Conductive adhesive, method of preparation and use thereof

Abstract

The application provides a conductive adhesive, a preparation method and application thereof. The conductive adhesive is a composite conductive polymer with a three-dimensional interpenetrating network structure formed by blending of a polyaniline-modified carbon nanotube composite material and polyacrylate; the polyaniline-modified carbon nanotube composite material is a composite material with polyaniline in-situ grown on the surface of modified carbon nanotubes, and the modified carbon nanotubes are hydroxylated modified carbon nanotubes. The polyaniline composite material with in-situ growth of the modified carbon nanotubes in the conductive adhesive has excellent conductivity, and the polyacrylate has good adhesion, and the conductive polymer with a three-dimensional interpenetrating network structure formed by blending of the two has the functions of not only more tightly bonding the positive active material together and enhancing the electronic conductivity of the positive active material, but also enhancing the adhesion and conductivity between the positive active material and the current collector and reducing the ohmic resistance of the pole piece.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a conductive binder, its preparation method, and its application. Background Technology

[0002] Lithium iron phosphate (LiFePO4) materials possess excellent safety and cycle performance due to their unique and stable olivine structure, and also show potential in high energy density and power density. Therefore, LiFePO4 is a promising electrode material and is widely used in the field of electric vehicles where high safety performance is required. However, the structure of lithium iron phosphate materials also has significant limitations, such as low electronic conductivity and low diffusion coefficient, resulting in high impedance, which restricts the application of lithium iron phosphate. To improve its electronic conductivity, various schemes have been proposed. The two main methods are: one is to coat the crystal surface with a good electronic conductor layer, such as carbon coating, to increase the electron transport path and thus improve the electrochemical performance of LiFePO4; the other method is to construct a composite conductive network using highly conductive materials such as carbon fibers, carbon nanotubes (CNTs), and graphene. The modified material has higher electron transport performance.

[0003] However, these methods all modify the material by improving its structure, thereby improving its performance. However, to improve the rate performance and cycle performance of LiFePO4 batteries, it is not only necessary to improve the performance of the material itself, but also to address the poor conductivity of LiFePO4 material by improving the structure and composition of each part of the electrode.

[0004] Traditional electrode materials consist of active materials, binders, and conductive agents. The commonly used binder system for positive electrode fabrication is the polyvinylidene fluoride (PVDF) / NMP system. PVDF, as an insulating polymer, constitutes a larger proportion of the formulation, leading to a decrease in battery capacity. PVDF can swell in non-aqueous liquid electrolytes, weakening the adhesion of the electrode material to the current collector and thus increasing the contact resistance between electrode materials. At elevated temperatures, it can react with lithium metal and lithium carbide (Li₂O₃). x C 6) Reactions can lead to safety accidents. Adding excessive conductive agents to increase conductivity not only increases the difficulty of dispersing the conductive agents in the solvent, resulting in uneven dispersion and increased complexity in subsequent processing, but can also negatively impact battery performance in severe cases. Therefore, reducing the amount of conductive agents and binders is a simple and effective way to improve battery capacity.

[0005] The application patent CN113078317A discloses a water-based conductive binder for lithium ion batteries, which comprises a basic binder, a functional binder, an intrinsic conductive polymer, modified carbon nanotubes, deionized water and an auxiliary agent. The basic binder comprises one or more of water-based styrene butadiene copolymer, sodium carboxymethyl cellulose, water-based polyacrylic acid, water-based polyimide, polyvinyl alcohol, water-based polyvinylidene fluoride, water-based polyurethane, water-based polyester, water-based polyether, polyacrylonitrile type water-based binder and polyvinylpyrrolidone binder. The functional binder is a polyacrylic acid binder emulsion containing a polyhydroxy structure. The intrinsic conductive polymer is at least one of polyacetylene, polythiophene, polypyrrole, polyaniline, poly-p-phenylene vinylene and derivatives of the above-mentioned substances. However, the above-mentioned conductive binder is a water-based conductive binder, which is more suitable for the preparation of negative electrode sheets and cannot be applied to mainstream lithium iron phosphate positive electrode materials. SUMMARY

