Current collector and preparation method therefor

Abstract

Provided in the present application are a current collector and a preparation method therefor. The current collector comprises a metal layer, wherein at least part of the metal layer comprises metal grains stacked in a staggered manner, and the average length L of the metal grains in a Z direction and the thickness K of the metal layer satisfy the following relational expression: 0<L≤0.8K; and the Z direction is the direction of the thickness of the metal layer.

Description

A current collector and its preparation method Technical Field

[0001] This application belongs to the field of lithium-ion battery technology, specifically relating to a current collector and its preparation method. Background Technology

[0002] Currently, polymer-based current collectors are receiving widespread attention and application in the new energy industry. These current collectors are typically prepared by depositing a metal layer onto a polymer film (such as polyester or polyolefin films) using physical vapor deposition (PVD), resulting in a current collector with good conductivity. Compared to traditional current collectors, polymer-based current collectors offer advantages such as lower cost, lighter weight, and better internal insulation. These characteristics enable them to reduce battery costs and improve battery energy density and safety when used in batteries.

[0003] However, after the current collector is prepared, it will be further used to make electrodes. In the process of making electrodes, there are usually various processes such as rolling, which puts higher requirements on the mechanical properties of the current collector. However, the current collector prepared by the existing technology is easily damaged during the electrode preparation process and has poor mechanical properties, which cannot meet the requirements of the electrode preparation process.

[0004] In view of this, further improving the mechanical properties of current collectors to enhance their stability during electrode fabrication is of great significance for further promoting the application of current collectors in batteries and for further improving battery performance. Summary of the Invention

[0005] To address the problems and shortcomings of existing technologies, this application provides a current collector and its preparation method. This current collector possesses superior mechanical properties, which can mitigate surface defects generated during electrode rolling. Simultaneously, it exhibits good electrical conductivity. Therefore, utilizing this current collector can facilitate further optimization of the battery's cycle charge-discharge performance.

[0006] According to a first aspect of this application, a current collector is provided, comprising a metal layer, at least a portion of which comprises misaligned stacked metal grains, and the average length L of the metal grains in the Z direction and the thickness K of the metal layer satisfy the following relationship: 0 < L ≤ 0.8K; where the Z direction is the direction of the metal layer thickness.

[0007] In the battery electrode manufacturing process, to improve the unit capacity of the electrode, it is generally necessary to roll the electrode with rollers. During the rolling process, a large rolling pressure is applied to the Z-direction (perpendicular to the in-plane direction) of the electrode, which places higher demands on the mechanical properties of the current collector in the Z-direction. Currently, commercially available current collectors are generally prepared using the PVD (Physical Vapor Deposition) method. The metal grains in the metal layer exhibit a columnar crystal structure, with larger grains in the Z-direction, resulting in poorer mechanical properties. These grains are prone to defects during the rolling process, leading to decreased conductivity and reduced battery cycle life. Therefore, to further improve the mechanical properties of the current collector in the Z-direction, it is necessary to develop a new current collector to promote its application and widespread use in batteries.

[0008] This application controls at least a portion of the metal layer in the current collector to contain misaligned stacked metal grains, and the average length L of the metal grains in the Z direction satisfies the relationship 0 < L ≤ 0.8K with respect to the thickness K of the metal layer. Firstly, this ensures that at least a portion of the metal grains in the metal layer have a relatively small average length L in the Z direction, less than the thickness of the metal layer. This improves the overall resistance of the metal layer to rolling pressure, allowing it to withstand higher pressure during electrode fabrication. Even under high rolling pressure, the current collector will not develop significant structural defects or cracks, maintaining high stability. Secondly, these misaligned stacked metal grains, when subjected to rolling pressure during electrode fabrication, provide mutual support due to their misalignment, further enhancing the pressure resistance of the current collector and thus the overall pressure resistance of the electrode, optimizing the structural stability of both the current collector and the electrode.

[0009] Regarding the dislocation-stacking metal grain structure contained in at least a portion of the metal layer in this application, please refer to Figure 1 of this application. The crystal faces of these dislocation-stacking metal grains are interconnected to form a continuous network structure. Therefore, by designing a metal layer with a specialized structure, this application effectively improves the overall stability of the electrode and the battery. This prevents the electrode from becoming unstable under cyclic stress due to structural defects in the current collector during charge-discharge cycles, thus optimizing the battery's cycle performance.

