Composite current collector, method for preparing the same and use thereof

Abstract

The present application relates to a kind of composite current collector and its preparation method and application.The composite current collector includes polymer base film layer and the metal layer on at least one surface of the polymer base film layer, the polymer base film layer includes the metal embedding layer in contact with the metal layer;The strength factor of the composite current collector is the strength factor of the present application is regulated in a certain range, can make the tensile strength of composite current collector relative to the tensile strength of base film significantly improve the degree of promotion.In addition, the composite current collector of the present application also has good peel strength and low square resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic components, and more particularly, to a composite current collector and a preparation method and application thereof. BACKGROUND

[0002] The composite current collector is a high-performance conductive material, which is usually composed of two layers of metal (such as copper) and one layer of polymer substrate (such as PET, PP, PI, etc.). As a substitute for electrolytic copper foil for lithium batteries, the composite current collector has the characteristics of low cost, lightness, high safety performance, and high energy density, and is also widely used in the fields of flexible electronic devices, thin film capacitors, electromagnetic shielding, etc.

[0003] Although the composite current collector performs well in many aspects, its peeling strength between the metal layer and the base film and the tensile strength still need to be further improved. Since the composite current collector belongs to a composite structure, good peeling strength is a basic requirement. During battery manufacturing and daily use, the composite current collector needs to withstand various forces such as internal electrolyte pressure and external mechanical impact of the battery, so the tensile strength of the composite current collector needs to be improved.

[0004] The tensile strength of the composite current collector is affected by the tensile strength of the base film itself and the composite process. Among them, the existing composite process is easy to damage the base film, so that the tensile strength of the composite current collector has no obvious improvement compared with the base film, or even lower than the base film. If the tensile strength of the composite current collector is lower than that of the base film, it will have a negative impact on the yield of the product, and may also affect the durability and safety of high-performance batteries.

[0005] Patent CN117497687A discloses a preparation method of a composite copper foil current collector, which adopts a copper layer sputtered by a magnetron sputtering process. The bonding force between the copper layer and the polymer base film is not good, and the high temperature in the magnetron sputtering process will cause the polymer base film to be damaged by perforation, thereby causing the tensile strength of the composite copper foil current collector to have no obvious improvement compared with the base film. SUMMARY

[0006] The primary object of the present application is to overcome the problems of the existing composite current collector, i.e., the tensile strength of the composite current collector has no obvious improvement compared with the base film, and the peeling strength of the composite current collector needs to be further improved, and to provide a composite current collector.

[0007] A further object of the present application is to provide a preparation method of the composite current collector.

[0008] A further object of the present application is to provide the application of the above-mentioned composite current collector in the preparation of a lithium ion battery negative electrode.

[0009] The above-mentioned objects of the present application are achieved by the following technical solutions:

[0010] A composite current collector includes a polymer base film layer and a metal layer disposed on at least one surface of the polymer base film layer, the polymer base film layer including a metal-embedded layer in contact with the metal layer;

[0011] The strength factor of the composite current collector is The

[0012] wherein D is the thickness of the metal layer, D0 is the thickness of the polymer base film layer, and d is the thickness of the metal-embedded layer.

[0013] In the present application, the thickness D of the metal layer, the thickness D0 of the polymer base film layer, and the thickness d of the metal-embedded layer are in the same unit. The metal-embedded layer refers to a layer in which the pores of the polymer base film in the polymer base film layer are embedded with metal. The thickness d of the metal-embedded layer refers to the shortest distance from the deepest copper embedded in the polymer base film to the surface of the polymer base film layer.

[0014] The inventors of the present application found that by regulating the strength factor of the composite current collector within a certain range, the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the polymer base film can be significantly improved, wherein the strength factor is regulated within the range, and the tensile strength of the composite current collector is R0 is the tensile strength of the polymer base film. In addition, by regulating the strength factor, the composite current collector also has good peel strength.

