Current collector and preparation method thereof, pole piece and preparation method thereof, and battery

Abstract

The invention provides a current collector and a preparation method thereof, a pole piece and a preparation method thereof, and a battery, the surface of the current collector is provided with a porous structure, and the pore inner wall of the porous structure comprises a nitrogen-containing functional group and an oxygen-containing functional group. The surface area and the porosity of the porous structure are increased, the negative electrode material is coated in the porous structure and can form a mechanical interlocking structure with the negative electrode coating, and the adhesive force of the current collector and the negative electrode coating is increased. Active functional groups (nitrogen functional groups and oxygen-containing functional groups) generated by plasma treatment on the inner walls of the pores can generate interaction of hydrogen bonds and covalent bonds with a filling material, so that the binding force between the current collector and the coating is further enhanced, and the problem of stripping or falling of a pole piece is avoided; and the cycle life and the overall performance of the battery are improved.

Description

Technical Field

[0001] This application relates to the field of batteries, and particularly to a current collector, a preparation method thereof, a pole piece, a preparation method thereof, and a battery. Background Art

[0002] In a battery, the current collector plays a crucial role. The current collector is a key component that conducts electrons inside the battery to the external circuit, and is usually made of a metal material (such as aluminum foil for the positive electrode and copper foil for the negative electrode). The current collector is in close contact with the pole piece (i.e., a thin film coated with active material), and ensures the high efficiency and stability of the battery through effective current conduction.

[0003] During the battery manufacturing process, the bonding force between the active material and the current collector is very critical. If the two are not firmly bonded, it may lead to insufficient stripping force of the pole piece. When the stripping force is insufficient, during the production process of the pole piece, it is inevitable to cause powder falling off the negative pole piece, resulting in problems such as large self-discharge, poor short-circuit test, and poor soldering, thus affecting the cycle stability and capacity retention of the finished battery, and further shortening the service life of the battery.

[0004] Therefore, how to ensure sufficient bonding force between the active material and the current collector is crucial for improving the performance of the battery. Summary of the Invention

[0005] This application provides a current collector, a preparation method thereof, a pole piece, a preparation method thereof, and a battery, so as to improve the bonding force between the current collector and the active material, and further improve the stripping force of the pole piece and the cycle performance of the battery.

[0006] In the first aspect, this application provides a current collector, on the surface of which a porous structure is provided, and the inner wall of the pores of the porous structure includes nitrogen-containing functional groups and oxygen-containing functional groups.

[0007] Optionally, the inclination angle between the porous structure and the surface of the current collector is 30° - 60°.

[0008] Optionally, the porous structure is conical or V-shaped.

[0009] Optionally, the length of the porous structure is 2 - 6 μm.

[0010] Optionally, the surface roughness Ra of the pore wall of the porous structure is 1.5 - 2.5 μm.

[0011] In the second aspect, this application provides a preparation method of a current collector, which is applied to the current collector according to any one of claims 1 - 5, and the preparation method includes:

[0012] Preparing a porous structure on the surface of the current collector by picosecond laser;

[0013] By radio frequency plasma treatment, nitrogen-containing functional groups and oxygen-containing functional groups are generated on the surface of the porous structure, and the gas used in the radio frequency plasma treatment is an N2 / O2 mixed gas.

[0014] In a third aspect, the present application provides an electrode sheet, comprising: the current collector according to any one of the first aspects.

[0015] Optionally, a conductive transition layer is provided on the surface of the current collector, and the conductive transition layer comprises graphene quantum dots and carbon nanotubes.

[0016] Optionally, the thickness of the conductive transition layer is 100 - 1000 nm.

[0017] Optionally, the peel force of the electrode sheet is greater than 15 N / m.

[0018] In a fourth aspect, the present application provides a method for preparing an electrode sheet, which is applied to the electrode sheet according to any one of the third aspects, and the preparation method comprises:

[0019] The composite slurry of graphene quantum dots and carbon nanotubes is filled into the porous structure on the surface of the fluid by vacuum impregnation, and the pressure of the vacuum impregnation method is 50 - 100 kPa;

[0020] Anneal for 5 - 15 minutes, and the annealing temperature is 120 - 180 °C;

[0021] Coat the negative electrode active material, dry and then roll press to obtain the electrode sheet.

