Composite current collector and preparation method therefor, electrode sheet, secondary battery and electric device

Abstract

A composite current collector and a preparation method therefor, an electrode sheet, a secondary battery and an electric device. The composite current collector comprises a current collector substrate and a current collector metal oxide film disposed on at least one side of the current collector substrate. The metal oxide film has a thickness ranging from 0.5 μm to 2 μm. The composite current collector has high sheet resistance, so that the safety performance of batteries can be improved.

Description

Composite current collector and preparation method thereof, pole piece, secondary battery and electrical device

[0001] Cross-references

[0002] This application refers to Chinese patent application No. 202410116158.9 filed on January 26, 2024, entitled "Composite current collector and its preparation method, pole piece, secondary battery and electrical device", which is incorporated into this application in its entirety by reference. Technical Field

[0003] The present application belongs to the field of battery technology, and specifically relates to a composite current collector and a preparation method thereof, a pole piece, a secondary battery, and an electrical device. Background Art

[0004] In recent years, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.

[0005] However, the safety of secondary batteries limits their application and popularity. How to effectively improve the safety performance of secondary batteries is a technical problem that needs to be solved urgently in this field.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a composite current collector that can improve the safety performance of secondary batteries.

[0008] A first aspect of the present application provides a composite current collector, which includes a current collector substrate and a metal oxide film disposed on at least one side of the current collector substrate, wherein the thickness of the metal oxide film is 0.5 μm-2 μm.

[0009] By depositing a metal oxide film of a certain thickness on at least one side of the current collector substrate, the composite current collector's square resistance is effectively controlled within a certain range. This improves the short-circuit resistance in the event of an abnormal battery short circuit, significantly reduces the short-circuit current, reduces the heat released by the short circuit within the battery, and reduces the risk of thermal runaway, greatly improving the battery's safety performance. Compared to current collectors in the prior art, this composite current collector structure has a high tolerance for extreme thickness variations in the metal conductive layer, allowing current collector substrates with poor precision and large square resistance deviations to be used in battery manufacturing. This significantly lowers the entry threshold for current collector substrates suitable for batteries and significantly reduces battery production costs.

[0010] In any embodiment, the thickness of the metal conductive layer may be 0.8 μm to 2 μm, or even greater.

[0011] In any embodiment, the maximum difference in thickness of the metal oxide film is 400 nm or less.

[0012] The metal oxide film provided in the embodiments of the present application has good thickness uniformity, which is beneficial to improving the uniformity and consistency of the composite current collector and improving its electrochemical performance in the battery.

[0013] In any embodiment, the current collector substrate includes a support layer and a metal conductive layer disposed on two opposite surfaces of the support layer.

[0014] In any embodiment, the current collector substrate includes a metal conductive layer and a support layer, the support layer includes an insulating layer, and the metal conductive layers are disposed on two opposite surfaces of the insulating layer.

[0015] In any embodiment, the current collector substrate includes a metal conductive layer and a support layer, the support layer includes a metal layer or an alloy layer, and the metal conductive layers are disposed on two opposite surfaces of the metal layer or the alloy layer.

[0016] When a short circuit occurs under abnormal battery conditions, the insulating layer will melt, blocking current conduction. This significantly reduces the short-circuit current and minimizes the temperature rise, ultimately reducing the risk of battery cell combustion and thermal runaway, and significantly improving battery safety. Furthermore, the insulating layer helps improve the elongation at break of the composite current collector, compensating for the negative impact of the metal oxide film on the composite current collector's processing performance, thereby meeting the battery's requirements for current collector processing performance. The metal conductive layer has conductive properties and is used to provide electrons to the electrode active material layer loaded on the composite current collector, performing both conductive and current collecting functions.

[0017] In any embodiment, the metal conductive layer includes at least one of aluminum, copper, titanium, silver, nickel, aluminum alloy, nickel alloy, titanium alloy, and silver alloy.

[0018] In any embodiment, the metal conductive layer includes a composite material of any one of metals or alloys and a two-dimensional material; the two-dimensional material includes at least one of a graphene material, a graphene-like material or a carbon fiber material.

[0019] In any embodiment, the thickness of the metal conductive layer is 0.8 μm to 2 μm.

[0020] The metal conductive layer has conductive properties and is used to provide electrons for the electrode active material layer loaded on the composite current collector, playing the role of conduction and current collection. In the prior art, the sheet resistance of the current collector is usually increased by controlling the thickness of the metal conductive layer. As the sheet resistance value increases, the metal conductive layer needs to be thinned to a certain extent. The embodiment of the present application adjusts the sheet resistance of the composite current collector through the metal oxide film, so that the composite current collector can tolerate a higher thickness of the metal conductive layer, broadens the formation path of the metal conductive layer, reduces the manufacturing cost of the composite current collector, and effectively achieves a significant reduction in battery cost.

[0021] In any embodiment, the thickness difference of the metal conductive layer is less than or equal to 0.6 μm.

[0022] The composite current collector provided in the embodiment of the present application is different from the current collector in the prior art. It is compatible with metal conductive layers with large thickness deviations, greatly expanding the production methods of metal conductive layers, significantly reducing the manufacturing cost of the composite current collector, and thus reducing battery costs.

[0023] In any embodiment, the insulating layer comprises a polymer.

[0024] In any embodiment, the metal oxide film includes aluminum oxide or copper oxide.

[0025] The aluminum oxide film is non-conductive and has high chemical and thermal stability. It can stably improve the square resistance of the composite current collector during the cycle life of the battery, thereby improving the safety performance of the battery.

[0026] In any embodiment, at room temperature, the sheet resistance of the composite current collector on the metal oxide film side is 25 mΩ / □-35 mΩ / □.