[0006] In view of the deficiencies and defects of the prior art, the present application aims to provide a conductive binder, a preparation method and applications thereof. The present application prepares a composite material with polyaniline grown in situ on the surface of modified carbon nanotubes by chemical oxidation polymerization of aniline in an acidic solution and in the presence of an oxidizing agent. Then, a polyacrylate solution is prepared by free radical polymerization. Finally, a composite conductive polymer with a three-dimensional interpenetrating network structure is obtained by blending the polyaniline-modified carbon nanotube composite material and the polyacrylate solution. The polyaniline composite material grown in situ on the modified carbon nanotubes in the conductive binder has excellent conductivity, while the polyacrylate has good adhesion. The conductive polymer with a three-dimensional interpenetrating network structure formed by blending the two has excellent adhesion to the positive electrode active material and can enhance the electronic conductivity of the positive electrode active material, as well as the adhesion and conductivity between the positive electrode active material and the current collector, thereby reducing the ohmic resistance of the electrode sheet.

[0007] To achieve the above-mentioned purpose, the first aspect of the present application provides a conductive binder, which adopts the following technical solution:

[0008] A conductive binder, which is a composite conductive polymer with a three-dimensional interpenetrating network structure formed by blending a polyaniline-modified carbon nanotube composite material and a polyacrylate. The polyaniline-modified carbon nanotube composite material is a composite material with polyaniline grown in situ on the surface of modified carbon nanotubes, and the modified carbon nanotubes are hydroxylated modified carbon nanotubes.

[0009] The polyacrylate has good adhesion, and the composite conductive polymer formed by blending the two has a three-dimensional network structure, which not only retains the conductivity of the polyaniline-modified carbon nanotube composite material and the adhesion of the polyacrylate, but also enables the positive active material to be more closely connected together and enhances the conductivity, and also enhances the adhesion and conductivity between the positive active material and the current collector, thereby reducing the ohmic resistance of the pole piece; compared with the traditional non-conductive binder, the conductive binder can replace the conductive agent and the binder at the same time, plays a role in adhesion, increases the conductivity of the electrode material, reduces the use of the conductive agent, and can increase the proportion of the active material in the electrode and increase the battery capacity; in summary, the conductive binder can replace the conductive agent and the binder widely used in the lithium ion battery lithium iron phosphate positive material system, and also plays a role in improving the battery capacity and the battery performance.

[0010] In the conductive binder, as a preferred embodiment, the polyaniline-modified carbon nanotube composite material is prepared by using aniline and modified carbon nanotubes as raw materials, and the aniline is subjected to chemical oxidation polymerization on the surface of the modified carbon nanotubes by using an acidic solution and an oxidizing agent to obtain a composite material in which polyaniline grows in situ on the surface of the modified carbon nanotubes.

[0011] In the present application, the carbon nanotubes are modified by hydroxylation to obtain hydroxyl-modified carbon nanotubes, so that a large number of hydroxyl groups exist on the surface of the carbon nanotubes, providing reaction sites for the growth of aniline, and then enabling polyaniline to grow in situ on the surface of the carbon nanotubes, forming polyaniline with more uniform distribution, thereby making the consistency of the final positive paste better.

[0012] In the conductive binder, as a preferred embodiment, the weight average molecular weight of the polyacrylate is 3000-18000 (such as 5000, 6000, 8000, 10000, 12000, 15000);

[0013] Preferably, the polyacrylate is obtained by homopolymerization or copolymerization of one or more monomers selected from acrylic ester monomers and carboxyl group-containing ethylenically unsaturated copolymerizable monomers; the acrylic ester monomers are selected from one or more of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and hydroxyethyl acrylate; the carboxyl group-containing ethylenically unsaturated copolymerizable monomers are selected from one or more of acrylic acid, methacrylic acid, and maleic acid.

[0014] The second aspect of the present application provides a preparation method of the conductive adhesive, comprising:

[0015] S1, aniline and modified carbon nanotubes are added to an acidic solution, followed by adding an oxidizing agent to perform a chemical oxidation polymerization reaction, and then performing washing treatment, filtration treatment and vacuum drying treatment to prepare a polyaniline-modified carbon nanotube composite material;

[0016] S2, one or more monomers of an acrylate monomer and a carboxyl group-containing ethylenically unsaturated copolymerizable monomer are subjected to a free radical polymerization reaction to obtain a polyacrylate solution;

[0017] S3, the polyaniline-modified carbon nanotube composite material is added to the polyacrylate solution for mixing treatment, followed by suction filtration treatment, washing treatment and vacuum drying treatment to prepare the conductive adhesive.

