Negative electrode current collector, secondary battery, battery module, battery pack and electric device containing the same

Abstract

The present application provides a negative electrode current collector, a secondary battery, a battery module, a battery pack and an electric device containing the same. The negative electrode current collector includes: a first metal layer, a pre-lithiation layer and a second metal layer, wherein the pre-lithiation layer is arranged between the first metal layer and the second metal layer, and at least one of the first metal layer and the second metal layer has a porous structure. The negative electrode current collector provided in the embodiment of the present application can effectively extend the cycle life of the battery while improving the coulombic efficiency and energy density of the secondary battery.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a negative electrode current collector, a secondary battery containing the negative electrode current collector, a battery module, a battery pack and an electrical device. Background Art

[0002] In recent years, the application scope of secondary batteries has become more and more extensive. They are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As secondary batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance, etc.

[0003] How to make secondary batteries have both high energy density and good cycle performance is a technical problem that needs to be solved. Summary of the invention

[0004] The present application is made in view of the above technical problems, and its purpose is to provide a negative electrode current collector that effectively prolongs the cycle life of the battery while improving the coulombic efficiency and energy density of the secondary battery.

[0005] In order to achieve the above-mentioned objectives, the present application provides a negative electrode current collector, a secondary battery containing the same, a battery module, a battery pack and an electrical device.

[0006] In a first aspect, the present application provides a negative electrode current collector, comprising: a first metal layer, a pre-lithiation layer and a second metal layer, wherein the pre-lithiation layer is arranged between the first metal layer and the second metal layer, and at least one of the first metal layer and the second metal layer has a porous structure.

[0007] In the embodiment of the present application, the negative electrode current collector has a composite sandwich structure of a metal layer-pre-lithiation layer-metal layer. On the one hand, at least one of the two metal layers has a porous structure, so that the negative electrode active material disposed on the surface of the current collector can contact the pre-lithiation layer. The pre-lithiation layer can be used as a lithium source to pre-compensate for the active lithium consumed by the formation of the negative electrode SEI (Solid electrolyte interphase) film and other processes in the first cycle of the lithium-ion battery, effectively improving the first cycle coulomb efficiency of the battery. The gap left after the lithium layer is consumed reserves space for the volume expansion of the negative electrode material during the lithium insertion process, which can reduce the rupture and polarization of graphite and improve the mechanical stability and cycle performance of the negative electrode. On the other hand, the special composite sandwich structure ensures that the consumption of the pre-lithiation layer will not affect the bonding strength between the negative electrode film layer and the current collector, that is, the negative electrode film layer will not fall off from the negative electrode current collector due to the consumption of the pre-lithiation layer, without damaging the cycle life of the battery.

[0008] In any embodiment, the first metal layer and the second metal layer both have a porous structure.

[0009] When both the first metal layer and the second metal layer have a porous structure, the coulombic efficiency and energy density of the battery can be further improved.

[0010] In any embodiment, the first metal layer is connected to the first surface of the pre-lithiation layer, and the second metal layer is connected to the second surface of the pre-lithiation layer.

[0011] It should be understood that the pre-lithiation layer is disposed between the first metal layer and the second metal layer, and the pre-lithiation layer can be disposed in a variety of ways. In one embodiment, the pre-lithiation layer has a first surface and a second surface opposite to each other along its thickness direction, and the first metal layer and the second metal layer are respectively connected or partially connected to the first surface and the second surface of the pre-lithiation layer. In another embodiment, the pre-lithiation layer is disposed between the first metal layer and the second metal layer by metal rolling bonding. Preferably, the first metal layer and the second metal layer are respectively fixedly connected to the first surface and the second surface of the pre-lithiation layer. In other words, the first metal layer and the second metal layer are respectively in close contact with the first surface and the second surface of the pre-lithiation layer.

[0012] In any embodiment, an area of ​​the first metal layer or the second metal layer is greater than an area of ​​the pre-lithiation layer.

[0013] In any embodiment, a ratio of an area of ​​the first metal layer to an area of ​​the pre-lithiation layer is greater than 1.1.

[0014] In any embodiment, a ratio of an area of ​​the second metal layer to an area of ​​the pre-lithiation layer is greater than or equal to 1.1.

[0015] Through structural design, the embodiment of the present application makes the area of ​​the metal layer in the negative electrode current collector larger than the area of ​​the pre-lithiation layer, and the metal layer partially covers or completely covers the pre-lithiation layer, thereby reducing the exposure area of ​​the pre-lithiation layer at the electrode / electrolyte solid-liquid interface or avoiding direct exposure of the pre-lithiation layer, thereby effectively inhibiting or avoiding the formation of lithium dendrites on the pre-lithiation layer, reducing safety risks, reducing the waste of lithium sources, and improving the pre-lithiation effect, thereby further improving the coulombic efficiency of the secondary battery.