[0022] In a fifth aspect, the present application provides a battery, comprising the electrode sheet according to any one of the third aspects.

[0023] A current collector provided by the present application, its preparation method, an electrode sheet, its preparation method and a battery. The surface of the current collector is provided with a porous structure, and the inner wall of the pores of the porous structure comprises nitrogen-containing functional groups and oxygen-containing functional groups. By increasing the surface area and porosity, the negative electrode material is coated in the porous structure, and a mechanical interlocking structure can be formed with the negative electrode coating, increasing the adhesion between the current collector and the negative electrode coating. The active functional groups (nitrogen functional groups and oxygen-containing functional groups) generated by plasma treatment on the inner wall of the pores can interact with the filled materials to generate hydrogen bonds and covalent bonds, further enhancing the bonding force between the current collector and the coating, avoiding the peeling or falling off problem of the electrode sheet, and thus improving the cycle life and overall performance of the battery. Description of the Drawings

[0024] The drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0025] Figure 1 Schematic structure of the current collector provided by this application Figure 1 ;

[0026] Figure 2 Schematic structure of the current collector provided by this application Figure 2 ;

[0027] Figure 3 Schematic structure of the current collector provided by this application Figure 3 ;

[0028] Figure 4 Schematic diagram of the structure of the electrode sheet provided by this application.

[0029] Through the above-mentioned drawings, specific embodiments of this application have been shown, and there will be more detailed descriptions hereinafter. These drawings and written descriptions are not intended to limit the scope of the concept of this application in any way, but to illustrate the concept of this application to those skilled in the art by referring to specific embodiments. Detailed Description of the Invention

[0030] Here, exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. On the contrary, they are merely examples of devices and methods consistent with some aspects of this application as detailed in the appended claims.

[0031] During the battery manufacturing process, the bonding force between the active material and the current collector is very crucial. If the two are not firmly bonded, it may lead to insufficient stripping force of the electrode sheet.

[0032] The preparation process of the negative electrode sheet in the traditional process is: stirring, coating, cold pressing and slitting. The stripping force of the prepared negative electrode sheet is relatively low (about 5 N / m, or less than 5 N / m). During the entire production process, it is inevitable to cause powder dropping of the negative electrode sheet, resulting in problems such as large self-discharge, poor short-circuit test, and poor soldering, thus affecting the performance of the finished battery. For the positive electrode sheet, the stripping force is relatively higher than that of the negative electrode, and the powder dropping phenomenon is not serious.

[0033] Therefore, how to improve the stripping force of the negative electrode sheet is an urgent problem to be solved, and the key to improving the stripping force of the negative electrode sheet is to improve the bonding force between the negative current collector (copper foil) and the active material. The current main methods include:

[0034] 1. Chemical etching method.

[0035] Etch the surface of the copper foil with a chemical solution to form a rough surface to enhance the adhesion to the active material.

[0036] However, this method has the following problems: During the chemical etching process, the thickness of the copper foil may be uneven, resulting in a decrease in the conductivity of the current collector, which in turn affects the performance of the battery. Chemical etching may cause damage to the surface of the copper foil, reducing the conductivity, usually resulting in a loss of about 10-15%, which directly affects the power density and overall efficiency of the battery. During the chemical etching process, it is difficult to control the morphology of the microstructure, which may affect the adhesion quality of subsequent coatings and active materials.

[0037] 2. Sandblasting / Electrodeposition Roughening

[0038] The sandblasting or electrodeposition roughening method enhances the surface roughness through physical treatment of the copper foil surface to improve the adhesion of the active material.