[0018] In the preparation method of the conductive adhesive, as a preferred embodiment, in step S1, the mass ratio of the aniline to the modified carbon nanotubes is 1-2:1 (such as 1.1:1, 1.2:1, 1.4:1, 1.5:1, 1.7:1, 1.8:1, 1.9:1);

[0019] Preferably, the acidic solution is selected from one of hydrochloric acid, sulfuric acid, phosphoric acid and citric acid;

[0020] Preferably, the molar ratio of the aniline to H + in the acidic solution is 11-13:1 (such as 11.2:1, 11.5:1, 11.8:1, 12:1, 12.2:1, 12.5:1, 12.8:1);

[0021] Preferably, the oxidizing agent is ammonium persulfate, and the molar ratio of the oxidizing agent to the aniline is 1:1-5 (such as 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 5:1);

[0022] Preferably, the temperature of the chemical oxidation polymerization reaction is 20-30℃ (such as 22℃, 24℃, 25℃, 27℃, 29℃) (room temperature), and the reaction time is 12-24h (such as 13h, 15h, 18h, 20h, 22h, 23h).

[0023] In the preparation method of the conductive adhesive, as a preferred embodiment, in step S1, the modified carbon nanotubes are prepared by sequentially performing modification treatment and washing centrifugal treatment on carbon nanotubes added to a mixed acid solution;

[0024] Preferably, the carbon nanotube is a multi-walled carbon nanotube, with a diameter of 20-50 nm (such as 25 nm, 30 nm, 35 nm, 40 nm, 45 nm) and a tube length of 100-200 μm (such as 120 μm, 140 μm, 150 μm, 180 μm, 190 μm);

[0025] Preferably, the mixed acid is a mixed solution of H2SO4 and HNO3 in a volume ratio of 3:1; the ratio of the mass g of the carbon nanotube to the volume mL of the mixed acid is 1:100-500 (such as 1:150, 1:200, 1:250, 1:300, 1:350, 1:400, 1:450);

[0026] Preferably, the temperature of the modification treatment is 100-140℃ (such as 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃) and the time is 6-12h (such as 7h, 8h, 9h, 10h, 11h).

[0027] In the above method for preparing the conductive adhesive, as a preferred embodiment, in step S2, the radical polymerization reaction is a solution polymerization reaction.

[0028] Preferably, the monomer mixture is formed by mixing one or more of an acrylate monomer, a carboxyl group-containing ethylenically unsaturated copolymerizable monomer, and an initiator, and then performing a solution polymerization reaction in an organic solvent, followed by filtration to obtain a polyacrylate solution.

[0029] Preferably, the mass ratio of the monomer mixture to the initiator is 50-200:1 (such as 60:1, 80:1, 100:1, 150:1, 170:1, 190:1).

[0030] Preferably, the organic solvent is selected from one of methyl, N-methylpyrrolidone; and the mass ratio of the monomer mixture to the organic solvent is 1:5-10 (such as 1:6, 1:7, 1:8, 1:9).

[0031] Preferably, the temperature of the solution polymerization reaction is 75-85℃ (such as 76℃, 78℃, 80℃, 82℃, 84℃) and the time is 4-7h (such as 4.5h, 5h, 5.5h, 6h, 6.5h).

[0032] In the preparation method of the conductive adhesive, as a preferred embodiment, in step S3, the mass percentage of the polyaniline-modified carbon nanotube composite is 10%-50% (such as 15%, 20%, 25%, 30%, 35%, 40%, 45%), and the mass percentage of the polyacrylate solution is 50%-90% (such as 55%, 60%, 65%, 70%, 75%, 80%, 85%) relative to the total mass of the polyaniline-modified carbon nanotube composite and the polyacrylate solution.

