm 3 1.55g / cm 3 1.6g / cm 3 1.65g / cm 3 1.7g / cm 3 1.75g / cm 3 1.8g / cm 3 Or the range of values ​​between any two.

[0181] The negative electrode sheet of this application embodiment has both high compaction density and good fracture resistance, which is beneficial to improving the energy density and cycle life of the battery cell.

[0182] In some embodiments, the thickness of the film layer on one side of the negative electrode is 20μm-150μm, and can be selected as 40μm-80μm.

[0183] In some embodiments, the thickness of the single-sided film layer of the negative electrode can be selected as 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm or any value range between the two.

[0184] The thickness of the film on one side of the electrode can be tested using the following method. As an example, the film thickness in the cross-section of the electrode is measured using a scanning electron microscope.

[0185] The electrode in this embodiment has high tensile strength and can withstand the large cyclic expansion force of the thick-coated electrode, which is beneficial to further improve the energy density of the battery.

[0186] In some embodiments, the full discharge margin of the battery cell is 70%-105%.

[0187] Group margin refers to the ratio of the actual internal cross-sectional area occupied by the battery cell to the maximum internal cross-sectional area of ​​the battery cell. In battery design, group margin is used to characterize the space filling degree within the battery cell, that is, the degree to which the cell is filled within the battery casing. In this application, full discharge refers to the state of the battery cell discharged to the cutoff voltage (usually the minimum allowable voltage of the battery). Full discharge group margin is calculated by dividing the total thickness of the wound cells in the battery cell by the inner width of the battery cell casing in the direction of the wound cell thickness. Because the cell will rebound during cycling, causing the casing to expand, the full discharge group margin of the battery cell may be greater than or equal to 100%.

[0188] In some implementations, the full discharge margin of a single battery cell can be selected as 70%, 75%, 80%, 85%, 90%, 95%, 100%, 105%, or any value range between the two.

[0189] A cell's full-discharge margin within the aforementioned range indicates high space filling within the cell, which, while beneficial for increasing energy density, also makes it prone to crack failure. The cell designs in this application are particularly suitable for high-margin cell designs, improving both energy density and battery life.

[0190] In some embodiments, the battery cell includes a negative electrode sheet, the film layer of the negative electrode sheet includes a negative electrode active material, the negative electrode active material is a silicon-based material, and based on the total mass of the negative electrode film layer, the mass percentage of silicon element is greater than or equal to 10%, and the thickness of the wound cell is 10mm-50mm.

[0191] Silicon-based materials are beneficial for improving the energy density of individual battery cells. However, silicon-based materials exhibit significant lattice expansion during battery cell cycling, leading to a high expansion rate of the electrode sheets. This high expansion rate can easily cause cracks or even breakage in the current collector. The battery cells described in this application are particularly suitable for battery systems incorporating silicon-based materials, which are beneficial for achieving both high energy density and good cycle life.

[0192] In some implementations, the mass percentage of silicon is greater than or equal to 10% based on the total mass of the negative electrode film.

[0193] Based on the total mass of the negative electrode film, the mass content of silicon can be measured using any method known in the art. As an example, inductively coupled plasma spectrometry (ICP) is used to measure the elements in the negative electrode film. In some embodiments, based on the total mass of the negative electrode film, the mass content percentage of silicon can be selected as 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, or any value between these two ranges.

[0194] The battery cells of this application embodiment are applicable to high-silicon systems, which helps to further improve the energy density per unit mass of the battery cell. In some embodiments, the battery cell includes a negative electrode sheet; the film layer of the negative electrode sheet includes a negative electrode active material, the negative electrode active material is a silicon-based material, and based on the total mass of the negative electrode film layer, the mass percentage of silicon element is greater than or equal to 10%, and the thickness of the wound cell is 10mm-25mm.

[0195] Silicon-based materials possess high specific capacity, and their inclusion enables thin-walled wound cells to achieve high energy density. However, silicon-based materials exhibit significant lattice expansion during cell cycling, leading to a high expansion rate of the electrode sheets. This high expansion rate increases the risk of cracks or even breakage in the current collector during cycling. The silicon-based wound cell with a thickness within the aforementioned range provided in this application combines high energy density with excellent cycle life.

[0196] In some embodiments, the battery cell includes a negative electrode sheet, the film layer of the negative electrode sheet includes a negative electrode active material, the negative electrode active material is a carbon-based material, and based on the total mass of the negative electrode film layer, the mass content of the carbon-based material is greater than or equal to 90%, and the thickness of the wound cell is 10mm-50mm, optionally 20mm-50mm.

[0197] In some embodiments, based on the total mass of the negative electrode film, the mass percentage of carbon-based material can be selected as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or any value range between two of these. Carbon-based materials have a smaller specific capacity than silicon-based materials, but exhibit better cycle stability, enabling their application in energy storage batteries to achieve long cycle life. The wound battery cells containing carbon-based materials with thicknesses within the above-mentioned ranges provided in this application embodiment can further extend cycle life while maintaining a certain energy density.

[0198] 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.

[0199] 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).

[0200] 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.

[0201] The negative electrode film 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 usually 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.

[0202] 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 undercoating 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.

[0203] In some embodiments, the texture coefficient of the (111) crystal plane is greater than that of the (200) crystal plane in the X-ray diffraction spectrum of the first metal foil layer.

[0204] In some embodiments, the texture coefficient of the (111) crystal plane accounts for 30%-80% in the X-ray diffraction spectrum of the first metal foil layer.

[0205] (111) The proportion of the texture coefficient of the crystal plane can be obtained by X-ray diffraction test of the first metal foil layer.

[0206] The X-ray diffraction pattern of the first metal foil layer was compared with the standard pattern. The phase and crystal plane corresponding to the diffraction peak of the first metal foil layer were analyzed. The texture coefficient M of the (111) crystal plane was calculated with reference to Equation I.

[0207] M(111)=I(111) / IR(111) (Formula I)

[0208] Where I(111) is the diffraction peak intensity of the (111) crystal plane in the X-ray diffraction spectrum obtained by actual testing, and IR(111) is the standard intensity of the (111) crystal plane in the standard XRD spectrum of the main phase.

[0209] (111) The proportion of the texture coefficient P(111) of the crystal plane is calculated by Equation II.

[0210] P(111)=M(111) / (Formula II)

[0211] Where M(hkl) is the texture coefficient of each crystal plane of the main phase in the X-ray diffraction spectrum obtained by actual testing.

[0212] The following is for reference Figure 2 The texture coefficient ratio P(111) of the (111) crystal plane is explained. In some embodiments, the X-ray diffraction pattern of the first metal foil layer of the current collector is as follows: Figure 2 As shown, the diffraction peaks mainly include those located at 44.0º±0.8º, 51.2º±0.8º, 76.0º±0.5º, and 92.0º±1.0º, respectively. Phase analysis shows that these diffraction peaks correspond to Ni. 4.00 The (111), (200), (220), and (311) crystal planes are shown in the XRD standard card (reference code: 96-901-3035). Therefore, the texture factor P(111) of the (111) crystal plane can be calculated by the following formula.

[0213] P(111)=M(111) / [M(111)+M(200)+M(220)+M(311)]=[I(111) / IR(111)] / [[I(111) / IR(111)]+ [I(200) / IR(200)]+ [I(220) / IR(220)]+ [I(311) / IR(311)]】=I(111) / [I(111)+ [I(200) / IRP(200)]+ [I(220) / IRP(220)]+ [I(311) / IRP(311)]】

[0214] IRP(hkl) represents the ratio of the intensity of the diffraction peak of the (hkl) crystal plane to the intensity of the highest diffraction peak in the standard XRD pattern, which can be found in the standard XRD pattern. It can be understood that when the texture coefficient ratio of the crystal plane is close to or greater than 25%, it means that the crystal plane has a high degree of orientation.

[0215] In some embodiments, the texture coefficient of the (111) crystal plane in the X-ray diffraction spectrum of the first metal foil layer can be selected as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any value range between the two.

[0216] The fact that the proportion of the texture coefficient of the (111) crystal plane is within the above range means that the orientation degree of the (111) crystal plane in the grains of the first metal foil layer is high, which is beneficial for the current collector to slide by means of the (111) crystal plane and improve the plasticity of the current collector.

[0217] In some embodiments, the texture coefficient of the (200) crystal plane in the X-ray diffraction spectrum of the first metal foil layer is 15%-50%, and can be selected as 25%-40%.

[0218] The proportion of texture coefficient of (200) crystal plane can be obtained by referring to the (111) texture coefficient proportion test above.

[0219] In some embodiments, the texture coefficient of the (200) crystal plane in the X-ray diffraction spectrum of the first metal foil layer can be selected as 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value between the two.

[0220] When the proportion of the texture factor of the (200) crystal plane in the first metal foil layer is within the above range, the (200) crystal plane exhibits a preferred orientation, which further improves the fracture elongation and bending resistance of the current collector. The reason for this is likely related to the formation of new phases in the metal layer. The proportion of the texture factor of the (200) crystal plane in a pure metal layer is usually low. The fact that the proportion of the texture factor of the (200) crystal plane in the first metal foil layer is within the above range means that the first metal foil layer may include new phases or coordinated deformation between multiple phases, thereby improving the plasticity of the current collector, increasing the fracture elongation of the current collector when the battery reaches 80% SOH, and improving the cycle life of the battery cell.

