Composite current collector and electrochemical device comprising the same

Abstract

The utility model provides a kind of composite current collector and electrochemical device, including porous substrate layer, the side surface of porous substrate layer is sequentially provided with first adhesive layer and first conductive layer, the other side surface of porous substrate layer is sequentially provided with second adhesive layer and second conductive layer;First adhesive layer is sequentially divided into first transition layer and first bonding layer, first transition layer is set at the surface pore of porous substrate layer, and first bonding layer is set between porous substrate layer and first conductive layer;Second adhesive layer is sequentially divided into second transition layer and second bonding layer, second transition layer is set at the surface pore of porous substrate layer, and second bonding layer is set between porous substrate layer and second conductive layer.The application utilizes the surface roughness and pore design of porous substrate layer, improves the mechanical riveting degree of adhesive layer and porous substrate layer, increases the peeling force, and its pore can also discharge adhesive layer bubble, avoid dot-like corrosion, to improve the electrolyte corrosion resistance of composite current collector.

Description

Technical Field

[0001] This utility model belongs to the field of current collector technology, and relates to a composite current collector and an electrochemical device including the same. Background Technology

[0002] Lithium-ion batteries, currently the most widely used chemical energy devices, are no longer able to meet the demands of societal development due to their limited energy density, high cost, and poor safety. To reduce battery costs, increase energy density, and improve the safety, toughness, and bending resistance of the positive and negative electrodes, recent research has focused on replacing traditional metal current collectors with lightweight, flexible metallized plastic composite film materials. These composite current collectors consist of an inner polymer layer and two conductive metal layers on either side. However, during the deposition of the conductive layer on the polymer film surface, internal stress is generated due to ion bombardment, interface mismatch, film growth phase transformation stress, and thermal stress. After deposition, this internal stress is partially released over time through plastic deformation and the disappearance of defects. As the internal stress is partially released, it gradually decreases, leading to a reduction in shear stress at the polymer film-conductive layer interface. This results in low adhesion between the conductive layer and the polymer film, causing the conductive layer on the composite current collector to detach during electrode processing and the lithium-ion battery's lifespan. This, in turn, leads to the detachment of the positive electrode material, ultimately causing battery failure. In addition, highly corrosive substances in the electrolyte can also accelerate the occurrence of the above phenomena.

[0003] To address these issues, current improvement methods primarily involve adding an electrolyte-resistant adhesive layer and a passivation layer between the conductive layer and the polymer film. However, existing coating processes struggle to achieve perfectly uniform distribution of the adhesive and passivation layers, leading to the presence of air bubbles in the adhesive layer. This makes it susceptible to pitting corrosion by highly corrosive substances in the electrolyte, resulting in failure. Furthermore, the polymer films currently used often have low surface roughness, resulting in weak adhesion between the adhesive and the adhesive layer, making them prone to peeling or even detachment. Utility Model Content

[0004] The technical problem to be solved by this utility model is that the existing current collector has poor resistance to electrolyte corrosion, and the adhesive layer and polymer film are easy to peel off or fall off, which affects the conductivity stability of the current collector.

[0005] Therefore, this utility model provides a composite current collector and an electrochemical device including the same.

[0006] The technical solution adopted by this utility model to solve its technical problem is:

[0007] In a first aspect, the present invention provides a composite current collector, the composite current collector comprising a porous substrate layer, a first adhesive layer, a second adhesive layer, a first conductive layer, and a second conductive layer;

[0008] The first adhesive layer and the first conductive layer are sequentially disposed on one side surface of the porous substrate layer, and the second adhesive layer and the second conductive layer are sequentially disposed on the other side surface of the porous substrate layer.

[0009] Along the direction from the first adhesive layer toward the first conductive layer, the first adhesive layer is sequentially divided into a first transition layer and a first bonding layer. The first transition layer is disposed at the surface pores of the porous substrate layer, and the first bonding layer is disposed between the porous substrate layer and the first conductive layer.

[0010] Along the direction from the second adhesive layer toward the second conductive layer, the second adhesive layer is sequentially divided into a second transition layer and a second bonding layer. The second transition layer is disposed at the surface pores of the porous substrate layer, and the second bonding layer is disposed between the porous substrate layer and the second conductive layer.

[0011] Furthermore, the surface pore depth of the porous substrate layer is 0.2μm to 5μm, for example, it can be 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0012] Furthermore, the depth of the first transition layer at the pores on the surface of the porous substrate layer is 0.05μm to 2μm, for example, it can be 0.05μm, 0.1μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0013] Furthermore, the depth of the second transition layer at the pores on the surface of the porous substrate layer is 0.05μm to 2μm, for example, it can be 0.05μm, 0.1μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] Furthermore, the surface porosity of the porous substrate layer is 30°~90°, for example, it can be 30°, 40°, 50°, 60°, 70°, 80°, 90°, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] Furthermore, the porosity of the porous substrate layer is 30% to 95%, for example, it can be 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Furthermore, the average pore size of the porous substrate layer is 0.01μm to 1μm, for example, it can be 0.01μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Furthermore, the thickness of the porous substrate layer is 2μm to 20μm, for example, it can be 2μm, 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] Furthermore, the tensile strength of the composite current collector is 100MPa to 1000MPa, for example, it can be 100MPa, 200MPa, 300MPa, 400MPa, 500MPa, 600MPa, 700MPa, 800MPa, 900MPa, 1000MPa, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Furthermore, the thickness of the first adhesive layer is 0.1μm to 2μm, for example, it can be 0.1μm, 0.2μm, 0.4μm, 0.6μm, 0.8μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Furthermore, the thickness of the second adhesive layer is 0.1μm to 2μm, for example, it can be 0.1μm, 0.2μm, 0.4μm, 0.6μm, 0.8μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Furthermore, the thickness of the first conductive layer is 0.2μm to 3μm, for example, it can be 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Furthermore, the thickness of the second conductive layer is 0.2μm to 3μm, for example, it can be 0.2μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Secondly, this utility model provides an electrochemical device, which includes a positive electrode and a negative electrode; wherein at least one of the positive electrode or the negative electrode adopts the composite current collector described in the first aspect.

