Negative electrode and battery

Abstract

This application relates to the field of battery technology, specifically to a negative electrode and a battery. The negative electrode includes: a current collector comprising a first metal layer and a second metal layer disposed on at least one surface of the first metal layer along its thickness direction; the second metal layer having a porous structure; a first active layer disposed on the surface of the second metal layer away from the first metal layer; and a second active layer disposed on the surface of the first active layer away from the second metal layer. The first and second metal layers are both metallic materials, resulting in a tighter bond. Furthermore, since the second metal layer itself is metallic, it can effectively conduct current, reducing the internal resistance of the battery and improving the overall efficiency of the battery. In addition, the second metal layer also has a porous structure, which increases the contact area between the current collector and the active material while improving the adhesion stability between the active material and the current collector.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a negative electrode and a battery. Background Technology

[0002] Lithium-ion batteries are widely used in electronic devices, new energy vehicles, and energy storage due to their environmental friendliness, high operating voltage, large specific capacity, and long cycle life. However, the short driving range of new energy vehicles has always been a limiting factor for the industry's development. Existing technologies typically use thicker electrodes to increase the active material loading of the electrodes, thereby improving battery energy density and fast-charging performance. While thicker electrodes have their advantages, they also introduce some problems. For example, battery polarization is more pronounced. Due to the increased electrode thickness, the diffusion paths of lithium ions and electrons become longer, further exacerbating the non-uniformity of internal and external polarization along the electrode thickness direction.

[0003] Double-layer coating technology, by optimizing the formulation of the upper and lower slurries, can solve problems such as poor rate performance and insufficient adhesion caused by thick electrodes. However, because the surface of the foil is very smooth, it is not easy to form a mutually cross-bonding contact surface with the active material. This leads to poor adhesion between the current collector and the material, loose interface bonding, poor conductivity, and the electrode failing to continue discharging.

[0004] Therefore, it is necessary to provide a negative electrode sheet that can effectively solve the problem of poor adhesion between the active material and the current collector. Utility Model Content

[0005] In view of this, this application aims to at least partially solve one of the technical problems in the related art. To this end, this application provides a negative electrode sheet and a battery that can effectively solve the problem of poor adhesion between the active material and the current collector, thereby improving the battery's energy density, fast charging performance, and the conductivity, uniformity, and adhesion stability of the negative electrode sheet.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] According to one aspect of this application, an embodiment of this application provides a negative electrode sheet, the negative electrode sheet comprising:

[0008] A current collector, the current collector comprising a first metal layer and a second metal layer disposed on at least one surface of the first metal layer along its thickness direction; the second metal layer having a porous structure;

[0009] A first active layer is disposed on the surface of the second metal layer on the side away from the first metal layer;

[0010] The second active layer is disposed on the surface of the first active layer away from the second metal layer.

[0011] In one alternative implementation, the first metal layer and the second metal layer are joined by welding.

[0012] In one alternative implementation, the first metal layer comprises a metal foil.

[0013] In one alternative implementation, the second metal layer comprises foamed metal.

[0014] In one alternative implementation, the second metal layer and the first active layer are joined by hot rolling.

[0015] In one alternative implementation, the first active layer is a dry-formed film.

[0016] In one alternative implementation, the second active layer is a wet-formed film.

[0017] In one alternative implementation, the thickness of the first metal layer is 4.5 μm to 20 μm.

[0018] In one alternative implementation, the thickness of the second metal layer is 20 μm to 80 μm.

[0019] In one alternative embodiment, the porosity of the second metal layer is 90% to 97%.

[0020] In one alternative embodiment, the aperture of the second metal layer is 0.6 mm to 1.2 mm.

[0021] In one optional implementation, the specific surface area of ​​the second metal layer is 270 cm². 2 / cm 3 ~600cm 2 / cm 3 .

[0022] In one optional implementation, the thickness of the first active layer is 100 μm to 300 μm.

[0023] In one optional implementation, the areal density of the first active layer is 0.05 g / cm³. 2 ~0.3g / cm 2 .

[0024] In one optional implementation, the thickness of the second active layer is 100 μm to 300 μm.

[0025] In one optional embodiment, the areal density of the second active layer is 0.05 g / cm³. 2 ~0.3g / cm 2 .