[0221] In some implementations, the total thickness of the first metal foil layer accounts for 30%-100% based on the total thickness of the current collector.

[0222] In some implementations, the percentage of the total thickness of the first metal foil layer, based on the total thickness of the current collector, can be tested using any method known in the art. The percentage of the total thickness of the first metal foil layer is the ratio of the total thickness of the first metal foil layer to the thickness of the current collector. The total thickness of the first metal foil layer can be measured when observing the layered structure of the current collector.

[0223] In some implementations, based on the total thickness of the current collector, the total thickness percentage of the first metal foil layer can be selected as 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or any value range between the two.

[0224] In some implementations, the total thickness of the first metal foil layer accounts for 30%-85% based on the total thickness of the current collector.

[0225] Within the above-mentioned range, the total thickness of the first metal foil layer can further improve the bending resistance of the current collector by the coordinated effect of different structures or components in different foil layers, thereby reducing the probability of the current collector breaking in the inner ring of the winding cell with high bending degree, which would lead to battery failure.

[0226] In some embodiments, the current collector further includes at least one second metal layer, the second metal layer including a second element, the second element including one or more of Cu, Ag, and Au, and the mass content of the second element in the second metal layer is greater than or equal to 90%.

[0227] During their research on current collectors, the inventors discovered that current collectors containing a nickel-iron alloy layer exhibit high tensile strength. However, the size difference between nickel and iron atoms in the first metal foil layer leads to the formation of a solid solution, resulting in lattice distortion. This distortion hinders dislocation slip, making deformation of the first metal foil layer more difficult, thus reducing the energy absorbed before fracture and decreasing toughness. In this case, a second metal layer is placed on at least one surface of the first metal foil layer. The second metal layer can compensate for the poor toughness of the first metal foil layer with its own superior toughness, improving the overall toughness of the current collector. However, the addition of the second metal layer weakens the overall strength of the current collector. Therefore, further design is needed for current collectors containing nickel-iron alloy to better balance tensile strength and toughness, aiming to maintain good cycle performance when used in batteries containing high-expansion negative electrode materials. In some embodiments of this application, a second metal layer is disposed on at least one surface of the first metal foil layer, which can improve the toughness of the negative electrode current collector. At the same time, by controlling the average grain size of the first metal foil layer within a suitable range (e.g., the average grain size of the first metal foil layer is 5nm-50nm), the first metal foil layer can have high tensile strength and good toughness. When matched with the second metal layer, the negative electrode current collector can achieve both high tensile strength and good toughness with a relatively small thickness (e.g., a thickness of 2μm-10μm).

[0228] In some embodiments, the battery cell includes an electrode assembly, which includes a negative electrode sheet. The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes a silicon-based material. The negative current collector includes a first metal foil layer and a second metal layer located on at least one surface of the first metal foil layer. The first metal foil layer includes nickel and iron elements. The average grain size of the first metal foil layer is 5nm-50nm. The thickness of the negative current collector is 3μm-9μm.

[0229] In this battery cell, a second metal layer is disposed on at least one surface of the first metal foil layer. This improves the toughness of the negative electrode current collector. Simultaneously, controlling the average grain size of the first metal foil layer within a suitable range allows it to possess both high tensile strength and good toughness. Matching the second metal layer, this enables the negative electrode current collector to achieve both high tensile strength and good toughness with a relatively small thickness (e.g., 3μm-9μm). For example, if the average grain size of the first metal foil layer is too small, although it can possess high tensile strength, the increased number of grain boundaries, internal microcracks, and defect phases can lead to brittle fracture within the grain boundaries. Under external force, the negative electrode current collector is prone to brittle fracture. Conversely, if the average grain size of the first metal foil layer is too large, its internal structure becomes loose, making it difficult to maintain high tensile strength, thus increasing the risk of fracture of the negative electrode current collector under stress. Therefore, in the above-mentioned battery cell, by adapting the first metal foil layer and the second metal layer, the negative electrode current collector can achieve both high tensile strength and good toughness with a smaller thickness, thereby enabling the battery to improve its cycle performance while increasing energy density.

[0230] Furthermore, the first metal foil layer, which includes nickel and iron, has high stability in the electrochemical environment and is not easily corroded. It also has high tensile strength and plasticity, which enables the electrode to maintain a high ability to resist external casing pressure during cycling and to retain a high residual elongation at break after stretching, thereby improving the cycle performance of the battery.

[0231] In some embodiments, the mass content percentage of the second element in the second metal layer can be selected as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.9%, or any value range between the two.

[0232] In some embodiments, the average grain size of the second metal layer is greater than the average grain size of the first metal foil layer.

[0233] In some embodiments, the average grain size of the second metal layer is greater than or equal to 40 nm.

[0234] The elements in the second metal layer can be the same as or different from those in the first metal foil layer, but the average grain size of the second metal layer differs from that of the first metal foil layer. The average grain size of the second metal layer can be tested with reference to the average grain size of the first metal foil layer described above.

[0235] In some embodiments, the average grain size of the second metal layer can be selected as 90nm, 91nm, 92nm, 93nm, 94nm, 95nm, 96nm, 97nm, 98nm, 99nm, 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, 21nm, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm, 280nm, 290nm, 300nm, 320, 340, 360, 380, 400, or any value range between the two. For example, the average grain size of the second metal layer can be 90nm-400nm, 90nm-350nm, 90nm-300nm, 90nm-250nm, 90nm-200nm, 90nm-150nm, 100nm-400nm, 100nm-350nm, 100nm-300nm, 100nm-250nm, 100nm-150nm, 110nm-400nm, 110nm-350nm, 110nm-300nm, 110nm-250nm, or 110nm-150nm.

[0236] The second metal layer with relatively large grains has a relatively high degree of grain boundary tortuosity. During crack propagation, it needs to overcome greater resistance and generate more crystal plane slip, which reduces the probability of brittle fracture of the current collector during cycling. It can effectively improve the plasticity of the current collector and reduce the risk of battery failure caused by the current collector breaking in the inner ring of the wound cell.

[0237] In some embodiments, the second metal layer includes copper, with Cu accounting for more than or equal to 90% of the mass content in the second metal layer, and the average grain size of the second metal layer is 90nm-400nm; optionally, it is 100-250nm.

[0238] In some implementations, the total thickness of the second metal layer accounts for 15%-70% based on the total thickness of the current collector.

[0239] In some implementations, based on the total thickness of the current collector, the total thickness percentage of the second metal layer can be selected as 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any value range between the two.

[0240] The thickness of the second metal layer within the above range is beneficial for balancing the strength and flexibility of the current collector, while reducing the risk of crack failure of the current collector in the inner ring with high bending degree and the outer ring with large expansion force, thereby improving the cycle life of the battery.

[0241] In some embodiments, the current collector includes a first metal foil layer and a second metal layer that are sequentially and alternately stacked in the thickness direction.

[0242] In some implementations, at least a portion of the second metal layer is close to the surface of the current collector.

[0243] The surface of the current collector is where the deformation is greatest during the winding and bending process, and it is also where the stress is most concentrated. Having at least a portion of the second metal layer close to the surface of the current collector can minimize the probability of cracks forming during winding and bending, thus improving the cycle life of the battery cell.

[0244] In some embodiments, the second metal layer includes a second element, which includes one or more of Cu, Ag, and Au, and the mass content of the second element in the second metal layer is greater than or equal to 99%, and the average grain size of the second metal layer is 40nm-150nm.

[0245] The elemental composition of the second metal layer can be obtained by energy dispersive spectroscopy (EDS) or plasma atomic emission spectrometry (PISA). The mass percentage of the second element in the second metal layer can be obtained by separating the second metal layer from the current collector and analyzing it using PISA.

[0246] The second element is a highly ductile metallic element that can effectively improve the bending resistance of the current collector and improve the cycle life of the battery cell without significantly sacrificing the strength of the current collector.

[0247] In some embodiments, the second metal layer includes copper, with the mass content of copper in the second metal layer being greater than or equal to 99%, and the average grain size of the second metal layer being 90nm-400nm; optionally, it is 100-250nm.

[0248] Using pure copper in the second metal layer helps to further improve the ductility of the second metal layer, improve the bending resistance of the current collector, and reduce the probability of cracks in the inner ring of the cell.

[0249] The average grain size of the second metal layer is within the above range, which allows the current collector to have both strength and plasticity while also giving the second metal layer a high surface roughness. This is beneficial to improving the bonding strength between the second metal layer and its adjacent layers, and further improving the cycle stability of the battery.

[0250] In some implementations, such as Figure 1 As shown in Figure (a), the current collector 10 includes two second metal layers 102 close to the surface of the current collector in the thickness direction and a first metal foil layer 101 disposed between the two second metal layers 102 in the thickness direction.

[0251] In some implementations, please refer to [the documentation / reference]. Figure 1 A passivation layer 103 is provided on the surface of the current collector 10.

[0252] In some embodiments, the passivation layer includes any component capable of reducing metal oxidation on the current collector surface, including but not limited to chromides and oxides.

[0253] In some implementations, please refer to [the documentation / reference]. Figure 1 The surface scan results of the energy spectrum in Figure (b) show that the second metal layer near the current collector surface mainly consists of copper, and the first metal foil layer disposed between the two second metal layers mainly consists of nickel-iron alloy.

[0254] In some implementations, the current collector includes a first metal foil layer.

[0255] In some embodiments, the current collector comprises a nickel-based alloy, wherein the nickel content in the current collector is 40%-95% by mass.