[0024] The beneficial effects of this utility model are as follows:

[0025] The composite current collector of this application utilizes the surface roughness and pore design of the porous substrate layer to improve the mechanical bonding between the adhesive layer and the porous substrate layer while ensuring the tensile strength of the composite current collector, thereby increasing the peeling force. In addition, the pores of the porous substrate layer can also expel air bubbles from the adhesive layer, avoiding pitting corrosion, and thus improving the electrolyte corrosion resistance of the composite current collector itself. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the composite current collector in this utility model;

[0028] Figure 2 This is a schematic diagram of the composite current collector provided in Embodiment 1 of this utility model;

[0029] Wherein, 1-porous substrate layer; 2-first adhesive layer; 3-second adhesive layer; 4-first conductive layer; 5-second conductive layer; 6-porous PE layer; 7-first aluminum layer; 8-second aluminum layer. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the present invention, and therefore only show the components relevant to the present invention.

[0031] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0032] It should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0033] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0034] An electrochemical device includes a positive electrode and a negative electrode; wherein at least one of the positive electrode or the negative electrode is a composite current collector.

[0035] The structural schematic diagram of the above composite current collector is shown below. Figure 1 As shown, it includes a porous substrate layer 1, a first adhesive layer 2, a second adhesive layer 3, a first conductive layer 4, and a second conductive layer 5; the first adhesive layer 2 and the first conductive layer 4 are sequentially disposed on one side surface of the porous substrate layer 1, and the second adhesive layer 3 and the second conductive layer 5 are sequentially disposed on the other side surface of the porous substrate layer 1.

[0036] The composite current collector of this invention features a porous substrate layer 1. An adhesive is filled into the pores on the surface of the porous substrate layer 1 to form a first transition layer and a second transition layer. This design removes gas from the current collector and effectively solves the problem of air bubbles forming in the adhesive layer. It also improves the adhesion of the adhesive layer to the surface of the porous substrate layer 1, further enhancing the corrosion resistance of the composite current collector. Furthermore, the high surface roughness of the porous substrate layer 1 in this application effectively increases the bonding area between the adhesive layer and the porous substrate layer 1, thereby improving adhesion.

[0037] It should be noted that the first adhesive layer 2 and the second adhesive layer 3 in this utility model can preferentially adhere to the first conductive layer 4 and the second conductive layer 5, so that the air bubbles generated after the first adhesive layer 2 and the second adhesive layer 3 shrink pores are located at the interface between the adhesive layer and the porous substrate layer 1, which is more conducive to the discharge of air bubbles in the first adhesive layer 2 and the second adhesive layer 3.

[0038] Along the direction from the first adhesive layer 2 toward the first conductive layer 4, the first adhesive layer 2 is sequentially divided into a first transition layer and a first bonding layer. The first transition layer is disposed at the surface pores of the porous substrate layer 1, and the first bonding layer is disposed between the porous substrate layer 1 and the first conductive layer 4.

[0039] It should be noted that in this utility model, the first transition layer is disposed at the surface pores of the porous substrate layer 1, which is intended to indicate that the first adhesive layer 2 is disposed on the surface of the porous substrate layer 1, and a portion of it will penetrate into the porous structure of the porous substrate layer 1, and this portion of the first adhesive layer 2 that has penetrated into it becomes the first transition layer; and the first transition layer is connected to the first adhesive layer.

[0040] Along the direction from the second adhesive layer 3 toward the second conductive layer 5, the second adhesive layer 3 is sequentially divided into a second transition layer and a second bonding layer. The second transition layer is disposed at the surface pores of the porous substrate layer 1, and the second bonding layer is disposed between the porous substrate layer 1 and the second conductive layer 5.

[0041] It should be noted that in this utility model, the second transition layer is disposed at the surface pores of the porous substrate layer 1, which is intended to indicate that the second adhesive layer 3 is disposed on the surface of the porous substrate layer 1, and a portion of it will penetrate into the porous structure of the porous substrate layer 1, and this portion of the second adhesive layer 3 that has penetrated into it becomes the second transition layer; and the second transition layer is connected to the second adhesive layer.

[0042] It should be noted that in this utility model, the first transition layer and the second transition layer are structures formed by the adhesive penetrating through the surface pores of the porous substrate layer 1 and filling the surface pores of the porous substrate layer 1. The penetrating forms include, but are not limited to, physical penetration (the first transition layer and the second transition layer flow into the pores on the surface of the porous substrate layer 1), chemical penetration (the first transition layer and the second transition layer form a chemical crosslink with the surface of the porous substrate layer 1), and pressure-driven penetration (the depth of the first transition layer and the second transition layer can be promoted and controlled by the pressure applied during the hot-press bonding process).