[0016] In any embodiment, an area of ​​the first metal layer is equal to an area of ​​the second metal layer.

[0017] The embodiment of the present application uses a first metal layer and a second metal layer with equal areas, which facilitates industrial processing and improves the production efficiency of the secondary battery.

[0018] In any embodiment, the pre-lithiation layer is a lithium foil.

[0019] The embodiment of the present application uses lithium foil as a pre-lithiation layer without the need for other binders or adhesives. The lithium foil can be used to prepare the above-mentioned composite sandwich structure negative electrode collector through a rolling process. The process is simple and the lithium metal is in direct contact with the collector and the active material, which is beneficial to the transfer of electrons in the electrochemical reaction, can shorten the mass transfer distance of lithium ions, and improve the charge and discharge efficiency of the secondary battery.

[0020] In any embodiment, the pre-lithiation layer is lithium metal powder.

[0021] In any embodiment, the pre-lithiation layer is lithium silicide powder.

[0022] In any embodiment, the redox potential of the first metal layer and the second metal layer is greater than or equal to 0.337V.

[0023] In any embodiment, the first metal layer and / or the second metal layer is / are made of copper metal.

[0024] It should be understood that the materials of the first metal layer and the second metal layer may be the same or different. Preferably, the first metal layer and the second metal layer are made of the same material.

[0025] In any embodiment, the first metal layer and / or the second metal layer is / are porous copper foil.

[0026] In any embodiment, the pore size of the pores in the porous copper foil is 15-500 μm, preferably 20-100 μm.

[0027] In any embodiment, the porosity of the porous copper foil is ≤50%.

[0028] In any embodiment, the thickness of the porous copper foil is 2.5-6 μm, preferably 2.5-4 μm.

[0029] In any embodiment, the first metal layer and / or the second metal layer is / are foamed copper.

[0030] It should be understood that the structures of the first metal layer and the second metal layer may be the same or different. Exemplarily, the first metal layer is a porous copper foil and the second metal layer is a foamed copper. Preferably, the first metal layer and the second metal layer are made of the same material.

[0031] In any embodiment, the pores in the copper foam have a diameter of 0.3-7 mm.

[0032] In any embodiment, the porosity of the copper foam is ≥50%; optionally, it can be 50%-80%.

[0033] In any embodiment, the thickness of the copper foam is 0.8-10 mm.

[0034] In any embodiment, the first metal layer and / or the second metal layer is / are copper wires in a mesh structure.

[0035] In any embodiment, the copper wire has a diameter of 0.02-2 mm.

[0036] In any embodiment, the first metal layer and / or the second metal layer is / are made of nickel.

[0037] In any embodiment, the first metal layer and / or the second metal layer is made of stainless steel.

[0038] In a second aspect, the present application further provides a secondary battery, comprising a negative electrode plate, wherein the negative electrode plate comprises the negative electrode collector described in the first aspect of the present application.

[0039] In a third aspect, the present application further provides a battery module, comprising the secondary battery described in the second aspect of the present application.

[0040] In a fourth aspect, the present application further provides a battery pack, comprising the secondary battery described in the second aspect of the present application and one of the battery modules described in the third aspect of the present application.

[0041] In a fifth aspect, the present application further provides an electrical device, comprising at least one of the secondary battery described in the second aspect of the present application, the battery module described in the third aspect of the present application, and the battery pack described in the fourth aspect of the present application.

[0042] The negative electrode current collector provided in the present application has a composite sandwich structure consisting of a metal layer-pre-lithiation layer-metal layer. It can provide sufficient lithium source for the negative electrode active material through the porous structure of the metal layer without exposing the pre-lithiation layer to the electrode / electrolyte, thereby replenishing the active lithium ions consumed by the negative electrode during the formation of the SEI film and the battery cycle, effectively improving the first-cycle coulomb efficiency of the battery, increasing the energy density of the battery, and extending the cycle life of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order 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 ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work. In the drawings, the drawings are not drawn according to the actual scale.

[0044] Figure 1a It is a schematic diagram of a negative electrode current collector of the present application.

[0045] Figure 1b It is a schematic diagram of a negative electrode current collector provided with active materials in the present application.

[0046] Figure 2a It is a schematic diagram of another negative electrode current collector of the present application.

[0047] Figure 2b It is a schematic diagram of another negative electrode current collector provided with active material in the present application.