[0256] In some embodiments, the current collector comprises a nickel-iron-based alloy, wherein the mass content of nickel and iron in the current collector is greater than that of the other metal elements, the mass content of nickel in the current collector is greater than or equal to 35%, and the mass content of iron in the current collector is 10%-60%.

[0257] The current collector in this embodiment has high tensile strength, which helps to delay the time when cracks occur on the outer ring of the battery cell and improve the cycle life of the battery.

[0258] In some implementations, the range of iron content in the current collector is less than or equal to 6%.

[0259] The range of iron content in the current collector can be tested using any method known in the art. As an example, the battery is disassembled, the negative electrode is obtained, the film layer on the negative electrode is removed, and the current collector is obtained. Five different regions are selected on the current collector; for a wound cell, the minimum distance between the different regions is 1 m; each region has an area of ​​at least 0.25 dm².2 The first metal foil layer sample was analyzed by ICP testing at different collection points to determine the mass content of iron in the first metal foil layer. The maximum mass content of iron in the obtained data was subtracted from the minimum mass content of iron as the range of iron mass content in the current collector.

[0260] In some implementations, the range of iron content in the current collector can be selected as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or any value between the two.

[0261] The range of iron content in the current collector being within the above range means that the composition of different regions in the current collector is uniform and there is no obvious component segregation. This is beneficial to reducing the probability of local stress and strain concentration or accumulation, improving the consistency of current collector performance, delaying the occurrence time of cell crack failure, and improving the cycle life of battery cells.

[0262] In some embodiments, the current collector includes Ni, FeNi3, Fe3Ni2, and Ni 0.64 Fe 0.36 One or more of the Ni1Fe1 phase.

[0263] The identification of the aforementioned phases can be obtained by comparing the X-ray diffraction pattern of the current collector sample with the standard pattern of the Joint Committee on Powder Diffraction Standards (JCPDS).

[0264] The presence of the aforementioned phases in the current collector is beneficial for further improving the plasticity of the current collector and increasing the cycle life of the battery cell.

[0265] In some implementations, the total thickness of the current collector is 2 μm-10 μm.

[0266] In some embodiments, the total thickness of the current collector is 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or any value between two of these. For example, the total thickness of the current collector can be 3 μm-9 μm or 4 μm-8 μm.

[0267] The current collector has a low thickness, which allows for the transfer of mass and space to increase the loading of active materials, thus improving battery mass energy density and / or volumetric energy density while increasing battery cycle life.

[0268] In some implementations, the thickness range of the current collector is less than or equal to 0.5 μm.

[0269] In some implementations, the thickness range of the current collector can be selected as 0, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, or any value range between the two.

[0270] The range of current collector thickness can be tested using methods known in the art. As an example, the current collector cross-section is collected at different sites using argon ion polishing technology. For wound cells, the minimum distance between different sites is 1m. The thickness of the current collector cross-section at different sites is measured under an electron microscope, obtaining no less than 10 data points. The maximum thickness of the current collector minus the minimum thickness of the current collector in the collected data is taken as the range of current collector thickness.

[0271] The fact that the thickness variation of the current collector is within the above range indicates that the current collector has good thickness consistency, which can reduce the probability of stress concentration in local areas, reduce the risk of premature current collector failure, and improve the cycle life of the battery.

[0272] In some embodiments, the current collector includes at least one first metal foil layer and at least two second metal layers.

[0273] In some embodiments, the first metal foil layer includes a nickel-based alloy, wherein the mass percentage of nickel in the first metal foil layer is 40%-95%; the second metal layer includes copper, wherein the mass percentage of Cu in the second metal layer is greater than or equal to 90%; and the average grain size of the second metal layer is 90nm-400nm, optionally 100-250nm.

[0274] In this embodiment, the current collector, through the composite of multiple metal layers, balances the tensile strength and bending resistance of the current collector, thereby reducing the probability of cracks appearing on both the outer and inner rings of the wound cell, which is beneficial to improving the battery cycle life.

[0275] In some embodiments, the first metal foil layer comprises a nickel-iron-based alloy, wherein the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass percentage of nickel in the first metal foil layer is greater than or equal to 35%, and the mass percentage of iron in the first metal foil layer is 10%-60%; the second metal layer comprises copper, wherein the mass percentage of Cu in the second metal layer is greater than or equal to 90%; the average grain size of the second metal layer is 90nm-400nm, optionally 100-250nm.

[0276] The current collector in this embodiment combines multiple metal layers, taking into account the tensile strength, plasticity, bending resistance and low cost of the current collector. It can simultaneously reduce the probability of cracks appearing on the outer and inner rings of the wound cell, which is beneficial to improving the cycle life of the battery.

[0277] In some implementations, based on the total mass of the current collector, the mass percentage of Ni is 25%-70%, the mass percentage of Fe is 1%-40%, and the mass percentage of Cu is 15%-65%.

[0278] In some implementations, based on the total mass of the current collector, the mass percentage of Ni can be selected as 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any value between two of these; the mass percentage of Fe can be selected as 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any value between two of these; and the mass percentage of Cu can be selected as 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or any value between two of these.

[0279] Current collectors with a composition within the above range have both good strength and elongation, which helps to delay the time when cracks appear in the current collector during long cycles and improve the cycle life of the battery.

[0280] In some embodiments, the first metal foil layer includes Ni, FeNi3, Fe3Ni2, and Ni 0.64 Fe 0.36 One or more of the Ni1Fe1 phase.

[0281] The identification of the aforementioned phases can be obtained by comparing the X-ray diffraction pattern of the first metal foil layer sample with the standard pattern of the Joint Committee on Powder Diffraction Standards (JCPDS).

[0282] The presence of the aforementioned phases in the first metal foil layer is beneficial for further improving the plasticity of the current collector and increasing the cycle life of the battery cell.

[0283] In some embodiments, the tensile strength of the current collector is 0.9 GPa-2 GPa under test conditions of room temperature and tensile speed of 50 ± 0.5 mm / min.

[0284] The tensile strength of the current collector at room temperature can be obtained by testing its tensile fracture curve. The specific test method can be found in GB / T5230-1995 "Electrolytic Copper Foil" standard. As an example, at least four current collector specimens with a length of 200±0.5 mm, a width of 15±0.25 mm, and a gauge length of 50±0.5 mm should be cut. The specimens should be continuously loaded at a tensile speed of 50±0.5 mm / min at room temperature until fracture. The maximum tensile stress of the specimen during the tensile fracture process is taken as the tensile strength of the specimen, expressed in MPa or GPa. The maximum tensile stress of the specimen is calculated by dividing the maximum load borne by the specimen during the tensile fracture process by the cross-sectional area of ​​the current collector. The cross-sectional area of ​​the current collector is calculated by multiplying its width by its thickness. The thickness of the current collector is measured using a micrometer, and the width of the current collector is the standard specimen width of 15 mm. At least four current collector specimens should be tested, and the average value should be taken as the tensile strength of the current collector. It is understandable that the current collector sample can be obtained from a freshly prepared current collector or from a current collector obtained from disassembling a battery.

[0285] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the tensile strength of the current collector can be selected from 0.9 GPa, 1.0 GPa, 1.1 GPa, 1.2 GPa, 1.3 GPa, 1.4 GPa, 1.5 GPa, 1.6 GPa, 1.7 GPa, 1.8 GPa, 1.9 GPa, 2 GPa, or any value range between the two. Optionally, the tensile strength of the current collector is 1.2 GPa-2 GPa, 1.2 GPa-1.5 GPa, 1.4 GPa-2 GPa, etc.

[0286] The aforementioned current collector has high tensile strength, which can improve the cell's resistance to expansion and improve the cycle life of the battery cell.

[0287] It is understood that the negative electrode current collector includes a lateral direction and a longitudinal direction. The lateral direction refers to the lateral extension direction of the negative electrode current collector, and the longitudinal direction refers to the direction perpendicular to the lateral extension direction of the negative electrode current collector. The dimension in the lateral direction is larger than the dimension in the longitudinal direction. In some embodiments, the lateral direction of the negative electrode current collector represents the length direction of the negative electrode current collector, and the longitudinal direction of the negative electrode current collector represents the width direction of the negative electrode current collector.

[0288] In some embodiments, the electrode assembly in the battery includes a wound structure. In this case, the negative electrode current collector has a transverse direction that is the same as the winding direction of the electrode assembly.

[0289] In some implementations, the tensile strength of the current collector refers to its transverse tensile strength.

[0290] In some implementations, fatigue testing is performed at room temperature and with 1% extended load, and the current collector undergoes 500 or more fatigue cycles.

[0291] Referring to the tensile strength test method for current collectors described above, the tensile stress corresponding to a deformation rate of 1% in the first tensile test of the current collector was determined. Current collector specimens with a length of 200±0.5 mm, a width of 15±0.25 mm, and a gauge length of 50±0.5 mm were cut and mounted on a tensile testing machine. The tensile stress corresponding to a deformation rate of 1% in the first tensile test of the current collector was used as the maximum tensile stress. Repeated rebound tests were performed until the sample fractured. The number of tensile rebounds from the first tensile rebound to the final fracture was recorded as the fatigue cycle number of the sample. One complete tensile and rebound cycle was considered as one fatigue cycle. At least four current collector specimens were tested, and the average value was taken as the fatigue cycle number of the current collector. It is understood that the current collector specimens can be obtained from freshly prepared current collectors or from current collectors disassembled from batteries.

