A method for preparing a high-stability, high-conductivity, self-healing conductive current collector

Abstract

The present invention relates to the field of electrochemical technology, and in particular to a method for preparing a high-stability, high-conductivity, self-healing conductive current collector, comprising the following steps: (1) synthesizing carbon nanotubes wrapped with p-type poly(3,4-ethylenedioxythiophene), (2) synthesizing carbon nanotubes wrapped with n-type poly(3,4-ethylenedioxythiophene), and (3) preparing a conductive current collector. The surface coating of the current collector has good conductivity and strong adhesion, can partially buffer the influence of external damage, and ensure basic conductive stability.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a method for preparing a high-stability, high-conductivity, self-healing conductive current collector. Background Art

[0002] The rapid development of electric vehicles, smart grids, and mobile devices has driven the rapid growth of lithium batteries, placing higher demands on them in terms of energy density and cycle stability. Recently, with the advent of silicon-carbon anodes, anodes with higher lithium storage capacity are gradually entering the industrialization stage and are already being used in a wide range of products. These applications also place higher demands on current collectors, particularly in terms of stability and conductivity.

[0003] Much work has been done to improve the stability of the current collector. Patent CN 112103512 A uses a deposition method to form a coating on the current collector surface, ensuring 99% battery capacity after 300 cycles. However, the high processing temperature and high raw material costs pose significant cost pressures for large-scale use. Patent CN112259743 A uses materials such as polyacrylonitrile and polymethyl methacrylate to impart toughness and mechanical strength to the current collector, thereby improving the battery's coulombic efficiency and cycle stability. However, the binder partially increases the current collector's resistance, and once the material is damaged, it cannot be restored. Patent CN 106928788 A uses polytetrafluoroethylene as a binder to bond glass fiber, carbon fiber, and graphite powder to improve the impact resistance and conductivity of the coating film. However, the binder still enhances the electron-blocking ability of the coating layer itself, so further improvement is needed.

[0004] The main binders in the existing technology are water-based binders such as polyvinylidene fluoride or styrene-butadiene rubber, which have excellent bonding properties. However, when the outer material expands or dislocates, the negative electrode will peel off and lose its function. At the same time, the addition of the binder will partially increase the resistance of the material and reduce the material's electron transmission capacity. At the same time, due to the properties of the material itself, once the coating layer is damaged, it will fail, and the battery performance of the material will not be restored. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to propose a method for preparing a high-stability, high-conductivity, self-healing conductive current collector. The surface coating of the current collector has good conductivity and strong adhesion, can partially buffer the impact of external damage, and ensure basic conductive stability.

[0006] Based on the above objectives, the present invention provides a method for preparing a high-stability, high-conductivity, self-healing conductive current collector, comprising the following steps:

[0007] S1: adding carbon nanotubes and ferric chloride to a mixed solution of anhydrous ethanol and deionized water, ultrasonically treating for 15-30 minutes, and drying to obtain carbon nanotubes adsorbing iron ions;

[0008] S2: adding 3,4-ethylenedioxythiophene and carbon nanotubes adsorbed with iron ions to anhydrous ethanol, ultrasonically treating for 5-10 minutes, then reacting at 60-70°C for 24-36 hours, washing, and drying to obtain p-type poly(3,4-ethylenedioxythiophene)-coated carbon nanotubes;

[0009] S3: adding polyethyleneimine to anhydrous ethanol, and then adding p-type poly (3,4-ethylenedioxythiophene) wrapped carbon nanotubes, ultrasonically treating for 5-10 minutes, and then drying at 60-70 ° C for 4-6 hours to obtain n-type poly (3,4-ethylenedioxythiophene) wrapped carbon nanotubes;

[0010] S4: mixing p-type poly (3,4-ethylenedioxythiophene) wrapped carbon nanotubes, n-type poly (3,4-ethylenedioxythiophene) wrapped carbon nanotubes, polyetherthiourea, a binder, a conductive agent and a solvent to obtain a binding solution;

[0011] S5: The bonding solution is coated on the current collector, dried at 70-80°C for 2-4 hours, and then vacuum activated at 150-170°C for 3-5 hours to form a cross-linked network to obtain a highly stable, high-conductivity, self-healing conductive current collector.