[0010] It should be noted that in this application, the Z direction in the metal layer refers to the direction of the metal layer thickness, which is perpendicular to the plane of the metal layer. Therefore, the average length L of the grains in the Z direction of the metal layer refers to the average length of the grains in the direction of the metal layer thickness.

[0011] Furthermore, in existing technologies, the average length L in the Z-direction of metal grains in the metal layer is typically large, resulting in poor metal layer density and consequently reduced conductivity. However, this application controls the average length L in the Z-direction of the dislocation-stacking metal grains in at least a portion of the current collector's metal layer to satisfy the relationship 0 < L ≤ 0.8K. This results in higher metal layer density, which improves the conductivity of the current collector and further optimizes the battery's cycle charge-discharge performance.

[0012] In some embodiments, at least a portion of the metal layer in the longitudinal section forms a staggered stacked metal grain structure, and the grain boundaries between the metal grains together form a continuous network structure.

[0013] In some embodiments, at least a portion of the metal layer in the cross-section forms a staggered stacked metal grain structure, with the grain boundaries between the metal grains forming a continuous network structure.

[0014] In some embodiments, at least a portion of the metal layer is filled with the metal grains in the Z direction.

[0015] In some embodiments, the metal layer is composed of misaligned stacked metal grains, the grain boundaries between the metal grains together forming a continuous network structure, and the average length L of the metal grains in the Z direction and the thickness K of the metal layer satisfy the following relationship: 0 < L ≤ 0.8K; the Z direction is the direction of the thickness of the metal layer.

[0016] In some embodiments, in the longitudinal section of the metal layer, the area ratio of the misaligned stacked metal grains in the metal layer is ≥20%. Ensuring a certain proportion of the area of ​​the misaligned stacked metal grains, i.e., ensuring a sufficient proportion of the misaligned stacked metal grains in the metal layer, effectively improves the pressure-bearing capacity of the current collector, i.e., effectively improves the pressure-bearing capacity of the current collector during the rolling process, and improves the stability of the current collector in use. Furthermore, the area ratio of the misaligned stacked metal grains in the metal layer can be specifically tested and calculated as follows: Take a longitudinal section of the metal layer every 5 meters, and accumulate at least 3 longitudinal sections for TEM characterization. Calculate the ratio of the area of ​​all misaligned stacked metal grains in each longitudinal section to the area of ​​the longitudinal section of the metal layer, and then take the average value. Here, the size of each longitudinal section is (1000~1500) × (800~1200) nm.

[0017] In some embodiments, the staggered stacked metal grains are uniformly distributed within the metal layer. Uniform distribution of the staggered stacked metal grains within the metal layer indicates that the current collector has a relatively uniform pressure-bearing capacity throughout when subjected to rolling pressure, meaning that it can withstand greater pressure at all points. This is beneficial for improving the overall pressure-bearing capacity of the current collector and preventing structural defects caused by poor pressure-bearing capacity in certain areas, which would affect the structural stability and service life of the current collector. Uniform distribution is defined as follows: A longitudinal section of the metal layer is taken every 5 meters, and at least 5 longitudinal sections are characterized using TEM. The area ratio of the staggered stacked metal grains within the metal layer is calculated. Among the 5 or more area ratios, (maximum value - minimum value) / maximum value < 50%. Here, the dimensions of each longitudinal section are (1000~1500) × (800~1200) nm.

[0018] In some embodiments, the current collector further includes a substrate layer, wherein the metal layer is disposed on at least one side surface of the substrate layer.