[0048] Figure 3 It is a schematic flow chart of the preparation of a negative electrode current collector of the present application.

[0049] Figure 4a This is a schematic diagram of another negative electrode current collector of the present application.

[0050] Figure 4b This is a schematic diagram of another negative electrode current collector of the present application.

[0051] Figure 5 It is a schematic structural diagram of a secondary battery of the present application.

[0052] Figure 6 It is a schematic diagram of a square structure of a secondary battery in the present application.

[0053] Figure 7 It is a schematic diagram of a battery module of the present application.

[0054] Figure 8 It is a schematic diagram of a battery pack of the present application.

[0055] Fig. 9 This is an exploded view of a battery pack of the present application. DETAILED DESCRIPTION

[0056] Hereinafter, the negative electrode current collector, the secondary battery containing the negative electrode current collector, the battery module and the electrical device of the present application 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 structure 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 descriptions 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.

[0057] The "ranges" disclosed in this application are defined in the form of lower limits and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined in this way can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a particular parameter, it is understood that 60 - Ranges of 110 and 80-120 are also contemplated. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed in this article, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥2, it 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.

[0058] In the description of the present application, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", "inside", "outside", etc., indicating the orientation or positional relationship, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but is within the allowable error range. "Parallel" is not strictly parallel, but is within the allowable error range.

[0059] The directional words appearing in the following description are all directions shown in the figures, and do not limit the specific structure of this application. In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0060] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0061] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0062] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0063] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0064] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0065] This application takes lithium-ion batteries as an example. Lithium-ion batteries are a typical secondary battery. Since they rely on the chemical reaction of lithium ions being embedded and released between the positive and negative electrodes for charging and discharging, lithium-ion batteries are also called rocking-chair batteries. During the charging process of lithium-ion batteries, lithium ions are released from the positive electrode, moved and embedded in the negative electrode; and during the discharging process, lithium ions are released from the negative electrode, moved and embedded in the positive electrode.

[0066] In the electrochemical reaction of lithium-ion batteries, due to the influence of various factors such as the structural changes of electrode materials during the lithium insertion and de-lithiation process and the side reactions of active materials, the lithium ions extracted from the positive electrode material cannot completely return to the positive electrode, resulting in the loss of lithium-ion battery capacity and the decrease of coulombic efficiency, which limits the development of high energy density lithium-ion batteries.

[0067] For negative electrode materials, the formation of SEI (Solid electrolyte interphase) film is one of the main reasons why the initial discharge capacity of the negative electrode is smaller than the charging capacity.

[0068] It should be understood that the "lithium insertion" and "embedding" processes described in this application refer to the process in which lithium ions are embedded in the positive electrode material and the negative electrode material due to electrochemical reactions, and the "extraction", "delithium" and "extraction" processes described in this application refer to the process in which lithium ions are extracted from the positive electrode material and the negative electrode material due to electrochemical reactions.

[0069] [Negative electrode]

[0070] The negative electrode sheet generally includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0071] The negative electrode current collector of the present application solves the problem of low coulombic efficiency and short life of the secondary battery due to irreversible consumption of lithium ions through a special structural design. The composite sandwich structure of metal layer-pre-lithiation layer-metal layer is used as the negative electrode current collector of the secondary battery, which can improve the energy density and coulombic efficiency of the secondary battery while extending the cycle life of the battery. Specifically, in one embodiment, Figure 1a As shown, the negative electrode current collector 100 includes:

[0072] The first metal layer 101 , the pre-lithiation layer 103 , and the second metal layer 102 .

[0073] Among them, the pre-lithiation layer 103 is used to supplement lithium ions for the active material arranged on the surface of the negative electrode collector in the electrochemical reaction of the lithium-ion battery. The pre-lithiation layer 103 is arranged between the first metal layer 101 and the second metal layer 102, and at least one of the first metal layer 101 and the second metal layer 102 has a porous structure.

[0074] In this embodiment, the first metal layer, the pre-lithiation layer and the second metal layer form a special composite sandwich structure, the negative electrode active material is arranged on the surface of the current collector, that is, the surface of the metal layer, and at least one of the two metal layers has a porous structure, so that the active material arranged on the surface of the current collector can contact the pre-lithiation layer through the porous structure, and the pre-lithiation layer can be used as a lithium source to supplement the formation of the SEI film and the active lithium consumed during the battery cycle, effectively improving the first cycle coulomb efficiency of the secondary battery. In addition, the special composite sandwich structure makes the consumption of the pre-lithiation layer not affect the structure between the active material and the current collector, that is, the active material will not fall off from the negative electrode current collector due to the consumption of the pre-lithiation layer, thereby extending the cycle life of the battery. Moreover, when the pre-lithiation layer is completely consumed, the negative electrode current collector forms a hollow structure composed of two metal layers, which can improve the battery performance degradation caused by the accumulation of byproducts at the electrode during the battery cycle, resulting in volume expansion; on the other hand, it can also provide expansion space for the structural changes of the active material during the battery cycle, reduce the problem of battery kinetic performance degradation caused by the expansion of the active material, and further extend the battery cycle life.

