A composite current collector, a battery, and a method for preparing the composite current collector.

Abstract

This invention relates to the field of composite current collector technology, and discloses a composite current collector, a battery, and a method for preparing the composite current collector. The current collector includes a polymer substrate, metal coatings on both sides of the polymer substrate, and a MOF coating on the side of the metal coating away from the polymer substrate. This composite current collector is enhanced by a three-dimensional, high-strength, interconnected MOF network. Based on its 3D framework, electron mobility can be improved, thus forming an ultrafast ion transport network with excellent ion conductivity. Secondly, the metal atoms and nitrogen atoms loaded on the MOF can effectively convert the lithium-phobicity of the carbon material into lithium-philicity, thereby promoting the lithium plating process on the electrode. Furthermore, by reducing the local current density and limiting the volume change within the three-dimensional network porous structure, the growth of dendritic crystals can be effectively suppressed.

Description

Technical Field

[0001] This invention relates to the field of composite current collector technology, and in particular to a composite current collector, a battery, and a method for preparing the composite current collector. Background Technology

[0002] Battery current collectors are a crucial component of batteries, connected to the positive and negative terminals. Their primary function is to concentrate the internal current, enabling the battery to output more stable and efficient electrical energy. Traditional current collectors are typically made of highly conductive metals such as copper and silver. However, large burrs are prone to form during manufacturing, causing internal short circuits and potentially leading to thermal runaway. Currently, composite current collectors are preferred. These are composite materials made by depositing copper or aluminum onto both sides of a PET or similar base film using processes such as magnetron sputtering or vacuum deposition. This creates a three-layer composite structure of "metal-polymer-metal," which exhibits high stability and conductivity, making it widely used as a current collector material in lithium-ion batteries.

[0003] Although the small size of the burrs generated by the composite current collector and the short-circuit effect caused by the heating of the superimposed polymer material layer can greatly reduce the short-circuit current in the short term, as the charge-discharge cycle progresses, the inherent protrusions on the current collector surface will lead to excessive Li ion flow, eventually forming a localized non-uniform current density. A large number of lithium dendrites will form on the current collector surface. The excessive generation of lithium dendrites can pierce the separator, leading to short circuits and thermal runaway in the battery. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a composite current collector, a battery, and a method for preparing the composite current collector. The MOF coating on the composite current collector can effectively suppress the growth of lithium dendrites, solving the problem that the excessive generation of lithium dendrites can puncture the separator, leading to short circuits and thermal runaway in the battery.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] In a first aspect, a composite current collector includes a polymer substrate, with metal coatings on both sides of the polymer substrate and an MOF coating on the side of the metal coating away from the polymer substrate.

[0007] As a further implementation, the material of the metal coating is selected from copper or aluminum.

[0008] As a further implementation, the MOF coating is loaded onto the surface of the metal coating by magnetron sputtering.

[0009] As a further implementation, the total thickness of the polymer base layer, the metal coating, and the MOF coating is between 1.5 μm and 4.5 μm.

[0010] As a further implementation, the polymer base layer is made of one or more of polyethylene, polypropylene, and thermoplastic polyester.

[0011] As a further implementation, the material of the MOF coating is selected from 2-methylimidazole solution and nitrate solution.

[0012] Secondly, a method for preparing a composite current collector includes the following steps:

[0013] Metal coatings are deposited on the upper and lower surfaces of a polymer substrate; a 2-methylimidazole solution and a nitrate solution are mixed in a set ratio to obtain a mixture, which is then heated and dried before being calcined under nitrogen protection to synthesize a MOF coating; the prepared MOF coating is loaded onto the outer surface of the metal coating by magnetron sputtering to obtain a composite current collector as described above.

[0014] As a further implementation, the concentration ratio of the 2-methylimidazole solution to the nitrate solution is in the range of 10:1 to 5:1.

[0015] As a further implementation, the heating temperature of the mixture is between 110℃ and 130℃, and the heating time is 8-10 hours; the flow rate of the nitrogen gas is 5℃ / min.

[0016] Thirdly, a battery comprising a composite current collector as described in any of the above.

[0017] The beneficial effects of the present invention are as follows:

[0018] This invention loads a MOF (Metal-Organic Foil) coating onto the metal coating surface of the original composite current collector, resulting in an improved composite current collector. This composite current collector is enhanced by a three-dimensional, high-strength, interconnected MOF network. Based on its 3D framework, electron mobility is improved, thus forming an ultrafast ion transport network with excellent ion conductivity. Secondly, the metal atoms and nitrogen atoms loaded on the MOF can effectively transform the lithiophilic nature of carbon materials into lithiophilic nature, thereby promoting the lithium plating process on the electrode. Furthermore, by reducing the local current density and limiting volume changes within the three-dimensional porous network structure, dendritic growth can be effectively suppressed. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a schematic diagram of the composite current collector in an embodiment of the present invention.