[0292] In some implementations, fatigue testing is performed at room temperature and 1% of the extended load, and the number of fatigue cycles of the current collector can be selected as 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000 or any value between the two.

[0293] In existing technologies, the fatigue resistance of current collectors at a 1% deformation rate is generally no more than 1000 cycles, which is insufficient to meet the increasingly stringent market requirements for the cycle life of battery cells, and even more so to withstand the higher expansion forces generated by next-generation high-energy-density active materials during cycling. Figure 4 As shown in Figure (b), the current collector in the prior art undergoes significant irreversible deformation during fatigue testing, causing the current collector's malleable space to continuously shrink until fatigue fracture occurs. However, as... Figure 4 As shown in Figure (a), the current collector in this embodiment can withstand higher elongation loads under the same elongation rate and will not produce significant irreversible deformation in each cycle test, which greatly increases the number of cycles that the current collector can withstand. This indicates that the current collector can effectively withstand the reciprocating expansion of the battery cell during the cycle, delay the time when the current collector will experience fatigue fracture, and improve the cycle life of the battery cell.

[0294] In some implementations, fatigue testing is performed at room temperature and with 1% extended load, and the current collector undergoes 2,000 to 4,000 fatigue cycles.

[0295] In the embodiments of this application, the fatigue cycle number of the current collector is within the above range, indicating that the current collector can effectively withstand the reciprocating expansion of the battery cell during the cycle, delay the time when the current collector will experience fatigue fracture, and improve the cycle life of the battery cell.

[0296] In some implementations, under test conditions of room temperature and tensile speed of 50 ± 0.5 mm / min, the elongation at break of the current collector is 1%-8%.

[0297] The elongation at break of the current collector at room temperature can be tested using the tensile strength test method described above.

[0298] In some embodiments, under test conditions of room temperature and a tensile speed of 50 ± 0.5 mm / min, the elongation at break of the current collector can be selected as 1%, 1.5%, 2%, 3%, 4%, 5%, 6%, 6.5%, 7%, 8%, or any value range between the two.

[0299] The aforementioned current collector has a high elongation at break, indicating that the current collector has good plasticity, which helps to improve the electrode's ability to withstand cyclic expansion and improve the cycle life of the battery cell.

[0300] In some implementations, under test conditions of room temperature and tensile speed of 50 ± 0.5 mm / min, the elongation at break of the current collector is 2%-5%.

[0301] In some implementations, the current collector withstands 1 to 10 flexural cycles under room temperature testing conditions.

[0302] The bending resistance of the current collector can be tested using methods known in the art. For example, at room temperature, the current collector sample is folded 180° and then rolled back and forth at the fold with a 1.5kg roller. After unfolding, it is observed whether cracking and light transmission occur at the fold. The number of times the rolling caused cracking and light transmission at the fold is recorded. At least ten samples are tested, and the average value is taken as the bending resistance of the current collector.

[0303] In some implementations, under room temperature testing conditions, the current collector's resistance to bending is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 times or any range between two of these values.

[0304] The aforementioned current collector exhibits a high number of bending cycles, indicating that it has good bending resistance, which helps improve the bending resistance of the electrode in the battery cell and improve the cycle life of the battery cell.

[0305] [current collector]

[0306] This application also provides a current collector, which includes any of the characteristics of the current collector in the above-mentioned battery cell.

[0307] This application also provides a method for preparing a current collector, comprising the following steps:

[0308] S10. Provide an anode, a first electroplating solution, and a cathode, and perform electroplating to form a first metal foil layer on the surface of the cathode; wherein, the first electroplating solution includes a first metal source, a primary brightener, a secondary brightener, a stress reliever, and a complexing agent; the primary brightener includes one or more of saccharin or sodium saccharin; the secondary brightener includes one or more of alkynyl alcohol compounds or alkynylamine compounds and their salts; the stress reliever contains unsaturated bonds and acid radicals, and the acid radicals include one or more of sulfate or sulfonate; the first metal source includes one or more of Ni, Fe, Cu, and Cr sources.

[0309] S20. Separate the first metal foil layer from the surface of the cathode to form the first metal foil layer.

[0310] Understandably, during the electroplating process, the cathode rotates relative to the anode located in the electroplating solution, thereby forming a continuous first metal foil layer on the cathode. In the aforementioned method for preparing the negative electrode current collector, a specific type and proportion of primary and secondary brighteners are added to the first electroplating solution used to form the first metal foil layer. The primary brightener provides tensile stress to the formed first metal foil layer, while the secondary brightener provides compressive stress. Their synergistic effect yields a negative electrode current collector with suitable tensile strength. Simultaneously, their synergistic effect enhances grain refinement in the first metal foil layer and strengthens grain growth along the banding direction of the first metal foil layer. This results in a difference between the transverse and longitudinal tensile strengths of the negative electrode current collector, but this difference is controlled within a small range. This ensures that both the transverse and longitudinal tensile strengths of the negative electrode current collector are within optimal ranges, meeting the high strength requirements of the battery for the negative electrode current collector. This reduces the risk of breakage of the negative electrode current collector and the electrode sheet containing it, improves the battery's resistance to stresses such as expansion, and enhances the battery's cycle life. If the ratio of primary brightener to secondary brightener in the electroplating solution is too low, it will not significantly enhance the grain growth along the banding direction of the nickel-based first metal foil layer. Consequently, the transverse tensile strength and longitudinal tensile strength of the resulting negative electrode current collector will not differ, and the transverse tensile strength of the negative electrode current collector cannot be within the aforementioned suitable range. If the ratio of primary brightener to secondary brightener in the first electroplating solution is too high, it will increase polarization during the electroplating process, reduce the deposition quality of the first metal foil layer, and decrease the tensile strength of the negative electrode current collector.

[0311] Specifically, the growth of the first metal foil layer in the direction of its travel refers to the length direction of the first metal foil layer.

[0312] Understandably, during the electroplating process, the direction of the first metal foil layer is the same as the length direction of the first metal foil layer.

[0313] In some embodiments, the concentration of the primary brightener in the first electroplating solution is 1.5 g / L to 5 g / L. As an example, the concentration of the primary brightener is 1.5 g / L, 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, 4 g / L, 4.5 g / L, 5 g / L, or any value within the range formed by any two of the above points as endpoints.

[0314] In some embodiments, the concentration of the secondary brightener in the first electroplating solution is 0.2 g / L to 1 g / L. As an example, the concentration of the secondary brightener is 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1 g / L, or any value within a range defined by any two of the above points.

[0315] In some embodiments, the total number of carbon and oxygen atoms on the main chain of the alkynol compound is ≥4, optionally 4-8; as an example, the alkynol compound includes, but is not limited to, one or more of butynediol, butynediol diethoxy ether or propynediol ethoxy compound.

[0316] In some embodiments, the total number of carbon and nitrogen atoms on the main chain of the acetyleneamine compound and its salt is ≥4, optionally 4-8; as an example, the acetyleneamine compound and its salt include, but are not limited to, N,N-diethylpropynylamine formate.

[0317] In some embodiments, the unsaturated bonds of the stress-relieving agent are easily adsorbed onto the active sites on the electrode surface, hindering the rapid deposition of metal ions and refining the grains of the first metal foil layer. Grain refinement reduces grain boundary stress accumulation and lowers the internal stress of the coating itself. Acid radicals can adjust the interfacial tension between the electroplating solution and the electrode, improve the wettability of the electroplating solution, and allow metal ions to be deposited more uniformly on the substrate surface, avoiding excessively thick local coatings or stress concentration, thereby improving the toughness of the current collector.

[0318] In some embodiments, the unsaturated bond includes one or more of alkenyl and alkynyl groups. Optionally, the unsaturated bond includes one or more of propenyl and propargyl groups.

[0319] Optionally, the stress reliever includes one or more of sodium propylene sulfonate, sodium vinyl sulfonate, sodium aminosulfonate, sodium benzene sulfonate, sodium ethoxylated alkyl sulfate, and sodium 2-ethylhexyl sulfate.

[0320] In some embodiments, the concentration of the stress reliever in the first electroplating solution is 0.1 g / L to 0.5 g / L. For example, the concentration of the stress reliever in the electroplating solution can be 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, or any value within the range of any two of the above values.

[0321] In some embodiments, the first metal source includes one or more of Ni, Fe, Cu, and Cr sources.

[0322] In some embodiments, the nickel source includes one or more of nickel sulfate, nickel chloride, and nickel carbonate. Nickel sulfate, for example, is NiSO4·6H2O. Optionally, the concentration of the nickel source in the first electroplating solution is 150 g / L to 250 g / L.

[0323] In some embodiments, the Fe source includes one or more of ferrous sulfate, ferrous chloride, and iron powder. Ferrous sulfate, for example, is FeSO4·7H2O. Optionally, the concentration of the iron source in the first electroplating solution is 20 g / L to 50 g / L.

[0324] In some embodiments, the first electroplating solution comprises nickel sulfate and ferrous sulfate. Further, the concentration of ferrous sulfate in the first electroplating solution is 20 g / L-50 g / L. Further, the concentration of nickel sulfate in the first electroplating solution is 150 g / L-250 g / L.

