A current collector and a method for manufacturing the same

Abstract

The application provides a current collector and a preparation method thereof. The current collector comprises a metal layer, at least part of the metal layer 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; the Z direction is the thickness direction of the metal layer. The current collector has excellent mechanical properties, can improve the generation of surface defects of the current collector during the rolling process of the pole piece, and has good electrical conductivity. Therefore, the use of the current collector can further optimize the cyclic charge-discharge performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion batteries, and particularly relates to a current collector and a preparation method thereof. BACKGROUND

[0002] At present, the current collector based on high polymer film has been widely concerned and applied in the new energy industry. The preparation of the current collector usually adopts a method of physical vapor deposition (PVD) to deposit a layer of metal on a high polymer film (such as polyester, polyolefin, etc.), so as to prepare a current collector with good conductivity. Compared with the traditional current collector, the current collector based on high polymer film has the characteristics of low cost, light weight, good internal insulation, etc. These characteristics enable the current collector to reduce the cost of the battery and improve the energy density and safety of the battery when the current collector is applied in the battery.

[0003] However, after the preparation of the current collector, the current collector will be further applied to prepare a pole piece. In the preparation process of the pole piece, various processes such as rolling are usually involved, which has higher requirements for the mechanical properties of the current collector. The current collector prepared in the prior art is easily damaged in the preparation process of the pole piece, and has poor mechanical properties, and cannot well meet the preparation process of the pole piece.

[0004] Therefore, how to further improve the mechanical properties of the current collector to improve the stability in the preparation process of the pole piece has important significance for further improving the application and promotion of the current collector in the battery, and also has important significance for further improving the performance of the battery. SUMMARY

[0005] In order to solve the problems and deficiencies in the prior art, the present application provides a current collector and a preparation method thereof. The current collector has excellent mechanical properties, can improve the generation of surface defects of the current collector in the rolling process of the pole piece, and has good conductivity. Therefore, the use of the current collector can be beneficial to further optimize the cyclic charge-discharge performance of the battery.

[0006] According to a first aspect of the present application, a current collector is provided, which comprises a metal layer, at least part of the metal layer 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; the Z direction is the thickness direction of the metal layer.

[0007] In the process of preparing battery pole piece, in order to improve the unit capacity of the pole piece, generally, the pole piece is rolled by rollers. In the rolling process, a large roller pressure is applied to the Z direction (perpendicular to the in-plane direction) of the pole piece, which puts forward higher requirements for the mechanical properties of the current collector in the Z direction. At present, the current collector on the market is generally prepared by PVD (physical vapor deposition) method, the metal grains in the metal layer present columnar crystal structure, the grains in the Z direction are large, and the mechanical properties are poor, which is easy to produce defects in the rolling process, resulting in poor conductivity and reducing the cycle life of the battery. Therefore, in order to further improve the mechanical properties of the current collector in the Z direction, it is necessary to develop a new current collector, so as to promote the application and promotion of the current collector in the battery.

[0008] And the present application controls at least part of the metal layer in the current collector contains dislocation stacking 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. First, this makes at least part of the metal grains in the metal layer in the Z direction has a relatively small average length L, which is less than the thickness of the metal layer, which can improve the anti-rolling capacity of the metal layer as a whole, so that it can have higher pressure capacity when it is rolled in the process of preparing the pole piece. Even under a larger rolling pressure, the current collector will not produce obvious structural defects or cracks, and can still maintain high stability. Second, this part of the dislocation stacking metal grains can provide mutual support force when they are rolled in the process of preparing the pole piece, so as to further improve the pressure capacity of the current collector and further improve the pressure capacity of the pole piece as a whole, and optimize the structural stability of the current collector and the pole piece.

[0009] Regarding the dislocation stacking metal grain structure contained in at least part of the metal layer of the present application, please refer to the description of the present application Figure 1 The crystal planes of this part of dislocation stacking metal grains are connected with each other to form a continuous network structure. Therefore, by designing the metal layer with a special structure, the present application effectively improves the overall stability of the pole piece and the battery, so that the pole piece will not become unstable under the cycle stress due to the structural defects of the current collector in the process of charging and discharging cycle, and the cycle performance of the battery is optimized.

[0010] It should be noted that in the present application, the Z direction in the metal layer refers to the direction of the thickness of the metal layer, 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 thickness direction of the metal layer.

