Composite current collector and preparation method and application thereof

Abstract

The invention relates to the technical field of battery materials, and discloses a composite current collector and a preparation method and application thereof. The composite current collector comprises a first metal layer, a first transition layer, a polymer film base layer, a second transition layer and a second metal layer which are sequentially arranged from top to bottom, the surfaces of the two sides of the polymer film base layer are provided with micro-concave structures. The micro-concave structures are rhombic pits; the first transition layer and the second transition layer are made of metal oxides independently, and the surfaces of the two sides of the first transition layer and the second transition layer are provided with nanometer protruding structures; the height of the nano convex structure is 20 to 50 nm; the first metal layer and the second metal layer are made of metal conductive materials independently. The composite current collector provided by the invention has the characteristics of high interface bonding force and high conductivity.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a composite current collector, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy and electronic technology, battery cycle life, safety performance, and energy density have become paramount. As a crucial component of the battery, the current collector gathers the current generated by the battery's active materials to form a larger output current; its performance directly impacts the battery's cycle life, energy density, and safety.

[0003] Traditional battery current collectors (such as copper foil and aluminum foil) have the following problems: 1. Insufficient mechanical strength: Metal foil is prone to breakage or pulverization during cycling, leading to a decline in battery performance; 2. Weak interfacial bonding: The active material and the current collector are prone to peeling due to the difference in thermal expansion coefficients, affecting conductivity and cycle life; 3. Thickness and cost limitations: The thickness of metal foil is usually 5-20μm, which increases the weight and cost of the battery.

[0004] Composite current collectors are functional thin films made by combining multiple layers of materials, typically using "metals" polymer materials The structure of "metal" uses a polymer material as the middle layer and metal layers (such as copper and aluminum) on both sides. It is mainly used to replace traditional metal foil as positive and negative electrode current collectors.

[0005] CN118645632A discloses a composite current collector, its preparation method, and a battery. It solves the above problems by depositing a metal transition layer on the surface of a polymer film. However, it does not involve the synergistic design of micro-concave structures and nanoscale protrusions, nor does it optimize the deposition parameters and annealing process of the transition layer, resulting in unsatisfactory interfacial bonding and conductivity. Summary of the Invention

[0006] The purpose of this invention is to provide a composite current collector with high interfacial bonding strength and high conductivity.

[0007] To achieve the above objectives, the first aspect of the present invention provides a composite current collector, which includes a first metal layer, a first transition layer, a polymer film base layer, a second transition layer, and a second metal layer disposed sequentially from top to bottom. The polymer film substrate has micro-concave structures on both sides; the micro-concave structures are rhomboid pits. The first transition layer and the second transition layer are each made of metal oxide, and both sides have nano-protrusion structures; the height of the nano-protrusion structures is 20-50 nm. The first metal layer and the second metal layer are each made of an independently conductive metallic material.

[0008] A second aspect of the present invention provides a method for preparing a composite current collector as described in the first aspect, the method comprising: (1) In the presence of oxygen-containing gas, a polymer film with diamond-shaped perforations covering both sides of the polymer film is formed on the surface of the polymer film by plasma etching process to form a micro-concave structure, and the metal foil is removed to obtain polymer film base layer I; (2) A first transition layer and a first metal layer are sequentially deposited on the upper surface of the polymer film substrate I by magnetron sputtering, and a second transition layer and a second metal layer are sequentially deposited on the lower surface of the polymer film substrate I to obtain a current collector semi-finished product; the vacuum degree of the magnetron sputtering process is 0.001-0.1 Pa; (3) The current collector semi-finished product is annealed in the presence of an inert gas to obtain a composite current collector; the annealing temperature is 80-150℃.

[0009] The third aspect of this invention provides the application of the composite current collector described in the first aspect in energy storage devices.