[0325] In some embodiments, the complexing agent includes one or more of citric acid, sodium citrate, sodium gluconate, and gluconic acid. The main function of the complexing agent is to coordinate with metal ions in the electroplating solution, guiding their deposition on the cathode surface. The amount of complexing agent added affects the ratio of nickel to iron in the first metal foil layer, thereby affecting the tensile strength of the first metal foil layer. Further, the concentration of the complexing agent in the first electroplating solution is 20 g / L-40 g / L. As an example, it is any value within the range of 20 g / L, 30 g / L, 40 g / L, or any two of the above points as endpoints.

[0326] In some embodiments, the first electroplating solution may further include a conductive agent; optionally, the conductive agent includes one or more of sodium chloride and ammonium chloride. Optionally, the concentration of the conductive agent in the electroplating solution is 10 g / L-50 g / L, for example, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, or any value within the range defined by any two of the above points. The conductive agent can enhance ion transport capability and improve deposition efficiency.

[0327] In some embodiments, the first electroplating solution may further include a stabilizer; optionally, the stabilizer includes one or more of boric acid, citric acid, and fluoroborate. Optionally, the concentration of the stabilizer in the electroplating solution is 2 g / L - 40 g / L, for example, 20 g / L, 30 g / L, 40 g / L, or any value within the range defined by any two of the above points. The stabilizer's main function is to maintain pH stability and prevent excessive pH shift due to the hydrogen evolution reaction, which would increase the degree of reaction polarization and thus affect the foil formation efficiency of the first metal foil layer. Furthermore, during the formation of the first metal foil layer, it can also cause excessive deviation of the nickel content from the preset value, resulting in uneven solid solution formation.

[0328] In some embodiments, the first electroplating solution may further include an antioxidant; optionally, the antioxidant includes one or more of ascorbic acid, hydroxylamine sulfate, catechol, and hydroquinone. Optionally, the concentration of the antioxidant in the first electroplating solution is 1 g / L - 5 g / L, for example, 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, or any value within the range defined by any two of the above points. The main function of the antioxidant is to prevent air oxidation of the first electroplating solution, for example, to prevent the oxidation of ferrous ions in the first electroplating solution to ferric ions. Excessive ferric ion content will increase the number of defect vacancies in the first metal foil layer, affecting the grain boundary density and leading to a decrease in tensile strength and elongation.

[0329] In some embodiments, the first electroplating solution comprises: ferrous sulfate 20 g / L-50 g / L, nickel sulfate 150 g / L-250 g / L, sodium chloride 10 g / L-50 g / L, stabilizer 20 g / L-60 g / L, primary brightener 1.5 g / L-5 g / L, secondary brightener 0.2 g / L-1 g / L, and complexing agent 20 g / L-40 g / L.

[0330] Furthermore, the first electroplating solution comprises: ferrous sulfate 20 g / L-50 g / L, nickel sulfate 150 g / L-250 g / L, sodium chloride 10 g / L-50 g / L, boric acid 20 g / L-60 g / L, sodium saccharin 1.5 g / L-5 g / L, butynediol 0.2 g / L-1 g / L, and sodium citrate 20 g / L-40 g / L.

[0331] Furthermore, the electroplating temperature for forming the first metal foil layer is 50℃-60℃. Temperature control within this range helps to increase ion transport speed and improve deposition efficiency.

[0332] Furthermore, the current density for the electroplating process that forms the first metal foil layer is 3 A / dm². 2 -10A / dm 2 As an example, this current density could be 3 A / dm³.2 6A / dm 2 8A / dm 2 10A / dm 2 Alternatively, any value within the range defined by any two of the above points as endpoints. Adjusting the current density within this range is beneficial for increasing the electroplating speed and improving deposition efficiency.

[0333] Furthermore, the pH value of the first electroplating solution is 2-4.

[0334] Further, the flow rate of the first electroplating solution is 40 L / min-80 L / min; as an example, it can be any value within the range of 40 L / min, 50 L / min, 60 L / min, 70 L / min, 80 L / min, or any two of the above points as endpoints. During the electroplating process to form the first metal foil layer, taking a nickel-iron alloy layer as an example, increasing the flow rate of the electroplating solution usually increases the iron content in the coating. This is because increasing the flow rate of the electroplating solution enhances convection, improving the mass transfer efficiency of the cathode surface. Since the concentration of ferrous ions (Fe²⁺) in the electroplating solution is usually significantly lower than that of divalent nickel ions (Ni²⁺), and the reduction reaction of Fe²⁺ is controlled by the diffusion step, increasing the flow rate accelerates the transport of Fe²⁺ to the cathode surface, reducing the consumption of Fe²⁺ in the cathode diffusion layer, making it more readily involved in the electrodeposition reaction, thereby increasing the iron content in the coating.

[0335] In some embodiments, S20 is followed by: S30, electroplating the first metal foil layer with a second electroplating solution to form a metal layer on at least one side of the first metal foil layer.

[0336] In some embodiments, the second electroplating solution includes a second metal source, which includes at least one of Cu, Ag, Au, Ni, Zn, or Cr.

[0337] Furthermore, the concentration of the second metal source in the second electroplating solution is 200 g / L-250 g / L. In some examples, the second metal source in the second electroplating solution includes divalent copper ions.

[0338] Optionally, the Cu source includes one or more of copper sulfate, elemental copper, and copper chloride. Optionally, the components of the second electroplating solution include CuSO4·5H2O.

[0339] Optionally, the second electroplating solution includes 200g / L-250g / L of copper sulfate.

[0340] In some embodiments, the second electroplating solution also includes one or more of a brightener, a conductive agent, and a pH adjuster.

[0341] Further, the brightener includes one or more of sodium dithiopropane sulfonate, polyethylene glycol, tetrahydrothiazolium thione, or benzotriazole. Optionally, the concentration of the brightener in the second electroplating solution is 0.5 g / L to 3 g / L. The main function of the brightener is to refine the grains, thereby improving the tensile strength and elongation of the second metal layer.

[0342] Furthermore, the second electroplating solution also includes a conductive agent, which includes chlorides. Optionally, the chloride includes one or more of copper chloride and sodium chloride. Optionally, the concentration of the conductive agent in the second electroplating solution is 5 g / L-25 g / L; as an example, it is any value within the range of 5 g / L, 8 g / L, 10 g / L, 15 g / L, 20 g / L, 25 g / L, or any two of the above points as endpoints.

[0343] Further, the pH adjuster includes one or more of sulfuric acid or hydrochloric acid. Optionally, the concentration of the pH adjuster in the second electroplating solution is 20 g / L-60 g / L. The function of the pH adjuster is to adjust the pH value and stabilize the acid-base balance of the electroplating solution. Further, the pH value of the second electroplating solution is less than 1.

[0344] As an example, the second electroplating solution, in addition to the metal source, also includes sulfuric acid, polyethylene glycol, and sodium polydisulfide dipropane sulfonate. Optionally, the second electroplating solution includes 200 g / L-250 g / L copper sulfate, 20 g / L-60 g / L sulfuric acid, 0.5 g / L-5 g / L polyethylene glycol, and 0.5 g / L-3 g / L sodium polydisulfide dipropane sulfonate.

[0345] Furthermore, the electroplating temperature for the second electroplating treatment is 15℃-40℃. Temperature control within this range helps to increase ion transport speed and improve deposition efficiency.

[0346] Furthermore, the current density for forming the second metal layer is 1 A / dm. 2 -10A / dm 2 As an example, this current density could be 1 A / dm³. 2 2A / dm 2 3A / dm 2 4A / dm 2 5A / dm 2 8A / dm 2 10A / dm 2 Alternatively, any value within the range defined by any two of the above points as endpoints. Adjusting the current density within this range is beneficial for improving deposition efficiency and coating quality.

[0347] In some embodiments, the anode is an insoluble anode. In this application, an "insoluble anode" refers to an anode that does not dissolve or dissolves very little when current passes through it. Its core function is to provide a platform for electron transfer, promoting the oxidation reaction of ions in the electroplating solution on its surface. Using an insoluble anode instead of a traditional soluble anode can reduce the problems of uneven foil thickness and coating contamination associated with soluble anodes. It also ensures good thickness consistency of the nickel-iron alloy foil in both the conveying direction and the direction perpendicular to the conveying direction, reducing the contamination of the plating solution and coating by anode sludge.

[0348] Without limitation, the material of the insoluble anode includes titanium metal. Specifically, it can be, for example, a titanium metal mesh. Optionally, the surface of the insoluble anode can be provided with an anti-oxidation coating, the material of which is, for example, platinum, iridium-tantalum alloy, ruthenium-iridium alloy, rhodium, etc.

[0349] [Positive electrode plate]

[0350] 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.

[0351] The positive electrode current collector can be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer material base layer may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0352] 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.

[0353] The positive electrode active material may be a positive electrode active material known in the art for use in battery cells.

[0354] When the battery cell of this application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, lithium phosphates, and their respective modified compounds. Examples of 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 lithium phosphates may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds.

[0355] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material for a lithium-ion battery may include materials with the general formula Li. a Ni b Co c M d O e A f One 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.

[0356] In some embodiments, as an example, the positive electrode active material for lithium-ion batteries may include 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 One or more of O2, LiFePO4 and LiMnPO4.

[0357] 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.

[0358] [Electrolytes]

[0359] The electrolyte used in this application is not specifically limited and may be at least one of liquid electrolyte, gel electrolyte or solid electrolyte.

[0360] In some embodiments, the electrolyte is a liquid electrolyte (i.e., an electrolyte solution), which includes an electrolyte salt and a solvent.