[0075] In the negative electrode current collector of the present application, at least one of the first metal layer 101 or the second metal layer 102 has a porous structure.

[0076] In some embodiments, both the first metal layer 101 and the second metal layer 102 have a porous structure. When both the first metal layer and the second metal layer have a porous structure, both sides of the negative electrode current collector can contact the negative electrode active material through the porous structure, increasing the contact area between the pre-lithiation layer and the negative electrode active material, further improving the coulombic efficiency of the lithium-ion battery; both sides of the negative electrode current collector can be provided with active materials and the active materials on both sides can participate in the lithium-ion battery reaction, effectively improving the energy density of the lithium-ion battery.

[0077] It should be understood that the negative electrode active material contacts the pre-lithiation layer through the metal layer having a porous structure.

[0078] The pre-lithiation layer 103 has a first surface and a second surface opposite to each other in the thickness direction thereof.

[0079] Optionally, in one embodiment, the first metal layer 101 is connected to a first surface of the pre-lithiation layer 103 , and the second metal layer 102 is connected or partially connected to a second surface of the pre-lithiation layer 103 .

[0080] Specifically, the first metal layer, the pre-lithiation layer and the second metal layer can be formed by rolling and other processes so that the first surface and the second surface of the pre-lithiation layer are connected or partially connected to the first metal layer and the second metal layer respectively.

[0081] Optionally, in one embodiment, the pre-lithiation layer 103 is disposed between the first metal layer 101 and the second metal layer 102 via a binder.

[0082] It should be understood that the pre-lithiation layer can be arranged between the first metal layer and the second metal layer in a variety of ways. Preferably, the first metal layer 101 and the second metal layer 102 are fixedly connected to the first surface and the second surface of the pre-lithiation layer 103, respectively. In other words, the first metal layer 101 and the second metal layer 102 are in close contact with the first surface and the second surface of the pre-lithiation layer 103, respectively.

[0083] Alternatively, if Figure 2a As shown, in one embodiment, the first metal layer 101 and the second metal layer 102 both have a porous structure. The negative electrode current collector 200 having a double-sided porous structure is provided with an active material, preferably, as Figure 2b As shown, the active material is disposed on the first metal layer 101 and the second metal layer 102 of the negative electrode current collector 200 having a porous structure.

[0084] In this embodiment, the negative electrode current collector has two metal layers with a porous structure, so that both sides of the negative electrode current collector can contact the active material through the porous structure, thereby increasing the contact area between the pre-lithiation layer and the active material, and further improving the coulombic efficiency of the secondary battery; active materials can be arranged on both sides of the negative electrode current collector and the active materials on both sides can participate in the battery reaction, effectively improving the energy density of the secondary battery.

[0085] Optionally, in one embodiment, the area of ​​the first metal layer 101 and / or the area of ​​the second metal layer 102 is greater than the area of ​​the pre-lithiation layer 103. Specifically, the ratio of the area of ​​the first metal layer 101 to the area of ​​the pre-lithiation layer 103 is greater than or equal to 1.1; and / or the ratio of the area of ​​the second metal layer 102 to the area of ​​the pre-lithiation layer 103 is greater than or equal to 1.1.

[0086] Through structural design, the embodiment of the present application makes the area of ​​the metal layer in the negative electrode current collector larger than the area of ​​the pre-lithiation layer, and the metal layer partially covers or completely covers the pre-lithiation layer, and can be closed at the edge of the pre-lithiation layer to wrap the pre-lithiation layer, reducing the exposure area of ​​the pre-lithiation layer at the electrode / electrolyte solid-liquid interface or avoiding direct exposure of the pre-lithiation layer, thereby effectively inhibiting or avoiding the formation of lithium dendrites on the pre-lithiation layer, reducing the waste of lithium sources, improving the pre-lithiation effect, and further improving the coulombic efficiency of the secondary battery.

[0087] Optionally, in one embodiment, the first metal layer 101 has a first region and a second region, and the second metal layer 102 has a first region and a second region, wherein the first region of the first metal layer 101 is connected to the first surface of the pre-lithiation layer 103, the first region of the second metal layer 102 is connected to the second surface of the pre-lithiation layer 103, and the second region of the first metal layer 101 is connected to the second region of the second metal layer 102.