[0011] In addition, in the prior art, the average length L of the metal grains in the Z direction is usually large, and the density of the metal layer is poor, and the conductivity is relatively low. In the present application, the average length L of the dislocation-stacked metal grains in the Z direction contained in at least part of the metal layer of the current collector satisfies the relationship 0

[0012] Preferably, in the longitudinal section of the metal layer, at least part of the metal layer forms a dislocation-stacked metal grain structure, and the grain boundaries between the metal grains form a continuous network structure.

[0013] Preferably, in the longitudinal section of the metal layer, at least part of the metal layer forms a dislocation-stacked metal grain structure, and the grain boundaries between the metal grains form a continuous network structure.

[0014] Preferably, at least part of the metal layer is filled with the metal grains in the Z direction.

[0015] Preferably, the metal layer is composed of the dislocation-stacked metal grains, the grain boundaries between the metal grains form a continuous network structure, and the average length L of the metal grains in the Z direction satisfies the following relationship with the thickness K of the metal layer: 0

[0016] Preferably, in the longitudinal section of the metal layer, the area ratio of the dislocation-stacked metal grains in the metal layer is ≥20%. This ensures that the dislocation-stacked metal grains have a certain area ratio, i.e., the dislocation-stacked metal grains have a sufficient area ratio in the metal layer, which can effectively improve the pressure-bearing capacity of the current collector, i.e., effectively improve the pressure-bearing capacity of the current collector during the rolling process, and improve the stability of the current collector. In addition, the area ratio of the dislocation-stacked metal grains in the metal layer can be tested and calculated as follows: every 5 meters, one longitudinal section of the metal layer is taken, and more than three longitudinal sections are taken for TEM characterization, and the area ratio of all dislocation-stacked metal grains in each longitudinal section of the metal layer to the area of the longitudinal section of the metal layer is calculated, and then the average value is taken. The size of each longitudinal section is (1000-1500) x (800-1200) nm.

[0017] Preferably, the distribution of the misaligned stacked metal grains in the metal layer is uniform. The uniform distribution of the misaligned stacked metal grains in the metal layer means that the pressure bearing capacity of the current collector is uniform at different positions of the current collector, i.e., the pressure bearing capacity at different positions of the current collector is large, thus being beneficial to improve the overall pressure bearing capacity of the current collector, avoid structural defects of the current collector due to poor pressure bearing capacity at some positions of the current collector, and affect the structural stability and service life of the current collector. The uniform distribution is defined as follows: every 5 meters, one longitudinal section of the metal layer is taken, and more than 5 longitudinal sections are taken for TEM characterization. The area ratio of the misaligned stacked metal grains in the metal layer is calculated, and the (maximum value-minimum value) / maximum value in the more than 5 area ratios is less than 50%. Here, the size of each longitudinal section is (1000-1500) x (800-1200) nm.

[0018] Preferably, the current collector further comprises a substrate layer, and the metal layer is arranged on at least one side surface of the substrate layer.

[0019] Preferably, the substrate layer satisfies at least one of the following conditions: the thickness of the substrate layer is 1.0-10 μm; if the thickness of the substrate layer is too thin, the mechanical properties of the current collector as a whole will be reduced, and the stability will be deteriorated, which will deteriorate the cycle performance of the battery; if the thickness of the substrate layer is too thick, the energy density of the battery will be reduced, which is not conducive to the improvement of the comprehensive performance of the battery; the material of the substrate layer comprises one or more of an insulating polymer material, a metal material, an organic fiber material, a carbon material, and an inorganic material; the insulating polymer material comprises one or more of polyethylene terephthalate, polypropylene, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene fluoride, polytetrafluoroethylene, polyphenylene sulfide, polyphenyl ether, polystyrene, polyimide, and polyimide-based urea; the metal material comprises one or more of aluminum, copper, nickel, iron, titanium, silver, gold, cobalt, chromium, molybdenum, and tungsten; the organic fiber material comprises one or more of polyacrylonitrile fiber, poly-p-phenylene benzobisoxazole fiber, polybenzimidazole fiber, and polyimide fiber; the carbon material comprises one or more of conductive carbon black, acetylene black, natural graphite, artificial graphite, mesocarbon microbeads, mesocarbon fibers, vapor-grown carbon fibers, 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. Preferably, the material of the substrate layer comprises 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), polyphenyl ether (PPO), polystyrene (PS), polyimide (PI), and polyimide-based urea (PASC).