[0033] The conductive adhesive in the application is a composite conductive polymer with a three-dimensional interpenetrating network structure formed by blending a polyaniline-modified carbon nanotube composite and a polyacrylate, wherein the polyacrylate mainly functions as an adhesive; if the added mass of the polyacrylate solution is too small, the adhesion between the positive electrode sheet and the current collector prepared is insufficient, resulting in a low peeling strength; if the added mass of the polyacrylate solution is too large, the conductivity of the positive electrode sheet is reduced, and thus the conductive adhesive cannot play a conductive role.

[0034] The third aspect of the application provides a positive electrode, which comprises a current collector and an active material layer attached to at least one surface of the current collector, and the raw material of the active material layer comprises a positive electrode active material and the conductive adhesive described above or prepared by the preparation method described above, and the raw material of the active material layer comprises, in terms of mass percentage, the positive electrode active material 95%-97% (such as 95.2%, 95.5%, 95.8%, 96%, 96.2%, 96.5%, 96.8%) and the conductive adhesive 3%-5% (such as 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%).

[0035] The conductive adhesive in the application plays a conductive role on one hand and an adhesive role on the other hand; if the added mass of the conductive adhesive is too large, the excessive conductive adhesive will occupy a larger proportion of the positive electrode active material, and thus the capacity of the battery is reduced; if the added mass of the conductive adhesive is too small, the positive electrode active material cannot be attached to the current collector, and phenomena such as powder falling, low peeling strength, etc. occur.

[0036] In the positive electrode described above, as a preferred embodiment, the positive electrode active material is a lithium iron phosphate material; preferably, the current collector is an aluminum foil.

[0037] The fourth aspect of the application provides an application of the positive electrode described above in a lithium ion battery.

[0038] Compared with the prior art, the application has the following effective effects:

[0039] Compared with the traditional non-conductive binder, the conductive binder of the present application can replace the conductive agent and the binder at the same time, increase the conductivity of the electrode material while playing a binding role, reduce the use of the conductive agent, increase the proportion of the active substance in the electrode, and increase the battery capacity; at the same time, the addition of the conductive binder can reduce the contact resistance between the active substances and the current collector, thereby improving the electrochemical performance of the battery, and has great advantages in the preparation of the electrode material. The conductive binder of the present application can replace the conductive agent and the binder widely used in the lithium ion battery lithium iron phosphate positive electrode material system at present, and at the same time, play a role in improving the battery capacity and the battery performance. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A schematic diagram of the preparation method of the polyaniline-modified carbon nanotube composite material in the present application;

[0041] Figure 2 A schematic diagram of the preparation method of the conductive binder in the present application;

[0042] Figure 3 The positive electrode is assembled into a button cell after the conductive binder prepared in Example 1 and the conductive binder of Comparative Example 3 are mixed with the positive electrode active material, respectively, and the charge-discharge curve at 0.1C rate is shown. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the embodiments of the present application. It should be understood by those skilled in the art that the embodiments are only to help understand the present application, and should not be regarded as a specific limitation on the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0044] The embodiments of the present application are implemented on the premise of the technical scheme of the present application, and detailed implementation modes and processes are given, but the protection scope of the present application is not limited to the following embodiments, and the process parameters not specified in the following embodiments are usually according to the conventional conditions.

[0045] The endpoints of the ranges and any values disclosed in the present application are not limited to the precise values stated. The ranges or values should be interpreted as approximately between the stated values. For ranges, the endpoints are included between each respective range; the endpoints are included in the respective range and each respective range is a new range; and the ranges of values are not limited to the precise values stated.

[0046] In the present application, unless otherwise specified and / or described, all the numerical values of the component amount involved throughout are "parts by weight". The process parameters not specified in the following examples are generally in accordance with the conventional conditions. The raw materials described in the following examples can be obtained from the public commercial channels. The carbon nanotubes used in the examples and comparative examples of the present application are multi-walled carbon nanotubes with a diameter of 20-50 nm and a tube length of 100-200 μm. The initiator in the preparation method of the polyacrylate solution of the present application is not specifically limited, and can be the common initiator in the free radical polymerization reaction in the art, as long as it can initiate the free radical polymerization reaction of one or more monomers of the acrylate monomer and the carboxyl group-containing ethylenically unsaturated copolymerizable monomer to obtain the polyacrylate solution.