[0021] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0022] Wherein: 1: MOF coating, 2: metal coating, 3: polymer base layer. Detailed Implementation

[0023] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] Example 1

[0025] In a typical embodiment of the present invention, reference is made to Figure 1 As shown, a composite current collector includes a polymer base layer 3, a metal coating 2, and a MOF coating 1, wherein the metal coating 2 is deposited on the upper and lower surfaces of the polymer base layer 3, and the MOF coating 1 is disposed on the outer surface of the metal coating 2. The total thickness of the composite current collector is between 1.5 μm and 4.5 μm.

[0026] Specifically, the polymer base layer 3 and the metal coating layer 2 form a three-layer composite structure of "metal-polymer material-metal", which is a current technology. The material of the metal coating layer 2 is selected from copper or aluminum. The polymer base layer 3 can be made of PET, PP, PE, etc. PE is polyethylene, PP is polypropylene, and PET is commonly known as polyester resin. It is a condensation polymer of terephthalic acid and ethylene glycol, and together with PBT, it is collectively referred to as thermoplastic polyester or saturated polyester. The metal coating layer 2 is loaded onto the polymer base layer 3 through processes such as magnetron sputtering or vacuum coating.

[0027] MOF coating 1, or metal-organic framework, was modified in this embodiment to control the uniform deposition of lithium ions, thereby achieving uniform current density distribution, improved cycle stability, and prevention of lithium dendrite formation. Metal-organic framework (MOF) is a novel crystalline porous material formed by the self-assembly of transition metal ions and organic ligands to create a periodic network structure.

[0028] MOFs (Metal-on-Fibers) possess characteristics such as high porosity, low density, regular pore structure, and adjustable pore size, offering significant advantages in high-performance three-dimensional current collectors. Furthermore, the metal and nitrogen atoms generated during the carbonization process of MOFs can effectively transform the lithium-repellent nature of carbon materials into lithium-affinity, thereby promoting lithium plating on the electrodes. In addition, by reducing local current density and limiting volume changes within the three-dimensional porous network structure, dendrite growth can be effectively suppressed. This also allows this layered substrate to adapt to high areal loading lithium deposition, significantly reducing lithium dendrite formation. Moreover, lithium dendrites are mostly precipitated in a planar, two-dimensional form, solving the problem that excessive lithium dendrite formation can puncture the separator, leading to short circuits and thermal runaway in the battery.

[0029] Example 2

[0030] In a typical embodiment of the present invention, reference is made to Figure 1 As shown, a method for preparing a composite current collector involves first depositing a metal coating 2 on the upper and lower surfaces of a polymer base layer 3, then preparing a MOF, and finally loading the prepared MOF onto the surface of the metal coating 2.

[0031] The preparation steps of MOF are as follows: 2-methylimidazole solution and nitrate solution are mixed to obtain a mixed solution, wherein the molar concentration of 2-methylimidazole to the molar concentration of nitrate solution is in the range of 10:1 to 5:1.

[0032] The above mixed solution was heated at 110℃~130℃ for 8~10 hours and then dried by centrifugation. Subsequently, it was calcined at 400℃~500℃ under N2 protection at a flow rate of 5℃ / min to synthesize MOF.

[0033] The prepared MOF is loaded onto the surface of the metal coating 2 by magnetron sputtering or hydrothermal evaporation to form a composite current collector with a surface-loaded MOF coating 1 and a thickness of 1.5 to 5 μm.

[0034] Implementation Method 1:

[0035] Metal coatings 2 were deposited on the upper and lower surfaces of a polymer substrate 3 by magnetron sputtering. A 0.5 mol / L 2-methylimidazole solution and a 0.05 mol / L cobalt nitrate solution were mixed. The mixture was heated at 110 °C for 8 hours and then centrifuged to dry. Subsequently, it was calcined at 400 °C under N2 protection at a flow rate of 5 °C / min to synthesize a MOF. The prepared MOF was then loaded onto the surface of the metal coating using magnetron sputtering to form a composite current collector with a surface-loaded MOF and a thickness of 1.5 μm.

[0036] Implementation Method Two:

[0037] Metal coatings 2 were deposited on the upper and lower surfaces of a polymer base layer 3 by magnetron sputtering. A 0.25 mol / L 2-methylimidazole solution and a 0.05 mol / L cobalt nitrate solution were mixed. The mixture was heated at 110 °C for 8 hours and then centrifuged to dry. Subsequently, it was calcined at 400 °C under N2 protection at a flow rate of 5 °C / min to synthesize a MOF. The prepared MOF was then loaded onto the surface of the metal coating 2 using magnetron sputtering or hydrothermal evaporation to form a composite current collector with a surface-loaded MOF coating 1 and a thickness of 1.5 μm.

[0038] Implementation Method 3

[0039] Metal coatings 2 were deposited on the upper and lower surfaces of a polymer base layer 3 by magnetron sputtering. A 0.5 mol / L 2-methylimidazole solution and a 0.05 mol / L cobalt nitrate solution were mixed. The mixture was heated at 110°C for 8 hours and then centrifuged to dry. Subsequently, it was calcined at 400°C under N2 protection at a flow rate of 5°C / min to synthesize a MOF. The prepared MOF was then loaded onto the surface of the metal coating 2 using magnetron sputtering or hydrothermal evaporation to form a composite current collector with a surface-loaded MOF coating 1 and a thickness of 4.5 μm.