[0020] Preferably, the metal layer satisfies at least one of the following conditions: (1) the thickness of the metal layer is 500-2000 nm; if the metal layer is too thin, the conductivity will be poor; if the metal layer is too thick, the current collector prepared will be too thick and heavy, which is not conducive to the improvement of the energy density of the battery; preferably, the thickness of the metal layer is 800-1200 nm; further, if the thickness of the metal layer is controlled within the above range, the conductivity of the current collector and the energy density of the battery can be balanced, and the comprehensive performance of the battery can be optimized; (2) the material of the metal layer comprises one or more of aluminum, copper, silver, gold, nickel, and alloys thereof; preferably, the material of the metal layer comprises one or more of copper, aluminum, and alloys thereof.

[0021] Preferably, the substrate layer is provided with a metal layer 1 and a metal layer 2 on both sides of the substrate layer; the materials of the metal layer 1 and the metal layer 2 can be the same or different.

[0022] Preferably, the above-mentioned current collector Young's modulus is in the range of: > 1600 MPa. Controlling the Young's modulus to be larger can make the current collector have better mechanical properties, further improve the structural stability of the current collector, and improve its pressure-bearing capacity. The Young's modulus is controlled by adjusting the ion bombardment parameters to control the grain refinement degree or the average length L of the grains in the Z direction to meet 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. The higher the mass fraction of particles with 0 < L ≤ 0.8K, the greater the Young's modulus.

[0023] Preferably, the above-mentioned current collector further comprises a protective layer arranged on the surface of at least one metal layer. Adding a protective layer on the surface of the metal layer can prevent the metal layer from being chemically corroded or physically damaged, further improve the electrolyte resistance and mechanical properties of the current collector, and optimize the stability of the current collector.

[0024] Preferably, the protective layer satisfies at least one of the following conditions: (1) the thickness of the protective layer is 5-100 nm; if the protective layer is too thin, it cannot effectively protect the metal layer, which 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; preferably, the thickness of the protective layer is 10-80 nm; further limiting the thickness of the protective layer within the above range is more conducive to balancing the performance of the current collector and the battery; (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 nanometer quantum dots, carbon nanotubes, carbon nanofibers, and graphene.

[0025] Preferably, the material of the protective layer is consistent or inconsistent; the thickness of the protective layer is consistent or inconsistent.

[0026] According to a second aspect of the present application, a method for preparing the current collector is provided, comprising the following steps: S1. placing a substrate layer in a vacuum evaporation cabin, evaporating a metal material in a metal evaporation chamber at 1100-1600 ℃ 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 of the plasma bombardment treatment are as follows: the gas source is an inert gas, the gas flow is 10-300 mL / min, the working power is 1-20 kW, and the treatment time is not less than 5 s. In the method for preparing the current collector provided in the present application, after the metal layers are deposited on both surfaces of the polymer film, the metal layers are subjected to plasma bombardment treatment under specific process conditions, so that the average length of the metal grains in the Z direction of the metal layer is effectively refined, thereby effectively improving the mechanical properties of the current collector in the Z direction, and the current collector is less likely to produce defects during the rolling of the pole piece, and still maintains high stability, which is beneficial to improving the stability of the current collector, the pole piece and the battery, and optimizing the charge-discharge cycle performance of the battery.

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

[0028] Preferably, in S2, the treatment time is 10-60 s.

[0029] Preferably, another method for preparing the current collector is provided, comprising the following steps: S1. placing a substrate layer in a vacuum evaporation cabin, evaporating a metal material in a metal evaporation chamber at 1100-1600 ℃ 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 surface of the product obtained in S1; the process conditions of the plasma bombardment treatment are as follows: the gas source is an inert gas, the gas flow is 10-300 mL / min, the working power is 1-20 kW, and the treatment time is not less than 5 s; S3. forming a protective layer on at least one side surface of the product in S2; the forming method comprises one or more of physical vapor deposition, chemical vapor deposition, in-situ forming, coating and the like.

[0030] Preferably, the vapor deposition method comprises one or more of vacuum evaporation and magnetron sputtering; the chemical vapor deposition comprises one or more of atmospheric pressure chemical vapor deposition and plasma enhanced chemical vapor deposition; the coating method comprises one or more of die coating, blade coating and extrusion coating.

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

[0032] According to a fourth aspect of the present application, a lithium battery cell is provided, comprising the pole piece described above.

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

[0034] According to a sixth aspect of the present application, an electrical equipment is provided, comprising the lithium battery cell or the battery pack described above.