[0015] If the strength factor is too small or no metal-embedded layer is provided, the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film is not good, and the peel strength of the composite current collector is also not good. The strength factor should not be too large, because the advantage of the composite current collector in terms of lightness and thinness is one of the main reasons for replacing the traditional metal foil (such as electrolytic copper foil), and if the strength factor is too large, it will result in the thickness D of the metal layer being too large, thereby resulting in the composite current collector no longer having the advantages of lightness and thinness, and the manufacturing cost is high, which is no longer suitable for replacing the traditional metal foil.

[0016] In the present application, the strength factor of the composite current collector may be 0.3, 0.33, 0.37, 0.40, 0.47, 0.50, 0.56, 0.6, 0.7, 0.78, 0.80, 0.86, 0.90, 1.00, 1.07, 1.10, 1.15, 1.17, or 1.2.

[0017] Preferably, the strength factor of the composite current collector is

[0018] More preferably, the strength factor of the composite current collector For

[0019] Further preferably, the strength factor of the composite current collector is For

[0020] Optionally, the thickness of the metal layer is: 0.5 μm≤D≤1.5 μm.

[0021] Preferably, the thickness of the metal layer is: 1 μm≤D≤1.5 μm.

[0022] Optionally, the thickness of the polymer base film layer is: 2 μm≤D0≤8 μm.

[0023] Preferably, the thickness of the polymer base film layer is: 3 μm≤D0≤5 μm.

[0024] More preferably, the thickness of the polymer base film layer is: 3 μm≤D0≤3.5 μm.

[0025] Optionally, the thickness of the metal embedded layer is: 0.1 μm≤d≤D0 / 2 μm. Wherein, "D0 / 2" refers to the value obtained by dividing the thickness of the polymer base film layer D0 by 2.

[0026] Preferably, the thickness of the metal embedded layer is: 0.1 μm≤d≤1.5 μm.

[0027] More preferably, the thickness of the metal embedded layer is: 0.5 μm≤d≤1.5 μm.

[0028] Optionally, the polymer material of the polymer base film layer is at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate or polypropylene.

[0029] Optionally, the material of the metal layer is at least one of copper, copper alloy, nickel, nickel alloy, silver or silver alloy.

[0030] Optionally, the metal in the metal embedded layer is at least one of copper, copper alloy, nickel, nickel alloy, silver or silver alloy.

[0031] Optionally, the number of the metal layer is two, which are respectively arranged on the two surfaces of the polymer base film layer.

[0032] Preferably, the porosity of the polymer base film of the polymer base film layer is 5-70%.

[0033] More preferably, the porosity of the polymer base film of the polymer base film layer is 20-50%.

[0034] Further preferably, the porosity of the polymer base film is 30-50%.

[0035] Optionally, the average pore size of the pores of the polymer base film of the polymer base film layer is 20-100 nm.

[0036] Optionally, the tensile strength of the polymer base film of the polymer base film layer is 200-380 MPa.

[0037] Preferably, the tensile strength of the polymer base film of the polymer base film layer is 210-360 MPa.

[0038] More preferably, the tensile strength of the polymer base film of the polymer base film layer is 320-360 MPa.

[0039] A preparation method of a composite current collector, comprising the following steps:

[0040] S1. performing plasma treatment, sensitization treatment and activation treatment on a polymer base film to obtain a pretreated polymer base film;

[0041] S2. performing chemical plating on the pretreated polymer base film to form a metal embedding layer in the polymer base film to obtain a metalized base film;

[0042] S3. performing electroplating on the metalized base film to form a metal layer, thereby obtaining the composite current collector.

[0043] The polymer base film and the metal layer are combined by the chemical plating + electroplating of the preparation method of the present application, which not only forms a metal embedding layer in the polymer base film, but also does not damage the polymer base film, thereby significantly improving the tensile strength of the composite current collector relative to the tensile strength of the base film, and improving the peel strength of the composite current collector. In addition, the preparation method of the present application is not only suitable for the polymer base film with the commonly used materials of PP and PET, but also suitable for the polymer base film with the material of PE.