[0039] However, this method has the following defects: During the sandblasting or electrodeposition process, metal debris or other impurities will be introduced, which will affect the purity of the copper foil and may reduce the performance of the battery. To remove these impurities, additional cleaning processes are usually required, increasing the production cost and complexity. In addition, although the surface roughness has been improved, the Ra value of the roughness is usually limited, usually not exceeding 1.0 μm, which may not provide sufficient bonding force for some high-performance batteries.

[0040] 3. Physical Coating Method

[0041] The physical coating method improves the bonding force with the active material by coating a transition layer (alloy layer) on the copper foil surface.

[0042] However, this method also has the following problems: The bonding force between the transition layer and the copper foil is weak. Especially during long-term cycling, due to the volume expansion of the battery, the coating is prone to delamination, resulting in insufficient bonding force between the coating and the copper foil, affecting the cycle stability and performance of the battery. The negative electrode material will undergo volume expansion during charge and discharge, which will increase the interfacial stress between the coating and the current collector, easily causing the transition layer to peel off or delaminate.

[0043] In view of the defects of the above methods, the present application proposes a method for preparing a current collector, which synergistically processes the current collector through laser micro-nano structure processing and plasma functionalization. On the one hand, picosecond laser is used to prepare a conical hole / V-groove array on the surface of the current collector. The conical hole / V-groove forms a physical anchor with the coating through geometric constraint effect, forming a mechanically interlocked structure to improve the bonding force. On the other hand, combined with nitrogen-oxygen plasma activation, nitrogen / oxygen functional groups are generated on the inner wall of the hole structure to enhance the chemical bonding between the current collector and the active material. The mechanical interlock and chemical bonding of the coating are synergistically enhanced. The peel force of the obtained pole piece is increased to more than 15 N / m, the conductivity loss <2%, and the capacity retention rate after 2000 cycles >85%. It is especially suitable for high-energy density power batteries and flexible battery fields.

[0044] It should be noted that the above preparation method can be used to prepare not only the negative electrode current collector, but also the positive electrode current collector.

[0045] The first aspect of the present application provides a current collector. Referring to Figure 1 , a porous structure is provided on the surface of the current collector, and the inner wall of the pores of the porous structure includes nitrogen-containing functional groups and oxygen-containing functional groups.

[0046] By increasing the surface area and porosity, the negative electrode material is coated in the porous structure, and a mechanical interlocking structure can be formed with the negative electrode coating, increasing the adhesion between the current collector and the negative electrode coating. The active functional groups (nitrogen functional groups and oxygen-containing functional groups) treated by plasma can interact with the negative electrode binder (such as CMC, PVDF), or the negative electrode active material, or the conductive transition layer, generating hydrogen bond and covalent bond interactions, further enhancing the binding force between the current collector and the negative electrode coating, and avoiding the problems of peeling or falling off during battery use.

[0047] Due to the enhancement of mechanical interlocking and chemical bonds, the binding force between the current collector and the negative electrode coating is greatly improved, which directly increases the peel force, that is, the negative electrode material is not easily detached from the current collector during the production of the electrode sheet and the battery cycling process, thereby improving the cycle life and overall performance of the battery.

[0048] To further increase the effect of mechanical interlocking, the porous structure on the current collector can be inclined, which further increases the adhesion between the current collector and the negative electrode coating.

[0049] In some embodiments, referring to Figure 2 , the inclination angle of the porous structure with respect to the surface of the current collector is 30° - 60°. Here, the inclination angle refers to the angle between the line connecting the vertex of the porous structure to the center of the pore surface and the plane where the surface of the current collector is located. Exemplarily, the inclination angle can be 30°, 35°, 40°, 45°, 50°, 55°, 60° or any range composed of any two of the above values.

[0050] The inclined porous structure is periodically arrayed or evenly dispersed irregularly.

[0051] In some embodiments, referring to Figure 3 , the porous structure can be divided into two directions, one porous structure is inclined to the left and the other is inclined to the right. This can prevent overall slipping and improve the effect of mechanical interlocking.

[0052] In some embodiments, the length of the porous structure is 2 - 6 μm, and the length can be 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 6 μm or any range composed of any two of the above values.