[0010] The composite current collector provided by this invention has high interfacial bonding force, mechanical strength and conductivity. When applied to lithium-ion batteries, sodium-ion batteries or supercapacitors, it can improve the energy density, cycle stability and lithium-ion transport efficiency of the battery. Attached Figure Description

[0011] Figure 1 This is a top view schematic diagram of the upper surface of a polymer film substrate for an optional composite current collector according to the present invention. Detailed Implementation

[0012] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0013] As mentioned above, a first aspect of the present invention provides a composite current collector, which includes a first metal layer, a first transition layer, a polymer film base layer, a second transition layer, and a second metal layer disposed sequentially from top to bottom. The polymer film substrate has micro-concave structures on both sides; the micro-concave structures are rhomboid pits. The first transition layer and the second transition layer are each made of metal oxide, and both sides have nano-protrusion structures; the height of the nano-protrusion structures is 20-50 nm. The first metal layer and the second metal layer are each made of an independently conductive metallic material.

[0014] The micro-concave structure with rhomboid pits in this invention can improve the adhesion between the transition layer and the substrate, laying the foundation for improving the peel strength of the composite current collector. Furthermore, the nano-protrusion structure with specific height and spacing can provide anchor points for metal deposition. The structure containing the aforementioned technical features can increase the contact area. Combined with the chemical bonding effect of the transition layer, it can significantly improve the interfacial bonding force of the composite current collector. At the same time, the synergistic design of the metal layer and the transition layer can reduce the interfacial resistance and improve the electron transport efficiency.

[0015] In a preferred embodiment, the composite current collector further includes, from top to bottom, a first conductive layer, a first metal layer, a first transition layer, a polymer film base layer, a second transition layer, a second metal layer, and a second conductive layer.

[0016] Preferably, the materials of the first conductive layer and the second conductive layer are each independently selected from at least one of thin-layer graphite, carbon black, graphene, and carbon nanotubes.

[0017] In a preferred embodiment, the depth of the micro-concave structure is 0.1-0.5 μm, the width is 0.5-5 mm, and the spacing between adjacent micro-concave structures is 1-20 mm.

[0018] The present invention does not have any special requirements on the internal shape of the micro-concave structure. The micro-concave structure can be vertical, inclined, or curved.

[0019] In this invention, the depth of the micro-concave structure refers to the distance from the lowest point of the concave pit to the plane of the polymer film substrate; the width of the micro-concave structure refers to the length of the shortest diagonal of the rhomboid concave pit, and the length of the micro-concave structure refers to the length of the longest diagonal; the spacing between adjacent micro-concave structures refers to the distance between the rightmost end of one micro-concave structure and the leftmost end of the adjacent micro-concave structure along the length direction of the micro-concave structure. The rhomboid concave pit described in this invention includes square concave pits.

[0020] In a preferred embodiment, the area of ​​the rhomboid recess is 0.2-25 mm. 2 Under these preferred conditions, the inventors discovered that the prepared composite current collector exhibits superior peel strength.

[0021] Preferably, the micro-concave structures are arranged in a parallel, staggered pattern. Under this preferred condition, the inventors found that the prepared composite current collector has a higher yield and better peel strength.

[0022] In this invention, the arrangement of the micro-concave structures along their length is considered a row, and the parallel staggered distribution means that the micro-concave structures in each row are interlaced. This invention exemplarily provides a top view of the upper surface of the polymer film substrate of the composite current collector, as shown below. Figure 1 As shown.

[0023] In this invention, the adjacent nanoprotrusion structures can be uniformly distributed or non-uniformly distributed, as long as the spacing is between 50-500 nm. The spacing refers to the distance between the tops of two adjacent nanoprotrusion structures. This will not be described in detail here, and those skilled in the art should not understand it as a limitation of this invention.

[0024] In a preferred embodiment, the polymer film base layer is made of at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide.

[0025] Preferably, the metal oxide is selected from at least one of aluminum oxide, titanium oxide, and zirconium oxide.