[0044] Optionally, the porosity of the polymer base film in step S1 is 5-70%; specifically, 5%, 10%, 20%, 30%, 40%, 50%, 60% or 70%.

[0045] Preferably, the porosity of the polymer base film in step S1 is 20-50%.

[0046] More preferably, the porosity of the polymer base film in step S1 is 30-50%.

[0047] Optionally, the average pore size of the pores of the polymer base film in step S1 is 20-100 nm.

[0048] Optionally, the power of the plasma treatment in step S1 is 50-200 W, and the time is 60-300 s.

[0049] Optionally, the sensitization solution used in the sensitization treatment in step S1 comprises the following components with the following concentrations: SnCl2 5-25 g / L, HCl 10-35 ml / L.

[0050] Optionally, the time of the sensitization treatment in step S1 is 0.5-3 min.

[0051] Optionally, after the sensitization treatment in step S1, a cleaning step is further included before the activation treatment.

[0052] Optionally, the cleaning agent used in the cleaning step is water.

[0053] Optionally, the time of the cleaning step is 5-15 s.

[0054] Optionally, the activation solution used in the activation treatment in step S1 comprises the following components with the following concentrations: PdCl2 0.5-2 g / L, HCl 8-20 ml / L.

[0055] Optionally, the time of the activation treatment in step S1 is 0.5-3 min.

[0056] Optionally, the activation treatment in step S1 further comprises a drying step.

[0057] Optionally, the number of electroless plating in step S2 can be one or two.

[0058] Optionally, when the number of electroless plating is one, the electroless plating solution comprises the following components with the following concentrations: copper sulfate 5-10 g / L, disodium EDTA 30-60 g / L, bipyridine 5-20 mg / L, sodium hydroxide 3-8 g / L, formaldehyde 5-10 g / L; and the time of electroless plating is 6-8 min.

[0059] Preferably, when the number of electroless plating is two, the electroless plating comprises a first electroless plating and a second electroless plating in sequence; the electroless plating solution of the first electroless plating comprises the following components with the following concentrations: copper sulfate 5-10 g / L, disodium EDTA 30-60 g / L, bipyridine 5-20 mg / L, sodium hydroxide 3-8 g / L, formaldehyde 5-10 g / L; and the electroless plating solution of the second electroless plating comprises the following components with the following concentrations: copper sulfate 5-15 g / L, disodium EDTA 5-10 g / L, potassium sodium tartrate 20-40 g / L, bipyridine 5-20 mg / L, sodium hydroxide 5-10 g / L, formaldehyde 5-20 g / L.

[0060] Preferably, when the number of electroless plating is two, the electroless plating comprises a first electroless plating and a second electroless plating in sequence; the electroless plating solution of the first electroless plating comprises the following components with the following concentrations: copper sulfate 5-10 g / L, disodium EDTA 30-60 g / L, bipyridine 5-20 mg / L, sodium hydroxide 3-8 g / L, formaldehyde 5-10 g / L; and the electroless plating solution of the second electroless plating comprises the following components with the following concentrations: copper sulfate 5-15 g / L, disodium EDTA 5-10 g / L, potassium sodium tartrate 20-40 g / L, bipyridine 5-20 mg / L, sodium hydroxide 5-10 g / L, formaldehyde 5-20 g / L.

[0061] Compared with the chemical plating with one time, the chemical plating with two times can make the metal embedding layer reach the same thickness in a shorter time through cooperation of the first chemical plating and the second chemical plating, and is more efficient.

[0062] Optionally, the time of the first chemical plating is 1-3 min; and the time of the second chemical plating is 1-2 min.

[0063] Optionally, the electroplating in step S2 is multi-stage electroplating.

[0064] Optionally, the electroplating in step S2 further comprises a step of corrosion inhibition treatment.

[0065] Optionally, the corrosion inhibition treatment is in the form of immersion in a corrosion inhibition solution.