[0019] In some embodiments, the substrate layer satisfies at least one of the following conditions: the thickness of the substrate layer is 1.0~10μm; if the substrate layer is too thin, it will reduce the overall mechanical properties of the current collector, deteriorate its stability, and thus deteriorate the battery cycle performance; if the substrate layer is too thick, it will reduce the energy density of the battery and is also not conducive to improving the overall performance of the battery; the material of the substrate layer includes one or more of insulating polymer materials, metal materials, organic fiber materials, carbon materials, and inorganic materials, and the insulating polymer materials include polyethylene terephthalate, polypropylene, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, and polytetrafluoroethylene. The material comprises one or more of ethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, polyimide, and polyimide urea; the metallic material comprises one or more of aluminum, copper, nickel, iron, titanium, silver, gold, cobalt, chromium, molybdenum, or tungsten; the organic fiber material comprises one or more of polyacrylonitrile fiber, poly(p-phenylenebenzobisoxazole) fiber, polybenzimidazole fiber, and polyimide fiber; the carbon material comprises one or more of conductive carbon black, acetylene black, natural graphite, artificial graphite, mesophase carbon microspheres, mesophase carbon fiber, vapor-grown carbon fiber, hard carbon, soft carbon, petroleum coke, graphene, fullerene, carbon nanotubes, and glassy carbon; and the inorganic material comprises one or more of oxides, carbides, silicides, and nitrides. In some embodiments, the substrate layer material includes one or more of polyethylene terephthalate (PET), polypropylene (PP), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polyethylene (PE), polypropylene, polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polystyrene (PS), polyimide (PI), and polyimide urea (PASC).

[0020] In some embodiments, the metal layer satisfies at least one of the following conditions: (1) The thickness of the metal layer is 500~2000nm; as a conductive layer, if the metal layer is too thin, its conductivity is poor; if it is too thick, the current collector is too heavy, which is not conducive to improving the energy density of the battery; in some embodiments, the thickness of the metal layer is 800~1200nm; furthermore, if the thickness of the metal layer is controlled within the above range, it is more conducive to taking into account both the conductivity of the current collector and the energy density of the battery, and optimizing the overall performance of the battery; (2) The material of the metal layer includes one or more of aluminum, copper, silver, gold, nickel and their alloys; in some embodiments, the material of the metal layer includes one or more of copper, aluminum and their alloys.

[0021] In some embodiments, a metal layer 1 and a metal layer 2 are respectively provided on both sides of the substrate layer; the metal layer 1 and the metal layer 2 may be made of the same material or different materials.

[0022] In some embodiments, the Young's modulus of the current collector is in the range of >1600 MPa. A larger Young's modulus allows the current collector to possess better mechanical properties, further improving its structural stability and pressure resistance. This Young's modulus is controlled by adjusting the plasma bombardment parameters to control the grain refinement degree or by controlling the proportion of particles with an average grain length L in the Z direction that satisfies the following relationship: 0 < L ≤ 0.8K. The greater the ion bombardment intensity, the higher the grain refinement degree, and the greater the Young's modulus; similarly, the higher the mass proportion of particles with 0 < L ≤ 0.8K, the greater the Young's modulus.

[0023] In some embodiments, the current collector further includes a protective layer disposed on the surface of at least one metal layer. Adding a protective layer to the surface of the metal layer can prevent the metal layer from being chemically corroded or physically damaged, further improving the electrolyte resistance and mechanical properties of the current collector, and optimizing its stability.

[0024] In some embodiments, the protective layer satisfies at least one of the following conditions: (1) The thickness of the protective layer is 5~100nm; if the protective layer is too thin, it cannot effectively protect the metal layer and is not conducive to the charge-discharge cycle performance of the battery; if the protective layer is too thick, it will reduce the energy density of the battery; in some embodiments, the thickness of the protective layer is 10~80nm; further limiting the thickness of the protective layer to the above range is more conducive to taking into account the current collector and the performance of the battery in all aspects; (2) The material of the protective layer includes one or more of nickel, chromium, nickel-based alloy, copper-based alloy, copper oxide, aluminum oxide, silicon oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, copper chromate, copper chromite, carbon nanotubes, carbon nanofibers and graphene.

[0025] In some implementations, the material of the protective layer may be consistent or inconsistent; the thickness of the protective layer may be consistent or inconsistent.