[0026] Preferably, the conductive metallic material is selected from at least one of copper, aluminum, nickel, silver, and gold.

[0027] According to a preferred embodiment, the composite current collector is used as a positive electrode current collector for a lithium-ion battery, and both the first metal layer and the second metal layer are made of aluminum.

[0028] According to another preferred embodiment, the composite current collector is used as a negative electrode current collector for a lithium-ion battery, and both the first metal layer and the second metal layer are made of copper.

[0029] According to a preferred embodiment, the thickness of the polymer film substrate is 18-30 times the depth of the micro-recessed structure, the thickness of the first metal layer and the second metal layer are each independently 0.5-2 μm, and the thickness of the first transition layer and the second transition layer are each independently 30-200 nm. Under this preferred condition, the inventors found that the thickness ratio of the polymer film substrate to the metal layer optimizes the overall strength and weight balance.

[0030] According to another preferred embodiment, the thickness of the first conductive layer and the second conductive layer are each independently 0.2-2 μm.

[0031] As previously described, a second aspect of the present invention provides a method for preparing a composite current collector as described in the first aspect, the method comprising: (1) In the presence of oxygen-containing gas, a polymer film with diamond-shaped perforations covering both sides of the polymer film is formed on the surface of the polymer film by plasma etching process to form a micro-concave structure, and the metal foil is removed to obtain polymer film base layer I; (2) A first transition layer and a first metal layer are sequentially deposited on the upper surface of the polymer film substrate I by magnetron sputtering, and a second transition layer and a second metal layer are sequentially deposited on the lower surface of the polymer film substrate I to obtain a current collector semi-finished product; the vacuum degree of the magnetron sputtering process is 0.001-0.1 Pa; (3) The current collector semi-finished product is annealed in the presence of an inert gas to obtain a composite current collector; the annealing temperature is 80-150℃.

[0032] In a preferred embodiment, the method further includes: coating the upper and lower surfaces of the intermediate product obtained by the annealing treatment with a first conductive layer and a second conductive layer, respectively, to obtain a composite current collector.

[0033] In this invention, the diamond-shaped perforation of the metal foil can be customized according to the distribution, area, width and spacing of the micro-concave structures and adjacent micro-concave structures.

[0034] In this invention, the composite current collector can be a positive electrode composite current collector, a negative electrode composite current collector, or a bipolar composite current collector.

[0035] According to a preferred embodiment, in step (1), the operating conditions of the plasma etching process include: radio frequency power of 100-300W, gas pressure of 0.5-2Pa, and time of 5-15min.

[0036] This invention does not impose any special requirements on the instruments used in the plasma etching process; those skilled in the art can select the appropriate instruments based on known techniques. For example, an radio frequency plasma etching machine is used.

[0037] Preferably, the oxygen-containing gas is a mixture of argon and oxygen. Under this preferred condition, the inventors found that the prepared composite current collector exhibits minimal substrate damage and avoids unexpected reactions.

[0038] More preferably, the volume ratio of argon to oxygen is 3-15:1.

[0039] According to a preferred embodiment, in step (2), the operating conditions of the magnetron sputtering process include: sputtering power of 200-500W, gas pressure of 0.2-1Pa, temperature of 25-130℃, and deposition rate of 5-20nm / min.

[0040] In this invention, the operating conditions for magnetron sputtering of the first transition layer, the second transition layer, the first metal layer, and the second metal layer can be the same or different, as long as they meet the operating condition range of the magnetron sputtering process. This invention will not be described in detail here, and those skilled in the art should not understand it as a limitation of this invention.

[0041] This invention does not impose any special requirements on the instruments used in the magnetron sputtering process; those skilled in the art can select the appropriate instruments based on known techniques. For example, a DC magnetron sputtering instrument is used; however, this will not be described in detail here, and should not be construed as a limitation of the invention.

[0042] Preferably, the sputtering power for depositing the first and second transition layers is 50-100 W lower than the sputtering power for depositing the first and second metal layers. The inventors have found that under these preferred conditions, the prepared composite current collector can achieve a more uniform surface structure.