[0088] Preferably, in one embodiment, the second region of the first metal layer 101 surrounds the first region of the first metal layer 101 ; and the second region of the second metal layer 102 surrounds the first region of the second metal layer 102 .

[0089] Optionally, in one embodiment, the area of ​​the first metal layer 101 is equal to the area of ​​the second metal layer 102 .

[0090] The embodiment of the present application adopts a first metal layer and a second metal layer of equal area. On the one hand, the area of ​​the first metal layer and the area of ​​the second metal layer are both larger than the area of ​​the pre-lithiation layer, so that the pre-lithiation layer is completely covered, thereby avoiding exposure of the pre-lithiation layer to the electrode / electrolyte solid-liquid interface, thereby improving the pre-lithiation effect. At the same time, on the other hand, the use of a first metal layer and a second metal layer of equal area facilitates industrial processing and improves the production efficiency of the secondary battery.

[0091] Optionally, in one embodiment, the pre-lithiation layer 103 is a lithium foil.

[0092] Specifically, Figure 3 The figure is a schematic flow chart of preparing a negative electrode current collector according to an embodiment of the present application. Lithium foil is inserted into the first metal layer and the second metal layer, and the three are connected together by rolling to obtain a composite sandwich structure of metal layer-lithium foil-metal layer.

[0093] The embodiment of the present application uses lithium foil as a pre-lithiation layer, without the need for other binders or adhesives. The lithium foil can be directly connected to the metal layer through a rolling process to prepare the above-mentioned composite sandwich structure negative electrode collector. The process is simple and the lithium metal is in direct contact with the collector and the active material, which is beneficial to the transfer of electrons in the electrochemical reaction, can shorten the mass transfer distance of lithium ions, and improve the charge and discharge efficiency of the secondary battery.

[0094] Optionally, in one embodiment, the pre-lithiation layer 103 is lithium metal powder.

[0095] Optionally, in one embodiment, the pre-lithiation layer 103 is lithium silicide powder.

[0096] Specifically, lithium metal powder or lithium silicide powder can be directly disposed between the first metal layer 101 and the second metal layer 102, or can be disposed between the first metal layer 101 and the second metal layer 102 via a binder and / or other additives, and the embodiment of the present application does not limit this.

[0097] Alternatively, in one embodiment, the pre-lithiation layer 103 is a lithium salt compound capable of providing lithium ions to the active material.

[0098] Optionally, in one embodiment, the redox potential of the first metal layer 101 and the second metal layer 102 is greater than or equal to 0.337V.

[0099] It should be understood that in a secondary battery, the negative electrode has a lower potential than the positive electrode. This embodiment uses a metal material with a redox potential greater than or equal to 0.377V as a current collector, which can maintain electrochemical stability at low potentials, that is, no redox reaction occurs at low potentials, ensuring that the electrochemical reaction of the battery proceeds normally.

[0100] Optionally, in one embodiment, the first metal layer 101 and / or the second metal layer 102 is made of metal copper material.

[0101] It should be understood that the materials of the first metal layer 101 and the second metal layer 102 may be the same or different. Preferably, the first metal layer 101 and the second metal layer 102 are made of the same material.

[0102] Optionally, in one embodiment, the first metal layer 101 and / or the second metal layer 102 is a porous copper foil.

[0103] Optionally, in one embodiment, the pore size of the porous copper foil is 15-500 μm, preferably 20-100 μm.

[0104] Optionally, in one embodiment, the porosity of the porous copper foil is ≤50%.

[0105] Optionally, in one embodiment, the thickness of the porous copper foil is 2.5-6 μm, preferably 2.5-4 μm.

[0106] Optionally, in one embodiment, the first metal layer 101 and / or the second metal layer 102 is foam copper.

[0107] It should be understood that the structures of the first metal layer 101 and the second metal layer 102 may be the same or different. Exemplarily, the first metal layer 101 is a porous copper foil, and the second metal layer 102 is a foamed copper. Preferably, the first metal layer 101 and the second metal layer 102 are made of the same material.

[0108] This embodiment uses foamed copper as the negative electrode current collector metal layer material. Foamed copper has a larger specific surface area and can carry more active materials than planar materials, providing more active substances for the electrochemical reaction of the secondary battery, further improving the energy density of the secondary battery.

[0109] Figure 4a This is a schematic diagram of another negative electrode current collector 401 according to an embodiment of the present application; Figure 4b FIG. 4 is a schematic diagram of another negative electrode current collector 402 according to an embodiment of the present application.