[0027] The composite current collector with the above-mentioned square resistance can increase the short-circuit resistance when a short circuit occurs in an abnormal situation of the battery, significantly reduce the short-circuit current, reduce the heat released due to the short circuit in the battery, reduce the risk of thermal runaway, and greatly improve the safety performance of the battery.

[0028] The second aspect of the present application provides a method for preparing a composite current collector, comprising: providing a current collector substrate, preparing a metal oxide film on at least one side of the current collector substrate by anodization to obtain a composite current collector, wherein the thickness of the metal oxide film is 0.5 μm-2 μm.

[0029] By adopting the anodic oxidation process, the current collector substrate is used as the anode, and a metal oxide film of a certain thickness is generated on its surface through an electrochemical reaction to obtain a composite current collector. The composite current collector has a certain square resistance, so that when a short circuit occurs inside the battery under abnormal conditions, the short-circuit current can be greatly reduced, reducing the heat released by the short circuit, reducing the risk of thermal runaway, and greatly improving the safety performance of the battery. Compared with the current collectors in the prior art, this composite current collector allows current collector substrates with poor precision and large square resistance deviation to be used in battery manufacturing, greatly lowering the entry threshold for current collector substrates that can be used in batteries, and significantly reducing the production cost of batteries. In addition, the oxide film generated by the anodic oxidation method has a high degree of density and good thickness uniformity, which is conducive to improving the uniformity and consistency of the composite current collector.

[0030] In any embodiment, the maximum difference in thickness of the metal oxide film is 400 nm or less.

[0031] In any embodiment, the electrolyte of the anodic oxidation method is an acidic electrolyte, the acidic electrolyte includes at least one of sulfuric acid, hypochlorous acid, and hypochlorite, and the mass percentage concentration of the acidic electrolyte is 10%-40%.

[0032] When the concentration of the acidic electrolyte is within the above range, it is conducive to the formation of a metal oxide film on the surface of the current collector substrate, which can not only improve the preparation efficiency of the metal oxide film, but also prevent the metal oxide film from decomposing too quickly due to excessively high concentration of the acidic electrolyte, thereby achieving stable and efficient preparation of the metal oxide film.

[0033] In any embodiment, the temperature of the electrolyte is 0°C-40°C.

[0034] When the temperature of the electrolyte is within the above range, acid corrosion is not likely to occur, and the electrochemical reaction efficiency of anodization can be improved, thereby achieving stable and efficient preparation of the metal oxide film.

[0035] In any embodiment, the voltage of the anodization process is 5V-25V.

[0036] When the anodic oxidation voltage is within the above range, neither ablation of the current collector substrate surface will occur due to excessively high oxidation voltage, nor will the oxide film be unable to be generated due to excessively low oxidation voltage, thereby achieving stable and efficient deposition of the metal oxide film.

[0037] In any embodiment, the preparation method is a continuous production method.

[0038] The above method improves the preparation efficiency of the composite current collector, which is beneficial to industrial promotion and application.

[0039] In any of the methods, under normal temperature conditions, the sheet resistance of the composite current collector on the metal oxide film side is 25 mΩ / □-35 mΩ / □.

[0040] The composite current collector with a certain square resistance can significantly reduce the short-circuit current when a short circuit occurs inside the battery under abnormal circumstances, reduce the heat released by the short circuit, reduce the risk of thermal runaway, and greatly improve the safety performance of the battery.

[0041] A third aspect of the present application provides a pole piece, which includes a current collector, and the current collector includes the composite current collector of the first aspect or the composite current collector prepared by the preparation method of the second aspect.

[0042] A fourth aspect of the present application provides a secondary battery, comprising the electrode according to the third aspect.

[0043] A fifth aspect of the present application provides an electrical device comprising the secondary battery of the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0045] FIG1 is a schematic diagram of a cross section of a composite current collector according to one embodiment of the present application;

[0046] FIG2 is a schematic diagram of a cross section of a composite current collector according to one embodiment of the present application;

[0047] FIG3 is a scanning electron microscope image of the surface of a composite current collector according to one embodiment of the present application;

[0048] FIG4 (a) is a scanning electron microscope image of a cross section of a composite current collector according to an embodiment of the present application; FIG4 (b) is a scanning electron microscope image of a cross section of a current collector according to the prior art;

[0049] FIG5 is a schematic diagram of an electroplating apparatus according to an embodiment of the present application;

[0050] FIG6 is a schematic diagram of an embodiment of a secondary battery of the present application;

[0051] FIG7 is an exploded schematic diagram of an embodiment of a secondary battery of the present application;

[0052] FIG8 is a schematic diagram of an embodiment of a battery module of the present application;

[0053] FIG9 is a schematic diagram of an embodiment of a battery pack of the present application;

[0054] FIG. 10 is an exploded schematic diagram of the embodiment of the battery pack shown in FIG. 9 .

[0055] FIG. 11 is a schematic diagram of an embodiment of an electric device including the secondary battery of the present application as a power source.

[0056] In the accompanying drawings, which are not necessarily drawn to scale, the reference numerals are as follows: 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 housing, 52 electrode assembly, 53 cover plate, 6 composite current collector, 61 current collector substrate, 62 metal oxide film, 611 metal conductive layer, 612 support layer, 7 electroplating device, 71 conductive roller, 72 external power supply, 73 electrolytic cell, 74 roller, 75 cathode plate, 76 electrolyte, L1 thickness of metal oxide film, L2 thickness of metal conductive layer, L3 thickness of insulating layer. DETAILED DESCRIPTION

[0057] Below, the composite current collector and its preparation method, as well as the embodiments of the electrode, secondary battery and electrical device containing the same are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0058] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0059] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0060] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0061] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further 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 may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0062] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0063] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0064] Unless otherwise specified, the terms used in this application have the common meanings generally understood by those skilled in the art.

[0065] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in this application.