[0066] Optionally, the immersion in the corrosion inhibition solution is for 2-5 min at a temperature of 30-70 DEG C.

[0067] Optionally, the corrosion inhibition solution for the immersion in the corrosion inhibition solution comprises the following components with the following concentrations: BTA 5-20 mg / L, and ammonium molybdate 2-30 mg / L.

[0068] The application also relates to the composite current collector in the preparation of a lithium ion battery negative electrode.

[0069] Compared with the prior art, the application has the following beneficial effects:

[0070] (1) The strength factor of the composite current collector is regulated within a certain range, so that the tensile strength of the composite current collector is obviously improved relative to the tensile strength of the base film; meanwhile, the regulation of the strength factor also makes the composite current collector have good peeling strength. In addition, the composite current collector also has low square resistance.

[0071] (2) The polymer base film and the metal layer are compounded through the chemical plating+electroplating mode of the preparation method, so that not only the metal embedding layer can be formed in the polymer base film, but also the mode of forming the metal embedding layer will not damage the polymer base film, thereby obviously improving the tensile strength of the composite current collector relative to the tensile strength of the base film, and improving the peeling strength of the composite current collector. In addition, the preparation method is not only suitable for the polymer base film with the commonly used materials of PP and PET, but also suitable for the polymer base film with the material of PE. BRIEF DESCRIPTION OF DRAWINGS

[0072] Figure 1 It is a structure schematic view of the composite current collector of Example 2.

[0073] Figure 2 It is an SEM view of the surface of the composite current collector of Example 2.

[0074] Figure 3 SEM image of a cross section of the composite current collector of Example 2. DETAILED DESCRIPTION

[0075] In order to more clearly, completely describe the technical solutions of the present application, the present application is further described in detail below through specific examples. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application. Various changes can be made within the scope of the present application.

[0076] Example 1

[0077] The present example provides a composite current collector, which comprises a polymer base film layer 1 and a metal layer 2 arranged on both surfaces of the polymer base film layer 1, and the polymer base film layer 1 comprises a metal embedding layer 11 in contact with the metal layer. The thickness D0 of the polymer base film layer 1 is 3 μm, the thickness D of the metal layer 2 is 1 μm, and the thickness d of the metal embedding layer 11 is 1.5 μm. The polymer material of the polymer base film layer 1 is polyethylene, the material of the metal layer 2 is copper, and the polymer material in the metal embedding layer 11 is polyethylene and the metal in the metal embedding layer 11 is copper. The porosity of the polymer base film of the polymer base film layer 1 is 30%.

[0078] The preparation method of the composite current collector of the present example comprises the following steps:

[0079] 1) A PE film with a porosity of 30%, an average diameter of pores of 80 nm, and a thickness of 3 μm is selected as a polymer base film. The base film is first subjected to low-pressure plasma treatment, then is immersed in a prepared sensitization solution for 2 min, is then washed in deionized water for 10 s, is then immersed in an activation solution for 2 min, and is then dried at 60 °C for 2 min to obtain a pretreated polymer base film. The plasma treatment conditions are as follows: a power of 50 W, a time of 80 s, and an argon gas as the plasma treatment gas. The composition of the sensitization solution is as follows: SnCl2 20 g / L, HCl 30 ml / L, and deionized water as the solvent. The composition of the activation solution is as follows: PdCl2 1.0 g / L, HCl 10 ml / L, and deionized water as the solvent.

[0080] 2) immerse the pretreated polymer base film into the first electroless plating solution for 3 minutes, continuously stirring the first electroless plating solution during the immersion, then immerse the film into the second electroless plating solution for 1 minute, continuously stirring the second electroless plating solution during the immersion, and take out the film to obtain the metalized film. The first electroless plating solution comprises copper sulfate 6 g / L, disodium EDTA 50 g / L, bipyridine 15 mg / L, sodium hydroxide 6 g / L, formaldehyde 5 g / L, and deionized water as the solvent; the second electroless plating solution comprises copper sulfate 8 g / L, disodium EDTA 5 g / L, potassium sodium tartrate 40 g / L, bipyridine 10 mg / L, sodium hydroxide 8 g / L, formaldehyde 15 g / L, and deionized water as the solvent.