[0012] Preferably, the diameter of the carbon nanotubes in step S1 is 2-5 nm, and the length is 5-10 μm.

[0013] Preferably, in step S1, the mass ratio of carbon nanotubes, ferric chloride, ethanol and deionized water is 10-15:3-5:50-80:100-160.

[0014] Preferably, in step S2, the mass ratio of 3,4-ethylenedioxythiophene, carbon nanotubes adsorbing iron ions, and anhydrous ethanol is 10-25:15-40:100-200.

[0015] Preferably, in step S3, the mass ratio of polyethyleneimine, anhydrous ethanol and carbon nanotubes wrapped with p-type poly(3,4-ethylenedioxythiophene) is 1-4:50-200:5-20; and the concentration of polyethyleneimine is ≥98%.

[0016] Preferably, in step S4, the mass ratio of the p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, the n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, the polyetherthiourea, the binder, the conductive agent and the solvent is 10-18:5-9:0.3-0.6:0.1-0.3:5-10:10-20.

[0017] Preferably, the binder in step S4 includes one or more of polyvinylidene fluoride, polyacrylate, sodium carboxymethyl cellulose, styrene-butadiene rubber, epoxy resin, silicone resin, polyphthalimide resin, phenolic resin, polyurethane, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and acrylonitrile multipolymer.

[0018] Preferably, the conductive agent in step S4 includes one or more of graphene, carbon nanotubes, carbon fibers, activated carbon, graphite sheets, graphite particles, conductive carbon black, acetylene black and mesocarbon microbeads.

[0019] Preferably, the solvent in step S4 includes an organic solvent and / or an inorganic solvent, wherein the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide, ethanol, and isopropanol, and the inorganic solvent includes one or more of deionized water, distilled water, and purified water.

[0020] The present invention further provides a high-stability, high-conductivity, self-healing conductive current collector, which is prepared according to the above-mentioned method for preparing a high-stability, high-conductivity, self-healing conductive current collector.

[0021] Beneficial effects of the present invention:

[0022] (1) The coating on the surface of the current collector prepared by the present invention has better conductivity and can alleviate the inhibition of electron transport of the material by using traditional binders.

[0023] (2) The polyetherthiourea in the present invention forms a cross-linked network under thermal cross-linking, wherein the carbon nanotubes wrapped by p-type poly(3,4-ethylenedioxythiophene) are in a continuous state due to aggregation, while the carbon nanotubes wrapped by n-type poly(3,4-ethylenedioxythiophene) are in a dispersed state in the cross-linked network due to hydrogen bonding with the amino groups in thiourea. The combination of the continuous state and the dispersed state promotes the transmission of electrons and improves the conductivity.

[0024] (3) The cross-linked network constructed by polyetherthiourea can play a good buffering role when internal stress occurs in the matrix, and the cross-linking of the thiourea group itself has self-healing ability, thereby giving the surface coating of the current collector self-healing ability. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments.

[0026] Example 1

[0027] A highly stable, highly conductive, self-healing conductive current collector is prepared by the following specific preparation process:

[0028] S1: 10 g of carbon nanotubes with a diameter of 2.5 nm and a length of 8 μm and 3 g of ferric chloride were added to a mixed solution of 50 g of anhydrous ethanol and 100 g of deionized water, ultrasonicated for 15 min, and dried to obtain carbon nanotubes adsorbing iron ions;

[0029] S2: 10 g of 3,4-ethylenedioxythiophene and 15 g of carbon nanotubes adsorbed with iron ions were added to 100 g of anhydrous ethanol, and ultrasonicated for 5 min. Then, the mixture was reacted at 60°C for 24 h, washed, and dried to obtain p-type poly(3,4-ethylenedioxythiophene)-coated carbon nanotubes.

[0030] S3: 1 g of polyethyleneimine was added to 50 g of anhydrous ethanol, followed by the addition of 5 g of p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes. The mixture was ultrasonicated for 5 min and then dried at 60°C for 4 h to obtain n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes.