[0066] Unless otherwise specified, in this application, the term "active ions" refers to ions that can be intercalated and extracted between the positive electrode and the negative electrode of a secondary battery, including but not limited to lithium ions.

[0067] In this application, the terms "plurality" and "multiple" refer to two or more.

[0068] Secondary batteries are prone to fire and explosion when subjected to abnormal conditions such as squeezing, collision or puncture, causing serious harm. Research results show that when secondary batteries are subjected to abnormal conditions such as squeezing, collision or puncture, internal short circuits occur in the battery, resulting in intense heat generation, which is the root cause of safety hazards such as battery fire and explosion. In the existing technology, the square resistance of the current collector is often controlled within a certain range to reduce the probability of instantaneous internal short circuits in secondary batteries when safety hazards arise. In order to maintain the square resistance of the current collector within a certain range, it is necessary to strictly control the thickness and precision of the conductive metal in the current collector, which makes the cost of the current collector remain high.

[0069] Based on this, as shown in FIG1 , the present application proposes a composite current collector 6 , which includes a current collector substrate 61 and a metal oxide film 62 disposed on at least one side of the current collector substrate 61 , wherein the thickness L1 of the metal oxide film 62 is 0.5 micrometers (μm) to 2 μm.

[0070] In this article, "metal oxide film" refers to a film layer mainly composed of metal oxide.

[0071] Herein, “current collector substrate” refers to a main component for collecting current during discharge or charge of a secondary battery. In some embodiments, the metal oxide film 62 is disposed on one surface of the current collector substrate 61 .

[0072] In some embodiments, the metal oxide film 62 is disposed on two opposite surfaces of the current collector substrate 61 .

[0073] The thickness of the metal oxide film 62 can be tested by methods known in the art. As an example, as shown in Figure 4a, the composite current collector is polished using argon ion polishing technology to obtain a smooth polished cross-section of the composite current collector, the cross-section of the composite current collector is tested using a scanning electron microscope, and the thickness L1 of the metal oxide film is measured using software.

[0074] In some embodiments, the thickness L1 of the metal oxide film 62 is 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, or any range therebetween. It is generally believed that naturally occurring metal oxide films are less than 0.5 μm.

[0075] In the prior art, it is often believed that depositing a metal oxide film on one side of the current collector substrate is not conducive to the electrochemical performance of the current collector substrate in the battery. The present application overcomes the technical prejudice in the prior art and adopts a method of depositing a metal oxide film 62 of a certain thickness on at least one side of the current collector substrate 61 to effectively control the square resistance of the composite current collector 6 within a certain range, thereby increasing the short-circuit resistance when a short circuit occurs under abnormal conditions of the battery, significantly reducing the short-circuit current, reducing the heat released due to the short circuit in the battery, reducing the risk of thermal runaway, and greatly improving the safety performance of the battery. Compared with the current collectors in the prior art, the composite current collector enables current collector substrates with poor precision and large square resistance deviation to be used in the manufacture of batteries, greatly reducing the entry threshold of current collector substrates that can be used for batteries, and significantly reducing the production cost of the battery.

[0076] In some embodiments, the thickness L1 of the metal oxide film 62 has a maximum difference of less than or equal to 400 nanometers (nm).

[0077] The range of the thickness of the metal oxide film refers to the larger one of the difference between the maximum thickness of the metal oxide film and the average thickness of the metal oxide film and the difference between the average thickness of the metal oxide film and the minimum thickness of the metal oxide film.

[0078] The range of the thickness of the metal oxide film can be measured by any method known in the art. As an example, the composite current collector is polished using argon ion polishing technology to obtain a flat polished cross-section of the composite current collector, the cross-section of the composite current collector is tested using a scanning electron microscope, and the thickness of the metal oxide film is measured using software. At least five different samples are taken, and at least 10 sites are taken from each sample. The average thickness of the metal oxide film is calculated, and the larger of the difference between the maximum thickness of the metal oxide film and the average thickness of the metal oxide film or the difference between the average thickness of the metal oxide film and the minimum thickness of the metal oxide film is used as the range of the thickness of the metal oxide film.

[0079] In some embodiments, the thickness L1 of the metal oxide film may have a range of 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, or any range therebetween.

[0080] The metal oxide film provided in the embodiments of the present application has good thickness uniformity, which is beneficial to improving the uniformity and consistency of the composite current collector and improving its electrochemical performance in the battery.

[0081] In some embodiments, as shown in FIG. 2 , the current collector substrate 61 includes a support layer 612 and a metal conductive layer 611 disposed on two opposite surfaces of the support layer 612 .

[0082] In some embodiments, the metal conductive layer 611 includes at least one of aluminum, copper, titanium, silver, nickel, aluminum alloy, nickel alloy, titanium alloy, and silver alloy.

[0083] In some embodiments, the nickel alloy may be a nickel-iron alloy or a nickel-copper alloy.

[0084] In some embodiments, the metal conductive layer 611 includes a composite material of any one of metals or alloys and a two-dimensional material.

[0085] In some embodiments, the two-dimensional material includes at least one of a graphene material, a graphene-like material, or a carbon fiber material.

[0086] In some embodiments, the composite material may be a physical mixture of different materials in a single layer, or may be a composite structure of multiple layers.

[0087] In this article, “graphene material” refers to the allotrope of carbon, with carbon atoms arranged in sp 2 Hybrid bonding forms a single-layer hexagonal honeycomb lattice graphene.

[0088] In this article, "graphene-like materials" refers to a general term for materials with a two-dimensional single-layer or few-layer structure, including but not limited to layered van der Waals solid materials, layered ionic solid materials, Group IV graphene-like materials, Group IV compounds, and Group III-V compounds. In this article, "carbon fiber materials" refers to high-strength and high-modulus fibers with a carbon content of more than 90%.

[0089] In some embodiments, the metal conductive layer 611 includes at least one of aluminum and an aluminum alloy.