[0035] In summary, in the current collector provided in the present application, by controlling the metal grains in at least part of the metal layer to be misaligned and stacked, and the average length L of the metal grains in the Z direction satisfying the relationship 0 < L ≤ 0.8K with the thickness K of the metal layer, the mechanical properties and electrical conductivity of the current collector are effectively improved, and the charge-discharge cycle performance of the battery is further optimized. BRIEF DESCRIPTION OF DRAWINGS

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

[0037] Figure 2 is the electron microscope image of the aluminum metal layer without plasma bombardment treatment in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0038] In order for those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, not all.

[0039] Example 1

[0040] The current collector of the present embodiment is prepared according to the following steps:

[0041] S1. A PET film with a thickness of 6 μm is placed in a vacuum evaporation cabin, and high-purity aluminum wire (purity greater than 99.99%) in a metal evaporation chamber is melted and evaporated at 1300°C, so that the evaporated aluminum atoms diffuse to both surfaces of the PET film, and under the cooling action of the main roller, two layers of aluminum metal layers with a thickness of 1 μm are formed by cooling and deposition on both surfaces of the PET film;

[0042] S2. The product obtained in S1 is subjected to plasma bombardment treatment; the process conditions for plasma bombardment treatment are as follows: the gas source is argon gas, the gas flow is 100 mL / min, the working power is 10 kW, and the treatment time is 30 s.

[0043] S3. The product obtained in S2 is placed in an oxygen atmosphere and subjected to oxidation treatment for 2 min, so as to form an aluminum oxide protective layer on the two surfaces of the product, with a thickness of 5 nm.

[0044] Example 2

[0045] The example is basically identical with Example 1, except that in S2, the power in the plasma bombardment treatment process is 1 kW.

[0046] Example 3

[0047] The example is basically identical with Example 1, except that in S2, the power in the plasma bombardment treatment process is 20 kW.

[0048] Example 4

[0049] The example is basically identical with Example 1, except that in S2, the treatment time in the plasma bombardment treatment process is 5 s.

[0050] Example 5

[0051] The example is basically identical with Example 1, except that in S2, the treatment time in the plasma bombardment treatment process is 10 s.

[0052] Example 6

[0053] The example is basically identical with Example 1, except that in S2, the treatment time in the plasma bombardment treatment process is 60 s.

[0054] Example 7

[0055] The example is basically identical with Example 1, except that in S2, the argon flow rate in the plasma bombardment treatment process is 10 mL / min.

[0056] Example 8

[0057] The example is basically identical with Example 1, except that in S2, the argon flow rate in the plasma bombardment treatment process is 300 mL / min.

[0058] Example 9

[0059] The example is basically identical with Example 1, except that the metal layer is a copper layer, and the specific preparation process is as follows: a PET film with a thickness of 6 μm is placed in a vacuum evaporation cabin, high-purity copper wire (purity greater than 99.99%) in a metal evaporation chamber is melted and evaporated at 1500°C, so that the metal copper atoms evaporated and escaped diffuse to the two surfaces of the PET film, and under the cooling action of the main roller, the two surfaces of the PET film are cooled and deposited to form two copper metal layers with a thickness of 1 μm.

[0060] Example 10

[0061] The same as Example 1, except that in S2, the power in the plasma bombardment process is 21 kW.

[0062] Example 11

[0063] The same as Example 1, except that in S2, the argon flow rate in the plasma bombardment process is 310 mL / min.

[0064] Comparative Example 1

[0065] The same as Example 1, except that the power in the plasma bombardment process is 0.8 kW.

[0066] Comparative Example 2

[0067] The same as Example 1, except that the plasma bombardment process in S2 is not performed.

[0068] Comparative Example 3

[0069] The same as Example 9, except that the plasma bombardment process in S2 is not performed.

[0070] Comparative Example 4

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

[0072] Comparative Example 5

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

[0074] Comparative Example 6

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

[0076] Test Example

[0077] 1. Experimental construction

[0078] The average length of the crystal grains in the Z direction, the Young's modulus, the surface roughness, the square resistance, and the number of holes in the metal layer of the current collector prepared in all the above examples and comparative examples were tested, and the specific testing methods are as follows:

[0079] (1) Average length of metal grains in the Z direction of the metal layer: The average length of metal grains in the Z direction of the metal layer was analyzed by a method combining a focused ion beam microscope (FIB-SEM) with a field emission transmission electron microscope (TEM). Specifically, the current collector sample was prepared according to the sample preparation requirements of FIB, and then the cross section was ion cut and prepared in the FIB FIB-SEM (Zeiss Gemini2Crossbeam) to prepare a cross section sample with a thickness of about 50 nm. The prepared cross section sample was placed in the TEM (JEM-2100F) for cross section microstructure analysis (cross section size: (1000-1500) x (800-1200) nm). At the same time, the software matched with the TEM was used to count the grains and their sizes, and the average length of the metal grains in the Z direction of the metal layer was calculated.