[0031] S4: 10 g of p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 5 g of n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 0.3 g of polyetherthiourea, 0.1 g of polyvinylidene fluoride, 5 g of graphene, and 10 g of N,N-dimethylformamide were mixed to obtain a bonding solution;

[0032] S5: The bonding solution is coated on the current collector, dried at 70°C for 2 hours, and then vacuum activated at 150°C for 3 hours to form a cross-linked network to obtain a highly stable, high-conductivity, self-healing conductive current collector.

[0033] Example 2

[0034] A highly stable, highly conductive, self-healing conductive current collector is prepared by the following specific preparation process:

[0035] S1: 12.5 g of carbon nanotubes with a diameter of 2.5 nm and a length of 8 μm and 4 g of ferric chloride were added to a mixed solution of 65 g of anhydrous ethanol and 130 g of deionized water, ultrasonicated for 22 min, and dried to obtain carbon nanotubes adsorbing iron ions;

[0036] S2: 17.5 g of 3,4-ethylenedioxythiophene and 27.5 g of carbon nanotubes adsorbed with iron ions were added to 150 g of anhydrous ethanol, and the mixture was ultrasonically treated for 7 min. Then, the mixture was reacted at 65° C. for 30 h, washed, and dried to obtain p-type poly(3,4-ethylenedioxythiophene)-coated carbon nanotubes.

[0037] S3: 2.5 g of polyethyleneimine was added to 125 g of anhydrous ethanol, followed by the addition of 12.5 g of p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes. The mixture was ultrasonically treated for 7 min and then dried at 65° C. for 5 h to obtain n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes.

[0038] S4: 14 g of p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 7 g of n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 0.45 g of polyetherthiourea, 0.2 g of polyvinylidene fluoride, 7.5 g of graphene, and 15 g of N,N-dimethylformamide were mixed to obtain a bonding solution;

[0039] S5: The bonding solution is coated on the current collector, dried at 75°C for 3 hours, and then vacuum activated at 160°C for 4 hours to form a cross-linked network to obtain a highly stable, high-conductivity, self-healing conductive current collector.

[0040] Example 3

[0041] A highly stable, highly conductive, self-healing conductive current collector is prepared by the following specific preparation process:

[0042] S1: 15 g of carbon nanotubes with a diameter of 2.5 nm and a length of 8 μm and 5 g of ferric chloride were added to a mixed solution of 80 g of anhydrous ethanol and 160 g of deionized water, ultrasonicated for 30 min, and dried to obtain carbon nanotubes adsorbing iron ions;

[0043] S2: 25 g of 3,4-ethylenedioxythiophene and 40 g of carbon nanotubes adsorbed with iron ions were added to 200 g of anhydrous ethanol, and ultrasonicated for 10 min. Then, the mixture was reacted at 70°C for 36 h, washed, and dried to obtain p-type poly(3,4-ethylenedioxythiophene)-coated carbon nanotubes.

[0044] S3: 4 g of polyethyleneimine was added to 200 g of anhydrous ethanol, followed by the addition of 20 g of p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes. The mixture was ultrasonically treated for 10 min and then dried at 70°C for 6 h to obtain n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes.

[0045] S4: 18 g of p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 9 g of n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 0.6 g of polyetherthiourea, 0.3 g of polyvinylidene fluoride, 10 g of graphene, and 20 g of N,N-dimethylformamide were mixed to obtain a bonding solution;

[0046] S5: The bonding solution is coated on the current collector, dried at 80°C for 4 hours, and then vacuum activated at 170°C for 5 hours to form a cross-linked network to obtain a highly stable, high-conductivity, self-healing conductive current collector.

[0047] Comparative Example 1

[0048] A conductive current collector is obtained by the following specific preparation process:

[0049] S1: Same as Example 2;

[0050] S2: Same as Example 2;

[0051] S3: 21 g of p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 0.45 g of polyetherthiourea, 0.2 g of polyvinylidene fluoride, 7.5 g of graphene, and 15 g of N,N-dimethylformamide were mixed to obtain a bonding solution;

[0052] S4: The bonding solution is coated on the current collector, dried at 75°C for 3 hours, and then vacuum activated at 160°C for 4 hours to form a cross-linked network to obtain a highly stable, high-conductivity, self-healing conductive current collector.