[0090] In some embodiments, the metal conductive layer 611 is prepared by at least one of mechanical rolling, bonding, vapor deposition, and chemical plating, and the vapor deposition method includes at least one of vacuum evaporation, thermal evaporation, electron beam evaporation, and magnetron sputtering.

[0091] In some embodiments, the metal conductive layer 611 is prepared by a mechanical rolling method.

[0092] The metal conductive layer prepared by the mechanical rolling method is often thicker and has a large deviation value, which makes the square resistance of the current collector substrate smaller and the square resistance measured at different positions vary greatly. By providing a metal oxide film on at least one side of the metal conductive layer, the composite current collector has a suitable square resistance, which can significantly improve battery safety while reducing battery manufacturing costs.

[0093] In some embodiments, as shown in FIG. 2 and FIG. 4 a , the thickness L2 of the metal conductive layer 611 is 0.8 μm to 2 μm.

[0094] In some embodiments, the thickness L2 of the metal conductive layer 611 may be 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, or any range therebetween.

[0095] The thickness L2 of the metal conductive layer can be tested by methods known in the art. As an example, the composite current collector is polished using argon ion polishing technology to obtain a smooth polished cross-section of the composite current collector, the cross-section of the composite current collector is tested using a scanning electron microscope, and the thickness of the metal conductive layer is measured using software.

[0096] The metal conductive layer has conductive properties and is used to provide electrons to the electrode active material layer supported on the composite current collector, performing both electrical conduction and current collection functions. In the prior art, the sheet resistance of the current collector is often controlled by limiting the thickness of the metal conductive layer. However, in the embodiments of the present application, the sheet resistance of the composite current collector is adjusted by using a metal oxide film, allowing the composite current collector to have a thicker metal conductive layer. This broadens the formation path of the metal conductive layer, reduces the manufacturing cost of the composite current collector, and effectively achieves a significant reduction in battery costs.

[0097] In some embodiments, the thickness L2 of the metal conductive layer 611 has a maximum difference of less than or equal to 0.6 μm.

[0098] The extreme difference in thickness of the metal conductive layer refers to the larger one of the difference between the maximum thickness of the metal conductive layer and the average thickness of the metal conductive layer and the difference between the average thickness of the metal conductive layer and the minimum thickness of the metal conductive layer.

[0099] In some embodiments, the thickness L2 of the metal conductive layer 611 may have a range of 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, or any range therebetween.

[0100] The range of the thickness L2 of the metal conductive layer can be measured by any method known in the art. As an example, the composite current collector is polished using argon ion polishing technology to obtain a flat polished cross-section of the composite current collector, the cross-section of the composite current collector is tested using a scanning electron microscope, and the thickness of the metal conductive layer is measured using software. At least five different samples are taken, and at least 10 sites are taken from each sample. The average thickness of the metal conductive layer is calculated, and the larger of the difference between the maximum thickness of the metal conductive layer and the average thickness of the metal conductive layer or the difference between the average thickness of the metal conductive layer and the minimum thickness of the metal conductive layer is used as the range of the thickness of the metal conductive layer.

[0101] Figure 4(b) shows a current collector in the prior art, which only includes a support layer 612 and a metal conductive layer 611 disposed on both surfaces of the support layer 612. A comparison of Figures 4(a) and 4(b) shows that the composite current collector provided in the embodiments of the present application is different from the composite current collector in the prior art. By providing a metal oxide film to adjust the overall sheet resistance, it is compatible with metal conductive layers 611 with large thickness deviations, greatly expanding the production methods of the metal conductive layer 611, significantly reducing the manufacturing cost of the composite current collector, and thus reducing battery costs.

[0102] In some embodiments, the support layer 612 is an insulating layer.

[0103] In some embodiments, the support layer 612 is a metal layer or an alloy layer.

[0104] In some embodiments, the thickness L3 of the insulating layer is 4 μm to 8 μm.

[0105] In some embodiments, the thickness L3 of the insulating layer may be 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, or any range therebetween.

[0106] In some embodiments, the insulating layer includes a middle layer and adhesive layers disposed on both sides of the middle layer.

[0107] The adhesive layer facilitates the bonding and mechanical bonding of the conductive layer and the intermediate layer, thereby further reducing production costs.

[0108] In some embodiments, the insulating layer comprises a polymer.

[0109] In some embodiments, the polymer includes at least one of polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and polycarbonate.

[0110] In some embodiments, the insulating layer further includes an inorganic filler.

[0111] In some embodiments, the inorganic filler includes at least one of alumina, silicon carbide, silicon dioxide, and glass fiber.

[0112] When a battery short-circuit occurs under abnormal conditions, the insulating layer melts, preventing further current conduction. This significantly reduces the short-circuit current, lowering the heat released and the temperature rise during abnormal conditions. This ultimately reduces the risk of cell combustion and thermal runaway, significantly improving battery safety. Furthermore, the insulating layer improves the elongation at break of the composite current collector, compensating for the negative impact of the metal oxide film on the composite current collector's processing performance, ultimately meeting the battery's requirements for current collector processing performance.

[0113] In some embodiments, the metal oxide film 62 includes aluminum oxide or copper oxide.

[0114] In some embodiments, metal oxide film 62 includes aluminum oxide.

[0115] The surface of the metal oxide film can be tested using a scanning electron microscope, as shown in Figure 3. The aluminum oxide film is non-conductive and has high density, chemical stability, and thermal stability. It can steadily increase the square resistance of the composite current collector during the battery's cycle life, thereby improving the battery's safety performance.

[0116] In some embodiments, as shown in FIG. 1 , at room temperature, the sheet resistance of the composite current collector 6 on the side of the metal oxide film 62 is 25 milliohms per square (mΩ / □) to 35 mΩ / □.