[0047] The present application will be further described in detail below in conjunction with specific examples.

[0048] Example 1 A preparation method of a conductive adhesive, comprising:

[0049] (1) Preparation of polyaniline-modified carbon nanotube composite material: i. 0.5 g of carbon nanotubes was added to 100 mL of a mixed solution of H2SO4 and HNO3 with a volume ratio of 3:1, and modified at 100°C for 12 h, then centrifuged, washed and adjusted to pH 6 with deionized water to obtain modified carbon nanotubes; ii. 20 ml of hydrochloric acid (1 mol / L) was mixed with 450 mg of modified carbon nanotubes to obtain a uniform mixture, 30 mL of hydrochloric acid (1 mol / L), 1.6 mmol of ammonium persulfate and 6.4 mmol of aniline were added thereto, and a chemical oxidation polymerization reaction was carried out at room temperature (20-30°C) for 24 h, then the obtained precipitate was washed, filtered and vacuum dried at room temperature to prepare a polyaniline-modified carbon nanotube composite material Figure 1 Schematic diagram of the preparation method of the polyaniline-modified carbon nanotube composite material in the present application);

[0050] (2) Preparation of polyacrylate solution: 80 g of toluene solution was added to a three-necked flask equipped with a condenser, a dropping funnel and a thermometer, and stirred to warm up to 75°C, 0.05 g of ammonium persulfate (initiator APS) and a monomer mixture were added, wherein the monomer mixture was composed of 4 g of methyl methacrylate (MMA), 5 g of butyl acrylate (BA) and 1 g of acrylic acid (AA). After the addition of the monomer mixture was completed, the temperature was raised to 80°C for 5 hours to carry out solution polymerization, and then the polyacrylate solution (PAA) was obtained after cooling and filtering.

[0051] (3) Preparation of the conductive binder: the polyacrylate solution and the polyaniline-modified carbon nanotube composite material are mixed in a mass ratio of 70%:30% to form a stable solution, and then the conductive polymer, i.e. the conductive binder, is obtained after extraction, washing, and vacuum drying. Figure 2 The preparation method of the conductive binder in the present application is shown in the schematic diagram.

[0052] Example 2

[0053] Example 2 differs from Example 1 in that the polyacrylate solution and the polyaniline-modified carbon nanotube composite material are mixed in a mass ratio of 90%:10%, and the rest is the same as Example 1.

[0054] Example 3

[0055] Example 3 differs from Example 1 in that the polyacrylate solution and the polyaniline-modified carbon nanotube composite material are mixed in a mass ratio of 80%:20%, and the rest is the same as Example 1.

[0056] Example 4

[0057] Example 4 differs from Example 1 in that the polyacrylate solution and the polyaniline-modified carbon nanotube composite material are mixed in a mass ratio of 60%:40%, and the rest is the same as Example 1.

[0058] Example 5

[0059] Example 5 differs from Example 1 in that the polyacrylate solution and the polyaniline-modified carbon nanotube composite material are mixed in a mass ratio of 50%:50%, and the rest is the same as Example 1.

[0060] Comparative Example 1

[0061] The conductive binder of Comparative Example 1 is a polyaniline-modified carbon nanotube composite material, which differs from Example 1 in that no polyacrylate solution is added for mixing, and the preparation of the polyaniline-modified carbon nanotube composite material is the same as Example 1.

[0062] Comparative Example 2

[0063] The conductive binder of Comparative Example 2 is a polyacrylate solution, which differs from Example 1 in that no polyaniline-modified carbon nanotube is added for mixing, and the preparation of the polyacrylate solution is the same as Example 1.

[0064] Comparative Example 3

[0065] The conductive binder of Comparative Example 3 is PVDF and SP in a mass ratio of 2:1.