[0053] Comparative Example 2

[0054] A conductive current collector is obtained by the following specific preparation process:

[0055] S1: Same as Example 2;

[0056] S2: Same as Example 2;

[0057] S3: Same as Example 2;

[0058] S4: 21 g of n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 0.45 g of polyetherthiourea, 0.2 g of polyvinylidene fluoride, 7.5 g of graphene, and 15 g of N,N-dimethylformamide were mixed to obtain a bonding solution;

[0059] S5: Same as Example 2.

[0060] Comparative Example 3

[0061] A conductive current collector is obtained by the following specific preparation process:

[0062] S1: 0.45 g of polyetherthiourea, 0.2 g of polyvinylidene fluoride, 28.5 g of graphene, and 15 g of N,N-dimethylformamide were mixed to obtain a bonding solution;

[0063] S2: The bonding solution is coated on the current collector, dried at 75°C for 3 hours, and then vacuum activated at 160°C for 4 hours to obtain a high-stability, high-conductivity, self-healing conductive current collector.

[0064] Comparative Example 4

[0065] A conductive current collector is obtained by the following specific preparation process:

[0066] S1: Same as Example 2;

[0067] S2: Same as Example 2;

[0068] S3: Same as Example 2;

[0069] S4: 14 g of p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 7 g of n-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, 0.65 g of polyvinylidene fluoride, 7.5 g of graphene, and 15 g of N,N-dimethylformamide were mixed to obtain a bonding solution;

[0070] S5: The bonding solution is coated on the current collector, dried at 75°C for 3 hours, and then vacuum dried at 160°C for 4 hours to form a cross-linked network to obtain a high-stability, high-conductivity, self-healing conductive current collector.

[0071] Assembly of button half-cell: using commercial Li4Ti5O 12 (LTO) is the active material, acetylene black is the conductive agent, and polyvinylidene fluoride is the binder. They are dispersed in N-methylpyrrolidone at a mass ratio of 8:1:1 to prepare a slurry. The slurry is then evenly coated on the surface of the conductive current collector prepared in Examples 1-3 and Comparative Examples 1-4. The coated electrode sheet is then vacuum-dried at 120°C for 12 hours. After drying, the electrode sheet is punched into a disc with a diameter of 12 mm to obtain an LTO electrode. A lithium sheet is used as the counter electrode, LTO is used as the working electrode, Celgard2400 is used as the separator, and the electrolyte is LiPF6 (organic solvent: EC+DMC+DEC, volume ratio 1:1:1). Half-cells are assembled in a glove box, and 45 μL of electrolyte is used for each button half-cell.

[0072] Performance Tests of Examples 1-3 and Comparative Examples 1-4

[0073] Cycling performance: The battery was charged and discharged using a BlueDian system with the following parameters set: During the constant current charge and discharge test, the discharge voltage was cut off at 1.0V, the charge voltage was cut off at 2.5V, and the battery was charged and discharged at a constant current of 1C for 500 cycles. The test results are shown in Table 1.

[0074] Peel strength: The current collectors prepared in the above embodiments and comparative examples were cut into test samples with a size of 90x120 mm. The cut current collectors were affixed to the middle of a thin steel plate with double-sided tape, with the end faces flush. The thin steel plate should be wiped clean with dust-free paper in advance to remove stains and dust. One end of the sample was bent 180° in the opposite direction and fixed on a tensile probe. The sample was peeled 180° at a constant rate of 5 cm / min to test the peel strength of the sample. The test results are shown in Table 1.

[0075] Table 1 Performance test results of Examples 1-3 and Comparative Examples 1-4

[0076]

[0077] Data analysis: From the performance test results of Examples 1-3, it can be seen that the conductive current collector prepared by the present invention has high stability and high conductivity, and from Example 2 and Comparative Example 4, it can be seen that the polyether thiourea added by the present invention has a great influence on the stability of the battery, mainly because the polyether thiourea itself has self-repairing ability and can self-repair during the battery cycle.