[0117] In this document, "normal temperature" refers to 20±10 degrees Celsius (°C).

[0118] In this article, "sheet resistance" refers to the voltage drop caused by the current density per unit area (i.e. the amount of current per unit area) in the thickness direction of the material at a certain temperature.

[0119] For conventional three-dimensional conductors, the resistance calculation formula is:

[0120] Where ρ represents resistivity, A represents cross-sectional area, and L represents length. The cross-sectional area can be decomposed into width W and film thickness t, so the resistance can be written as:

[0121] Where Rs is the square resistance. When the diaphragm is square, L=W, the measured resistance R is the square resistance R S , and R S Regardless of the size of L or W, R S is the resistance of the unit square, so R S The unit can be expressed as ohm per square (Ω / □).

[0122] The square resistance of the composite current collector on the metal oxide film side can be tested by methods known in the art. As an example, a four-terminal probe test instrument is used under room temperature conditions, and four smooth copper probes A, B, C, and D with a diameter of 2.0 mm are pressed parallel to the metal oxide film of the composite current collector in sequence along the length direction of the composite current collector. Wires are welded on the copper rods and connected to the milliohmmeter so that the distance L between the copper rods B and C is equal to the width W of the composite current collector. The distance between the copper rods A and B, and the distance between the copper rods C and D is not specifically limited and can be selected from 10 mm to 20 mm. After the milliohmmeter is connected, the resistance value displayed by the milliohmmeter is the square resistance value of the composite current collector on the metal oxide film side.

[0123] In some embodiments, at room temperature, the square resistance of the composite current collector on one side of the metal oxide film is 25mΩ / □, 26mΩ / □, 27mΩ / □, 28mΩ / □, 29mΩ / □, 30mΩ / □, 31mΩ / □, 32mΩ / □, 33mΩ / □, 34mΩ / □, 35mΩ / □ or any numerical range therebetween.

[0124] The composite current collector with the above-mentioned square resistance can increase the short-circuit resistance when a short circuit occurs in an abnormal situation of the battery, significantly reduce the short-circuit current, reduce the heat released due to the short circuit in the battery, reduce the risk of thermal runaway, and greatly improve the safety performance of the battery.

[0125] In some embodiments, the composite current collector has an elongation at break of 15% to 30%.

[0126] In this article, the term "elongation at break" refers to the ratio of the change in length of a material when it undergoes plastic deformation until it breaks after being subjected to stress to its original length. It is usually expressed as a percentage and is an important parameter for measuring the material's ability to withstand stress during stretching.

[0127] In the present application, the elongation at break of the composite current collector can be tested by methods known in the art. As an example, referring to the GB / T 5230-1995 standard, at least 4 samples with a length of 200±0.5 mm and a width of 15±0.25 mm are cut, and the samples are continuously loaded at a tensile speed of 50 mm / min at room temperature until they break. The maximum load divided by the cross-sectional area of ​​the sample is used as the tensile strength of the sample.

[0128] In some embodiments, the elongation at break of the composite current collector may be 15%, 20%, 25%, 30%, or any range therebetween.

[0129] When the elongation at break of the composite current collector is within the above range, the composite current collector also has good plasticity, which can reduce the probability of brittle fracture of the electrode and further improve the safety of the battery.

[0130] The second aspect of the present application provides a method for preparing a composite current collector, comprising: providing a current collector substrate, preparing a metal oxide film on at least one side of the current collector substrate by an anodic oxidation method, and obtaining a composite current collector, wherein the thickness of the metal oxide film is 0.5 μm-2 μm.

[0131] In this article, the term "anodization method" refers to the process of forming a metal oxide film on the surface of metals and their alloys in an electrolyte and specific process conditions under the action of an external current.

[0132] By adopting the anodic oxidation process, the current collector substrate is used as the anode, and a metal oxide film of a certain thickness is generated on its surface through an electrochemical reaction to obtain a composite current collector. The composite current collector has a certain square resistance, so that when a short circuit occurs inside the battery under abnormal conditions, the short-circuit current can be greatly reduced, reducing the heat released by the short circuit, reducing the risk of thermal runaway, and greatly improving the safety performance of the battery. Compared with the current collectors in the prior art, this composite current collector allows current collector substrates with poor precision and large square resistance deviation to be used in battery manufacturing, greatly lowering the entry threshold for current collector substrates that can be used in batteries, and significantly reducing the production cost of batteries. In addition, the oxide film generated by the anodic oxidation method has a high degree of density and good thickness uniformity, which is conducive to improving the uniformity and consistency of the composite current collector.

[0133] In any embodiment, the metal oxide film has a thickness range of 400 nm or less.

[0134] In some embodiments, at room temperature, the sheet resistance of the composite current collector on the side of the metal oxide film is 25 mΩ / □-35 mΩ / □.

[0135] In some embodiments, the electrolyte of the anodization method is an acidic electrolyte, and the acidic electrolyte includes at least one of sulfuric acid, hypochlorous acid, and hypochlorite, and the mass percentage concentration of the acidic electrolyte is 10%-40%.

[0136] In some embodiments, the acidic electrolyte includes sulfuric acid.

[0137] In some embodiments, the mass percentage concentration of the acidic electrolyte is 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any range therebetween.

[0138] Mass percentage concentration refers to the ratio of the mass of the solute contained in the solution to the mass of the solution. Acidic electrolyte concentrations within the above ranges are beneficial for the formation of a metal oxide film on the surface of the current collector substrate, improving the efficiency of metal oxide film preparation while preventing the rapid decomposition of the metal oxide film caused by excessively high acidic electrolyte concentrations, thereby achieving stable and efficient metal oxide film preparation.

[0139] In some embodiments, the temperature of the electrolyte is 0°C-40°C.

[0140] In some embodiments, the temperature of the electrolyte is 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, or any range therebetween.