[0066] Comparative Example 4

[0067] (1) Preparation of modified carbon nanotubes: 0.5 g of carbon nanotubes was added to 100 mL of a mixed solution of H2SO4 and HNO3 with a volume ratio of 3:1, and modified at 100°C for 12 h, and then adjusted to pH 6 by centrifugation, washing with deionized water, to obtain modified carbon nanotubes;

[0068] (2) Preparation of polyaniline: 50 ml of hydrochloric acid (1 mol / L), 1.6 mmol of ammonium persulfate, and 6.4 mmol of aniline were mixed at room temperature (20-30°C) for 24 h of chemical oxidation polymerization, and then the obtained precipitate was washed, filtered, and vacuum dried at room temperature to obtain polyaniline;

[0069] (3) Preparation of polyacrylate solution: 80 g of toluene was added to a three-necked flask equipped with a condenser, a dropping funnel, and a thermometer, and stirred to 75°C, and then 0.05 g of ammonium persulfate (initiator APS) solution and a monomer mixture were added, wherein the monomer mixture was composed of 4 g of methyl methacrylate (MMA), 5 g of butyl acrylate (BA), and 1 g of acrylic acid (AA). After the addition of the monomer mixture, the temperature was raised to 80°C and the solution polymerization was carried out for 5 hours, and then the polyacrylate solution (PAA) was obtained after cooling and filtration.

[0070] (4) Preparation of conductive adhesive: polyacrylate solution, polyaniline, and modified carbon nanotube composite were mixed in a mass ratio of 70%:20%:10% to form a stable solution, and then subjected to suction filtration, washing, and vacuum drying to obtain a conductive polymer, i.e. conductive adhesive.

[0071] Comparative Example 5

[0072] Comparative Example 5 and Example 1 differ in that the polyacrylate solution and the polyaniline-modified carbon nanotube composite were mixed in a mass ratio of 95%:5%, and the rest was the same as Example 1.

[0073] Performance Test

[0074] The positive active material (LiFePO4), the conductive binder in Examples 1-5 and Comparative Examples 1-5 were added into N-methyl pyrrolidone solvent (NMP) at a mass ratio of 97:3, and mechanically stirred for 3 h to form a stable slurry, and then the slurry was uniformly coated on a metal aluminum foil with a coating thickness of 150 μm, and then vacuum dried at 80°C for 2 h to obtain a positive electrode sheet, and the dried positive electrode sheet was cut into a circular sheet with a diameter of 14 mm. A button cell was prepared in a glove box with the cut electrode sheet as the positive electrode, a metal lithium sheet as the negative electrode, a porous polypropylene film (PP) as the separator, and a 1 mol / L lithium hexafluorophosphate (LiPF6) solution as the electrolyte, and the solvent was a mixture of ethylene carbonate (EC) and ethyl carbonate (DMC) at a volume ratio of 1:1, according to a certain assembly process. After completion, the electrolyte was fully infiltrated with the electrode material at room temperature for 2 h. A series of electrochemical tests were performed on the prepared battery using a Neware battery test cabinet, and the test conditions were as follows: at room temperature (25±0.5°C), the charge and discharge were performed at 0.1C / 0.1C in the voltage range of 2-3.75V. The test conditions for the sheet resistance were as follows: the resistance of the prepared positive electrode sheet was measured using a two-probe tester; the test conditions for the sheet peeling strength were as follows: the positive electrode sheet was cut into a sample with a size of 25*200 mm, and a tensile test was performed at a 180° angle on a tensile testing machine at room temperature, and the specific test results are shown in Tables 1 and 2. Figure 3 The conductive binder prepared in Example 1 of the present application and the conductive binder of Comparative Example 3 were mixed with the positive active material to form a positive electrode, and the button cell was assembled, and the charge and discharge curves at 0.1C rate were obtained.

[0075] Table 1

[0076]

[0077] Table 2

[0078]

[0079]

[0080] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application is within the scope of the claims of the present application.