[0026] According to a second aspect of this application, a method for preparing the above-mentioned current collector is provided, comprising the following steps: S1. Placing a substrate layer in a vacuum evaporation chamber, melting and evaporating the metal material in the metal evaporation chamber at 1100~1600°C, causing the evaporated metal atoms to diffuse to at least one side surface of the substrate layer, and cooling and depositing to form a metal layer on at least one side surface of the substrate layer; S2. Performing plasma bombardment treatment on at least one side of the product obtained in S1 to obtain the current collector; the process conditions for plasma bombardment treatment are: the gas source is an inert gas, the gas flow rate is 10~300mL / min, the working power is 1~20kW, and the treatment time is not less than 5s. In the current collector preparation method provided in this application, after depositing metal layers on both surfaces of the polymer film, the metal layers are subjected to plasma bombardment treatment under specific process conditions. This effectively refines the average length of the metal grains in the Z direction, thereby effectively improving the mechanical properties of the current collector in the Z direction. Consequently, it is less prone to defects during the electrode rolling process and maintains high stability, which is beneficial to improving the stability of the current collector, electrode, and battery, and optimizing the charge-discharge cycle performance of the battery.

[0027] Preferably, in S2, the inert gas includes one or more of argon and helium.

[0028] In some implementations, the processing time in S2 is 10~60s.

[0029] In some embodiments, another method for preparing the above-mentioned current collector is provided, comprising the following steps: S1. Placing the substrate layer in a vacuum evaporation chamber, melting and evaporating the metal material in the metal evaporation chamber at 1100~1600°C, causing the evaporated metal atoms to diffuse to at least one surface of the substrate layer, and cooling and depositing to form a metal layer on at least one surface of the substrate layer; S2. Performing plasma bombardment treatment on at least one surface of the product obtained in S1; the process conditions for plasma bombardment treatment are: the gas source is an inert gas, the gas flow rate is 10~300mL / min, the working power is 1~20kW, and the treatment time is not less than 5s; S3. Forming a protective layer on at least one surface of the product in S2; the formation method includes one or more of physical vapor deposition, chemical vapor deposition, in-situ molding, coating, etc.

[0030] In some embodiments, vapor deposition methods include one or more of vacuum evaporation and magnetron sputtering; chemical vapor deposition includes one or more of atmospheric pressure chemical vapor deposition and plasma-enhanced chemical vapor deposition; and coating methods include one or more of die coating, blade coating, and extrusion coating.

[0031] According to a third aspect of this application, an electrode is provided, comprising the current collector described above or the current collector prepared by the above preparation method and an electrode active material located on the current collector.

[0032] According to a fourth aspect of this application, a lithium battery cell is provided, comprising the aforementioned electrode.

[0033] According to a fifth aspect of this application, a battery pack is provided, comprising the aforementioned lithium battery cell.

[0034] According to a sixth aspect of this application, an electrical device is provided, comprising the aforementioned lithium battery cell or the aforementioned battery pack.

[0035] In summary, the current collector provided in this application effectively improves the mechanical properties and conductivity of the current collector by controlling at least a portion of the metal layer in the current collector to contain misaligned stacked metal grains, and the average length L of the metal grains in the Z direction and the thickness K of the metal layer satisfy the relationship 0 < L ≤ 0.8K, thereby further optimizing the charge-discharge cycle performance of the battery. Attached Figure Description

[0036] Figure 1 is an electron microscope image of the aluminum metal layer after plasma bombardment treatment in Embodiment 1 of this application.

[0037] Figure 2 is an electron microscope image of the aluminum metal layer in Comparative Example 2 of this application before plasma bombardment treatment. Embodiments of the present invention

[0038] Example 1

[0039] The current collector of this embodiment is prepared according to the following steps:

[0040] S1. A 6μm thick PET film is placed in a vacuum evaporation chamber. High-purity aluminum wire (purity greater than 99.99%) in the metal evaporation chamber is melted and evaporated at 1300℃, so that the evaporated aluminum atoms diffuse to the two surfaces of the PET film. Under the cooling action of the main roller, the aluminum metal layers are cooled and deposited on the two surfaces of the PET film to form two aluminum metal layers with a thickness of 1μm.

[0041] S2. The product obtained in S1 is subjected to plasma bombardment treatment; the process conditions for plasma bombardment treatment are: the gas source is argon gas, the gas flow rate is 100mL / min, the working power is 10kW, and the treatment time is 30s.

[0042] S3. Place the product obtained in S2 in an oxygen atmosphere and perform oxidation treatment for 2 minutes to form an aluminum oxide protective layer with a thickness of 5nm on both surfaces of the product.