[0141] When the temperature of the electrolyte is within the above range, acid corrosion is not likely to occur, and the electrochemical reaction efficiency of anodization can be improved, thereby achieving stable and efficient preparation of the metal oxide film.

[0142] In some embodiments, the voltage of the anodization method is 5V to 25V.

[0143] In some embodiments, the voltage of the anodization method is 5 V, 9 V, 13 V, 17 V, 21 V, 25 V, or any range therebetween.

[0144] When the voltage of the anodic oxidation method is within the above range, neither ablation of the current collector substrate surface will occur due to excessively high oxidation voltage, nor will the oxide film be unable to be generated due to excessively low oxidation voltage, thereby achieving stable and efficient deposition of the metal oxide film.

[0145] In some embodiments, the preparation method is a continuous production method.

[0146] In some embodiments, the continuous production method uses a continuous belt conveyor to enable continuous anodization of the current collector substrate. The above method improves the preparation efficiency of the composite current collector, facilitating industrial promotion and application.

[0147] In some embodiments, the continuous production method utilizes a continuous electroplating apparatus. In some embodiments, the electroplating apparatus 7 is shown in FIG5 and includes a conductive roller 71, an external power source 72, an electrolytic cell 73, a roller 74, a cathode plate 75, and an electrolyte 76 contained in the electrolytic cell. The cathode plate 75 is immersed in the electrolyte 76 opposite the surface of the current collector substrate 61.

[0148] In some embodiments, the conductive rollers 71 are respectively disposed on two opposite surfaces of the current collector substrate 61 , so that both surfaces of the current collector substrate 61 can be positively charged.

[0149] In some embodiments, the continuous production method includes: connecting the conductive roller 71 of the electroplating device 7 to the positive electrode of the external power supply 72, and connecting the cathode plate 75 to the negative electrode of the external power supply 72; the current collector substrate 61 is transferred to the electrolytic tank 73 containing the electrolyte 76 via the conductive roller 71 for anodization and then moved out of the electrolytic tank 73 via the roller 74.

[0150] In some embodiments, the cathode plate is at least one of a copper plate and a lead plate.

[0151] In some embodiments, the conductive roller is a metal roller, and may be a stainless steel roller.

[0152] In some embodiments, the electroplating apparatus includes at least two cathode plates, and the at least two cathode plates are disposed opposite to each other on two opposite surfaces of the current collector substrate.

[0153] This arrangement enables the upper and lower surfaces of the current collector substrate to be simultaneously anodic-oxidized to form a metal oxide film when the current collector substrate is conveyed in the electrolytic cell, thereby improving production efficiency.

[0154] Pole

[0155] A third aspect of the embodiments of the present application provides a pole piece, which includes a current collector. The current collector includes a composite current collector according to any embodiment or a composite current collector prepared by a preparation method according to any embodiment.

[0156] In some embodiments, the electrode is a positive electrode, and the current collector is a composite current collector.

[0157] In some embodiments, the positive electrode sheet includes a composite current collector and a positive electrode film layer disposed on at least one surface of the composite current collector. For example, the composite current collector has two surfaces that are opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the composite current collector.

[0158] The positive electrode film layer generally comprises a positive electrode active material, an optional binder and an optional conductive agent. The positive electrode film layer is generally formed by coating a positive electrode slurry on a metal oxide film of a composite current collector, drying, and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring evenly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto. As an example, the binder for the positive electrode film layer may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. As an example, the conductive agent for the positive electrode film layer includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0159] The positive electrode active material may be a positive electrode active material for a secondary battery known in the art.

[0160] When the secondary battery of the present application is a lithium-ion battery, the positive electrode active material may include, but is not limited to, one or more of lithium-containing transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of the lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of the lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds.

[0161] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material for the lithium-ion battery may include a lithium transition metal oxide having a general formula of Li a Ni b Co c M d O e A f and its modified compounds. 0.8 ≤ a ≤ 1.2, 0.5 ≤ b < 1, 0 < c < 1, 0 < d < 1, 1 ≤ e ≤ 2, 0 ≤ f ≤ 1, M is selected from one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, and B, and A is selected from one or more of N, F, S, and Cl.

[0162] In some embodiments, by way of example, the positive electrode active material for the lithium-ion battery may include one or more of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811), LiNi 0.85 Co 0.15 Al 0.05 O2, LiFePO4, and LiMnPO4.

[0163] In the present application, the modified compounds of the above-mentioned positive electrode active materials may be the ones subjected to doping modification and / or surface coating modification on the positive electrode active materials.

[0164] In some embodiments, the electrode is a negative electrode, and the current collector is a composite current collector.

[0165] In some embodiments, the negative electrode plate includes a composite current collector and a negative electrode film layer disposed on at least one surface of the composite current collector. For example, the composite current collector has two surfaces that are opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposing surfaces of the composite current collector.

[0166] In some embodiments, the negative electrode film layer includes a negative electrode active material. In some embodiments, the other negative electrode active materials include, but are not limited to, one or more of conventional natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials may include one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloy materials. The tin-based materials may include one or more of elemental tin, tin oxide, and tin alloy materials.

[0167] In some embodiments, the negative electrode film layer may further optionally include a negative electrode conductive agent. The present application does not particularly limit the type of the negative electrode conductive agent. As examples, 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.

[0168] In some embodiments, the negative electrode film layer may further optionally include a negative electrode binder. The present application does not particularly limit the type of the negative electrode binder. As examples, the negative electrode binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0169] In some embodiments, the negative electrode film layer may further include other additives. For example, the other additives may include a thickener, such as sodium carboxymethyl cellulose (CMC), a PTC thermistor material, and the like.