[0043] It should be noted that the depth characterization method of the first transition layer and the second transition layer in this utility model includes: the first method is that characteristic functional groups of the first transition layer and / or the second transition layer can be detected inside the substrate layer at a distance of 0.2 μm to 1 μm from the surface of the porous substrate layer 1; for example, the first transition layer and / or the second transition layer is maleic anhydride modified PP and cyanate ester curing agent, the porous substrate layer 1 is porous PET, and the characteristic infrared peak of maleic anhydride (infrared characteristic peak wavelength region 1700~1750 cm-1) can be detected inside the substrate at a distance of 0.35 μm from the surface of the porous substrate layer 1, so that the depth of the first transition layer and / or the second transition layer is determined to be 0.35 μm. The second method involves detecting characteristic elements of the first transition layer and / or the second transition layer inside the substrate layer at a distance of 0.2 μm to 1 μm from the surface of the porous substrate layer 1. For example, if the first transition layer and / or the second transition layer is polyurethane and epoxy curing agent, and the porous substrate layer 1 is porous PE (without oxygen (O) element), oxygen (O) element can be detected inside the substrate at a distance of 0.4 μm from the surface of the porous substrate layer 1, thus determining that the depth of the first transition layer and / or the second transition layer is 0.4 μm.

[0044] In some embodiments, the surface pore depth of the porous substrate layer 1 is 0.2 μm to 5 μm, the depth of the first transition layer at the surface pores of the porous substrate layer 1 is 0.05 μm to 2 μm, and the depth of the second transition layer at the surface pores of the porous substrate layer 1 is 0.05 μm to 2 μm.

[0045] It should be noted that the surface pore depth in this invention refers to the presence of certain pores on the surface of the porous substrate layer 1. This depth is the distance from the overall horizontal plane of the porous substrate layer 1 to the actual surface of the pore at the vertical angle, and can be characterized by atomic force microscopy (AFM). The surface pore depth of the porous substrate layer 1 is 0.2 μm to 5 μm because within this range, the adhesive layer can penetrate to the pores on the surface of the porous substrate layer 1, thereby enhancing the mechanical bonding between the adhesive layer and the porous substrate layer 1. A further preferred depth is 0.5 μm to 2 μm because this range is more conducive to balancing the physical properties of the composite current collector and its interlayer bonding strength, ensuring good mechanical properties of the composite current collector while improving the interlayer bonding strength.

[0046] It should be noted that the depth of the first transition layer at the pores on the surface of the porous substrate layer 1 in this utility model is 0.05μm~2μm, because this range is conducive to improving the bonding strength between the adhesive layer 2 and the porous substrate layer 1; it is even more preferable to be 0.2μm~1μm, which is more conducive to improving the bonding strength while avoiding stress concentration, that is, avoiding brittle fracture of the composite current collector.

[0047] It should be noted that the depth of the second transition layer at the pores on the surface of the porous substrate layer 1 in this utility model is 0.05μm~2μm, because this range is conducive to improving the bonding strength between the adhesive layer 2 and the porous substrate layer 1; it is even more preferable to be 0.2μm~1μm, which is more conducive to improving the bonding strength while avoiding stress concentration, that is, avoiding brittle fracture of the composite current collector.

[0048] It should be noted that, in this invention, the depth of the first transition layer at the pores on the surface of the porous substrate layer 1 is 10% to 90% of the surface pore depth of the porous substrate layer 1 itself. This percentage indicates that the contact area between the adhesive layer 2 and the porous substrate layer 1 is greater than the horizontal area, thereby improving the bonding strength between the adhesive layer 2 and the porous substrate layer 1. More preferably, it is 20% to 70%, because this helps to increase the contact area and improve the bonding strength while avoiding the concentration of internal stress at the pores, thus affecting the mechanical properties of the composite current collector. Similarly, the depth of the second transition layer at the pores on the surface of the porous substrate layer 1 is 10% to 90% of the surface pore depth of the porous substrate layer 1 itself. This percentage indicates that the contact area between the adhesive layer 2 and the porous substrate layer 1 is greater than the horizontal area, thereby improving the bonding strength between the adhesive layer 2 and the porous substrate layer 1. More preferably, it is 20% to 70%, because this helps to increase the contact area and improve the bonding strength while avoiding the concentration of internal stress at the pores, thus affecting the mechanical properties of the composite current collector.

[0049] In some embodiments, the surface porosity of the porous substrate layer 1 is 30° to 90°.

[0050] It should be noted that, in this invention, the surface porosity tortuosity refers to the presence of pores on and inside the porous substrate layer 1, and these pores are often not vertically distributed. The tortuosity here refers to the range of angles within which the surface pores bend. The surface porosity tortuosity of the porous substrate layer 1 is 30°~90° because within this range, the adhesive layer can effectively form a "barb" structure during penetration, thereby improving the mechanical bonding between the adhesive layer and the porous substrate layer 1. Further, 45°~75° is preferable because this range is more conducive to the probability of forming "barb" structures, thereby increasing the number of "barb" structures and further improving the mechanical bonding.

[0051] In some embodiments, the porosity of the porous substrate layer 1 is 30% to 95%, the average pore size of the porous substrate layer 1 is 0.01 μm to 1 μm, the thickness of the porous substrate layer 1 is 2 μm to 20 μm, and the tensile strength of the composite current collector is 100 MPa to 1000 MPa.