[0053] In some embodiments, the porous structure is conical. In a specific implementation, the pore diameter of the porous structure on the surface of the current collector is 1-3 μm, the length is 2-6 μm, and the pore spacing is 10-20 μm. Exemplarily, the pore diameter can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, or a range composed of any two of the above values. The pore spacing can be 10 μm, 12 μm, 13 μm, 15 μm, 16 μm, 18 μm, 20 μm, or a range composed of any two of the above values.

[0054] In some embodiments, the porous structure is V-shaped. In a specific implementation, the width of the V shape is 2-4 μm and the length is 2-6 μm.

[0055] The above V-shaped holes or conical holes can be inclined.

[0056] The inner wall of the holes of the current collector includes nitrogen functional groups and oxygen-containing functional groups, and the surface roughness Ra of the inner wall of the porous structure is 1.5-2.5 μm. Exemplarily, the roughness Ra can be 1.5 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.3 μm, 2.5 μm, or a range composed of any two of the above values.

[0057] The second aspect of the present application provides a method for preparing a current collector, and this preparation method can prepare the current collector of any item in the first aspect. The preparation method includes the following steps:

[0058] Step 1: Prepare a porous structure on the surface of the current collector by picosecond laser.

[0059] Equipment: Picosecond laser (wavelength 532 / 1064 nm, pulse width ≤ 15 ps). Parameters: Power density: 5-20 J / cm 2 ; Scanning speed: 300-1200 mm / s; Hole type design: Conical hole (pore diameter 1-3 μm, depth 2-6 μm, pore spacing 10-20 μm) or V-shaped groove (width 2-4 μm, depth 2-6 μm); Surface roughness: Ra 1.5-2.5 μm.

[0060] Step 2: Generate nitrogen-containing functional groups and oxygen-containing functional groups on the surface of the porous structure by radio frequency plasma treatment, and the gas used for radio frequency plasma treatment is a N2 / O2 mixed gas.

[0061] Among them, the ratio of nitrogen to oxygen in the radio frequency plasma treatment mixed gas is 2:1-5:1. Exemplarily, the ratio of nitrogen to oxygen can be 2:1, 3:1, 4:1, 5:1, or a range composed of any two of the above values. The power of the radio frequency plasma treatment is 150-250 W, the air pressure is 10-50 Pa, and the treatment time is 30-90 seconds.

[0062] The third aspect of the present application provides a pole piece, which uses the current collector according to any one of the first aspect. The pole piece can be a positive pole piece or a negative pole piece.

[0063] The following introduces the negative pole piece prepared using this current collector.

[0064] In some embodiments, a negative active layer is directly provided on the current collector (copper foil). If the negative active layer is directly provided, hydrogen bonds / covalent bonds are generated between the active functional groups on the inner wall of the porous structure and the negative binder (such as CMC, PVDF).

[0065] In some embodiments, referring to Figure 4 , a conductive transition layer is provided on the surface of the current collector, and a negative active layer is provided on the conductive transition layer. Among them, the conductive transition layer fills the porous structure, and the conductive transition layer includes graphene quantum dots and carbon nanotubes. Graphene quantum dots and carbon nanotubes are rich in functional groups, and can generate hydrogen bonds and covalent bonds with the nitrogen-containing functional groups and oxygen-containing functional groups on the pore wall. CNTs vertically penetrate the pores to form a "rivet" structure, improving the in-plane conductivity. Since the carbon nanotubes and graphene quantum dots in the conductive transition layer can provide better electron conduction channels and stronger adhesion, the structure of the negative active layer is more stable, which helps to resist the volume expansion and contraction of the battery during charge and discharge, reduce battery aging and performance degradation, and thus improve the cycle life of the battery.

[0066] Figure 4 The inclination angles of the porous structures in Figure 3 all incline to one side. In some other embodiments, a conductive transition layer is provided on the current collector shown in Figure 3 .

[0067] In some embodiments, the thickness of the conductive transition layer is 100 - 1000 nm. Exemplarily, the thickness can be 100 nm, 200 nm, 400 nm, 600 nm, 800 nm, 1000 nm, or the range composed of any two of the above values.