[0170] The negative electrode film layer is typically formed by coating a negative electrode slurry onto the metal oxide film of a composite current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing the negative electrode active material, an optional conductive agent, an optional binder, and other optional additives in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0171] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate described in the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the composite current collector and the negative electrode film layer and disposed on the surface of the composite current collector; in some embodiments, the negative electrode plate described in the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0172] secondary batteries

[0173] A fourth aspect of the embodiments of the present application provides a secondary battery.

[0174] The present application has no particular restrictions on the type of secondary battery. For example, the secondary battery can be a lithium-ion battery, etc. In general, a secondary battery includes a positive electrode plate, a negative electrode plate, and an electrolyte, etc. During the charge and discharge process of the secondary battery, active ions are embedded and released back and forth between the positive electrode plate and the negative electrode plate, and the electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The present application has no particular restrictions on the type of the electrolyte, and it can be selected according to actual needs. For example, the electrolyte can be selected from at least one of a solid electrolyte and a liquid electrolyte (i.e., an electrolyte). Secondary batteries using electrolytes and some secondary batteries using solid electrolytes can also include an isolation membrane, which is arranged between the positive electrode plate and the negative electrode plate to play an isolation role.

[0175] [Electrolytes]

[0176] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0177] The type of the electrolyte salt is not particularly limited and can be selected according to actual needs.

[0178] When the secondary battery of the present 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 bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0179] The type of the solvent is not specifically limited and can be selected according to actual needs. In some embodiments, for example, the solvent may include 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), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE). One or more.

[0180] In some embodiments, the electrolyte may further optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives capable of improving certain properties of the secondary battery, such as additives that improve the overcharge performance of the secondary battery, additives that improve the high-temperature performance of the secondary battery, and additives that improve the low-temperature power performance of the secondary battery.

[0181] [Isolation film]

[0182] The present application has no particular limitation on the type of the isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0183] In some embodiments, the material of the isolation membrane may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0184] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process.

[0185] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0186] In some embodiments, the outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0187] The present application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square, or any other shape. FIG6 shows a secondary battery 5 with a square structure as an example.

[0188] In some embodiments, as shown in FIG7 , the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation film can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be adjusted according to demand.

[0189] The preparation method of the secondary battery of the present application is well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a secondary battery. As an example, the positive electrode sheet, separator, and negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. The secondary battery is then vacuum packaged, allowed to stand, formed, and shaped.

[0190] In some embodiments of the present application, the secondary batteries according to the present application can be assembled into a battery module. The battery module can contain multiple secondary batteries, and the specific number can be adjusted according to the application and capacity of the battery module.

[0191] Figure 8 is a schematic diagram of an exemplary battery module 4. As shown in Figure 8 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0192] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0193] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0194] Figures 9 and 10 are schematic diagrams of an exemplary battery pack 1. As shown in Figures 9 and 10, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 covers the lower case 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the battery box.

[0195] Electrical devices

[0196] The present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack of the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0197] The electrical device may select a secondary battery, a battery module or a battery pack according to its usage requirements.

[0198] Figure 11 is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module may be used.

[0199] As another example, the electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a secondary battery as a power source.

[0200] Example

[0201] The following examples describe the present disclosure in more detail. These examples are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are by mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing. The instruments used in the examples are commercially available.

[0202] Example 1

[0203] (1) Preparation of composite current collector

[0204] The structure of the current collector substrate is aluminum foil / polyvinyl fluoride / polypropylene / polyvinyl fluoride / aluminum foil, with polyvinyl fluoride / polypropylene / polyvinyl fluoride as the insulating layer. The aluminum foil is deposited by mechanical calendering, and its single layer thickness is 1±0.2μm. The thickness of the insulating layer is 8μm. The current collector substrate enters the electrolytic cell, passes through the conductive roller, and then enters the tank with electrolyte. The electrolyte in the tank includes H2SO4, the electrolyte concentration is 15%, and the electrolyte temperature is 28°C.

[0205] The electrolytic cell was connected to an external power supply, with the positive power supply connected to a steel conductive roller. After the current collector substrate passed through the conductive rollers, which were positioned on opposite surfaces of the current collector, both opposing surfaces of the current collector substrate became positively charged. The negative power supply was connected to a negatively charged copper cathode plate within the electrolytic cell, measuring 0.6 m x 2 m. This formed a current loop within the entire electrolytic cell. The electrolyte level was higher than the cathode plate, and the entire cathode plate was immersed in the electrolyte. The current collector substrate passed between the upper and lower cathode plates within the electrolytic cell, with the surfaces of the upper and lower cathode plates and the current collector substrate being substantially parallel. The current collector substrate was moved within the electrolytic cell, achieving simultaneous anodization of both its upper and lower surfaces. The moving speed was 4 m / min, and the anodization time was 3.0 min. A metal oxide film was deposited on the current collector substrate, resulting in a composite current collector. The thickness of the metal oxide film was 1.10 ± 0.38 μm, and the elongation at break of the composite current collector was 18%.

[0206] (2) Preparation of batteries

[0207] The positive electrode active material NCM811, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are mixed evenly in an N-methylpyrrolidone (NMP) solution in a mass ratio of 97%:1%:2% to prepare a positive electrode slurry. Then, the slurry is applied to the surface of the composite current collector using an extrusion coater and dried. The coated electrode is then cold-pressed using a cold press to prepare the final positive electrode electrode.

[0208] The negative electrode active material artificial graphite, carbon nanotubes, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are fully stirred and mixed in deionized water at a mass ratio of 97.1%:0.9%:1.1%:0.9% to form a uniform negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and the negative electrode film layer is obtained after drying and other processes.

[0209] Polyethylene film (PE film) is used as the separator.

[0210] Ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0211] The positive electrode sheet, separator, and negative electrode sheet are wound or stacked in sequence to obtain a bare cell. The bare cell is placed in a packaging shell, dried, and then injected with electrolyte. After vacuum packaging, standing, forming, shaping, and other processes, a lithium-ion battery is obtained.