[0043] Preferably, in step (3), the inert gas is nitrogen and / or argon.

[0044] Preferably, the annealing conditions include: a heating rate of 5-10℃ / min and a holding time of 0.5-4h.

[0045] As previously stated, the third aspect of the present invention provides the application of the composite current collector described in the first aspect in energy storage devices.

[0046] Preferably, the energy storage device includes: a lithium-ion battery, a sodium-ion battery, and a supercapacitor.

[0047] In a preferred embodiment, the application includes: combining the composite current collector with an electrode active material layer to form an electrode for a battery or supercapacitor.

[0048] The present invention will be described in detail below through examples. Unless otherwise specified, specific experimental steps or conditions in the following examples can be performed according to known experimental steps or conditions described in the literature in this field. Unless otherwise specified, the raw materials or instruments used are commercially available. Unless otherwise specified, the reaction temperature in the following examples is at room temperature, which refers to 25±2℃.

[0049] Polymer film I: Polyimide (PI) film, with dimensions of 100mm × 100mm; Polymer Film II: Polyethylene (PE) film, 100mm × 100mm in size; Polymer Film III: Polyethylene terephthalate (PET) film, with a size of 100mm × 100mm.

[0050] Metal foil I: The diamond-shaped cutouts are arranged in parallel and interlaced patterns, with an area of ​​5 mm². 2 The width is 1.5mm, and the spacing between adjacent diamond-shaped cutouts is 2mm; Metal Foil II: The diamond-shaped cutouts are arranged in parallel and interlaced patterns, with an area of ​​20 mm². 2 The width is 2mm, and the spacing between adjacent diamond-shaped cutouts is 5mm; Metal Foil III: The diamond-shaped perforations are arranged in parallel and interlaced patterns, with an area of ​​2 mm. 2 The width is 1mm, and the spacing between adjacent diamond-shaped cutouts is 20mm; Metal foil IV: The diamond-shaped cutouts are arranged in parallel alignment, with an area of ​​5 mm². 2 The width is 1.5mm, and the spacing between adjacent diamond-shaped cutouts is 2mm.

[0051] Example 1 (1) The polymer film I with metal foil I containing diamond-shaped perforations on both sides is placed in an RF plasma etching machine, and a mixture of argon and oxygen with a volume ratio of 4:1 is introduced to form a micro-concave structure on the surface of the polymer film I. The metal foil I is removed to obtain the polymer film base layer I. Operating conditions for the radio frequency plasma etching machine: radio frequency power of 200W, gas pressure of 1Pa, and time of 10min; The micro-concave structure consists of rhomboid pits arranged in parallel and staggered patterns, with an area of ​​5 mm². 2 The depth is 0.3 μm, the width is 1.5 mm, and the spacing between adjacent micro-concave structures is 2 mm; The thickness of polymer film base layer I is 30 times the depth of the micro-recessed structure; (2) A first transition layer and a first metal layer are sequentially deposited on the upper surface of the polymer film substrate I using a DC magnetron sputtering instrument, and a second transition layer and a second metal layer are sequentially deposited on the lower surface of the polymer film substrate I to obtain a current collector semi-finished product; The first and second transition layers have the same material and thickness, both being aluminum oxide with a thickness of 100 nm. The first metal layer and the second metal layer have the same material and thickness, both being aluminum with a thickness of 1.5μm; Operating conditions for the DC magnetron sputtering instrument for the first and second transition layers: vacuum level 0.001 Pa, sputtering power 300 W, gas pressure 0.5 Pa, temperature 100 °C, deposition rate 10 nm / min; Operating conditions for the DC magnetron sputtering instrument for the first and second metal layers: vacuum level 0.001 Pa, sputtering power 400 W, gas pressure 0.5 Pa, temperature 100 °C, deposition rate 15 nm / min; The first and second transition layers have nano-protrusion structures on both sides, with a height of 50 nm. (3) Anneal the current collector semi-finished product in the presence of nitrogen and cool it naturally to room temperature to obtain the positive electrode composite current collector; Annealing conditions: temperature 120℃, heating rate 5℃ / min, holding time 2h.