[0080] (2) Young's modulus: used to characterize the mechanical properties of the current collector in the Z direction. The sample was prepared according to the sample preparation method of an atomic force microscope (AFM), and then the sample was placed in the AFM (Bruker-Dimension Icon) for scanning. The interaction force between the probe and the sample surface was detected, and the Young's modulus was calculated according to the force curve.

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

[0082] (4) Pore: the sample was placed in a surface quality detection system (micro-visual charge-coupled device CCD), and the surface was scanned. Then the optical signal was converted into an electrical signal and transmitted to a computer to count the number of pores per unit area (per square meter) of the current collector sample surface.

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

[0084] 2. Experimental results

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

[0086] Table 1 Test results of the current collector related performance in the examples and comparative examples

[0087]

[0088]

[0089] From the above table 1, it can be seen that in the current collector provided by the present application, the average length L of the metal grains in the metal layer in the Z direction is controlled within a certain smaller numerical range relative to the thickness of the metal layer, so that the current collector has more excellent mechanical properties and electrical conductivity, and at the same time, the current collector can also have better surface roughness, which is beneficial to improve the adhesion between the current collector and the electrode active material, improve the stability of the electrode sheet, and thus optimize the battery cycle performance. And the current collector can also have less pore defects on the surface, so that it can maintain high stability during the charging and discharging cycle process.

[0090] Further, from examples 1, 9 and comparative examples 2, 3, it can be seen that: compared with the traditional current collector, the current collector prepared by the present application has: a. smaller average length of metal grains in the metal layer in the Z direction, which is the result of the increased plasma post-treatment process for grain refinement of the metal layer; b. larger Young's modulus, i.e. better mechanical properties in the Z direction, which is caused by the refinement of metal grains in the Z direction; c. higher surface roughness, which is caused by the bombardment of plasma on the surface of the metal layer, and higher roughness is beneficial to improve the adhesion between the current collector and the electrode active material during the subsequent electrode sheet preparation process. d. The area ratio of the misaligned and stacked metal grains in the metal layer is higher, which is beneficial to improve the mechanical properties of the current collector. Therefore, the current collector provided by the present application has more excellent mechanical properties and electrical conductivity, and can improve the adhesion with the electrode active material, thereby effectively improving the mechanical properties, electrical conductivity and structural stability of the electrode sheet, which is beneficial to the current collector and the electrode sheet to maintain high stability during the battery charging and discharging cycle process, and not easily damaged by the cycle stress, thereby improving the cycle charging and discharging performance of the battery. Further, from Figure 1 and Figure 2 it can be seen that, Figure 1 is the electron microscope image of the aluminum metal layer after plasma bombardment treatment in example 1, Figure 2 is the electron microscope image of the aluminum metal layer without plasma bombardment treatment in the comparative example 2, after plasma bombardment treatment, the average length of the metal grains in the metal layer in the Z direction is obviously effectively reduced, thereby optimizing the mechanical properties and electrical conductivity of the current collector, and optimizing the battery cycle charging and discharging performance. And it can also be seen from example 1 and comparative example 2 that, in comparative example 2, the current collector is not treated by plasma bombardment, resulting in a lower Young's modulus of the current collector, which significantly reduces the structural strength and stability of the current collector, and deteriorates the performance of the current collector.

[0091] From Examples 1-3, 10, Comparative Example 1, 4, it can be seen that: increasing the power of the plasma bombardment treatment, the prepared current collector: a. the average length of the metal grains in the metal layer in the Z direction decreases, which is due to the increase of the energy of the plasma post-treatment, which promotes the refinement of the grains; b. the Young's modulus is larger, that is, 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 increase of the power of the plasma post-treatment, which makes the bombardment of the plasma on the surface of the metal layer more intense. And it can be further seen that d. if the power of the plasma bombardment treatment is too low, the performance improvement is not obvious, and if the power is too high, holes will be produced on the surface; and if the power of the plasma bombardment treatment is too low, the area ratio of the misaligned stacked metal grains in the metal layer in the longitudinal section of the metal layer will also decrease, which is not conducive to the improvement of the mechanical properties of the current collector.