[0026] In one alternative implementation, the metal in the first metal layer includes copper and / or nickel.

[0027] In one alternative implementation, the metal in the second metal layer includes copper and / or nickel.

[0028] According to a second aspect of this application, an embodiment of this application provides a battery including a negative electrode sheet, the negative electrode sheet including the aforementioned negative electrode sheet.

[0029] The technical solution of this application has at least the following beneficial effects:

[0030] The negative electrode sheet provided in this embodiment features a specially designed current collector with a second metal layer disposed along the thickness direction of the first metal layer. Both the first and second metal layers are metallic materials, resulting in a tighter bond. Since the second metal layer is itself metallic, it effectively conducts current, reduces internal battery resistance, and improves overall battery efficiency. Furthermore, the second metal layer has a porous structure, which increases the contact area between the current collector and the active material while also improving the adhesion stability between the active material and the current collector.

[0031] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0032] Figure 1 The diagram shown is a schematic diagram of a negative electrode structure provided in an embodiment of this application.

[0033] 1-First metal layer;

[0034] 2-Second metal layer;

[0035] 3-First active layer;

[0036] 4-Second active layer. Detailed Implementation

[0037] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0038] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0039] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0040] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0041] 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.

[0042] Currently, to achieve higher active material loading in negative electrodes, the electrode thickness is typically large. While thick electrodes prepared using double-layer coating technology can solve the problem of poor rate performance associated with thick electrodes, they still suffer from insufficient adhesion between the current collector and the active material.

[0043] To address the aforementioned problems, embodiments of this application provide a negative electrode sheet. For example... Figure 1 As shown, some embodiments of this application provide a negative electrode sheet, which includes:

[0044] The current collector includes a first metal layer 1 and a second metal layer 2 disposed on at least one surface of the first metal layer 1 along the thickness direction; the second metal layer 2 has a porous structure.

[0045] The first active layer 3 is disposed on the surface of the second metal layer 2 away from the first metal layer 1;

[0046] The second active layer 4 is disposed on the surface of the first active layer 3 away from the second metal layer 2.

[0047] refer to Figure 1 The current collector includes a first metal layer 1 and a second metal layer 2 disposed on at least one surface of the first metal layer 1 along its thickness direction; the second metal layer 2 has a porous structure. The lengths of the first metal layer 1 and the second metal layer 2 may be the same or different, and those skilled in the art can adjust them according to this application and actual needs; no specific limitation is made in this embodiment.

[0048] Therefore, the embodiments of this application mainly achieve this by specially designing the structure of the negative electrode current collector, with a second metal layer 2 disposed along the thickness direction of the first metal layer 1. Both the first metal layer 1 and the second metal layer 2 are made of metallic materials, resulting in a tighter connection. Since the second metal layer 2 itself is a metallic material, it can effectively conduct current, reduce the internal resistance of the battery, and improve the overall efficiency of the battery. Furthermore, the second metal layer 2 also has a porous structure, which increases the contact area between the current collector and the active material while also improving the adhesion stability between the active material and the current collector.

[0049] In some embodiments of this application, the first metal layer 1 and the second metal layer 2 are connected by welding. As an example, the first metal layer 1 and the second metal layer 2 can be connected by brazing.

[0050] The term "brazing" is a joining method performed at lower temperatures, using a filler metal (brazing filler metal) with a melting point lower than that of the materials being joined, which enables a connection without damaging the porous metal layer.

[0051] In some embodiments of this application, the first metal layer 1 includes a metal foil. As an example, the first metal layer 1 may be a copper foil.

[0052] In some embodiments of this application, the second metal layer 2 comprises foamed metal. As an example, the second metal layer 2 may be foamed copper.

[0053] In some embodiments of this application, the second metal layer 2 and the first active layer 3 are joined by hot rolling.

[0054] In some embodiments of this application, the first active layer 3 is a dry-formed film. If the first active layer 3 is a wet-formed film, the active material will fall into the second metal layer 2 during the wet coating process, and the active material will be permanently deactivated after drying and rolling.