[0052] Example 2 The same method as in Example 1 was used, except that metal foil I in step (1) was replaced with metal foil II, and the time of the radio frequency plasma etching machine was adjusted to 7 min. The remaining steps and conditions were the same, and a positive electrode composite current collector was obtained. The micro-concave structure consists of rhomboid pits arranged in parallel and staggered patterns, with an area of ​​20 mm². 2 The depth is 0.1 μm, the width is 2 mm, and the spacing between adjacent micro-concave structures is 5 mm.

[0053] Example 3 The same method as in Example 1 was used, except that metal foil I in step (1) was replaced with metal foil III, and the time of the radio frequency plasma etching machine was adjusted to 13 min. The remaining steps and conditions were the same, and a positive electrode composite current collector was obtained. The micro-concave structure consists of rhomboid pits arranged in parallel and staggered patterns, with an area of ​​2 mm. 2 The depth is 0.5μm, the width is 1mm, and the spacing between adjacent micro-concave structures is 20mm.

[0054] Example 4 (1) The polymer film I with metal foil I containing diamond-shaped perforations on both sides is placed in an RF plasma etching machine, and a mixture of argon and oxygen with a volume ratio of 4:1 is introduced to form a micro-concave structure on the surface of the polymer film I. The metal foil I is removed to obtain the polymer film base layer I. Operating conditions for the radio frequency plasma etching machine: radio frequency power of 200W, gas pressure of 1Pa, and time of 10min; The micro-concave structure consists of rhomboid pits arranged in parallel and staggered patterns, with an area of ​​5 mm². 2 The depth is 0.3 μm, the width is 1.5 mm, and the spacing between adjacent micro-concave structures is 2 mm; The thickness of polymer film base layer I is 30 times the depth of the micro-recessed structure; (2) A first transition layer and a first metal layer are sequentially deposited on the upper surface of the polymer film substrate I using a DC magnetron sputtering instrument, and a second transition layer and a second metal layer are sequentially deposited on the lower surface of the polymer film substrate I to obtain a current collector semi-finished product; The first and second transition layers have the same material and thickness, both being aluminum oxide with a thickness of 100 nm. The first metal layer and the second metal layer have the same material and thickness, both being aluminum with a thickness of 1.5μm; Operating conditions for the DC magnetron sputtering instrument for the first and second transition layers: vacuum level 0.001 Pa, sputtering power 300 W, gas pressure 0.5 Pa, temperature 100 °C, deposition rate 10 nm / min; Operating conditions for the DC magnetron sputtering instrument for the first and second metal layers: vacuum level 0.001 Pa, sputtering power 400 W, gas pressure 0.5 Pa, temperature 100 °C, deposition rate 15 nm / min; The first and second transition layers have nano-protrusion structures on both sides, with a height of 50 nm. (3) Anneal the current collector semi-finished product in the presence of nitrogen and cool it naturally to room temperature to obtain the intermediate product; Annealing conditions: temperature 120℃, heating rate 5℃ / min, holding time 2h; (4) Coat the upper and lower surfaces of the intermediate product with the first conductive layer and the second conductive layer respectively to obtain the positive electrode composite current collector; Both the first conductive layer and the second conductive layer are made of graphene.

[0055] Example 5 The same method as in Example 1 was used, except that metal foil I in step (1) was replaced with metal foil IV, and the remaining steps and conditions were the same, to obtain a positive electrode composite current collector; The micro-concave structure consists of rhomboid pits arranged in parallel alignment, with an area of ​​5 mm². 2 The depth is 0.3 μm, the width is 1.5 mm, and the spacing between adjacent micro-concave structures is 2 mm.