[0043] Example 2

[0044] It is basically the same as Example 1, except that in S2, the power in the plasma bombardment process is 1kW.

[0045] Example 3

[0046] It is basically the same as Example 1, except that in S2, the power in the plasma bombardment process is 20kW.

[0047] Example 4

[0048] It is basically the same as Example 1, except that in S2, the processing time in the plasma bombardment process is 5s.

[0049] Example 5

[0050] It is basically the same as Example 1, except that in S2, the processing time in the plasma bombardment process is 10s.

[0051] Example 6

[0052] It is basically the same as Example 1, except that in S2, the processing time in the plasma bombardment process is 60s.

[0053] Example 7

[0054] It is basically the same as Example 1, except that in S2, the argon flow rate in the plasma bombardment process is 10 mL / min.

[0055] Example 8

[0056] It is basically the same as Example 1, except that in S2, the argon flow rate in the plasma bombardment process is 300 mL / min.

[0057] Example 9

[0058] The process is basically the same as in Example 1, except that the metal layer is a copper layer. The specific preparation process is as follows: a 6μm thick PET film is placed in a vacuum evaporation chamber, and a high-purity copper wire (purity greater than 99.99%) in the metal evaporation chamber is melted and evaporated at 1500°C, so that the evaporated copper atoms diffuse to the two surfaces of the PET film. Under the cooling action of the main roller, the copper metal layer is cooled and deposited on the two surfaces of the PET film to form a two-layer copper metal layer with a thickness of 1μm.

[0059] Example 10

[0060] It is basically the same as Example 1, except that in S2, the power in the plasma bombardment process is 21kW.

[0061] Example 11

[0062] It is basically the same as Example 1, except that in S2, the argon flow rate in the plasma bombardment process is 310 mL / min.

[0063] Comparative Example 1

[0064] It is basically the same as Example 1, except that the power in the plasma bombardment process is 0.8kW.

[0065]

[0066] Comparative Example 2

[0067] It is basically the same as Example 1, except that the plasma bombardment treatment in S2 is not performed.

[0068] Comparative Example 3

[0069] It is basically the same as Example 9, except that the plasma bombardment treatment in S2 is not performed.

[0070] Comparative Example 4

[0071] It is basically the same as Example 1, except that in S2, the power in the plasma bombardment process is 0.5kW.

[0072] Comparative Example 5

[0073] It is basically the same as Example 1, except that in S2, the processing time in the plasma bombardment process is 3s.

[0074] Comparative Example 6

[0075] It is basically the same as Example 1, except that in S2, the argon flow rate in the plasma bombardment process is 5 mL / min.

[0076] Test case

[0077] 1. Experimental Construction Method

[0078] The average length of grains in the Z-direction, Young's modulus, surface roughness, sheet resistance, and number of voids in the metal layers of the current collectors prepared in all the above embodiments and comparative examples were tested. The specific test methods are as follows:

[0079] (1) Average grain length of the metal layer in the Z direction: The average grain length of the current collector metal layer in the Z direction was analyzed by combining focused ion beam microscopy (FIB-SEM) and field emission transmission electron microscopy (TEM). The specific method was as follows: The current collector sample was prepared according to the sample preparation requirements of FIB, and then placed in a FIB FIB-SEM (Zeiss Gemini2 Crossbeam) for ion cutting of its cross-section to prepare a cross-section sample with a thickness of about 50 nm. The prepared cross-section sample was placed in a TEM (JEM-2100F) for cross-section microstructure analysis (the cross-section size was (1000 - 1500) × (800 - 1200) nm). At the same time, the grains and their sizes were statistically analyzed using the software supporting the TEM, and the average length of the metal grains in the Z direction in the metal layer was obtained through calculation.

[0080] (2) Young's modulus: Used to characterize the mechanical properties of the current collector in the Z direction. The test method was as follows: The current collector was prepared according to the sample preparation method of atomic force microscopy (AFM), and then the sample was placed in an AFM (Bruker-Dimension Icon) to scan the surface of the sample. By detecting the force between the probe and the surface of the sample, and according to the force curve, Young's modulus was simulated and calculated.