[0068] In some embodiments, the peel strength of the pole piece obtained by using the porous structure and plasma treatment is greater than 15 N / m. The effect of improving the peel strength of the scheme with the conductive transition layer is better than that of the scheme without the conductive transition layer.

[0069] The copper foil prepared by the above method of laser micro-nano structure processing and plasma functionalization has a uniform thickness, can avoid the problem of uneven copper foil thickness caused by the traditional chemical etching method, and improve the conductivity. Etching to create depressions on the surface of the copper foil will cause a 10 - 15% loss in the conductivity of the battery, while the conductivity loss of the battery prepared by this method is less than 2% (based on the original copper foil benchmark of 100% IACS).

[0070] The fourth aspect of the present application provides a method for preparing a negative electrode sheet, and this preparation method is used to produce the electrode sheet provided in the third aspect.

[0071] For a negative electrode sheet without a conductive transition layer, the preparation method can have the following several ways.

[0072] In one implementation, the negative electrode active material can be directly coated on any of the copper foils in the first aspect above, and after drying, it is roll-pressed to obtain the electrode sheet.

[0073] In another implementation, it includes the following steps:

[0074] Step 1: Spray a solvent on the upper surface of any of the copper foils in the first aspect above; use the solvent to adsorb the negative electrode material on the copper foil, reducing the usage amounts of the binder, dispersant, and surfactant, saving raw material costs; use the solvent and the method of mechanical roll-pressing to force the negative electrode active material and the copper foil to closely combine together and generate irreversible deformation, constructing a mechanical interlocking structure at the microporous structure and enhancing the adhesion strength of the active material.

[0075] Step 2: Uniformly spray the negative electrode material on the surface of the copper foil and conduct the first baking and drying. The usage amount of the negative electrode material is 10 - 100 g / m 2 ; The first baking and drying is to control the amount of solvent after coating the negative electrode material to prevent the phenomenon that too much solvent takes away the negative electrode material during roll-pressing.

[0076] Step 3: Conduct roll-pressing treatment on the copper foil; the roll-pressing treatment is to force the negative electrode material and the copper foil to closely combine, and also to make the negative electrode material and the aluminum foil undergo irreversible deformation, constructing a mechanical interlocking structure at the porous structure and enhancing the adhesion between the coating and the copper foil.

[0077] Step 4: Conduct the second baking and drying on the aluminum foil, and then the negative electrode sheet is obtained.

[0078] Optionally, in step 1, the usage amount of the solvent is: 10 - 100 ml / m 2 .

[0079] Optionally, in step 1, the solvent is N-methylpyrrolidone.

[0080] Optionally, in step 2, the temperature of the first baking and drying is 30 - 100 °C, and the time is 10 - 60 min.

[0081] Optionally, in step 2, the negative electrode material is a mixture of graphite (natural, artificial), carbon black, or carbon nanotubes, binder (SBR, CMC), etc.

[0082] Optionally, in step 3, the roll-pressing pressure is 10 - 200 T, and the roll-pressing speed is 50 - 300 m / min.

[0083] Optionally, in step 4, the temperature of the second baking and drying is 60 - 150 °C, and the time is 10 - 100 min.

[0084] For the negative electrode sheet including a conductive transition layer, the preparation method includes the following steps:

[0085] Step 1: The composite slurry of graphene quantum dots and carbon nanotubes is filled into the pores of the porous structure by vacuum impregnation method, and the pressure of the vacuum impregnation method is 50 - 100 kPa; wherein, the mass ratio of graphene quantum dots to carbon nanotubes is 3:1 - 5:1.

[0086] Step 2: Anneal for 5 - 15 minutes, and the annealing temperature is 120 - 180 °C;

[0087] Step 3: Coating the negative electrode active material, drying and then rolling to obtain the electrode sheet.

[0088] In some embodiments, secondary drying is performed after rolling.