[0052] In this invention, the porous substrate layer 1 is a thin film with a porous structure, including one or two of the following: linear fibers or dumbbell-shaped rods made of porous PE, PP, PET or other non-metallic materials. The specific material selection of the porous substrate layer 1 is not specifically limited, and those skilled in the art can make appropriate selections according to the actual situation.

[0053] It should be noted that the porosity of the porous substrate layer 1 in this invention is 30% to 95%, because this range is conducive to the porous substrate layer 1 having sufficient porosity to expel air bubbles from the adhesive layer and absorb part of the adhesive layer; it is further preferred to be 40% to 90%, because this range is more conducive to the adhesive penetrating into the interior of the porous substrate layer 1 while taking into account the mechanical properties and reliability of the composite current collector.

[0054] It should be noted that the tensile strength of the composite current collector in this invention is 100MPa~1000MPa because the porous substrate layer 1 has sufficient strength within this range, thereby ensuring that the composite current collector has suitable flexibility.

[0055] In some embodiments, the thickness of the first adhesive layer is 0.1 μm to 2 μm, and the thickness of the second adhesive layer is 0.1 μm to 2 μm.

[0056] In this invention, the first adhesive layer is disposed between the first conductive layer 4 and the porous substrate layer 1, and its thickness is limited to 0.1μm~2μm. This is because if the first adhesive layer is too thin, the bonding strength between the layers will decrease, and stress concentration will occur, leading to brittle fracture of the composite current collector. If the first adhesive layer is too thick, delamination or pores will easily appear inside, affecting the bonding strength. The second adhesive layer is disposed between the second conductive layer 5 and the porous substrate layer 1, and its thickness is limited to 0.1μm~2μm. This is because if the second adhesive layer is too thin, the bonding strength between the layers will decrease, and stress concentration will occur, leading to brittle fracture of the composite current collector. If the second adhesive layer is too thick, delamination or pores will easily appear inside, affecting the bonding strength.

[0057] In this invention, the materials of the first adhesive layer 2 and the second adhesive layer 3 can be the same or different, and those skilled in the art can make an adaptive selection according to the actual situation. The material of the first adhesive layer 2 may include one or two of modified PE, modified PP, and polyurethane, and one or two of epoxy curing agents and cyanate ester curing agents. The combination of modified PE, modified PP, polyurethane with epoxy curing agents and cyanate ester curing agents can be selected by those skilled in the art according to their needs, and is not limited here. Similarly, the material of the second adhesive layer 3 may include one or two of modified PE, modified PP, and polyurethane, and one or two of epoxy curing agents and cyanate ester curing agents. The combination of modified PE, modified PP, polyurethane with epoxy curing agents and cyanate ester curing agents can be selected by those skilled in the art according to their needs, and is not limited here.

[0058] In some embodiments, the thickness of the first conductive layer 4 is 0.2 μm to 3 μm, and the thickness of the second conductive layer 5 is 0.2 μm to 3 μm.

[0059] In this invention, the thickness and material selection of the first conductive layer 4 and the second conductive layer 5 can be the same or different, and those skilled in the art can make adaptive selections according to actual conditions. The material of the first conductive layer 4 may include one or two of aluminum, nickel, copper, stainless steel, and conductive carbon materials; the material of the second conductive layer 5 may include one or two of aluminum, nickel, copper, stainless steel, and conductive carbon materials; the functions of the first conductive layer 4 and the second conductive layer 5 include collecting current and connecting the active materials of the battery.

[0060] For example, this utility model provides a method for preparing a composite current collector, namely, a vapor deposition → transfer method, specifically including:

[0061] (1) Preparation of porous substrate layer 1.

[0062] (2) A release agent is coated on the substrate surface to obtain a primary film.

[0063] (3) A conductive layer is deposited on the side of the substrate coated with release agent using a vacuum coating machine to obtain a pre-conductive layer.

[0064] (4) Apply adhesive to the aluminum surface of the pre-conductive layer and dry it to form an adhesive layer. Then, apply hot roller bonding to both sides of the porous substrate layer 1. The bonding pressure is 0.1~1MPa and the hot roller temperature is 50~120℃ to obtain the first semi-finished composite film.

[0065] (5) The first semi-finished composite film is placed in an oven for curing and hardening, so that the adhesive layer, porous substrate layer 1 and pre-made conductive layer are fully bonded. The oven temperature is 50℃~80℃ and the oven treatment time is 48h~120h to obtain the second semi-finished composite film.

[0066] (6) Use a peeling and slitting device to peel off the substrates on both sides of the second semi-finished composite film and cut them to obtain the finished composite current collector.

[0067] It should be noted that the release agent in this invention can be any one of silicon and silicon-based compounds, carbon and carbon-based compounds, boron nitride, molybdenum disulfide, tungsten disulfide, molybdenum diselenide, tungsten diselenide and MXene, or any combination containing at least two or more of them.

[0068] For example, this utility model also provides a method for preparing a composite current collector, namely, a conductive layer → bonding → corrosion thinning method, specifically including:

[0069] (1) Fabricate porous substrate layer 1.

[0070] (2) Apply adhesive to the surface of the conductive layer and dry it. Then, hot roll bonding is performed on both sides of the porous substrate layer 1. The bonding pressure is 0.1~1MPa and the hot roll temperature is 50~120℃ to obtain the first semi-finished composite film.