[0212] Examples 2-4

[0213] The anodic oxidation parameters were adjusted, as shown in Table 1. The battery was prepared in the same manner as in Example 1.

[0214] Comparative Example 1

[0215] A secondary battery was prepared using the current collector substrate before anodization in Example 1 as the positive electrode current collector.

[0216] Performance Testing

[0217] (1) Square resistance test

[0218] At 25°C, a four-terminal probe test instrument is used, and four smooth round copper rod probes A, B, C, and D are pressed parallel to the metal oxide film of the composite current collector along the length direction of the composite current collector. The probe diameter is 2.00 mm. Wires are welded on the copper rods and connected to the milliohmmeter. The distance L between copper rods B and copper rods C is equal to the width W of the composite current collector. There is no specific limit on the distance between copper rods A and copper rods B, and copper rods C and copper rods D, and can be selected from 10 mm to 20 mm. After the milliohmmeter is connected, the resistance value displayed by the milliohmmeter is the square resistance value of the composite current collector on the metal oxide film side.

[0219] (2) Thickness test

[0220] The composite current collector obtained after anodization is sampled, and a smooth polished cross section is obtained by cross-section polishing technology. The cross section of the composite current collector is tested using a scanning electron microscope to measure the thickness of the metal oxide film.

[0221] (3) Acupuncture experiment

[0222] After fully charging the battery, use a φ1mm high-temperature resistant steel needle to penetrate the battery electrode at a speed of 0.1mm / s to a depth of 4mm from a direction perpendicular to the battery electrode. The penetration position should be close to the geometric center of the punctured surface. The steel needle stays in the battery and is left to stand for 1 hour before observing the battery fire situation.

[0223] Test results

[0224] The test results of the embodiments and comparative examples are shown in Table 1.

[0225] Table 1

[0226] Comparison of the Examples and Comparative Examples shows that the composite current collector provided in the Examples of the present application includes a current collector substrate and a metal oxide film disposed on at least one side of the current collector substrate. The thickness of the metal oxide film is 0.5 μm to 2 μm. At room temperature, the composite current collector has a sheet resistance of 25 mΩ / □ to 35 mΩ / □. This composite current collector has a high sheet resistance and does not ignite after a one-hour needle penetration test, thus helping to improve battery safety.

[0227] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A composite current collector, characterized in that, The composite current collector includes a current collector substrate and a metal oxide film provided on at least one side of the current collector substrate, and the thickness of the metal oxide film is 0.5 μm - 2 μm.

2. The composite current collector according to claim 1, wherein The range of the thickness of the metal oxide film is less than or equal to 400 nm.

3. The composite current collector according to claim 1 or 2, wherein The current collector substrate includes a support layer and metal conductive layers provided on two opposite surfaces of the support layer; the current collector substrate includes one or more of the following features: (1) The support layer is an insulating layer, and the metal conductive layers are provided on two opposite surfaces of the insulating layer; (2) The support layer is a metal layer or an alloy layer, and the metal conductive layers are provided on two opposite surfaces of the metal layer or the alloy layer.

4. The composite current collector according to claim 3, wherein The metal conductive layer includes one or more of the following features: (1) The metal conductive layer includes at least one of aluminum, copper, titanium, silver, nickel, aluminum alloy, nickel alloy, titanium alloy, and silver alloy; (2) The metal conductive layer includes a composite material of any one of a metal or an alloy and a two-dimensional material; the two-dimensional material includes at least one of a graphene material, a graphene-like material, and a carbon fiber material.

5. The composite current collector according to claim 3 or 4, wherein the thickness of the metal conductive layer is 0.8 μm - 2 μm.

6. The composite current collector according to any one of claims 3 to 5, wherein the range of the thickness of the metal conductive layer is less than or equal to 0.6 μm.

7. The composite current collector according to any one of claims 3 to 6, wherein the insulating layer includes a polymer.

8. The composite current collector according to any one of claims 1 to 7, wherein the metal oxide film includes aluminum oxide or copper oxide.

9. The composite current collector according to any one of claims 1 to 8, characterized in that, Under normal temperature conditions, the sheet resistance of the composite current collector on the side of the metal oxide film is 25 mΩ / □ - 35 mΩ / □.

10. A preparation method of a composite current collector, characterized in that, including: providing a current collector substrate, preparing a metal oxide film on at least one side of the current collector substrate by an anodic oxidation method to obtain a composite current collector, and the thickness of the metal oxide film is 0.5 μm - 2 μm.

11. The preparation method according to claim 10, characterized in that, The range of the thickness of the metal oxide film is less than or equal to 400 nm.

12. The preparation method according to claim 11, wherein, The electrolyte for the anodic oxidation method is an acidic electrolyte, and the acidic electrolyte includes at least one of sulfuric acid, hypochlorous acid, and hypochlorite, and the mass percentage concentration of the acidic electrolyte is 10% - 40%.

13. The preparation method according to claim 12, wherein, The temperature of the electrolyte is 0°C - 40°C.

14. The preparation method according to any one of claims 10 to 13, characterized in that, The voltage of the anodic oxidation method is 5V - 25V.

15. The preparation method according to any one of claims 10 to 14, characterized in that, The preparation method is a continuous production method.

16. The preparation method according to any one of claims 10 to 15, characterized in that, Under normal temperature conditions, the sheet resistance of the composite current collector on the side of the metal oxide film is 25 mΩ / □ - 35 mΩ / □.

17. A pole piece, characterized in that, The electrode plate includes a current collector, and the current collector includes the composite current collector according to any one of claims 1 to 9 or the composite current collector prepared by the preparation method according to any one of claims 10 to 16.

18. A secondary battery, characterized in that, including the electrode plate according to claim 17.

19. An electrical device, characterized in that, including the secondary battery according to claim 18.

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