[0089] Through the above preparation method, the conductive transition layer is filled in the porous structure and has a certain thickness on the surface layer of the copper foil. The active functional groups on the surface of the copper foil and the inner wall of the pores can generate hydrogen bonds, van der Waals forces or covalent bond forces with the graphene quantum dots (GQDs) and carbon nanotubes (CNTs) in the conductive transition layer, enhancing the bonding force between the conductive transition layer and the current collector.

[0090] The fifth aspect of the present application provides a battery including the electrode sheet prepared by any one of the above fourth aspects.

[0091] Hereinafter, the present application will be further introduced through specific examples.

[0092] Example 1

[0093] 1. Laser drilling of copper foil:

[0094] Picosecond laser (wavelength 1064 nm, power density 12 J / cm 2 , scanning speed 800 mm / s) is used to process a conical hole array (hole diameter 8 μm, depth 6 μm, pitch 25 μm). The conical holes have no inclination and are drilled vertically.

[0095] 2. Plasma treatment after drilling:

[0096] N2 / O2 = 4:1, power 200 W, time 60 s, air pressure 30 Pa.

[0097] 3. After plasma treatment, the negative electrode active material is coated, dried and then rolled to obtain the electrode sheet. The negative electrode active material is a mixture of graphite (natural, artificial), carbon black or carbon nanotubes, and binders (SBR, CMC).

[0098] Example 2

[0099] The difference from Example 1 is that a conductive transition layer is coated before coating the negative electrode active material.

[0100] In the conductive transition layer, the GQDs / CNTs composite slurry (mass ratio 4:1) is vacuum impregnated (-80 kPa) and annealed at 150 °C for 8 minutes.

[0101] Example 3

[0102] The difference from Example 1 is that the inclination angle of the tapered hole is 30°.

[0103] Example 4

[0104] The difference from Example 1 is that the inclination angle of the tapered hole is 45°.

[0105] Example 5

[0106] The difference from Example 1 is that the inclination angle of the tapered hole is 60°.

[0107] Example 6

[0108] The difference from Example 2 is that the inclination angle of the tapered hole is 30°.

[0109] Example 7

[0110] The difference from Example 2 is that the inclination angle of the tapered hole is 45°.

[0111] Example 8

[0112] The difference from Example 2 is that the inclination angle of the tapered hole is 60°.

[0113] Comparative Example 1

[0114] The difference from Example 1 is that a flat copper foil is used and no punching or plasma treatment is performed.

[0115] Comparative Example 2

[0116] The difference from Example 1 is that the inclination angle of the tapered hole is 75°.

[0117] Comparative Example 3

[0118] The difference from Example 1 is that the inclination angle of the tapered hole is 15°.

[0119] Comparative Example 4

[0120] The difference from Example 2 is that the inclination angle of the tapered hole is 75°.

[0121] Comparative Example 5

[0122] The difference from the second embodiment is that the inclination angle of the conical hole is 15°.

[0123] Test example

[0124] 1. Measurement method of the initial peel force of the electrode sheet:

[0125] Cut the electrode sheet into strips of 20 mm × 150 mm, ensuring that the coating is not damaged. Use tape to bond the coating, and roll it with a roller to remove air bubbles. Test the peel force through a universal testing machine with a fixture spacing of 50 mm, a peel angle of 180°, and a speed of 100 mm / min. The peel force is the average value of the stable section of the curve.

[0126] 2. Measurement of the 2000-cycle retention rate after the battery is made

[0127] After 2000 charge and discharge cycles, record the capacity of the battery. Calculate the percentage of the capacity of the battery after cycling to the initial capacity to determine the 2000-cycle retention rate.

[0128] The test results are shown in Table 1 below.

[0129]

[0130] According to the above test results, by comparing the peel force data of the first embodiment and the first comparative example, it can be seen that through the porous structure and plasma treatment, the peel force of the negative electrode sheet is significantly improved, from 6.7 N / m to 15.1 N / m, and the cycle life of the battery after being made is also significantly improved. The experimental data shows that the porous structure and the measures of forming oxygen-containing functional groups and nitrogen-containing functional groups on the pore wall surface by plasma treatment can improve the interlayer bonding force, increase the peel force, and enhance the cycle life of the battery.