[0071] (3) Place the first semi-finished composite film in an oven for curing, wherein the oven temperature is 50℃~80℃ and the oven treatment time is 48h~120h. The second semi-finished composite film is obtained.

[0072] (4) The conductive layer of the second semi-finished composite film is placed in an acid solution or an alkaline solution for corrosion and thinning until it reaches the target thickness, and then cut to obtain the finished composite current collector.

[0073] It should be noted that the acidic solution in this invention can be selected from inorganic acids such as sulfuric acid and nitric acid, as well as organic acids such as oxalic acid and acetic acid, and combinations thereof. The alkaline solution can be selected from strong bases such as sodium hydroxide and sodium carbonate, other alkaline reducing agents such as ferric chloride, and any combination thereof.

[0074] The above-mentioned methods for preparing composite current collectors—evaporation deposition → transfer method and conductive layer → bonding → corrosion thinning method—can be adapted by those skilled in the art according to actual needs, and are not specifically limited here.

[0075] It should be noted that the working mechanism of the composite current collector in this utility model is that the pores in the porous substrate layer 1 act as "micro-clamps" to lock the adhesive layer. This mechanical riveting structure can effectively improve the bonding force between the adhesive layer and the substrate layer. The adhesive used in the adhesive layer penetrates into the pores of the substrate to form a barbed structure, which also improves the bonding force between the adhesive layer and the substrate layer. The porous surface of the porous substrate layer 1 increases the effective bonding area, thereby improving the bonding force between the adhesive layer and the substrate layer.

[0076] Example 1

[0077] This embodiment provides a composite current collector prepared using a vapor deposition → transfer method, such as... Figure 2 As shown, where:

[0078] It includes a porous PE layer 6, a first adhesive layer 2, a second adhesive layer 3, a first aluminum layer 7, and a second aluminum layer 8; the first adhesive layer 2 and the first aluminum layer 7 are sequentially disposed on one side surface of the porous PE layer 6, and the second adhesive layer 3 and the second aluminum layer 8 are sequentially disposed on the other side surface of the porous PE layer 6.

[0079] Along the direction from the first adhesive layer 2 toward the first aluminum layer 7, the first adhesive layer 2 is sequentially divided into a first transition layer and a first bonding layer. The first transition layer is disposed at the surface pores of the porous PE layer 6, and the first bonding layer is disposed between the porous PE layer 6 and the first aluminum layer 7.

[0080] Along the direction from the second adhesive layer 3 toward the second aluminum layer 8, the second adhesive layer 3 is sequentially divided into a second transition layer and a second bonding layer. The second transition layer is disposed at the surface pores of the porous PE layer 6, and the second bonding layer is disposed between the porous PE layer 6 and the second aluminum layer 8.

[0081] The surface pore depth of the porous PE layer 6 is 0.7 μm, the depth of the first transition layer at the surface pores of the porous PE layer 6 is 0.2 μm, and the depth of the second transition layer at the surface pores of the porous PE layer 6 is 0.2 μm.

[0082] The surface pore tortuosity of the porous PE layer 6 is 45°, the porosity of the porous PE layer 6 is 36.5%, the average pore diameter of the porous PE layer 6 is 75 nm, the thickness of the porous PE layer 6 is 7 μm, and the tensile strength of the composite current collector is 240 MPa.

[0083] The thickness of the first adhesive layer is 0.6 μm, and the thickness of the second adhesive layer is 0.6 μm. The thickness of the first aluminum layer 7 is 1 μm, and the thickness of the second aluminum layer 8 is 1 μm.

[0084] Example 2

[0085] The difference from Example 1 is:

[0086] The surface pore depth of the porous PE layer 6 is 1.12 μm, the depth of the first transition layer at the surface pores of the porous PE layer 6 is 0.31 μm, and the depth of the second transition layer at the surface pores of the porous PE layer 6 is 0.31 μm.

[0087] The surface pore tortuosity of the porous PE layer 6 is 50°, the porosity of the porous PE layer 6 is 42.1%, the average pore diameter of the porous PE layer 6 is 82 nm, the thickness of the porous PE layer 6 is 10 μm, and the tensile strength of the composite current collector is 190 MPa.

[0088] The thickness of the first aluminum layer 7 is 1.5 μm, and the thickness of the second aluminum layer 8 is 1.5 μm.

[0089] Example 3

[0090] The difference from Example 1 is:

[0091] It includes a porous PP layer, a first adhesive layer 2, a second adhesive layer 3, a first aluminum layer 7, and a second aluminum layer 8; the first adhesive layer 2 and the first aluminum layer 7 are sequentially disposed on one side surface of the porous PP layer, and the second adhesive layer 3 and the second aluminum layer 8 are sequentially disposed on the other side surface of the porous PP layer.

[0092] The surface pore depth of the porous PP layer is 1.5 μm, the depth of the first transition layer at the surface pores of the porous PP layer is 0.37 μm, and the depth of the second transition layer at the surface pores of the porous PP layer is 0.37 μm.

[0093] The surface pore tortuosity of the porous PP layer is 43°, the porosity of the porous PP layer is 60.5%, the average pore size of the porous PP layer is 95nm, the thickness of the porous PP layer is 16μm, and the tensile strength of the composite current collector is 160MPa.

[0094] The thickness of the first aluminum layer 7 is 1.5 μm, and the thickness of the second aluminum layer 8 is 1.5 μm.