[0110] For example, in Figure 4a In the embodiment, the first metal layer 101 of the negative electrode current collector 401 is a porous copper foil, and the second metal layer 102 is a foam copper; Figure 4b In the embodiment, the first metal layer 101 and the second metal layer 102 of the negative electrode current collector 402 are both made of foamed copper.

[0111] Optionally, in one embodiment, the diameter of the pores in the copper foam is 0.3-7 mm.

[0112] Optionally, in one embodiment, the porosity of the copper foam is 50%-80%.

[0113] Optionally, in one embodiment, the thickness of the copper foam is 0.8-10 mm.

[0114] Optionally, in one embodiment, the first metal layer 101 and / or the second metal layer 102 is a copper wire with a mesh structure.

[0115] Optionally, in one embodiment, the diameter of the copper wire is 0.02-2 mm.

[0116] Optionally, in one embodiment, the first metal layer 101 and / or the second metal layer 102 is made of metal nickel material.

[0117] Optionally, in one embodiment, the first metal layer 101 and / or the second metal layer 102 is made of stainless steel.

[0118] Preferably, the first copper foil and the second copper foil have the same area, thickness, pore size and porosity.

[0119] Figure 5 A schematic structural diagram of a secondary battery according to an embodiment of the present application is shown.

[0120] like Figure 5 As shown, the present application also provides a secondary battery 500, including:

[0121] The negative electrode sheet 501 includes the negative electrode current collector described in any embodiment of the present application.

[0122] Optionally, in one embodiment, the negative electrode plate 501 further includes:

[0123] The active material layer 502 is disposed on the surface of the negative electrode current collector and contacts the pre-lithiation layer of the negative electrode current collector through the porous structure of the negative electrode current collector; the area of ​​the active material layer is larger than the area of ​​the pre-lithiation layer.

[0124] The negative electrode film layer may be disposed on only one surface of the negative electrode current collector, or may be disposed on both surfaces of the negative electrode current collector.

[0125] Optionally, in one embodiment, the negative electrode active material may adopt a negative electrode active material for a battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0126] like Figure 1b, which is a schematic diagram of a negative electrode current collector and an active material disposed thereon in accordance with an embodiment of the present application. Specifically, the negative electrode active material and the additive form a negative electrode film layer which is coated on the negative electrode current collector 100 to form a negative electrode film layer 104; preferably, the active material is disposed on the first metal layer 101 of the negative electrode current collector 100 having a porous structure.

[0127] Optionally, in one embodiment, the negative electrode film layer further includes a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0128] Optionally, in one embodiment, the negative electrode film layer further includes a conductive agent, which can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0129] Optionally, in one embodiment, the negative electrode film layer further includes other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0130] [Positive electrode]

[0131] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material of the first aspect of the present application.

[0132] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0133] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0134] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523), LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211), LiNi0.6Co At least one of 0.2Mn0.2O2 (also referred to as NCM622), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.15A10.05O2) and modified compounds thereof. Examples of lithium phosphates containing an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0135] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0136] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0137] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0138] [Electrolytes]

[0139] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0140] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0141] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0142] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0143] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0144] [Isolation film]

[0145] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0146] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0147] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0148] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0149] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0150] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 6 The secondary battery 500 is a square structure as an example.

[0151] Figure 7 700 is an example of a battery module. Figure 7 In the battery module 700, the plurality of secondary batteries 500 may be arranged in sequence along the length direction of the battery module 700. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 500 may be fixed by fasteners.

[0152] Optionally, in one embodiment, the battery module 700 may further include a housing having a receiving space, and the plurality of secondary batteries 500 may be received in the receiving space.

[0153] Optionally, in one embodiment, the battery modules mentioned above may also be assembled into a battery pack. The number of battery modules contained in the battery pack may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0154] Figure 8 and Fig. 9 800 is an example of a battery pack. Figure 8 and Fig. 9 The battery pack 800 may include a battery box and a plurality of battery modules 700 disposed in the battery box. The battery box includes an upper box body 801 and a lower box body 802. The upper box body 801 can cover the lower box body 802 and form a closed space for accommodating the battery modules 700. The plurality of battery modules 700 may be arranged in the battery box in any manner.

[0155] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0156] As an electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0157] As an example of an electric device, the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module may be used.