[0131] By comparing the peel force data of the first embodiment and the second embodiment, it can be seen that the peel force effect is better after adding the conductive transition layer.

[0132] Through the peel force data of the third embodiment, the fourth embodiment, the fifth embodiment, the second comparative example and the third comparative example, it can be determined that when the inclination angle of the porous structure is less than 30° or greater than 75°, the effect becomes worse. Similarly, in the comparison with the addition of the conductive transition layer, when the inclination angle of the porous structure is less than 30° or greater than 75°, the effect also becomes worse.

[0133] Perform strength tests on the copper foils of the first comparative example and the first embodiment above. The test results are shown in Table 2 below.

[0134] Performance Index Comparative Example 1 Example 1 Rate of Change Tensile Strength (MPa) 325±8 312±10 -4.0％ Yield Strength (MPa) 285±6 275±8 -3.5％ Elongation at Break (%) 12.5±0.3 11.8±0.4 -5.6％

[0135] As can be seen from the data in Table 2, the mechanical property degradation rate of the copper foil after laser drilling and plasma functionalization is < 10% (tensile / yield strength), and the elongation at break degradation is < 8%, which is significantly better than the chemical etching process (the traditional etching strength loss > 15%).

[0136] The strength loss is mainly due to material removal (hole structure processing), but by optimizing the laser energy density (5 - 20 J / cm 2 ), the heat affected zone (HAZ) is controlled to ≤ 5 μm to avoid brittle fracture caused by grain coarsening.

[0137] Finally, it should be noted that: After considering the specification and practicing the invention disclosed herein, those skilled in the art will readily think of other embodiments of the present invention. The present invention is intended to cover any variations, uses, or adaptations of the present invention, which follow the general principles of the present invention and include the common general knowledge or conventional technical means in the technical field not disclosed in the present invention. It is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A current collector, characterized in that, The surface of the current collector is provided with a porous structure, and the inner wall of the pores of the porous structure includes nitrogen-containing functional groups and oxygen-containing functional groups.

2. The current collector according to claim 1, characterized in that, The inclination angle between the porous structure and the surface of the current collector is 30°-60°.

3. The current collector according to claim 2, wherein, The porous structure is conical or V-shaped.

4. The current collector according to any one of claims 1 to 3, characterized in that, The length of the porous structure is 2-6 μm; and / or, the surface roughness Ra of the pore wall of the porous structure is 1.5-2.5 μm.

5. A method for preparing a current collector, characterized in that, The preparation method is applied to the current collector according to any one of claims 1-4, and the preparation method includes: Preparing a porous structure on the surface of the current collector by picosecond laser; Generating nitrogen-containing functional groups and oxygen-containing functional groups on the surface of the porous structure by radio frequency plasma treatment, and the gas used for the radio frequency plasma treatment is an N2 / O2 mixed gas.

6. A pole piece, characterized in that, including: The current collector according to any one of claims 1-4.

7. The pole piece according to claim 6, characterized in that, A conductive transition layer is provided between the current collector and the negative electrode material, and the conductive transition layer includes graphene quantum dots and carbon nanotubes.

8. The pole piece according to claim 7, characterized in that, The thickness of the conductive transition layer is 100-1000 nm; and / or, the peel force of the electrode sheet is greater than 15 N / m.

9. A method for preparing a pole piece, characterized in that, The preparation method is applied to the electrode sheet according to claim 7 or 8, and the preparation method includes: Filling the porous structure on the surface of the current collector with the composite slurry of graphene quantum dots and carbon nanotubes by vacuum impregnation method, and the pressure of the vacuum impregnation method is 50-100 kPa; Annealing for 5-15 minutes, and the annealing temperature is 120-180 °C; Coating the negative electrode active material, drying and then rolling to obtain the electrode sheet.

10. A battery, characterized in that, including the electrode sheet according to any one of claims 6-8.

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