[0081] 3) carry out multi-stage electroplating on the metalized film to form a metal layer with a thickness of 1 μm on each side of the film; then immerse the film into the corrosion inhibitor solution at 45 °C for 2 minutes, clean the film with deionized water, and dry the film with hot air at 60 °C to obtain the composite current collector. The corrosion inhibitor solution comprises BTA 10 mg / L and ammonium molybdate 15 mg / L, and deionized water as the solvent.

[0082] Examples 2-5

[0083] The composite current collectors of Examples 2-5 differ from the composite current collector of Example 1 in that the thickness d of the metal embedding layer 11 is different, as shown in Table 1. The structure of Example 2 is shown in Fig. 2. Figure 1

[0084] The preparation method of the composite current collectors of Examples 2-5 differs from the preparation method of the composite current collector of Example 1 in that the immersion time of the first electroless plating solution and the second electroless plating solution in Step 2) is different. The immersion time of the first electroless plating solution in Examples 2-5 is 2.5 minutes, 2 minutes, 1.6 minutes, and 1.0 minute, respectively, and the immersion time of the second electroless plating solution in Examples 2-5 is 1.25 minutes, 1.5 minutes, 1.7 minutes, and 2.0 minute, respectively.

[0085] Examples 6-7

[0086] The composite current collectors of Examples 6-7 differ from the composite current collector of Example 3 in that the porosity of the polymer base film of the polymer base film layer 1 is different, as shown in Table 1.

[0087] The preparation method of the composite current collectors of Examples 6-7 differs from the preparation method of the composite current collector of Example 3 in that the porosity of the PE film selected in Step 1) is 20% and 50%, respectively.

[0088] Examples 8-9

[0089] ​The composite current collectors of Examples 8-9 differ from the composite current collector of Example 1 in that the thickness D of the metal layer 2 is different, as shown in Table 1.

[0090] The method for preparing the composite current collector of Example 8 differs from the method for preparing the composite current collector of Example 1 in that in the third step, the thickness of the metal layer formed on each side of the metallized film is controlled to be 1.2 μm by controlling the time of the multi-stage electroplating.

[0091] The method for preparing the composite current collector of Example 9 differs from the method for preparing the composite current collector of Example 1 in that in the third step, the thickness of the metal layer formed on each side of the metallized film is controlled to be 1.5 μm by controlling the time of the multi-stage electroplating.

[0092] Examples 10-11

[0093] The composite current collectors of Examples 10-11 differ from the composite current collector of Example 1 in that the thickness D0 of the polymer base film layer 1 is different, as shown in Table 1.

[0094] The method for preparing the composite current collectors of Examples 10-11 differs from the method for preparing the composite current collector of Example 1 in that in the first step, the thickness of the PE film used is 3.5 μm and 4.5 μm, respectively.

[0095] Comparative Example 1

[0096] The composite current collector of Comparative Example 1 differs from the composite current collector of Example 1 in that the thickness D0 of the polymer base film layer 1 and the thickness d of the metal-embedded layer 11 are different, as shown in Table 1.

[0097] The method for preparing the composite current collector of Comparative Example 1 differs from the method for preparing the composite current collector of Example 1 in that in the first step, the thickness of the PE film used is 4.5 μm; and in the second step, the first electroless plating solution is not used, and only the second electroless plating solution is used, and the soaking time is 2.5 min.

[0098] Comparative Example 2

[0099] The composite current collector of Comparative Example 2 differs from the composite current collector of Example 1 in that the thickness of the polymer base film layer 1, the thickness D of the metal layer 2, and the thickness d of the metal-embedded layer 11 are different, as shown in Table 1.