[0092] From Examples 1, 4-6 and Comparative Example 5, it can be seen that: increasing the time of the plasma bombardment treatment, the prepared current collector: a. the average size of the metal grains in the metal layer in the Z direction decreases, which is due to the extension of the plasma bombardment treatment time, which promotes the refinement of the grains; b. the Young's modulus is larger, that is, 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 increase of the time of the plasma post-treatment, which makes the bombardment of the plasma on the surface of the metal layer more intense; d. if the time of the post-treatment is too short, the area ratio of the misaligned stacked metal grains in the metal layer in the longitudinal section of the metal layer will decrease, which is not conducive to the improvement of the performance.

[0093] From Examples 1, 7, 8, 10 and Comparative Example 6, it can be seen that: increasing the gas flow of the post-treatment, the prepared current collector: a. the average size of the metal grains in the metal layer in the Z direction decreases, which is due to the increase of the plasma post-treatment flow, which can increase the number of plasma, thereby promoting the refinement of the grains; b. the Young's modulus is larger, that is, 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 increase of the plasma post-treatment flow, which can increase the number of plasma, thereby making the bombardment of the plasma on the surface of the metal layer more intense. And it can be further seen that d. if the gas flow of the post-treatment is too low, the generated plasma is too low, the area ratio of the misaligned stacked metal grains in the metal layer will decrease, which is not conducive to the improvement of the performance.

[0094] And further from the examples 1-11 and comparative examples 1, 4-6 can be seen, even after a certain plasma bombardment treatment, but the area percentage of misoriented stacked metal grains in the metal layer in comparative examples 1, 4-6 is low, lower than 20%, compared with other examples, the current collector Young's modulus in these comparative examples is low, representing that the mechanical properties are low, so the overall performance of the current collector is low.

[0095] The above examples are only used to illustrate the technical solutions of the present application, but not limit the protection scope of the present application. Although the present application has been described in detail with reference to the above examples, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently, and these modifications or replacements are within the protection scope of the present application.

Claims

1. A current collector, characterized in that: The material includes a metal layer and a substrate layer. The metal layer is disposed on at least one side surface of the substrate layer. At least a portion of the metal layer includes displaced and stacked metal grains. 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; In the longitudinal section of the metal layer, the area of ​​the misaligned and stacked metal grains in the metal layer is ≥20%; The Young's modulus of the current collector in the Z direction is >1600 MPa.

2. The current collector as described in claim 1, characterized in that: At least a portion of the metal layer is filled with the metal grains in the Z direction.

3. The current collector as described in claim 1, characterized in that: The metal layer is composed of 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; The Z direction is the direction of the thickness of the metal layer.

4. The current collector as described in claim 1, characterized in that: The misaligned stacked metal grains are uniformly distributed in the metal layer.

5. The current collector as described in claim 1, characterized in that: The substrate layer satisfies at least one of the following conditions: The thickness of the substrate layer is 1.0–10 μm; The material of the substrate layer includes one or more of the following: 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 material includes 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. The inorganic material includes one or more of oxides, carbides, silicides, and nitrides.

6. The current collector as described in claim 5, characterized in that: 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.

7. The current collector as described in claim 1, characterized in that: 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.

8. The current collector as described in claim 7, characterized in that: 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.

9. The current collector as described in claim 1, characterized in that: 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.

10. The current collector as described in claim 9, characterized in that: The current collector also includes a protective layer disposed on the surface of at least one of the metal layers.

11. The current collector as described in claim 10, characterized in that: The protective layer satisfies at least one of the following conditions: (1) The thickness of the protective layer is 5-100 nm; (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.

12. The current collector as described in claim 11, characterized in that: The thickness of the protective layer is 10–80 nm.

13. A method for preparing a current collector as described in any one of claims 1 to 9, characterized in that: 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 10-300 mL / min, the working power is 1-20 kW, and the treatment time is not less than 5 s.

14. A method for preparing a current collector as described in any one of claims 10 to 12, characterized in that: 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 10-300 mL / min, the working power is 1-20 kW, and the treatment time is not less than 5 s. 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 physical vapor deposition, chemical vapor deposition, in-situ molding, and coating methods.

15. An electrode sheet, characterized in that: It includes the current collector as described in any one of claims 1 to 12 or the current collector prepared by the method described in any one of claims 13 to 14, and the electrode active material located on the current collector.

16. A lithium battery cell, characterized in that: Includes the electrode as described in claim 15.

17. A battery pack, characterized in that: Includes the lithium battery cell as described in claim 16.

18. An electrical appliance, characterized in that: Includes the lithium battery cell as described in claim 16 or the battery pack as described in claim 17.

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