[0055] In this application, the first active layer 3 is a dry-formed film and is connected to the second metal layer 2 by hot rolling. Hot rolling not only enhances the adhesion stability between the first active layer 3 and the second metal layer 2, but also promotes the spatial three-dimensional connection of the pore structures of the first active layer 3 and the second metal layer 2, thereby improving conductivity and overall stability. Therefore, it solves the problems of loose bonding and easy detachment between traditional dry-formed films and metal foil current collectors.

[0056] In some embodiments of this application, the second active layer 4 is a wet-formed film.

[0057] In some embodiments of this application, the thickness of the first metal layer 1 is 4.5 μm to 20 μm. As an example, the thickness of the first metal layer 1 can be any one of 4.5 μm, 8 μm, 12 μm, 16 μm, 20 μm, or a range between any two.

[0058] In some embodiments of this application, the thickness of the second metal layer 2 is 20 μm to 80 μm. As an example, the thickness of the second metal layer 2 can be any value from 20 μm, 30 μm, 50 μm, 70 μm, and 80 μm, or a range between any two. Within this range, the thickness of the second metal layer 2 can balance conductivity, mechanical strength, and energy density. An appropriate thickness provides sufficient current carrying capacity, while the hot rolling process enables three-dimensional pore connection, improving interfacial bonding stability. If the thickness of the second metal layer 2 is too large, it increases the overall weight and reduces the volumetric energy density of the battery; it may also hinder electrolyte penetration between the active layer and the metal layer, affecting ion transport efficiency. If the thickness of the second metal layer 2 is too small, the mechanical strength is insufficient, making it prone to breakage and detachment during rolling or cycling; the reduced current-carrying cross-sectional area leads to increased local current density and accelerated polarization.

[0059] In some embodiments of this application, the porosity of the second metal layer 2 is 90% to 97%. As an example, the porosity of the second metal can be any one of 90%, 91%, 93%, 95%, or 97%, or a range between any two. A porosity within this range ensures sufficient contact area between the active material and the second metal layer 2, thereby giving the negative electrode superior conductivity and overall stability.

[0060] In some embodiments of this application, the pore size of the second metal layer 2 is 0.6 mm to 1.2 mm. As an example, the pore size of the second metal layer 2 can be any one of 0.6 mm, 0.8 mm, 1 mm, or 1.2 mm, or a range between any two. Within this range, the pore size of the second metal layer 2 can balance the active material loading and ion transport path, avoiding pore blockage caused by excessively small pore sizes or mechanical loosening caused by excessively large pore sizes. If the pore size of the second metal layer 2 is too small, the pore connectivity is poor, the electrolyte distribution is uneven, and local ion transport is obstructed; if the pore size of the second metal layer 2 is too large, the metal layer structure is loose, reducing the bonding force between the current collector and the active layer, and easily causing delamination and peeling.

[0061] In some embodiments of this application, the specific surface area of ​​the second metal layer 2 is 270 cm². 2 / cm 3 ~600cm 2 / cm 3 As an example, the specific surface area of ​​the second metal layer 2 can be 270 cm².2 / cm 3 330cm 2 / cm 3 380cm 2 / cm 3 450cm 2 / cm 3 500cm 2 / cm 3 550cm 2 / cm 3 600cm 2 / cm 3 The specific surface area of ​​the second metal layer 2 can be any one of the specified values ​​or a range between the two. Within this range, the electrochemical reaction activity can be optimized, interfacial impedance reduced, and ion transport efficiency and mechanical stability balanced. If the specific surface area of ​​the second metal layer 2 is too low, there are insufficient active sites, internal resistance increases, and electrolyte distribution becomes uneven. If the specific surface area of ​​the second metal layer 2 is too high, side reactions increase (such as electrolyte decomposition), and mechanical strength decreases.

[0062] In some embodiments of this application, the thickness of the first active layer 3 is 100 μm to 300 μm. As an example, the thickness of the first active layer 3 can be any value among 100 μm, 150 μm, 200 μm, 250 μm, and 300 μm, or a range between any two. If the thickness of the first active layer 3 is too large, it will prolong the diffusion path of lithium ions in the active layer, increase internal resistance, and lead to a decrease in rate performance; if the thickness of the first active layer 3 is too small, the active material loading will be insufficient, reducing electrode capacity and energy density.