[0095] Example 4

[0096] The difference from Example 1 is:

[0097] It includes a porous PET layer, a first adhesive layer 2, a second adhesive layer 3, a first aluminum layer 7, and a second aluminum layer 8; the first adhesive layer 2 and the first aluminum layer 7 are sequentially disposed on one side surface of the porous PET layer, and the second adhesive layer 3 and the second aluminum layer 8 are sequentially disposed on the other side surface of the porous PET layer.

[0098] The surface pore depth of the porous PET layer is 0.45 μm, the depth of the first transition layer at the surface pores of the porous PET layer is 0.09 μm, and the depth of the second transition layer at the surface pores of the porous PET layer is 0.09 μm.

[0099] The porosity of the porous PET layer is 30.5%, the average pore size of the porous PET layer is 89 nm, the thickness of the porous PET layer is 6 μm, and the tensile strength of the composite current collector is 110 MPa.

[0100] Example 5

[0101] The difference from Example 1 is:

[0102] It includes a porous PP layer, a first adhesive layer 2, a second adhesive layer 3, a first aluminum layer 7, and a second aluminum layer 8; the first adhesive layer 2 and the first aluminum layer 7 are sequentially disposed on one side surface of the porous PP layer, and the second adhesive layer 3 and the second aluminum layer 8 are sequentially disposed on the other side surface of the porous PP layer.

[0103] The surface pore depth of the porous PP layer is 1.25 μm, the depth of the first transition layer at the surface pores of the porous PP layer is 0.19 μm, and the depth of the second transition layer at the surface pores of the porous PP layer is 0.19 μm.

[0104] The porosity of the porous PP layer is 53.45%, the average pore size of the porous PP layer is 89 nm, the thickness of the porous PP layer is 7 μm, and the tensile strength of the composite current collector is 220 MPa.

[0105] The thickness of the first adhesive layer is 0.8 μm, the thickness of the second adhesive layer is 0.8 μm; the thickness of the first aluminum layer 7 is 1.5 μm, and the thickness of the second aluminum layer 8 is 1.5 μm.

[0106] Example 6

[0107] The difference from Example 1 is:

[0108] The surface pore depth of the porous PE layer is 0.32 μm, the depth of the first transition layer at the surface pores of the porous PE layer is 0.025 μm, and the depth of the second transition layer at the surface pores of the porous PE layer is 0.025 μm.

[0109] The porosity of the porous PE layer is 18.9%, the average pore size of the porous PE layer is 50 nm, and the thickness of the porous PE layer is 2.8 μm.

[0110] The thickness of the first adhesive layer is 0.8 μm, and the thickness of the second adhesive layer is 0.8 μm. The thickness of the first aluminum layer 7 is 1.5 μm, and the thickness of the second aluminum layer 8 is 1.5 μm.

[0111] Example 7

[0112] The difference from Example 1 is:

[0113] The surface pore depth of the porous PE layer is 0.7 μm, the depth of the first transition layer at the surface pores of the porous PE layer is 0.68 μm, and the depth of the second transition layer at the surface pores of the porous PE layer is 0.68 μm.

[0114] The porosity of the porous PE layer is 36.8%, and the tensile strength of the composite current collector is 130 MPa.

[0115] Example 8

[0116] The difference from Example 1 is:

[0117] The surface pore depth of the porous PE layer is 2.1 μm, the depth of the first transition layer at the surface pores of the porous PE layer is 0.68 μm, and the depth of the second transition layer at the surface pores of the porous PE layer is 0.68 μm.

[0118] The tensile strength of the composite current collector is 100 MPa.

[0119] Example 9

[0120] The difference from Example 1 is:

[0121] Composite current collector prepared by aluminum foil → bonding → etching thinning method;

[0122] It includes a porous PP layer, a first adhesive layer 2, a second adhesive layer 3, a first aluminum layer 7, and a second aluminum layer 8; the first adhesive layer 2 and the first aluminum layer 7 are sequentially disposed on one side surface of the porous PP layer, and the second adhesive layer 3 and the second aluminum layer 8 are sequentially disposed on the other side surface of the porous PP layer.

[0123] The surface pore depth of the porous PP layer is 1.15 μm, the depth of the first transition layer at the surface pores of the porous PE layer is 0.18 μm, and the depth of the second transition layer at the surface pores of the porous PE layer is 0.18 μm.

[0124] The porosity of the porous PP layer is 53.45%, the average pore size of the porous PP layer is 89 nm, the thickness of the porous PP layer is 7 μm, and the tensile strength of the composite current collector is 210 MPa.

[0125] The thickness of the first adhesive layer is 0.8 μm, the thickness of the second adhesive layer is 0.8 μm; the thickness of the first aluminum layer 7 is 1.5 μm, and the thickness of the second aluminum layer 8 is 1.5 μm.

[0126] Example 10

[0127] The difference from Example 1 is:

[0128] Composite current collector prepared by aluminum foil → bonding → etching thinning method;

[0129] The surface pore depth of the porous PE layer is 0.7 μm, the depth of the first transition layer at the surface pores of the porous PE layer is 0.25 μm, and the depth of the second transition layer at the surface pores of the porous PE layer is 0.25 μm.

[0130] The porosity of the porous PE layer is 36.5%, the average pore size of the porous PE layer is 75 nm, the thickness of the porous PE layer is 7 μm, and the tensile strength of the composite current collector is 170 MPa.