[0158] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0159] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0160] Examples 1-14

[0161] (1) Preparation of negative electrode current collector: Use porous copper foil, copper foam, and copper wire as the first metal layer and the second metal layer respectively, and use a rolling process with lithium foil (pre-lithiation layer) to prepare a negative electrode current collector with a composite sandwich structure as the current collector of the negative electrode of the secondary battery. The area of ​​the first metal layer is equal to the area of ​​the second metal layer, and the area of ​​the first metal layer and the area of ​​the second metal layer are both larger than the area of ​​the pre-lithiation layer. The ratio of the area of ​​the first metal layer or the area of ​​the second metal layer to the area of ​​the pre-lithiation layer is greater than or equal to 1.1. For example, the side length of the square first metal layer and the second metal layer of equal area is 5-10 mm longer than the side length of the square pre-lithiation layer. For specific parameters of the first metal layer and the second metal layer, see Table 1.

[0162] Table 1

[0163]

[0164]

[0165] In Table 1, A represents porous copper foil, B represents copper wire nonwoven fabric, C represents foam copper, D represents nonporous copper foil, and X / Y represents the ratio of the area of ​​the first metal layer or the area of ​​the second metal layer to the area of ​​the pre-lithiation layer.

[0166] (2) Preparation of negative electrode sheet: artificial graphite, a negative electrode active material, acetylene black, a binder styrene butadiene rubber (SBR), and a thickener sodium carboxymethyl cellulose (CMC-Na) are mixed in a mass ratio of 96:1:1:1, and then deionized water is added as a solvent. The mixture is stirred into a negative electrode slurry according to a method known in the art. The negative electrode slurry is evenly coated on a negative electrode current collector copper foil, and a negative electrode film layer is obtained after drying. The negative electrode sheet is then obtained through a cold pressing process.

[0167] (3) Preparation of positive electrode sheet: The positive electrode active material lithium iron phosphate, the binder polyvinylidene fluoride, and the conductive agent acetylene black are mixed in a mass ratio of 97:2:1, and then the solvent N-methylpyrrolidone (NMP) is added to adjust the viscosity. The mixture is fully stirred into a positive electrode slurry according to a method known in the art; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and the positive electrode film layer is obtained after drying, and then the positive electrode sheet is obtained through a cold pressing process.

[0168] (4) Preparation of isolation film: A polyethylene (PE) film was used as the isolation film.

[0169] (5) Preparation of electrolyte: In an argon atmosphere glove box with a water content of less than 10 ppm, ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 30:40:3 to obtain an organic solvent, 1% by mass of vinylene carbonate (VC) was added, and then 1 mol / L of LiPF6 was uniformly dissolved in the above organic solvent to obtain an electrolyte.

[0170] (6) Preparation of secondary batteries: The positive electrode sheet, the separator, and the negative electrode sheet are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed into an aluminum casing, the top cover is welded, and the electrolyte is injected after drying. After standing, forming, sealing welding, aging, capacity and other processes, a secondary battery is obtained.

[0171] Comparative Example 1

[0172] The preparation steps of Comparative Example 1 are the same as those of Example 1, except that in step (1), a copper foil with a thickness of 6 μm is used as the negative electrode current collector of the lithium ion battery.

[0173] Comparative Example 2

[0174] The preparation steps of Comparative Example 2 are the same as those of Example 1, except that: the negative electrode current collector in step (1) includes a first metal layer, the first metal layer is a porous copper foil, and a lithium foil is arranged on the first metal layer by a calendering process.

[0175] Battery performance test

[0176] 1. First-cycle Coulomb efficiency

[0177] At 25°C, the secondary batteries prepared in each embodiment and comparative example were charged at a constant current of 1C to a charging cut-off voltage V1, then charged at a constant voltage to a current ≤ 0.05C, and left to stand for 5 minutes; then the secondary batteries prepared in each embodiment and comparative example were discharged at a constant current of 1C to a cut-off voltage V2, and left to stand for 5 minutes. This is the first charge and discharge cycle. The first charge capacity and the first discharge capacity were recorded respectively. The first coulomb efficiency is the ratio of the first discharge capacity to the first charge capacity. The test results are shown in Table 2.

[0178] 2. Cycle life test

[0179] At 25°C, the secondary battery prepared in each embodiment and comparative example is charged at a constant current of 1C to a charge cut-off voltage V1, then charged at a constant voltage to a current ≤ 0.05C, left to stand for 5 minutes, and then discharged at a constant current of 0.33C to a discharge cut-off voltage V2, left to stand for 5 minutes, which is a charge and discharge cycle. According to this method, the battery is subjected to a cyclic charge and discharge test until the battery capacity decays to 80%. The number of cycles at this time is the cycle life of the battery. The test results are shown in Table 2.