[0100] The preparation method of the composite current collector in Comparative Example 2 differs from that in Example 1 in that: in step 1), the thickness of the PE film used is 2.5 μm; in step 2), the chemical plating process involves immersing the pretreated base film in the first chemical plating solution for 3 minutes, and then immersing it in the second chemical plating solution for 1 minute; in step 3), by controlling the time of the multi-stage electroplating, the thickness of the metal layer formed on both sides is 2 μm.

[0101] Comparative Example 3

[0102] The composite current collector of Comparative Example 3 differs from the composite current collector of Example 1 in that: no metal embedding layer 11 is provided, that is, the thickness d of the metal embedding layer 11 is 0, and the porosity of the polymer base film of the polymer base film layer 1 is different, as shown in Table 1.

[0103] The preparation method of the composite current collector in Comparative Example 3 differs from that in Example 1 in that: in step 1), the porosity of the selected PE membrane is 0.

[0104] Sample characterization and performance testing

[0105] 1. Cross-section and surface morphology

[0106] Scanning electron microscopy (SEM) was used for imaging. The surface and cross-sectional morphology were tested after gold sputtering. Gold sputtering was used to improve the conductivity of the sample to obtain clear images. The gold-plated film formed by sputtering is approximately 10–30 nm thick and does not affect the morphology observation. Furthermore, imaging was conducted under low voltage conditions to avoid burning the base film material. The surface and cross-section of the composite current collector in Example 2 are shown below. Figure 2 and Figure 3 As shown. From Figure 2 It is evident that the chemical plating + electroplating method of this invention, used to form the metal embedding layer and the metal layer, does not damage the polymer base film. This results in a significantly higher tensile strength of the obtained composite current collector compared to the polymer base film. From Figure 3 It is known that by using the chemical plating method of the present invention, a metal embedded layer can be formed on the base film. The formation of the metal embedded layer is beneficial to the tensile strength of the obtained composite current collector being significantly higher than that of the polymer base film.

[0107] 2. Thickness

[0108] SEM cross-sectional analysis allows for direct measurement of the thickness of the polymer base film (D0), the metal embedding layer (d), and the metal layer (D), as detailed in Table 1. The thickness d of the metal embedding layer refers to the shortest distance from the deepest copper layer embedded in the polymer base film to the surface of the polymer base film.

[0109] 3. Tensile strength

[0110] Tensile strength test was performed on the polymer base film and the composite current collector of each example and comparative example. The test was performed on an island electronic universal testing machine AGS-X-10kN type tension tester, the sample length was 150mm*15mm, the test interval was 8mm, and the tensile speed was 50mm / min.

[0111] 4. Peeling strength

[0112] Peeling strength of the composite current collector of each example and comparative example was tested. The prepared flat composite current collector sample was cut into a sample with a width of 24mm and a length of 300mm, one end of the cut sample was folded with the adhesive surface facing out to form a folded layer about 12mm long; the other end of the sample was pasted to one end of a steel plate, and then rolled twice with an adhesive tape rolling machine at a speed of 600mm / min, and then placed in an electronic peeling tester, with a test speed of 250mm / min and a sample width of 24mm; the force value during peeling was recorded automatically by the equipment, and the peeling strength of the sample was reported accordingly.

[0113] 5. Square resistance test

[0114] Square resistance of the composite current collector of each example and comparative example was tested. A four-probe tester was used, and the correction coefficient was set according to the test requirements; after selecting the measurement category, the instrument was switched to the measurement mode; the sample was placed on the test table, and the probe was pressed to make good contact with the sample, and the test result was read.

[0115] The results of sample characterization and performance test are shown in Table 1 below.

[0116] Table 1

[0117]

[0118] In Table 1, R0 is the tensile strength of the polymer base film, with the unit of MPa. The units of D0, D and d are all μm. is the strength factor, dimensionless unit. R m is the tensile strength of the composite current collector, with the unit of MPa. X is the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film, and the calculation process is X = ((R m -R0) / R0)*100%. The unit of peeling strength is N / m. The unit of square resistance is mΩ / □.