[0063] In some embodiments of this application, the areal density of the first active layer 3 is 0.05 g / cm³. 2 ~0.3g / cm 2 As an example, the areal density of the first active layer 3 can be 0.05 g / cm³. 2 0.12g / cm 2 0.18g / cm 2 0.2g / cm 2 0.3g / cm 2 The value of any one of the points or the range between any two.

[0064] In some embodiments of this application, the first active layer 3 includes a first active material, a first conductive agent, and a first binder. The mass ratio of the first active material, the first conductive agent, and the first binder is (60-95):(1-20):(1-15). As an example, the mass ratio of the first active material, the first conductive agent, and the first binder can be any one of 60:1:1, 75:11:8, or 95:20:15, or a range between any two.

[0065] In some embodiments of this application, the first active material includes, but is not limited to, at least one of lithium iron phosphate, lithium cobalt oxide, or lithium manganese iron phosphate. As an example, the first active material may be lithium iron phosphate or lithium cobalt oxide.

[0066] In some embodiments of this application, the first adhesive may be polytetrafluoroethylene, cross-linked waterborne adhesive, or styrene-butadiene rubber adhesive.

[0067] In some embodiments of this application, the thickness of the second active layer 4 is 100 μm to 300 μm. As an example, the thickness of the second active layer 4 can be any one of 100 μm, 150 μm, 200 μm, 250 μm, or 300 μm, or a range between any two. If the thickness of the second active layer 4 is too large, lithium-ion diffusion will be hindered, resulting in a decrease in rate performance; if the thickness of the second active layer 4 is too small, capacity and energy density will be limited.

[0068] In some embodiments of this application, the areal density of the second active layer 4 is 0.05 g / cm³. 2 ~0.3g / cm 2 As an example, the areal density of the second active layer 4 can be 0.05 g / cm³. 2 0.12g / cm 2 0.18g / cm 2 0.2g / cm 2 0.3g / cm 2 The value of any one of the points or the range between any two.

[0069] In some embodiments of this application, the second active material, the second conductive agent, and the second binder are used. The mass ratio of the second active material, the second conductive agent, and the second binder is (70-95):(5-20):(1-10). As an example, the mass ratio of the second active material, the second conductive agent, and the second binder can be any one of 70:5:1, 85:12:5, or 95:20:10, or a range between any two.

[0070] In some embodiments of this application, the second adhesive includes, but is not limited to, at least one of polyvinyl fluoride, styrene-butadiene rubber, or polyacrylic acid. As an example, the second adhesive may be polyvinyl fluoride or styrene-butadiene rubber.

[0071] In some embodiments of this application, the first conductive agent and the second conductive agent each independently include at least one of conductive carbon black, conductive graphite, carbon fiber, or carbon nanotubes. For example, the conductive agent may be conductive carbon black or conductive graphite.

[0072] In some embodiments of this application, the metal in the first metal layer 1 includes copper and / or nickel. That is, the first metal layer 1 can be copper foil or nickel foil.

[0073] In some embodiments of this application, the metal in the second metal layer 2 includes copper and / or nickel. That is, the second metal layer 2 can be foamed copper or foamed nickel.

[0074] Some embodiments of this application also provide a method for preparing a negative electrode sheet, including the following steps:

[0075] S1. The first metal layer 1 and the second metal layer 2 are connected by welding.

[0076] S2. After mixing the first active material, the first conductive agent, and the first binder, a mixture is obtained. The mixture is then used to form the first active layer 3 on the surface of the second metal layer 2 away from the first metal layer 1 by a hot roll forming process.

[0077] S3. Mix the second active material, the second conductive agent, and the second binder in a solvent, and then coat them onto the surface of the first active layer 3 away from the second metal layer 2 to form the second active layer 4.

[0078] In some embodiments of this application, the solvent may be N-methylpyrrolidone.

[0079] This application also provides a battery in some embodiments, including: a negative electrode sheet as described in any of the above embodiments of this application; and / or a negative electrode sheet prepared by the method for preparing the negative electrode sheet as described in any of the above embodiments of this application.

[0080] In some embodiments of this application, the battery further includes a positive electrode, an electrolyte, and a separator. That is, the battery includes a positive electrode, a negative electrode, an electrolyte, and a separator.