[0081] (3) Surface roughness: A flat sample was placed on the sample stage of a surface roughness meter (Beijing Time TR260), and the surface of the sample was scanned with a probe to obtain the surface roughness Ra of the sample.

[0082] (4) Holes: The sample was placed in a surface quality detection system (Microvision charge-coupled device CCD) to scan the surface, and then the optical signal was converted into an electrical signal and transmitted to a computer to count the number of holes on the surface of the current collector sample per unit area (per square meter).

[0083] (5) Area ratio of misaligned stacked metal grains in the metal layer: One longitudinal section of the metal layer was intercepted every 5 meters, and more than 3 longitudinal sections were taken cumulatively for TEM characterization. The ratio of the area of all misaligned stacked metal grains in each longitudinal section of the metal layer to the area of the longitudinal section of the metal layer was calculated, and then the average value was taken. Here, the size of each longitudinal section was (1000 - 1500) × (800 - 1200) nm.

[0084] 2. Experimental results

[0085] The relevant test results of the current collectors prepared in all the above embodiments and comparative examples regarding the average length of the metal grains in the Z direction in the metal layer, Young's modulus, surface roughness, number of holes, and area ratio of misaligned stacked metal grains in the metal layer are shown in Table 1.

[0086] Table 1. Performance test results of current collectors in the embodiments and comparative examples.

[0087]

[0088] As shown in Table 1 above, in the current collector provided by this application, the average length L of the metal grains in the Z direction of the metal layer is controlled within a relatively small range relative to the thickness of the metal layer. This results in the current collector possessing superior mechanical and electrical properties. Simultaneously, the current collector also exhibits good surface roughness, which is beneficial for improving its adhesion to the electrode active material, enhancing electrode stability, and thus optimizing battery cycle performance. Furthermore, the current collector also has relatively few pores and defects on its surface, enabling it to maintain high stability during charge-discharge cycles.

[0089] Furthermore, as can be seen from Examples 1 and 9 and Comparative Examples 2 and 3, compared with traditional current collectors, the current collector prepared in this application has: a. a smaller average length of metal grains in the Z direction in the metal layer, which is the result of the added plasma post-processing step refining the metal grains; b. a larger Young's modulus, i.e., better mechanical properties in the Z direction, which is due to the refinement of metal grains in the Z direction; c. a higher surface roughness, which is due to the bombardment of the metal layer surface by plasma, and the higher roughness is beneficial to improving the adhesion between the current collector and the electrode active material in the subsequent electrode preparation process; d. a higher area ratio of misaligned stacked metal grains in the metal layer cross section, which is beneficial to improving the mechanical properties of the current collector. Therefore, the current collector provided by this application has superior mechanical and electrical properties, and can improve the adhesion with the electrode active material, thereby effectively improving the mechanical properties, electrical properties, and structural stability of the electrode. This is beneficial for the current collector and the electrode to maintain high stability during battery charge-discharge cycles and not be easily damaged by cyclic stress, thereby improving the cyclic charge-discharge performance of the battery. Furthermore, as can be seen from Figures 1 and 2, Figure 1 is an electron microscope image of the aluminum metal layer in Example 1 after plasma bombardment treatment, and Figure 2 is an electron microscope image of the aluminum metal layer in Comparative Example 2 without plasma bombardment treatment. After plasma bombardment treatment, the average length of the metal grains in the Z direction in the metal layer is significantly and effectively reduced, thereby optimizing the mechanical and electrical properties of the current collector and thus optimizing the battery's cycle charge-discharge performance. It can also be seen from Examples 1 and 2 that the lack of plasma bombardment treatment in Comparative Example 2 results in a lower Young's modulus of the current collector, which significantly reduces the structural strength and stability of the current collector, thus degrading its performance.