[0056] Comparative Example 1 (1) A first transition layer and a first metal layer are sequentially deposited on the upper surface of polymer film I using a DC magnetron sputtering instrument, and a second transition layer and a second metal layer are sequentially deposited on the lower surface of polymer film substrate I to obtain a current collector semi-finished product; The first and second transition layers have the same material and thickness, both being aluminum oxide with a thickness of 100 nm. The first metal layer and the second metal layer have the same material and thickness, both being aluminum with a thickness of 1.5μm; Operating conditions for the DC magnetron sputtering instrument for the first and second transition layers: vacuum level 0.001 Pa, sputtering power 300 W, gas pressure 0.5 Pa, temperature 100 °C, deposition rate 10 nm / min; Operating conditions for the DC magnetron sputtering instrument for the first and second metal layers: vacuum level 0.001 Pa, sputtering power 400 W, gas pressure 0.5 Pa, temperature 100 °C, deposition rate 15 nm / min; The first and second transition layers have nano-protrusion structures on both sides, with a height of 50 nm. (3) Anneal the current collector semi-finished product in the presence of nitrogen and cool it naturally to room temperature to obtain the positive electrode composite current collector; Annealing conditions: temperature 120℃, heating rate 5℃ / min, holding time 2h.

[0057] Comparative Example 2 (1) The polymer film II with circular perforated metal foil covering both sides is placed in an RF plasma etching machine, and a mixture of argon and oxygen with a volume ratio of 3:1 is introduced to form a micro-concave structure on the surface of the polymer film II. The metal foil is removed to obtain the polymer film base layer I. Operating conditions for the radio frequency plasma etching machine: radio frequency power of 250W, gas pressure of 1Pa, and time of 8min; The micro-concave structure consists of circular pits arranged in parallel and staggered patterns, with an area of ​​1.13 mm. 2 The depth is 0.2 μm, the diameter is 1.2 mm, and the spacing between adjacent micro-concave structures is 1.8 mm; The thickness of polymer film base layer I is 30 times the depth of the micro-recessed structure; (2) A first transition layer and a first metal layer are sequentially deposited on the upper surface of the polymer film substrate I using a DC magnetron sputtering instrument, and a second transition layer and a second metal layer are sequentially deposited on the lower surface of the polymer film substrate I to obtain a current collector semi-finished product; The first and second transition layers are made of the same material and have the same thickness, both being titanium oxide with a thickness of 150nm. The first metal layer and the second metal layer have the same material and thickness, both being copper and 1.2 μm thick; Operating conditions for the DC magnetron sputtering instrument for the first and second transition layers: vacuum level 0.001 Pa, sputtering power 250 W, gas pressure 0.5 Pa, temperature 100 °C, deposition rate 10 nm / min; Operating conditions for the DC magnetron sputtering instrument for the first and second metal layers: vacuum level 0.001 Pa, sputtering power 350 W, gas pressure 0.5 Pa, temperature 100 °C, deposition rate 10 nm / min; The first and second transition layers have nano-protrusion structures on both sides, with a height of 50 nm. (3) Anneal the current collector semi-finished product in the presence of nitrogen and cool it naturally to room temperature to obtain the negative electrode composite current collector; Annealing conditions: temperature 100℃, heating rate 5℃ / min, holding time 1.5h.