[0081] In this embodiment, the materials and structures of the positive electrode current collector 1 and the conductive agent and binder in the positive electrode active material layer are not limited, and the positive electrode structure and composition known in the art that can be used in secondary batteries can be selected.

[0082] In this embodiment, the specific material or type of the separator is not limited, and any separator known in the art that can be used in secondary batteries can be selected.

[0083] It should also be noted that the battery in this application does not limit the specific material or type of electrolyte. Any components and types known in the art that can be used in secondary batteries can be selected, as long as the purpose of this application can be achieved.

[0084] Since the battery provided in this application adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, and will not be described in detail here.

[0085] Since the battery provided in this application adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be described in detail here.

[0086] The present application will be described in detail below with reference to the accompanying drawings and examples. However, the implementation and protection of the present application are not limited thereto. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0087] Example 1

[0088] S1. The copper-clad laminate with foam is used as a current collector. It can be divided into two parts: a copper foil layer (first metal layer) and a copper-clad laminate with foam (second metal layer). The copper foil is 10μm thick and the copper-clad laminate is 40μm thick. The copper-clad laminate and the copper plate are connected by brazing.

[0089] The copper foam has a porosity of 94%, a pore size of 0.8 mm, and a specific surface area of ​​350 cm². 2 / cm 3 .

[0090] S2. Lithium iron phosphate, conductive carbon black and polytetrafluoroethylene are mixed evenly by mechanical stirring, and then the mixture is made into the first active layer on the surface of the foamed copper away from the copper foil by hot roll forming process.

[0091] The mass ratio of lithium iron phosphate, conductive carbon black, and polytetrafluoroethylene is 80:10:10.

[0092] The compaction density of the first active layer is 2.6 g / cm³. 3 It has a thickness of 295 μm and an areal density of 0.11 g / cm³. 2 .

[0093] S3. Lithium iron phosphate, conductive carbon black, and polyvinyl difluoroethylene are mixed evenly with N-methylpyrrolidone by mechanical stirring to obtain a slurry. The slurry is coated on the surface of the first active layer away from the copper foam and then dried and compacted to form the second active layer.

[0094] The mass ratio of lithium iron phosphate, conductive carbon black, and polydifluoroethylene is 80:10:10.

[0095] The solid content of the slurry is 70%;

[0096] The compaction density of the second active layer is 2.6 g / cm³. 3 It has a thickness of 200 μm and an areal density of 0.06 g / cm³. 2 .

[0097] The structure of the prepared negative electrode is shown in the appendix of the instruction manual. Figure 1 .

[0098] Example 2

[0099] The difference between Example 2 and Example 1 is that the thickness of the copper foam layer is 50 μm.

[0100] Example 3

[0101] The difference between Example 3 and Example 1 is that the thickness of the copper foam layer is 60 μm.

[0102] Example 4

[0103] The difference between Example 4 and Example 1 is that the thickness of the copper foam layer is 70 μm.

[0104] Comparative Example 1

[0105] The difference between Comparative Example 1 and Example 1 is that the current collector of Comparative Example 1 does not contain copper foam.

[0106] Comparative Example 2

[0107] The difference between Comparative Example 2 and Example 1 is that Comparative Example 2 does not contain a second active layer.

[0108] Comparative Example 3

[0109] The difference between Comparative Example 3 and Example 1 is that Comparative Example 3 does not contain a first active layer.

[0110] Performance testing

[0111] Diaphragm resistance test:

[0112] The diaphragm resistance is tested using the two-probe method. The electrode or diaphragm is placed on the testing apparatus, ensuring a flat surface, and the pressure gauge is adjusted to fix the sample, guaranteeing good contact between the probe and the sample. After power is applied, the voltage change is recorded, and the sample resistance is calculated using Ohm's law. Six sets of data are tested for each group of electrodes, and the average resistance is then taken.

[0113] Peel strength test:

[0114] The electrode peel strength test was conducted using the 180° peel method. The free end of the electrode was folded 180° and clamped on the upper and lower grippers. A tensile testing machine was used to continuously peel the electrode at a tensile speed of 50 mm / min until the electrode and coating were completely separated. Six sets of data were tested for each electrode, and the average peel strength was then taken.