Claims

1. An electrically conductive binder for lithium ion batteries, characterized by, The conductive adhesive is a composite conductive polymer with a three-dimensional interpenetrating network structure formed by blending a polyaniline-modified carbon nanotube composite material and a polyacrylate; the polyaniline-modified carbon nanotube composite material is a composite material in which polyaniline is grown in situ on the surface of modified carbon nanotubes, and the modified carbon nanotubes are hydroxylated modified carbon nanotubes; The preparation method of the conductive adhesive comprises: S1, adding aniline and modified carbon nanotubes into an acidic solution, then adding an oxidizing agent to perform a chemical oxidation polymerization reaction, and then performing washing treatment, filtration treatment, and vacuum drying treatment to prepare a polyaniline-modified carbon nanotube composite material; S2, performing a free radical polymerization reaction on one or more monomers of an acrylate monomer and a carboxyl group-containing ethylenically unsaturated copolymerizable monomer to obtain a polyacrylate solution; S3, adding the polyaniline-modified carbon nanotube composite material into the polyacrylate solution for mixing treatment, and then performing suction filtration treatment, washing treatment, and vacuum drying treatment to prepare the conductive adhesive.

2. The electrically conductive adhesive of claim 1, wherein, The weight average molecular weight of the polyacrylate is 3000-18000; And / or, the polyacrylate is obtained by homopolymerization or copolymerization of one or more monomers of an acrylate monomer and a carboxyl group-containing ethylenically unsaturated copolymerizable monomer; the acrylate monomer is selected from one or more of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and hydroxyethyl acrylate; and the carboxyl group-containing ethylenically unsaturated copolymerizable monomer is selected from one or more of acrylic acid, methacrylic acid, and maleic acid.

3. The electrically conductive adhesive of claim 1, wherein, In step S1, the mass ratio of the aniline to the modified carbon nanotubes is 1-2:1; And / or, the acidic solution is selected from one of hydrochloric acid, sulfuric acid, phosphoric acid, and citric acid; and / or the molar ratio of said aniline to H + of said acid solution is 11-13:1; And / or, the oxidizing agent is ammonium persulfate, and the molar ratio of the oxidizing agent to the aniline is 1:1-5; And / or, the temperature of the chemical oxidation polymerization reaction is 20-30°C, and the reaction time is 12-24h.

4. The electrically conductive adhesive of claim 1, wherein, In step S1, the modified carbon nanotubes are prepared by sequentially performing modification treatment and washing and centrifugal treatment on carbon nanotubes added into a mixed acid solution to obtain modified carbon nanotubes; And / or, the carbon nanotubes are multi-walled carbon nanotubes with a diameter of 20-50nm and a tube length of 100-200μm; And / or, the mixed acid is a mixed solution of H2SO4 and HNO3 with a volume ratio of 3:1; and the ratio of the mass g of the carbon nanotubes to the volume mL of the mixed acid is 1:100-500; And / or, the temperature of the modification treatment is 100-140°C, and the time is 6-12h.

5. The electrically conductive adhesive of claim 1, wherein, In step S2, the free radical polymerization reaction is a solution polymerization reaction; And / or, the polyacrylate solution is obtained by adding a monomer mixture formed by mixing one or more monomers of an acrylate monomer and a carboxyl group-containing ethylenically unsaturated copolymerizable monomer and an initiator into an organic solvent to perform a solution polymerization reaction, and then performing filtration treatment; And / or, the mass ratio of the monomer mixture to the initiator is 50-200:

1. and / or, the organic solvent is selected from one of methyl, N-methyl pyrrolidone; the mass ratio of the monomer mixture to the organic solvent is 1:5-10; and / or, the temperature of the solution polymerization reaction is 75-85℃, and the time is 4-7h.

6. The electrically conductive adhesive of claim 1, wherein, In step S3, the polyaniline-modified carbon nanotube composite material is 10%-50% and the polyacrylate solution is 50%-90% relative to the total mass of the polyaniline-modified carbon nanotube composite material and the polyacrylate solution.

7. A positive electrode, characterized by comprising: The positive electrode comprises: a current collector and an active material layer attached to at least one surface of the current collector, the raw material of the active material layer comprises a positive electrode active material and the conductive binder of any one of claims 1-6, and the raw material of the active material layer comprises, in mass percentage, the positive electrode active material 95%-97% and the conductive binder 3%-5%.

8. The positive electrode according to claim 7, characterized by The positive electrode active material is a lithium iron phosphate material.

9. The positive electrode according to claim 7, characterized by The current collector is an aluminum foil.

10. Use of the positive electrode according to any one of claims 7-9 in a lithium ion battery.

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