[0180] Table 2

[0181] First-cycle Coulomb efficiency Cycle life (cycles) Example 1 99.80％ 5849 Example 2 99.76％ 5137 Example 3 98.90％ 4457 Example 4 97.20％ 4186 Example 5 98.50％ 4964 Example 6 99.10％ 4050 Example 7 99.84％ 4832 Example 8 99.84％ 4597 Example 9 99.60％ 4854 Example 10 99.41％ 4525 Embodiment 11 99.74％ 5461 Example 12 99.53％ 5206 Embodiment 13 98.26％ 4967 Comparative Example 1 93.00％ 2800 Comparative Example 2 95.30％ 4000

[0182] It can be seen from the above-mentioned lithium-ion battery performance test that the negative electrode current collector provided in the present application can effectively improve the first-cycle coulomb efficiency and cycle life of the lithium-ion battery.

[0183] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode current collector, comprising: A first metal layer, a pre-lithiation layer, and a second metal layer; Wherein, the pre-lithiation layer is disposed between the first metal layer and the second metal layer, and at least one of the first metal layer and the second metal layer has a porous structure; An area of ​​the first metal layer or the second metal layer is greater than an area of ​​the pre-lithiation layer.

2. The negative electrode current collector according to claim 1, wherein: The first metal layer and the second metal layer both have a porous structure.

3. The negative electrode current collector according to claim 1, wherein: The ratio of the area of ​​the first metal layer to the area of ​​the pre-lithiation layer is greater than or equal to 1.1, and / or A ratio of an area of ​​the second metal layer to an area of ​​the pre-lithiation layer is greater than or equal to 1.

1.

4. The negative electrode current collector according to claim 3, wherein: The area of ​​the first metal layer is equal to the area of ​​the second metal layer.

5. The negative electrode current collector according to any one of claims 1 to 4, wherein The pre-lithiation layer is a lithium foil.

6. The negative electrode current collector according to any one of claims 1 to 4, wherein The pre-lithiation layer is lithium metal powder.

7. The negative electrode current collector according to any one of claims 1 to 4, wherein The pre-lithiation layer is lithium silicide powder.

8. The negative electrode current collector according to any one of claims 1 to 4, wherein The redox potential of the first metal layer and the second metal layer is greater than or equal to 0.337V.

9. The negative electrode current collector according to any one of claims 1 to 4, wherein: The first metal layer and / or the second metal layer is made of copper material.

10. The negative electrode current collector according to claim 9, wherein: The first metal layer and / or the second metal layer is / are porous copper foil.

11. The negative electrode current collector according to claim 10, wherein: The pores in the porous copper foil have a pore size of 15-500 μm.

12. The negative electrode current collector according to claim 10, wherein: The porosity of the porous copper foil is ≤50%.

13. The negative electrode current collector according to claim 10, wherein: The thickness of the porous copper foil is 2.5-6 μm.

14. The negative electrode current collector according to any one of claims 1 to 4, wherein: The first metal layer and / or the second metal layer is foam copper.

15. The negative electrode current collector according to claim 14, wherein: The pores in the copper foam have a diameter of 0.3-7 mm.

16. The negative electrode current collector according to claim 14, wherein: The porosity of the foamed copper is ≥50%.

17. The negative electrode current collector according to claim 16, wherein: The porosity of the foamed copper is 50%-80%.

18. The negative electrode current collector according to claim 14, wherein: The thickness of the foam copper is 0.8-10 mm.

19. The negative electrode current collector according to any one of claims 1 to 4, wherein: The first metal layer and / or the second metal layer is / are copper wires with a mesh structure.

20. The negative electrode current collector according to claim 19, wherein: The diameter of the copper wire is 0.02-2 mm.

21. The negative electrode current collector according to any one of claims 1 to 4, wherein: The first metal layer and / or the second metal layer is made of nickel material.

22. The negative electrode current collector according to any one of claims 1 to 4, wherein: The first metal layer and / or the second metal layer is made of stainless steel. 23 . A secondary battery comprising a negative electrode plate, wherein the negative electrode plate comprises the negative electrode collector according to claim 1 .

24. The secondary battery according to claim 23, wherein The negative electrode plate also includes: An active material layer is disposed on the surface of the negative electrode current collector and contacts the pre-lithiation layer of the negative electrode current collector through the porous structure of the negative electrode current collector; the area of ​​the active material layer is greater than the area of ​​the pre-lithiation layer.

25. A battery module comprising the secondary battery according to claim 23. 26 . A battery pack comprising one of the secondary battery according to claim 23 and the battery module according to claim 25 . 27 . An electrical device comprising at least one of the secondary battery according to claim 23 or 24, the battery module according to claim 25, and the battery pack according to claim 26.

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