[0131] The thickness of the first adhesive layer is 0.8 μm, and the thickness of the second adhesive layer is 0.8 μm. The thickness of the first aluminum layer 7 is 1.5 μm, and the thickness of the second aluminum layer 8 is 1.5 μm.

[0132] Comparative Example 1

[0133] The difference from Example 1 is:

[0134] The composite current collector is made of aluminum foil with a thickness of 12μm and a tensile strength of 190MPa. It does not have a first adhesive layer 2, a second adhesive layer 3, a first aluminum layer 7, or a second aluminum layer 8, and it does not require the vapor deposition → transfer method for preparation.

[0135] Comparative Example 2

[0136] The difference from Example 1 is:

[0137] It includes a PET layer, a first adhesive layer 2, a second adhesive layer 3, a first aluminum layer 7, and a second aluminum layer 8; the first adhesive layer 2 and the first aluminum layer 7 are sequentially disposed on one side surface of the PET layer, and the second adhesive layer 3 and the second aluminum layer 8 are sequentially disposed on the other side surface of the PET layer.

[0138] The overall thickness of the composite current collector is 82 μm, and the tensile strength is 130 MPa.

[0139] Specifically, the specific parameters of the composite current collectors in Examples 1-10 and Comparative Examples 1-2 are shown in Tables 1 and 2.

[0140]

[0141]

[0142] In Tables 1 and 2 above, the porosity test method for porous substrate layer 1 is the weighing method, and the operation procedure is as follows: 1) Sample preparation: Cut a membrane sample of regular size (e.g., 10cm × 10cm), weigh its dry weight using an analytical balance with an accuracy of 0.1mg, and record it as m1. 2) Liquid immersion: Immerse the sample completely in a liquid with low surface tension, easy wetting, and no reaction with the membrane (e.g., anhydrous ethanol, n-butanol) for 10-30 minutes to ensure that the liquid fully fills the pores. 3) Surface dehydration: Remove the sample, gently blot off excess liquid on the surface with filter paper (avoid squeezing the sample to prevent liquid loss from the pores), and immediately weigh its wet weight, and record it as m2. 4) Calculation of porosity: Calculate the porosity P(%) according to the formula: Porosity P(%) = [(m2 - m1) / (ρ×V)]×100%. Where ρ is the density of the soaking liquid (known, such as 0.789 g / cm³ for ethanol), and V is the volume of the diaphragm sample (calculated from sample length × width × thickness).

[0143] The pore size of the porous substrate layer 1 can be measured using a capillary flow porosimeter. The specific steps are as follows: 1) Completely wet and fill the pores of the diaphragm to be measured with liquid, creating positive pressure inside the pores due to capillary action; 2) Place the diaphragm in a sealed tank and use gas pressure to force the liquid out of the capillary channels; 3) Based on the relative relationship between the pressure applied when the liquid in a single channel is completely squeezed out of the capillary channel and the channel diameter, the pore size of the diaphragm can be obtained according to the Laplace equation. The Laplace equation is as follows: d = -(4γcosθ) / ⊿P. Where d is the pore diameter, ⊿P is the pressure, γ is the liquid surface tension, and θ is the contact angle between the diaphragm and the liquid. Under different pressures, the liquid in the diaphragm will be successively squeezed out, generating a certain gas permeation flow rate. The pore size and pore size distribution can be calculated based on the relationship between pressure and flow rate changes.

[0144] The surface pore depth of the porous substrate layer 1 can be characterized using atomic force microscopy (AFM) with the Bruker Dimenson ICON instrument. The sample surface morphology and height are characterized using a 1cm*1cm sample size and a single scan range of 50μm*50μm. Three regions are randomly scanned. The height difference between the height at the pores and the average height of the surface of the porous substrate layer 1 is taken as the surface pore depth, and multiple measurements are taken to obtain the average value.

[0145] The depth of the transition layer can be measured using XPS. A Thermo ESCALAB 250XI is selected as the testing equipment. A 5mm x 5mm sample is placed inside the device, and X-rays are used to irradiate the sample, exciting the inner-shell electrons or valence electrons of atoms or molecules. Electrons excited by photons are called photoelectrons, and their energy and quantity can be measured to obtain the composition of the analyte. Etching tests using this method can observe the distribution depth of characteristic elements of the binder in the composite current collector. The distance of this depth from the surface of the porous substrate layer 1 is the depth of the transition layer.

[0146] The tensile strength of the composite current collector can be measured using a universal metal testing machine according to the national standard GB / T 1040.1-2025. The sample to be tested is made into a strip with a width of 15 mm, the tensile spacing is fixed at 50 mm, and the tensile speed is 50 mm / min. The peel force test is performed according to the national standard GB / T 2792-1998, with a sample width of 15 mm and a peel speed of 100 mm / min.

[0147] Electrolyte corrosion resistance test of composite current collector: The composite current collector to be tested was cut into strips with a width of 25mm and a length of 10cm, and immersed in a lithium salt electrolyte containing 1000PPM water at 85℃ for 72 hours. After immersion, it was taken out and rinsed with DMC solution to remove residual electrolyte and dried. Then, the area of ​​the conductive layer peeling off was directly observed and measured using a two-dimensional instrument. If the peeling area ratio is <3%, the electrolyte corrosion resistance is good.