[0361] The type of electrolyte salt is not specifically limited and can be selected according to actual needs.

[0362] When the battery cell 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 bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0363] 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 ethylene 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).

[0364] 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 properties of the battery cell, such as additives that improve the overcharge performance of the battery cell, additives that improve the high-temperature performance of the battery cell, and additives that improve the low-temperature power performance of the battery cell.

[0365] In some embodiments, the electrolyte is a solid electrolyte. Solid electrolytes include one or more of sulfides, oxides, and polymers.

[0366] In some embodiments, the sulfide electrolyte may be a compound containing sulfur atoms (S), exhibiting the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and exhibiting electronic insulation.

[0367] In some embodiments, the oxide electrolyte may be a compound containing oxygen atoms (O), exhibiting the ionic conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and exhibiting electronic insulation.

[0368] In some embodiments, the polymer electrolyte may be a solid polymer electrolyte formed by adding a polymer resin to a separately solvated lithium salt, or a polymer gel electrolyte formed by impregnating a polymer resin with an organic electrolyte containing an organic solvent and a lithium salt.

[0369] [Isolation membrane]

[0370] 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.

[0371] 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.

[0372] 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.

[0373] In some embodiments, the battery cell may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0374] 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).

[0375] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. Figure 5 The example shown is a square-structured battery cell 5.

[0376] In some embodiments, such as Figure 6 As shown, the outer packaging may include a housing 51 and a cover plate 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 plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, negative electrode sheet, 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 number of electrode assemblies 52 contained in the battery cell 5 may be one or more, which can be adjusted according to requirements.

[0377] The method for preparing the battery cell of 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 battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After vacuum sealing, settling, formation, and shaping processes, a battery cell is obtained.

[0378] In some embodiments, the battery cell includes an electrode assembly, which includes a positive electrode, a solid electrolyte, and a negative electrode. The solid electrolyte is located between the positive and negative electrode, and the negative electrode includes a negative current collector, which is the aforementioned current collector.

[0379] Optionally, the battery cell may include a solid-state battery.

[0380] Optionally, the negative electrode current collector includes the first metal foil layer described above.

[0381] In some implementations, the solid electrolyte includes a sulfide.

[0382] Optionally, the sulfide includes one or more of the following substances: Li3PS4, Li7P3S 11 Li6PS5Cl, Li 10 GeP2S 12 , Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-H2S, Li2S-P2S5-H2S-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li 2SLi2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, Li2S-P2S5-Al2S3, Li2S-GeS2, Li2S-GeS2-ZnS, Li2S-Ga2S3, Li2S-GeS2-Ga2S3, Li2S-GeS2-P2S5, Li2S-GeS2-Sb2S5, Li2S-GeS2-Al2S3, Li2S-SiS2, L i2S-Al2S3, Li2S-SiS2-Al2S3, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4.

[0383] Sulfide solid electrolytes have high conductivity, which helps reduce the internal resistance of the battery and improve its power performance. However, sulfide solid electrolytes can corrode traditional copper foil negative electrode current collectors, leading to damage to the negative electrode current collector and thus deteriorating battery performance. In some embodiments of the solid-state battery of this application, the first metal foil layer has good corrosion resistance, which can reduce the risk of corrosion of the negative electrode current collector and promote the improvement of the cycle performance of the solid-state battery.

[0384] The second aspect of this application provides a battery device, including the battery cell provided in the first aspect of this application, wherein the battery device is at least one of a battery module, a battery pack, and an energy storage device.

[0385] In some embodiments of this application, the battery cells according to this application can be assembled into a battery module. The number of battery cells 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.

[0386] Figure 7 This is a schematic diagram of battery module 4 as an example. Figure 7 As shown, in battery module 4, multiple battery cells 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 battery cells 5 can be fixed in place using fasteners.

[0387] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0388] 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.

[0389] Figure 8 and Figure 9 This is a schematic diagram of battery pack 1 as an example. Figure 8 and Figure 9 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.

[0390] Electrical appliances

[0391] This application also provides an electrical device, which includes a battery cell provided in the first aspect of this application or a battery device provided in the second aspect of this application. The battery cell, 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.

[0392] The electrical device can be equipped with individual battery cells, battery modules, or battery packs according to its usage requirements.

[0393] Figure 10This 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.

[0394] 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 a single battery cell as their power source.

[0395] Example

[0396] 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.

[0397] 1) Preparation of negative electrode current collector

[0398] 1.1 Preparation of the first metal foil layer.

[0399] The electroplating apparatus includes an anode, a first electroplating solution, and a cathode. The anode is a titanium mesh, and the cathode is a titanium roller with a ruthenium-iridium alloy coating on its surface. The first electroplating solution consists of: 30 g / L ferrous sulfate (Fe source), 200 g / L nickel sulfate (Ni source), 20 g / L sodium chloride, 40 g / L boric acid (stabilizer), 2.5 g / L sodium saccharin (primary brightener), 0.2 g / L 1,4-butynediol (secondary brightener), 30 g / L sodium citrate (complexing agent), 0.1 g / L sodium propylene sulfonate (stress reliever), 0.2 g / L sodium dodecyl sulfate (wetting agent), and water as the solvent.

[0400] Electroplating parameters are: current density 8A / dm 2 The temperature was 50℃, the pH of the first electroplating solution was 2.5, and the flow rate of the first electroplating solution was 60L / min.

[0401] A nickel-iron alloy layer is formed by electroplating on a titanium roller, and then the nickel-iron alloy layer is peeled off from the titanium roller. The thickness of the nickel-iron alloy layer is 4μm.

[0402] 1.2 Preparation of the second metal layer.

[0403] The electroplating apparatus includes an anode, a second electroplating solution, and a cathode. The anode is a titanium mesh with a ruthenium-iridium alloy coating on its surface, and the cathode is a nickel-iron alloy layer. The second electroplating solution consists of: 200 g / L copper sulfate, 30 g / L sulfuric acid, 2.0 g / L polyethylene glycol (first additive), 0.2 g / L collagen (second additive), and water as the solvent.

[0404] The electroplating parameters are: electroplating temperature 25℃, current density 7A / dm³. 2 The conductive roller speed is 3m / min, and the pH value is less than 1.

[0405] Copper layers are electroplated on both sides of the nickel-iron alloy layer to form a 1μm copper layer, thus obtaining a negative electrode current collector, which includes a nickel-iron alloy layer and copper layers (second metal layers) disposed on both sides of the nickel-iron alloy layer (first metal foil layer).

[0406] 2) Preparation of negative electrode sheet

[0407] The negative electrode active material (a mixture of silicon carbon material and graphite in a mass ratio of 3:7), conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are dissolved in deionized water in a weight ratio of 88:2:8:2 and mixed evenly to prepare a negative electrode slurry. The negative electrode slurry is then coated evenly on the prepared composite foil once or multiple times, dried to obtain a negative electrode film, and then cold-pressed and slit to obtain a negative electrode sheet.

[0408] 3) Preparation of positive electrode sheet.

[0409] LiNi, the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5. After thorough stirring and mixing, a positive electrode slurry is obtained. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, and after drying, cold pressing, and slitting, a positive electrode sheet is obtained.

[0410] 4) Separating membrane

[0411] Polyethylene separator film is selected.

[0412] 5) Preparation of electrolyte

[0413] In an argon-atmospheric glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), fluoroethylene carbonate (FEC), ethylene carbonate (EC), and ethyl methyl carbonate (EMC) were mixed uniformly at a mass ratio of 1:2:7. Then, 12.5 wt% LiPF6 lithium salt was dissolved in the organic solvent. Next, 0.5 wt% 1,3-propanesulfonate lactone and 0.5 wt% succinic anhydride were added as additives to the above organic solvent, and the mixture was stirred until homogeneous to obtain the electrolyte.

[0414] 6) Battery manufacturing

[0415] 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 cell. The wound cell is placed in a battery casing, dried, and then injected with electrolyte. After formation and settling processes, a lithium-ion battery is obtained.

[0416] Examples 2-4

[0417] The preparation methods of the negative electrode current collector in Examples 2-4 are basically the same as those in Example 1. The difference is that the composition of the first electroplating solution and the electroplating process parameters are different in step 1.1 of the preparation of the nickel-iron alloy layer, which results in different average grain sizes of the nickel-iron alloy layer, as shown in Table 1.

[0418] Examples 5-6

[0419] The preparation methods of the negative electrode current collector in Examples 5-6 are basically the same as those in Example 1. The difference is that the composition of the second electroplating solution and the electroplating process parameters are different when preparing the copper layer in step 1.2 of the preparation of the negative electrode current collector, which results in different average grain sizes of the copper layer, as shown in Table 2.

[0420] Test case

[0421] (1) Bending resistance of the negative electrode current collector

[0422] At 25°C, the current collector sample is folded 180° and then rolled back and forth at the fold with a 1.5kg roller. After unfolding, the sample is observed to see if cracking and light transmission occur at the fold. The number of times the current collector cracks and light transmission occurs is recorded. At least ten samples are tested, and the average value is taken as the bending resistance of the current collector.

[0423] (2) Battery cycle performance

[0424] The cycle performance of the batteries in the examples and comparative examples was tested. The test method was as follows: the battery was charged at room temperature at a rate of 0.33C to a voltage of 4.17V, then charged at a constant voltage of 4.17V to 0.05C, and then discharged at a rate of 0.33C to a voltage of 2.8V. The reversible capacity was measured as C0. This charging and discharging process was repeated until the discharge capacity C of a certain cycle was reached. n The total number of iterations until C0 reaches 80% is denoted as X-Cycle. Where C... n It is the reversible capacity at the nth cycle.