[0078] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples. Within the scope of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0079] The present invention is intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a high-stability, high-conductivity, self-healing conductive current collector, characterized in that: The following steps are involved: S1: adding carbon nanotubes and ferric chloride to a mixed solution of anhydrous ethanol and deionized water, ultrasonically treating for 15-30 minutes, and drying to obtain carbon nanotubes adsorbing iron ions; S2: adding 3,4-ethylenedioxythiophene and carbon nanotubes adsorbed with iron ions to anhydrous ethanol, ultrasonically treating for 5-10 minutes, then reacting at 60-70°C for 24-36 hours, washing, and drying to obtain p-type poly(3,4-ethylenedioxythiophene)-wrapped carbon nanotubes; S3: adding polyethyleneimine to anhydrous ethanol, and then adding p-type poly (3,4-ethylenedioxythiophene)-wrapped carbon nanotubes, ultrasonically treating for 5-10 minutes, and then drying at 60-70°C for 4-6 hours to obtain n-type poly (3,4-ethylenedioxythiophene)-wrapped carbon nanotubes; S4: mixing p-type poly (3,4-ethylenedioxythiophene) wrapped carbon nanotubes, n-type poly (3,4-ethylenedioxythiophene) wrapped carbon nanotubes, polyetherthiourea, a binder, a conductive agent and a solvent to obtain a binding solution; S5: The bonding solution is coated on the current collector, dried at 70-80°C for 2-4 hours, and then vacuum activated at 150-170°C for 3-5 hours to form a cross-linked network to obtain a highly stable, high-conductivity, self-healing conductive current collector.

2. The method for preparing a high-stability, high-conductivity, self-healing conductive current collector according to claim 1, characterized in that: In step S1, the diameter of the carbon nanotubes is 2-5 nm and the length is 5-10 μm.

3. The method for preparing a high-stability, high-conductivity, self-healing conductive current collector according to claim 1, characterized in that: In step S1, the mass ratio of carbon nanotubes, ferric chloride, anhydrous ethanol and deionized water is 10-15:3-5:50-80:100-160.

4. The method for preparing a high-stability, high-conductivity, self-healing conductive current collector according to claim 1, characterized in that: In step S2, the mass ratio of 3,4-ethylenedioxythiophene, carbon nanotubes adsorbing iron ions, and anhydrous ethanol is 10-25:15-40:100-200.

5. The method for preparing a high-stability, high-conductivity, self-healing conductive current collector according to claim 1, characterized in that: In step S3, the mass ratio of polyethyleneimine, anhydrous ethanol, and carbon nanotubes wrapped with p-type poly(3,4-ethylenedioxythiophene) is 1-4:50-200:5-20.

6. The method for preparing a high-stability, high-conductivity, self-healing conductive current collector according to claim 1, characterized in that: In step S4, the mass ratio of the p-type poly (3,4-ethylenedioxythiophene) wrapped carbon nanotubes, the n-type poly (3,4-ethylenedioxythiophene) wrapped carbon nanotubes, polyetherthiourea, binder, conductive agent and solvent is 10-18:5-9:0.3-0.6:0.1-0.3:5-10:10-20.

7. The method for preparing a high-stability, high-conductivity, self-healing conductive current collector according to claim 1, characterized in that: The binder in step S4 includes one or more of polyvinylidene fluoride, polyacrylate, sodium carboxymethyl cellulose, styrene-butadiene rubber, epoxy resin, silicone resin, polyimide resin, phenolic resin, polyurethane, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, and acrylonitrile multipolymer.

8. The method for preparing a high-stability, high-conductivity, self-healing conductive current collector according to claim 1, characterized in that: The conductive agent in step S4 includes one or more of graphene, carbon nanotubes, carbon fibers, activated carbon, graphite sheets, graphite particles, conductive carbon black, acetylene black and mesocarbon microbeads.

9. The method for preparing a high-stability, high-conductivity, self-healing conductive current collector according to claim 1, characterized in that: The solvent in step S4 includes an organic solvent and / or an inorganic solvent, wherein the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide, ethanol, and isopropanol, and the inorganic solvent includes one or more of deionized water, distilled water, and purified water.

10. A high stability, high conductivity, self-healing conductive current collector, characterized in that: The high-stability, high-conductivity, self-healing conductive current collector is prepared according to the preparation method of the high-stability, high-conductivity, self-healing conductive current collector according to any one of claims 1-9.

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