[0115] The test results of the examples and comparative examples are shown in Table 1.

[0116] Table 1

[0117] Diaphragm resistance / mΩ Peel strength N / m Example 1 4.8 1.8 Example 2 5.1 1.7 Example 3 5.4 1.6 Example 4 5.7 1.5 Comparative Example 1 7.2 1.1 Comparative Example 2 6.8 0.9 Comparative Example 3 7.0 0.8

[0118] As can be seen from the test data in Table 1, Example 1 exhibits the lowest membrane resistance (low resistance helps reduce battery internal resistance and improve energy transfer efficiency) and the highest peel strength (high peel strength helps improve battery mechanical stability and cycle life). The lowest membrane resistance and highest peel strength in Example 1 indicate that it possesses optimal conductivity and adhesion, resulting in the best overall battery performance. Test results from Examples 2-4 show that as the thickness of the foamed copper layer increases, the membrane resistance gradually increases, while the peel strength slightly decreases. This suggests that increasing the thickness of the foamed copper layer may improve the mechanical strength of the current collector (due to its thicker structure making it more resistant to external impacts and deformation), but at the expense of some conductivity and adhesion.

[0119] The diaphragm in Comparative Example 1 has a higher resistance and lower peel strength than in Example 1. This is because the porous structure lacking the foamed copper layer reduces the contact area between the current collector and the active material, resulting in decreased conductivity and adhesion. Comparative Example 2 lacks a second active layer, leading to lower resistance, but the reduced contact area between the single active layer and the current collector significantly decreases the peel strength, indicating that the synergistic effect of the two active layers is crucial for both mechanical stability and conductivity. Comparative Example 3 lacks a first active layer, and the second active layer is directly exposed on the porous foamed copper surface, resulting in uneven distribution of the active material, poor contact, a significant increase in resistance, and the lowest mechanical bonding strength due to unilateral adhesion failure.

[0120] The parts not described in detail in this application are techniques known to those skilled in the art.

[0121] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0122] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "the," and "the" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0123] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A negative electrode sheet characterized by comprising: The negative electrode includes: A current collector, the current collector comprising a first metal layer and a second metal layer disposed on at least one surface of the first metal layer along its thickness direction; the second metal layer having a porous structure; A first active layer is disposed on the surface of the second metal layer on the side away from the first metal layer; The second active layer is disposed on the surface of the first active layer away from the second metal layer.

2. The negative electrode sheet according to claim 1, characterized by The first metal layer and the second metal layer are connected by welding; And / or, the first metal layer comprises a metal foil; And / or, the second metal layer comprises foamed metal.

3. The negative electrode sheet according to claim 1, characterized by The second metal layer and the first active layer are joined by hot rolling.

4. The negative electrode sheet according to claim 1, characterized by The first active layer is a dry-formed film; The second active layer is a wet-formed film.

5. The negative electrode sheet according to claim 1, characterized in that, The thickness of the first metal layer is 4.5 μm to 20 μm; And / or, the thickness of the second metal layer is 20 μm to 80 μm.

6. The negative electrode sheet according to claim 1, characterized in that, The first metal layer and the second metal layer satisfy at least one of the following features (1) to (3): (1) The porosity of the second metal layer is 90% to 97%; (2) The pore size of the second metal layer is 0.6 mm to 1.2 mm; (3) the specific surface area of the second metal layer is 270 cm 2 / cm 3 ~ 600 cm 2 / cm 3 .

7. The negative electrode sheet according to claim 1, characterized in that, The thickness of the first active layer is 100 μm to 300 μm; and / or the first active layer has an areal density of 0.05 g / cm 2 ~ 0.3 g / cm 2 .

8. The negative electrode sheet according to claim 1, characterized in that, The thickness of the second active layer is 100 μm to 300 μm; and / or the second active layer has an areal density of 0.05 g / cm 2 ~ 0.3 g / cm 2 .

9. The negative electrode sheet according to claim 1, characterized in that, The metal in the first metal layer includes copper and / or nickel; And / or, the metal in the second metal layer includes copper and / or nickel.

10. A battery, comprising a negative electrode, characterized in that, The negative electrode includes the negative electrode as described in any one of claims 1 to 9.

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