[0425] The test results are shown in Table 1-2.

[0426] Table 1

[0427]

[0428] In Table 1, the concentration of the primary brightener represents the concentration of the primary brightener in the first electroplating solution, in g / L. The concentration of the secondary brightener represents the concentration of the secondary brightener in the first electroplating solution, in g / L. The current density represents the current density during the preparation of the first metal foil layer, in A / dm³. 2 The average grain size of the first metal foil layer is measured in nm. The transverse tensile strength of the negative electrode current collector is measured in MPa. The number of battery cycles is measured in cycles.

[0429] As shown in Table 1, the average grain size of the nickel-iron alloy layer can be adjusted by controlling the preparation process of the nickel-iron alloy layer. Examples 1-4 and Comparative Example 1 demonstrate that when the average grain size of the nickel-iron alloy layer is within a suitable range, the cycle performance of the battery can be improved.

[0430] Table 2

[0431]

[0432] In Table 2, the polyethylene glycol concentration represents the concentration of polyethylene glycol in the second electroplating solution, in g / L. The collagen concentration represents the concentration of collagen in the second electroplating solution, in g / L. The conductive roller speed represents the rotational speed of the conductive roller during the preparation of the second metal layer, in m / min. The current density represents the current density during the preparation of the second metal layer, in A / dm³. 2 The average grain size of the second metal layer is measured in nm. The transverse tensile strength of the negative electrode current collector is measured in MPa. The number of bends is measured in cycles. The number of battery cycles is measured in revolutions.

[0433] As can be seen from Table 2, in the negative electrode current collector, the combination of the first metal foil layer and the second metal layer can enable the negative electrode current collector to have both high tensile strength and good toughness, which can promote the improvement of battery cycle performance.

[0434] Example 7

[0435] (1) Preparation of negative electrode sheet.

[0436] 1) Preparation of negative electrode current collector

[0437] Prepare the first metal foil layer.

[0438] The electroplating apparatus includes an anode, a first electroplating solution, and a cathode. The anode is a titanium mesh, and the cathode is a titanium roller with a ruthenium-iridium alloy coating on its surface. The first electroplating solution consists of: 30 g / L ferrous sulfate (Fe source), 200 g / L nickel sulfate (Ni source), 20 g / L sodium chloride, 40 g / L boric acid (stabilizer), 2.5 g / L sodium saccharin (primary brightener), 0.2 g / L 1,4-butynediol (secondary brightener), 30 g / L sodium citrate (complexing agent), 0.1 g / L sodium propylene sulfonate (stress reliever), 0.2 g / L sodium dodecyl sulfate (wetting agent), and water as the solvent.

[0439] Electroplating parameters are: current density 8A / dm 2 The temperature was 50℃, the pH of the first electroplating solution was 2.5, and the flow rate of the first electroplating solution was 60L / min.

[0440] A nickel-iron alloy layer is electroplated on a titanium roller, and then the nickel-iron alloy layer is peeled off from the titanium roller. The thickness of the nickel-iron alloy layer is 6μm.

[0441] 2) Preparation of negative electrode sheet

[0442] An 8 μm lithium metal layer is placed on the nickel-iron alloy current collector prepared above as the negative electrode active material layer.

[0443] (2) Preparation of positive electrode sheet.

[0444] Solid electrolyte Li6PS5Cl and lithium-containing transition metal oxide LiNi 0.9 Co 0.05 Mn 0.05 O2, conductive agent SP, and binder PVDF are mixed evenly in N-methylpyrrolidone in a ratio of 5:91.5:2:1.5 to prepare a positive electrode slurry. The positive electrode slurry is coated on the surface of the positive electrode current collector aluminum foil and dried, and then cold-pressed to prepare the positive electrode sheet.

[0445] (3) Solid electrolyte layer.

[0446] The solid electrolyte Li6PS5Cl and the binder PTFE were mixed at a mass ratio of 97:3 and then formed into a solid electrolyte layer by cold pressing.

[0447] (4) Battery assembly.

[0448] A solid-state secondary battery is assembled by stacking the positive electrode, solid electrolyte layer, and negative electrode in sequence.

[0449] Examples 8-9

[0450] The preparation methods of the negative electrode current collector in Examples 8-9 are basically the same as those in Example 7. The difference is that the composition of the first electroplating solution and the electroplating process parameters are different when preparing the nickel-iron alloy layer, which in turn makes the average grain size of the nickel-iron alloy layer different, as shown in Table 3.

[0451] Comparative Example 2

[0452] The difference from Example 7 is that the negative electrode current collector is a copper foil with a thickness of 10 μm.

[0453] Examples 7-9, Cycle performance tests of the batteries in Comparative Example 2.

[0454] The battery was charged at room temperature at a rate of 0.33C until the voltage reached 4.17V, then charged at a constant voltage of 4.17V until it reached 0.05C, and then discharged at a rate of 0.33C until the voltage reached 2.8V. The reversible capacity was measured as C0. This charging and discharging process was repeated until the discharge capacity C of a certain cycle was reached. n The total number of iterations until C0 reaches 80% is denoted as X-Cycle. Where C... n This is the reversible capacity at the nth cycle. The results are shown in Table 3.

[0455] Table 3

[0456]

[0457] In Table 3, the concentration of the primary brightener represents the concentration of the primary brightener in the first electroplating solution, in g / L. The concentration of the secondary brightener represents the concentration of the secondary brightener in the first electroplating solution, in g / L. The current density represents the current density during the preparation of the first metal foil layer, in A / dm³. 2 The average grain size of the first metal foil layer is measured in nm. The transverse tensile strength of the negative electrode current collector is measured in MPa. The number of battery cycles is measured in cycles.

[0458] As can be seen from Table 3, the first metal foil layer used in solid-state batteries can effectively improve the cycle performance of solid-state batteries compared to traditional copper foil.

[0459] 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 includes at least one first metal foil layer; the first metal foil layer includes a first element, which includes one or more of Ni, Fe, Cu, and Cr; the average grain size of the first metal foil layer is 5nm-50nm.

2. The current collector according to claim 1, characterized in that, The average grain size of the first metal foil layer is 10nm-45nm, and can be selected as 15nm-40nm.

3. The current collector according to claim 1 or 2, characterized in that, The thickness of the current collector is 2μm-10μm; optionally, it is 3μm-9μm; optionally, it is 4μm-8μm.

4. The current collector according to any one of claims 1 to 3, characterized in that, In the X-ray diffraction spectrum of the first metal foil layer, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane is less than 0.5, and can be selected as 0-0.

3.

5. The current collector according to any one of claims 1 to 4, characterized in that, The current collector satisfies one or more of the following conditions: (1) The first metal foil layer comprises a nickel-based alloy; (2) The first metal foil layer comprises a nickel-based alloy; the mass content of nickel in the first metal foil layer is greater than the mass content of the other metal elements, and the mass content of nickel in the first metal foil layer is less than or equal to 95%; (3) The first metal foil layer comprises an iron-based alloy; the mass content of iron in the first metal foil layer is greater than the mass content of the other metal elements, and the mass content of iron in the first metal foil layer is greater than or equal to 30%; (4) The first metal foil layer comprises a nickel-iron-based alloy; the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass content of nickel in the first metal foil layer is greater than or equal to 35%, and the mass content of iron in the first metal foil layer is less than 65%.

6. The current collector according to any one of claims 1 to 5, characterized in that, The current collector satisfies one or more of the following conditions: (1) The first metal foil layer comprises a nickel-based alloy, wherein the mass percentage of nickel in the first metal foil layer is 40%-95%; (2) The first metal foil layer includes a nickel-iron-based alloy, wherein the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass percentage of nickel in the first metal foil layer is greater than or equal to 35%, and the mass percentage of iron in the first metal foil layer is 10%-60%.

7. The current collector according to any one of claims 1 to 5, characterized in that, The first metal foil layer includes nickel and iron, wherein the mass percentage of nickel in the first metal foil layer is greater than the mass percentage of iron in the first metal foil layer; Optionally, the mass percentage of nickel in the first metal foil layer is 40%-85%; Optionally, the mass percentage of nickel in the first metal foil layer is 55%-85%; Optionally, the mass percentage of iron in the first metal foil layer is 10%-60%, and optionally 15%-40%.

8. The current collector according to any one of claims 1 to 7, characterized in that, In the X-ray diffraction spectrum of the first metal foil layer, the proportion of the texture coefficient of the (111) crystal plane is greater than that of the (200) crystal plane; Optionally, in the X-ray diffraction spectrum of the first metal foil layer, the texture coefficient of the (111) crystal plane accounts for 30%-80%; optionally, in the X-ray diffraction spectrum of the first metal foil layer, the texture coefficient of the (200) crystal plane accounts for 15%-50%, and can be 25%-40%.

9. The current collector according to any one of claims 1 to 8, characterized in that, Based on the total thickness of the current collector, the total thickness of the first metal foil layer accounts for 30%-100%, and can be selected as 30%-85%.