[0119] From Table 1, it can be seen that:

[0120] The degree of improvement of the tensile strength of the composite current collector of Examples 1-11 relative to the tensile strength of the base film is all above 9.7%, which indicates that the strength factor Within a certain range, the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the polymer base film can be significantly improved; at the same time, the peel strength of the composite current collector of Examples 1-11 is all above 550 N / m, indicating that the strength factor of the composite current collector is controlled, and the composite current collector also has good peel strength. In addition, by controlling the strength factor of the composite current collector Within a certain range, the composite current collector also has low square resistance (all below 17 mΩ / □).

[0121] As can be seen from Comparative Examples 1-5, as d increases, the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film gradually increases, the tensile strength and peel strength of the composite current collector gradually increase, and the square resistance gradually decreases. Among them, the square resistance of Example 1 decreases obviously relative to Examples 2-5, which is caused by the mutual connection of the metal embedded layers on both sides of the base film of Example 1.

[0122] As can be seen from Comparative Example 3 and Examples 6-7, as the porosity of the base film increases, the strength factor first increases and then decreases, and the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film also first increases and then decreases.

[0123] As can be seen from Comparative Example 1, 8 and 9, as the thickness of the metal layer increases, the strength factor gradually increases, the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film gradually increases, the tensile strength of the composite current collector increases, and the square resistance performance decreases.

[0124] As can be seen from Comparative Example 1, 10 and 11, as the thickness of the base film (polymer base film layer) increases, the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film gradually decreases, and the tensile strength and square resistance of the composite current collector gradually increase.

[0125] The strength factor of Comparative Example 1 is not controlled within a suitable range, the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film is not good, and the peel strength of the composite current collector is insufficient.

[0126] The strength factor of Comparative Example 2 is too large, although the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film is large, but the thickness of the metal layer is too large at this time, which leads to the composite current collector no longer having the advantage of being light and thin, and the manufacturing cost is high, which is no longer suitable to replace the traditional metal foil (such as electrolytic copper foil).

[0127] The composite current collector of Comparative Example 3 does not have a metal embedded layer, the degree of improvement of the tensile strength of the composite current collector relative to the tensile strength of the base film is small; and its peel strength is obviously insufficient, which does not meet the requirements in the industry.

[0128] Obviously, the above embodiments of the present application are merely exemplary but not intended to limit the embodiments of the present application. Based on the above description, any other variations or changes can be made by those skilled in the art without departing from the spirit and principles of the present application. It is not necessary to list all the embodiments here. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall fall within the scope of the claims of the present application.

Claims

1. A composite current collector, characterized in that, It includes a polymer base film layer and a metal layer disposed on at least one surface of the polymer base film layer, wherein the polymer base film layer includes a metal embedded layer in contact with the metal layer; The intensity factor of the composite current collector for The Where D is the thickness of the metal layer, D0 is the thickness of the polymer base film layer, and d is the thickness of the metal intercalation layer; The thickness of the metal layer is: 0.5μm≤D≤1.5μm; The thickness of the polymer-based film layer is: 2μm≤D0≤8μm; The thickness of the metal embedding layer is: 0.1μm≤d≤D0 / 2μm; The thickness d of the metal embedding layer refers to the shortest distance from the deepest copper embedded in the polymer base film to the surface of the polymer base film layer.

2. The composite current collector according to claim 1, characterized in that, The intensity factor of the composite current collector for 3. The composite current collector according to claim 2, characterized in that, The intensity factor of the composite current collector for 4. The composite current collector according to claim 3, characterized in that, The intensity factor of the composite current collector for 5. The composite current collector according to claim 1, characterized in that, The thickness of the metal layer is: 1.0μm≤D≤1.5μm.

6. The composite current collector according to claim 1, characterized in that, The thickness of the polymer-based film layer is: 3μm≤D0≤3.5μm.