[0058] Comparative Example 3 (1) The polymer film III, which has rectangular perforated metal foil covering both sides, is placed in an RF plasma etching machine. A mixture of argon and oxygen with a volume ratio of 5:1 is introduced to form a micro-concave structure on the surface of the polymer film III. The metal foil is then removed to obtain the polymer film base layer I. Operating conditions for the radio frequency plasma etching machine: radio frequency power of 300W, gas pressure of 1Pa, and time of 12min; The micro-concave structure consists of rectangular pits arranged in a row along the length, with the rows arranged in parallel and staggered patterns, each with an area of ​​5 mm². 2 The depth is 0.4 μm, the width is 1.8 mm, and the spacing between adjacent micro-concave structures is 2.5 mm; The thickness of polymer film base layer I is 30 times the depth of the micro-recessed structure; (2) A first transition layer and a first metal layer are sequentially deposited on the upper surface of the polymer film substrate I using a DC magnetron sputtering instrument, and a second transition layer and a second metal layer are sequentially deposited on the lower surface of the polymer film substrate I to obtain a current collector semi-finished product; The first transition layer and the first metal layer serve as the positive electrode side. The first transition layer is made of zirconium oxide and has a thickness of 180 nm; the first metal layer is made of aluminum and has a thickness of 2 μm. The second transition layer and the second metal layer serve as the negative electrode side. The second transition layer is made of aluminum oxide and has a thickness of 120 nm. The second metal layer is made of copper and has a thickness of 1.8 μm. Operating conditions for the DC magnetron sputtering instrument in the first transition layer: vacuum level of 0.001 Pa, sputtering power of 280 W, gas pressure of 0.5 Pa, temperature of 100 °C, and deposition rate of 10 nm / min; Operating conditions for the DC magnetron sputtering instrument in the second transition layer: vacuum level of 0.001 Pa, sputtering power of 260 W, gas pressure of 0.5 Pa, temperature of 100 °C, and deposition rate of 10 nm / min. Operating conditions for the DC magnetron sputtering instrument for the first metal layer: vacuum level of 0.001 Pa, sputtering power of 420 W, gas pressure of 0.5 Pa, temperature of 100 °C, and deposition rate of 15 nm / min; Operating conditions for the DC magnetron sputtering instrument for the second metal layer: vacuum degree of 0.001 Pa, sputtering power of 380 W, gas pressure of 0.5 Pa, temperature of 100 °C, and deposition rate of 15 nm / min; The first and second transition layers have nano-protrusion structures on both sides, with a height of 50 nm. (3) Anneal the current collector semi-finished product in the presence of nitrogen and cool it naturally to room temperature to obtain a bipolar composite current collector; Annealing conditions: temperature 150℃, heating rate 5℃ / min, holding time 3h.

[0059] Comparative Example 4 The process was carried out using a method similar to that in Example 1, except that the vacuum level of the DC magnetron sputtering instrument for the first and second transition layers in step (2) was adjusted to 10 Pa. All other steps and conditions were the same, and a positive electrode composite current collector was obtained. The first and second transition layers have nano-protrusion structures on both sides, with a height of 200 nm.

[0060] Test Example 1 The composite current collectors prepared in the aforementioned examples were subjected to the following performance tests: 1. Tensile strength was measured using the method specified in GB / T 1040.1-2018; 2. The interfacial bonding force was measured using the method specified in GB / T 8808-1988; 3. The capacity retention rate after 500 discharge cycles was measured using the method in GB 31241-2014; The test results are shown in Table 1 below.

[0061] Table 1

[0062] As shown in Table 1, the composite current collector provided by this invention exhibits higher tensile strength, higher interfacial adhesion, and higher conductivity. Specifically, a comparison between Example 1 and Comparative Example 1 demonstrates that the micro-dimpled structure improves tensile strength and cycle life. A comparison between Example 1 and Comparative Example 4 shows that the transition layer used in this invention significantly enhances interfacial adhesion and reduces active material peeling. This invention, through a multi-level structural design of a polymer base layer and a metal conductive layer, combined with plasma etching, magnetron sputtering, and annealing processes, successfully prepares a composite current collector with excellent mechanical strength, conductivity, and interfacial adhesion. Its performance is significantly superior to traditional metal foil materials, making it suitable for various energy storage devices such as lithium-ion batteries, sodium-ion batteries, and supercapacitors.