[0090] As can be seen from Examples 1-3, Example 10, and Comparative Examples 1 and 4, increasing the power of plasma bombardment treatment results in the following improvements in the current collector: a. The average length of the metal grains in the Z-direction of the metal layer decreases, due to the increased energy of the plasma post-treatment, which promotes grain refinement; b. The Young's modulus is larger, i.e., the mechanical properties in the Z-direction are improved, which is due to the finer metal grains in the Z-direction; c. The surface roughness is improved, because the increased plasma post-treatment power makes the plasma bombardment of the metal layer surface more intense. Furthermore, it can be seen that d. If the plasma bombardment treatment power is too low, the performance improvement is not significant, while if the power is too high, surface porosity defects will occur; and if the plasma bombardment treatment power is too low, the area ratio of misaligned stacked metal grains in the metal layer's longitudinal section will also decrease, which is also detrimental to improving the mechanical properties of the current collector.

[0091] As can be seen from Examples 1, 4-6 and Comparative Example 5: Increasing the plasma bombardment treatment time results in the following effects on the prepared current collector: a. The average size of the metal grains in the Z direction of the metal layer decreases, which is due to the increased plasma bombardment treatment time promoting grain refinement; b. The Young's modulus is larger, i.e. the mechanical properties in the Z direction are improved, which is due to the finer metal grains in the Z direction; c. The surface roughness is improved, which is due to the increased plasma post-treatment time making the plasma bombardment of the metal layer surface more intense; d. If the post-treatment time is too short, the area ratio of misaligned stacked metal grains in the metal layer in the longitudinal section of the metal layer decreases, and the performance improvement is not significant.

[0092] As can be seen from Examples 1, 7, 8, 10 and Comparative Example 6: Increasing the post-treatment gas flow rate results in the following improvements in the prepared current collector: a. The average size of the metal grains in the metal layer decreases in the Z direction. This is because increasing the plasma post-treatment flow rate increases the amount of plasma, thereby promoting grain refinement; b. The Young's modulus is larger, i.e., the mechanical properties in the Z direction are improved. This is due to the finer metal grains in the Z direction; c. The surface roughness is improved. This is because increasing the plasma post-treatment flow rate increases the amount of plasma, thereby making the plasma bombardment of the metal layer surface more intense. Furthermore, it can be seen that d. If the post-treatment gas flow rate is too low, the generated plasma is too low, the area ratio of the misaligned stacked metal grains in the metal layer decreases, resulting in a less significant performance improvement.

[0093] Furthermore, it can be seen from Examples 1-11 and Comparative Examples 1, 4-6 that even after a certain plasma bombardment treatment, the area ratio of misaligned stacked metal grains in the metal layer in Comparative Examples 1, 4-6 is low, less than 20%. Compared with other examples, the Young's modulus of the current collector in these comparative examples is low, which means that its mechanical properties are low. Therefore, the overall performance of the current collector is low.

Claims

1. A current collector comprising a metal layer, at least a portion of said metal layer comprising displaced stacked metal grains, wherein the average length L of said metal grains in the Z direction and the thickness K of said metal layer satisfy the following relationship: 0 < L ≤ 0.8K; The Z direction is the direction of the thickness of the metal layer.

2. The current collector of any one of claims 1, wherein: At least a portion of the metal layer is filled with the metal grains in the Z direction.

3. The current collector of claim 1, wherein: The metal layer is composed of displaced stacked metal grains, and the grain boundaries between the metal grains together form a continuous network structure. The average length L of the metal grains in the Z direction and the thickness K of the metal layer satisfy the following relationship: 0 < L ≤ 0.8K. The Z direction is the direction of the thickness of the metal layer.

4. The current collector of claim 1, wherein: In the longitudinal section of the metal layer, the area of ​​the misaligned stacked metal grains in the metal layer is ≥20%.

5. The current collector of claim 1, wherein: The misaligned stacked metal grains are uniformly distributed in the metal layer.

6. The current collector of claim 1, wherein: The current collector further includes a substrate layer, and the metal layer is disposed on at least one side surface of the substrate layer.