[0040] Implementation Method 4

[0041] Metal coatings 2 were deposited on the upper and lower surfaces of a polymer base layer 3 by magnetron sputtering. A 0.5 mol / L 2-methylimidazole solution and a 0.05 mol / L zinc nitrate solution were mixed. The mixture was heated at 110°C for 10 hours and then centrifuged to dry. Subsequently, it was calcined at 400°C under N2 protection at a flow rate of 5°C / min to synthesize a MOF. The prepared MOF was then loaded onto the surface of the metal coating 2 using magnetron sputtering or hydrothermal evaporation to form a composite current collector with a surface-loaded MOF coating 1 and a thickness of 1.5 μm.

[0042] Implementation Method 5

[0043] Metal coatings 2 were deposited on the upper and lower surfaces of a polymer base layer 3 by magnetron sputtering. A 0.5 mol / L 2-methylimidazole solution and a 0.05 mol / L zinc nitrate solution were mixed. The mixture was heated at 130°C for 10 hours and then centrifuged to dry. Subsequently, it was calcined at 500°C under N2 protection at a flow rate of 5°C / min to synthesize a MOF. The prepared MOF was then loaded onto the surface of the metal coating 2 using magnetron sputtering or hydrothermal evaporation to form a composite current collector with a surface-loaded MOF coating 1 and a thickness of 1.5 μm.

[0044] Comparative Example 1:

[0045] The difference from the above-described embodiment one is that 2-methylimidazole solution is not used; only cobalt nitrate solution is used alone.

[0046] Comparative Example 2:

[0047] The difference from the above-described embodiment one is that a blank composite current collector is used, that is, no MOF coating is loaded on the surface of the composite current collector.

[0048] Table 1

[0049]

[0050]

[0051] Table 1 above compares the material performance of different implementation methods and comparative examples. It can be concluded that the composite current collector with MOF coating 1 ultimately forms only a small amount of lithium dendrites on its surface. In contrast, in the comparative examples, Comparative Example 1 uses cobalt nitrate solution alone for the MOF, and Comparative Example 2 does not have a MOF coating, both ultimately forming a large number of lithium dendrites on the current collector surface. Furthermore, the tensile strength, elongation, and cycle capacity retention of the comparative examples are all weaker than those of Embodiments 1 to 5.

[0052] This embodiment proposes a composite current collector that can prevent lithium dendrite formation and improve cycle stability by preparing a metal-organic framework (MOF) and loading the prepared MOF onto the surface of the metal coating 2 of the original composite current collector via magnetron sputtering. This composite current collector is enhanced by a three-dimensional, high-strength, interconnected MOF network. Based on its 3D framework, electron mobility can be improved, thus forming an ultrafast ion transport network with excellent ionic conductivity. Secondly, the metal atoms and nitrogen atoms loaded on the MOF can effectively transform the lithium-phobicity of the carbon material into lithium-philicity, thereby promoting the lithium plating process on the electrode. Furthermore, by reducing the local current density and limiting the volume change within the three-dimensional network porous structure, the growth of dendrites can be effectively suppressed.

[0053] Example 3

[0054] In a typical embodiment of the present invention, a battery is provided, which includes a composite current collector as shown in Example 1. Only a small number of lithium dendrites are formed on the composite current collector in the battery, thereby increasing battery life and improving battery performance.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite current collector, characterized in that, Includes the following steps: Metal plating layers are deposited on the upper and lower surfaces of the polymer base layer; A 2-methylimidazole solution and a nitrate solution were mixed in a set ratio to obtain a mixed solution. The nitrate solution was either a cobalt nitrate solution or a zinc nitrate solution. After heating and drying the mixed solution, it was calcined at 400℃~500℃ under nitrogen protection to synthesize a MOF coating. The prepared MOF coating was loaded onto the outer surface of a metal coating by magnetron sputtering to obtain a composite current collector.

2. The method for preparing a composite current collector according to claim 1, characterized in that, The concentration ratio of 2-methylimidazole solution to nitrate solution ranges from 10:1 to 5:

1.

3. The method for preparing a composite current collector according to claim 1, characterized in that, The heating temperature of the mixture is between 110℃ and 130℃, and the heating time is 8-10 hours; the flow rate of the nitrogen gas is 5℃ / min.

4. A composite current collector, characterized in that, The product is prepared by the method described in claim 1, comprising a polymer base layer, metal coatings on both sides of the polymer base layer, and an MOF coating on the side of the metal coating away from the polymer base layer.

5. A composite current collector according to claim 4, characterized in that, The material of the metal coating is selected from copper or aluminum.

6. A composite current collector according to claim 4, characterized in that, The total thickness of the polymer base layer, metal coating, and MOF coating is between 1.5 μm and 4.5 μm.

7. A composite current collector according to claim 4, characterized in that, The polymer base layer is made of one or more of polyethylene, polypropylene, and thermoplastic polyester.

8. A battery, characterized in that, The battery includes the composite current collector as described in any one of claims 4-7.

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