[0063] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite current collector, characterized in that, The composite current collector includes, from top to bottom, a first metal layer, a first transition layer, a polymer film base layer, a second transition layer, and a second metal layer; The polymer film substrate has micro-concave structures on both sides; the micro-concave structures are rhomboid pits. The first transition layer and the second transition layer are each made of metal oxide, and both sides have nano-protrusion structures; the height of the nano-protrusion structures is 20-50 nm. The first metal layer and the second metal layer are each made of an independently conductive metallic material.

2. The composite current collector according to claim 1, characterized in that, The composite current collector further includes, from top to bottom, a first conductive layer, a first metal layer, a first transition layer, a polymer film base layer, a second transition layer, a second metal layer, and a second conductive layer; The materials of the first conductive layer and the second conductive layer are each independently selected from at least one of thin-layer graphite, carbon black, graphene, and carbon nanotubes.

3. The composite current collector according to claim 1 or 2, characterized in that, The depth of the micro-concave structure is 0.1-0.5μm, the width is 0.5-5mm, and the spacing between adjacent micro-concave structures is 1-20mm; And / or, the area of ​​the rhomboid recess is 0.2-25 mm. 2 ; And / or, the micro-concave structures are arranged in a parallel, staggered pattern.

4. The composite current collector according to claim 1 or 2, characterized in that, The polymer film base layer is made of at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. And / or, the metal oxide is selected from at least one of aluminum oxide, titanium oxide, and zirconium oxide; And / or, the metallic conductive material is selected from at least one of copper, aluminum, nickel, silver, and gold.

5. The composite current collector according to claim 1 or 2, characterized in that, The thickness of the polymer film substrate is 18-30 times the depth of the micro-recessed structure, the thickness of the first metal layer and the second metal layer are each independently 0.5-2 μm, and the thickness of the first transition layer and the second transition layer are each independently 30-200 nm. And / or, the thickness of the first conductive layer and the second conductive layer are each independently 0.2-2 μm.

6. A method for preparing a composite current collector as described in any one of claims 1-5, characterized in that, The method includes: (1) In the presence of oxygen-containing gas, a polymer film with diamond-shaped perforations covering both sides of the polymer film is formed on the surface of the polymer film by plasma etching process to form a micro-concave structure, and the metal foil is removed to obtain polymer film base layer I; (2) A first transition layer and a first metal layer are sequentially deposited on the upper surface of the polymer film substrate I by magnetron sputtering, and a second transition layer and a second metal layer are sequentially deposited on the lower surface of the polymer film substrate I to obtain a current collector semi-finished product; the vacuum degree of the magnetron sputtering process is 0.001-0.1 Pa; (3) The current collector semi-finished product is annealed in the presence of an inert gas to obtain a composite current collector; the annealing temperature is 80-150℃.

7. The method according to claim 6, characterized in that, The method further includes coating the upper and lower surfaces of the intermediate product obtained by the annealing treatment with a first conductive layer and a second conductive layer, respectively, to obtain a composite current collector.

8. The method according to claim 6 or 7, characterized in that, In step (1), the operating conditions of the plasma etching process include: radio frequency power of 100-300W, gas pressure of 0.5-2Pa, and time of 5-15min; And / or, the oxygen-containing gas is a mixture of argon and oxygen; And / or, the volume ratio of argon to oxygen is 3-15:

1.

9. The method according to claim 6 or 7, characterized in that, In step (2), the operating conditions of the magnetron sputtering process include: sputtering power of 200-500W, gas pressure of 0.2-1Pa, temperature of 25-130℃, and deposition rate of 5-20nm / min; And / or, the sputtering power for depositing the first transition layer and the second transition layer is 50-100W lower than the sputtering power for depositing the first metal layer and the second metal layer; And / or, in step (3), the inert gas is nitrogen and / or argon; And / or, the annealing conditions include: a heating rate of 5-10℃ / min and a holding time of 0.5-4h.

10. The application of the composite current collector according to any one of claims 1-5 in energy storage devices.

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