[0148] In Table 2 above, the peel force of the composite current collector refers to the bonding strength between the conductive layer and the adhesive layer, and the electrolyte corrosion resistance of the composite current collector refers to the percentage of the area where the conductive layer peels off in a point-like or sheet-like manner in an electrolyte immersion environment. The smaller the percentage, the better the electrolyte corrosion resistance.

[0149] Examples 1 to 10 all use a porous substrate layer 1. In particular, Example 3 has a higher surface pore depth, allowing more adhesive layer to penetrate into the interior of the porous substrate layer 1. This forms a "barb" structure with the pores of the porous substrate layer 1, thereby locking the adhesive layer in place. This significantly improves the peel strength. Furthermore, during the penetration process, air bubble defects that were originally located in the adhesive layer are also discharged from the pores of the porous substrate layer 1, resulting in no air bubble defects inside. This also provides excellent resistance to electrolyte corrosion.

[0150] A comparison of Examples 4 and 6 with Examples 1-3, 5, 9, and 10 revealed that the surface pore depth and transition layer depth of the porous substrate layer 1 are relatively small, resulting in a reduced degree of mechanical bonding, manifested as lower peel strength and poorer resistance to electrolyte corrosion in the composite current collector. Therefore, the surface pore depth and transition layer depth of the porous substrate layer 1 need to be kept within the limits defined in this application.

[0151] Comparing Example 7 with Example 1, it was found that although the excessive depth of the transition layer increases the degree of mechanical riveting, resulting in good peel force and electrolyte corrosion resistance of the composite current collector, it also leads to stress concentration in the substrate layer due to the excessive depth of the transition layer. This results in the composite current collector being prone to fracture, with lower fracture elongation and tensile strength. The difference in fracture elongation was not reflected in Example 7.

[0152] For Example 8, due to its high surface pore depth, the adhesive penetrates to a specified depth, but there are still a large number of vertical pores. These pores are prone to pitting corrosion due to electrolyte accumulation. Therefore, the composite current collector exhibits pitting corrosion in the electrolyte corrosion resistance test, with a corrosion area of ​​≈5%. Furthermore, due to the high surface pore depth, there is a stress concentration problem during the tensile process, resulting in low tensile strength.

[0153] For Examples 5 and 10, due to their high porosity, the number of surface pores is high. Although the transition layer depth is lower than the preferred value, the number of surface pores is high, and the number of adhesive penetration pores compensates for the lack of adhesive penetration depth, resulting in good peeling force. However, due to the low adhesive penetration depth, the resistance to electrolyte corrosion is good, and the proportion of electrolyte immersion corrosion area is <5%.

[0154] A comparison of Examples 3 with Examples 5 and 7 revealed that a higher porosity in the porous substrate layer 1 leads to a decrease in its mechanical strength. Therefore, the porosity of the porous substrate layer 1 needs to be kept within the range defined in this application.

[0155] The above description is only a specific embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present utility model fall within the protection and disclosure scope of the present utility model.

Claims

1. A composite current collector, characterized in that, The composite current collector includes a porous substrate layer, a first adhesive layer, a second adhesive layer, a first conductive layer, and a second conductive layer; The first adhesive layer and the first conductive layer are sequentially disposed on one side surface of the porous substrate layer, and the second adhesive layer and the second conductive layer are sequentially disposed on the other side surface of the porous substrate layer. Along the direction from the first adhesive layer toward the first conductive layer, the first adhesive layer is sequentially divided into a first transition layer and a first bonding layer. The first transition layer is disposed at the surface pores of the porous substrate layer, and the first bonding layer is disposed between the porous substrate layer and the first conductive layer. Along the direction from the second adhesive layer toward the second conductive layer, the second adhesive layer is sequentially divided into a second transition layer and a second bonding layer. The second transition layer is disposed at the surface pores of the porous substrate layer, and the second bonding layer is disposed between the porous substrate layer and the second conductive layer.

2. The composite current collector according to claim 1, characterized in that, The surface pore depth of the porous substrate layer is 0.2μm~5μm.

3. The composite current collector according to claim 1 or 2, characterized in that, The first transition layer is disposed at a depth of 0.05 μm to 2 μm in the pores on the surface of the porous substrate layer.

4. The composite current collector according to claim 1 or 2, characterized in that, The second transition layer is disposed at a depth of 0.05 μm to 2 μm in the pores on the surface of the porous substrate layer.

5. The composite current collector according to claim 1, characterized in that, The surface porosity of the porous substrate layer is 30°~90°.

6. The composite current collector according to claim 1, characterized in that, The porosity of the porous substrate layer is 30%~95%; The average pore size of the porous substrate layer is 0.01 μm to 1 μm.

7. The composite current collector according to claim 1, characterized in that, The thickness of the porous substrate layer is 2μm~20μm; The tensile strength of the composite current collector is 100MPa~1000MPa.

8. The composite current collector according to claim 1, characterized in that, The thickness of the first adhesive layer is 0.1 μm to 2 μm; The thickness of the second adhesive layer is 0.1μm to 2μm.

9. The composite current collector according to claim 1, characterized in that, The thickness of the first conductive layer is 0.2 μm to 3 μm; The thickness of the second conductive layer is 0.2μm to 3μm.

10. An electrochemical device, characterized in that, The electrochemical device includes a positive electrode and a negative electrode; Wherein, at least one of the positive electrode or the negative electrode adopts the composite current collector as described in any one of claims 1-9.

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