7. The composite current collector according to claim 1, characterized in that, The thickness of the metal embedding layer is: 0.1μm≤d≤1.5μm.

8. The composite current collector according to claim 1, characterized in that, The polymer material of the polymer base film layer is at least one of polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polybutylene terephthalate, or polypropylene.

9. The composite current collector according to claim 1, characterized in that, The material of the metal layer is at least one of copper, copper alloy, nickel, nickel alloy, silver, or silver alloy.

10. The composite current collector according to claim 1, characterized in that, The metal in the metal embedding layer is at least one of copper, copper alloy, nickel, nickel alloy, silver, or silver alloy.

11. The composite current collector according to claim 1, characterized in that, The metal layer consists of two layers, which are respectively disposed on the two surfaces of the polymer base film layer.

12. The composite current collector according to claim 1, characterized in that, The polymer base film of the polymer base film layer has a porosity of 5-70%.

13. The composite current collector according to claim 12, characterized in that, The polymer base film of the polymer base film layer has a porosity of 20-50%.

14. The composite current collector according to claim 1, characterized in that, The average pore size of the polymer base film in the polymer base film layer is 20–100 nm.

15. A method for preparing the composite current collector according to any one of claims 1 to 14, characterized in that, Includes the following steps: S1. The polymer base film is subjected to plasma treatment, sensitization treatment and activation treatment to obtain a pretreated polymer base film; S2. Perform chemical plating on the pretreated polymer base film to form a metal intercalation layer in the polymer base film, thereby obtaining a metallized base film; S3. Electroplating is performed on the metallized base film to form a metal layer, thus obtaining the composite current collector.

16. The preparation method according to claim 15, characterized in that, The plasma treatment in step S1 has a power of 50-200W and a time of 60-300s.

17. The preparation method according to claim 15, characterized in that, The sensitization solution used in step S1 includes the following components at the following concentrations: SnCl2 5-25 g / L and HCl 10-35 ml / L.

18. The preparation method according to claim 15 or 17, characterized in that, The sensitization treatment time in step S1 is 0.5 to 3 minutes.

19. The preparation method according to claim 15, characterized in that, The activation solution used in step S1 includes the following components at the following concentrations: PdCl2 0.5-2 g / L and HCl 8-20 ml / L.

20. The preparation method according to claim 15 or 19, characterized in that, The activation treatment time in step S1 is 0.5 to 3 minutes.

21. The preparation method according to claim 15, characterized in that, The chemical plating in step S2 is performed once or twice.

22. The preparation method according to claim 21, characterized in that, When the electroless plating is performed once, the electroless plating solution contains the following components at the following concentrations: copper sulfate 5-10 g / L, disodium EDTA 30-60 g / L, bipyridine 5-20 mg / L, sodium hydroxide 3-8 g / L, and formaldehyde 5-10 g / L; the electroless plating time is 6-8 min.

23. The preparation method according to claim 21, characterized in that, When the electroless plating is performed twice, the electroless plating sequentially includes a first electroless plating and a second electroless plating; the electroless plating solution for the first electroless plating includes the following components at the following concentrations: copper sulfate 5-10 g / L, disodium EDTA 30-60 g / L, bipyridine 5-20 mg / L, sodium hydroxide 3-8 g / L, and formaldehyde 5-10 g / L; the electroless plating solution for the second electroless plating includes the following components at the following concentrations: copper sulfate 5-15 g / L, disodium EDTA 5-10 g / L, potassium sodium tartrate 20-40 g / L, bipyridine 5-20 mg / L, sodium hydroxide 5-10 g / L, and formaldehyde 5-20 g / L.

24. The preparation method according to claim 23, characterized in that, The first electroless plating time is 1 to 3 minutes; the second electroless plating time is 1 to 2 minutes.

25. The preparation method according to claim 15, characterized in that, The electroplating process also includes a corrosion inhibition treatment step.

26. The application of the composite current collector according to any one of claims 1 to 14 in the preparation of a lithium-ion battery anode.

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