7. The current collector as claimed in claim 6, wherein: The substrate layer satisfies at least one of the following conditions: The thickness of the substrate layer is 1.0~10μm; The substrate layer is made of one or more of the following materials: insulating polymer materials, metallic materials, organic fiber materials, carbon materials, and inorganic materials. The insulating polymer material includes one or more of the following: polyethylene terephthalate, polypropylene, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, polyimide, and polyimide urea. The metallic material includes one or more of aluminum, copper, nickel, iron, titanium, silver, gold, cobalt, chromium, molybdenum, or tungsten; The organic fiber material includes one or more of polyacrylonitrile fiber, poly(p-phenylenebenzobisoxazole) fiber, polybenzimidazole fiber, and polyimide fiber. The carbon materials include one or more of the following: conductive carbon black, acetylene black, natural graphite, artificial graphite, mesophase carbon microspheres, mesophase carbon fibers, vapor-grown carbon fibers, hard carbon, soft carbon, petroleum coke, graphene, fullerene, carbon nanotubes, and glassy carbon. The inorganic material includes one or more of oxides, carbides, silicides, and nitrides.

8. The current collector of claim 6 or 7, wherein: The material of the substrate layer includes one or more of polyethylene terephthalate, polypropylene, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenylene ether, polystyrene, polyimide, and polyimide urea.

9. The current collector of claim 1, wherein: The metal layer satisfies at least one of the following conditions: (1) The thickness of the metal layer is 500~2000 nm; (2) The material of the metal layer includes one or more of aluminum, copper, silver, gold, nickel and their alloys.

10. The current collector of claim 1, wherein: The metal layer satisfies at least one of the following conditions: (1) The thickness of the metal layer is 800~1200 nm; (2) The material of the metal layer includes one or more of copper, aluminum and their alloys.

11. The current collector of claim 9 or 10, wherein: Metal layer 1 and metal layer 2 are respectively provided on both sides of the substrate layer, and the metal layer 1 and metal layer 2 are made of different materials.

12. The current collector as claimed in claim 11, wherein: The range of Young's modulus is >1600MPa.

13. The current collector of claim 12, wherein: The current collector also includes a protective layer disposed on the surface of at least one of the metal layers.

14. The current collector of claim 13, wherein: The protective layer satisfies at least one of the following conditions: (1) The thickness of the protective layer is 5~100nm; preferably, the thickness of the protective layer is 10~80nm; (2) The material of the protective layer includes one or more of nickel, chromium, nickel-based alloys, copper-based alloys, copper oxide, aluminum oxide, silicon oxide, nickel oxide, chromium oxide, cobalt oxide, graphite, carbon black, copper chromate, copper chromite, carbon nanotubes, carbon nanofibers and graphene.

15. A method of making the current collector of any one of claims 1 to 12, wherein: Includes the following steps: S1. The substrate layer is placed in a vacuum evaporation chamber, and the metal material in the metal evaporation chamber is melted and evaporated at 1100~1600°C, so that the evaporated metal atoms diffuse to at least one side surface of the substrate layer, and are cooled and deposited to form the metal layer on at least one side surface of the substrate layer. S2. At least one side of the product obtained in S1 is subjected to plasma bombardment treatment to obtain the current collector; the process conditions for plasma bombardment treatment are: the gas source is inert gas, the gas flow rate is 10~300mL / min, the working power is 1~20kW, and the treatment time is not less than 5s.

16. A method of making the current collector of any one of claims 13-14, wherein: Includes the following steps: S1. The substrate layer is placed in a vacuum evaporation chamber, and the metal material in the metal evaporation chamber is melted and evaporated at 1100~1600°C, so that the evaporated metal atoms diffuse to at least one side surface of the substrate layer, and are cooled and deposited to form the metal layer on at least one side surface of the substrate layer. S2. At least one surface of the product obtained in S1 is subjected to plasma bombardment treatment; the process conditions for plasma bombardment treatment are: the gas source is inert gas, the gas flow rate is 10~300mL / min, the working power is 1~20kW, and the treatment time is not less than 5s. S3. The protective layer is formed on at least one side surface of the product in S2; the method of forming the protective layer includes one or more of the following methods: physical vapor deposition, chemical vapor deposition, in-situ molding, coating, etc.

17. An electrode sheet, wherein: It includes the current collector as described in any one of claims 1 to 14 or the current collector prepared by the method described in any one of claims 14 to 15, and the electrode active material located on the current collector.

18. A lithium battery cell, wherein: Including the electrode as described in claim 17.

19. A battery pack, wherein: Includes the lithium battery cell as described in claim 18.

20. An electrical device, comprising: Includes the lithium battery cell as described in claim 19 or the battery pack as described in claim 18.

Images