10. The current collector according to any one of claims 1 to 9, characterized in that, The current collector further includes at least one second metal layer, and the current collector satisfies one or more of the following conditions: (1) The second metal layer includes a second element, which includes one or more of Cu, Ag, Au, Ni, Zn, and Cr, and the mass content of the second element in the second metal layer is greater than or equal to 90%; (2) The average grain size of the second metal layer is greater than the average grain size of the first metal foil layer; (3) The average grain size of the second metal layer is greater than or equal to 40 nm; (4) The second metal layer includes copper, and the mass content of copper in the second metal layer is greater than or equal to 90%, and the average grain size of the second metal layer is 90nm-400nm; optionally, it is 100-250nm. (5) Based on the total thickness of the current collector, the total thickness of the second metal layer accounts for 15%-70%; (6) At least a portion of the second metal layer is close to the surface of the current collector.

11. The current collector according to any one of claims 1 to 10, characterized in that, The current collector further includes at least one second metal layer, and the current collector satisfies one or more of the following conditions: (1) The second metal layer includes a second element, which includes one or more of Cu, Ag, Au, Ni, Zn, and Cr. The mass content of the second element in the second metal layer is greater than or equal to 99%, and the average grain size of the second metal layer is 90 nm to 400 nm; optionally, it is 100 to 250 nm. (2) The second metal layer includes copper, and the mass content of Cu in the second metal layer is greater than or equal to 99%, and the average grain size of the second metal layer is 90nm-400nm; optionally, it is 100-250nm.

12. The current collector according to any one of claims 1 to 11, characterized in that, The current collector includes two second metal layers close to the surface of the current collector in the thickness direction and a first metal foil layer disposed between the two second metal layers in the thickness direction.

13. The current collector according to any one of claims 1 to 12, characterized in that, The current collector includes the first metal foil layer, and the current collector satisfies one or more of the following conditions: (1) The current collector comprises a nickel-based alloy, wherein the mass content of nickel in the current collector is 40%-95%; (2) The current collector includes a nickel-iron based alloy, wherein the mass content of nickel and iron in the current collector is greater than that of the other metal elements, the mass content of nickel in the current collector is greater than or equal to 35%, and the mass content of iron in the current collector is 10%-60%; (3) The range of iron content in the current collector is less than or equal to 6%; (4) one or more of the phases Ni, FeNi3, Fe3Ni2, Ni 0.64 Fe 0.36 , Ni1Fe1 in the current collector (5) The thickness range of the current collector is less than or equal to 0.5 μm.

14. The current collector according to any one of claims 1 to 13, characterized in that, The current collector comprises at least one first metal foil layer and at least two second metal layers, and the current collector satisfies one or more of the following conditions: (1) The first metal foil layer includes a nickel-based alloy, and the mass percentage of nickel in the first metal foil layer is 40%-95%; the second metal layer includes copper, and the mass percentage of Cu in the second metal layer is greater than or equal to 90%; the average grain size of the second metal layer is 90nm-400nm, and optionally 100-250nm; (2) The first metal foil layer includes a nickel-iron-based alloy, wherein the mass content of nickel and iron in the first metal foil layer is greater than that of the other metal elements, the mass percentage of nickel in the first metal foil layer is greater than or equal to 35%, and the mass percentage of iron in the first metal foil layer is 10%-60%; the second metal layer includes copper, wherein the mass percentage of Cu in the second metal layer is greater than or equal to 90%; the average grain size of the second metal layer is 90nm-400nm, optionally 100-250nm; (3) Based on the total mass of the current collector, the mass percentage of nickel is 25%-70%, the mass percentage of iron is 1%-40%, and the mass percentage of copper is 15%-65%; (4) The range of iron content in the current collector is less than or equal to 6%; (5) one or more of Ni, FeNi3, Fe3Ni2, Ni 0.64 Fe 0.36 , Ni1Fe1 phase in the first metal foil layer (6) The total thickness of the current collector is 2μm-10μm; (7) The thickness range of the current collector is less than or equal to 0.5 μm.

15. The current collector according to any one of claims 1 to 14, characterized in that, Under test conditions of room temperature and tensile speed of 50±0.5 mm / min, the tensile strength of the current collector is 0.9 GPa-2 GPa, optionally 1.2 GPa-2 GPa, or optionally 1.4 GPa-2 GPa.

16. The current collector according to any one of claims 1 to 15, characterized in that, Fatigue tests were conducted at room temperature and under 1% extended load, and the current collector underwent fatigue cycles greater than or equal to 500.

17. The current collector according to claim 16, characterized in that, Fatigue tests were conducted at room temperature and under 1% extended load, and the fatigue cycle count of the current collector was 2000-4000 cycles.

18. The current collector according to any one of claims 1 to 17, characterized in that, Under test conditions of room temperature and tensile speed of 50±0.5 mm / min, the elongation at break of the current collector is 1%-8%.

19. The current collector according to claim 18, characterized in that, Under test conditions of room temperature and tensile speed of 50±0.5 mm / min, the elongation at break of the current collector is 2%-8%, optionally 3%-6%.

20. The current collector according to any one of claims 1 to 19, characterized in that, Under room temperature testing conditions, the current collector has a bending resistance of 1 to 10 times.

21. A method for preparing a current collector, characterized in that, Includes the following steps: S10. Provide an anode, a first electroplating solution, and a cathode, and perform electroplating to form a first metal foil layer on the surface of the cathode; wherein, the first electroplating solution includes a first metal source, a primary brightener, a secondary brightener, a stress reliever, and a complexing agent; the primary brightener includes one or more of saccharin or sodium saccharin; the secondary brightener includes one or more of alkynyl alcohol compounds or alkynylamine compounds and their salts; the stress reliever contains unsaturated bonds and acid radicals, and the acid radicals include one or more of sulfate or sulfonate; the first metal source includes one or more of Ni, Fe, Cu, and Cr sources. S20. Separate the first metal foil layer from the surface of the cathode to form a first metal foil layer.

22. The method for preparing a current collector according to claim 21, characterized in that, Following S20 are: S30. Electroplating the first metal foil layer with a second electroplating solution to form a second metal layer on at least one side of the first metal foil layer; Optionally, the second electroplating solution includes a second metal source, which includes at least one of Cu, Ag, Au, Ni, Zn, or Cr.

23. The method for preparing a current collector according to claim 21 or 22, characterized in that, The first electroplating solution satisfies one or more of the following characteristics: (1) The concentration of the main brightener in the first electroplating solution is 1.5 g / L-5 g / L; (2) The concentration of the secondary brightener in the first electroplating solution is 0.2 g / L-1 g / L; (3) The total number of carbon and oxygen atoms on the main chain of the alkynol compound is ≥4; optionally, the alkynol compound includes one or more of butynediol, butynediol diethoxy ether or propynediol ethoxy compound; (4) The concentration of stress reliever in the first electroplating solution is 0.1g / L-0.5g / L.

24. The method for preparing a current collector according to any one of claims 21 to 23, characterized in that, The current density of the electroplating process for forming the first metal foil layer is 3 A / dm. 2 -10A / dm 2 .

25. A single battery cell, characterized in that, The device includes an electrode assembly, the electrode assembly including a negative electrode sheet, the negative electrode sheet including a negative current collector, and the negative current collector being the current collector according to any one of claims 1 to 24.

26. The battery cell according to claim 25, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one surface of the negative current collector. The negative electrode film layer includes a negative electrode active material, and the negative electrode active material includes a silicon-based material.

27. The battery cell according to claim 25 or 26, characterized in that, The battery cell includes one or more wound cells.

28. The battery cell according to claim 27, characterized in that, The battery cell satisfies one or more of the following conditions: (1) The thickness of the wound battery cell is 10mm-50mm; (2) The ratio of the length of the straight section to the length of the corner section of the wound cell is 1-10; (3) The single-sided density of the negative electrode sheet is 20 mg / 1540.25 mm. 2 -200mg / 1540.25mm 2 The option is 50mg / 1540.25mm. 2 -200mg / 1540.25mm 2 ; (4) The compaction density of the negative electrode sheet is 0.9 g / cm³. 3 -1.8g / cm 3 1.3g / cm³ is an optional value. 3 -1.8g / cm 3 ; (5) The thickness of the single-sided film layer of the negative electrode sheet is 20μm-150μm, and can be selected as 40μm-80μm; (6) The full discharge margin of the battery cell is 70%-105%.

29. The battery cell according to claim 27 or 28, characterized in that, The battery cell includes a negative electrode sheet, the film layer of the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a silicon-based material, and based on the total mass of the negative electrode film layer, the mass content of silicon element is greater than or equal to 10%, and the thickness of the wound cell is 10mm-50mm.

30. The battery cell according to claim 27 or 28, characterized in that, The battery cell includes a negative electrode sheet; the film layer of the negative electrode sheet includes a negative electrode active material, the negative electrode active material includes a silicon-based material, and based on the total mass of the negative electrode film layer, the mass content of silicon element is greater than or equal to 10%, and the thickness of the wound cell is 10mm-25mm.

31. A single battery cell, characterized in that, The device includes an electrode assembly comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein the solid electrolyte is located between the positive and negative electrode, and the negative electrode includes a negative current collector, wherein the negative current collector is the current collector as described in any one of claims 1 to 9.

32. The battery cell according to claim 31, characterized in that, The solid electrolyte includes sulfides.

33. A battery device, characterized in that, The battery device includes a single battery cell as described in any one of claims 25 to 32, and the battery device includes at least one of a battery module, a battery pack, and an energy storage device.

34. An electrical appliance, characterized in that, Includes the battery cell according to any one of claims 25 to 32 or the battery device according to claim 33.

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